Polycomb complexes repress developmental regulators in murine embryonic stem cells
TL;DR: It is shown that PcG proteins directly repress a large cohort of developmental regulators in murine ES cells, the expression of which would otherwise promote differentiation, and dynamic repression of developmental pathways by Polycomb complexes may be required for maintaining ES cell pluripotency and plasticity during embryonic development.
Abstract: The mechanisms by which embryonic stem (ES) cells self-renew while maintaining the ability to differentiate into virtually all adult cell types are not well understood. Polycomb group (PcG) proteins are transcriptional repressors that help to maintain cellular identity during metazoan development by epigenetic modification of chromatin structure. PcG proteins have essential roles in early embryonic development and have been implicated in ES cell pluripotency, but few of their target genes are known in mammals. Here we show that PcG proteins directly repress a large cohort of developmental regulators in murine ES cells, the expression of which would otherwise promote differentiation. Using genome-wide location analysis in murine ES cells, we found that the Polycomb repressive complexes PRC1 and PRC2 co-occupied 512 genes, many of which encode transcription factors with important roles in development. All of the co-occupied genes contained modified nucleosomes (trimethylated Lys 27 on histone H3). Consistent with a causal role in gene silencing in ES cells, PcG target genes were de-repressed in cells deficient for the PRC2 component Eed, and were preferentially activated on induction of differentiation. Our results indicate that dynamic repression of developmental pathways by Polycomb complexes may be required for maintaining ES cell pluripotency and plasticity during embryonic development.
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TL;DR: High-resolution maps for the genome-wide distribution of 20 histone lysine and arginine methylations as well as histone variant H2A.Z, RNA polymerase II, and the insulator binding protein CTCF across the human genome using the Solexa 1G sequencing technology are generated.
6,488 citations
TL;DR: Recent advances in understanding how epigenetic alterations participate in the earliest stages of neoplasia, including stem/precursor cell contributions, are reviewed and the growing implications of these advances for strategies to control cancer are discussed.
4,269 citations
Cites background from "Polycomb complexes repress developm..."
...A large group of genes is marked by PcG control in ES cells (Boyer et al., 2006; Lee et al., 2006), as well as in other more committed stem/precursor cells (Bracken et al., 2006; see also the Review by M.A. Surani et al., page 747 in this issue)....
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...A large group of genes is marked by PcG control in ES cells (Boyer et al., 2006; Lee et al., 2006), as well as in other more committed stem/precursor cells (Bracken et al....
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TL;DR: The application of single-molecule-based sequencing technology for high-throughput profiling of histone modifications in mammalian cells is reported and it is shown that chromatin state can be read in an allele-specific manner by using single nucleotide polymorphisms.
Abstract: We report the application of single-molecule-based sequencing technology for high-throughput profiling of histone modifications in mammalian cells By obtaining over four billion bases of sequence from chromatin immunoprecipitated DNA, we generated genome-wide chromatin-state maps of mouse embryonic stem cells, neural progenitor cells and embryonic fibroblasts We find that lysine 4 and lysine 27 trimethylation effectively discriminates genes that are expressed, poised for expression, or stably repressed, and therefore reflect cell state and lineage potential Lysine 36 trimethylation marks primary coding and non-coding transcripts, facilitating gene annotation Trimethylation of lysine 9 and lysine 20 is detected at satellite, telomeric and active long-terminal repeats, and can spread into proximal unique sequences Lysine 4 and lysine 9 trimethylation marks imprinting control regions Finally, we show that chromatin state can be read in an allele-specific manner by using single nucleotide polymorphisms This study provides a framework for the application of comprehensive chromatin profiling towards characterization of diverse mammalian cell populations
4,166 citations
TL;DR: The transcriptional landscape of the four human HOX loci is characterized at five base pair resolution in 11 anatomic sites and 231 HOX ncRNAs are identified that extend known transcribed regions by more than 30 kilobases, suggesting transcription of ncRNA may demarcate chromosomal domains of gene silencing at a distance.
4,003 citations
Cites background or result from "Polycomb complexes repress developm..."
...Our results confirm the existence of broad chromosomal domains of histone modifications and the occupancy of HMTases over the Hox loci observed by previous investigators (Bernstein et al., 2005; Boyer et al., 2006; Guenther et al., 2005; Lee et al., 2006; Squazzo et al., 2006) and extend on these observation in several important ways....
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...…broad chromosomal domains of histone modifications and the occupancy of HMTases over the Hox loci observed by previous investigators (Bernstein et al., 2005; Boyer et al., 2006; Guenther et al., 2005; Lee et al., 2006; Squazzo et al., 2006) and extend on these observation in several important ways....
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TL;DR: In this article, the ESC master transcription factors form unusual enhancer domains at most genes that control the pluripotent state, called super-enhancers, which consist of clusters of enhancers that are densely occupied by the master regulators and Mediator.
2,978 citations
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TL;DR: Insight is provided into the transcriptional regulation of stem cells and how OCT4, SOX2, and NANOG contribute to pluripotency and self-renewal and how they collaborate to form regulatory circuitry consisting of autoregulatory and feedforward loops.
4,447 citations
TL;DR: Results indicate that while a 3-fold reduction in levels of genomic m5C has no detectable effect on the viability or proliferation of ES cells in culture, a similar reduction of DNA methylation in embryos causes abnormal development and embryonic lethality.
3,994 citations
TL;DR: The purification and characterization of an EED-EZH2 complex, the human counterpart of the Drosophila ESC-E(Z) complex, is reported, and it is demonstrated that the complex specifically methylates nucleosomal histone H3 at lysine 27 (H3-K27).
Abstract: Polycomb group (PcG) proteins play important roles in maintaining the silent state of HOX genes. Recent studies have implicated histone methylation in long-term gene silencing. However, a connection between PcG-mediated gene silencing and histone methylation has not been established. Here we report the purification and characterization of an EED-EZH2 complex, the human counterpart of the Drosophila ESC-E(Z) complex. We demonstrate that the complex specifically methylates nucleosomal histone H3 at lysine 27 (H3-K27). Using chromatin immunoprecipitation assays, we show that H3-K27 methylation colocalizes with, and is dependent on, E(Z) binding at an Ultrabithorax (Ubx) Polycomb response element (PRE), and that this methylation correlates with Ubx repression. Methylation on H3-K27 facilitates binding of Polycomb (PC), a component of the PRC1 complex, to histone H3 amino-terminal tail. Thus, these studies establish a link between histone methylation and PcG-mediated gene silencing.
3,565 citations
TL;DR: It is found that PRC2 target genes are preferentially activated during ES cell differentiation and that the ES cell regulators OCT4, SOX2, and NANOG cooccupy a significant subset of these genes.
2,341 citations
TL;DR: The results suggest that EZH2 serves as a recruitment platform for DNA methyltransferases, thus highlighting a previously unrecognized direct connection between two key epigenetic repression systems.
Abstract: The establishment and maintenance of epigenetic gene silencing is fundamental to cell determination and function. The essential epigenetic systems involved in heritable repression of gene activity are the Polycomb group (PcG) proteins and the DNA methylation systems. Here we show that the corresponding silencing pathways are mechanistically linked. We find that the PcG protein EZH2 (Enhancer of Zeste homolog 2) interacts-within the context of the Polycomb repressive complexes 2 and 3 (PRC2/3)-with DNA methyltransferases (DNMTs) and associates with DNMT activity in vivo. Chromatin immunoprecipitations indicate that binding of DNMTs to several EZH2-repressed genes depends on the presence of EZH2. Furthermore, we show by bisulphite genomic sequencing that EZH2 is required for DNA methylation of EZH2-target promoters. Our results suggest that EZH2 serves as a recruitment platform for DNA methyltransferases, thus highlighting a previously unrecognized direct connection between two key epigenetic repression systems.
1,976 citations