427 results on '"E2F4"'
Search Results
252. Infrequent frameshift mutations of polynucleotide repeats in multiple primary cancers affecting the esophagus and other organs
- Author
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Satoshi Nishizuka, Koki Otsuka, Kiichi Aoki, Kazuyoshi Saito, Ken Sakata, Nobuhiro Sato, Yasushi Suzuki, Takeshi Iwaya, Chihaya Maesawa, Satoshi Ogasawara, Kaoru Ishida, Yusuke Kimura, Kenichiro Ikeda, Keisuke Koeda, and Gen Tamura
- Subjects
Cancer Research ,Esophageal Neoplasms ,DNA Mutational Analysis ,Loss of Heterozygosity ,Protein Serine-Threonine Kinases ,Biology ,Frameshift mutation ,Neoplasms, Multiple Primary ,Stomach Neoplasms ,Proto-Oncogene Proteins ,Genetics ,medicine ,Humans ,Thyroid Neoplasms ,Frameshift Mutation ,E2F4 ,Gene ,Repetitive Sequences, Nucleic Acid ,Reverse Transcriptase Polymerase Chain Reaction ,Receptor, Transforming Growth Factor-beta Type II ,Cancer ,DNA, Neoplasm ,medicine.disease ,Kidney Neoplasms ,DNA-Binding Proteins ,MSH6 ,MutS Homolog 2 Protein ,MSH3 ,MSH2 ,Colonic Neoplasms ,MutS Homolog 3 Protein ,Microsatellite ,Multidrug Resistance-Associated Proteins ,Receptors, Transforming Growth Factor beta ,Microsatellite Repeats - Abstract
Frequent frameshift mutations of simple nucleotide repeats in the protein-encoding regions, as well as replication errors (RERs) at microsatellite loci, have recently been demonstrated in gastrointestinal tumors. These genetic instabilities have been considered indicative of an increased risk of accumulating mutations in cancer-associated genes and of developing multiple cancers. We studied frameshift (or insertion/deletion) mutations of simple nucleotide repeats in five genes (TGFbeta type II receptor [TGFbetaRII], E2F4, MSH2, MSH3, and MSH6) in 23 tumors from 12 patients who had synchronous cancers of the esophagus and other organs. Genetic instability at four microsatellite loci, as well as mutations in the TP53, APC, and KRAS2 genes, were also studied. No frameshift mutations were observed in the TGFbetaRII, MSH3, and MSH6 genes. RER and a deletion mutation of BAT26 in MSH2 were present in one (1/23; 4%) gastric cancer. This tumor also carried a deletion mutation in the serine (AGC) repeat of the E2F4 gene. Mutation screening of the TP53, APC, and KRAS2 genes revealed that the synchronous cancers did not carry the same mutations. Our results suggested that genetic instability, such as insertion/deletion mutations in simple nucleotide repeats, is not significantly associated with the development of multiple primary cancers of the esophagus and other organs, and that these synchronous cancers developed independently according to their different environmental factors.
- Published
- 1998
253. TREX1 suppression imparts cancer-stem-cell-like characteristics to CD133 - osteosarcoma cells through the activation of E2F4 signaling.
- Author
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Feng J, Lan R, Cai G, and Lin J
- Abstract
There is ongoing debate whether cancer stem cells (CSCs) could arise from the transformation of non-CSCs under specific conditions. In the present study, the role of the three prime repair exonuclease 1 (TREX1) in regulating CSC generation form human osteosarcoma cells was investigated. High, intermediate and low levels of TREX1 expression were respectively observed in low-grade, high-grade and metastatic human osteosarcoma samples, while the opposite tendency was observed for E2F4, a transcription factor associated with G2 arrest. Luciferase assay proved that TREX1 had a negative impact on the activity of E2F4 promoter. TREX1 was highly expressed in CD133
- HOS cells (non-CSC osteosarcoma cells) compared to CD133+ ones; whereas TREX1 knockdown endowed the CD133- non-CSCs with CSC-like characteristics in vitro relying on E2F4 activation, as demonstrated by enlarged proportion of the subset expressing CSC markers in flow cytometry analysis, enhanced self-renewal ability in osteosphere formation assay, increased metastasis capacity in migration and invasion assays, together with improved chemoresistance to cisplatin. Furthermore, TREX1 knockdown and subsequent E2F4 activation could promote the tumorigenicity of CD133- non-CSCs in vivo . With respect to underlying mechanisms, it was found that in CD133- HOS cells, TREX1 suppression would allow the activation of β-catenin signaling in the dependence of E2F4, thus possibly leading to the up-regulation of the transcription factor OCT4. These findings suggested that TREX1 was probably a negative regulator of CSC formation and hence worth to be further studied for developing new treatments in cancer therapies targeting CSCs., Competing Interests: None., (IJCEP Copyright © 2019.)- Published
- 2019
254. Unraveling the role of aurora A beyond centrosomes and spindle assembly: implications in muscle differentiation.
- Author
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Dhanasekaran K, Bose A, Rao VJ, Boopathi R, Shankar SR, Rao VK, Swaminathan A, Vasudevan M, Taneja R, and Kundu TK
- Subjects
- Animals, Aurora Kinase A genetics, Cell Cycle, Cells, Cultured, E2F4 Transcription Factor genetics, HEK293 Cells, Humans, Mice, Mitosis, Muscle, Skeletal metabolism, Myoblasts metabolism, Phosphorylation, Aurora Kinase A metabolism, Cell Differentiation, Centrosome metabolism, E2F4 Transcription Factor metabolism, Muscle, Skeletal cytology, Myoblasts cytology, Spindle Apparatus metabolism
- Abstract
Aurora kinases are critical mitotic serine/threonine kinases and are often implicated in tumorigenesis. Recent studies of the interphase functions for aurora kinase (Aurk)A have considerably expanded our understanding of its role beyond mitosis. To identify the unknown targets of AurkA, we used peptide array-based screening and found E2F4 to be a novel substrate. Phosphorylation of E2F4 by AurkA at Ser75 regulates its DNA binding and subcellular localization. Because E2F4 plays an important role in skeletal muscle differentiation, we attempted to gain insight into E2F4 phosphorylation in this context. We observed that a block in E2F4 phosphorylation retained it better within the nucleus and inhibited muscle differentiation. RNA sequencing analysis revealed a perturbation of the gene network involved in the process of muscle differentiation and mitochondrial biogenesis. Collectively, our findings establish a novel role of AurkA in the process of skeletal muscle differentiation.-Dhanasekaran, K., Bose, A., Rao, V. J., Boopathi, R., Shankar, S. R., Rao, V. K., Swaminathan, A., Vasudevan, M., Taneja, R., Kundu, T. K. Unravelling the role of aurora A beyond centrosomes and spindle assembly: implications in muscle differentiation.
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- 2019
- Full Text
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255. Differential activities of E2F family members: Unique functions in regulating transcription
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Angela M. Pierce, Robin Schneider-Broussard, Jennifer L. Philhower, and David G. Johnson
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Genetics ,Cancer Research ,General transcription factor ,Activator (genetics) ,Transcription (biology) ,E2F1 ,Promoter ,biological phenomena, cell phenomena, and immunity ,Biology ,E2F ,Molecular Biology ,E2F4 ,E2F Transcription Factors - Abstract
Several regulators of E2F transcriptional activity, including the retinoblastoma tumor suppressor (Rb) protein, p16Ink4a, cyclin D1, and cyclin-dependent kinase 4, have been shown to be targets for genetic alterations that underlie the development of human cancers. Deregulation of E2F transcription factors as a result of these genetic alterations is believed to contribute to tumor development. This hypothesis is supported by the finding that at least some members of the E2F gene family can contribute to oncogenic transformation when overexpressed. Each E2F family member can dimerize with DP proteins, bind consensus E2F sites, and activate transcription. Several pieces of evidence suggest, however, that the various E2F species have unique functions in regulating transcription. We compared the abilities of E2F1, E2F4, and E2F5 to activate transcription from a variety of gene promoters and found that in all cases E2F1 was the most potent activator, followed by E2F4 and then by E2F5. Construction of chimeric proteins between E2F1 and E2F4 demonstrated that either the carboxy terminus or the amino terminus of E2F1 could make E2F4 a more potent activator. In contrast, neither the carboxy terminus nor the amino terminus of E2F1 could significantly increase the activity of E2F5. We found that, consistent with a role for E2F5 in transcriptional repression, E2F5's binding partner p130, like Rb, could also actively repress transcription when directly bound to a target promoter. Mol. Carcinog. 22:190–198, 1998. © 1998 Wiley-Liss, Inc.
- Published
- 1998
256. Regulation of the cdk inhibitor p21 gene during cell cycle progression is under the control of the transcription factor E2F
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Steven A. Reeves, Antonio Iavarone, and Hirofumi Hiyama
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Cyclin-Dependent Kinase Inhibitor p21 ,Cancer Research ,Cell Cycle Proteins ,E2F4 Transcription Factor ,Biology ,S Phase ,Mice ,Transactivation ,Cyclin-dependent kinase ,Cyclins ,Tumor Cells, Cultured ,Genetics ,Animals ,Humans ,E2F1 ,Enzyme Inhibitors ,Promoter Regions, Genetic ,E2F ,Molecular Biology ,E2F4 ,Binding Sites ,Cell Cycle ,G1 Phase ,Glioma ,Cell cycle ,E2F Transcription Factors ,DNA-Binding Proteins ,Gene Expression Regulation, Neoplastic ,Cancer research ,biology.protein ,Ectopic expression ,biological phenomena, cell phenomena, and immunity ,Carrier Proteins ,Transcription Factor DP1 ,Restriction point ,E2F1 Transcription Factor ,Retinoblastoma-Binding Protein 1 ,Transcription Factors - Abstract
The control of cell cycle progression is orchestrated by an extraordinary diverse and dynamic in function group of proteins. Critical in the progression are the actions of the E2F family of transcription factors which regulate the expression of genes necessary for the G1/S transition and the WAF/CIP/KIP family of cdk inhibitors which can inhibit cell cycle progression. In this report, we have identified E2F binding sites in both the human and mouse p21 promoters that bind E2F protein complexes from nuclear extracts in a cell cycle-dependent manner. In ectopic expression experiments we determined that E2F1, but not E2F4, can strongly transactivate the human p21 gene through these E2F binding sites which are located in the -215/+1 region of the p21 gene. The transactivation of the p21 gene through regulatory elements within the -215/+1 region of the promoter was correlated with increased levels of endogenous E2F1 and p21 proteins at the G1/S boundary. The significance of transactivation of the p21 gene by E2F is that p21 function is important in cell cycle progression as well as for cell cycle arrest. Indeed, E2F-induced levels of p21 protein during the G1/ S transition is consistent with the recent findings demonstrating that p21 acts as an assembly factor for kinase active cyclin/cdk/p21 complexes.
- Published
- 1998
257. Interaction of E2F/Rb Family Members with Factor Binding to Co repressor Element on B- myb and E2F1 Promoters
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Yusuke Nakajima
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Transcription, Genetic ,Cell Cycle Proteins ,E2F4 Transcription Factor ,Biology ,Mice ,E2F2 Transcription Factor ,Transcription (biology) ,Tumor Cells, Cultured ,Animals ,Humans ,E2F1 ,Promoter Regions, Genetic ,E2F ,Psychological repression ,E2F4 ,Transcription factor ,Cell Cycle ,Gene Expression Regulation, Developmental ,General Medicine ,Molecular biology ,E2F Transcription Factors ,Rats ,DNA-Binding Proteins ,Genes, cdc ,DNA binding site ,E2F3 Transcription Factor ,Mutation ,Trans-Activators ,biological phenomena, cell phenomena, and immunity ,Carrier Proteins ,Transcription Factor DP1 ,Corepressor ,E2F1 Transcription Factor ,Retinoblastoma-Binding Protein 1 ,Transcription Factors - Abstract
The E2F transcription factor plays an important role in controlling the expression of genes required for cell cycle progression. The transcription of a number of these genes, including E2F1 and B-myb, is repressed in G0/early G1 at E2F DNA binding sites mediated by interaction of E2F with the Rb family member proteins. It was shown that a corepressor element CHR, which was originally identified in the B-myb promoter, is also responsible for the repression of the E2F1 promoter. The mutation of the CHR element adjacent to E2F sites leads to a derepression of the E2F1 promoter in quiescent cells. The CHR-mutated promoter is activated by the E2F family of proteins (E2F1, E2F2, E2F3, and E2F4) but unable to be repressed by any of the Rb family members (Rb, p107, and p130) to the level of the wild-type promoter activity in G0, indicating that the repression by the Rb family members is required for the corepressor element. Moreover, it was shown that a factor specifically bound to the CHR element is co-purified with E2F by DNA affinity purification and co-immunoprecipitated with E2F4 and the Rb family members. These results seggested that E2F and the Rb family member proteins regulate the transcription of the E2F1 and B-myb genes by associating with an additional corepressor protein.
- Published
- 1998
258. Position-Dependent Transcriptional Regulation of the Murine Dihydrofolate Reductase Promoter by the E2F Transactivation Domain
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Peggy J. Farnham, Jill E. Slansky, and Christopher J. Fry
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Transcriptional Activation ,endocrine system ,Transcription, Genetic ,Response element ,Cell Cycle Proteins ,E2F4 Transcription Factor ,Mice ,Transactivation ,parasitic diseases ,Dihydrofolate reductase ,Animals ,Humans ,heterocyclic compounds ,Cloning, Molecular ,Promoter Regions, Genetic ,Molecular Biology ,E2F4 ,Transcription factor ,E2F5 Transcription Factor ,Binding Sites ,Base Sequence ,Models, Genetic ,biology ,Promoter ,3T3 Cells ,DNA ,Cell Biology ,DNA-binding domain ,Molecular biology ,E2F Transcription Factors ,DNA-Binding Proteins ,Tetrahydrofolate Dehydrogenase ,enzymes and coenzymes (carbohydrates) ,Mutation ,biology.protein ,biological phenomena, cell phenomena, and immunity ,Carrier Proteins ,Transcription Factor DP1 ,E2F1 Transcription Factor ,HeLa Cells ,Retinoblastoma-Binding Protein 1 ,Transcription Factors ,Research Article - Abstract
Activity of the dihydrofolate reductase (dhfr) promoter increases at the G1-S-phase boundary of the cell cycle. Mutations that abolish protein binding to an E2F element in the dhfr promoter also abolish the G1-S-phase increase in dhfr transcription, indicating that transcriptional regulation is mediated by the E2F family of proteins. To investigate the mechanism by which E2F regulates dhfr transcription, we moved the E2F element upstream and downstream of its natural position in the promoter. We found that the E2F element confers growth regulation to the dhfr promoter only when it is proximal to the transcription start site. Using a heterologous E2F element, we showed that position-dependent regulation is a property that is promoter specific, not E2F element specific. We demonstrated that E2F-mediated growth regulation of dhfr transcription requires activation of the dhfr promoter in S phase and that the C-terminal activation domains of E2F1, E2F4, and E2F5, when fused to the Gal4 DNA binding domain, are sufficient to specify position-dependent activation. To further investigate the role of activation in dhfr regulation, we tested other transactivation domains for their ability to activate the dhfr promoter. We found that the N-terminal transactivation domain of VP16 cannot activate the dhfr promoter. We propose that, unlike other E2F-regulated promoters, robust transcription from the dhfr promoter requires an E2F transactivation domain close to the transcription start site.
- Published
- 1997
259. The Role of Cell Cycle Machinery in Ischemic Neuronal Death
- Author
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Iyirhiaro, Grace O.
- Subjects
Cell death ,Inflammation ,Cerebral Ischemia ,p130 ,Cdk4 ,Cdks ,Cdk5 ,Cell Cycle ,Neuronal death ,Flavopiridol ,B-Myb ,Minocycline ,Neuroprotection ,Stroke ,C-Myb ,Cdc25 ,pRb ,E2F4 ,Cyclin D1 ,Excitotoxicity - Abstract
Ischemic stroke occurs as a result of a lack or severe reduction of blood supply to the brain. Presently therapeutic interventions are limited and there is a need to develop new and efficacious stroke treatments. To this end, a great deal of research effort has been devoted to studying the potential molecular mechanisms involved in ischemic neuronal death. Correlative evidence demonstrated a paradoxical activation of the cell cycle machinery in ischemic neurons. The levels and activity of key cell cycle regulators including cyclin D1, Cdk2 and Cdk4 are upregulated following ischemic insults. However, the functional relevance of these various signals following ischemic injury was unclear. Accordingly, the research described in this thesis address the functional relevance of the activation of the cell cycle machinery in ischemic neuronal death. The data indicate that the inhibition of Cdk4 protects neurons from ischemia-induced delayed death, whereas abrogation of Cdk5 activity prevents excitotoxicity-induced damage in vitro and in vivo. Examination of upstream activators of mitotic-Cdks showed that Cdc25A is a critical mediator of delayed ischemic neuronal death. Investigation of the potential molecular mechanism by which cell cycle regulators induced neuronal death revealed perturbations in the levels and activity of key downstream targets of Cdk4. The retinoblastoma protein family members, pRb and p130 are increasingly phosphorylated following ischemic stresses. Importantly, p130 and E2F4 proteins are drastically reduced following ischemic insults. Additionally, E2F1 association with promoters of pro-apoptotic genes are induced while that of E2F4 is reduced. These changes appear to be important determinants in ischemic neuronal death. Cumulatively, the data supports the activation of the cell cycle machinery as a pathogenic signal contributing to ischemic neuronal death. The development of neuroprotectant strategies for stroke has been hampered in part by its complex pathophysiology. Previous research indicated that flavopiridol, a general CDK-inhibitor, is unable to provide sustained neuroprotection beyond one week following cerebral ischemia. The potential benefit of combining flavopiridol with another neuroprotectant, minocycline, was explored. The data indicate that while this approach provided histological protection 10 weeks after insult, the protected neurons are not functional due to progressive dendritic degeneration. This evidence indicates that targeting cell cycle pathways in stroke while important must be combined with other therapeutic modalities to fully treat stroke-induced damage.
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- 2013
- Full Text
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260. Polo-like kinase 4 transcription is activated via CRE and NRF1 elements, repressed by DREAM through CDE/CHR sites and deregulated by HPV E7 protein
- Author
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Gerd A. Müller, Axel Wintsche, Marianne Quaas, Martin Fischer, and Kurt Engeland
- Subjects
Cyclin-Dependent Kinase Inhibitor p21 ,Transcriptional Activation ,Papillomavirus E7 Proteins ,Molecular Sequence Data ,Down-Regulation ,Cell Cycle Proteins ,Polo-like kinase ,Biology ,Protein Serine-Threonine Kinases ,Gene Regulation, Chromatin and Epigenetics ,Response Elements ,Cell Line ,Mice ,Genetics ,Transcriptional regulation ,Animals ,Humans ,Cell Cycle Protein ,Promoter Regions, Genetic ,E2F4 ,Mitosis ,Binding Sites ,Base Sequence ,Nuclear Respiratory Factor 1 ,Cell Cycle ,Promoter ,Cell cycle ,Molecular biology ,Cell Cycle Gene ,Repressor Proteins ,NIH 3T3 Cells ,Trans-Activators ,Tumor Suppressor Protein p53 - Abstract
Infection by oncogenic viruses is a frequent cause for tumor formation as observed in cervical cancer. Viral oncoproteins cause inactivation of p53 function and false transcriptional regulation of central cell cycle genes. Here we analyze the regulation of Plk4, serving as an example of many cell cycle- and p53-regulated genes. Cell cycle genes are often repressed via CDE and CHR elements in their promoters and activated by NF-Y binding to CCAAT-boxes. In contrast, general activation of Plk4 depends on NRF1 and CRE sites. Bioinformatic analyses imply that NRF1 and CRE are central elements of the transcriptional network controlling cell cycle genes. We identify CDE and CHR sites in the Plk4 promoter, which are necessary for binding of the DREAM (DP, RB-like, E2F4 and MuvB) complex and for mediating repression in G0/G1. When cells progress to G2 and mitosis, DREAM is replaced by the MMB (Myb-MuvB) complex that only requires the CHR element for binding. Plk4 expression is downregulated by the p53-p21(WAF1/CIP1)-DREAM signaling pathway through the CDE and CHR sites. Cell cycle- and p53-dependent repression is abrogated by HPV E7 oncoprotein. Together with genome-wide analyses our results imply that many cell cycle genes upregulated in tumors by viral infection are bound by DREAM through CDE/CHR sites.
- Published
- 2013
261. Functional impact of colorectal cancer-associated mutations in the transcription factor E2F4
- Author
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Etienne Lemieux, Benjamin Bian, Nathalie Rivard, Marie-Christine Paquin, and Caroline Leblanc
- Subjects
Cancer Research ,Transcription, Genetic ,Mutant ,E2F4 Transcription Factor ,Biology ,Frameshift mutation ,Trinucleotide Repeats ,Cell Line, Tumor ,Humans ,Amino Acid Sequence ,Gene ,E2F4 ,Cell Proliferation ,Reporter gene ,Retinoblastoma-Like Protein p130 ,Cell Cycle ,Sequence Analysis, DNA ,Cell cycle ,HCT116 Cells ,Molecular biology ,HEK293 Cells ,Oncology ,Amino Acid Substitution ,Tumor progression ,Mutation ,Cancer research ,Microsatellite Instability ,Caco-2 Cells ,Transcription Factor E2F4 ,Colorectal Neoplasms ,HT29 Cells - Abstract
The transcription factor E2F4 plays a critical role in cell cycle progression of normal and cancerous intestinal epithelial cells. Contrary to other E2Fs, the coding region of the E2F4 gene contains a longer spacer segment of a CAG trinucleotide repeat sequence encoding 13 consecutive serine residues, which is highly vulnerable to frameshift mutations in situations of genetic instability. Mutations in this region of the E2F4 gene have been observed in colorectal tumors with microsatellite instability. However, the effect of these changes on its function in colorectal cancer cells is currently unknown. We generated E2F4(CAG)₁₂ and E2F4(CAG)₁₄ mutants and compared their activity to the E2F4 wild-type, E2F4(CAG)₁₃. Luciferase assays with the thymidine kinase-luc reporter gene revealed that the mutants were more transcriptionally active than wild-type E2F4. The mechanism of increased activity of E2F4 was primarily related to protein stability, due to a significantly enhanced half-life of E2F4 mutants comparatively to that of wild-type E2F4. However, the association with the pocket protein p130/RBL2 did not account for this increased protein stability. Sequencing analysis of the endogenous E2F4 gene in a series of colorectal cancer cell lines showed that the microsatellite-unstable cell line SW48 exhibited a serine deletion in this gene. Accordingly, E2F4 half-life was much more elevated in SW48 cells in comparison to Caco-2/15, a microsatellite-stable cell line. Notably, in soft-agar assays, both mutants more potently increased anchorage-independent growth in comparison to wild-type E2F4. In conclusion, our data demonstrate that cancer-associated E2F4 mutations enhance the capacity of colorectal cancer cells to grow without anchorage, thereby contributing to tumor progression.
- Published
- 2013
262. Inorganic arsenic exposure induces E2F-dependent G0/G1 arrest via an increase in retinoblastoma family protein p130 in B-cell lymphoma A20 cells
- Author
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Kazuyuki Okamura, Keiko Nohara, and Daisuke Miki
- Subjects
Cyclin-Dependent Kinase Inhibitor p21 ,Lymphoma, B-Cell ,Cell cycle checkpoint ,Arsenites ,Cell Cycle Proteins ,E2F4 Transcription Factor ,Biology ,Mice ,chemistry.chemical_compound ,Cell Line, Tumor ,Genetics ,medicine ,Animals ,Phosphorylation ,RNA, Small Interfering ,E2F ,E2F4 ,Cyclin-Dependent Kinase Inhibitor p16 ,Arsenite ,Retinoblastoma-Like Protein p130 ,Ubiquitin ,Retinoblastoma ,Cell Cycle Checkpoints ,Cell Biology ,medicine.disease ,Molecular biology ,Blot ,Gene Expression Regulation ,chemistry ,embryonic structures ,Proteasome inhibitor ,Tumor Suppressor Protein p53 ,biological phenomena, cell phenomena, and immunity ,medicine.drug - Abstract
Inorganic arsenic exerts toxic effect on multiple systems including the immune system. We previously showed in a study on mouse thymocytes and B-cell lymphoma A20 cells that arsenite induces cell cycle arrest at G0/G1 by suppressing expression of E2F-target genes. In this study, we furthermore investigated the involvement of retinoblastoma (RB) family proteins in E2F-dependent cell cycle arrest by arsenite. Arsenite exposure of A20 cells was showed to increase the protein level of p130, a RB family member, without changing the mRNA level. Suppression of arsenite-induced p130 by siRNA reduced the G0/G1 phase, indicating that p130 accumulation is responsible for arsenite-induced G0/G1 arrest. The accumulated p130 was shown to increase the p130 complex with E2F4, a transcription-suppressing E2F. Comparison by Western blotting of arsenite-induced p130 and p130 accumulated by a proteasome inhibitor suggested that arsenite-induced p130 is hypophosphorylated and hypoubiquitinated and refractory to proteasome-dependent degradation. We also showed that arsenite increases mRNA and protein of p16(INK4a), an inhibitor of CDK4/6 that phosphorylates p130. Down-regulation of arsenite-induced p16(INK4a) by siRNA suppressed the p130 accumulation. We propose a novel mechanism in which arsenite inhibits phosphorylation/ubiquitin-dependent proteasome degradation of p130 by inducing p16(INK4a) and the accumulated p130 causes cell cycle arrest with E2F4.
- Published
- 2013
263. Loss of ARF sensitizes transgenic BRAFV600E mice to UV-induced melanoma via suppression of XPC
- Author
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Rutao Cui, Guo-fu Hu, Chi Luo, Miaofen G. Hu, Philip N. Tsichlis, Jinghao Sheng, Frank G. Haluska, Zhengping Xu, and Philip W. Hinds
- Subjects
Proto-Oncogene Proteins B-raf ,Cancer Research ,Neoplasms, Radiation-Induced ,DNA Repair ,DNA repair ,DNA damage ,Ultraviolet Rays ,Transgene ,Melanoma, Experimental ,Mice, Transgenic ,E2F4 Transcription Factor ,Biology ,Article ,Mice ,CDKN2A ,Cell Line, Tumor ,medicine ,Animals ,Humans ,Promoter Regions, Genetic ,E2F4 ,neoplasms ,Melanoma ,Cells, Cultured ,Cyclin-Dependent Kinase Inhibitor p16 ,Mice, Knockout ,Oncogene ,DNA Methylation ,medicine.disease ,DNA-Binding Proteins ,Mice, Inbred C57BL ,Oncology ,Cancer research ,Tumor Suppressor Protein p53 ,Transcription Factor DP1 ,Nucleotide excision repair - Abstract
Both genetic mutations and UV irradiation (UVR) can predispose individuals to melanoma. Although BRAFV600E is the most prevalent oncogene in melanoma, the BRAFV600E mutant is not sufficient to induce tumors in vivo. Mutation at the CDKN2A locus is another melanoma-predisposing event that can disrupt the function of both p16INK4a and ARF. Numerous studies have focused on the role of p16INK4a in melanoma, but the involvement of ARF, a well-known p53 activator, is still controversial. Using a transgenic BRAFV600E mouse model previously generated in our laboratory, we report that loss of ARF is able to enhance spontaneous melanoma formation and cause profound sensitivity to neonatal UVB exposure. Mechanistically, BRAFV600E and ARF deletion synergize to inhibit nucleotide excision repair by epigenetically repressing XPC and inhibiting the E2F4/DP1 complex. We suggest that the deletion of ARF promotes melanomagenesis not by abrogating p53 activation but by acting in concert with BRAFV600E to increase the load of DNA damage caused by UVR. Cancer Res; 73(14); 4337–48. ©2013 AACR.
- Published
- 2013
264. Latent transforming growth factor β-binding protein 4 is downregulated in esophageal cancer via promoter methylation
- Author
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Anja Sterner-Kock, Insa Bultmann, Celine Kretschmer, and Anne Conradi
- Subjects
Esophageal Neoplasms ,Biochemistry ,Molecular cell biology ,Cell Movement ,Gene Order ,Promoter Regions, Genetic ,E2F4 ,Multidisciplinary ,GATA1 ,Extracellular Matrix ,Gene Expression Regulation, Neoplastic ,Cell Motility ,Latent TGF-beta binding protein ,Oncology ,DNA methylation ,Azacitidine ,Disease Progression ,Medicine ,Epigenetics ,DNA modification ,Protein Binding ,Research Article ,Esophageal Cancer ,Science ,Biophysics ,Down-Regulation ,Biology ,Decitabine ,Cell Growth ,Transforming Growth Factor beta1 ,Molecular Genetics ,Cell Line, Tumor ,Gastrointestinal Tumors ,Genetics ,Humans ,Gene silencing ,Gene Regulation ,Transcription factor ,Neoplasm Staging ,Binding Sites ,Base Sequence ,Cell growth ,Carcinoma ,Cancers and Neoplasms ,DNA Methylation ,Latent TGF-beta Binding Proteins ,Cancer research ,Gene expression ,Transcription Factors ,Transforming growth factor - Abstract
Latent transforming growth factor β-binding protein 4 (LTBP4) is an extracellular matrix molecule that is a member of important connective tissue networks and is needed for the correct folding and the secretion of TGF-β1. LTBP4 is downregulated in carcinomas of various tissues. Here we show that LTBP4 is also downregulated in adenocarcinomas and squamous cell carcinomas of the esophagus in vitro and in vivo. Re-expression of LTBP4 in esophageal cancer cell lines reduced cell migration ability, whereas cell viability and cell proliferation remained unchanged. Hypermethylation of the promoter regions of the two main human LTBP4 transcriptional forms, LTBP4L and LTBP4S, was found to be involved in LTBP4 silencing. Detailed investigations of the methylation patterns of the promoter regions of LTBP4L and LTBP4S identified GATA1, SP1, E2F4 and SMAD3 as potential transcription factors involved in LTBP4 expression. In in vitro transcription factor activity studies we discovered E2F4 as novel powerful regulator for LTBP4S expression.
- Published
- 2013
265. The Kinase MIRK/DYRK1B Mediates a Reversible Quiescent State in a Subset of Ovarian, Pancreatic and Colon Cancers
- Author
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Eileen Friedman
- Subjects
DYRK1B ,biology ,Downregulation and upregulation ,Chemistry ,Kinase ,p38 mitogen-activated protein kinases ,Cyclin D ,Cancer cell ,Cancer research ,biology.protein ,DREAM complex ,E2F4 - Abstract
The serine/threonine kinase Mirk is an active kinase in pancreatic, ovarian and colon cancers, but is not activated by mutation. Mirk was upregulated or amplified in the majority of resected pancreatic or ovarian adenocarcinomas, and may be selected for by enabling cancer cells to enter a reversible quiescent state and thus survive suboptimal conditions. Mirk/dyrk1B levels and activity are highest when cells are quiescent. Some cancer cells can enter a reversible quiescent phase dependent on p130/Rb2 and Mirk/dyrk1B when deprived of growth factors, while others undergo autophagy or apoptosis. Mirk blocks cell cycle progression in G0 by complexing with GSK3s and destabilizing cyclin D isoforms and by activating by phosphorylation Lin52, which is part of the DREAM complex including p130/Rb2 which sequesters E2F4 and other transcription factors necessary for cells to enter cycle. Mirk transcriptional co-activator activity allows Mirk to decrease ROS levels by increasing expression of a group of antioxidant genes. Since Mirk is activated by oncogenic K-ras/H-ras, its upregulation of antioxidant genes may compensate for the increase in ROS induced by ras oncoproteins. Mirk competes with the SAPK p38 for binding to their common activator MKK3. Thus Mirk is upregulated or amplified in certain pancreatic and ovarian cancers, is an active kinase in these cancers, and under suboptimal growth conditions, maintains these cancer cells in a viable, quiescent state.
- Published
- 2013
266. A unique role for the Rb protein in controlling E2F accumulation during cell growth and differentiation
- Author
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Joseph R. Nevins, Masa-Aki Ikeda, and Laszlo Jakoi
- Subjects
Cell division ,Cellular differentiation ,Molecular Sequence Data ,Cell Cycle Proteins ,E2F4 Transcription Factor ,Biology ,Retinoblastoma Protein ,Cell Line ,Humans ,Amino Acid Sequence ,Cell Cycle Protein ,E2F ,E2F4 ,Cells, Cultured ,Multidisciplinary ,Cell growth ,Cell Cycle ,Retinoblastoma protein ,Cell Differentiation ,Cell cycle ,E2F Transcription Factors ,Cell biology ,DNA-Binding Proteins ,stomatognathic diseases ,biology.protein ,biological phenomena, cell phenomena, and immunity ,Carrier Proteins ,Transcription Factor DP1 ,Cell Division ,Retinoblastoma-Binding Protein 1 ,Transcription Factors ,Research Article - Abstract
Examination of the interactions involving transcription factor E2F activity during cell growth and terminal differentiation suggests distinct roles for Rb family members in the regulation of E2F accumulation. The major species of E2F in quiescent cells is a complex containing the E2F4 product in association with the Rb-related p130 protein. As cells enter the cell cycle, this complex disappears, and there is a concomitant accumulation of free E2F activity of which E2F4 is a major component. E2F4 then associates with the Rb-related p107 protein as cells enter S phase. Rb can be found in interactions with each E2F species, including E2F4, during G1, but there appears to be a limited amount of Rb with respect to E2F, likely due to the maintenance of most Rb protein in an inactive state by phosphorylation. A contrasting circumstance can be found during the induction of HL60 cell differentiation. As these cells exit the cell cycle, active Rb protein appears to exceed E2F, as there is a marked accumulation of E2F-Rb interactions, involving all E2F species, including E2F4, which is paralleled by the conversion of Rb from a hyperphosphorylated state to a hypophosphorylated state. These results suggest that the specific ability of Rb protein to interact with each E2F species, dependent on concentration of active Rb relative to accumulation of E2F, may be critical in cell-growth decisions.
- Published
- 1996
267. E2F-4 Switches from p130 to p107 and pRB in Response to Cell Cycle Reentry
- Author
-
Kenneth H. Moberg, M A Starz, and Jacqueline A. Lees
- Subjects
Blotting, Western ,Molecular Sequence Data ,Cell Cycle Proteins ,Retinoblastoma-Like Protein p107 ,E2F4 Transcription Factor ,Biology ,Retinoblastoma Protein ,E2F2 Transcription Factor ,Tumor Cells, Cultured ,Humans ,Nuclear protein ,Cell Cycle Protein ,E2F ,Molecular Biology ,E2F4 ,Base Sequence ,Retinoblastoma-Like Protein p130 ,Cell Cycle ,Retinoblastoma protein ,Antibodies, Monoclonal ,Nuclear Proteins ,Proteins ,E2F1 Transcription Factor ,Cell Biology ,Cell cycle ,Phosphoproteins ,Molecular biology ,E2F Transcription Factors ,Cell biology ,DNA-Binding Proteins ,stomatognathic diseases ,E2F3 Transcription Factor ,biology.protein ,biological phenomena, cell phenomena, and immunity ,Carrier Proteins ,Oligonucleotide Probes ,Transcription Factor DP1 ,Retinoblastoma-Binding Protein 1 ,Transcription Factors ,Research Article - Abstract
The E2F transcription factor couples the coordinate expression of cell cycle proteins to their appropriate transition points. Its activity is controlled by the cell cycle regulators pRB, p107, and p130. These bind to E2F at defined but distinct stages of the cell cycle. Using specific antisera, we have identified the DP and E2F components of each of these species. Although present at very different levels, DP-1 and DP-2 are evenly distributed among each of these complexes. In contrast, the individual E2Fs have distinctly different binding profiles. Consistent with previous studies, E2F-1, E2F-2, and E2F-3 bind specifically to the retinoblastoma protein. In each case, their expression and DNA binding activity are restricted to post-G1/S fractions. Surprisingly, E2F-1 and E2F-3 make unequal contributions to the pRB-associated and free E2F activity, suggesting that these proteins perform different cell cycle functions. Most significantly, this study showed E2F-4 accounts for the vast majority of the endogenous E2F activity. In arrested cells, E2F-4 is sequestered by the p130 protein. However, as the cells pass the G1-to-S transition, the levels of pRB and p107 increase and E2F-4 now associates with both of these regulators. Despite this, a considerable amount of E2F-4 exists as free E2F. In G1 cells, this accounts for almost all of the free activity. Once the cells enter S phase, free E2F is composed of an equal mixture of E2F-4 and E2F-1.
- Published
- 1996
268. Weighted gene co-expression network analysis in identification of endometrial cancer prognosis markers
- Author
-
Yan Li Xu, Xiao Lu Zhu, Juan Wang, Yin Cheng Teng, and Zhi Hong Ai
- Subjects
Cancer Research ,Transcription, Genetic ,Epidemiology ,Chromosomal Proteins, Non-Histone ,E2F4 Transcription Factor ,Zinc Finger Protein GLI1 ,GLI1 ,Proto-Oncogene Proteins ,Transcriptional regulation ,Biomarkers, Tumor ,Pre-B-Cell Leukemia Transcription Factor 1 ,Humans ,E2F4 ,Regulation of gene expression ,Homeodomain Proteins ,Oncogene Proteins ,Analysis of Variance ,N-Myc Proto-Oncogene Protein ,biology ,Gene Expression Profiling ,Public Health, Environmental and Occupational Health ,PAX5 Transcription Factor ,Nuclear Proteins ,Endometrial Neoplasms ,Gene expression profiling ,DNA-Binding Proteins ,Gene Expression Regulation, Neoplastic ,Oncology ,Proto-Oncogene Proteins c-bcl-2 ,biology.protein ,Cancer research ,Gene co-expression network ,PAX5 ,Female ,Collagen Type V ,Insulin-Like Growth Factor Binding Protein 6 ,Signal Transduction ,Transcription Factors - Abstract
Objective: Endometrial cancer (EC) is the most common gynecologic malignancy. Identification of potential biomarkers of EC would be helpful for the detection and monitoring of malignancy, improving clinical outcomes. Methods: The Weighted Gene Co-expression Network Analysis method was used to identify prognostic markers for EC in this study. Moreover, underlying molecular mechanisms were characterized by KEGG pathway enrichment and transcriptional regulation analyses. Results: Seven gene co-expression modules were obtained, but only the turquoise module was positively related with EC stage. Among the genes in the turquoise module, COL5A2 (collagen, type V, alpha 2) could be regulated by PBX (pre-B-cell leukemia homeobox 1)1/2 and HOXB1(homeobox B1) transcription factors to be involved in the focal adhesion pathway; CENP-E (centromere protein E, 312kDa) by E2F4 (E2F transcription factor 4, p107/p130-binding); MYCN (v-myc myelocytomatosis viral related oncogene, neuroblastoma derived [avian]) by PAX5 (paired box 5); and BCL-2 (B-cell CLL/ lymphoma 2) and IGFBP-6 (insulin-like growth factor binding protein 6) by GLI1. They were predicted to be associated with EC progression via Hedgehog signaling and other cancer related-pathways. Conclusions: These data on transcriptional regulation may provide a better understanding of molecular mechanisms and clues to potential therapeutic targets in the treatment of EC.
- Published
- 2012
269. Functional interaction between E2F-4 and p130: evidence for distinct mechanisms underlying growth suppression by different retinoblastoma protein family members
- Author
-
G Vairo, David M. Livingston, and Doron Ginsberg
- Subjects
Transcriptional Activation ,Cell cycle checkpoint ,T-Lymphocytes ,E2F4 Transcription Factor ,Resting Phase, Cell Cycle ,Retinoblastoma Protein ,DNA-binding protein ,Tumor Cells, Cultured ,Genetics ,Humans ,E2F ,E2F4 ,Transcription factor ,Retinoblastoma-Like Protein p130 ,biology ,G1 Phase ,Retinoblastoma protein ,Proteins ,Cell cycle ,Phosphoproteins ,Growth Inhibitors ,Cell biology ,DNA-Binding Proteins ,stomatognathic diseases ,biology.protein ,biological phenomena, cell phenomena, and immunity ,Immediate early gene ,Protein Binding ,Transcription Factors ,Developmental Biology - Abstract
Little is known of the mechanisms controlling the G0/G1 transition of the cell cycle. The induction of immediate early gene expression, thought to be important for this process, suggests that the key factors controlling this transition preexist in quiescent cells. The E2F family of transcription factors likely play an important role in this process, because E2F DNA-binding activity exists in quiescent cells, and the induction of at least some immediate early genes requires intact E2F regulatory promoter sites. Here, we show that the major G0 E2F activity of primary human T cells, E2F-4, is stably bound to the p130 pocket protein in association with a DP heterodimerization partner. p130-E2F-4 binding has functional implications because p130 effectively suppressed E2F-4-mediated trans-activation, and coexpression of E2F4 overcame p130-mediated G1 arrest more efficiently than RB-induced G1 blockade. Conversely, E2F-1 overrode an RB-induced G1 block more efficiently than E2F-4. Thus, p130 and RB appear to induce cell cycle arrest via biochemically distinct mechanisms that involve different E2F family members.
- Published
- 1995
270. E2F4 (E2F transcription factor 4, p107/p130-binding)
- Author
-
Nathalie Rivard and Marie-Christine Paquin
- Subjects
Cancer Research ,Sp1 transcription factor ,biology ,General transcription factor ,Hematology ,TCF4 ,Molecular biology ,Activating transcription factor 2 ,Oncology ,Sp3 transcription factor ,embryonic structures ,TAF2 ,Genetics ,biology.protein ,E2F1 ,biological phenomena, cell phenomena, and immunity ,E2F4 - Abstract
Review on E2F4 (E2F transcription factor 4, p107/p130-binding), with data on DNA, on the protein encoded, and where the gene is implicated.
- Published
- 2012
271. Gene expression of the lysophosphatidic acid receptor 1 is a target of transforming growth factor beta
- Author
-
Deborah A. Lebman, Xianjun Fang, Abir Mukherjee, and Jinhua Wu
- Subjects
Cancer Research ,Transcription, Genetic ,Response Elements ,migration ,Article ,03 medical and health sciences ,TGFβ ,0302 clinical medicine ,Cell Movement ,Transforming Growth Factor beta ,Cell Line, Tumor ,Genetics ,SMAD binding ,Humans ,cancer ,RNA, Messenger ,Smad3 Protein ,RNA, Small Interfering ,Receptors, Lysophosphatidic Acid ,Promoter Regions, Genetic ,Molecular Biology ,E2F4 ,030304 developmental biology ,Smad4 Protein ,0303 health sciences ,Gene knockdown ,biology ,LPA1 ,Promoter ,Transforming growth factor beta ,invasion ,Molecular biology ,Gene Expression Regulation, Neoplastic ,LPA ,030220 oncology & carcinogenesis ,biology.protein ,RNA Interference ,Signal transduction ,Chromatin immunoprecipitation ,Transforming growth factor ,Signal Transduction - Abstract
The lysophosphatidic acid (LPA) receptor LPA1/Edg2 is the first identified LPA receptor. Although its wide tissue distribution and biological functions have been well studied, little is known about how LPA1 is transcriptionally regulated. In the current study, we showed that LPA1 is a physiological target of transforming growth factor beta (TGFβ)-mediated repression. In both normal and neoplastic cells, TGFβ inhibits LPA1 promoter activity, LPA1 mRNA expression and LPA1-dependent chemotaxis and tumor cell invasion. Knockdown of the TGFβ intracellular effector Smad3 or Smad4 with lentivirally transduced short hairpin RNA relieved these inhibitory effects of TGFβ. Interestingly, the LPA1 promoter contains two potential TGFβ inhibitory elements (TIEs), each consisting of a Smad-binding site and an adjacent E2F4/5 element, structurally similar to the TIE found on the promoter of the well-defined TGFβ target gene c-myc. Deletion and point mutation analyses indicate that the distal TIE located at 401 bp from the transcription initiation site, is required for TGFβ repression of the LPA1 promoter. A DNA pull-down assay showed that the -401 TIE was capable of binding Samd3 and E2F4 in TGFβ-treated cells. TGFβ-induced binding of the Smad complex to the native -401 TIE sequence of the LPA1 gene promoter was further verified by chromatin immunoprecipitation assays. We therefore identified a novel role of TGFβ in the control of LPA1 expression and LPA1-coupled biological functions, adding LPA1 to the list of TGFβ-repressed target genes.
- Published
- 2012
272. Toxicogenomic activity of gemcitabine in two TP53-mutated bladder cancer cell lines: special focus on cell cycle-related genes
- Author
-
Glenda Nicioli da Silva, Elaine Aparecida de Camargo, and Daisy Maria Favero Salvadori
- Subjects
Antimetabolites, Antineoplastic ,Cell cycle checkpoint ,Cell Survival ,Cell Cycle Proteins ,Biology ,medicine.disease_cause ,Deoxycytidine ,Downregulation and upregulation ,Cell Line, Tumor ,Genetics ,medicine ,Humans ,CHEK1 ,Molecular Biology ,E2F4 ,Mutation ,Genome, Human ,Cell Cycle ,General Medicine ,Cell cycle ,Molecular biology ,Gemcitabine ,Gene Expression Regulation, Neoplastic ,Urinary Bladder Neoplasms ,biology.protein ,Cyclin-dependent kinase 6 ,Tumor Suppressor Protein p53 ,Transcriptome ,medicine.drug - Abstract
Because of its lower toxicity and good tolera- bility and response, gemcitabine has been described as one of the most highly promising drugs for urinary bladder cancer therapy. Its phosphorylated active-dFdCTP metab- olite can incorporate into DNA, causing replication blockage. Additionally, it is known that mutations in the TP53 gene are related to the high recurrence rate of these neoplasias. Based on these premises, we investigated the effects of gemcitabine on the expression of the cell cycle- related genes in two different TP53-mutated bladder tran- sitional carcinoma cell lines-5637 (from a moderate-grade tumor with a TP53 allele carrying two mutations) and T24 (from an invasive tumor with a TP53 allele encoding an in- frame deletion). Cell viability and morphology analyses (phase-contrast photomicrographs), Nuclear Division Index and pathway-specific quantitative RT-PCR gene arrays were performed. Treatment with gemcitabine led to the following results: (1) a significant decrease of viable T24 cells after treatment at the highest concentration (3.12 lM) tested; (2) scattered, elongated and vacuolated 5637 and T24 cells; (3) a cytostatic effect in both cell lines; and (4) significant upregulation of the BRCA1, CCNE1, CDK2, CDK6, CDKN1A, CDKN2B, E2F4, GADD45A, MAD2L2, CCNH, SERTAD1, CDC1, and CHEK1 genes. Gemcitabine had distinct toxicogenomic effects in the bladder transi- tional carcinoma cell lines with two different TP53 muta- tions. However, independent of the type of mutation and tumor grade, gemcitabine induced cell cycle arrest; upregulation of DNA repair-related genes, G1/S transition, apoptosis and activation of transcription factors, mainly by upregulation of the CCNE1, CDKN1A and GADD45A genes.
- Published
- 2012
273. Carbon Monoxide Inhibits Lung Fibrosis By Inducing Cellular Quiescence Via E2F4
- Author
-
Ying Shi, Jiaofei Cao, Danielle Morse, and Augustine M.K. Choi
- Subjects
chemistry.chemical_compound ,chemistry ,Cellular quiescence ,Lung fibrosis ,Cancer research ,E2F4 ,Carbon monoxide - Published
- 2012
274. Anti-apoptotic function of the E2F transcription factor 4 (E2F4)/p130, a member of retinoblastoma gene family in cardiac myocytes
- Author
-
Dharmendra Dingar, Jian Zou, Rüdiger von Harsdorf, Filip Konecny, and Xuetao Sun
- Subjects
Male ,Programmed cell death ,Cellular differentiation ,Apoptosis ,Histone Deacetylase 1 ,E2F4 Transcription Factor ,Biology ,03 medical and health sciences ,Mice ,0302 clinical medicine ,Transcriptional repressor complex ,E2F1 ,Animals ,Myocytes, Cardiac ,Promoter Regions, Genetic ,Molecular Biology ,Transcription factor ,E2F4 ,Cells, Cultured ,030304 developmental biology ,Cell Nucleus ,Mice, Knockout ,0303 health sciences ,Promoter ,3. Good health ,Rats ,Protein Transport ,030220 oncology & carcinogenesis ,embryonic structures ,Cancer research ,biological phenomena, cell phenomena, and immunity ,Cardiology and Cardiovascular Medicine ,Chromatin immunoprecipitation ,E2F1 Transcription Factor ,Protein Binding - Abstract
The E2F4–p130 transcriptional repressor complex is a cell-cycle inhibitor in mitotic cells. However, the role of E2F4/p130 in differentiated cells is largely unknown. We investigated the role of E2F4/p130 in the regulation of apoptosis in postmitotic cardiomyocytes. Here we demonstrate that E2F4 can inhibit hypoxia-induced cell death in isolated ventricular cardiomyocytes. As analyzed by chromatin immunoprecipitation, the E2F4–p130-repressor directly blocks transcription of essential apoptosis-related genes, E2F1, Apaf-1, and p73α through recruitment of histone deacetylase 1 (HDAC1). In contrast, diminution of the E2F4–p130–HDAC1-repressor and recruitment of E2F1 and histone acetylase activity to these E2F-regulated promoters is required for the execution of cell death. Expression of kinase-dead HDAC1.H141A or HDAC-binding deficient p130ΔHDAC1 abolishes the antiapoptotic effect of E2F4. Moreover, histological examination of E2F4−/− hearts revealed a markedly enhanced degree of cardiomyocyte apoptosis. Taken together, our genetic and biochemical data delineate an essential negative function of E2F4 in cardiac myocyte apoptosis.
- Published
- 2012
275. Zbtb7 suppresses the expression of CDK2 and E2F4 in liver cancer cells: Implications for the role of Zbtb7 in cell cycle regulation
- Author
-
Wei Xiong, Xuyu Zu, Xuefeng Yang, Jing Tang, Feng Liu, Yuan Zhang, and Yuyang Jiang
- Subjects
Cancer Research ,Carcinoma, Hepatocellular ,Cellular differentiation ,Cell ,Down-Regulation ,E2F4 Transcription Factor ,Biology ,medicine.disease_cause ,Biochemistry ,Cell Line, Tumor ,Genetics ,medicine ,Humans ,RNA, Small Interfering ,Promoter Regions, Genetic ,Molecular Biology ,E2F4 ,Transcription factor ,Cell Cycle ,Cyclin-Dependent Kinase 2 ,Liver Neoplasms ,Cyclin-dependent kinase 2 ,Promoter ,Hep G2 Cells ,Cell cycle ,G1 Phase Cell Cycle Checkpoints ,Cell biology ,DNA-Binding Proteins ,medicine.anatomical_structure ,Oncology ,biology.protein ,Cancer research ,Molecular Medicine ,RNA Interference ,Carcinogenesis ,Transcription Factors - Abstract
Zbtb7, a member of the POK protein family, is involved in tumorigenesis and cellular differentiation by acting as a crucial transcription factor, but its role in cell cycle modulation remains uncharacterized. In the present study, CDK2 and E2F4, two cell cycle regulators, are shown to be downregulated at the mRNA and protein levels by Zbtb7 in HepG2 and QGY7703 cells. Moreover, we demonstrate that the activities of CDK2 and E2F4 promoters were suppressed by the modulation of Zbtb7 levels and that Zbtb7 represses promoter activities through a mechanism involving direct binding of Zbtb7 to the promoters. Furthermore, it was identified that the site at -259 to -252 within the CDK2 promoter is responsible for Zbtb7-induced repression of the promoter activity. It was found that siRNA‑induced knockdown of Zbtb7 resulted in the suppression of cell cycle progression in HepG2 and QGY7703 cells. Collectively, these data indicate that CDK2 and E2F4 are the downstream targets of Zbtb7, and Zbtb7 may be a cell cycle modulator by regulating the expression of cell cycle-associated genes in liver cancer cells.
- Published
- 2012
276. E2F6 associates with BRG1 in transcriptional regulation
- Author
-
Joseph R. Nevins and Janet Y. Leung
- Subjects
Chromatin Immunoprecipitation ,Transcription, Genetic ,Immunoprecipitation ,DNA transcription ,Repressor ,E2F6 Transcription Factor ,lcsh:Medicine ,E2F4 Transcription Factor ,Biology ,Biochemistry ,Cell Growth ,Molecular Genetics ,03 medical and health sciences ,0302 clinical medicine ,Molecular cell biology ,Two-Hybrid System Techniques ,Genetics ,Humans ,Gene Regulation ,Promoter Regions, Genetic ,lcsh:Science ,E2F4 ,030304 developmental biology ,Genes, Dominant ,Regulation of gene expression ,0303 health sciences ,Multidisciplinary ,lcsh:R ,DNA Helicases ,Nuclear Proteins ,Proteins ,Computational Biology ,Promoter ,Molecular biology ,SWI/SNF ,Regulatory Proteins ,Gene Expression Regulation ,030220 oncology & carcinogenesis ,SMARCA4 ,lcsh:Q ,Gene expression ,Gene Function ,biological phenomena, cell phenomena, and immunity ,Chromatin immunoprecipitation ,E2F1 Transcription Factor ,Protein Binding ,Transcription Factors ,Research Article - Abstract
The E2F6 protein functions as an Rb-independent repressor of gene transcription. We have previously provided evidence suggesting a role for E2F6 in repression of E2F-responsive genes at S phase. Here, we have identified BRG1, the ATPase subunit of the SWI/SNF chromatin-remodeling complex, as an E2F6 interacting protein. Immunoprecipitation experiments demonstrate that BRG1 binds specifically to E2F6 and E2F4 but not the activator E2Fs. E2F6 was also able to interact with BAF155, a BRG1-associated factor, in the SWI/SNF complex. Chromatin immunoprecipitation assays demonstrate the binding of BRG1 coincident with E2F6 on G1/S gene promoters during S phase. Collectively, our studies suggest that E2F6 may recruit BRG1 in transcriptional regulation of genes important for G1/S phase transition of the cell cycle.
- Published
- 2012
277. Adenovirus E1A directly targets the E2F/DP-1 complex
- Author
-
Dawn M. E. Bowdish, Joe S. Mymryk, Peter Whyte, Matthew J. Cecchini, Ahmed F. Yousef, Frederick A. Dick, Matthew S. Miller, and Peter Pelka
- Subjects
viruses ,Immunology ,Biology ,medicine.disease_cause ,Virus Replication ,Microbiology ,Adenoviridae ,Retinoblastoma-like protein 1 ,Virology ,Protein Interaction Mapping ,medicine ,Humans ,Adenovirus infection ,E2F ,E2F4 ,Promoter ,Cell cycle ,medicine.disease ,Molecular biology ,E2F Transcription Factors ,Virus-Cell Interactions ,Insect Science ,Host-Pathogen Interactions ,Adenovirus E1A Proteins ,biological phenomena, cell phenomena, and immunity ,Transcription Factor DP1 ,HeLa Cells ,Protein Binding - Abstract
Deregulation of the cell cycle is of paramount importance during adenovirus infection. Adenovirus normally infects quiescent cells and must initiate the cell cycle in order to propagate itself. The pRb family of proteins controls entry into the cell cycle by interacting with and repressing transcriptional activation by the E2F transcription factors. The viral E1A proteins indirectly activate E2F-dependent transcription and cell cycle entry, in part, by interacting with pRb and family members to free the E2Fs. We report here that an E1A 13S isoform can unexpectedly activate E2F-responsive gene expression independently of binding to the pRb family of proteins. We demonstrate that E1A binds to E2F/DP-1 complexes through a direct interaction with DP-1. E1A appears to utilize this binding to recruit itself to E2F-regulated promoters, and this allows the E1A 13S protein, but not the E1A 12S protein, to activate transcription independently of interaction with pRb. Importantly, expression of E1A 13S, but not E1A 12S, led to significant enhancement of E2F4 occupancy of E2F sites of two E2F-regulated promoters. These observations identify a novel mechanism by which adenovirus deregulates the cell cycle and suggest that E1A 13S may selectively activate a subset of E2F-regulated cellular genes during infection.
- Published
- 2011
278. Disruption of repressive p130-DREAM complexes by human papillomavirus 16 E6/E7 oncoproteins is required for cell-cycle progression in cervical cancer cells
- Author
-
Roger J. Watson, Rohana Yusof, and Nurshamimi Nor Rashid
- Subjects
Papillomavirus E7 Proteins ,Cell ,Biology ,Malignant transformation ,Virology ,Cell Line, Tumor ,medicine ,Humans ,DREAM complex ,Transcription factor ,E2F4 ,Cell Proliferation ,Human papillomavirus 16 ,Cell growth ,Cell Cycle ,Epithelial Cells ,Kv Channel-Interacting Proteins ,Oncogene Proteins, Viral ,Cell cycle ,humanities ,Repressor Proteins ,medicine.anatomical_structure ,Crk-Associated Substrate Protein ,Cell culture ,embryonic structures ,Host-Pathogen Interactions ,biological phenomena, cell phenomena, and immunity ,Protein Multimerization - Abstract
Human papillomaviruses (HPVs) with tropism for mucosal epithelia are the major aetiological factors in cervical cancer. Most cancers are associated with so-called high-risk HPV types, in particular HPV16, and constitutive expression of the HPV16 E6 and E7 oncoproteins is critical for malignant transformation in infected keratinocytes. E6 and E7 bind to and inactivate the cellular tumour suppressors p53 and Rb, respectively, thus delaying differentiation and inducing proliferation in suprabasal keratinocytes to enable HPV replication. One member of the Rb family, p130, appears to be a particularly important target for E7 in promoting S-phase entry. Recent evidence indicates that p130 regulates cell-cycle progression as part of a large protein complex termed DREAM. The composition of DREAM is cell cycle-regulated, associating with E2F4 and p130 in G0/G1 and with the B-myb transcription factor in S/G2. In this study, we addressed whether p130–DREAM is disrupted in HPV16-transformed cervical cancer cells and whether this is a critical function for E6/E7. We found that p130–DREAM was greatly diminished in HPV16-transformed cervical carcinoma cells (CaSki and SiHa) compared with control cell lines; however, when E6/E7 expression was targeted by specific small hairpin RNAs, p130–DREAM was reformed and the cell cycle was arrested. We further demonstrated that the profound G1 arrest in E7-depleted CaSki cells was dependent on p130–DREAM reformation by also targeting the expression of the DREAM component Lin-54 and p130. The results show that continued HPV16 E6/E7 expression is necessary in cervical cancer cells to prevent cell-cycle arrest by a repressive p130–DREAM complex.
- Published
- 2011
279. Necdin-E2F4 interaction provides insulin-sensitizing effect after weight loss induced by gastric bypass surgery
- Author
-
Anna Spagnoli, Michael J. Muehlbauer, Alfonso Torquati, Zehra Pamuklar, and Jiegen Chen
- Subjects
Adult ,Male ,medicine.medical_specialty ,medicine.medical_treatment ,Gastric Bypass ,Adipose tissue ,Nerve Tissue Proteins ,E2F4 Transcription Factor ,Article ,chemistry.chemical_compound ,Insulin resistance ,Downregulation and upregulation ,Internal medicine ,Adipocyte ,Gene expression ,Weight Loss ,medicine ,Adipocytes ,Humans ,Prospective Studies ,E2F4 ,Cells, Cultured ,business.industry ,Insulin ,nutritional and metabolic diseases ,Nuclear Proteins ,Middle Aged ,medicine.disease ,Surgery ,Obesity, Morbid ,Endocrinology ,chemistry ,Case-Control Studies ,Female ,Signal transduction ,Insulin Resistance ,business - Abstract
Background The insulin-like growth factor-1 (IGF-1) signaling pathway promotes adipocyte differentiation and, therefore, insulin sensitivity by suppression of necdin expression, which represses peroxisome proliferator-activated receptor-gamma promoter activity by interaction with E2F4 in mouse adipocytes. The aim of the present study was to test the hypothesis that this pathway represents one of the mechanisms by which Roux-en- Y gastric bypass surgery (RYGB) induces resolution of insulin resistance. Methods Clinical samples were collected and the key biomarkers measured to test the hypothesis that the IGF-1 pathway represents 1 of the mechanisms by which RYGB induces resolution of insulin resistance in obese individuals. Results Free IGF-1 levels were significantly greater in the post-RYGB patients than in the pre-RYGB obese patients (2.55 ± 1.54 versus 1.32 ± .65 μg/L, P = .03) and similar to that in normal weight controls (2.54 ± 1.27 μg/L). Necdin and E2F4 gene expression in the adipose tissue was significantly downregulated after RYGB compared with obese and were similar to the levels observed in the controls. In mature human adipocytes cultured in vitro, treatment with des-IGF-1 induced downregulation of necdin and E2F4 gene expression in a dose-dependent manner ( P = .01). Conclusion After RYGB, the insulin/IGF-1 signaling pathway is activated and could account for the observed decrease in the expression of necdin, which represses peroxisome proliferator-activated receptor-gamma promoter activity by interaction with E2F4. This could represent one of the mechanisms that induce resolution of insulin resistance after RYGB.
- Published
- 2011
280. DYRK1A protein kinase promotes quiescence and senescence through DREAM complex assembly
- Author
-
Larisa Litovchick, Laurence Florens, Michael P. Washburn, Selene K. Swanson, and James A. DeCaprio
- Subjects
Cell growth ,Cell cycle ,Biology ,Cell biology ,Genetics ,DREAM complex ,Nuclear protein ,E2F ,Protein kinase A ,E2F4 ,Cell aging ,psychological phenomena and processes ,Developmental Biology ,Research Paper - Abstract
In the absence of growth signals, cells exit the cell cycle and enter into G0 or quiescence. Alternatively, cells enter senescence in response to inappropriate growth signals such as oncogene expression. The molecular mechanisms required for cell cycle exit into quiescence or senescence are poorly understood. The DREAM (DP, RB [retinoblastoma], E2F, and MuvB) complex represses cell cycle-dependent genes during quiescence. DREAM contains p130, E2F4, DP1, and a stable core complex of five MuvB-like proteins: LIN9, LIN37, LIN52, LIN54, and RBBP4. In mammalian cells, the MuvB core dissociates from p130 upon entry into the cell cycle and binds to BMYB during S phase to activate the transcription of genes expressed late in the cell cycle. We used mass spectroscopic analysis to identify phosphorylation sites that regulate the switch of the MuvB core from BMYB to DREAM. Here we report that DYRK1A can specifically phosphorylate LIN52 on serine residue 28, and that this phosphorylation is required for DREAM assembly. Inhibiting DYRK1A activity or point mutation of LIN52 disrupts DREAM assembly and reduces the ability of cells to enter quiescence or undergo Ras-induced senescence. These data reveal an important role for DYRK1A in the regulation of DREAM activity and entry into quiescence.
- Published
- 2011
281. Loss of E2F7 expression is an early event in squamous differentiation and causes derepression of the key differentiation activator Sp1
- Author
-
Alison L. Dahler, Mehlika Hazar-Rethinam, Danny Rickwood, Liliana Endo-Munoz, Nicholas A. Saunders, S. Cameron, and Louise Smith
- Subjects
Keratinocytes ,Sp1 Transcription Factor ,Squamous Differentiation ,Dermatology ,Biology ,Biochemistry ,Gene Expression Regulation, Enzymologic ,Small hairpin RNA ,03 medical and health sciences ,0302 clinical medicine ,E2F7 Transcription Factor ,Transcription (biology) ,E2F1 ,Humans ,Promoter Regions, Genetic ,Molecular Biology ,E2F4 ,Transcription factor ,Derepression ,Cells, Cultured ,030304 developmental biology ,0303 health sciences ,Gene knockdown ,Transglutaminases ,Cell Differentiation ,Cell Biology ,Molecular biology ,030220 oncology & carcinogenesis - Abstract
Squamous differentiation is controlled by key transcription factors such as Sp1 and E2F. We have previously shown that E2F1 can suppress transcription of the differentiation-specific gene, transglutaminase type 1 (TG1), by an indirect mechanism mediated by Sp1. Transient transfection of E2F1-E2F6 indicated that E2F-mediated reduction of Sp1 transcription was not responsible for E2F-mediated suppression of squamous differentiation. However, we found that E2F4 and E2F7, but not E2Fs 1, 2, 3, 5, or 6, could suppress the activation of the Sp1 promoter in differentiated keratinocytes (KCs). E2F4-mediated suppression could not be antagonized by E2Fs 1, 2, 3, 5, or 6 and was localized to a region of the human Sp1 promoter spanning -139 to + 35 bp. Chromatin immunoprecipitation analysis, as well as transient overexpression and short hairpin RNA knockdown experiments indicate that E2F7 binds to a unique binding site located between -139 and -119 bp of the Sp1 promoter, and knockdown of E2F7 in proliferating KCs leads to a derepression of Sp1 expression and the induction of TG1. In contrast, E2F4 knockdown in proliferating KCs did not alter Sp1 expression. These data indicate that loss of E2F7 during the initiation of differentiation leads to the derepression of Sp1 and subsequent transcription of differentiation-specific genes such as TG1.
- Published
- 2011
282. The CHR promoter element controls cell cycle-dependent gene transcription and binds the DREAM and MMB complexes
- Author
-
Eberhard Krause, Martin Fischer, Megha Padi, Michael Schümann, Gerd A. Müller, Marianne Quaas, Larisa Litovchick, Kurt Engeland, and James A. DeCaprio
- Subjects
Transcriptional Activation ,Transcription, Genetic ,Gene Regulation, Chromatin and Epigenetics ,Biology ,Cell Line ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Genetics ,Transcriptional regulation ,Animals ,Humans ,DREAM complex ,Cyclin B2 ,Promoter Regions, Genetic ,Transcription factor ,E2F4 ,Conserved Sequence ,Phylogeny ,030304 developmental biology ,Regulation of gene expression ,0303 health sciences ,Cyclin-dependent kinase 1 ,Binding Sites ,Base Sequence ,Promoter ,Molecular biology ,Cell Cycle Gene ,Genes, cdc ,Gene Expression Regulation ,030220 oncology & carcinogenesis ,Ubiquitin-Conjugating Enzymes ,NIH 3T3 Cells ,Transcription Factors - Abstract
Cell cycle-dependent gene expression is often controlled on the transcriptional level. Genes like cyclin B, CDC2 and CDC25C are regulated by cell cycle-dependent element (CDE) and cell cycle genes homology region (CHR) promoter elements mainly through repression in G(0)/G(1). It had been suggested that E2F4 binding to CDE sites is central to transcriptional regulation. However, some promoters are only controlled by a CHR. We identify the DREAM complex binding to the CHR of mouse and human cyclin B2 promoters in G(0). Association of DREAM and cell cycle-dependent regulation is abrogated when the CHR is mutated. Although E2f4 is part of the complex, a CDE is not essential but can enhance binding of DREAM. We show that the CHR element is not only necessary for repression of gene transcription in G(0)/G(1), but also for activation in S, G(2) and M phases. In proliferating cells, the B-myb-containing MMB complex binds the CHR of both promoters independently of the CDE. Bioinformatic analyses identify many genes which contain conserved CHR elements in promoters binding the DREAM complex. With Ube2c as an example from that screen, we show that inverse CHR sites are functional promoter elements that can bind DREAM and MMB. Our findings indicate that the CHR is central to DREAM/MMB-dependent transcriptional control during the cell cycle.
- Published
- 2011
283. Genome-Wide Profiling of H3K56 Acetylation and Transcription Factor Binding Sites in Human Adipocytes
- Author
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Mary K. Bauchmann, Mark A. Thiede, Christopher J. Donahue, Amy P. Baumann, Kinyui Alice Lo, Shelley G. des Etages, Ernest Fraenkel, Lisa S. Hayes, Massachusetts Institute of Technology. Department of Biological Engineering, Fraenkel, Ernest, and Lo, Kinyui Alice
- Subjects
lcsh:Medicine ,Histones ,Mesoderm ,Mice ,0302 clinical medicine ,Heat Shock Transcription Factors ,Sirtuin 1 ,Transcriptional regulation ,Adipocytes ,lcsh:Science ,E2F4 ,Cells, Cultured ,Genetics ,0303 health sciences ,Multidisciplinary ,Ccaat-enhancer-binding proteins ,Chromosome Biology ,Acetylation ,Cell Differentiation ,Genomics ,CREB-Binding Protein ,Chromatin ,3. Good health ,Cell biology ,Functional Genomics ,DNA-Binding Proteins ,Medicine ,Research Article ,E2F4 Transcription Factor ,Biology ,DNA-binding protein ,03 medical and health sciences ,3T3-L1 Cells ,CCAAT-Enhancer-Binding Protein-alpha ,Animals ,Humans ,E2F ,Transcription factor ,030304 developmental biology ,Binding Sites ,Base Sequence ,Genome, Human ,Gene Expression Profiling ,Lysine ,lcsh:R ,DNA binding site ,Metabolic Disorders ,lcsh:Q ,Chromatin immunoprecipitation ,E1A-Associated p300 Protein ,030217 neurology & neurosurgery ,Transcription Factors - Abstract
The growing epidemic of obesity and metabolic diseases calls for a better understanding of adipocyte biology. The regulation of transcription in adipocytes is particularly important, as it is a target for several therapeutic approaches. Transcriptional outcomes are influenced by both histone modifications and transcription factor binding. Although the epigenetic states and binding sites of several important transcription factors have been profiled in the mouse 3T3-L1 cell line, such data are lacking in human adipocytes. In this study, we identified H3K56 acetylation sites in human adipocytes derived from mesenchymal stem cells. H3K56 is acetylated by CBP and p300, and deacetylated by SIRT1, all are proteins with important roles in diabetes and insulin signaling. We found that while almost half of the genome shows signs of H3K56 acetylation, the highest level of H3K56 acetylation is associated with transcription factors and proteins in the adipokine signaling and Type II Diabetes pathways. In order to discover the transcription factors that recruit acetyltransferases and deacetylases to sites of H3K56 acetylation, we analyzed DNA sequences near H3K56 acetylated regions and found that the E2F recognition sequence was enriched. Using chromatin immunoprecipitation followed by high-throughput sequencing, we confirmed that genes bound by E2F4, as well as those by HSF-1 and C/EBPα, have higher than expected levels of H3K56 acetylation, and that the transcription factor binding sites and acetylation sites are often adjacent but rarely overlap. We also discovered a significant difference between bound targets of C/EBPα in 3T3-L1 and human adipocytes, highlighting the need to construct species-specific epigenetic and transcription factor binding site maps. This is the first genome-wide profile of H3K56 acetylation, E2F4, C/EBPα and HSF-1 binding in human adipocytes, and will serve as an important resource for better understanding adipocyte transcriptional regulation., Singapore. Agency for Science, Technology and Research (National Science Scholarship ), Massachusetts Institute of Technology (Eugene Bell Career Development Chair), National Science Foundation (U.S.) (Award No. DBI-0821391), Pfizer Inc.
- Published
- 2010
284. Redox-dependent Brca1 transcriptional regulation by an NADH-sensor CtBP1
- Author
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Su-Yan Wang, Qinghong Zhang, Yu Deng, Shi-Long Lu, Xiao-Jing Wang, Chu-Xia Deng, Stephen P. Malkoski, Jing Liu, Gangwen Han, and Aik Choon Tan
- Subjects
Cancer Research ,DNA Repair ,Transcription, Genetic ,DNA repair ,Down-Regulation ,E2F4 Transcription Factor ,Biology ,medicine.disease_cause ,Article ,Cyclic N-Oxides ,CTBP1 ,Downregulation and upregulation ,Genetics ,medicine ,Transcriptional regulation ,Humans ,skin and connective tissue diseases ,Promoter Regions, Genetic ,Molecular Biology ,E2F4 ,Regulation of gene expression ,BRCA1 Protein ,NAD ,DNA-Binding Proteins ,Gene Expression Regulation, Neoplastic ,Alcohol Oxidoreductases ,Head and Neck Neoplasms ,Cancer research ,Carcinoma, Squamous Cell ,Spin Labels ,Carcinogenesis ,Oxidation-Reduction ,Immunostaining - Abstract
Carboxyl-terminal binding protein 1 (CtBP1) is a transcriptional co-repressor and metabolic sensory protein, which often represses tumor suppressor genes. Hence, we sought to determine if CtBP1 affects expression of the tumor suppressor Brca1 in head and neck tissue, as down-regulation of Brca1 begins at the early stages of head and neck squamous cell carcinomas (HNSCCs). We found that CtBP1 represses Brca1 transcription by binding to the E2F4 site of the Brca1 promoter. Additionally, the recruitment of CtBP1 to the Brca1 promoter is redox-dependent, i.e., increased at high NADH levels in hypoxic conditions. Further, immunostaining using a human HNSCC tissue array revealed that nuclear CtBP1 staining began to accumulate in hyperplasic lesions and HNSCCs, this staining correlated with Brca1 down-regulation in these lesions. Pharmacological disruption of CtBP1 binding to Brca1 promoter by the antioxidant Tempol, which reduces NADH levels, relieved CtBP1-mediated repression of Brca1, leading to increased DNA repair in HNSCC cells. Since tumor cells are generally hypoxic with increased NADH levels, the dynamic control of Brca1 by a "metabolic switch" found in this study not only provides an important link between tumor metabolism and tumor suppressor expression, but also suggests a potential chemo preventative or therapeutic strategy for HNSCC via blocking NADH-dependent CtBP1 activity at early stages of HNSCC carcinogenesis.
- Published
- 2010
285. RB·E2F1 complex mediates DNA damage responses through transcriptional regulation of ZBRK1
- Author
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Wen Chang Chang, Connie Y. Tsai, Ching Chun Liao, Ju Ming Wang, and Wen-Hwa Lee
- Subjects
Transcription, Genetic ,DNA repair ,DNA damage ,Ultraviolet Rays ,Repressor ,Cell Cycle Proteins ,Biology ,Response Elements ,Biochemistry ,Retinoblastoma Protein ,Chromatin remodeling ,Cell Line, Tumor ,Transcriptional regulation ,E2F1 ,Humans ,Gene Regulation ,Molecular Biology ,E2F4 ,Mesylates ,Endodeoxyribonucleases ,Cell Cycle ,Nuclear Proteins ,E2F1 Transcription Factor ,Cell Biology ,Chromatin Assembly and Disassembly ,Molecular biology ,Repressor Proteins ,Multiprotein Complexes ,Carrier Proteins ,DNA Damage - Abstract
RB plays an essential role in DNA damage-induced growth arrest and regulates the expression of several factors essential for DNA repair machinery. However, how RB coordinates DNA damage response through transcriptional regulation of genes involved in growth arrest remains largely unexplored. We examined whether RB can mediate the response to DNA damage through modulation of ZBRK1, a zinc finger-containing transcriptional repressor that can modulate the expression of GADD45A, a DNA damage response gene, to induce cell cycle arrest in response to DNA damage. We found that the ZBRK1 promoter contains an authentic E2F-recognition sequence that specifically binds E2F1, but not E2F4 or E2F6, together with chromatin remodeling proteins CtIP and CtBP to form a repression complex that suppresses ZBRK1 transcription. Furthermore, loss of RB-mediated transcriptional repression led to an increase in ZBRK1 transcript levels, correlating with increased sensitivity to ultraviolet (UV) and methyl methanesulfonate-induced DNA damage. Taken together, these results suggest that the RB·CtIP (CtBP interacting protein)/CtBP (C terminus-binding protein) /E2F1 complex plays a critical role in ZBRK1 transcriptional repression, and loss of this repression may contribute to cellular sensitivity of DNA damage, ultimately leading to carcinogenesis.
- Published
- 2010
286. Capsaicin displays anti-proliferative activity against human small cell lung cancer in cell culture and nude mice models via the E2F pathway
- Author
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Yi C. Chen, Kathleen C. Brown, A. Betts Carpenter, Haitao Luo, Theodore R. Witte, W. Elaine Hardman, Piyali Dasgupta, and Jamie K. Lau
- Subjects
CDC25A ,Cyclin E ,Cell Biology/Cell Growth and Division ,Mice, Nude ,lcsh:Medicine ,Antineoplastic Agents ,E2F4 Transcription Factor ,Biology ,Response Elements ,Cell Biology/Cell Signaling ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,In vivo ,Tumor Cells, Cultured ,Animals ,Humans ,E2F ,lcsh:Science ,E2F4 ,Oncology/Lung Cancer ,030304 developmental biology ,0303 health sciences ,Multidisciplinary ,Cell growth ,lcsh:R ,Small Cell Lung Carcinoma ,Xenograft Model Antitumor Assays ,Molecular biology ,E2F Transcription Factors ,3. Good health ,Gene Expression Regulation ,chemistry ,Capsaicin ,Cell culture ,030220 oncology & carcinogenesis ,Cancer research ,lipids (amino acids, peptides, and proteins) ,lcsh:Q ,Research Article - Abstract
Background Small cell lung cancer (SCLC) is characterized by rapid progression and low survival rates. Therefore, novel therapeutic agents are urgently needed for this disease. Capsaicin, the active ingredient of chilli peppers, displays anti-proliferative activity in prostate and epidermoid cancer in vitro. However, the anti-proliferative activity of capsaicin has not been studied in human SCLCs. The present manuscript fills this void of knowledge and explores the anti-proliferative effect of capsaicin in SCLC in vitro and in vivo. Methodology/Principal Findings BrdU assays and PCNA ELISAs showed that capsaicin displays robust anti-proliferative activity in four human SCLC cell lines. Furthermore, capsaicin potently suppressed the growth of H69 human SCLC tumors in vivo as ascertained by CAM assays and nude mice models. The second part of our study attempted to provide insight into molecular mechanisms underlying the anti-proliferative activity of capsaicin. We found that the anti-proliferative activity of capsaicin is correlated with a decrease in the expression of E2F-responsive proliferative genes like cyclin E, thymidylate synthase, cdc25A and cdc6, both at mRNA and protein levels. The transcription factor E2F4 mediated the anti-proliferative activity of capsaicin. Ablation of E2F4 levels by siRNA methodology suppressed capsaicin-induced G1 arrest. ChIP assays demonstrated that capsaicin caused the recruitment of E2F4 and p130 on E2F-responsive proliferative promoters, thereby inhibiting cell proliferation. Conclusions/Significance Our findings suggest that the anti-proliferative effects of capsaicin could be useful in the therapy of human SCLCs.
- Published
- 2010
287. Capsaicin displays anti‐proliferative activity of human small cell lung cancer via recruitment of E2F4 to downstream target genes
- Author
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Piyali Dasgupta, W. Elaine Hardman, Haitao Luo, Ted R. Witte, Yi C. Chen, and Kathleen C. Brown
- Subjects
chemistry.chemical_compound ,chemistry ,Downstream (manufacturing) ,Capsaicin ,Genetics ,Cancer research ,Non small cell ,Anti proliferative ,Molecular Biology ,Biochemistry ,Gene ,E2F4 ,Biotechnology - Published
- 2010
288. pRB and E2F4 play distinct cell-intrinsic roles in fetal erythropoiesis
- Author
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Jacqueline A. Lees, Yangang Liu, Jing Zhang, Eunice Y. Lee, Seth D. Berman, and Harvey F. Lodish
- Subjects
Cell Survival ,Cellular differentiation ,Cell ,Apoptosis ,Mice, Transgenic ,E2F4 Transcription Factor ,Biology ,Retinoblastoma Protein ,Article ,Gene Knockout Techniques ,Mice ,Fetus ,Erythroid Cells ,medicine ,Animals ,Erythropoiesis ,Molecular Biology ,E2F4 ,Retinoblastoma ,Macrophages ,Retinoblastoma protein ,Cell Differentiation ,Cell Biology ,Cell cycle ,medicine.disease ,Embryo, Mammalian ,medicine.anatomical_structure ,biology.protein ,Cancer research ,E2F Transcription Factors ,Developmental Biology - Abstract
The retinoblastoma tumor suppressor protein pRB functions, at least in part, by directly binding to and modulating the activity of the E2F transcription factors. Previous studies have shown that both E2F4 and pRB play important roles in fetal erythropoiesis. Given that these two proteins interact directly we investigated the overlap of E2F4 and pRB function in this process by analyzing E2f4(-/-), conditional Rb knockout (Rb(1lox/1lox)), and compound E2f4(-/-);Rb(1lox/1lox) embryos. At E15.5 E2f4(-/-) and Rb(1lox/1lox) fetal erythroid cells display distinct abnormalities in their differentiation profiles. When cultured in vitro, both E2f4(-/-) and Rb(1lox/1lox) erythroid cells show defects in cell cycle progression. Surprisingly, analysis of cell cycle profiling suggests that E2F4 and pRB control cell cycle exit through different mechanisms. Moreover, only pRB, but not E2F4, promotes cell survival in erythroid cells. We observed an additive rather than a synergistic impact upon the erythroid defects in the compound E2f4(-/-);Rb(1lox/1lox) embryos. We further found that fetal liver macrophage development is largely normal regardless of genotype. Taken together, our results show that E2F4 and pRB play independent cell-intrinsic roles in fetal erythropoiesis.
- Published
- 2009
289. Tumor suppression by ARF: gatekeeper and caretaker
- Author
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Yi Ju Chen, Julia Pimkina, Carmen Dominguez-Brauer, Pradip Raychaudhuri, and Patrick M. Brauer
- Subjects
Cell cycle checkpoint ,biology ,Activator (genetics) ,DNA repair ,Repressor ,Cell Biology ,Models, Biological ,Cell biology ,E2F Transcription Factors ,Neoplasms ,biology.protein ,Cancer research ,Mdm2 ,Animals ,Humans ,biological phenomena, cell phenomena, and immunity ,Tumor Suppressor Protein p53 ,E2F ,Molecular Biology ,Transcription factor ,E2F4 ,Cyclin-Dependent Kinase Inhibitor p16 ,Developmental Biology ,Protein Binding ,Signal Transduction - Abstract
ARF is a vital tumor suppressor and its loss contributes significantly to cancer. The frequency in which ARF is mutated, deleted or silenced is second to the loss of p53. The most documented and widely accepted activity of ARF is mediated through its activation of the p53 transcriptional program by inhibiting MDM2 function. However, several lines of evidence have surfaced demonstrating that ARF possesses p53-independent functions. One of these p53-independent functions is ARF's regulation of the E2F family. The E2F/DP transcription factor is critical for cell cycle progression. The balance between activator and repressor E2Fs regulates the expression of E2F target genes and thus cell proliferation as well as other cellular functions such as checkpoint, chromosome assembly and repair. Through its ability to bind directly to DP1, ARF can cause dissociation of both activator and repressor E2Fs. While the regulation of the activator E2Fs is related to cell cycle arrest, there is evidence that the regulation of the repressors, E2F4 and E2F5, is significant in maintaining genomic stability.
- Published
- 2009
290. E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin
- Author
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Roderick H. Dashwood, Korakod Chimploy, George S. Bailey, Wan Mohaiza Dashwood, Qingjie Li, Christopher K. Mathews, Orianna Carter, David E. Williams, and G. Darío Díaz
- Subjects
Cancer Research ,Colorectal cancer ,E2F4 Transcription Factor ,Biology ,Article ,S Phase ,chemistry.chemical_compound ,Cell Line, Tumor ,Ribonucleotide Reductases ,medicine ,Anticarcinogenic Agents ,Humans ,E2F4 ,DNA synthesis ,Chlorophyllides ,Chlorophyllin ,Cancer ,DNA ,Cell cycle ,medicine.disease ,Molecular biology ,Ribonucleotide reductase ,Oncology ,chemistry ,Cell culture ,Colonic Neoplasms ,Cancer research ,Tumor Suppressor Protein p53 ,E2F1 Transcription Factor - Abstract
Chlorophyllin (CHL) is a water-soluble derivative of chlorophyll that exhibits cancer chemopreventive properties, but which also has been studied for its possible cancer therapeutic effects. We report here that human colon cancer cells treated with CHL accumulate in S-phase of the cell cycle, and this is associated with reduced expression levels of p53, p21, and other G(1)/S checkpoint controls. At the same time, E2F1 and E2F4 transcription factors become elevated and exhibit increased DNA binding activity. In CHL-treated colon cancer cells, bromodeoxyuridine pulse-chase experiments provided evidence for the inhibition of DNA synthesis. Ribonucleotide reductase (RR), a pivotal enzyme for DNA synthesis and repair, was reduced at the mRNA and protein level after CHL treatment, and the enzymatic activity was inhibited in a concentration-dependent manner both in vitro and in vivo. Immunoblotting revealed that expression levels of RR subunits R1, R2, and p53R2 were reduced by CHL treatment in HCT116 (p53(+/+)) and HCT116 (p53(-/-)) cells, supporting a p53-independent mechanism. Prior studies have shown that reduced levels of RR small subunits can increase the sensitivity of colon cancer cells to clinically used DNA-damaging agents and RR inhibitors. We conclude that by inhibiting R1, R2, and p53R2, CHL has the potential to be effective in the clinical setting, when used alone or in combination with currently available cancer therapeutic agents.
- Published
- 2009
291. A Role for E2F Activities in Determining the Fate of Myc-Induced Lymphomagenesis
- Author
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Seiichi Mori, Rachel E. Rempel, Eran R. Andrechek, Maura Gasparetto, Clay Smith, Anand S. Lagoo, Joseph R. Nevins, Michele A. Glozak, Steven B. Adler, Nina Laakso, and Robert W. Storms
- Subjects
Male ,Cancer Research ,Lineage (genetic) ,Lymphoma, B-Cell ,lcsh:QH426-470 ,E2F4 Transcription Factor ,Biology ,medicine.disease_cause ,Proto-Oncogene Proteins c-myc ,03 medical and health sciences ,Mice ,0302 clinical medicine ,E2F2 Transcription Factor ,Genetics ,medicine ,E2F1 ,Animals ,Humans ,B-cell lymphoma ,E2F ,Molecular Biology ,E2F4 ,Genetics and Genomics/Cancer Genetics ,Genetics (clinical) ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology ,E2F2 ,Mice, Knockout ,0303 health sciences ,Genetic heterogeneity ,Genetics and Genomics/Gene Expression ,medicine.disease ,Gene Expression Regulation, Neoplastic ,Mice, Inbred C57BL ,lcsh:Genetics ,Disease Models, Animal ,Genetics and Genomics/Disease Models ,E2F3 Transcription Factor ,030220 oncology & carcinogenesis ,Cancer research ,Female ,Carcinogenesis ,E2F1 Transcription Factor ,Research Article - Abstract
The phenotypic heterogeneity that characterizes human cancers reflects the enormous genetic complexity of the oncogenic process. This complexity can also be seen in mouse models where it is frequently observed that in addition to the initiating genetic alteration, the resulting tumor harbors additional, somatically acquired mutations that affect the tumor phenotype. To investigate the role of genetic interactions in the development of tumors, we have made use of the Eμ-myc model of pre-B and B cell lymphoma. Since various studies point to a functional interaction between Myc and the Rb/E2F pathway, we have investigated the role of E2F activities in the process of Myc-induced lymphomagenesis. Whereas the absence of E2F1 and E2F3 function has no impact on Myc-mediated tumor development, the absence of E2F2 substantially accelerates the time of tumor onset. Conversely, tumor development is delayed by the absence of E2F4. The enhanced early onset of tumors seen in the absence of E2F2 coincides with an expansion of immature B lineage cells that are likely to be the target for Myc oncogenesis. In contrast, the absence of E2F4 mutes the response of the lineage to Myc and there is no expansion of immature B lineage cells. We also find that distinct types of tumors emerge from the Eμ-myc mice, distinguished by different patterns of gene expression, and that the relative proportions of these tumor types are affected by the absence of either E2F2 or E2F4. From these results, we conclude that there are several populations of tumors that arise from the Eμ-myc model, reflecting distinct populations of cells that are susceptible to Myc-mediated oncogenesis and that the proportion of these cell populations is affected by the presence or absence of E2F activities., Author Summary The diversity of human cancers reflects the variety of genetic changes that cause tumors to emerge and progress. Even for mice engineered with a specific cancer-causing mutation, the resulting tumors are often divergent, reflecting different additional mutations. We wanted to investigate how activities that work together can collaborate in tumorigenesis. Specifically, we are interested in Myc and the E2F family of proteins, intersecting activities that influence a cell's decision to replicate, rest, or die. We made use of an engineered mouse that develops pre-B and B cell lymphoma initiated by Myc and tested whether the loss of particular E2F family members influences these lymphomas. We found that tumor emergence was accelerated by E2F2 loss and delayed by E2F4 loss. We attributed these results to the finding that the mice lacking E2F2 have a greater proportion than usual of the most susceptible, early-stage B lineage cells and the mice lacking E2F4 have fewer of these cells. Distinct tumor types emerged with their relative proportions influenced by E2F2 and E2F4 status. We conclude that the variety of tumors probably reflect different stages of B lymphoid development that respond to Myc and that E2F proteins can influence the proportions of these different stages.
- Published
- 2009
292. E2F4 expression is required for cell cycle progression of normal intestinal crypt cells and colorectal cancer cells
- Author
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Hugo Garneau, Nathalie Rivard, Marie-Christine Paquin, and Julie C. Carrier
- Subjects
Physiology ,Clinical Biochemistry ,Cyclin A ,Down-Regulation ,E2F4 Transcription Factor ,Mouse model of colorectal and intestinal cancer ,S Phase ,Cell Line, Tumor ,Humans ,Intestinal Mucosa ,E2F4 ,Cyclin ,Cell Proliferation ,Regulation of gene expression ,Cell Nucleus ,biology ,Cell growth ,Cell Cycle ,G1 Phase ,Epithelial Cells ,Cell Biology ,DNA ,Cell cycle ,Cell biology ,Gene Expression Regulation, Neoplastic ,Intestines ,Agar ,Protein Transport ,Cell culture ,Gene Knockdown Techniques ,Cancer research ,biology.protein ,Colorectal Neoplasms - Abstract
The generation of knock-out mice for E2F4 gene expression has suggested a role for this transcription factor in establishing and/or maintaining the intestinal crypt compartment. Having previously demonstrated that E2F4 is cytoplasmic in quiescent-differentiated cells but nuclear in growth factor-stimulated proliferative cells, the present study was aimed at determining the role of E2F4 in the control of human intestinal epithelial proliferation. Results herein demonstrate that lentiviral infection of an shRNA which specifically knocked-down E2F4 expression slowed down G1/S phase transition and the proliferation rate of normal human intestinal epithelial cells (HIEC) and of colon cancer cells. Protein expression of Cdk2, cyclins D1 and A, Cdc25A and c-myc was markedly down-regulated in shE2F4-expressing cells; by contrast, expression of the cell cycle inhibitors p21(Cip/Waf) and p27(Kip1) was increased. In addition, the expression of many genes involved in DNA synthesis was down-regulated in shE2F4-expressing cells, whereas no modulation in E2F1 expression was observed. A decrease in E2F4 in colon cancer cell lines also resulted in a reduction in soft-agar growth capacity. Immunofluorescence experiments in human fetal intestine revealed that cells expressing high nuclear levels of E2F4 also expressed cyclin A protein. Lastly, E2F4 and its target cyclin A were up-regulated and mostly nuclear in human colorectal tumor cells in comparison to the corresponding benign epithelium. These results indicate that nuclear E2F4 may be determinant in the promotion of proliferation of human intestinal epithelial crypt cells and colorectal cancer cells.
- Published
- 2009
293. EKLF/KLF1 controls cell cycle entry via direct regulation of E2f2
- Author
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Janelle R. Keys, Patrick O. Humbert, Andrew C. Perkins, and Michael R. Tallack
- Subjects
Molecular Sequence Data ,Kruppel-Like Transcription Factors ,KLF1 ,E2F4 Transcription Factor ,Biochemistry ,Retinoblastoma Protein ,S Phase ,Mice ,E2F2 Transcription Factor ,Erythroid Cells ,Animals ,Erythropoiesis ,Transcription, Chromatin, and Epigenetics ,RNA, Messenger ,Enhancer ,Molecular Biology ,Transcription factor ,E2F4 ,Conserved Sequence ,Binding Sites ,biology ,Base Sequence ,Cell growth ,Cell Cycle ,Retinoblastoma protein ,Cell Biology ,Cell cycle ,Molecular biology ,Introns ,Cell biology ,Enhancer Elements, Genetic ,Gene Expression Regulation ,biology.protein ,Gene Deletion ,Transcription Factors - Abstract
Differentiation of erythroid cells requires precise control over the cell cycle to regulate the balance between cell proliferation and differentiation. The zinc finger transcription factor, erythroid Krüppel-like factor (EKLF/KLF1), is essential for proper erythroid cell differentiation and regulates many erythroid genes. Here we show that loss of EKLF leads to aberrant entry into S-phase of the cell cycle during both primitive and definitive erythropoiesis. This cell cycle defect was associated with a significant reduction in the expression levels of E2f2 and E2f4, key factors necessary for the induction of S-phase gene expression and erythropoiesis. We found and validated novel intronic enhancers in both the E2f2 and E2f4 genes, which contain conserved CACC, GATA, and E-BOX elements. The E2f2 enhancer was occupied by EKLF in vivo. Furthermore, we were able to partially restore cell cycle dynamics in EKLF(-/-) fetal liver upon additional genetic depletion of Rb, establishing a genetic causal link between reduced E2f2 and the EKLF cell cycle defect. Finally, we propose direct regulation of the E2f2 enhancer is a generic mechanism by which many KLFs regulate proliferation and differentiation.
- Published
- 2009
294. A Lin-9 complex is recruited by B-Myb to activate transcription of G2/M genes in undifferentiated embryonal carcinoma cells
- Author
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Roger J. Watson, A S Knight, and M Notaridou
- Subjects
G2 Phase ,Transcriptional Activation ,Cancer Research ,Chromatin Immunoprecipitation ,Embryonal Carcinoma Stem Cells ,LINC complex ,Survivin ,Cyclin B ,Cell Cycle Proteins ,Inhibitor of Apoptosis Proteins ,Mice ,Genetics ,Animals ,DREAM complex ,Cyclin B1 ,Promoter Regions, Genetic ,Molecular Biology ,Transcription factor ,Mitosis ,E2F4 ,Binding Sites ,biology ,Tumor Suppressor Proteins ,fungi ,Cell biology ,E2F Transcription Factors ,Repressor Proteins ,biology.protein ,Trans-Activators ,Microtubule-Associated Proteins ,Cell Division - Abstract
It has recently been discovered that cell-cycle gene transcription is regulated by a core complex named LINC that switches from a transcriptionally repressive complex in G(0)-G(1) with the p130 or p107 pocket proteins and E2F4 to a transcriptionally active complex in S-G(2) containing B-Myb. We have studied the function of LINC in F9 embryonal carcinoma cells, which are distinguished by a rapid cell cycle resulting from an extremely short G(1) phase. We show that suppressing expression of the LINC component, Lin-9, in F9 cells causes arrest in mitosis, and we have used this system to screen for transcriptional targets. In these cells, B-Myb was found in complexes with Lin-9 and several other LINC constituents, however, the pocket proteins did not associate with LINC unless F9 cells were differentiated. Lin-9 and B-Myb were both required for transcription of G(2)/M genes such as Cyclin B1 and Survivin. Moreover, B-Myb was demonstrated to recruit Lin-9 to the Survivin promoter through multiple Myb-binding sites. The demonstration that a B-Myb/LINC complex is vital for progression through mitosis in cells lacking a G(1)/S checkpoint has implications for both undifferentiated embryonal cells and for cancers in which pocket protein function is compromised.
- Published
- 2009
295. Thyroid hormone – triiodothyronine – has contrary effect on proliferation of human proximal tubules cell line (HK2) and renal cancer cell lines (Caki-2, Caki-1) – role of E2F4, E2F5 and p107, p130
- Author
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Piotr Popławski and Alicja Nauman
- Subjects
medicine.medical_specialty ,Endocrinology, Diabetes and Metabolism ,lcsh:Diseases of the endocrine glands. Clinical endocrinology ,Endocrinology ,Internal medicine ,medicine ,E2F4 ,Cyclin ,Triiodothyronine ,lcsh:RC648-665 ,biology ,Endocrine and Autonomic Systems ,business.industry ,Research ,Cyclin-dependent kinase 2 ,medicine.disease ,Clear cell renal cell carcinoma ,Cell culture ,embryonic structures ,biology.protein ,Cancer research ,Signal transduction ,biological phenomena, cell phenomena, and immunity ,business ,Hormone - Abstract
Background Triiodothyronine regulates proliferation acting as stimulator or inhibitor. E2F4 and E2F5 in complexes with pocket proteins p107 or p130 stop cells in G1, repressing transcription of genes important for cell cycle progression. p107 and p130 inhibits activity of cyclin/cdk2 complexes. Expression of all those proteins could be regulated by triiodothyronine. In clear cell renal cell carcinoma many disturbances in T3 signaling pathway was described, in that type of cancer also expression of some key G1 to S phase progression regulators was shown. Methods We investigated role of T3 and its receptors in regulation of proliferation of HK2, Caki-2, Caki-1 cell lines (cell counting, cytometric analysis of DNA content) and expression of thyroid hormone receptors, E2F4, E2F5, p107 and p130 (western blot and semi-quantitative real time PCR). Statistical analysis was performed using one-way ANOVA. Results and Conclusion We show that T3 inhibits proliferation of HK2, and stimulates it in Caki lines. Those differences are result of disturbed expression of TR causing improper regulation of E2F4, E2F5, p107 and p130 in cancer cells.
- Published
- 2008
296. Rb/E2F4 and Smad2/3 link survivin to TGF-beta-induced apoptosis and tumor progression
- Author
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Mark W. Jackson, Tracy L. Krebs, Jiayi Yang, David Danielpour, and Kyung Song
- Subjects
Male ,Cancer Research ,Transcription, Genetic ,Survivin ,Blotting, Western ,Receptor, Transforming Growth Factor-beta Type I ,Repressor ,Apoptosis ,Electrophoretic Mobility Shift Assay ,E2F4 Transcription Factor ,Smad2 Protein ,Biology ,Protein Serine-Threonine Kinases ,medicine.disease_cause ,Response Elements ,Retinoblastoma Protein ,Article ,Inhibitor of Apoptosis Proteins ,Transforming Growth Factor beta ,Genetics ,medicine ,Tumor Cells, Cultured ,Gene silencing ,Humans ,Smad3 Protein ,E2F ,Promoter Regions, Genetic ,Molecular Biology ,E2F4 ,Reverse Transcriptase Polymerase Chain Reaction ,Prostatic Neoplasms ,Neoplasm Proteins ,Tumor progression ,Cancer research ,Carcinogenesis ,Microtubule-Associated Proteins ,Receptors, Transforming Growth Factor beta ,Transforming growth factor ,Protein Binding - Abstract
Survivin is a prosurvival protein overexpressed in many cancers through mechanisms that remain poorly explored, and is implicated in control of tumor progression and resistance to cancer chemotherapeutics. Here, we report a critical role for survivin in the induction of apoptosis by transforming growth factor-beta (TGF-beta). We show that TGF-beta rapidly downregulates survivin expression in prostate epithelial cells, through a unique mechanism of transcriptional suppression involving Smads 2 and 3, Rb/E2F4, and the cell-cycle repressor elements CDE and CHR. This TGF-beta response is triggered through a Smad2/3-dependent hypophosphorylation of Rb and the subsequent association of the Rb/E2F4 repressive complex to CDE/CHR elements in the proximal region of the survivin promoter. Viral-mediated gene delivery experiments, involving overexpressing or silencing survivin, reveal critical roles of survivin in apoptosis induced by TGF-beta alone or in cooperation with cancer therapeutic agents. We propose a novel TGF-beta/Rb/survivin axis with a putative role in the functional switch of TGF-beta from tumor suppressor to tumor promoter.
- Published
- 2008
297. Disruption of mutually negative regulatory feedback loop between interferon-inducible p202 protein and the E2F family of transcription factors in lupus-prone mice
- Author
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Hong Xin, Ravichandran Panchanathan, and Divaker Choubey
- Subjects
endocrine system ,Immunology ,E2F4 Transcription Factor ,Biology ,Retinoblastoma Protein ,Article ,Mice ,E2F2 Transcription Factor ,Immunology and Allergy ,E2F1 ,Animals ,Lupus Erythematosus, Systemic ,E2F ,Gene ,Transcription factor ,E2F4 ,E2F2 ,Regulation of gene expression ,Ifi202 ,Mice, Knockout ,Intracellular Signaling Peptides and Proteins ,Fibroblasts ,Embryo, Mammalian ,Phosphoproteins ,Molecular biology ,Disease Models, Animal ,Gene Expression Regulation ,NIH 3T3 Cells ,biological phenomena, cell phenomena, and immunity ,Tumor Suppressor Protein p53 ,Apoptosis Regulatory Proteins ,E2F1 Transcription Factor ,Spleen - Abstract
Studies have identified IFN-inducible Ifi202 gene as a lupus susceptibility gene (encoding p202 protein) in mouse models of lupus disease. However, signaling pathways that regulate the Ifi202 expression in cells remain to be elucidated. We found that steady-state levels of Ifi202 mRNA and protein were high in mouse embryonic fibroblasts (MEFs) from E2F1 knockout (E2F1−/−) and E2F1 and E2F2 double knockout (E2F1−/−E2F2−/−) mice than isogenic wild-type MEFs. Moreover, overexpression of E2F1 in mouse fibroblasts decreased expression of p202. Furthermore, expression of E2F1, but not E2F4, transcription factor in mouse fibroblasts repressed the activity of 202-luc-reporter in promoter-reporter assays. Interestingly, the E2F1-mediated transcriptional repression of the 202-luc-reporter was independent of p53 and pRb expression. However, the repression was dependent on the ability of E2F1 to bind DNA. We have identified a potential E2F DNA-binding site in the 5′-regulatory region of the Ifi202 gene, and mutations in this E2F DNA-binding site reduced the E2F1-mediated transcriptional repression of 202-luc-reporter. Because p202 inhibits the E2F1-mediated transcriptional activation of genes, we compared the expression of E2F1 and its target genes in splenic cells from lupus-prone B6.Nba2 congenic mice, which express increased levels of p202, with age-matched C57BL/6 mice. We found that increased expression of Ifi202 in the congenic mice was associated with inhibition of E2F1-mediated transcription and decreased expression of E2F1 and its target genes that encode proapoptotic proteins. Our observations support the idea that increased Ifi202 expression in certain strains of mice contributes to lupus susceptibility in part by inhibiting E2F1-mediated functions.
- Published
- 2008
298. E2F4 modulates differentiation and gene expression in hematopoietic progenitor cells during commitment to the lymphoid lineage
- Author
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Timothy P. Bushnell, Megan E. Enos, Simona Bancos, and Ian N. Crispe
- Subjects
Male ,Cellular differentiation ,Immunology ,Cell Cycle Proteins ,Mice, Transgenic ,Biology ,Cell fate determination ,Ikaros Transcription Factor ,Mice ,Fetus ,E2F2 Transcription Factor ,Immunology and Allergy ,Animals ,Cell Lineage ,Myeloid Cells ,Lymphocytes ,Progenitor cell ,E2F4 ,Interleukin 3 ,Regulation of gene expression ,Mice, Knockout ,Cell Differentiation ,Cell cycle ,Hematopoietic Stem Cells ,Mice, Inbred C57BL ,Haematopoiesis ,Gene Expression Regulation ,Liver ,Cancer research ,Female - Abstract
The E2F4 protein is involved in gene repression and cell cycle exit, and also has poorly understood effects in differentiation. We analyzed the impact of E2F4 deficiency on early steps in mouse hematopoietic development, and found defects in early hematopoietic progenitor cells that were propagated through common lymphoid precursors to the B and T lineages. In contrast, the defects in erythromyeloid precursor cells were self-correcting over time. This suggests that E2F4 is important in early stages of commitment to the lymphoid lineage. The E2F4-deficient progenitor cells showed reduced expression of several key lymphoid-lineage genes, and overexpression of two erythromyeloid lineage genes. However, we did not detect effects on cell proliferation. These findings emphasize the significance of E2F4 in controlling gene expression and cell fate.
- Published
- 2008
299. Comparative Analysis of E2F Family Member Oncogenic Activity
- Author
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Chunxia Chen and Andrew D. Wells
- Subjects
Cell division ,Blotting, Western ,Cell Biology/Cell Growth and Division ,lcsh:Medicine ,Biology ,DNA-binding protein ,Polymerase Chain Reaction ,Culture Media, Serum-Free ,Cell Line ,03 medical and health sciences ,Mice ,0302 clinical medicine ,E2F1 ,Animals ,Humans ,lcsh:Science ,E2F4 ,Transcription factor ,030304 developmental biology ,E2F2 ,DNA Primers ,Genetics ,0303 health sciences ,Multidisciplinary ,Base Sequence ,Cell growth ,lcsh:R ,3T3 Cells ,Oncogenes ,Flow Cytometry ,E2F Transcription Factors ,Oncology ,030220 oncology & carcinogenesis ,lcsh:Q ,Cell Division ,Research Article - Abstract
The E2F family of transcription factors consists of nine members with both distinct and overlapping functions. These factors are situated downstream of growth factor signaling cascades, where they play a central role in cell growth and proliferation through their ability to regulate genes involved in cell cycle progression. For this reason, it is likely that the members of the E2F family play a critical role during oncogenesis. Consistent with this idea is the observation that some tumors exhibit deregulated expression of E2F proteins. In order to systematically compare the oncogenic capacity of these family members, we stably over-expressed E2F1 through 6 in non-transformed 3T3 fibroblasts and assessed the ability of these transgenic cell lines to grow under conditions of low serum, as well as to form colonies in soft agar. Our results show that these six E2F family members can be divided into three groups that exhibit differential oncogenic capacity. The first group consists of E2F2 and E2F3a, both of which have strong oncogenic capacity. The second group consists of E2F1 and E2F6, which were neutral in our assays when compared to control cells transduced with vector alone. The third group consists of E2F4 and E2F5, which generally act to repress E2F-responsive genes, and in our assays demonstrated a strong capacity to inhibit transformation. Our results imply that the pattern of expression of these six E2F family members in a cell could exert a strong influence over its susceptibility to oncogenic transformation.
- Published
- 2007
300. The RAS-dependent ERF control of cell proliferation and differentiation is mediated by c-Myc repression
- Author
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George Mavrothalassitis, Elena Vorgia, Lionel Le Gallic, Chara Papadaki, and Mihalis Verykokakis
- Subjects
MAPK/ERK pathway ,Repressor ,E2F4 Transcription Factor ,Biology ,Cell fate determination ,Biochemistry ,Models, Biological ,Proto-Oncogene Proteins c-myc ,Mice ,Cell Line, Tumor ,Transcriptional regulation ,DNA-(Apurinic or Apyrimidinic Site) Lyase ,Animals ,Humans ,Extracellular Signal-Regulated MAP Kinases ,Molecular Biology ,E2F4 ,Cell Proliferation ,Mice, Knockout ,Effector ,Cell growth ,fungi ,food and beverages ,Cell Differentiation ,Cell Biology ,Fibroblasts ,Molecular biology ,Chromatin ,DNA-Binding Proteins ,Repressor Proteins ,ras Proteins ,Transcription Factors - Abstract
The ERF transcriptional repressor is a downstream effector of the RAS/ERK pathway that interacts with and is directly phosphorylated by ERKs in vivo and in vitro. This phosphorylation results in its cytoplasmic export and inactivation, although lack of ERK activity allows its immediate nuclear accumulation and repressor function. Nuclear ERFs arrest cell cycle progression in G(1) and can suppress ras-dependent tumorigenicity. Here we provide evidence that ERF function is mediated by its ability to repress transcription of c-Myc. Promoter reporter assays indicate a DNA binding-dependent and repressor domain-dependent Myc transcriptional repression. Chromatin immunoprecipitations in primary cells suggest that ERF specifically binds on the c-Myc promoter in an E2F4/5-dependent manner and only under conditions that the physiological c-Myc transcription is stopped. Cellular systems overexpressing nuclear ERF exhibit reduced c-Myc mRNA and tumorigenic potential. Elimination of Erf in animal models results in increased c-Myc expression, whereas Erf(-)(/)(-) primary fibroblasts fail to down-regulate Myc in response to growth factor withdrawal. Finally, elimination of c-Myc in primary mouse embryo fibroblasts negates the ability of nuclear ERF to suppress proliferation. Thus Erf provides a direct link between the RAS/ERK signaling and the transcriptional regulation of c-Myc and suggests that RAS/ERK attenuation actively regulates cell fate.
- Published
- 2007
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