The PRC2-associated factor C17orf96 is a novel CpG island regulator in mouse ES cells
ABSTRACT: 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).
Project description:Binding of Polycomb repressive complex 2 (PRC2) and chromatin composition of the inactive X (Xi) before, during and after X chromosome inactivation reveal that spreading is driven by a combination of Xi-specific strong and moderate Ezh2 sites. Sequence context of these sites shows a moderate enrichment of SINEs and simple repeats. The general pattern of Ezh2 and H3K27me3 distribution over the chromosome reflect a graded concentration originating from strong Ezh2 sites, around which moderate sites are clustered, suggesting a hierarchy of Ezh2 sites govern spreading. ChIP-seq of Ezh2 and H3K27me3 as well as the three active marks H3K4me3, H3K36me3 and RNA-POLII-serine5 phosphorylation (RNA-polII-S5P) in female cell lines: undifferentiated embryonic stem (ES) cells (d0), differentiating ES cells (d7) and a transformed embryonic fibroblast cell line (MEF).
Project description:Embryogenesis requires the timely and coordinated activation of developmental regulators. It has been suggested that the recently discovered class of histone demethylases (UTX and JMJD3) that specifically target the repressive H3K27me3 modification play an important role in the activation of “bivalent” genes in response to specific developmental cues. To determine the requirements for UTX in pluripotency and development, we have generated Utx null ES cells and mutant mice. The loss of UTX had a profound effect during embryogenesis. Utx null embryos had reduced somite counts, neural tube closure defects and heart malformation which presented between E9.5 and E13.5. Unexpectedly, homozygous mutant female embryos were more severely affected than hemizygous mutant male embryos. In fact, we observed the survival of a subset of UTX-deficient males which were smaller in size and had reduced life-span. Interestingly, these animals were fertile with normal spermatogenesis. Consistent with a mid-gestation lethality, UTX null male and female ES cells gave rise to all three germ layers in teratoma assays although sex-specific differences could be observed in the activation of developmental regulators in embryoid body assays. Lastly, ChIP-seq analysis revealed an increase in H3K27me3 in Utx null male ES cells. In summary, our data demonstrate sex-specific requirements for this X-linked gene while suggesting a role for UTY during development. Examination of H3K27me3 and H3K4me3 in UtxKO ES cells (V6.5 background) vs UtxFlx (V6.5 background) ES cells grown in LIF containing ES cell media or treated with retinoic acid without LIF.
Project description:This study describes the epigenetic profiling of the X chromosome during X inactivation. It includes H3K4me3 and H3K27me3 ChIP-Seq profiles of male (E14) and female (LF2 and XT67E1) mouse ES cells, together with their differentiated derivatives (either 4d atRA or 10d EB). It also includes ChIP-chip profiles around the Xic on chromosome X of H3K4me3, H3K27me3, H3K9me2, H3K36me3, Pol II, TBP, H3-Core as well as expression, using male (E14) and female (LF2) mouse ES cells, together with their differentiated derivatives (either 4d atRA or 10d EB). Examination of two different histone modifications in 3 cell lines under 3 conditions using ChIP-Seq. Examination of five different histone modifications two transcription factors and gene expression under three conditions in 2 cell lines using ChIP-chip.
Project description:H3K27me3 represses developmental genes at initial embryonic stages. The KDM6 family, comprised of UTX and JMJD3, are the only known proteins that demethylate H3K27me3 and they are hypothesized to catalyze the rapid removal of repressive chromatin in early mammalian development. However, we report that male embryos carrying mutations in both Utx and Jmjd3 survive to term and appear phenotypically normal at mid-gestation. We utilize several cell culture models to demonstrate that H3K27me3 is lost from repressed promoters in the absence of active KDM6 demethylation. Our data indicate that KDM6 H3K27me3 demethylation is not essential in the early embryo and that H3K27me3 loss from developmental genes occurs via novel mechanisms. Examination of 2 different histone modifications (H3K27me3 and H3K4me3) in 2 cell types (ES and retinoic acid treated ES cells) comparing WT to UTX and JMJD3 KOs. In ES cells, there are two WT replicates and two KO replicates, both measuring H3K27me3, and one replicate measuring input. In retinoic acid treatment, there are two replicates each for measuring H3K27me3 and H3K4me3 in WT and KO cell lines, and one replicate measuring input.
Project description:Polycomb group proteins are transcriptional repressors that play essential roles in regulating genes required for differentiation and embryonic development. The Polycomb repressive complex 2 (PRC2) contains the methyltransferase activity for lysine 27 on histone 3 (H3K27me3), which is a docking site for the PRC1 complex and leads to gene repression. However, the role of other histone modifications in regulating PRC2 activity is just beginning to be understood. Here we show that direct recognition of histone H3 methylated at lysine 36 (H3K36me), an mark associated with activation, by the PRC2 subunit Phf19 is required for the full enzymatic activity of the PRC2 complex. We provide structural evidence for this interaction by nuclear magnetic resonance spectroscopy (NMR). Using genome-wide chromatin binding analyses and expression analyses, we show that Phf19 binds to a subset of PRC2 targets in embryonic stem (ES) cells, and that this is required for their repression and for H3K27me3 deposition. These findings reveal that the H3K36me2/3-Phf19 interaction is essential for PRC2 complex activity and for proper regulation of gene repression in ES cells. We determined the genome binding/occupancy profile of Phf19, H3K36me3, H3K36me2, H3K27me3 and Suz12 by high throughput sequencing in mouse embryonic stem cells. For Phf19 two independent biological replicas were performed and Phf19 binding sites were defined as those sites (ChIP-seq peaks) present in both replicas. H3K27me3 was evaluated in control ES cells and cells depleted of Phf19 (shRd and shPhf19 respectively).
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.
Project description:We report the application of single molecule-based sequencing technology in combination with CXXC affinity purifcation (CAP-seq), MBD affinity purification (MAP-seq) and chromatin immunoprecipitation (ChIP-seq) to generate reciprocal methylation and chromatin modifcation maps in human and mouse. We find that contrary to sequence based prediction methods that humans and mice possess highly equivalent compliments of CpG islands (CGIs). The majority of these CGIs are positive for the active histone modification; H3K4me3 in embryonic stem cells (ES cells) the magnitude of which is correlated with the local density of non-methylated CpG. Approximately half of the human and mouse CGIs are distal to annotated gene promoters, yet more than 40% identify unanticipated transcription start sites as defined by RNA polymerase occupancy and published RNA mapping data. These orphans CGIs preferentially acquire DNA methylation in somatic cells, and this corresponds with a loss of H3K4me3 and RNA polymerase II at these sites. Conversely abnormal CGI methylation found in colorectal tumours showed a distinct distribution relative to that found in normal somatic tissues displaying preferential association with loci marked by H3K27me3 in human ES cells. This study provides a comprehensive functional assessment of CGIs in normal and diseased tissues. Examination of CGI methylation status in human and mouse primary tissues.
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 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 Polycomb repressive complex 2 (PRC2) is important for the maintenance of stem cell pluripotency and suppression of cell differentiation by promoting histone H3 lysine 27 trimethylation (H3K27me3) and silencing expression of genes regulating differentiation. Here we show decreased expression of BRCA1 promotes EZH2 re-targeting genome wide and enhances H3K27me3 levels at PRC2 target loci in mouse ES cells. R1 mouse ES cells were transfected with control siRNA and Brca1 specific siRNA. At 48h after transfection, cells were harvested and subjected to ChIP assay with Ezh2 antibody. Brca1 wild-type (AB2.2) and Brca1 deficient (PL2F8) mouse ES cells were harvested and subjected to ChIP assay with Ezh2 antibody. Fragmented DNA obtained from ChIP assay was repaired by DNA Terminator End Repair Kit (Lucigen Corporation, Middleton, WI) and purified by QIAquick PCR purification kit. Then two unidirectional linkers JW102 and JW103 were annealed and ligated to the blunt ends DNA at 16°C overnight. The purified products were amplified to 2 μg by LM-PCR. NimbleGen Mouse ChIP 3x720K RefSeq Promoter Array (Roche) were used for the hybridization. Relative enrichments were calculated by dividing the normalized level of ChIP DNA to that of input DNA at corresponding locus. Labeling, hybridization and washing were carried out according to manufacturer’s instructions. Experiments in AB2.2 and PL2F8 cells were performed in duplicate.