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The tandem Tudor-like domain-containing protein Spindlin1 (SPIN1) is a transcriptional coactivator with critical functions in embryonic development and emerging roles in cancer. However, the involvement of SPIN1 in DNA damage repair has remained unclear. Our study shows that SPIN1 is recruited to DNA lesions through its N-terminal disordered region that binds to Poly-ADP-ribose (PAR), and facilitates homologous recombination (HR)-mediated DNA damage repair. SPIN1 promotes H3K9me3 accumulation at DNA damage sites and enhances the interaction between H3K9me3 and Tip60, thereby promoting the activation of ATM and HR repair. We also show that SPIN1 increases chemoresistance. These findings reveal a novel role for SPIN1 in the activation of H3K9me3-dependent DNA repair pathways, and suggest that SPIN1 may contribute to cancer chemoresistance by modulating the efficiency of double-strand break (DSB) repair. Synopsis: SPIN1, a histone methylation reader with diverse biological functions, has been implicated in tumor formation and growth. This study uncovers SPIN1's function in promoting chemoresistance and homologous recombination (HR) repair by enhancing Tip60 binding to H3K9me3. SPIN1 is rapidly recruited to DNA damage sites through direct binding to PAR. SPIN1 facilitates the accumulation of H3K9me3 at DNA damage sites, promoting the interaction between H3K9me3 and Tip60, leading to enhanced ATM activation and HR repair. SPIN1 increases chemoresistance both in vivo and in vitro. SPIN1, a histone methylation reader with diverse biological functions, has been implicated in tumor formation and growth. This study uncovers SPIN1's function in promoting chemoresistance and homologous recombination (HR) repair by enhancing Tip60 binding to H3K9me3. [ABSTRACT FROM AUTHOR]

Proper function of the centromeres ensures correct attachment of kinetochores to spindle microtubules and faithful chromosome segregation in mitosis. Defects in the integrity and function of centromeres can result in chromosome missegregation and genomic instability. Bub1 is essential for the mitotic centromere dynamics, yet the underlying molecular mechanisms remain largely unclear. Here, we demonstrate that TIP60 acetylates Bub1 at K424 and K431 on kinetochores in early mitosis. This acetylation increases the kinase activity of Bub1 to phosphorylate centromeric histone H2A at T120 (H2ApT120), which recruits Aurora B and Shugoshin 1 (Sgo1) to regulate centromere integrity, protect centromeric cohesion, and ensure the subsequent faithful chromosome segregation. Expression of the non-acetylated Bub1 mutant reduces its kinase activity, decreases the level of H2ApT120, and disrupts the recruitment of centromere proteins and chromosome congression, leading to genomic instability of daughter cells. When cells exit mitosis, HDAC1-regulated deacetylation of Bub1 decreases H2ApT120 levels and thereby promotes the departure of centromeric CPC and Sgo1, ensuring timely centromeres disassembly. Collectively, our results reveal a molecular mechanism by which the acetylation and deacetylation cycle of Bub1 modulates the phosphorylation of H2A at T120 for recruitment of Aurora B and Sgo1 to the centromeres, ensuring faithful chromosome segregation during mitosis. [ABSTRACT FROM AUTHOR]

Simple Summary: Individualized medicine means understanding how each tumor is different from normal cells and how each tumor is different from other tumors, including profiling mutations, non-mutational epigenetic changes, and differences in gene expression. This allows the discovery of key processes each tumor absolutely depends on for survival and growth, which are intrinsic weaknesses. This profiling means selecting treatments to specifically target each tumor's survival-dependent pathways, killing them. Tip60 is a master controller of processes that maintain genome stability and signaling regulating gene expression. While disrupted in many cancers, Tip60 is essential for cell survival, and inhibiting Tip60 kills tumors. While we understand some key aspects of the molecular roles Tip60 plays, much more remains to be discovered. A more complete understanding of the diverse roles and functions of Tip60 in cancer, and how targeting Tip60 kills cancer cells, will lead to better treatments for patients and increased survival. Precision (individualized) medicine relies on the molecular profiling of tumors' dysregulated characteristics (genomic, epigenetic, transcriptomic) to identify the reliance on key pathways (including genome stability and epigenetic gene regulation) for viability or growth, and then utilises targeted therapeutics to disrupt these survival-dependent pathways. Non-mutational epigenetic changes alter cells' transcriptional profile and are a key feature found in many tumors. In contrast to genetic mutations, epigenetic changes are reversable, and restoring a normal epigenetic profile can inhibit tumor growth and progression. Lysine acetyltransferases (KATs or HATs) protect genome stability and integrity, and Tip60 is an essential acetyltransferase due to its roles as an epigenetic and transcriptional regulator, and as master regulator of the DNA double-strand break response. Tip60 is commonly downregulated and mislocalized in many cancers, and the roles that mislocalized Tip60 plays in cancer are not well understood. Here we categorize and discuss Tip60-regulated genes, evaluate Tip60-interacting proteins based on cellular localization, and explore the therapeutic potential of Tip60-targeting compounds as epigenetic inhibitors. Understanding the multiple roles Tip60 plays in tumorigenesis will improve our understanding of tumor progression and will inform therapeutic options, including informing potential combinatorial regimes with current chemotherapeutics, leading to improvements in patient outcomes. [ABSTRACT FROM AUTHOR]

Histone modifications play crucial roles in transcriptional activation, and aberrant epigenetic changes are associated with oncogenesis. Lysine (K) acetyltransferases 5 (TIP60, also known as KAT5) is reportedly implicated in cancer development and maintenance, although its function in lung cancer remains controversial. Here we demonstrate that TIP60 knockdown in non-small cell lung cancer cell lines decreased tumor cell growth, migration, and invasion. Furthermore, analysis of a mouse lung cancer model with lung-specific conditional Tip60 knockout revealed suppressed tumor formation relative to controls, but no apparent effects on normal lung homeostasis. RNA-seq and ChIP-seq analyses of inducible TIP60 knockdown H1975 cells relative to controls revealed transglutaminase enzyme (TGM5) as downstream of TIP60. Investigation of a connectivity map database identified several candidate compounds that decrease TIP60 mRNA, one that suppressed tumor growth in cell culture and in vivo. In addition, TH1834, a TIP60 acetyltransferase inhibitor, showed comparable antitumor effects in cell culture and in vivo. Taken together, suppression of TIP60 activity shows tumor-specific efficacy against lung cancer, with no overt effect on normal tissues. Our work suggests that targeting TIP60 could be a promising approach to treating lung cancer.

Since patients with triple-negative breast cancer do not respond to hormone therapy, the main treatment method is the combination of chemotherapy and radiotherapy. Because the DNA of the tumor cell is the target in both some chemotherapeutics and radiotherapy, problems may occur in individuals with a high DNA repair pathway. It is suggested that high expression of the Tip60 gene, which has an important role in repairing DNA damage, will increase the repair of DNA double-strand breaks in tumor cells, especially during radiotherapy treatment, thus reducing the response to treatment and adversely affecting treatment. In this study, for the first time, the role of the silenced and active Tip60 gene in response to radiotherapy in MDA-MB-231 and MCF-7 cells was investigated. For this purpose, the Tip60 gene was silenced by applying siRNA to the cell lines and UV was applied. In the study, cytotoxicity and DNA breaks were measured by MTT and COMET methods, and mRNA and protein expression values were measured by PCR and Raman spectrophotometer in silenced, unsilenced, UV-treated, and non-UV-treated cell lines. According to the results of the study, increased DNA damage was observed in MCF-7 cell lines in which the Tip60 gene was silenced, and radiotherapy was applied, compared to the cell lines with the Tip60 gene active. It was observed that DNA damage in MDA-MB-231 cell lines was less than in cell lines with the active Tip60 gene.

TWIST1 induces epithelial‐to‐mesenchymal transition (EMT) to drive cancer metastasis. It is yet unclear what determines TWIST1 functions to activate or repress transcription. We found that the TWIST1 N‐terminus antagonizes TWIST1‐regulated gene expression, cancer growth and metastasis. TWIST1 interacts with both the NuRD complex and the NuA4/TIP60 complex (TIP60‐Com) via its N‐terminus. Non‐acetylated TWIST1‐K73/76 selectively interacts with and recruits NuRD to repress epithelial target gene transcription. Diacetylated TWIST1‐acK73/76 binds BRD8, a component of TIP60‐Com that also binds histone H4‐acK5/8, to recruit TIP60‐Com to activate mesenchymal target genes and MYC. Knockdown of BRD8 abolishes TWIST1 and TIP60‐Com interaction and TIP60‐Com recruitment to TWIST1‐activated genes, resulting in decreasing TWIST1‐activated target gene expression and cancer metastasis. Both TWIST1/NuRD and TWIST1/TIP60‐Com complexes are required for TWIST1 to promote EMT, proliferation, and metastasis at full capacity. Therefore, the diacetylation status of TWIST1‐K73/76 dictates whether TWIST1 interacts either with NuRD to repress epithelial genes, or with TIP60‐Com to activate mesenchymal genes and MYC. Since BRD8 is essential for TWIST1‐acK73/76 and TIP60‐Com interaction, targeting BRD8 could be a means to inhibit TWIST1‐activated gene expression. Synopsis: Non‐acetylated TWIST1 induces EMT and metastasis by interacting with the NuRD complex to repress epithelial genes. Diacetylated TWIST1 interacts with BRD8 in the NuA4/TIP60 complex to activate MYC and mesenchymal genes. TWIST1 has a non‐acetylated and a diacetylated form, which interacts with the NuRD and the TIP60 complex, respectively.TWIST1–NuRD represses epithelial target genes. TWIST1‐acK73/K76–TIP60 activates mesenchymal target genes.TWIST1 requires both of these transcriptional activities to fully induce breast cancer cell growth, EMT and metastasis.TWIST1‐N competes with TWIST1 for TIP60 and NuRD binding, thereby inhibiting TWIST1‐induced EMT and metastasis. [ABSTRACT FROM AUTHOR]

Since patients with triple-negative breast cancer do not respond to hormone therapy, the main treatment method is the combination of chemotherapy and radiotherapy. Because the DNA of the tumor cell is the target in both some chemotherapeutics and radiotherapy, problems may occur in individuals with a high DNA repair pathway. It is suggested that high expression of the Tip60 gene, which has an important role in repairing DNA damage, will increase the repair of DNA double-strand breaks in tumor cells, especially during radiotherapy treatment, thus reducing the response to treatment and adversely affecting treatment. In this study, for the first time, the role of the silenced and active Tip60 gene in response to radiotherapy in MDA-MB-231 and MCF-7 cells was investigated. For this purpose, the Tip60 gene was silenced by applying siRNA to the cell lines and UV was applied. In the study, cytotoxicity and DNA breaks were measured by MTT and COMET methods, and mRNA and protein expression values were measured by PCR and Raman spectrophotometer in silenced, unsilenced, UV-treated, and non-UV-treated cell lines. According to the results of the study, increased DNA damage was observed in MCF-7 cell lines in which the Tip60 gene was silenced, and radiotherapy was applied, compared to the cell lines with the Tip60 gene active. It was observed that DNA damage in MDA-MB-231 cell lines was less than in cell lines with the active Tip60 gene. • TNBC is with a heterogeneous tumor structure, exhibits different biological behaviors, and has multiple molecular subtypes. • One of the most important problems encountered in chemotherapy and radiotherapy treatment is that the tumor tissue does not respond to treatment at all or less. • The combination of chemotherapy and radiotherapy may be a problem in individuals with highly active DNA repair pathways. • The over-expression of Tip60 may affect the treatment by repairing DNA damage in tumor cells, especially in response to radiotherapy, during the treatment stages of cancer. [ABSTRACT FROM AUTHOR]

ATP-dependent chromatin remodeling complexes are involved in nucleosome sliding and eviction and/or the incorporation of histone variants into chromatin to facilitate several cellular and biological processes, including DNA transcription, replication and repair. The DOM/TIP60 chromatin remodeling complex of Drosophila melanogaster contains 18 subunits, including the DOMINO (DOM), an ATPase that catalyzes the exchange of the canonical H2A with its variant (H2A.V), and TIP60, a lysine-acetyltransferase that acetylates H4, H2A and H2A.V histones. In recent decades, experimental evidence has shown that ATP-dependent chromatin remodeling factors, in addition to their role in chromatin organization, have a functional relevance in cell division. In particular, emerging studies suggested the direct roles of ATP-dependent chromatin remodeling complex subunits in controlling mitosis and cytokinesis in both humans and D. melanogaster. However, little is known about their possible involvement during meiosis. The results of this work show that the knockdown of 12 of DOM/TIP60 complex subunits generates cell division defects that, in turn, cause total/partial sterility in Drosophila males, providing new insights into the functions of chromatin remodelers in cell division control during gametogenesis. [ABSTRACT FROM AUTHOR]

The severity of Alzheimer's disease (AD) progression involves a complex interplay of genetics, age, and environmental factors orchestrated by histone acetyltransferase (HAT)-mediated neuroepigenetic mechanisms. While disruption of Tip60 HAT action in neural gene control is implicated in AD, alternative mechanisms underlying Tip60 function remain unexplored. Here, we report a novel RNA binding function for Tip60 in addition to its HAT function. We show that Tip60 preferentially interacts with pre-mRNAs emanating from its chromatin neural gene targets in the Drosophila brain and this RNA binding function is conserved in human hippocampus and disrupted in Drosophila brains that model AD pathology and in AD patient hippocampus of either sex. Since RNA splicing occurs co-transcriptionally and alternative splicing (AS) defects are implicated in AD, we investigated whether Tip60- RNA targeting modulates splicing decisions and whether this function is altered in AD. Replicate multivariate analysis of transcript splicing (rMATS) analysis of RNA-Seq datasets from wild-type and AD fly brains revealed a multitude of mammalian-like AS defects. Strikingly, over half of these altered RNAs are identified as bona-fide Tip60-RNA targets that are enriched for in the AD-gene curated database, with some of these AS alterations prevented against by increasing Tip60 in the fly brain. Further, human orthologs of several Tip60-modulated splicing genes in Drosophila are well characterized aberrantly spliced genes in human AD brains, implicating disruption of Tip60's splicing function in AD pathogenesis. Our results support a novel RNA interaction and splicing regulatory function for Tip60 that may underly AS impairments that hallmark AD etiology. [ABSTRACT FROM AUTHOR]

H2AX is a histone H2A variant that becomes phosphorylated upon genotoxic stress. The phosphorylated H2AX (γ‐H2AX) plays an antioncogenic role in the DNA damage response and its foci patterns are highly variable, in terms of intensities and sizes. However, whether characteristic γ‐H2AX foci patterns are associated with oncogenesis (oncogenic‐specific γ‐H2AX foci patterns) remains unknown. We previously reported that a defect in the acetyltransferase activity of TIP60 promotes cancer cell growth in human cell lines. In this study, we compared γ‐H2AX foci patterns between TIP60 wild‐type cells and TIP60 HAT mutant cells by using machine learning. When focused solely on the intensity and size of γ‐H2AX foci, we extracted the TIP60 HAT mutant‐like oncogenic‐specific γ‐H2AX foci pattern among all datasets of γ‐H2AX foci patterns. Furthermore, by using the dimensionality reduction method UMAP, we also observed TIP60 HAT mutant‐like oncogenic‐specific γ‐H2AX foci patterns in TIP60 wild‐type cells. In summary, we propose the existence of an oncogenic‐specific γ‐H2AX foci pattern and the importance of a machine learning approach to extract oncogenic signaling among the γ‐H2AX foci variations. [ABSTRACT FROM AUTHOR]

The accessibility of DNA to different cellular functions requires a dynamic regulation of chromatin organization that is mediated by different epigenetic modifications, which regulate chromatin accessibility and degree of compaction. These epigenetic modifications, particularly the acetylation of histone H4 in lysine 14 (H4K16ac), determine the degree of chromatin accessibility to different nuclear functions, as well as to DNA damage drugs. H4K16ac is regulated by the balance between two alternative histone modifications, acetylation and deacetylation, which are mediated by acetylases and deacetylases. Tip60/KAT5 acetylates, and SIRT2 deacetylates histone H4K16. However, the balance between these two epigenetic enzymes is unknown. VRK1 regulates the level of H4K16 acetylation by activating Tip60. We have shown that the VRK1 and SIRT2 are able to form a stable protein complex. For this work, we used in vitro interaction, pull-down and in vitro kinase assays. In cells, their interaction and colocalization were detected by immunoprecipitation and immunofluorescence. The kinase activity of VRK1 is inhibited by a direct interaction of its N-terminal kinase domain with SIRT2 in vitro. This interaction causes a loss of H4K16ac similarly to the effect of a novel VRK1 inhibitor (VRK-IN-1) or VRK1 depletion. The use of specific SIRT2 inhibitors in lung adenocarcinoma cells induces H4K16ac, contrary to the novel VRK-IN-1 inhibitor, which prevents H4K16ac and a correct DNA damage response. Therefore, the inhibition of SIRT2 can cooperate with VRK1 in the accessibility of drugs to chromatin in response to DNA damage caused by doxorubicin. [ABSTRACT FROM AUTHOR]

NAD+ synthesis is a fundamental process in living cells. The effects of local metabolite production on chromatin influence the epigenetic status of chromatin in DNA metabolism. We have previously shown that K5 acetylation of H2AX by TIP60 is required for the ADP ribosylation activity of PARP-1, for histone H2AX exchange at DNA damage sites. However, the detailed molecular mechanism has remained unclear. Here, we identified de novo NAD synthetase 1 (NAD syn1) as a novel binding partner to H2AX. The enzymatic activity of NAD syn1 is crucial for the ADP ribosylation activity of PARP-1 for the H2AX dynamics at sites of DNA damage. Inhibition of the NAD synthetase activity in the cell nucleus decreased the overall cellular NAD+ concentration, leading to cellular senescence. Accordingly, the acetylation-dependent H2AX dynamics and homologous recombination repair were suppressed, leading to increased tumorigenesis. Our findings have revealed the importance of de novo NAD+ production in the cell nucleus for protection against the decreased DNA repair capacity caused by cellular senescence and thus against tumorigenesis. [ABSTRACT FROM AUTHOR]

Paclitaxel (PTX) is one of the most efficient drugs for late-stage non-small cell lung cancer (NSCLC) patients. However, most patients gradually develop resistance to PTX with long-term treatments. The identification of new strategies to reverse PTX resistance in NSCLC is crucially important for the treatment. PTX is an agonist for the pregnane X receptor (PXR) which regulates PTX metabolism. Antagonizing PXR, therefore, may render the NSCLC more sensitive to the PTX treatment. In this study, we investigated the PXR antagonist SPA70 and its role in PTX treatment of NSCLC. In vitro, SPA70 and PTX synergistically inhibited cell growth, migration and invasion in both paclitaxel-sensitive and paclitaxel-resistant A549 and H460 lung cancer cells. Mechanistically, we found PTX and SPA70 cotreatment disassociated PXR from ABCB1 (MDR1, P-gp) promoter, thus inhibiting P-gp expression. Furthermore, the combination regimen synergistically enhanced the interaction between PXR and Tip60, which abrogated Tip60-mediated α-tubulin acetylation, leading to mitosis defect, S-phase arrest and necroptosis/apoptosis. Combination of PXT and SPA70 dramatically inhibited tumor growth in a paclitaxel-resistant A549/TR xenograft tumor model. Taken together, we showed that SPA70 reduced the paclitaxel resistance of NSCLC. The combination regimen of PTX and SPA70 could be potential novel candidates for the treatment of taxane-resistant lung cancer. [ABSTRACT FROM AUTHOR]

Objective: The hyperphosphorylation of Tau protein is considered an important cause of neuronal degeneration in Alzheimer's disease (AD). The disruption of neuronal histone acetylation homeostasis mediated by Tip60 HAT is a common early event in neurodegenerative diseases, but the deeper regulatory mechanism on β-amyloid peptide (Aβ)-induced neurotoxicity and autophagic function in AD is still unclear., Methods: AD models were established both in APP/PS1 mice and Aβ 1-42 -treated SH-SY5Y cells. The Morris water maze test (MWM) was performed to examine mouse cognitive function. Neurological damage in the hippocampus was observed by hematoxylin-eosin (H&E), Nissl's, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and NeuN staining. Autophagosome-lysosome fusion was detected by immunohistochemistry, immunofluorescence, and Lyso-Tracker Red staining. Cell viability and apoptosis were evaluated by CCK-8 assay and flow cytometry. The molecular interactions were verified by co-immunoprecipitation (Co-IP), dual luciferase assays, and ChIP detections. The RNA and autophagy-lysosome-related proteins were assessed by Western blot and RT-qPCR., Results: TIP60 overexpression improved cognitive deficits and neurological damage and restored the impairment of autophagy-lysosomes fusion in vivo. Similarly, the upregulation of TIP60 in Aβ 1-42 -treated SH-SY5Y cells suppressed neuronal apoptosis and tau phosphorylation through the activating autophagy-lysosome pathway. Mechanistically, TIP60 activated IKKβ transcription by promoting SOX4 acetylation, thus leading to the translocation of SNAP23 to STX17-contained autophagosomes. Moreover, the protective roles of TIP60 in neuron damage were abolished by the inhibition of SOX4/IKKβ signaling., Conclusion: Collectively, our results highlighted the potential of the TIP60 target for AD and provided new insights into the mechanisms underlying neuroprotection in this disorder., (© 2024 The Author(s). CNS Neuroscience & Therapeutics published by John Wiley & Sons Ltd.)

Stable transmission of genetic information during cell division requires faithful mitotic spindle assembly and chromosome segregation. In eukaryotic cells, nuclear envelope breakdown (NEBD) is required for proper chromosome segregation. Although a list of mitotic kinases has been implicated in NEBD, how they coordinate their activity to dissolve the nuclear envelope and protein machinery such as nuclear pore complexes was unclear. Here, we identified a regulatory mechanism in which Nup62 is acetylated by TIP60 in human cell division. Nup62 is a novel substrate of TIP60, and the acetylation of Lys432 by TIP60 dissolves nucleoporin Nup62–Nup58–Nup54 complex during entry into mitosis. Importantly, this acetylation-elicited remodeling of nucleoporin complex promotes the distribution of Nup62 to the mitotic spindle, which is indispensable for orchestrating correct spindle orientation. Moreover, suppression of Nup62 perturbs accurate chromosome segregation during mitosis. These results establish a previously uncharacterized regulatory mechanism in which TIP60-elicited nucleoporin dynamics promotes chromosome segregation in mitosis. [ABSTRACT FROM AUTHOR]

The development and growth of a normal prostate gland, as well as its physiological functions, are regulated by the actions of androgens through androgen receptor (AR) signaling which drives multiple cellular processes including transcription, cellular proliferation, and apoptosis in prostate cells. Post-translational regulation of AR plays a vital role in directing its cellular activities via modulating its stability, nuclear localization, and transcriptional activity. Among various post-translational modifications (PTMs), acetylation is an essential PTM recognized in AR and is governed by the regulated actions of acetyltransferases and deacetyltransferases. Acetylation of AR has been identified as a critical step for its activation and depending on the site of acetylation, the intracellular dynamics and activity of the AR can be modulated. Various acetyltransferases such as CBP, p300, PCAF, TIP60, and ARD1 that are known to acetylate AR, may directly coactivate the AR transcriptional function or help to recruit additional coactivators to functionally regulate the transcriptional activity of the AR. Aberrant expression of acetyltransferases and their deregulated activities have been found to interfere with AR signaling and play a key role in development and progression of prostatic diseases, including prostate cancer (PCa). In this review, we summarized recent research advances aimed at understanding the role of various lysine acetyltransferases (KATs) in the regulation of AR activity at the level of post-translational modifications in normal prostate physiology, as well as in development and progression of PCa. Considering the critical importance of KATs in modulating AR activity in physiological and patho-physiological context, we further discussed the potential of targeting these enzymes as a therapeutic option to treat AR-related pathology in combination with hormonal therapy.

Summary: A recurrent chromosomal translocation found in acute myeloid leukemia leads to an in-frame fusion of the transcription repressor ZMYND11 to MBTD1, a subunit of the NuA4/TIP60 histone acetyltransferase complex. To understand the abnormal molecular events that ZMYND11-MBTD1 expression can create, we perform a biochemical and functional characterization comparison to each individual fusion partner. ZMYND11-MBTD1 is stably incorporated into the endogenous NuA4/TIP60 complex, leading to its mislocalization on the body of genes normally bound by ZMYND11. This can be correlated to increased chromatin acetylation and altered gene transcription, most notably on the MYC oncogene, and alternative splicing. Importantly, ZMYND11-MBTD1 expression favors Myc-driven pluripotency during embryonic stem cell differentiation and self-renewal of hematopoietic stem/progenitor cells. Altogether, these results indicate that the ZMYND11-MBTD1 fusion functions primarily by mistargeting the NuA4/TIP60 complex to the body of genes, altering normal transcription of specific genes, likely driving oncogenesis in part through the Myc regulatory network.

Background: Asthma serves as a chronic inflammatory respiratory diseases disorder. It mainly occurs airway inflammation and remodeling. Circular RNA (circRNA) is mainly the control of cancer disease and asthma. In specific work, we were interested in the function of circRHOT1 in the advances in asthma. Methods: Effects of platelet-derived growth factor BB (PDGF-BB) on airway smooth muscle cells (ASMCs) and remolded simulation cells were assessed. The expressions of circRHOT1, TLR4, and Tip60 were detected by qRT-PCR and the increase and decrease of cell number were analyzed by cell count-8 (CCK-8), Transwell or flow cytometry. At the same time, the levels of PCNA, IGF1R protein were determined by western blot approach. The correlation of circRHOT1, TLR4, and Tip60 was analyzed by qRT-PCR, western blotting, ChIP, and RNA pulldown. Results: CircRHOT1 was significantly elevated in the serum collected from asthmatic patients. PDGF-BB had a positive effect on ASMCs with enhanced levels of circRHOT1, TLR4, and Tip60. Depletion of circRHOT1 avoided wider impact and migration but induced cell apoptosis. CircRHOT1 contributed PDGF-BB had a direct impact on the proliferation and migration of ASMCs by regulating TLR4. Mechanically, circRHOT1 could cooperate with acetyltransferase Tip60 in ASMCs. CircRHOT1 silencing was easy to have an adverse effect on the enrichment of Tip60 on TLR4 promoter in ASMCs. The depletion of circRHOT1 or Tip60 reduced h3k27ac and RNA polymerase II on the TLR4 promoter. Consistently, the inhibition of circRHOT1 or Tip60 reduced TLR4 expression in ASMCs. The deletion of circRHOT1 could reduce the expression level of TLR4, but the overexpression of Tip60 was easy to have a positive effect on the down-regulation of ASMCs. In addition, Tip60 could inhibit ASMCs proliferation and migration caused by PDGF-BB stimulation. CircRHOT1 could use PDGF-BB to stimulate ASMCs proliferation and migration when Tip60 regulation was implemented. Conclusions: We can think that based on the related effects of Tip60/TLR4, circular RNA circRHOT1 with platelet-derived growth factor BB can stimulate airway smooth muscle cells to proliferate or migrate, and circRHOT1 is an important target for the treatment of asthma.

The repair of DNA breaks takes place in the context of chromatin and thus involves the activity of chromatin remodelers. The nucleosome acetyltransferase of H4 (NuA4) remodeler complex enables DNA break repair by relaxing flanking chromatin. Here, we show that MRG domain binding protein (MRGBP), a member of this complex, acts as a general inhibitor of DNA double‐strand break repair. Upon its downregulation, repair is generally increased. This is particularly evident for the stimulation of early events of homologous recombination. Thus, MRGBP has an opposing role to the main catalytic subunits of the NuA4 complex. Our data suggest that MRGBP acts by limiting the activity of this complex in DNA repair, specifically by narrowing the extent of DNA‐end resection.

ATP-dependent chromatin remodeling complexes are involved in nucleosome sliding and eviction and/or the incorporation of histone variants into chromatin to facilitate several cellular and biological processes, including DNA transcription, replication and repair. The DOM/TIP60 chromatin remodeling complex of Drosophila melanogaster contains 18 subunits, including the DOMINO (DOM), an ATPase that catalyzes the exchange of the canonical H2A with its variant (H2A.V), and TIP60, a lysine-acetyltransferase that acetylates H4, H2A and H2A.V histones. In recent decades, experimental evidence has shown that ATP-dependent chromatin remodeling factors, in addition to their role in chromatin organization, have a functional relevance in cell division. In particular, emerging studies suggested the direct roles of ATP-dependent chromatin remodeling complex subunits in controlling mitosis and cytokinesis in both humans and D. melanogaster. However, little is known about their possible involvement during meiosis. The results of this work show that the knockdown of 12 of DOM/TIP60 complex subunits generates cell division defects that, in turn, cause total/partial sterility in Drosophila males, providing new insights into the functions of chromatin remodelers in cell division control during gametogenesis.

Casein kinase 1δ/ϵ (CK1δ/ϵ) are well-established positive modulators of the Wnt/β-catenin signaling pathway. However, the molecular mechanisms involved in the regulation of β-catenin transcriptional activity by CK1δ/ϵ remain unclear. In this study, we found that CK1δ/ϵ could enhance β-catenin-mediated transcription through regulating β-catenin acetylation. CK1δ/ϵ interacted with Tip60 and facilitated the recruitment of Tip60 to β-catenin complex, resulting in increasing β-catenin acetylation at K49. Importantly, Tip60 significantly enhanced the SuperTopFlash reporter activity induced by CK1δ/ϵ or/and β-catenin. Furthermore, a CK1δ/CK1ϵ/β-catenin/Tip60 complex was detected in colon cancer cells. Simultaneous knockdown of CK1δ and CK1ϵ significantly attenuated the interaction between β-catenin and Tip60. Notably, inhibition of CK1δ/ϵ or Tip60, with shRNA or small molecular inhibitors downregulated the level of β-catenin acetylation at K49 in colon cancer cells. Finally, combined treatment with CK1 inhibitor SR3029 and Tip60 inhibitor MG149 had more potent inhibitory effect on β-catenin acetylation, the transcription of Wnt target genes and the viability and proliferation in colon cancer cells. Taken together, our results revealed that the transcriptional activity of β-catenin could be modulated by the CK1δ/ϵ-β-catenin-Tip60 axis, which may be a potential therapeutic target for colon cancer. [ABSTRACT FROM AUTHOR]

Casein kinase 1δ/ϵ (CK1δ/ϵ) are well-established positive modulators of the Wnt/β-catenin signaling pathway. However, the molecular mechanisms involved in the regulation of β-catenin transcriptional activity by CK1δ/ϵ remain unclear. In this study, we found that CK1δ/ϵ could enhance β-catenin-mediated transcription through regulating β-catenin acetylation. CK1δ/ϵ interacted with Tip60 and facilitated the recruitment of Tip60 to β-catenin complex, resulting in increasing β-catenin acetylation at K49. Importantly, Tip60 significantly enhanced the SuperTopFlash reporter activity induced by CK1δ/ϵ or/and β-catenin. Furthermore, a CK1δ/CK1ϵ/β-catenin/Tip60 complex was detected in colon cancer cells. Simultaneous knockdown of CK1δ and CK1ϵ significantly attenuated the interaction between β-catenin and Tip60. Notably, inhibition of CK1δ/ϵ or Tip60, with shRNA or small molecular inhibitors downregulated the level of β-catenin acetylation at K49 in colon cancer cells. Finally, combined treatment with CK1 inhibitor SR3029 and Tip60 inhibitor MG149 had more potent inhibitory effect on β-catenin acetylation, the transcription of Wnt target genes and the viability and proliferation in colon cancer cells. Taken together, our results revealed that the transcriptional activity of β-catenin could be modulated by the CK1δ/ϵ-β-catenin-Tip60 axis, which may be a potential therapeutic target for colon cancer.

T regulatory cells suppress a variety of immune responses to self-antigens and play a role in peripheral tolerance maintenance by limiting autoimmune disorders, and other pathological immune responses such as limiting immune reactivity to oncoprotein encoded antigens. Forkhead box P3 (FOXP3) expression is required for Treg stability and affects functional activity. Mutations in the master regulator FOXP3 and related components have been linked to autoimmune diseases in humans, such as IPEX, and a scurfy-like phenotype in mice. Several lines of evidence indicate that Treg use a variety of immunosuppressive mechanisms to limit an immune response by targeting effector cells, including secretion of immunoregulatory cytokines, granzyme/perforin-mediated cell cytolysis, metabolic perturbation, directing the maturation and function of antigen-presenting cells (APC) and secretion of extracellular vesicles for the development of immunological tolerance. In this review, several regulatory mechanisms have been highlighted and discussed. [ABSTRACT FROM AUTHOR]

Negatively-supercoiled-ds DNA molecules, including the genomes of baculoviruses, spontaneously wrap around cores of histones to form nucleosomes when present within eukaryotic nuclei. Hence, nucleosome management should be essential for baculovirus genome replication and temporal regulation of transcription, but this has not been documented. Nucleosome mobilization is the dominion of ATP-dependent chromatin-remodeling complexes. SWI/SNF and INO80, two of the best-studied complexes, as well as chromatin modifier TIP60, all contain actin as a subunit. Retrospective analysis of results of AcMNPV time course experiments wherein actin polymerization was blocked by cytochalasin D drug treatment implicate actin-containing chromatin modifying complexes in decatenating baculovirus genomes, shutting down host transcription, and regulating late and very late phases of viral transcription. Moreover, virus-mediated nuclear localization of actin early during infection may contribute to nucleosome management.

T regulatory cells suppress a variety of immune responses to self-antigens and play a role in peripheral tolerance maintenance by limiting autoimmune disorders, and other pathological immune responses such as limiting immune reactivity to oncoprotein encoded antigens. Forkhead box P3 (FOXP3) expression is required for Treg stability and affects functional activity. Mutations in the master regulator FOXP3 and related components have been linked to autoimmune diseases in humans, such as IPEX, and a scurfy-like phenotype in mice. Several lines of evidence indicate that Treg use a variety of immunosuppressive mechanisms to limit an immune response by targeting effector cells, including secretion of immunoregulatory cytokines, granzyme/perforin-mediated cell cytolysis, metabolic perturbation, directing the maturation and function of antigen-presenting cells (APC) and secretion of extracellular vesicles for the development of immunological tolerance. In this review, several regulatory mechanisms have been highlighted and discussed.

The effects of genotoxic stress can be mediated by activation of the Ataxia Telangiectasia Mutated (ATM) kinase, under both DNA damage-dependent (including ionizing radiation), and independent (including hypoxic stress) conditions. ATM activation is complex, and primarily mediated by the lysine acetyltransferase Tip60. Epigenetic changes can regulate this Tip60-dependent activation of ATM, requiring the interaction of Tip60 with tri-methylated histone 3 lysine 9 (H3K9me3). Under hypoxic stress, the role of Tip60 in DNA damage-independent ATM activation is unknown. However, epigenetic changes dependent on the methyltransferase Suv39H1, which generates H3K9me3, have been implicated. Our results demonstrate severe hypoxic stress (0.1% oxygen) caused ATM auto-phosphorylation and activation (pS1981), H3K9me3, and elevated both Suv39H1 and Tip60 protein levels in FTC133 and HCT116 cell lines. Exploring the mechanism of ATM activation under these hypoxic conditions, siRNA-mediated Suv39H1 depletion prevented H3K9me3 induction, and Tip60 inhibition (by TH1834) blocked ATM auto-phosphorylation. While MDM2 (Mouse double minute 2) can target Suv39H1 for degradation, it can be blocked by sirtuin-1 (Sirt1). Under severe hypoxia MDM2 protein levels were unchanged, and Sirt1 levels depleted. SiRNA-mediated depletion of MDM2 revealed MDM2 dependent regulation of Suv39H1 protein stability under these conditions. We describe a novel molecular circuit regulating the heterochromatic state (H3K9me3 positive) under severe hypoxic conditions, showing that severe hypoxia-induced ATM activation maintains H3K9me3 levels by downregulating MDM2 and preventing MDM2-mediated degradation of Suv39H1. This novel mechanism is a potential anti-cancer therapeutic opportunity, which if exploited could target the hypoxic tumor cells known to drive both tumor progression and treatment resistance.

Paclitaxel (PTX) is one of the most efficient drugs for late-stage non-small cell lung cancer (NSCLC) patients. However, most patients gradually develop resistance to PTX with long-term treatments. The identification of new strategies to reverse PTX resistance in NSCLC is crucially important for the treatment. PTX is an agonist for the pregnane X receptor (PXR) which regulates PTX metabolism. Antagonizing PXR, therefore, may render the NSCLC more sensitive to the PTX treatment. In this study, we investigated the PXR antagonist SPA70 and its role in PTX treatment of NSCLC. In vitro, SPA70 and PTX synergistically inhibited cell growth, migration and invasion in both paclitaxel-sensitive and paclitaxel-resistant A549 and H460 lung cancer cells. Mechanistically, we found PTX and SPA70 cotreatment disassociated PXR from ABCB1 (MDR1, P-gp) promoter, thus inhibiting P-gp expression. Furthermore, the combination regimen synergistically enhanced the interaction between PXR and Tip60, which abrogated Tip60-mediated α-tubulin acetylation, leading to mitosis defect, S-phase arrest and necroptosis/apoptosis. Combination of PXT and SPA70 dramatically inhibited tumor growth in a paclitaxel-resistant A549/TR xenograft tumor model. Taken together, we showed that SPA70 reduced the paclitaxel resistance of NSCLC. The combination regimen of PTX and SPA70 could be potential novel candidates for the treatment of taxane-resistant lung cancer.

Histone acetylation is a key regulatory feature for chromatin that is established by opposing enzymatic activities of lysine acetyltransferases (KATs/HATs) and deacetylases (KDACs/HDACs). Esa1, like its human homolog Tip60, is an essential MYST family enzyme that acetylates histones H4 and H2A and other nonhistone substrates. Here we report that the essential requirement for ESA1 in Saccharomyces cerevisiae can be bypassed upon loss of Sds3, a noncatalytic subunit of the Rpd3L deacetylase complex. By studying the esa1∆ sds3∆ strain, we conclude that the essential function of Esa1 is in promoting the cellular balance of acetylation. We demonstrate this by fine-tuning acetylation through modulation of HDACs and the histone tails themselves. Functional interactions between Esa1 and HDACs of class I, class II, and the Sirtuin family define specific roles of these opposing activities in cellular viability, fitness, and response to stress. The fact that both increased and decreased expression of the ESA1 homolog TIP60 has cancer associations in humans underscores just how important the balance of its activity is likely to be for human well-being.

Abstract Background Increasing evidence has revealed a close relationship between non-coding RNAs and cancer progression. Circular RNAs (circRNAs), a recently identified new member of non-coding RNAs, are demonstrated to participate in diverse biological processes, such as development, homeostatic maintenance and pathological responses. The functions of circRNAs in cancer have drawn wide attention recently. Until now, the expression patterns and roles of circRNAs in hepatocellular carcinoma (HCC) have remained largely unknown. Methods Bioinformatics method was used to screen differentially expressed novel circRNAs in HCC. Northern blotting, qRT-PCR, in situ hybridization (ISH) and RNA-FISH were utilized to analyzed the expression of circRHOT1 in HCC tisues.CCK8, colony formation, EdU assays were used to analyze proliferation of HCC cells. Transwell assay was utilized to analyze HCC cell migration and invasion. FACS was used for apoptosis analysis. Xenograft experiments were used to analyze tumor growth in vivo. Mass spectrum, RNA pulldown, RIP and EMSA was utilized to test the interaction between circRHOT1 and TIP60. RNA-sequencing method was used to analyze the downstream target gene of circRHOT1. Results We identified circRHOT1 (hsa_circRNA_102034) as a conserved and dramatically upregulated circRNA in HCC tissues. HCC patients displaying high circRHOT1 level possessed poor prognosis. Through in vitro and in vivo experiments, we demonstrated circRHOT1 significantly promoted HCC growth and metastasis. Regarding the mechanism, we conducted a RNA pulldown with a biotin-labeled circRHOT1-specific probe and found that circRHOT1 recruited TIP60 to the NR2F6 promoter and initiated NR2F6 transcription. Moreover, NR2F6 knockout inhibited growth, migration and invasion, whereas rescuing NR2F6 in circRHOT1-knockout HCC cells rescued the proliferation and metastasis abilities of HCC cells. Conclusion Taken together, circRHOT1 inhibits HCC development and progression via recruiting TIP60 to initiate NR2F6 expression, indicating that circRHOT1 and NR2F6 may be potential biomarkers for HCC prognosis.

Abstract The histone variant H2A.Z is involved in several processes such as transcriptional control, DNA repair, regulation of centromeric heterochromatin and, not surprisingly, is implicated in diseases such as cancer. Here, we review the recent developments on H2A.Z focusing on its role in transcriptional activation and repression. H2A.Z, as a replication-independent histone, has been studied in several model organisms and inducible mammalian model systems. Its loading machinery and several modifying enzymes have been recently identified, and some of the long-standing discrepancies in transcriptional activation and/or repression are about to be resolved. The buffering functions of H2A.Z, as supported by genome-wide localization and analyzed in several dynamic systems, are an excellent example of transcriptional control. Posttranslational modifications such as acetylation and ubiquitination of H2A.Z, as well as its specific binding partners, are in our view central players in the control of gene expression. Understanding the key-mechanisms in either turnover or stabilization of H2A.Z-containing nucleosomes as well as defining the H2A.Z interactome will pave the way for therapeutic applications in the future.

The repair of DNA breaks takes place in the context of chromatin and thus involves the activity of chromatin remodelers. The nucleosome acetyltransferase of H4 (NuA4) remodeler complex enables DNA break repair by relaxing flanking chromatin. Here, we show that MRG domain binding protein (MRGBP), a member of this complex, acts as a general inhibitor of DNA double‐strand break repair. Upon its downregulation, repair is generally increased. This is particularly evident for the stimulation of early events of homologous recombination. Thus, MRGBP has an opposing role to the main catalytic subunits of the NuA4 complex. Our data suggest that MRGBP acts by limiting the activity of this complex in DNA repair, specifically by narrowing the extent of DNA‐end resection. [ABSTRACT FROM AUTHOR]

Regulatory T (Treg) cells play a role in the maintenance of immune homeostasis and are critical mediators of immune tolerance. The Forkhead box P3 (FOXP3) protein acts as a regulator for Treg development and function. Mutations in the FOXP3 gene can lead to autoimmune diseases such as Immunodysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) syndrome in humans, often resulting in death within the first 2 years of life and a scurfy like phenotype in Foxp3 mutant mice. We discuss biochemical features of the FOXP3 ensemble including its regulation at various levels (epigenetic, transcriptional, and post-translational modifications) and molecular functions. The studies also highlight the interactions of FOXP3 and Tat-interacting protein 60 (Tip60), a principal histone acetylase enzyme that acetylates FOXP3 and functions as an essential subunit of the FOXP3 repression ensemble complex. Lastly, we have emphasized the role of allosteric modifiers that help stabilize FOXP3:Tip60 interactions and discuss targeting this interaction for the therapeutic manipulation of Treg activity.

Amyloid-β (Aβ) peptides can form protease-resistant aggregates within and outside of neurons. Accumulation of these aggregates is a hallmark of Alzheimer’s disease (AD) neuropathology and contributes to devastating cognitive deficits associated with this disorder. The primary etiological factor for Aβ aggregation is either an increase in Aβ production or a decrease in its clearance. Aβ is produced by the sequential activity of β- and γ-secretase on the amyloid precursor protein (APP) and the clearance is mediated by chaperone-mediated mechanisms. The Aβ aggregates vary from soluble monomers and oligomers to insoluble senile plaques. While excess intraneuronal oligomers can transduce neurotoxic signals into neurons causing cellular defects like oxidative stress and neuroepigenetic mediated transcriptional dysregulation, extracellular senile plaques cause neurodegeneration by impairing neural membrane permeabilization and cell signaling pathways. Paradoxically, senile plaque formation is hypothesized to be an adaptive mechanism to sequester excess toxic soluble oligomers while leaving native functional Aβ levels intact. This hypothesis is strengthened by the absence of positive outcomes and side effects from immunotherapy clinical trials aimed at complete Aβ clearance, and support beneficial physiological roles for native Aβ in cellular function. Aβ has been shown to modulate synaptic transmission, consolidate memory, and protect against excitotoxicity. We discuss the current understanding of beneficial and detrimental roles for Aβ in synaptic function and epigenetic gene control and the future promising prospects of early therapeutic interventions aimed at mediating Aβ induced neuroepigenetic and synaptic dysfunctions to delay AD onset.

Chromatin remodeling plays a key role in the establishment and maintenance of gene expression patterns essential for plant development and responses to environmental factors. Post-translational modification of histones, including acetylation, is one of the most relevant chromatin remodeling mechanisms that operate in eukaryotic cells. Histone acetylation is an evolutionarily conserved chromatin signature commonly associated with transcriptional activation. Histone acetylation levels are tightly regulated through the antagonistic activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs). In plants, different families of HATs are present, including the MYST family, which comprises homologs of the catalytic subunit of the Nucleosome Acetyltransferase of H4 (NuA4) complex in yeast. This complex mediates acetylation of histones H4, H2A, and H2A.Z, and is involved in transcriptional regulation, heterochromatin silencing, cell cycle progression, and DNA repair in yeast. In Arabidopsis and, other plant species, homologs for most of the yeast NuA4 subunits are present and although the existence of this complex has not been demonstrated yet, compelling evidence supports the notion that this type of HAT complex functions from mosses to angiosperms. Recent proteomic studies show that several Arabidopsis homologs of NuA4 components, including the assembly platform proteins and the catalytic subunit, are associated in vivo with additional members of this complex suggesting that a NuA4-like HAT complex is present in plants. Furthermore, the functional characterization of some Arabidopsis NuA4 subunits has uncovered the involvement of these proteins in the regulation of different plant biological processes. Interestingly, for most of the mutant plants deficient in subunits of this complex characterized so far, conspicuous defects in flowering time are observed, suggesting a role for NuA4 in the control of this plant developmental program. Moreover, the participation of Arabidopsis NuA4 homologs in other developmental processes, such as gametophyte development, as well as in cell proliferation and stress and hormone responses, has also been reported. In this review, we summarize the current state of knowledge on plant putative NuA4 subunits and discuss the latest progress concerning the function of this chromatin modifying complex.

Background/Aims: Aberrant expression of Tip60 is associated with progression in many cancers. However, the role of Tip60 in cancer progression remains contradictory. The aim of this study was to investigate the clinical significance, biological functions and underlying mechanisms of Tip60 deregulation in cholangiocarcinoma (CCA) for the first time. Methods: Quantitative real-time PCR (QRT-PCR), western blotting and immunohistochemistry staining (IHC) were carried out to measure Tip60 expression in CCA tissues and cell lines. Kaplan–Meier analysis and the log-rank test were used for survival analysis. In vitro, cell proliferation was evaluated by flow cytometry and CCK-8, colony formation, and EDU assays. Migration/ invasion was evaluated by trans-well assays. Phosphokinase array was used to confirm the dominant signal regulated by Tip60. Tumor growth and metastasis were demonstrated in vivo using a mouse model. Results: Tip60 was notably downregulated in CCA tissues, which was associated with greater tumor size, venous invasion, and TNM stage. Down-regulation of Tip60 was associated with tumor progression and poorer survival in CCA patients. In vitro and in vivo studies demonstrated that Tip60 suppressed growth and metastasis throughout the progression of CCA. We further identified the PI3K/AKT pathway as a dominant signal of Tip60 and suggested that Tip60 regulated CCA cell proliferation and metastasis via PT3K-AKT pathway. Pearson analysis revealed that PTEN was positively correlated with the Tip60 level in CCA tissues. Conclusion: Tip60, as a tumor suppressor in CCA via the PI3K/AKT pathway, might be a promising therapeutic target or prognostic marker for CCA.

Amyloid-β (Aβ) peptides can form protease-resistant aggregates within and outside of neurons. Accumulation of these aggregates is a hallmark of Alzheimer's disease (AD) neuropathology and contributes to devastating cognitive deficits associated with this disorder. The primary etiological factor for Aβ aggregation is either an increase in Aβ production or a decrease in its clearance. Aβ is produced by the sequential activity of β- and γ-secretase on the amyloid precursor protein (APP) and the clearance is mediated by chaperone-mediated mechanisms. The Aβ aggregates vary from soluble monomers and oligomers to insoluble senile plaques. While excess intraneuronal oligomers can transduce neurotoxic signals into neurons causing cellular defects like oxidative stress and neuroepigenetic mediated transcriptional dysregulation, extracellular senile plaques cause neurodegeneration by impairing neural membrane permeabilization and cell signaling pathways. Paradoxically, senile plaque formation is hypothesized to be an adaptive mechanism to sequester excess toxic soluble oligomers while leaving native functional Aβ levels intact. This hypothesis is strengthened by the absence of positive outcomes and side effects from immunotherapy clinical trials aimed at complete Aβ clearance, and support beneficial physiological roles for native Aβ in cellular function. Aβ has been shown to modulate synaptic transmission, consolidate memory, and protect against excitotoxicity. We discuss the current understanding of beneficial and detrimental roles for Aβ in synaptic function and epigenetic gene control and the future promising prospects of early therapeutic interventions aimed at mediating Aβ induced neuroepigenetic and synaptic dysfunctions to delay AD onset. [ABSTRACT FROM AUTHOR]

Background/Aim: In breast cancer, initiation of carcinogenesis leads to epigenetic dysregulation, which can lead for example to the loss of the heterochromatin skeleton SUV39H1/H3K9me3/HP1 or the supposed secondary skeleton TIP60/P400/H4K12ac/BRD (2/4), which allows the maintenance of chromatin integrity and plasticity. This study investigated the relationship between TIP60, P400 and H4K12ac and their implications in breast tumors. Materials and Methods: Seventy-seven patients diagnosed with breast cancer were included in this study. Chromatin immunoprecipitation (ChIP) assay was used to identify chromatin modifications. Western blot and reverse transcription and quantitative real-time PCR were used to determine protein and gene expression, respectively. Results: We verified the variation in H4K12ac enrichment and the colocalization of H4K12ac and TIP60 on the euchromatin and heterochromatin genes, respectively, by ChIP-qPCR and ChIP-reChIP, which showed an enrichment of H4K12ac on specific genes in tumors compared to the adjacent healthy tissue and a co-localization of H4K12ac with TIP60 in different breast tumor types. Furthermore, RNA and protein expression of TIP60 and P400 was investigated and overexpression of TIP60 and P400 mRNA was associated with tumor aggressiveness. Conclusion: There is a potential interaction between H4K12ac and TIP60 in heterochromatin or euchromatin in breast tumors. [ABSTRACT FROM AUTHOR]

Breast cancer is often sporadic due to several factors. Among them, the deregulation of epigenetic proteins may be involved. TIP60 or KAT5 is an acetyltransferase that regulates gene transcription through the chromatin structure. This pleiotropic protein acts in several cellular pathways by acetylating proteins. RNA and protein expressions of TIP60 were shown to decrease in some breast cancer subtypes, particularly in triple-negative breast cancer (TNBC), where a low expression of TIP60 was exhibited compared with luminal subtypes. In this study, the inhibition of the residual activity of TIP60 in breast cancer cell lines was investigated by using two chemical inhibitors, TH1834 and NU9056, first on the acetylation of the specific target, lysine 4 of histone 3 (H3K4) by immunoblotting, and second, by chromatin immunoprecipitation (ChIP)-qPCR (-quantitative Polymerase Chain Reaction). Subsequently, significant decreases or a trend toward decrease of H3K4ac in the different chromatin compartments were observed. In addition, the expression of 48 human nuclear receptors was studied with TaqMan Low-Density Array in these breast cancer cell lines treated with TIP60 inhibitors. The statistical analysis allowed us to comprehensively characterize the androgen receptor and NR3C2 receptors in TNBC cell lines after TH1834 or NU9056 treatment. The understanding of the residual activity of TIP60 in the evolution of breast cancer might be a major asset in the fight against this disease, and could allow TIP60 to be used as a biomarker or therapeutic target for breast cancer progression in the future. [ABSTRACT FROM AUTHOR]

KAT5 encodes an essential lysine acetyltransferase, previously called TIP60, which is involved in regulating gene expression, DNA repair, chromatin remodeling, apoptosis, and cell proliferation; but it remains unclear whether variants in this gene cause a genetic disease. Here, we study three individuals with heterozygous de novo missense variants in KAT5 that affect normally invariant residues, with one at the chromodomain (p.Arg53His) and two at or near the acetyl-CoA binding site (p.Cys369Ser and p.Ser413Ala). All three individuals have cerebral malformations, seizures, global developmental delay or intellectual disability, and severe sleep disturbance. Progressive cerebellar atrophy was also noted. Histone acetylation assays with purified variant KAT5 demonstrated that the variants decrease or abolish the ability of the resulting NuA4/TIP60 multi-subunit complexes to acetylate the histone H4 tail in chromatin. Transcriptomic analysis in affected individual fibroblasts showed deregulation of multiple genes that control development. Moreover, there was also upregulated expression of PER1 (a key gene involved in circadian control) in agreement with sleep anomalies in all of the individuals. In conclusion, dominant missense KAT5 variants cause histone acetylation deficiency with transcriptional dysregulation of multiples genes, thereby leading to a neurodevelopmental syndrome with sleep disturbance, cerebellar atrophy, and facial dysmorphisms, and suggesting a recognizable syndrome. [ABSTRACT FROM AUTHOR]

Objectives: RING finger protein 8 (RNF8) is an E3 ligase that plays an essential role in DSB repair. p53 is a well‐established tumour suppressor and cellular gatekeeper of genome stability. This study aimed at investigating the functional correlations between RNF8 and p53 in DSB damage repair. Materials and methods: In this article, wild‐type, knockout and shRNA‐depleted HCT116 and U2OS cells were stressed, and the roles of RNF8 and p53 were examined. RT‐PCR and Western blot were utilized to investigate the expression of related genes in damaged cells. Cell proliferation, apoptosis and neutral cell comet assays were applied to determine the effects of DSB damage on differently treated cells. DR‐GFP, EJ5‐GFP and LacI‐LacO targeting systems, flow cytometry, mass spectrometry, IP, IF, GST pull‐down assay were used to explore the molecular mechanism of RNF8 and p53 in DSB damage repair. Results: We found that RNF8 knockdown increased cellular sensitivity to DSB damage and decreased cell proliferation, which was correlated with high expression of the p53 gene. RNF8 improved the efficiency of DSB repair by inhibiting the pro‐apoptotic function of p53. We also found that RNF8 restrains cell apoptosis by inhibiting over‐activation of ATM and subsequently reducing p53 acetylation at K120 through regulating Tip60. Conclusions: Taken together, these findings suggested that RNF8 promotes efficient DSB repair by inhibiting the pro‐apoptotic activity of p53 through regulating the function of Tip60. [ABSTRACT FROM AUTHOR]

Chromatin remodeling plays a key role in the establishment and maintenance of gene expression patterns essential for plant development and responses to environmental factors. Post-translational modification of histones, including acetylation, is one of the most relevant chromatin remodeling mechanisms that operate in eukaryotic cells. Histone acetylation is an evolutionarily conserved chromatin signature commonly associated with transcriptional activation. Histone acetylation levels are tightly regulated through the antagonistic activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs). In plants, different families of HATs are present, including the MYST family, which comprises homologs of the catalytic subunit of the Nucleosome Acetyltransferase of H4 (NuA4) complex in yeast. This complex mediates acetylation of histones H4, H2A, and H2A.Z, and is involved in transcriptional regulation, heterochromatin silencing, cell cycle progression, and DNA repair in yeast. In Arabidopsis and, other plant species, homologs for most of the yeast NuA4 subunits are present and although the existence of this complex has not been demonstrated yet, compelling evidence supports the notion that this type of HAT complex functions from mosses to angiosperms. Recent proteomic studies show that several Arabidopsis homologs of NuA4 components, including the assembly platform proteins and the catalytic subunit, are associated in vivo with additional members of this complex suggesting that a NuA4-like HAT complex is present in plants. Furthermore, the functional characterization of some Arabidopsis NuA4 subunits has uncovered the involvement of these proteins in the regulation of different plant biological processes. Interestingly, for most of the mutant plants deficient in subunits of this complex characterized so far, conspicuous defects in flowering time are observed, suggesting a role for NuA4 in the control of this plant developmental program. Moreover, the participation of Arabidopsis NuA4 homologs in other developmental processes, such as gametophyte development, as well as in cell proliferation and stress and hormone responses, has also been reported. In this review, we summarize the current state of knowledge on plant putative NuA4 subunits and discuss the latest progress concerning the function of this chromatin modifying complex. [ABSTRACT FROM AUTHOR]

Abstract Background The nuclear epigenetic integrator UHRF1 is known to play a key role with DNMT1 in maintaining the DNA methylation patterns during cell division. Among UHRF1 partners, TIP60 takes part in epigenetic regulations through its acetyltransferase activity. Both proteins are involved in multiple cellular functions such as chromatin remodeling, DNA damage repair and regulation of stability and activity of other proteins. The aim of this work was to investigate the interaction between UHRF1 and TIP60 in order to elucidate the dialogue between these two proteins. Methods Biochemical (immunoprecipitation and pull-down assays) and microscopic (confocal and fluorescence lifetime imaging microscopy; FLIM) techniques were used to analyze the interaction between TIP60 and UHRF1 in vitro and in vivo. Global methylation levels were assessed by using a specific kit. The results were statistically analyzed using Graphpad prism and Origin. Results Our study shows that UHRF1, TIP60 and DNMT1 were found in the same epigenetic macro-molecular complex. In vitro pull-down assay showed that deletion of either the zinc finger in MYST domain or deletion of whole MYST domain from TIP60 significantly reduced its interaction with UHRF1. Confocal and FLIM microscopy showed that UHRF1 co-localized with TIP60 in the nucleus and confirmed that both proteins interacted together through the MYST domain of TIP60. Moreover, overexpression of TIP60 reduced the DNA methylation levels in HeLa cells along with downregulation of UHRF1 and DNMT1. Conclusion Our data demonstrate for the first time that TIP60 through its MYST domain directly interacts with UHRF1 which might be of high interest for the development of novel oncogenic inhibitors targeting this interaction.

The scaffolding protein family Fe65, composed of Fe65, Fe65L1, and Fe65L2, was identified as an interaction partner of the amyloid precursor protein (APP), which plays a key function in Alzheimer’s disease. All three Fe65 family members possess three highly conserved interaction domains, forming complexes with diverse binding partners that can be assigned to different cellular functions, such as transactivation of genes in the nucleus, modulation of calcium homeostasis and lipid metabolism, and regulation of the actin cytoskeleton. In this article, we rule out putative new intracellular signaling mechanisms of the APP-interacting protein Fe65 in the regulation of actin cytoskeleton dynamics in the context of various neuronal functions, such as cell migration, neurite outgrowth, and synaptic plasticity.

Although histone-modifying enzymes are generally assumed to function in a manner dependent on their enzymatic activities, this assumption remains untested for many factors. Here, we show that the Tip60 (Kat5) lysine acetyltransferase (KAT), which is essential for embryonic stem cell (ESC) self-renewal and pre-implantation development, performs these functions independently of its KAT activity. Unlike ESCs depleted of Tip60, KAT-deficient ESCs exhibited minimal alterations in gene expression, chromatin accessibility at Tip60 binding sites, and self-renewal, thus demonstrating a critical KAT-independent role of Tip60 in ESC maintenance. In contrast, KAT-deficient ESCs exhibited impaired differentiation into mesoderm and endoderm, demonstrating a KAT-dependent function in differentiation. Consistent with this phenotype, KAT-deficient mouse embryos exhibited post-implantation developmental defects. These findings establish separable KAT-dependent and KAT-independent functions of Tip60 in ESCs and during differentiation, revealing a complex repertoire of regulatory functions for this essential chromatin remodeling complex.