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Introduction: Recent investigations suggest the potential negative impact of SARS-CoV-2 infection on pregnant women and pregnancy outcome. In addition, some studies have described pathological changes in the placental tissue of SARS-CoV-2-positive mothers, which are related or not to the infection severity and/or infection trimester. Among the various molecules involved in the normal structure and functionality of the placenta, sialic acids (Sias) seem to play an important role. Hence, we aimed to investigate possible changes in the distribution and content of Sias with different glycosidic linkages, namely alpha 2,3 and alpha 2,6 Galactose- or N-acetyl-Galactosamine-linked Sias and polymeric Sia (PolySia), in placentas from pregnant women infected by SARS-CoV-2 during the three different pregnancy trimesters. Methods: alpha 2,3 and alpha 2,6 Galactose-linked Sias were evaluated by lectin histochemistry (Maackia amurensis agglutinin (MAA) and Sambucus nigra agglutinin (SNA), respectively), while immunohistochemistry was used for PolySia detection. Results: Data showed lower levels of alpha 2,3 Galactose-linked Sias in the trophoblast and underlying basement membrane/basal plasma membrane in placentas from women infected during the second and third infection trimester compared with uninfected cases and those infected during first trimester. On the other hand, higher levels of PolySia were detected in the trophoblast during the second and third infection trimester. Conclusions: Our findings suggest that changes in the sialylation status of trophoblast and its basement membrane/basal plasma membrane, together with other concomitant factors, could be at the basis of the most common placental histopathological alterations and gestational complications found especially in pregnancies with SARS-CoV-2 infection during the second and third trimester.

Helicobacter pylori infects 50% of mankind. The vast majority of H. pylori infection occurs in the developing countries where up to 80% of the middle-aged adults may be infected. Bacterial infection causes an inflammatory response that proceeds through a series of intermediated stages of precancerous lesions (gastritis, atrophy, intestinal metaplasia, and dysplasia). Among infected individuals, approximately 10% develops severe gastric lesions such as peptic ulcer disease, 1-3% progresses to gastric cancer (GC) with a low 5-year survival rate, and 0.1% develops mucosa-associated lymphoid tissue (MALT). GC is one of the most common cancer and the third leading cause of cancer-related deaths worldwide. In this review, we have summarized the most recent papers about molecular mechanisms of H. pylori pathogenesis. The main important steps of H. pylori infection such as adhesion, entry in epithelial gastric cells, activation of intracellular pathways until epigenetic modifications have been described.

Recently increasing emphasis is placed on preventive health and management of chronic comorbidities avoiding long-term toxicities of antiretroviral therapy (ART). Drawing from this background we decided to use the Saos-2, osteosarcoma cell line, as a cellular model, to evaluate the effects of some antiretroviral drugs such as abacavir (ABC), tenofovir (TDF), efavirenz (EFV), etravirine (ETR), and darunavir (DRV), on bone differentiation related pathways. According to our observation, treatment with TDF and ABC affects the ability of the cells to produce calcium deposits with a reduced expression of type I collagen gene and p21 mRNA, also increasing the activity of Wnt3a related pathway. On the other hand treatment with EFV and DRV was not related to any significant reduction of calcium deposits but displayed a decrease in the expression of Wnt3a at day 14 and Type I Collagen at day 7 compared with untreated cells, even if this last down regulation was not confirmed at day 14. Instead ETR administration to Saos-2 cells increases the calcium deposits collagen type I production, as a result of Wnt3a mRNA overexpression, and of an upregulation of collagen type I expression, being also the only drug able to increase the expression of p21 cdk inhibitor as further marker of terminal differentiation. In summary these data suggest the potential negative interference of TDF and ABC on bone differentiation. DRV and EFV partially affect collagen type I production, instead ETR facilitates a positive bone balance as a result of an increased osteoblasts terminal differentiation.

The introduction of HAART (highly-active-antiretroviral-therapy) has resulted in extended survival of HIV positive patients. Conversely, due to the prolonged expectancy of life and the ageing of the HIV positive population, tumors are now one of the major cause of death, and among them hepatocellular carcinoma (HCC) has become a growing concern in these patients. Considering the potential anti-tumoral effects of HIV protease inhibitors, we decided to evaluate the anti-tumoral activity of Amprenavir on liver carcinoma and to evaluate its potential synergistic effects in combination with standard chemoterapic drugs, such as Doxorubicin. Our results indicate that Amprenavir had direct inhibitory effects on invasion of Huh-7 hepatocarcinoma cell lines, inhibiting MMP proteolytic activation. Amprenavir was able to delay the growth of hepatocarcinoma xenografts in nude mice and had a synergistic effect with Doxorubicin. Furthermore, Amprenavir was able to promote regression of hepatocarcinoma growth in vivo by anti-angiogenetic and overall anti-tumor activities, independently by PI3K/AKT related pathways that at today is one of the more suggestive hypothesis to explain the anti-tumor effects of the different protease inhibitors. In summary these findings suggest novel anti-neoplastic action of Amprenavir on liver cancer showing the possibility of novel combination therapies. J. Cell. Physiol. 228: 640–645, 2013. © 2012 Wiley Periodicals, Inc.

In the last few years, a major goal of cardiac research has been to drive stem cell differentiation to replace damaged myocardium. Several research groups have attempted to differentiate potential cardiac stem cells (CSCs) using bi- or three-dimensional systems supplemented with growth factors or molecules acting as differentiating substances. We hypothesize that these systems failed to induce a complete differentiation because they lacked an architectural space. In the present study, we isolated a pool of small proliferating and fibroblast-like cells from adult rat myocardium. The phenotype of these cells was assessed and the characterized cells were cultured in a collagen I/OPLA scaffold with horse serum to obtain fine myocardial differentiation. C-Kit(POS)/Sca-1(POS) CSCs fully differentiated in vitro when an environment more similar to the CSC niche was created. These experiments demonstrated an important model for the study of the biology of CSCs and the biochemical pathways that lead to myocardial differentiation. The results pave the way for a new surgical approach.

In the past, human heart has been considered a post-mitotic organ formed by cells, like adult cardiomyocytes, terminally differentiated and incapable of proliferation. This paradigm has been shaken by recent works indicating that postnatal adult cardiomyocytes are able to re-enter in the cell cycle and proliferate. In this view, the understanding of main candidates regulating cardiomyocyte cell cycle is of vital importance for future clinical approach.

The balance between cell death and cell proliferation and its regulation are essential features of many physiological processes and are particularly important in fetal morphogenesis and adult tissue homeostasis. Apoptosis is a type of cell suicide that is activated in two main ways: through a receptor-mediated pathway or through a mitochondrial pathway. We have investigated the immunohistochemical distribution of proteins belonging to these two pathways in human placenta during gestation by comparing their expression levels between the first and third trimester of gestation. In the first trimester, the receptor-mediated pathway prevails over the mitochondrial pathway with a moderate/intense expression of its three components, viz., Fas ligand (FasL), Fas, and caspase-8, and weak positivity of anti-apoptotic FLIP, these proteins being mainly localized in the cytotrophoblast compartment. In the third trimester of gestation, there is an increased expression of mitochondrial pathway proteins, viz., Apaf-1 and caspase-9. We have also investigated the expression level of caspase-3, the primary effector caspase of both pathways, and have observed that it is moderately expressed during gestation, being mainly localized in the cytotrophoblast during the first trimester and in both placental compartments during the third trimester of gestation. Thus, both pathways actively function in human placenta to execute cell death. By means of immunoelectron microscopy, we have further shown that, in human placenta, the two proteins of the mitochondrial pathway together with caspase-3 are localized both in the cytoplasm and in the nucleus. In particular, Apaf-1 and caspase-9 are distributed near to the nuclear envelope suggesting an important role for these two proteins in disrupting the nuclear-cytoplasmic barrier.

Cyclins are members of family of proteins involved in the cell cycle regulation. They are regulatory subunits of complexes with proteins called cyclin-dependent kinases (CDKs). There are three forms of cyclin T: cyclin T1, cyclin T2a, and T2b. All cyclin T contain an N-terminal "cyclin homology box," the most conserved region among different members of the cyclin family that serves to bind CDK9. In addition to the N-terminal cyclin domain, cyclin T contains a putative coiled-coil motif, a His-rich motif, and a C-terminal PEST sequence. The CDK9/cyclin T complex is able to activate gene expression in a catalytic-dependent manner, phosphorylating the carboxy-terminal domain (CTD) of RNA polymerase II. In addition, only cyclin T1 supports interactions between Tat and TAR. The interaction of Tat with cyclin T1 alters the conformation of Tat to enhance the affinity and specificity of the Tat:TAR interaction. On the other hand, CDK9/cyclin T2 complexes are involved in the regulation of terminal differentiation in muscle cells. © 2002 Wiley-Liss, Inc.

Myogenic transcription is repressed in myoblasts by serum-activated cyclin-dependent kinases, such as cdk2 and cdk4. Serum withdrawal promotes muscle-specific gene expression at least in part by down-regulating the activity of these cdks. Unlike the other cdks, cdk9 is not serum- or cell cycle-regulated and is instead involved in the regulation of transcriptional elongation by phosphorylating the carboxyl-terminal domain (CTD) of RNA polymerase II. While ectopic expression of cdk2 together with its regulatory subunits (cyclins E and A) inhibits myogenic transcription, overproduction of cdk9 and its associated cyclin (cyclin T2a) strengthens MyoD-dependent transcription and stimulates myogenic differentiation in both MyoD-converted fibroblasts and C2C12 muscle cells. Conversely, inhibition of cdk9 activity by a dominant negative form (cdk9-dn) represses the myogenic program. Cdk9, cyclinT2 and MyoD can be detected in a multimeric complex in C2C12 cells, with the minimal cdk9-binding region of MyoD mapping within 101-161 aa of the bHLH region. Finally, cdk9 can phosphorylate MyoD in vitro, suggesting the possibility that cdk9/cycT2a regulation of muscle differentiation includes the direct enzymatic activity of the kinase on MyoD.

The adenoviral E1A proteins are able to promote proliferation and transformation, inhibit differentiation, induce apoptosis, and suppress tumor growth. The extreme N terminus and conserved region one of E1A, which are indispensable for transcriptional regulation and for binding to p300/CBP, TBP, and pCAF, play essential roles in these abilities. These observations strongly suggest an intrinsic link between E1A-mediated transcriptional regulation and other effects. In this report, we show that E1A inhibits the normal growth of Saccharomyces cerevisiae HF7c, and this inhibition also depends on the domains required for transcriptional regulation. We demonstrate that E1A associates with histone acetyltransferase activity and represses the transactivation activity of transcription factor in S. cerevisiae, suggesting that E1A may suppress the expression of genes required for normal growth. Based on yeast growth rescue, we present a genetic screening strategy that identified RACK1 as an E1A antagonizing factor. Expression of human RACK1 efficiently relieves E1A-mediated growth inhibition in HF7c and protects human tumor cells from E1A-induced apoptosis. Finally, we show that RACK1 decreases E1A-associated histone acetyltransferase activity in yeast and mammalian cells, and physically interacts with E1A. Our data demonstrate that RACK1 is a repressor of E1A, possibly by antagonizing the effects of E1A on host gene transcription.

Cdk9, previously known as PITALRE, belongs to the Cdc2 family of protein kinases. We report the isolation and characterization of the complete gene coding for the murine Cdk9 protein. The gene contains seven exons spanning over 6 kb of genomic DNA, and the exon/intron boundaries conformed to the GT/AG rule. The Cdk9 gene mapped on mouse chromosome 2, which is consistent with the known region of synteny with human chromosome 9q34.1. The length of the individual exons ranged from 82 to 850 bp, and introns ranged from 452 to 1,465 bp. The further 5' flanking region of the gene showed features of a housekeeping promoter, such as the lack of a canonical TATA box and the presence of a CCAAT box as well as several GC boxes, which are potential binding sites for numerous transcription factors. Additionally, we performed a basic analysis of the transcriptional activity of the promoter and found that the 364 bp of Cdk9 5' flanking region were able to elicit high transcriptional levels of a luciferase reporter gene in NIH3T3 cells. This study provides the molecular basis for understanding the transcriptional control of the Cdk9 gene, and could serve to facilitate the molecular genetic investigation of Cdk9 function during mouse embryonal development.

Human immunodeficiency virus type-1 (HIV-1) infection of the central nervous system (CNS) gives rise to many of the neurological complications in patients with AIDS. Infection of microglial cells and astrocytes in the brain promotes the release of HIV-1 Tat and other candidate neurotoxins that may be associated with the widespread neuropathology. To examine the contribution of HIV-1 Tat to the interplay between virus and CNS cells, the human astrocytic cell line, U-87MG, was treated with recombinant Tat protein. Fluorescence-activated cell sorting analysis indicated that Tat induces a G1 arrest in these cells. Consistent with this observation, lower levels of cyclin E-Cdk2 kinase activity and phosphorylated Rb were detected in the Tat-treated cells compared with the control cells. Interestingly, our observations indicate that the underphosphorylated form of Rb that is prevalent in Tat-treated cells promotes HIV-1 transcription by a mechanism involving the NF-kappaB enhancer region. Taken together, the data presented here provide the first evidence that the HIV-1 regulatory protein, Tat, may manipulate the host cell cycle to promote viral gene expression. The significance of these findings relates to the current hypothesis that indirect effects of HIV-1 infection of the CNS may contribute to the neurological complications associated with AIDS dementia complex.

To evaluate transcriptional mechanisms during cytokine induction of myeloid progenitor cell proliferation, we examined the expression and activity of transcription factors that control cell cycle-dependent histone genes in interleukin-3 (IL-3)-dependent FDC-P1 cells. Histone genes are transcriptionally upregulated in response to a series of cellular regulatory signals that mediate competency for cell cycle progression at the G1/S-phase transition. We therefore focused on factors that are functionally related to activity of the principal cell cycle progression at the G1/S-phase transition. We therefore focused on factors that are functionally related to activity of the principal cell cycle regulatory element of the histone H4 promoter:CDC2, cyclin A, as well as RB-and IRF-related proteins. Comparisons were made with activities of ubiquitous transcription factors that influence a broad spectrum of promoters independent of proliferation or expression of tissue-specific phenotypic properties. Northern blot analysis indicates that cellular levels of cyclin A and CDC2 mRNAs increase when DNA synthesis and H4 gene expression are initiated, supporting invoulvement in cell cycle progression. Using gel-shift assays, incorporating factor-specific antibody and oligonucleotide competition controls, we define three sequential periods following cytokine stimulation of FDC-P1 cells when selective upregulation of a subset of transcription factors is observed. In the initial period, the levels of SP1 and HiNF-P are moderately elevated; ATF, AP-1, and HiNF-M/IRF-2 are maximal during the second period; while E2F and HiNF-D, which contain cyclin A as a component, predominate during the third period, coinciding with maximal H4 gene expression and DNA synthesis. Differential regulation of H4 gene transcription factors following growth stimulation is consistent with a principal role of histone gene promoter elements in integrating cues from multiple signaling pathways that control cell cycle induction and progression. Regulation of transcription factors controlling histone gene promoter activity within the context of a staged cascade of responsiveness to cyclins and other physiological mediators of proliferation in FDC-P1 cells provides a paradigm for experimentally addressing interdependent cell cycle and cell growth parameters that are operative in hematopoietic stem cells. © 1995 Wiley-Liss, Inc.

The Rb2/p130 protein has been shown to have a high sequence homology with the retinoblastoma gene product (pRb), one of the most well‐characterized tumor suppressor genes, and with pRb‐related p107, especially in their conserved pocket domains, which display a primary role in the function of these proteins. In this study, we report on the biochemical and immunocytochemical characterization of the Rb2/p130 protein, using a polyclonal antibody developed against its “spacer” region included in the pocket domain of the whole protein. We show that pRb/p130 is a phosphoprotein located at the nuclear level and that its phosphorylation pathway can be dramatically reduced by phosphatase treatment. Moreover pRb/p130, with p107, with p107, is one of the major targets of the E1A viral oncoprotein‐associated kinase activity, showing a phosphorylation pattern which is modulated during the cell cycle, reaching a peak of activation at the onset of S‐phase. © 1995 Wiley‐Liss, Inc. Copyright © 1995 Wiley‐Liss, Inc.

Employing the myeloblastic leukemia M1 cell line, which does not express endogenous p53, and genetically engineered variants, it was recently shown that activation of p53, using a p53 temperature-sensitive mutant transgene (p53ts), resulted in rapid apoptosis that was delayed by high level ectopic expression of bcl-2. In this report, advantage has been taken of these M1 variants to investigate the relationship between p53-mediated G1 arrest and apoptosis. Flow cytometric cell cycle analysis has provided evidence that activation of wild-type (wt) p53 function in M1 cells resulted in the induction of G1 growth arrest; this was clearly seen in the M1p53/bcl-2 cells because of the delay in apoptosis that unmasked p53-induced G1 growth arrest. This finding was further corroborated at the molecular level by analysis of the expression and function of key cell cycle regulatory genes in M1p53 versus M1p53/bcl-2 cells after the activation of wt p53 function; events that take place at early times during the p53-induced G1 arrest occur in both the M1p53 and the M1p53/bcl-2 cells, whereas later events occur only in the M1p53/bcl-2 cells, which undergo delayed apoptosis, thereby allowing the cells to complete G1 arrest. Finally, it was observed that a spectrum of p53 target genes implicated in p53-induced growth suppression and apoptosis were similarly regulated, either induced (gadd45, waf1, mdm2, and bax) or suppressed (c-myc and bcl-2), after activation of wt p53 function in M1p53 and M1p53/bcl-2 cells. Taken together, these findings show that wt p53 can simultaneously induce the genetic programs of both G1 growth arrest and apoptosis within the same cell type, in which the genetic program of cell death can proceed in either G1-arrested (M1p53/bcl-2) or cycling (M1p53) cells. These findings increase our understanding of the functions of p53 as a tumor suppressor and how alterations in these functions could contribute to malignancy.

The introduction of highly active antiretroviral therapies (HAART) has significantly changed the clinical course of HIV disease, with prolonged survival and better quality of life for HIV infected patients. However, this successful therapeutic advance has been partially marked by the development of serious long-term side effects including metabolic alterations, cardiovascular disease, kidney impairment, bone alterations and adipose tissue redistribution. This last phenomenon is currently indicated as HIV related lipodystrophy (Barbaro, 2006). Even if some studies suggested an independent role for HIV in the development of lipodystrophic phenotype, there is a widely accepted consensus that the risk to develop fat redistribution in HIV patients has to be mostly related to antiretroviral therapy. In order to investigate new pathways involved in the development of lipodystrophy, our group performed an array screening using two identical filter arrays with cDNAlabeled probes, generated from the adipose tissue of either HIV patients affected or not affected by lipodystrophy. Among the genes selected, we focused our attention on a recently described 48 kDa protein of 417 amino acids named FAP48. Our results suggest, using 3T3-L1-FAP48 stable clone, that FAP48 over-expression results in rapid NFAT dephosphorilatyon by activating CaN and in the increase of aP2 gene transcription, a gene expressed at the last phase of the adipocyte differentiation. These data support the role of Fap48 in the activation of adipocyte differentiation through a pathway involving NFAT. Moreover we evaluated the expression of PPARγ and aP2 in 3T3-L1 FAP48pcDNA stably transfected cells treated with five antiretroviral drugs (Indinavir, Amprenavir, Efavirenz, Stavudine and Saquinavir), belonging to the three main classes of anti-HIV drugs, that were able, in our experimental model, to affect adipocyte differentiation (Esposito et al., 2009). We observed that cells treated with Saquinavir and Efavirenz, using 3T3-L1FAP48 stable clone, are characterized by an increased expression of PPARγ and aP2, during the 6 day time course, compared with the control cells. This evidence supports the hypothesis of a protective mechanism, that in 3T3L1 cells could counteract the toxicity of Efavirenz and Saquinavir or could be activated in presence of these drugs. Drawing from our experimental results it can be then postulated that this mechanism could work trough FAP48/ FBP52/Hsp90 pathway, suggesting this complex as a potential target for novel therapeutic approaches to the HAART related lipodystrophy in patients treated with regimen including Efavirenz and Saquinavir. references

The cell cycle consists of a number of complex biochemical pathways that ensure that the start of a particular event depends on the successful and right end of previous steps in the pathway. An important role is played by cyclin/cyclin-dependent kinase (cdk) complexes which are critical regulators of cell cycle progression and RNA transcription. To ensure proper progression through each phase, cells have developed a series of orchestrated checkpoints that govern the different cellular kinases required for distinct cell cycle events. In particular, several cell cycle protein kinases, including members of the Aurora family and the Polo-like kinases, play critical roles in mitotic entry and chromosome segregation that ensure the correct formation of daughter cells. Tumour cell proliferation is frequently associated to both genetic and epigenetic mechanisms commonly affecting the expression of cell cycle regulatory proteins or causing an incompetent checkpoint control, resulting in aberrant responses to cellular damage. These alterations result not only in proliferative advantages but also in an increased susceptibility to the accumulation of additional genetic alterations that contribute to tumour progression and acquisition of more aggressive phenotypes. In the last years, the identification of anticancer drugs directed against critical cell cycle regulators has received particular attention. Specifically, several preclinical and clinical trials are addressing cdks or cell cycle protein kinase inhibitors. Starting from a description of cell cycle, this review summarizes the most recent studies on drugs targeting cell cycle regulators that are being used in cancer therapy.

It is known that the MyoD family members (MyoD, Myf5, myogenin, and MRF4) play a pivotal role in the complex mechanism of skeletal muscle cell differentiation. However, fragmentary information on transcription factor-specific regulation is available and data on their post-transcriptional and post-translational behavior are still missing. In this work, we combined mRNA and protein expression analysis with their subcellular localization. Each myogenic regulator factor (MRF) revealed a specific mRNA trend and a protein quantitative analysis not overlapping, suggesting the presence of post-transcriptional mechanisms. In addition, each MRF showed a specific behavior in situ, characterized by a differentiation stage-dependent localization suggestive of a post-translational regulation also. Consistently with their transcriptional activity, immunogold electron microscopy data revealed MRFs distribution in interchromatin domains. Our results showed a MyoD and Myf5 contrasting expression profile in proliferating myoblasts, as well as myogenin and MRF4 opposite distribution in the terminally differentiated myotubes. Interestingly, MRFs expression and subcellular localization analysis during C2C12 cell differentiation stages showed two main MRFs regulation mechanisms: (i) the protein half-life regulation to modulate the differentiation stage-dependent transcriptional activity and (ii) the cytoplasmic retention, as a translocation process, to inhibit the transcriptional activity. Therefore, our results exhibit that MRFs nucleo-cytoplasmic trafficking is involved in muscle differentiation and suggest that, besides the MRFs expression level, also MRFs subcellular localization, related to their functional activity, plays a key role as a regulatory step in transcriptional control mechanisms.

The pathogenetic bases of HAART-associated lipodystrophy are still poorly known, even if it is clear that adipose tissue and its metabolism are sensitive to antiretroviral therapy alone and/or in combination with HIV infection. The NEDD8 system is essential for the regulation of protein degradation pathways involved in cell cycle progression, morphogenesis and tumorigenesis. We investigated the possible involvement of NEED8 in adipogenesis and, consequently, in HIV-related lipodystrophy. One hundred HIV-1-infected patients were included in the study. Using an in vitro model of adipogenesis we evaluated the effects on adipogenesis of the forced expression of NEDD8 together with efavirenz, stavudine, saquinavir, amprenavir and indinavir, belonging to the three main classes of anti-HIV medications. We showed that NEDD8 expression level is higher in the peripheral blood of HIV patients developing lipodystrophy. Coherently, forced expression of NEDD8 in an in vitro model of adipogenesis was able to perturb expression of some key proteins involved in adipogenesis, such as C/EBPα and PPARγ, possibly acting throughout the NEDD8/p27/β-catenin pathway. Moreover, three out of five evaluated drugs were able to affect adipocyte differentiation: efavirenz, stavudine and saquinavir. Finally, we have shown that NEDD8 was expressed in the fat tissue of lipodystrophic patients, being significantly higher in the lipodystrophic patients with respect to the controls, thus further confirming the altered NEDD8 expression in the fat tissue of HIV-infected patients affected by lipodystrophy. Taken together, our data support the hypothesis of an implication of NEDD8 through p27 and β-catenin pathways in the disruption of adipogenesis and consequent lipodystrophy in patients affected by HIV infection under HAART therapy with qualitative and quantitative differences according to diverse antiretroviral treatments. These evidences indicate the NEDD8/β-catenin/p27 pathway as a possible molecular target for prevention of lipodystrophy development in patients under HAART therapy. © 2008 International Society of Differentiation.

Histone deacetylase (HDAC) inhibitors are promising new epi-drugs, but the presence of both class I and class II enzymes in HDAC complexes precludes a detailed elucidation of the individual HDAC functions. By using the class II-specific HDAC inhibitor MC1568, we separated class I- and class II-dependent effects and defined the roles of class II enzymes in muscle differentiation in cultured cells and in vivo. MC1568 arrests myogenesis by (i) decreasing myocyte enhancer factor 2D (MEF2D) expression, (ii) by stabilizing the HDAC4-HDAC3-MEF2D complex, and (iii) paradoxically, by inhibiting differentiation-induced MEF2D acetylation. In vivo MC1568 shows an apparent tissue-selective HDAC inhibition. In skeletal muscle and heart, MC1568 inhibits the activity of HDAC4 and HDAC5 without affecting HDAC3 activity, thereby leaving MEF2-HDAC complexes in a repressed state. Our results suggest that HDAC class II-selective inhibitors might have a therapeutic potential for the treatment of muscle and heart diseases. Histone deacetylase (HDAC) inhibitors are promising new epi-drugs, but the presence of both class I and class II enzymes in HDAC complexes precludes a detailed elucidation of the individual HDAC functions. By using the class II-specific HDAC inhibitor MC1568, we separated class I- and class II-dependent effects and defined the roles of class II enzymes in muscle differentiation in cultured cells and in vivo. MC1568 arrests myogenesis by (i) decreasing myocyte enhancer factor 2D (MEF2D) expression, (ii) by stabilizing the HDAC4-HDAC3-MEF2D complex, and (iii) paradoxically, by inhibiting differentiation-induced MEF2D acetylation. In vivo MC1568 shows an apparent tissue-selective HDAC inhibition. In skeletal muscle and heart, MC1568 inhibits the activity of HDAC4 and HDAC5 without affecting HDAC3 activity, thereby leaving MEF2-HDAC complexes in a repressed state. Our results suggest that HDAC class II-selective inhibitors might have a therapeutic potential for the treatment of muscle and heart diseases.

Recently, suggestive evidence for piecemeal degranulation (PMD), a particulate pattern of cell secretion accomplished by vesicle-mediated extracellular transport of granule-stored material, has been provided by electron microscopy investigations in chromaffin cells of different vertebrate species. In this study, chromaffin tissue from the interrenal gland of the amphibian urodede Triturus carnifex has been investigated by quantitative transmission electron microscopy in search for ultrastructural clues indicative of a vesicle-mediated mode of cell degranulation. Interestingly, a single type of chromaffin cell is recognizable in T. carnifex, which undergoes seasonal variations in its adrenaline and noradrenaline granule ratio according to an annual cycle that matches the trend of changes in secondary sexual characters. In this study, we looked for a series of ultrastructural changes regarded as highly specific for PMD. We calculated the percentage of (i) resting, unaltered granules (type 1 granules); (ii) granules with changes indicative of progressive release of secretory materials, that is, granules with lucent areas in their cores, reduced electron density, disassembled matrices, and residual cores (type 2 granules); and (iii) membrane empty containers (type 3 granules) in chromaffin cells of T. carnifex during the annual cycle. We found a significant increase in type 2 and 3 granules, accompanied by a significant decrease in type 1 granules, in the April and November samples. During the same seasonal periods, the number per net cytoplasmic area of 30-100-nm diameter electron-dense vesicles was found to be significantly augmented, and there was also an augmented percentage of chromaffin granules showing blebs or protrusions in their profiles. These ultrastructural data are indicative of an increased vesicle-mediated transport of chromaffin granule products for extracellular release in the amphibian T. carnifex in accordance with the increased rate of catecholamine release. This vesicle-mediated pattern of cell secretion suits the schema of PMD. In an evolutionary perspective, these findings suggest that PMD is a secretory pathway that has been highly conserved throughout vertebrate classes. Anat Rec, 2009. (c) 2008 Wiley-Liss, Inc.

Objectives: Melanoma cells take advantage of impaired ability to undergo programmed cell death in response to different external stimuli and chemotherapeutic drugs; this makes prevention of tumour progression very difficult. The aim of this study was to demonstrate whether 3-O-methylfunicone (OMF), a metabolite of Penicillium pinophilum, has the ability to arrest cell population growth and to induce apoptosis in A375P (parental) and A375M (metastasis derivatived) melanoma cell lines. Materials and methods: Cell proliferation and apoptosis were analysed by flow cytometry, DNA fragmentation, caspase-3 and caspase-9 activation, and PARP-1 cleavage. Results: We demonstrated that OMF affected cell proliferation in a time- and dose-dependent manner, reaching the best effect at concentration of 80 g/ml for 24 h. Flow cytometry revealed that OMF caused significant G2 phase arrest, which was associated with marked decrease in cyclin B1/p34cdc2 complex and p21 induction. OMF also induced marked decrease of survivin expression. Reduced levels of apoptosis were evident after silencing p21 expression in both cell lines. Finally, the effect exercised by OMF on hTERT and TEP-1 gene expression confirmed the ability of this molecule to interfere with replicative ability of cells. Conclusions: The results reported here seem to suggest that OMF as a promising molecule to include in strategies for treatment of melanoma. © 2009 Blackwell Publishing Ltd.

The objective of this study was to investigate the pattern of expression and the localization of Notch-1, Notch-4 and Jagged-1 in physiological and pathological human endometrium and to evaluate the expression levels of two major regulators of the G1 checkpoint, namely cyclin D1 and p21. Sixty samples of physiological endometrium and 60 samples of pathological endometrium were used for the study. Evaluation of the expression level and the distribution of Notch pathway members and cell-cycle proteins was performed by immunohistochemistry. In the physiological endometrium we observed an increase of Notch-1 and Jagged-1 from proliferative to secretory phase and an opposite trend for Notch-4. In menopause, the level of expression of all three members of the Notch pathway decreased. We also observed a cyclin D1 increase from proliferative to secretory phase. By contrast, p21 showed a slight increase from proliferative to secretory phase. In the pathological endometrium, we observed an increase of Notch-1 expression from polyps to carcinoma and decrease for Notch-4 and Jagged-1. Moreover, we observed a higher expression of cyclin D1 in all the endometrial pathologies. By contrast, the expression level of p21 slightly increased from polyps to carcinoma. We concluded that in human endometrium Notch-4 seems to be more involved in controlling proliferation, whereas Notch-1 seems to be more involved in differentiation programming. Deregulation of these functions may induce the onset of several endometrial pathologies from polyps to cancer.

Cdk9/Cyclin T1 complex is very important in controlling specific differentiative pathways of several cell types. Limited data are available regarding the expression of Cdk9/Cyclin T1 in hematopoietic and lymphoid tissues. Cdk9/Cyclin T1 expression seems to be related to particular stages of lymphoid differentiation/activation. In this study, we observed that the expression level of Cdk9/Cyclin T1 in vivo increases in memory B cells compared to naive B cells, and in activated B cells, compared to non-activated ones. The expression level of the Cdk9/Cyclin T1 complex does not increase in cells induced to differentiate in vitro. In addition, we showed that Cdk9 interacts with E12 and E47, specifically activated during Germinal Center (GC) reaction. Taken together this data suggests an active role for the Cdk9/Cyclin T1 complex during lymphoid differentiation through germinal center reaction. J. Cell. Physiol. 215: 276–282, 2008. © 2008 Wiley-Liss, Inc.

In this study, we have evaluated the effects on cell cycle regulation of VacA alone and in combination with other two Helicobacter pylori proteins, cytotoxin-associated protein (CagA) and HspB, using the human gastric epithelial cells (AGS). Our results indicate that VacA alone was able to inhibit the G1 to S progression of the cell cycle. The VacA capacity of inhibiting cell progression from G1 to S phase was also observed when cells were co-transfected with CagA or HspB. Moreover, VacA over-expression caused apoptosis in AGS cells through activation of caspase 8 and even more of caspase 9, thus indicating an involvement of both the receptor-mediated and the mitochondrial pathways of apoptosis. Indeed, the two pathways probably can co-operate to execute cell death with a prevalence of the mitochondrial pathways. Our data taken together provide additional information to further enhance our understanding of the molecular mechanism by which H. pylori proteins alter the growth status of human gastric epithelial cells. © 2007 Wiley-Liss, Inc.

none 11 Heat shock protein B (HspB) is one of the dominant proteins recognized by most Helicobacter pylori-infected persons and is being considered as potential candidates for subunit vaccines. In the present study we describe the generation of an antibody against HspB and its use in immunohistochemical assays on gastric biopsies. We have demonstrated that our rabbit polyclonal antibody against HspB did not recognize any protein in lysates from a lung human epithelial cell (H1299) line and did not cross-react with the other members of human heat shock proteins. Secondly, we have observed that in gastric biopsies, HspB immunostaining was present inside the cytoplasm of human epithelial cells with a particular localization in the apical portion of gastric epithelial cells other than in the extracellular spaces among gastric cells of human stomach. Finally, we have demonstrated a cytoplasmic HspB immunostaining in groups of neoplastic cells of MALT lymphoma. In conclusion, our observations suggest a possible involvement of HspB in the pathogenesis of H. pylori-related pathologies such as gastritis, ulcer and gastric cancer. © 2008 Wiley-Liss, Inc. mixed DE LUCA A; DE FALCO M; MANENTE L; DATTILO D; LUCARIELLO A; ESPOSITO V; GNARINI M; CITRO G; BALDI A; TUFANO MA; IAQUINTO G De Luca A.; De Falco M.; Manente L.; Dattilo D.; Lucariello A.; Esposito V.; Gnarini M.; Citro G.; Baldi A.; Tufano M.A.; Iaquinto G.

One strategy in the development of anticancer therapeutics has been to arrest malignant proliferation through inhibition of the enzymatic activity of cyclin-dependent kinases (cdks), which are key regulatory molecules of the cell cycle. Over the past few years, numerous compounds with remarkable cdk inhibitory activity have been studied in cancer therapy, although it is very difficult to point out the best cdk to target. An excellent candidate appears to be cdk2, whose alteration is a pathogenic hallmark of tumorigenesis. The small molecule described in our study showed an inhibitory effect on the kinase activity of cdk2, a significant growth arrest observed in a colony formation assay and a reduction in the size of the tumor in nude mice, thus suggesting its potential role as a promising new type of mechanism-based antitumor drug, also for the treatment of hyperproliferative disorders.

Notch proteins are a transmembrane receptor family that is structurally and functionally conserved from worms to humans. The mammalian family of Notch proteins consists of several genes encoding Notch receptors and related Notch ligands. Notch signaling is involved in different aspects of the cell-fate decision tree: differentiation, proliferation, and apoptosis. These three processes are finely regulated in human placenta in order to allow a successful pregnancy and correct fetal growth. Notch and its ligands also participate in vascular remodeling and stabilization. Vasculogenesis and blood regulation are of importance in the human placenta for normal fetal development and growth; any disorder of these systems leads to preeclampsia. Drawing on this background, we have investigated the expression of Notch-1, Notch-4, and Jagged-1, together with two members related to the Notch pathway in angiogenesis: VEGF and p21. Normal and preeclamptic human placentas have been evaluated by immunohistochemistry. In preeclamptic samples, a down-regulation of Notch pathway members occurs with a weak/moderate expression of the Notch protein members in all components of placenta compared with physiological placentas that, at term, exhibit the strong expression of Jagged-1 and a moderate expression of both Notch-1 and Notch-4 in all compartments of the placental villi. Moreover, preeclamptic samples also reveal a down-regulation of VEGF expression, together with a moderate nuclear expression of p21(Cip1) in the syncytiotrophoblast, cytotrophoblast, and endothelial cells. This down-regulation of VEGF in preeclamptic placentas, in turn, probably decreases Notch protein expression in placental compartments and in endothelial cells and could offer an ethiopathogenetic explanation for the onset of this pathology.

Notch signaling is an evolutionarily conserved mechanism used by invertebrates and vertebrates to control cell fates through close-range cell interactions. Four Notch receptors have been identified in vertebrates and different ligands, divided into Delta-like and Serrate-like (Jagged). Several studies have demonstrated that Notch signaling is involved in different branches of the cell fate decision tree: differentiation, proliferation and apoptosis. These three processes are finely regulated in human placenta in order to allow a successful pregnancy and a correct fetal growth. Moreover, Notch and its ligands participate in the vascular remodelling and stabilization, other two processes much important and ticklish in human placenta. So, we decided to investigate the pattern of expression of Notch-1, Notch-4 and Jagged-1, together with two members related to Notch pathway and involved in angiogenesis: VEGF and p21, in human placenta during gestation by immunoblotting and immunohistochemistry. We showed a modulation of Notch proteins throughout the pregnancy; in particular we showed a slight decrease of Notch-1 throughout pregnancy, with a decreased cytoplasmic staining from the first to the third trimester of gestation in cytotrophoblast and syncytiotrophoblast. In contrast Jagged-1 showed an increase throughout pregnancy especially in syncytiotrophoblast and stroma during the third trimester of gestation. In addition, we found by immunoblotting an increase of VEGF expression from the first to the third trimester and an intense VEGF expression inside endothelial cells throughout the gestation as also confirmed by immunohistochemistry. We also showed a decrease of p21 expression during the pregnancy both through immunoblotting and immunohistochemistry assays. Moreover, we observed Notch localization in extravillous trophoblast cells that are able to invade the decidualized endometrium. Our results suggest an involvement of Notch signaling in regulation of placental cell fate decision and in angiogenesis that are dramatically important to maintain a normal physiology of this organ during pregnancy.

With the aim to find novel partners of human Cyclin T2a, we performed a two-hybrid screening in yeast using the full-length cDNA of this cyclin as bait, and a human heart cDNA library as preys Source. Upon several interesting genes selected, our attention has been focused on the cDNA coding for PKN alpha, a fatty acid- and Rho-activated serine/threonine protein kinase, having a catalytic domain homologous to protein kinase C family. Co-immunoprecipitation and in vitro pull-down assays independently confirmed the interaction between the two proteins. Luciferase assays, performed on NIH3T3 cell extracts after transfection with a MyoD-responsive promoter, pointed out that PKN alpha was able to enhance MyoD-dependent transcription, and that this effect was further increased when cyclin T2a was co-overexpressed. Finally, overexpression of both Cyclin T2a and PKNC alpha. in C2C12 cells strongly enhanced the expression of myogenic differentiation markers, such as Myogenin and Myosin Heavy Chain, during starvation-induced differentiation. Taken together, our data strengthen the hypothesis that cyclin T2a plays a role in muscle differentiation, and propose PKNa as a novel partner of Cyclin T2a in this process.

Apelin is a novel bioactive peptide that has been isolated from bovine stomach extracts and identified as the endogenous ligand for the APJ receptor. Although the main physiological functions of apelin have not yet been clarified, it is known that apelin is involved in the regulation of blood pressure, central control of body fluid homeostasis and the modulation of immune response. In order to investigate the distribution of apelin in reptiles, we have performed an immunohistochemical analysis on tissues of the lizard Podarcis sicula. The peptide was found to be widely distributed, although its cellular localization differed in the various organs examined. A strong immunopositivity was found in the heart, stomach and intestine. In the spleen, an intense apelin immunopositivity was restricted to a discrete number of cells scattered throughout the red pulp and co-localized with immunoglobulin kappa and lambda chains, suggesting an analogous function of this peptide in immune responses also in reptiles. Intriguingly, apelin immunoreactivity was discretely localized in endothelial cells in the lung and thyroid gland. In the light of these data, we conclude that apelin may have multiple functions in reptiles.

The adenoviral E1A proteins have been implicated in promotion of proliferation and transformation, inhibition of differentiation, induction of apoptosis, regulation of transcription, and suppression of tumor growth. The ability of E1A to override the fundamental controls of host cells is based on its ability to physically interact with several cellular proteins. We recently characterized RACK1 as a new E1A-interacting protein. In this report, we show that the extreme N-terminal region of E1A, spanning from aminoacids 1-36, and the conserved WD regions of RACK1 are responsible for this interaction. We also demonstrate that E1A and RACK1 colocalize at the perinuclear membrane in the cells. Furthermore, we provide evidence that E1A is able to antagonize the inhibitory effects of RACK1 on Src activity. These results suggest that RACK1 signaling pathway may be a functional target of E1A, contributing to E1A oncogenic effect in the host cells. © 2003 Wiley-Liss, Inc.

Progression through the cell cycle in eukaryotic cells is controlled by a family of protein kinases, termed cyclin-dependent kinases (CDKs), and their specific partners, the cyclins. In particular, the control of mammalian cell proliferation occurs largely during the G1 phase of the cell cycle. Five mammalian G1 cyclins have been enumerated to date: cyclins D1, D2, and D3 (D-type cyclins), and cyclins E and E2. By the use of immunohistochemistry and immunoelectron microscopy, we observed that in the first trimester of gestation of human placenta, cyclin D1 was distributed in the nuclei of the cytotrophoblast compartment together with a weak positivity of endothelial cells surrounding blood vessels. The endothelial positivity of cyclin D1 strongly increased in the third trimester of gestation. Moreover, we observed the subcellular localization of cyclin D1 that was present both in the stroma of placental villi and in the nuclei of syncytiotrophoblast cells. Therefore, we observed that CDK4 was localized in the nuclei of the cytotrophoblast compartment during the first and third trimesters and it also had a nuclear positivity in the endothelial cells of blood vessels at the end of the third trimester of gestation. In conclusion we may hypothesize that cyclin D1/CDK4 complex functions to regulate the cell cycle progression in the proliferative compartment of human placenta, the cytotrophoblast, during the first trimester through interaction with p107 and p130. Therefore, cyclin D1 and CDK4 seem to be involved in the control of placental angiogenesis during the third trimester of gestation.

Thyroid hormone receptors (TRs) and members of the myocyte enhancer factor 2 (MEF2) family are involved in the regulation of muscle-specific gene expression during myogenesis. Physical interaction between these two factors is required to synergistically activate gene transcription. p300/cAMP-response-element-binding-protein ('CREB')-binding protein (CBP) interacting with transcription factors is able to increase their activity on target gene promoters. We investigated the role of p300 in regulating the TR—MEF2A complex. To this end, we mapped the regions of these proteins involved in physical interactions and we evaluated the expression of a chloramphenicol acetyltransferase (CAT) reporter gene in U2OS cells under control of the α-myosin heavy chain promoter containing the thyroid hormone response element (TRE). Our results suggested a role of p300/CBP in mediating the transactivation effects of the TR—retenoid X receptor (RxR)—MEF2A complex. Our findings showed that the same C-terminal portion of p300 binds the N-terminal domains of both TR and MEF2A, and our in vivo studies demonstrated that TR, MEF2A and p300 form a ternary complex. Moreover, by the use of CAT assays, we demonstrated that adenovirus E1A inhibits activation of transcription by TR—RxR—MEF2A—p300 but not by TR—RxR—MEF2A. Our data suggested that p300 can bind and modulate the activity of TR—RxR—MEF2A at TRE. In addition, it is speculated that p300 might modulate the activity of the TR—RxR—MEF2A complex by recruiting a hypothetical endogenous inhibitor which may act like adenovirus E1A.

Genetic aberrations, mostly resulting in changes in gene expression, are critical events in cancer onset and progression. The advent of the cDNA array technology allows the screening and the efficient measurement of expression of thousands genes simultaneously in a wide spectrum of experimental and clinical models. This genomic scale approach is being currently used to obtain global views of human cancer gene expression and to identify genetic markers that might be important for diagnosis, prognosis, and therapy. This review discusses some recent findings obtained by means of cDNA arrays investigating the human melanoma. © 2003 Wiley-Liss, Inc.

Although the structural and pharmacological properties of endothelin (ET) receptors have been studied, little is known concerning their physiological significance, even if each subtype is supposed to have a distinct physiological action. Thus, to further elucidate the physiological function of this receptor, we examined the presence and distribution of the endothelin-B receptor (ET(B)) subtype in tissues of the lizard Podarcis sicula, using immunoblotting and immunohistochemistry. Immunoblotting indicated that, although the ET(B) receptor appears to be ubiquitous, it is present at different levels in the tissues examined. Furthermore, immunohistochemistry showed that this receptor is very abundant in endothelial cells of all tissues, suggesting that there is an ET(B)-mediated autocrine system of endothelin, which plays an important role in the regulation of endothelial cell function. On the other hand, the presence of ET(B) immunoreactivity also in endocrine systems such as adrenal and thyroid glands suggests an involvement also in the paracrine system of these organs.

Caveolae are plasma membrane subcompartments that have been implicated in signal transduction. In many cellular systems, caveolae are rich in signal transduction molecules such as G proteins and receptor-associated tyrosine kinases. An important structural component of the caveolae is caveolin. Recent evidence show that among the caveolin gene family, caveolin-3 is expressed in skeletal and cardiac muscle and caveolae are present in cardiac myocyte cells. Both the ANP receptor as well as the muscarinic receptor have been localized to the caveolae of cardiac myocytes in culture. These findings prompted us to conduct a further analysis of cardiac caveolae. In order to improve our understanding of the mechanisms of signal transduction regulation in cardiac myocytes, we isolated cardiac caveolae by discontinuous sucrose density gradient centrifugation from rat ventricles and rat neonatal cardiocytes. Our analysis of caveolar content demonstrates that heterotrimeric G proteins, p21ras and receptor-associated tyrosine kinases are concentrated within these structures. We also show that adrenergic stimulation induces an increase in the amount of diverse a- and b-subunits of G proteins, as well as p21ras, in both in vivo and in vitro experimental settings. Our data show that cardiac caveolae are an important site of signal transduction regulation. This finding suggests a potential role for these structures in physiological and pathological states. J. Cell. Biochem. 77:529-539, 2000. © 2000 Wiley-Liss, Inc.

An association between cyclin D3 and the C-terminal domain of pRb2/p130 was demonstrated using the yeast two-hybrid system. Further analysis restricted the epitope responsible for the binding within the 74 N-terminal amino acids of cyclin D3, independent of the LXCXE amino acid motif present in the D-type cyclin N-terminal region. In a coprecipitation assay in T98G cells, a human glioblastoma cell line, the C-terminal domain of pRb2/p130 was able to interact solely with cyclin D3, while the corresponding portion of pRb interacted with either cyclin D3 or cyclin D1. In T98G cells, endogenous cyclin D3-associated kinase activity showed a clear predisposition to phosphorylate preferen- tially the C-terminal domain of pRb2/p130, rather than that of pRb. This propensity was also confirmed in LAN-5 human neuroblastoma cells, where phosphorylation of the pRb2/p130 C-terminal domain and expression of cyclin D3 also decreased remarkably in the late neural differentiation stages. J. Cell. Biochem. 75:698-709, 1999. r 1999 Wiley-Liss, Inc.

We investigate the role played by dendritic cells (DCs) in the non-obese diabetic (NOD) mouse pancreas. The early peri-islet, nondestructive infiltration phase, and intra-islet, destructive infiltration phase, which immediately precedes overt diabetes, are studied. Results show that infiltrating cells are Ia-b, ICAM-1, and, mainly, MIDC-8 immunoreactive (ir). These data from silica-treated animals and ultrastructural observations strongly support the hypothesis that DCs are both Ia-b-ir and ICAM-1-ir and that they exert a pivotal role during the period of early infiltration. This is a novel finding for NOD mice and increases the interest for this protective cell type during the rather complex islet infiltration process. Moreover, the cytokine profile demonstrates that Th2 protective cytokines are specific for peri-islet infiltrate. Disappearance of DCs from the infiltrate is concomitant with both the formation of intra-islet infiltration and the increase in proinflammatory Th1 cytokine levels. This further supports the hypothesis that DCs may exert a protective role against diabetes development.

We developed an immunohistochemical assay specific for cyclin D1 and suitable for formalin-fixed and paraffin-embedded sections, to evaluate cyclin D1 expression in a group of 135 surgically resected lung-cancer patients for the purpose of investigating the prognostic role of this protein in lung cancer. In addition, we compared cyclin D1 expression with the expression of proliferating cell nuclear antigen (PCNA), considered to be a reliable index of the proliferation rate. We found cyclin D1 expressed in more than 60% of the neoplastic cells in 26.5% of our specimens. A total of 24.5% of the specimens showed cyclin D1 expression in a percentage of cells ranging from 30 to 60%; 36.7% of the specimens expressed cyclin D1 in less than 30% of the cells; and 12.2% of the specimens expressed cyclin D1 in less than 1% of the evaluated cells. Western blot analyses confirmed the specificity of this assay by correlating statistically in a highly significant fashion with the immunohistochemical results (P = 0.0003). Furthermore, we found a direct relationship between cyclin D1 and PCNA immunodetection (P = 0.0004), which correlated cyclin D1 overexpression with a higher tumor proliferation rate. When we analyzed our data statistically, cyclin D1 expression was found to be a negative prognostic marker (P < 0.00005) whose expression correlates with a shorter patient survival time.

CDK9 has been recently shown to have increased kinase activity in differentiated cells in culture and a differentiated tissue-specific expression in the developing mouse. In order to identify factors that contribute to CDK9's differentiation-specific function, we screened a mouse embryonic library in the yeast two-hybrid system and found a tumor necrosis factor signal transducer, TRAF2, to be an interacting protein. CDK9 interacts with a conserved domain in the TRAF-C region of TRAF2, a motif that is known to bind other kinases involved in TRAF-mediated signaling. Endogenous interaction between the two proteins appears to be specific to differentiated tissue. TRAF2-mediated signaling may incorporate additional kinases to signal cell survival in myotubes, a cell type that is severely affected in TRAF2 knockout mice.

The cdc2-family of serine/threonine kinases and their binding partners recently were implicated in developmental roles. We previously cloned a cdc2-related kinase, cdk9/PITALRE, that is able to phosphorylate the retinoblastoma protein in vitro. We describe here the cloning and the characterization of the mouse homolog of cdk9/PITALRE. The murine cDNA is 98% identical with humans and is expressed at high levels in brain and kidney tissues. The kinase activity and protein expression of cdk9/PITALRE were highest in terminally differentiated tissues such as the muscle and brain. In situ immunohistology and immunofluorescence detected cdk9/PITALRE protein not only within terminally differentiated cells such as muscle and neuronal cells, but also in proliferating cells. C2C12 and P19 cells induced to differentiate along muscle and neural lineages peaked in cdk9/PITALRE kinase activity at the end of differentiation. These results suggest that, among other roles, cdk9/PITALRE plays a role not unlike cdk5 in the differentiation of certain cell types. J. Cell. Physiol. 177:206–213, 1998. © 1998 Wiley-Liss, Inc.

Neuroblastoma cells can undergo neural differentiation upon treatment with a variety of chemical inducers and growth factors. During this process, many cell cycle-related genes are downregulated while differentiation-specific genes are triggered. The retinoblastoma family proteins, pRb, p107, and pRb2/p130, are involved in transcriptional repression of proliferation genes, mainly through their interaction with the E2F transcription factors. We report that pRb2/p130 expression levels increased during differentiation of neuroblastoma cell line LAN-5. On the other hand, both pRb and p107 decreased and underwent progressive dephosphorylation at late differentiation times. The expression of B-myb and c-myb, two targets of the retinoblastoma family proteins, were downregulated in association with the increase of pRb2/p130, which was detected as the major component of the complex with E2F on the E2F site of the B-myb promoter in differentiated cells. Interestingly, E2F4, a preferential partner of p107 and pRb2/p130, was upregulated and underwent changes in cellular localization during differentiation. In conclusion, our data suggest a major role of pRb2/p130 in the regulation of B-myb promoter during neural differentiation despite the importance of cofactors in modulating the function of the retinoblastoma family proteins.

The histone H4 gene promoter provides a paradigm for defining transcriptional control operative at the G1/S phase transition point in the cell cycle. Transcription of the cell cycle-dependent histone H4 gene is upregulated at the onset of S phase, and the cell cycle control element that mediates this activation has been functionally mapped to a proximal promoter domain designated Site II. Activity of Site II is regulated by an E2F-independent mechanism involving binding of the oncoprotein IRF2 and the multisubunit protein HiNF-D, which contains the homeodomain CDP/cut, CDC2, cyclin A, and the tumor suppressor pRb. To address mechanisms that define interactions of Site II regulatory factors with this cell cycle control element, we have investigated these determinants of transcriptional regulation at the G1/S phase transition in FDC-P1 hematopoietic progenitor cells. The representation and activities of histone gene regulatory factors were examined as a function of FDC-P1 growth stimulation. We find striking differences in expression of the pRb-related growth regulatory proteins (pRb/p105, pRb2/p130, and p107) following the onset of proliferation. pRb2/p130 is present at elevated levels in quiescent cells and declines following growth stimulation. By contrast, pRb and p107 are minimally represented in quiescent FDC-P1 cells but are upregulated at the G1/S phase transition point. We also observe a dramatic upregulation of the cellular levels of pRb2/p130-associated protein kinase activity when S phase is initiated. Selective interactions of pRb and p107 with CDP/cut are observed during the FDC-P1 cell cycle and suggest functional linkage to competency for DNA binding and/or transcriptional activity. These results are particularly significant in the context of hematopoietic differentiation where stringent control of the cell cycle program is requisite for expanding the stem cell population during development and tissue renewal. J. Cell. Biochem. 66:512–523, 1997. © 1997 Wiley-Liss, Inc.

The Cdk2 kinase has long been known to be involved in the progression of mammalian cells past the G1 phase restriction point and through DNA replication in the cell cycle. The Rb family of proteins, consisting of pRb, p107, and pRb2/p130, has also been shown to monitor progression of G1 phase, mostly through their interaction with E2F family members. p107 is able to inhibit Cdk2 kinase activity through this interaction via a p21-related domain present in the C terminus of the protein. We show here that pRb2/p130 also possesses this activity, but through a separate domain. Moreover, we correlate the increased expression of pRb2/p130 during various cellular processes with the decreased kinase activity of Cdk2. We hypothesize that pRb2/p130 may act not only to bind and modify E2F activity, but also to inhibit Cdk2 kinase activity in concert with p21 in a manner different from p107.

Transgenic mice harboring the early genome from the human neurotropic JC virus, JCV, develop massive abdominal tumors of neural crest origin during 6–8 months after birth and succumb to death a few weeks later. The viral early protein, T-antigen, which possesses the ability to transform cells of neural origin, is highly expressed in the tumor cells. Immunoblot analysis of protein extract from tumor tissue shows high level expression of the tumor suppressor protein, p53, in complex with T-antigen. Expression of p21, a downstream target for p53, which controls cell cycle progression by regulating the activity of cyclins and their associated kinases during the G1 phase, is extremely low in the tumor cells. Whereas the level of expression and activity of cyclin D1 and its associated kinase, cdk6, was modest in tumor cells, both cyclin A and E, and their kinase partners, cdk2 and cdk4, were highly expressed and exhibited significant kinase activity. The retinoblastoma gene product, pRb, which upon phosphorylation by cyclins:cdk induces rapid cell proliferation, was found in the phosphorylated state in tumor cell extracts, and was detected in association with JCV T-antigen. The transcription factor, E2F-1, which dissociates from the pRb–E2F-1 complex and stimulates S phase-specific genes upon phosphorylation of pRb and/or complexation of pRb with the viral transforming protein, was highly expressed in tumor cells. Accordingly, high level expression of the E2F-1-responsive gene, proliferating cell nuclear antigen (PCNA), was detected in the tumor cells. These observations suggest a potential regulating pathway that, upon expression of JCV T-antigen, induces formation and progression of tumors of neural origin in a whole animal system. J Cell. Biochem. 67:223–230, 1997. © 1997 Wiley-Liss, Inc.

It was recently reported that B-MYB can overcome p107-induced growth arrest. Here we show that B-MYB autoregulation of its own transcription is specifically suppressed by p107 and transient transfection assays with p107 deletion constructs determined that the carboxyl terminus of the protein, containing the major pocket region, was associated with inhibition of B-MYB-dependent transactivation. Consistent with these results, co-immunoprecipitation studies showed that p107 interacted in vivo with B-MYB through its pocket and carboxyl terminus domain. Thus, B-MYB-dependent promotion of cell proliferation and gene transactivation might be specifically repressed by the growth suppressor p107 through direct interaction with B-MYB.

ets-2 is a member of a family of transcription factors implicated in the regulation of gene expression during cell proliferation, cell differentiation, and development. We report that the ets-2 protein transactivates the promoter of the cdc2 gene which encodes a 34-kDa serine-threonine kinase required for mitotic initiation in mammalian cells. Transactivation occurs via specific interaction with multiple ets binding sites in the 5′ flanking region of the gene. In BALB/c3T3 rodent fibroblasts constitutively expressing ets-2 and cultured in either 10 or 0.5% serum, cdc2 expression and its associated histone H1 kinase activity are increased, compared to control cells. Such increased activity correlates with elevated levels of cyclin A but not cyclin B1. Furthermore, ets-2-transfected, but not parental, BALB/c3T3 cells, grow under low serum conditions, albeit at a reduced rate. These data demonstrate that ets-2 plays a direct role in the regulation of cdc2 expression and raise the possibility that ets-2 participates in the coordinated regulation of cdc2 cyclin A expression which is essential for the modulation of cdc2-regulated processes.

Wolframin is a transmembrane glycoprotein of 890 aminoacids, encoded by WFS1 gene. WFS1 mutations are responsible for Wolfram syndrome, an autosomal recessive disorder. In the present paper, we first characterized the polyclonal wolframin antibody by dot blot. Secondly, we verified antibody specificity by western blotting using different human cell lines. Thirdly, we studied wolframin localization in human foetal (14-35 weeks) and adult tissues by immunohistochemistry. Wolframin expression was distributed in many organs, with different tissue and cell localization and expression levels. In foetal systems, wolframin expression was faint at 14-16 weeks and increased when development proceeded. In adult human tissues a variable positive staining was observed in both simple and stratified epithelia. A moderate wolframin expression was observed in liver and in the endocrine portion of the pancreas. In conclusion, our data suggest that this protein may have important roles in a number of different tissues, including many that are not known to be affected by WFS1-linked diseases. The immunopositivity in adult human tissues suggests that it may function maintaining physiological cellular homeostasis.