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Sequential ChIP-bisulfite sequencing enables direct genome-scale investigation of chromatin and DNA methylation cross-talk

ABSTRACT: Cross-talk between DNA methylation and histone modifications drives the establishment of composite epigenetic signatures and is traditionally studied using correlative rather than direct approaches. Here we present sequential ChIP-bisulfite-sequencing (ChIP- BS-seq) as an approach to quantitatively assess DNA methylation patterns associated with chromatin modifications or chromatin-associated factors directly. A chromatin- immunoprecipitation (ChIP)-capturing step is used to obtain a restricted representation of the genome occupied by the epigenetic feature of interest, for which a single-base resolution DNA methylation map is then generated. When applied to H3 lysine 27 tri- methylation (H3K27me3), we found that H3K27me3 and DNA methylation are compatible throughout most of the genome, except for CpG islands, where these two marks are mutually exclusive. Further ChIP-BS-seq-based analysis in Dnmt triple- knock-out (TKO) embryonic stem cells revealed that total loss of CpG methylation is associated with alteration of H3K27me3 levels throughout the genome: H3K27me3 in localized peaks is decreased while broad local enrichments (BLOCs) of H3K27me3 are formed. At an even broader scale, these BLOCs correspond to regions of high DNA methylation in wild-type ES cells, suggesting that DNA methylation prevents H3K27me3 deposition locally and at megabase scale. Our strategy provides an unique way of investigating global interdependencies between DNA methylation and other chromatin features.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE28254 | GEO | 2012/03/27

SECONDARY ACCESSION(S): PRJNA139563

REPOSITORIES: GEO

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Project description:Cross-talk between DNA methylation and histone modifications drives the establishment of composite epigenetic signatures and is traditionally studied using correlative rather than direct approaches. Here we present sequential ChIP-bisulfite-sequencing (ChIP- BS-seq) as an approach to quantitatively assess DNA methylation patterns associated with chromatin modifications or chromatin-associated factors directly. A chromatin- immunoprecipitation (ChIP)-capturing step is used to obtain a restricted representation of the genome occupied by the epigenetic feature of interest, for which a single-base resolution DNA methylation map is then generated. When applied to H3 lysine 27 tri- methylation (H3K27me3), we found that H3K27me3 and DNA methylation are compatible throughout most of the genome, except for CpG islands, where these two marks are mutually exclusive. Further ChIP-BS-seq-based analysis in Dnmt triple- knock-out (TKO) embryonic stem cells revealed that total loss of CpG methylation is associated with alteration of H3K27me3 levels throughout the genome: H3K27me3 in localized peaks is decreased while broad local enrichments (BLOCs) of H3K27me3 are formed. At an even broader scale, these BLOCs correspond to regions of high DNA methylation in wild-type ES cells, suggesting that DNA methylation prevents H3K27me3 deposition locally and at megabase scale. Our strategy provides an unique way of investigating global interdependencies between DNA methylation and other chromatin features. ChIP (chromatin immunoprecipitation) is followed by bisulfite conversion and deep sequencing to directly assess DNA methylation levels in captured chromatin fragments (ChIP-BS-seq). We used ChIP-BS-seq to study the potential global cross-talk between H3K27me3 and DNA methylation, which are both linked to repression. First, we used capturing of methylated DNA, followed by bisulfite-deep sequencing (MethylCap-BS-seq). Genomic DNA isolated from normal and tumor colon tissues was used for MethylCap-BS-seq as well as for conventional MethylCap-seq experiments. Second, we performed ChIP-BS-seq on H3K27me3, using HCT116 colon carcinoma cells. Third, to further study the relevance of the observations, we generated genome-wide profiles for H3K27me3 and DNA methylation by conventional ChIP-seq and MethylCap-seq, and RNA-seq, respectively. Finally, we performed H3K27me3-ChIP-BS-seq and MethylCap-seq on wild-type mouse ES cells as well as Dnmt-triple-knockout (TKO) mouse ES cells.

Project description:The model describing that aberrant CpG island (CGI) methylation leads to transcription repression of tumor suppressor genes and thereby is implicated in tumor progression has been established in many cancers. However, recent studies indicated aberrantly hypermethylated genes in multiple cancers are already repressed in pre-cancerous tissues despite their promoters are hypomethylated. Here, we hypothesized that the occurrence of CGI promoter hypermethylation in cancers are associated with Polycomb-repressive complex and the associated H3K27me3 mark in pre-cancerous tissues. By using a ChIP-BS-seq technology that examines methylation of the DNA fragments precipitated by the antibodies to histone modifications, we provided direct evidences showing that genes highly enriched with H3K27me3 marks both in cancer and normal cells became aberrantly hypermethylated in CGI promoters in cancer cells in comparison with normal cells. Furthermore, we confirmed that these genes consistently were significantly hypermethylated in TCGA primary cancer in comparison with normal tissues. Thus, we provided direct evidences supporting that the presence of H3K27m3 may serve as a guide to promoter hypermethylation. This will spur future work on epigenetic signature of combined histone and DNA methylation that could define a cancerM-bM-^@M-^Ys epigenetic abnormalities, therefore helping distinguish subtypes of cancers and aiding future diagnosis and therapeutics of cancers. We applied ChIP-BS technology to examine H3K27me3 marks, which are catalyzed by the SET domain histone methyltransferase EZH2 and have a repressive function with 50bp pair-end sequencing. found H3K27me3 marks were enriched preferentially at CpG islands, (+/-500) transcription start sites (TSSs) and exons in two GC cell lines (BGC-823 and AGS). In YH cells, H3K27me3 marks were only preferentially enriched at CpG islands. In contrast, Hela cells presented a reverse pattern with highest H3K27me3 enrichment in intergenic regions. To confirm this result in Hela cells, we performed two independent replicates of ChIP-Seq and ChIP-BS-seq. Cause of useful was relative small. we still sequenced one 100bp pe reads replicate for H3K4me3 and two replicate for H3K27me3 ChIP-BS-seq.

Project description:Epigenetic environment of histone H3.3 on promoters revealed by integration of imaging and genome-scale chromatin and methyl-DNA immunoprecipitation information. Chromatin regions with different transcriptional outputs are distinguished by the deposition of histone variants. Histone H3.3 is incorporated into chromatin in a replication-independent manner; yet the relationship between H3.3 deposition, chromatin environment is incompletely understood. We have integrated imaging and genome-scale chromatin and methyl-DNA immunoprecipitation approaches to investigate the genomic distribution of epitope-tagged H3.3 in relation to histone modifications, DNA methylation and transcription. Results: Imaging shows that H3.3, in contrast to replicative H3.1 or H2B, is enriched in chromatin marked by histone modifications of active genes. A genome-wide survey identifies 1,649 H3.3-enriched promoters, only a subset of which is co-enriched in H3K4me3, H3K9me3 and/or H3K27me3, with a preference for H3K4me3, corroborating imaging data. H3.3-enriched promoters are depleted of H3.3 at the TSS in a transcription-independent manner. H3.3 is found predominantly on CpG-rich unmethylated promoters, creating a condition favourable for transcription. In undifferentiated mesenchymal stem cells, H3.3 target genes are linked to signaling and mesodermal differentiation, suggesting that H3.3 may be a mark of lineage priming. Conclusions: A minor fraction of H3.3 is targeted to promoters, which are predominantly CpG-rich, DNA unmethylated and devoid of detectable trimethylated H3K4, K9 and K27. Among H3.3 target promoters co-marked by methylated H3, H4K4me3 is preferred, with or without H3K27me3, arguing that in mesenchymal stem cells H3.3 marks transcriptionally active or potentially active promoters. Key words: Imaging, ChIP-chip, MeDIP-chip, histone H3.3, mesenchymal stem cells ChIP-chip and MeDIP-chip experiments: Performed with two independent biological replicates. Gene expression profiling experiments: Total RNA obtained from H3.3-EGFP transfected or empty-EGFP transfected mesenchymal stem cells compared to untransfected mesenchymal stem cells. Raw expression data linked below as supplementary file (GSE17053_Illumina_non-normalized_data.txt).

Project description:Aberrant DNA hypermethylation of CpG island (CGI) promoters are associated with transcriptional repression of many tumor suppressor genes and lead to tumor progression in many cancers. Most recently, one research group observed that aberrantly hypermethylated genes in multiple cancers are already repressed, but their promoters are maintained in a hypomethylated state in pre-cancerous tissues.Their studies didn't provide a clue to explain by what mechanisms those genes were repressed in pre-cancerous tissues. Another research group found that many genes with de novo promoter hypermethylation in colon cancer were among the subset of genes "bivalently" marked in embryonic stem cells and adult stem/progenitor cells by repressive Polycomb group proteins (PcG), which are known for maintaining low, but poised, transcription.These observations provide a clue that CGI promoter hypermethylation in cancers is associated with PcG target genes in pre-cancerous tissues.we took advantage of ChIP-BS-seq technology and applied it to examine H3K27me3 and H3K4me3 profiles for one normal lymphoblastoid cell line (YH) and three cancer cell lines including one cervical cancer cell line (Hela) and two gastric cancer (GC) cell lines (BGC-823 and AGS). We aplied ChIP-BS technology to examine H3K27me3 marks, which are catalyzed by the SET domain histone methyltransferase EZH2 and have a repressive function with 50bp pair-end sequencing. found H3K27me3 marks were enriched preferentially at CpG islands, (+/-500) transcription start sites (TSSs) and exons in two GC cell lines (BGC-823 and AGS). In YH cells, H3K27me3 marks were only preferentially enriched at CpG islands. In contrast, Hela cells presented a reverse pattern with highest H3K27me3 enrichment in intergenic regions. To confirm this result in Hela cells, we performed two independent replicates of ChIP-Seq and ChIP-BS-seq. Cause of useful was relative small. we still sequenced one 100bp pe reads replicate for H3K4me3 and two replicate for H3K27me3 ChIP-BS-seq.

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Sequential ChIP-bisulfite sequencing enables direct genome-scale investigation of chromatin and DNA methylation cross-talk

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