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GC-rich Sequence Elements Recruit Polycomb Repressive Complex 2 (PRC2) in ES cells

ABSTRACT: Polycomb proteins are epigenetic regulators that localize to developmental loci in the early embryo where they mediate lineage-specific gene repression. In Drosophila, these repressors are recruited to sequence elements by DNA binding proteins associated with Polycomb repressive complex 2 (PRC2). However, the sequences that recruit PRC2 in mammalian cells have remained obscure. To address this, we integrated a series of engineered bacterial artificial chromosomes into embryonic stem (ES) cells and examined their chromatin. We found that a 44 kb region corresponding to the Zfpm2 locus initiates de novo recruitment of PRC2. We then pinpointed a CpG island within this locus as both necessary and sufficient for PRC2 recruitment. Based on this causal demonstration and prior genomic analyses, we hypothesized that large GC-rich elements depleted of activating transcription factor motifs mediate PRC2 recruitment in mammals. We validated this model in two ways. First, we showed that a constitutively active CpG island is able to recruit PRC2 after excision of a cluster of activating motifs. Second, we showed that two 1 kb sequence intervals from the E. coli genome with GC-contents comparable to a mammalian CpG island are both capable of recruiting PRC2 when integrated into the ES cell genome. Our findings demonstrate a causal role for GC-rich sequences in PRC2 recruitment and implicate a specific subset of CpG islands depleted of activating motifs as instrumental for the initial localization of this key regulator in mammalian genomes.

ORGANISM(S): Mus musculus

PROVIDER: GSE25197 | GEO | 2010/11/23

SECONDARY ACCESSION(S): PRJNA134307

REPOSITORIES: GEO

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GC-rich Sequence Elements Recruit Polycomb Repressive Complex 2 (PRC2) in ES cells

Project description:Polycomb proteins are epigenetic regulators that localize to developmental loci in the early embryo where they mediate lineage-specific gene repression. In Drosophila, these repressors are recruited to sequence elements by DNA binding proteins associated with Polycomb repressive complex 2 (PRC2). However, the sequences that recruit PRC2 in mammalian cells have remained obscure. To address this, we integrated a series of engineered bacterial artificial chromosomes into embryonic stem (ES) cells and examined their chromatin. We found that a 44 kb region corresponding to the Zfpm2 locus initiates de novo recruitment of PRC2. We then pinpointed a CpG island within this locus as both necessary and sufficient for PRC2 recruitment. Based on this causal demonstration and prior genomic analyses, we hypothesized that large GC-rich elements depleted of activating transcription factor motifs mediate PRC2 recruitment in mammals. We validated this model in two ways. First, we showed that a constitutively active CpG island is able to recruit PRC2 after excision of a cluster of activating motifs. Second, we showed that two 1 kb sequence intervals from the E. coli genome with GC-contents comparable to a mammalian CpG island are both capable of recruiting PRC2 when integrated into the ES cell genome. Our findings demonstrate a causal role for GC-rich sequences in PRC2 recruitment and implicate a specific subset of CpG islands depleted of activating motifs as instrumental for the initial localization of this key regulator in mammalian genomes. Analysis of YY1 binding in two cell types

2010-11-23 | E-GEOD-25197 | biostudies-arrayexpress

Mtf2 is a methylation-sensitive DNA-binding recruiter of Polycomb

Project description:Polycomb repression of gene expression is critical for development, with a pivotal role for trimethylation of lysine 27 of histone H3 (H3K27me3) deposited by Polycomb Repressive Complex 2 (PRC2). While the function and regulation of PRC2 have been extensively studied, the mechanism(s) by which it is recruited to specific genomic targets has remained largely elusive, in particular in vertebrates. Here we identify the PRC2-associated protein Mtf2 as a novel DNA methylation-sensitive PRC2 recruiter in mouse embryonic stem cells (mESCs). Mtf2 directly binds to DNA and is essential for recruitment of PRC2 both in vitro and in vivo. Genome-wide recruitment of the PRC2 catalytic subunit Ezh2 to genomic targets is drastically impaired in Mtf2 knock-out mESCs, resulting in largely reduced H3K27me3 deposition. Mtf2 selectively binds regions with high density of closely spaced unmethylated CpG-containing motifs with a locally unwound helical structure. This binding is dependent on one of the Mtf2 PHD domains, a protein domain shared among Pcl homologs, and an Mtf2-specific domain. The sequences bound by Mtf2 are enriched in PRC2-repressed CpG island-containing targets in zebrafish, Xenopus, mouse and human, suggesting that Mtf2-mediated PRC2 recruitment to unmethylated genomic regions is conserved among vertebrates.

2018-05-07 | PXD005821 | Pride

Polycomb-like proteins link the PRC2 complex to CpG islands

Project description:The Polycomb repressive complex 2 (PRC2) mainly mediates transcriptional repression and has essential roles in various biological processes including the maintenance of cell identity and proper differentiation. Polycomb-like (PCL) proteins, such as PHF1, MTF2 and PHF19, are PRC2-associated factors that form sub-complexes with PRC2 core components, and have been proposed to modulate the enzymatic activity of PRC2 or the recruitment of PRC2 to specific genomic loci. Mammalian PRC2-binding sites are enriched in CG content, which correlates with CpG islands that display a low level of DNA methylation. However, the mechanism of PRC2 recruitment to CpG islands is not fully understood. Here we solve the crystal structures of the N-terminal domains of PHF1 and MTF2 with bound CpG-containing DNAs in the presence of H3K36me3-containing histone peptides. We show that the extended homologous regions of both proteins fold into a winged-helix structure, which specifically binds to the unmethylated CpG motif but in a completely different manner from the canonical winged-helix DNA recognition motif. We also show that the PCL extended homologous domains are required for efficient recruitment of PRC2 to CpG island-containing promoters in mouse embryonic stem cells. Our research provides the first, to our knowledge, direct evidence to demonstrate that PCL proteins are crucial for PRC2 recruitment to CpG islands, and further clarifies the roles of these proteins in transcriptional regulation in vivo.

2017-09-06 | GSE97805 | GEO

An epigenetic mark of polycomb response elements implemented by Trx/MLL/COMPASS

Project description:In Drosophila, Polycomb Response Elements (PREs) are identified as genomic sequences allowing the maintenance of transcriptional repression in the absence of the initiating signal. Although PREs in Drosophila are well characterized, the existence of mammalian PRE-like elements remains debated. Accumulating evidence supports a model in which CpG islands function to recruit Polycomb-Group complexes (PcG), however, it is not evident which subclasses of CpG islands serve as PREs. Trithorax (Trx), which is required for positive regulation of gene expression in Drosophila, is known to co-bind Drosophila PREs where it is thought to antagonize polycomb-dependent silencing of nearby genes. Here, we demonstrate the existence of Trx-dependent H3K4 dimethylation loci that specifically mark Drosophila PREs and are required for the maintenance of expression of the nearby genes. Similarly, in human cells, we find ~ 3000 MLL1 (human Trx homologue)-dependent H3K4 dimethylation loci, which correlate strongly with CpG island density. In the absence of MLL1 and H3K4 dimethylation at these loci, there is an increase in H3K27 trimethylation levels, suggesting these sites can recruit Polycomb Repressive Complex 2 (PRC2). By inhibiting PRC2-dependent silencing in the absence of MLL1, we establish that a balance exists between MLL1 and PRC2, and their respective capacity to maintain or repress transcription. Thus, by investigating a conserved function between Trx and MLL1, we provide rules for the identification of CpG island subclasses serving as PRE-like sequences within the human genome. To examine changes in histone-modification profiles and gene expression after depletion of Trx in Drosophila S2 cells, and MLL1 in human HCT116 cells. We also treated MLL1-NULL HCT116 cells with GSK126 (5uM) for 4 days and measured changes in gene expression.

2016-07-26 | E-GEOD-81795 | biostudies-arrayexpress

An epigenetic mark of polycomb response elements implemented by Trx/MLL/COMPASS

2016-07-26 | GSE81795 | GEO

In embryo analysis of H3K27 trimethylation suggests a two-step process involving PRC2 interacting sequences and high GC content

Project description:ABSTRACT Polycomb group (PcG) proteins are essential for the repression of key developmental regulators during development. In Drosophila, the polycomb repressive complexes (PRC) associate with defined DNA sequences termed polycomb response elements (PREs). In mammals, however, the mechanisms underlying polycomb recruitment at targeted loci are poorly understood. We have used an in vivo approach to try and map DNA sequences of importance for the proper recruitment of polycomb proteins within the genetically well-characterized HoxD genomic locus. Here, we report that relatively small polycomb interacting sequences appear necessary and sufficient to confer polycomb recognition and targeting to ectopic loci. These elements synergize, when clustered together, to form a fully functional repressive domain. In addition, a high GC content, while not sufficient to recruit PRC2, may help its local spreading. We discuss the importance of PRC2 recruitment over Hox gene clusters, in embryonic stem cells, for their subsequent coordinated transcriptional activation during development. ChIP-chip using K27 antibodies

2015-01-27 | E-GEOD-43915 | biostudies-arrayexpress

Nucleotide composition-linked divergence of vertebrate core promoter architecture

Project description:Transcription initiation involves the recruitment of basal transcription factors to the core promoter. A variety of core promoter elements exists, however for most of these motifs the distribution across species is unknown. Here we report on the comparison of human and amphibian promoter sequences. We have used oligo-capping in combination with deep sequencing to determine transcription start sites in Xenopus tropicalis. To systematically predict regulatory elements we have developed a de novo motif finding pipeline using an ensemble of computational tools. A comprehensive comparison of human and amphibian promoter sequences revealed both similarities and differences in core promoter architecture. Some of the differences stem from a highly divergent nucleotide composition of Xenopus and human promoters. Whereas the distribution of some core promoter motifs is conserved independent of species-specific nucleotide bias, the frequency of another class of motifs correlates with the single nucleotide frequencies. This class includes the well-known TATA box and SP1 motifs, which are more abundant in Xenopus and human promoters, respectively. While these motifs are enriched above the local nucleotide background in both organisms, their frequency varies in step with this background. These differences are likely adaptive as these motifs can recruit TFIID to either CpG island or sharply initiating promoters. Our results highlight both conserved and diverged aspects of vertebrate transcription, most notably showing co-opted motif usage to recruit the transcriptional machinery to promoters with diverging nucleotide composition. This shows how sweeping changes in nucleotide composition are compatible with highly conserved mechanisms of transcription initiation. ChIP-seq profiles of TBP in Xenopus tropicalis stage 12 embryos and TSS-seq profiles of Xenopus oocytes and stage 12 embryos

2010-12-30 | E-GEOD-21482 | biostudies-arrayexpress

CpG islands and GC content dictate nucleosome depletion in a transcription independent manner at mammalian promoters

Project description:This SuperSeries is composed of the following subset Series: GSE38560: CpG islands and GC content dictate nucleosome depletion in a transcription independent manner at mammalian promoters (RNA-seq) GSE38561: CpG islands and GC content dictate nucleosome depletion in a transcription independent manner at mammalian promoters (ChIP-seq) GSE38562: CpG islands and GC content dictate nucleosome depletion in a transcription independent manner at mammalian promoters (genomic SEQ) GSE38563: CpG islands and GC content dictate nucleosome depletion in a transcription independent manner at mammalian promoters (MNase-seq) GSE38564: CpG islands and GC content dictate nucleosome depletion in a transcription independent manner at mammalian promoters (5) Refer to individual Series

2012-06-11 | E-GEOD-38577 | biostudies-arrayexpress

Mapping polycomb complexes in human and mouse embryonic stem cells

Project description:In embryonic stem (ES) cells, bivalent chromatin domains with overlapping repressive (H3 lysine 27 tri-methylation) and activating (H3 lysine 4 tri-methylation) histone modifications mark the promoters of more than 2000 genes. To gain insight into the structure and function of bivalent domains, we mapped key histone modifications and subunits of Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) genomewide in human and mouse ES cells by chromatin immunoprecipitation followed by ultra high-throughput sequencing. We find that bivalent domains can be segregated into two classes: the first occupied by both PRC2 and PRC1 (PRC1-positive) and the second specifically bound by PRC2 (PRC2-only). PRC1-positive bivalent domains appear functionally distinct as they more efficiently retain lysine 27 tri-methylation upon differentiation, show stringent conservation of chromatin state, and associate with an overwhelming number of developmental regulator gene promoters. We also used computational genomics to search for sequence determinants of Polycomb binding. This analysis revealed that the genomewide locations of PRC2 and PRC1 can be largely predicted from the locations, sizes and underlying motif contents of CpG islands. We propose that large CpG islands depleted of activating motifs confer epigenetic memory by recruiting the full repertoire of Polycomb complexes. Keywords: cell type comparison Suz12, Ezh2, Ring1b ChIP-Seq in singlicate from mouse embryonic stem (mES) cells. H3K4me3, H3K27me3, H3K36me3, Ezh2 and Ring1b ChIP-Seq in singlicate from human embyonic stem cells (hES; H9).

2008-11-01 | E-GEOD-13084 | biostudies-arrayexpress

CpG islands recruit a histone H3 lysine 36 demethylase [Agilent data]

Project description:Transcription factors that bind small DNA motifs embedded in promoters play a central role in controlling gene expression. However, in addition to these elements, up to 70% of genes in higher eukaryotes also have high levels of non-methylated cytosine/guanine base pairs (CpGs) surrounding promoters and gene regulatory units. These features, called CpG islands, were identified over twenty years ago but there remains little mechanistic evidence to suggest how these enigmatic elements contribute to promoter function, with the exception that they are refractory to epigenetic silencing by DNA methylation. Here we show that CpG islands directly recruit the H3K36 specific lysine demethylase enzyme KDM2A. Genome wide analyses by ChIP-seq demonstrated a striking global association of KDM2A with CpG islands. Nucleation of KDM2A at these elements resulted in removal of H3K36 methylation creating CpG island chromatin that is uniquely depleted of this modification. KDM2A utilizes a zinc finger CxxC (ZF-CxxC) domain that specifically recognizes non-methylated CpG DNA and binding is blocked when the CpG DNA is methylated, thus constraining KDM2A to nonmethylated CpG islands. These data expose a remarkably straightforward mechanism through which KDM2A delineates a unique architecture that differentiates CpG island chromatin from bulk chromatin.

2010-04-27 | GSE21201 | GEO

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