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5-azacytidine treatment reorganizes genomic histone modification patterns

ABSTRACT: Methylation of DNA in combination with histone modifications establishes an epigenetic code that ensures the proper control of gene expression. Although DNA methyltransferases have been shown to interact with histone methyltransferases such as EZH2 (which methylates histone H3 on lysine 27) and G9a (which methylates histone H3 on lysine 9), the relationship between DNA methylation and repressive histone marks has not been fully studied. In cancer cells, promoters of genes are often aberrantly methylated. Accordingly, 5-azacytidine (a DNA demethylating drug) is used for treating patients with myelodysplastic syndrome. However, no genome-scale studies of the effects of this drug have been reported. In this work, we report the effects of 5-azacytidine on global gene expression and analyze ~24,000 human promoters using ChIP-chip to determine how 5-azacytidine treatment effects H3K27me3 and H3K9me3 levels. We found that (1) 5-azacytidine treatment results in large changes in gene regulation with distinct functional categories of genes showing increased (e.g. C2H2 zinc finger transcription factors) and decreased (e.g. genes involved in regulation of mitochondria and oxidoreductase activity) levels; (2) most genes that show altered expression are not regulated by promoters that display DNA methylation prior to the treatment; (3) certain gene classes switch their repression mark upon treatment with 5-azacytidine (from H3K27me3 to H3K9me3 and vice versa); and (4) most changes in gene expression are not due to relief of repression mediated by DNA or histone methylation.

ORGANISM(S): Homo sapiens

PROVIDER: GSE20598 | GEO | 2010/04/09

SECONDARY ACCESSION(S): PRJNA124885

REPOSITORIES: GEO

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5-azacytidine treatment reorganizes genomic histone modification patterns

Project description:Methylation of DNA in combination with histone modifications establishes an epigenetic code that ensures the proper control of gene expression. Although DNA methyltransferases have been shown to interact with histone methyltransferases such as EZH2 (which methylates histone H3 on lysine 27) and G9a (which methylates histone H3 on lysine 9), the relationship between DNA methylation and repressive histone marks has not been fully studied. In cancer cells, promoters of genes are often aberrantly methylated. Accordingly, 5-azacytidine (a DNA demethylating drug) is used for treating patients with myelodysplastic syndrome. However, no genome-scale studies of the effects of this drug have been reported. In this work, we report the effects of 5-azacytidine on global gene expression and analyze ~24,000 human promoters using ChIP-chip to determine how 5-azacytidine treatment effects H3K27me3 and H3K9me3 levels. We found that (1) 5-azacytidine treatment results in large changes in gene regulation with distinct functional categories of genes showing increased (e.g. C2H2 zinc finger transcription factors) and decreased (e.g. genes involved in regulation of mitochondria and oxidoreductase activity) levels; (2) most genes that show altered expression are not regulated by promoters that display DNA methylation prior to the treatment; (3) certain gene classes switch their repression mark upon treatment with 5-azacytidine (from H3K27me3 to H3K9me3 and vice versa); and (4) most changes in gene expression are not due to relief of repression mediated by DNA or histone methylation. 5 ChIP-chip arrays. 6 gene expression samples: 3 treatments with 2 biological replicates per treatment.

2010-04-09 | E-GEOD-20598 | biostudies-arrayexpress

DAXX adds a de novo H3.3K9me3 deposition pathway to the histone chaperone network (part 1)

Project description:A multitude of histone chaperones are required to support histones from their biosynthesis until DNA deposition. They cooperate through the formation of histone co-chaperone complexes, but the crosstalk between nucleosome assembly pathways remains enigmatic. Using exploratory interactomics, we define the interplay between histone H3–H4 chaperones in the histone chaperone network. We identify several novel histone dependent complexes and predict the structure of the ASF1 and SPT2 co-chaperone complex, expanding the role of ASF1 in histone dynamics. We show that DAXX provides a unique functionality to the histone chaperone network, recruiting histone methyltransferases to promote H3K9me3 catalysis on new histone H3.3–H4 prior to deposition onto DNA. Hereby, DAXX provides a molecular mechanism for de novo H3K9me3 deposition and heterochromatin assembly. Collectively, our findings provide a framework for understanding how cells orchestrate histone supply and employ targeted deposition of modified histones to underpin specialized chromatin states.

2023-03-02 | PXD034888 | Pride

DAXX adds a de novo H3.3K9me3 deposition pathway to the histone chaperone network (part 2)

2023-03-02 | PXD038263 | Pride

LSD1 Prevents Aberrant Heterochromatin Formation in Neurospora crassa

Project description:Heterochromatin is a specialized form of chromatin that restricts access to DNA and inhibits genetic processes, including transcription and recombination. In Neurospora crassa, constitutive heterochromatin is characterized by trimethylation of lysine 9 on histone H3, hypoacetylation of histones, and DNA methylation. Here we explore whether the conserved histone demethylase, lysine-specific demethylase 1 (LSD1), regulates heterochromatin in Neurospora, and if so, how. Though LSD1 is implicated in heterochromatin regulation, its function is inconsistent across different systems; orthologs of LSD1 have been shown to either promote or antagonize heterochromatin expansion by removing H3K4me or H3K9me respectively. We identify three members of the Neurospora LSD complex (LSDC): LSD1, PHF1, and BDP-1, and strains deficient for any exhibit variable spreading of heterochromatin and establishment of new heterochromatin domains dispersed across the genome. Heterochromatin establishment outside of canonical domains in Neurospora share the unusual characteristic of DNA methylation-dependent H3K9me3; typically, H3K9me3 establishment is independent of DNA methylation. Consistent with this, the hyper-H3K9me3 phenotype of LSD1 knock-out strains is dependent on the presence of DNA methylation, as well as HCHC-mediated histone deacetylation, suggesting spreading is dependent on some feedback mechanism. Altogether, our results suggest LSD1 works in opposition to HCHC to maintain proper heterochromatin boundaries.

2021-07-21 | PXD017300 | Pride

Proteomic analyses identify a novel role for EZH2 in the initiation of cancer cell drug tolerance

Project description:Acquisition of drug resistance remains a chief impediment to successful cancer therapy, and we previously described a transient drug-tolerant cancer cell population (DTPs) whose survival is in part dependent on the activities of the histone methyltransferases G9a/EHMT2 and EZH2, the latter being the catalytic component of the polycomb repressive complex 2 (PRC2). Here, we applied multiple proteomic techniques to better understand the role of these HMTs in the establishment of the DTP state. Proteome-wide comparisons of lysine methylation patterns revealed that DTPs have increased methylation on K116 of PRC member Jarid2, an event that helps stabilize and recruit PRC2 to chromatin. We also found that EZH2, in addition to methylating histone H3K27, also methylates G9a at K185, and that methylated G9a better recruits repressive complexes to chromatin; similar to complexes recruited by histone H3 methylated at K9. Finally, a detailed histone posttranslational modification (PTM) analysis shows that EZH2, either directly or through its ability to methylate G9a, alters H3K9 methylation in the specific context of H3 serine10 phosphorylation, and primarily in a cancer cell subpopulation that serves as DTP precursors. We also show that combinations of histone PTMs recruit a different set of complexes to chromatin, shedding light on the temporal mechanisms that contribute to drug tolerance.

2020-01-24 | MSV000084838 | MassIVE

Gene regulation in Erbb2 transfected NIH3T3 cells after Azacytidine treatment

Project description:5-Azacytidine or 5-aza-2’-deoxycytidine is a chemical analogue of the cytosine nucleoside used in DNA and RNA. Cells in the presence of 5-azacytidine incorporate it into DNA during replication and RNA during transcription. The incorporation of 5-azacytidine into DNA or RNA inhibits methyltransferase thereby causing demethylation in that sequence, affecting the way that cell regulation proteins are able to bind to the DNA/RNA substrate. Inhibition of DNA occurs through the formation of stable complexes between the molecule and with DNA methyltransferases, thereby saturating the cells methylation machinery. 5-azacytidine is mainly used in the treatment of myelodysplastic syndrome. Changes in gene expression levels in Erbb2 transfected murine fibroblast cell line after treatment with Azacytidine in two different concentrations were analysed. Keywords: cDNA microarray, murine fibroblast, azacytidine treatment, carcinogenesis

2009-10-01 | GSE8374 | GEO

Examining the effect of the linker DNA length on protein binding to di-nucleosomes decorated with H3K9me3 and H3K27me3

Project description:Characteristic features of chromatin states are not limited to particular epigenetic modifications but include other regulatory cues, such as linker DNA length, typically ranging from between 35-55 bp (Valouev et al, 2011; Voong et al., 2016, Cell) to over 200 bp in nucleosome-depleted regions (NDRs) found at active enhancers and promoters (Schones et al, 2008; Hansen He et al, 2010). To investigate whether and how the nucleosome linker DNA affects chromatin recognition by nuclear proteins we performed a set of affinity purifications using di-nucleosomes incorporating different DNA linkers. This dataset contains experiments aimed to probe how the linker DNA length affects protein binding to di-nucleosomes decorated with H3K9me3 or H3K27me3. The following di-nucleosomes were used in affinity pull-down purifications with HeLa nuclear extract followed by label-free MS: 1. unmod. H3, 35 bp linker 2. unmod. H3, 40 bp linker 3. unmod. H3, 45 bp linker 4. unmod. H3, 50 bp linker 5. unmod. H3, 55 bp linker 6. H3K9me3, 35 bp linker 7. H3K9me3, 40 bp linker 8. H3K9me3, 45 bp linker 9. H3K9me3 50 bp linker 10. H3K9me3, 55 bp linker 11. H3K27me3, 35 bp linker 12. H3K27me3, 40 bp linker 13. H3K27me3, 45 bp linker 14. H3K27me3, 50 bp linker 15. H3K27me3, 55 bp linker

2023-12-10 | PXD042368 | Pride

Gene regulation in Erbb2 transfected NIH3T3 cells after Azacytidine treatment

Project description:5-Azacytidine or 5-aza-2â??-deoxycytidine is a chemical analogue of the cytosine nucleoside used in DNA and RNA. Cells in the presence of 5-azacytidine incorporate it into DNA during replication and RNA during transcription. The incorporation of 5-azacytidine into DNA or RNA inhibits methyltransferase thereby causing demethylation in that sequence, affecting the way that cell regulation proteins are able to bind to the DNA/RNA substrate. Inhibition of DNA occurs through the formation of stable complexes between the molecule and with DNA methyltransferases, thereby saturating the cells methylation machinery. 5-azacytidine is mainly used in the treatment of myelodysplastic syndrome. Changes in gene expression levels in Erbb2 transfected murine fibroblast cell line after treatment with Azacytidine in two different concentrations were analysed. Keywords: cDNA microarray, murine fibroblast, azacytidine treatment, carcinogenesis Gene expression levels of Erbb2 transfected NIH3T3 cell lines treated with 5ÂµM and 10ÂµM Azacytidine were compared to Erbb2 transfected but non-treated NIH3T3 cell line. For each Azacytidine concentration 4-8 experiments were performed including 50% dye swaps. As a controll experiments gene expression levels of NIH3T3 cells with and without Azacytidine treatment were analysed

2009-10-01 | E-GEOD-8374 | biostudies-arrayexpress

Regulation of Promoter and Enhancer Histone Landscape by DNA Methylation in Embryonic Stem Cells (RNA-seq)

Project description:In this study, we mapped modification of lysine 4 and lysine 27 of histone H3 genome-wide in a series of mouse embryonic stem cells (mESCs) varying in DNA methylation levels based on knock-out and reconstitution of DNA methyltransferases (DNMTs). We extend previous studies showing cross-talk between DNA methylation and histone modifications by examining a breadth of histone modifications, causal relationships, and direct effects. Our data shows a causal regulation of H3K27me3 at gene promoters as well as H3K27ac and H3K27me3 at tissue-specific enhancers. We also identify isoform differences between DNMT family members. This study provides a comprehensive resource for the study of the complex interplay between DNA methylation and histone modification landscape. RNA-seq performed on wild-type, Dnmt triple knock-out (Dnmt1/3a/3b; TKO), Dnmt double knock-out (Dnmt3a/3b; DKO), and respective reconstitution mouse embryonic stem cell lines

2016-08-02 | E-GEOD-77003 | biostudies-arrayexpress

Regulation of Promoter and Enhancer Histone Landscape by DNA Methylation in Embryonic Stem Cells (RRBS)

Project description:In this study, we mapped modification of lysine 4 and lysine 27 of histone H3 genome-wide in a series of mouse embryonic stem cells (mESCs) varying in DNA methylation levels based on knock-out and reconstitution of DNA methyltransferases (DNMTs). We extend previous studies showing cross-talk between DNA methylation and histone modifications by examining a breadth of histone modifications, causal relationships, and direct effects. Our data shows a causal regulation of H3K27me3 at gene promoters as well as H3K27ac and H3K27me3 at tissue-specific enhancers. We also identify isoform differences between DNMT family members. This study provides a comprehensive resource for the study of the complex interplay between DNA methylation and histone modification landscape. Reduced representation bisulfite sequencing (RRBS) performed on wild-type, Dnmt triple knock-out (Dnmt1/3a/3b; TKO), Dnmt double knock-out (Dnmt3a/3b; DKO), and respective reconstitution mouse embryonic stem cell lines.

2016-08-02 | E-GEOD-84103 | biostudies-arrayexpress

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