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Long noncoding RNA H19 promotes the acquisition of a mesenchymal-like invasive phenotype in mesothelial primary cells through an HDAC1-mediated WT1/Sp1 switch.

Peritoneal fibrosis is a pathological alteration of the peritoneal membrane occurring in pro-inflammatory conditions, including peritoneal dialysis (PD), a renal replacement therapy. Characteristic of this process is the acquisition of invasive/pro-fibrotic abilities by mesothelial cells (MCs) through induction of mesothelial to mesenchymal transition (MMT), a cell-specific form of EMT. Long noncoding (lnc) RNAs act as major players in physiologic regulatory circuitries of the cell. While LncRNA-H19 (lncH19), one of the first lncRNAs identified, has been broadly studied in tumorigenesis, its role in peritoneum fibrotic diseases has been scarcely addressed so far. Aim of this study was to investigate the role of H19 in the acquisition of a mesenchymal-like phenotype in primary fibrotic MCs from PD patients, and to elucidate epigenetic mechanisms controlling its expression. Genetic silencing/ectopic expression experiments revealed that H19 promoted the expression of MMT markers while downregulating the epithelial marker E-Cadherin, and favored MC directed migration and invasion on a collagen matrix. Silencing of three main H19 isoforms revealed a synergistic activity in the induction of a mesenchymal phenotype. Treatment with MS-275, an HDAC1-3 specific inhibitor previously known to promote MMT reversal, as well as HDAC1 genetic silencing, downregulated lncRNA H19 expression. Bioinformatic analysis revealed a binding sequence of Wilm's Tumor Protein 1 (WT1), the master gene of mesothelial differentiation, on the H19 promoter at an area with multiple acetylation peaks partially overlapping the binding site of Specificity protein 1 (Sp1), another transcription factor active in cellular plasticity regulation. Genetic silencing and Chromatin Immunoprecipitation (ChIP) experiments demonstrated that HDAC1 inhibition promotes a switch between WT1 and Sp1 in H19 promoter occupancy, favoring an inhibitory effect of WT1 on H19 expression and the reversal towards an epithelial-like phenotype. Overall, we discovered an HDAC1-WT1/Sp1-H19 axis potentially relevant to the design of new therapies aimed at counteracting peritoneal fibrosis.

RNA, Long Noncoding

Gfi1 coordinates epigenetic repression of p21Cip/WAF1 by recruitment of histone lysine methyltransferase G9a and histone deacetylase 1.

The growth factor independent 1 (Gfi1) transcriptional regulator oncoprotein plays a crucial role in hematopoietic, inner ear, and pulmonary neuroendocrine cell development and governs cell processes as diverse as self-renewal of hematopoietic stem cells, proliferation, apoptosis, differentiation, cell fate specification, and oncogenesis. However, the molecular basis of its transcriptional functions has remained elusive. Here we show that Gfi1 recruits the histone lysine methyltransferase G9a and the histone deacetylase 1 (HDAC1) in order to modify the chromatin of genes targeted for repression by Gfi1. G9a and HDAC1 are both in a repressive complex assembled by Gfi1. Endogenous Gfi1 colocalizes with G9a, HDAC1, and K9-dimethylated histone H3. Gfi1 associates with G9a and HDAC1 on the promoter of the cell cycle regulator p21Cip/WAF1, resulting in an increase in K9 dimethylation at histone H3. Silencing of Gfi1 expression in myeloid cells reverses G9a and HDAC1 recruitment to p21Cip/WAF1 and elevates its expression. These findings highlight the role of epigenetics in the regulation of development and oncogenesis by Gfi1.

Cell Line, Tumor

Unraveling the c-Myc-CASC19/HDAC1-NPM1 epigenetic axis: A novel regulatory circuitry and therapeutic target in gastric carcinogenesis.

Mounting evidence implicates long non-coding RNA cancer susceptibility candidate 19 (CASC19) in the pathogenesis of diverse malignancies. However, its functional role and molecular mechanisms in gastric cancer (GC) remain elusive. Herein, we identified a novel 717-bp transcript isoform of CASC19 in GC cells. This study aimed to delineate the biological functions and underlying mechanisms of this novel CASC19 transcript in GC pathogenesis. CASC19 was significantly upregulated in GC tissues and cell lines, correlating with adverse clinicopathological features and poor prognosis in GC patients. Functional investigations demonstrated that CASC19 overexpression potentiated GC cell proliferation, metastasis, and epithelial-mesenchymal transition, whereas CASC19 knockdown attenuated these malignant phenotypes and suppressed tumorigenesis in xenograft models. Mechanistically, CASC19 functioned as a molecular scaffold by recruiting histone deacetylase 1 (HDAC1) to the nucleophosmin 1 (NPM1) promoter. This recruitment sustained H3K27 deacetylation, thereby transcriptionally repressing NPM1 promoter activity and accelerating gastric carcinogenesis. Crucially, Depletion of HDAC1 or NPM1 partial rescued CASC19-mediated oncogenic effects. Intriguingly, the transcription factor c-Myc was found to transcriptionally activate CASC19 through direct binding to its promoter region. Collectively, our findings indicate that the c-Myc-CASC19/HDAC1-NPM1 axis acts as a potential prognostic biomarker candidate for GC and may represent a therapeutic vulnerability worthy of future investigation.

Humans

Analysis of differentially expressed genes in schizophrenia based on bioinformatics and corresponding mRNA expression levels.

OBJECTIVE: This study aimed to use bioinformatics analysis to identify differentially expressed genes (DEGs) involved in the pathogenesis of schizophrenia and validate their mRNA expression levels through real-time quantitative PCR (qPCR). MATERIAL/METHODS: Datasets from the publicly available Gene Expression Omnibus (GEO) database were analyzed using R software to identify DEGs. Functional enrichment analyses, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, were conducted. A protein-protein interaction (PPI) network was constructed using Cytoscape software to identify key genes with notable expression changes. The expression levels of these key genes were subsequently validated in schizophrenia patients using qPCR to assess potential susceptibility genes. RESULTS: In total, 813 DEGs were identified, with six key genes highlighted through GO analysis and PPI network screening. Among these, HDAC1, UBA52, and FYN demonstrated statistically significant differences in mRNA expression between schizophrenia patients and healthy controls (P&#xa0;<&#xa0;0.05). CONCLUSIONS: This study identified several DEGs potentially linked to the pathogenesis of schizophrenia, suggesting that HDAC1, UBA52, and FYN could serve as candidate susceptibility genes and diagnostic biomarkers. These findings provide new insights and directions for future schizophrenia research.

Humans

Unidirectional recruitment between MeCP2 and KSHV-encoded LANA revealed by CRISPR/Cas9 recruitment assay.

Kaposi's sarcoma-associated herpesvirus (KSHV, HHV-8) is associated with several human malignancies. During latency, the viral genomes reside in the nucleus of infected cells as large non-integrated plasmids, known as episomes. To ensure episome maintenance, the latency protein LANA tethers the viral episomes to the cell chromosomes during cell division. Directional recruitment of protein complexes is critical for the proper function of many nuclear processes. To test for recruitment directionality between LANA and cellular proteins, we directed LANA via catalytically inactive Cas9 (dCas9) to a repeat sequence to obtain easily detectable dots. Then, the recruitment of nuclear proteins to these dots can be evaluated. We termed this assay CRISPR-PITA for Protein Interaction and Telomere Recruitment Assay. Using this protein recruitment assay, we found that LANA recruits its known interactors ORC2 and SIN3A. Interestingly, LANA was unable to recruit MeCP2, but MeCP2 recruited LANA. Both LANA and histone deacetylase 1 (HDAC1) interact with the transcriptional-repression domain (TRD) and the methyl-CpG-binding domain (MBD) of MeCP2. Similar to LANA, HDAC1 was unable to recruit MeCP2. While heterochromatin protein 1 (HP1), which interacts with the N-terminal of MeCP2, can recruit MeCP2. We propose that available interacting domains force this recruitment directionality. We hypothesized that the tandem repeats in the SunTag may force MeCP2 dimerization and mimic the form of DNA-bound MeCP2. Indeed, providing only the tandem epitopes of SunTag allows LANA to recruit MeCP2 in infected cells. Therefore, CRISPR-PITA revealed the rules of unidirectional recruitment and allowed us to break this directionality.

Humans

Crotonylome profiling identifies MLKL crotonylation in lupus nephritis associated with RAB1A-mTOR signalling and autophagy changes in tubular epithelial cells.

OBJECTIVE: To investigate whether MLKL crotonylation is associated with tubular autophagy-lysosome pathway homeostasis in lupus nephritis (LN) and to explore its relationship with RAB1A-mechanistic target of rapamycin (mTOR) signalling. METHODS: Crotonylome proteomics was performed in peripheral blood mononuclear cells from patients with LN, patients with systemic lupus erythematosus without nephritis and healthy controls. Renal biopsy tissues were evaluated for tubulointerstitial fibrosis and autophagy-lysosome pathway-related markers. Mechanistic studies were conducted in lipopolysaccharide-stimulated HK-2 cells. Autophagic flux was assessed using bafilomycin A1. The dependency of mTOR/autophagy changes on RAB1A was tested by siRNA-mediated knockdown. RESULTS: MLKL was identified as a differentially crotonylated protein in LN, with increased crotonylation at K95 and K219. Kidney tissues from patients with LN showed increased fibronectin and collagen III deposition compared with controls, whereas no significant difference was observed between class IV and class V LN. LC3 signal did not differ significantly between groups, whereas LAMP1 expression and LC3-LAMP1 co-localisation were reduced in LN. In HK-2 cells, crotonylation-deficient MLKL mutants were associated with increased LC3-II and reduced p62, whereas K219Q showed the opposite pattern. Autophagic flux assays using bafilomycin A1 showed that K219R-expressing cells had higher LC3-II levels than WT cells both before and after lysosomal inhibition, with comparable BafA1-induced LC3-II accumulation, consistent with increased autophagosome formation rather than impaired lysosomal degradation. HDAC1 knockdown increased MLKL crotonylation and was accompanied by mTOR activation. MLKL crotonylation enhanced RAB1A guanriphosphat osphate (GTP) binding without altering total RAB1A abundance. RAB1A knockdown in MLKL WT-expressing cells attenuated mTOR phosphorylation and partly reversed the autophagy-suppressive marker profile. Sodium crotonate induced an autophagy-suppressive marker profile that was partly reversed by rapamycin. CONCLUSION: MLKL crotonylation is associated with activation of the RAB1A-mTOR axis and altered tubular autophagy-lysosome pathway homeostasis in LN. These findings suggest that tubular injury-related changes in LN may not be fully reflected by glomerulus-based classification alone.

Humans

Proteins driving liquid-liquid phase separation and histone modifications cooperatively associate with chromatin looping and transcriptional regulation.

BACKGROUND: Although liquid-liquid phase separation (LLPS) proteins are known to participate in genome organization and transcriptional regulation through the formation of biomolecular condensates, their functional interplay with other regulatory proteins and histone modifications in chromatin loop formation remains poorly characterized. By combining Hi-C chromatin interaction data with ChIP-seq profiles of 12, 27, and 24 LLPS proteins in GM12878, K562, and HepG2 cell lines, respectively, we identified chromatin loops associated with LLPS proteins and systematically analysed patterns of cooperative protein binding and histone modification enrichment within these loop-associated peaks. RESULTS: We identified 162, 313, and 431 chromatin loops associated with LLPS proteins in GM12878, K562, and HepG2 cell lines, respectively. These loops were relatively small in size and predominantly anchored at enhancer regions. Examination of cooperative binding of proteins within loop-associated peaks revealed that transcriptional repressor IKZF1, HDAC1, and SAP130 most frequently co-localized with LLPS proteins in GM12878, K562, and HepG2 cells, respectively. Further analysis of histone modification enrichment patterns revealed that active histone modifications, such as H3K4me2, H3K4me3, H3K9ac, and H3K27ac, co-localized at loop-associated peaks, with H3K4me1 exhibiting additional specific co-localization with these four histone modifications at enhancer-localized loop-associated peaks. Notably, bivalent chromatin domains where H3K27me3 co-localized with active histone modifications were identified at promoter-localized loop-associated peaks in HepG2 cells, and elevated H3K27me3 occupancy at these peaks was associated with transcriptional repression of target genes. Moreover, quantitative RNA-seq analysis revealed that the expression of target genes associated with enhancer-promoter loops was correlated with both the binding of LLPS proteins and the enrichment patterns of histone modifications within their ChIP-seq peaks at loop anchors. CONCLUSIONS: Our study suggests that LLPS proteins may cooperate with transcriptional repressors to facilitate chromatin looping. Furthermore, local enrichment of histone modifications at loop-associated peaks provides additional regulatory control over chromatin architecture and gene transcription.

Humans

Reversion from basal histone H4 hypoacetylation at the replication fork increases DNA damage in FANCA deficient cells.

The FA/BRCA pathway safeguards DNA replication by repairing interstrand crosslinks (ICL) and maintaining replication fork stability. Chromatin structure, which is in part regulated by histones posttranslational modifications (PTMs), has a role in maintaining genomic integrity through stabilization of the DNA replication fork and promotion of DNA repair. An appropriate balance of PTMs, especially acetylation of histones H4 in nascent chromatin, is required to preserve a stable DNA replication fork. To evaluate the acetylation status of histone H4 at the replication fork of FANCA deficient cells, we compared histone acetylation status at the DNA replication fork of isogenic FANCA deficient and FANCA proficient cell lines by using accelerated native immunoprecipitation of nascent DNA (aniPOND) and in situ protein interactions in the replication fork (SIRF) assays. We found basal hypoacetylation of multiple residues of histone H4 in FA replication forks, together with increased levels of Histone Deacetylase 1 (HDAC1). Interestingly, high-dose short-term treatment with mitomycin C (MMC) had no effect over H4 acetylation abundance at the replication fork. However, chemical inhibition of histone deacetylases (HDAC) with Suberoylanilide hydroxamic acid (SAHA) induced acetylation of the FANCA deficient DNA replication forks to levels comparable to their isogenic control counterparts. This forced permanence of acetylation impacted FA cells homeostasis by inducing DNA damage and promoting G2 cell cycle arrest. Altogether, this caused reduced RAD51 foci formation and increased markers of replication stress, including phospho-RPA-S33. Hypoacetylation of the FANCA deficient replication fork, is part of the cellular phenotype, the perturbation of this feature by agents that prevent deacetylation, such as SAHA, have a deleterious effect over the delicate equilibrium they have reached to perdure despite a defective FA/BRCA pathway.

Histones