Chip-chip from WT and Polycomb Component Kock Out Mouse ES cells for H2AZ, H3K27me3, EZH2 and Ring1B.
ABSTRACT: The essential histone variant H2A.Z localises to both active and silent chromatin sites. In embryonic stem cells (ESCs), H2A.Z is also reported to co-localise with polycomb repressive complex 2 (PRC2) at developmentally silenced genes. The mechanism of H2A.Z targeting is not clear, but a role for the PRC2 component Suz12 has been suggested. Given this association, we wished to determine if polycomb functionally directs H2A.Z incorporation in ESCs. We demonstrate that the PRC1 component Ring1B interacts with multiple complexes in ESCs. Moreover, we show that although the genomic distribution of H2A.Z co-localises with PRC2, Ring1B and with the presence of CpG islands, H2A.Z still blankets polycomb target loci in the absence of Suz12, Eed (PRC2) or Ring1B (PRC1). Therefore we conclude that H2A.Z accumulates at developmentally silenced genes in ESCs in a polycomb independent manner. Array design includes 2 biological replicates for all samples and technical replication (dye swaps for H3K27me3_WT_ES, EZH2_WT_ES, EZH2_RING1b_KO_ES, H2AZ_WT_ES(2), H2AZ_Eed_KO_ES and H2AZ_Suz12_KO_ES). Ring1B_WT_ES is represented by a single replicate.
Project description:The Polycomb repressive complexes PRC1 and PRC2 are key mediators of heritable gene silencing in multicellular organisms. Here we characterize AEBP2, a known PRC2 cofactor which, in vitro, has been shown to stimulate PRC2 activity. We show that AEBP2 localises specifically to PRC2 target loci, including the inactive X chromosome. Proteomic analysis confirms that AEBP2 associates exclusively with PRC2 complexes. However, analysis of embryos homozygous for a targeted mutation of Aebp2 unexpectedly revealed a Trithorax phenotype, normally linked to antagonism of Polycomb function. Consistent with this we observe elevated levels of PRC2 mediated histone H3K27 methylation at target loci in Aebp2 mutant embryonic stem cells. We further demonstrate that mutant ES cells assemble atypical hybrid PRC2 sub-complexes, potentially accounting for enhancement of Polycomb activity, and suggesting that AEBP2 normally plays a role in defining the mutually exclusive composition of PRC2 sub-complexes. H3K27me3, SUZ12, and AEBP2 ChIP-Seq in wild-type and AEBP2 KO mouse ESCs, biological replicates, pre-cleared chromatin as input, additionally FS2 ChIP-Seq in cells with FS2 tagged AEBP2, HiSeq2000
Project description:The established hierarchical model explaining co-occupancy of Polycomb repressor complexes 1 and 2 (PRC 1 and 2) at target loci proposes that the chromodomain of the polycomb protein, a core PRC1 subunit, recognises the H3K27me3 histone modification catalysed by PRC2. We used chromatin immunoprecipitation to analyse PRC1 occupancy at target loci in Eed-/- mouse embryonic stem cells (ESCs) that lack H3K27me3. Occupancy of the core PRC1 proteins Ring1B and Mel18 was strongly reduced, consistent with the hierarchical model. However, levels of H2A ubiquitylation (H2AK119u1), the histone modification catalysed by PRC1, were similar to wild-type cells, suggesting PRC1 recruitment is independent of H3K27me3. ChIP-sequencing analysis of Ring1B occupancy genome wide substantiated this conclusion, demonstrating significant Ring1B levels at polycomb target loci in Eed-/- ESCs. Thus PRC1 and PRC2 are recruited independently to sites that they co-occupy. We conclude that the primary function of H3K27me3 is to increase the residency of PRC1 at target loci and thereby to contribute to the stability of PRC1 mediated silencing. Examination of Ring1B binding in WT, Eed ko and Input of ESCs Examination of CBX7 in WT and Eed ko of ESCs
Project description:Polycomb repressive complex 1 (PRC1) catalyzes H2A monoubiquitination (uH2A) and regulates pluripotency in embryonic stem cells (ESCs). However the mechanisms controlling PRC1 recruitment and activity are largely unknown. Here we show that Fbxl10 interacts with Ring1B and Nspc1, forming a non-canonical PRC1. We demonstrate that Fbxl10-PRC1 is essential for H2A ubiquitination in mouse ESCs. Genome-wide analyses reveal that Fbxl10 preferentially binds to CpG islands and co-localizes with Ring1B on Polycomb target genes. Notably, Fbxl10 depletion causes modest dissociation of Ring1B but a major loss of uH2A on target genes. Furthermore rescue experiments for Fbxl10 reveal that its DNA binding capability and integration into PRC1 are required for proper H2A ubiquitination. ES cells lacking Fbxl10, like previously characterized Polycomb mutants, show a severely compromised capacity for successful differentiation. Our results shed light on a novel mechanism how CpG islands regulate chromatin function by affecting polycomb recruitment and activity. All ChIP-seq reactions were performed in either untransfected cells, cells expressing scrambled shRNA or Fbxl10 shRNA, Ring1b-/- or Suz12-/- mouse ES cells
Project description:The chromatin modifying activities inherent to polycomb repressive complexes PRC1 and PRC2 play an essential role in gene regulation, cellular differentiation, and development. However, the mechanisms by which these complexes recognize their target sites and function together to form repressive chromatin domains remain poorly understood. Recruitment of PRC1 to target sites has been proposed to occur through a hierarchical process, dependent on the prior nucleation of PRC2 and placement of H3K27me3. Here, using a de novo targeting assay in mouse embryonic stem cells we unexpectedly discover that PRC1-dependent H2AK119ub1 leads to the recruitment of PRC2 and H3K27me3 to effectively initiate a polycomb domain. Genetic ablation of catalytic subunit of the PRC1 complex (RINGA/B) and ChIP-seq analysis of PRC1 and PRC2 components confirmed genome-wide decreases in PRC2 occupancy and H3K27me3 levels at PRC target sites. This activity is restricted to variant PRC1 complexes and genetic ablation experiments reveal that targeting of the variant PCGF1/PRC1 complex by KDM2B to CpG islands is required for polycomb domain formation and normal development. Together these observations provide a surprising new PRC1-dependent logic for PRC2 occupancy and polycomb domain formation. RING1A-/-;RING1Bfl/fl ES cells were treated with 800µM tamoxifen for 48hours and compared to untreated control cells by ChIP-seq for RING1B, SUZ12, EZH2 and H3K27me3.
Project description:The histone lysine demethylase protein, KDM2B, associates with the PCGF1/PRC1 complex and binds to non-methylated DNA through its ZF-CxxC domain, providing a possible molecular link between CpG island elements and polycomb nucleation (Farcas et al., 2012, Wu et al., 2013). Here, a novel genetic system was designed in which PCGF1/PRC1 targeting could be disrupted in vivo through the ablation of KDM2B-mediated DNA binding. To ablate PCGF1/PRC1 targeting, an exon that encodes most of the KDM2B ZF-CxxC domain and is shared by both the long and short form of the protein was flanked by loxP sites (Kdm2bfl/fl). Homozygous mouse ES cell lines were derived that also stably express a tamoxifen inducible form of CRE-recombinase. CRE induced deletion of the ZF-CxxC domain by the addition of tamoxifen yields KDM2B long and short form proteins that are incapable of binding to CpG island DNA but still remain associated with the PCGF1/PRC1 variant complex. We then assessed genome-wide occupancy of the PRC1 component RING1B and the PRC2 component SUZ12 to examine the impact of losing KDM2B-dependent targeting of polycomb. KDM2Bfl/fl ES cells were treated with 800µM tamoxifen for 72hours and compared to untreated control cells by ChIP-seq for KDM2B, RING1B and SUZ12, and RNA-seq.
Project description:Suz12(Bgal/Bgal) ESCs express a truncated form of Suz12 fused to Beta-galactosidase. These cells maintain a reduced level of H3K27me3 despite this mutation to a core component of PRC2, unlike Eed-/- ESCs whose H3K27me3 is ablated. Two ESC lines mutant in genes of core components of Polycomb Repressive Complex 2 were assessed for H3K27me3 by ChIP-seq, as compared to a wild type ESC line.
Project description:Suz12(Bgal/Bgal) ESCs express a truncated form of Suz12 fused to Beta-galactosidase. These cells maintain a reduced level of H3K27me3 despite this mutation to a core component of PRC2, unlike Eed-/- ESCs whose H3K27me3 is ablated. This data shows the concomitant changes in H3K4me3 levels in these cells. An ESC line mutant in Suz12, a core component of Polycomb Repressive Complex 2, was assessed for H3K4me3 by ChIP-seq, as compared to a wild type ESC line, as well as both lines subjected to in vitro differentiation down the Spinal Motor Neuron pathway.
Project description:Polycomb repressive complex 2 (PRC2) regulates gene expression during lineage specification through trimethylation of lysine 27 on histone H3 (H3K27me3). In Drosophila, polycomb binding sites are dynamic chromatin regions coupled to incorporation of the histone variant H3.3. Here we show in mouse embryonic stem cells (ESCs) that H3.3 is required for proper establishment of H3K27me3 at the promoters of developmentally regulated genes. These promoters show reduced dynamics as determined by deposition of de novo synthesized histones, associated with reduced PRC2 occupancy. H3.3-depleted ESCs show upregulation of extraembryonic trophectoderm, as well as misregulation of other developmental genes upon differentiation. Our data demonstrate the importance of H3.3 incorporation in ESCs and suggest that changes in chromatin dynamics in its absence lead to misregulation of gene expression during differentiation. Moreover, our findings lend support to the emerging notion that H3.3 has multiple functions in distinct genomic locations that are not always correlated with an “active” chromatin state. Native ChIP analysis of three histone post-translational modifications (H3K4me3, H3K27me3, H3K27ac) in two mouse embryonic stem cell (ESC) lines (control and H3.3-depleted). Inputs sequenced as control. Native ChIP analysis of H3.3B-HA in control and Suz12-/- ESCs. Crosslinking ChIP analysis of histone H3 using a general H3 antibody in two ESC lines (control and H3.3-depleted). Crosslinking ChIP analysis Hira, UTX, and Jmjd3 in wild type and H3.3 KO ESCs.
Project description:Chromatin modifications have been implicated in the self-renewal and differentiation of embryonic stem cells (ESCs). However, the function of histone variant H2A.Z in ESCs remains unclear. We show that H2A.Z is highly enriched at promoters and enhancers and is required for both efficient self-renewal and differentiation of murine ESCs. H2A.Z deposition leads to an abnormal nucleosome structure, decreased nucleosome occupancy and increased chromatin accessibility. In self-renewing ESCs, knockdown of H2A.Z compromises OCT4 binding to its target genes and leads to decreased binding of MLL complexes to active genes and of PRC2 complex to repressed genes in self-renewal of ESCs. During differentiation of ESCs, inhibition of H2A.Z also compromises RA-induced RARα binding, activation of differentiation markers and the repression of pluripotency genes. We propose that H2A.Z mediates such contrasting activities by acting as a 'general facilitator' that generates access for a variety of complexes both activating and repressive. ChIP-Seq in murine embryonic stem (mES) cells for H2A.Z and acetylated H2A.Z. ChIP-Seq of H3K4me3, H3K27me3, RbBP5, SUZ12 and OCT4 for mES cells of both H2A.Z RNAi knockdown and shLuc control. ChIP-Seq of RARalpha in H2A.Z knockdown (withdraw of LIF and exposure to RA for 3h) and control cells. MNase-Seq and chromatin accessibility assay using Benzonase digestion followed by next-generation sequencing for mES cells of both H2A.Z RNAi knockdown and shLuc control. ChIP-Seq of H2A.Z and H3K4me3 for mES cells of both MLL4 RNAi knockdown and shLuc control. RNA-Seq for mES cells of H2A.Z knockdown and shluc control. RNA-Seq for embryonic bodies derived from mES cells (H2A.Z knockdown and shLuc control) at day 3 and day 7.
Project description:Native ChIP on chip for H3K27me3 in murine ES cells comparing WT and Ring1B-/- cells. Paper Abstract: How polycomb group proteins repress gene expression in vivo is not known. Whilst histone modifying activities of the polycomb repressive complexes have been studied extensively, in vitro data has suggested a direct activity of the PRC1 complex in compacting chromatin. Here, we investigate higher-order chromatin compaction of polycomb targets in vivo. We show that polycomb repressive complexes are required to maintain a compact chromatin state at Hox loci in embryonic stem (ES) cells. There is specific decompaction in the absence of PRC2 or PRC1. This is due to PRC1, since decompaction occurs in Ring1B null cells that still have PRC2-mediated H3K27 methylation. Moreover, we show that the ability of Ring1B to restore a compact chromatin state, and to repress Hox gene expression in ES cells, is not dependent on its histone ubiquitination activity. We suggest that Ring1B-mediated chromatin compaction acts to directly limit transcription in vivo. Biological replicates: 3 independently grown, harvested,preplated, micrococcal nuclease digested and ChIP for H3K27me3. 5 Technical replicates.