CpG Island Structure and Trithorax/Polycomb Chromatin Domains in Human Cells
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE39137 | GEO | 2012/07/06
SECONDARY ACCESSION(S): PRJNA170073
REPOSITORIES: GEO
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Project description:TrxG and PcG complexes play key roles in the epigenetic regulation of development through H3K4me3 and H3K27me3 modification at specific sites throughout the human genome, but how these sites are selected is poorly understood. We find that in pluripotent cells, clustered CpG islands at genes predict occupancy of H3K4me3 and H3K27me3, and these "bivalent" chromatin domains precisely span the boundaries of CpG island clusters. Examination of two histone modifications (H3K4me3 and H3K27me3) in human induced pluripotent stem (hiPS) M23F cells.
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Project description:The selective expression is pivotal in orchestrating human development, with the Trithorax Group (TrxG) and Polycomb Group (PcG) complexes playing crucial roles in transcriptional activation and repression, respectively. However, mechanism underlying selective regulation of transcription by TrxG and PcG remains poorly understood. In this study, RYBP was observed to interact with TrxG and PcG components. RYBP and TrxG co-localized loci selectively enriches RING1B. STAT3 enriches at RYBP-TrxG co-localized loci devoid of RING1B, while displaying minimal enrichment at RING1B-enrichred loci. Introduction of STAT3 at RYBP loci disrupted RING1B aggregation and chromatin binding. RYBP-deficiency impairs TrxG deposition at DNA repair genes in RYBP-TrxG loci, consequently diminishing their expression and inducing DNA damage. These results facilitate the transition of embryonic stem cells to 2-cell-like cells. Additionally, RYBP-deficiency attenuates PcG deposition at lineage-specific genes within RYBP-TrxG-RING1B loci, thereby promoting ESC differentiation. Collectively, these results provide novel insights into the selective regulation of gene expression.
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Project description:PcG and TrxG are important epigenetic regulators of genome expression. Here we have determined genomic distributions of PC, E(Z), H3K27me3, TRX, ASH1, RNA Pol II, H3K4me3, H3K27ac in cultured Drosophila ML-DmD23-c4 cells by hybridization of ChIP products with tiling microarrays
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Project description:PcG and TrxG are important epigenetic regulators of genome expression. Here we have determined genomic distributions of PC, E(Z), H3K27me3, TRX, ASH1, RNA Pol II, H3K4me3, H3K27ac in cultured Drosophila ML-DmBG3-c2 cells by hybridization of ChIP products with tiling microarrays.
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Project description:During Drosophila development, Polycomb-group and Trithorax-group proteins function to ensure correct maintenance of transcription patterns by epigenetically repressing or activating target gene expression. To get a deep insight into the PcG and trxG pathways, we investigated a BRCT domain-containing protein called PTIP, which was generally identified as a transcriptional coactivator and belongs to the TRR complex. At the genome scale, we sorted given PTIP binding peaks into two groups: PTIP/TRR-cobound and PTIP/PC-cobound peaks. In particular, we found that PTIP mediates the molecular switch between H3K4me3/H3K27ac and H3K27me3 histone modifications at TRR or PC occupied regions. Thus, we suggest that PTIP is a mediator rather than a dedicated co-activator along PcG and trxG pathways. Our hypothesis is further supported by the genetic assay: PTIP interacts genetically with either PcG or TrxG in a dosage-dependent manner, suggesting that PTIP functions as a co-factor of PcG/TrxG proteins. In addition, in accordance with the analysis of ChIP-seq, these genetic interactions correlate with modified ectopic HOX protein levels in imaginal discs, which reveals an essential role for PTIP in PcG-mediated Hox gene repression. Hence, we reveal a novel role for PTIP in the epigenetic regulation of gene expression along PcG and trxG pathways.
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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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Project description:CpG islands (CGIs) are key DNA regulatory elements in the vertebrate genome and are often found at gene promoters. In mammalian embryonic stem (ES) cells, CGIs are decorated by either the active or repressive histone marks, H3K4me3 and H3K27me3, respectively, or by both modifications (‘bivalent domains’), but their precise regulation is incompletely understood. Remarkably, we find that the polycomb repressive complex 2 (PRC2)-associated protein C17orf96 (a.k.a. esPRC2p48 and E130012A19Rik) is present at most CGIs in mouse ES cells. At PRC2-rich CGIs, loss of C17orf96 results in an increased chromatin binding of Suz12 and elevated H3K27me3 levels concomitant with gene repression. In contrast, at PRC2-poor CGIs, located at actively transcribed genes, C17orf96 colocalizes with RNA polymerase II and its depletion leads to a focusing of H3K4me3 in the core of CGIs. Our findings thus identify C17orf96 as a novel context-dependent CGI regulator. ChIP-seq of C17orf96, H3K4me3 and H3K27me3 in mouse ES cells (E14).
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Project description:Trithorax group (TrxG) and Polycomb group (PcG) proteins are two mutually antagonistic chromatin modifying complexes, however, how they together mediate transcriptional counterregulation remains unknown. Genome-wide analysis revealed that binding of Ezh2 and Menin, central members of the PcG and TrxG complexes, respectively, were reciprocally correlated. Moreover, we identified a developmental change in the positioning of Ezh2 and Menin in differentiated T lymphocytes compared to embryonic stem cells. Ezh2-binding upstream and Menin-binding downstream of the transcription start site (TSS) was frequently found at genes with higher transcriptional levels, and Ezh2-binding downstream and Menin-binding upstream was found at genes with lower expression in T lymphocytes. Interestingly, of the Ezh2 and Menin co-occupied genes, those exhibiting occupancy at the same position displayed greatly enhanced sensitivity to loss of Ezh2. Finally, we also found that different combinations of Ezh2 and Menin occupancy were associated with expression of specific functional gene groups important for T cell development. Therefore, spatial cooperative gene regulation by the PcG and TrxG complexes may represent a novel mechanism regulating the transcriptional identity of differentiated cells. ES cells, B cells and T cells are profiled for mRNA expression
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Project description:Trithorax group (TrxG) and Polycomb group (PcG) proteins are two mutually antagonistic chromatin modifying complexes, however, how they together mediate transcriptional counterregulation remains unknown. Genome-wide analysis revealed that binding of Ezh2 and Menin, central members of the PcG and TrxG complexes, respectively, were reciprocally correlated. Moreover, we identified a developmental change in the positioning of Ezh2 and Menin in differentiated T lymphocytes compared to embryonic stem cells. Ezh2-binding upstream and Menin-binding downstream of the transcription start site (TSS) was frequently found at genes with higher transcriptional levels, and Ezh2-binding downstream and Menin-binding upstream was found at genes with lower expression in T lymphocytes. Interestingly, of the Ezh2 and Menin co-occupied genes, those exhibiting occupancy at the same position displayed greatly enhanced sensitivity to loss of Ezh2. Finally, we also found that different combinations of Ezh2 and Menin occupancy were associated with expression of specific functional gene groups important for T cell development. Therefore, spatial cooperative gene regulation by the PcG and TrxG complexes may represent a novel mechanism regulating the transcriptional identity of differentiated cells.
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