Project description:Transcription factors that play key roles in regulating embryonic stem (ES) cell state have been identified, but the chromatin regulators that help maintain ES cells are less well understood. A high-throughput shRNA screen was used to identify novel chromatin regulators that influence ES cell state. Loss of histone H3K9 methyltransferases, particularly SetDB1, had the most profound effects on ES cells. ChIP-Seq and functional analysis revealed that SetDB1 and histone H3K9 methylated nucleosomes occupy and repress genes encoding developmental regulators. These SetDB1-occupied genes are a subset of the M-bM-^@M-^\bivalentM-bM-^@M-^] genes, which contain nucleosomes with H3K4me3 and H3K27me3 modifications catalyzed by trithorax and polycomb group proteins, respectively. These genes are subjected to repression by both polycomb group proteins and SetDB1, and loss of either regulator can destabilize ES cell state. ChIP-seq data for SetDB1 and H3K9me3 in mouse ES cells.
Project description:Transcription factors that play key roles in regulating embryonic stem (ES) cell state have been identified, but the chromatin regulators that help maintain ES cells are less well understood. A high-throughput shRNA screen was used to identify novel chromatin regulators that influence ES cell state. Loss of histone H3K9 methyltransferases, particularly SetDB1, had the most profound effects on ES cells. ChIP-Seq and functional analysis revealed that SetDB1 and histone H3K9 methylated nucleosomes occupy and repress genes encoding developmental regulators. These SetDB1-occupied genes are a subset of the “bivalent” genes, which contain nucleosomes with H3K4me3 and H3K27me3 modifications catalyzed by trithorax and polycomb group proteins, respectively. These genes are subjected to repression by both polycomb group proteins and SetDB1, and loss of either regulator can destabilize ES cell state.
Project description:Epigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators. To determine the genome-wide distribution of Tet1 in mouse ES cells, we have performed ChIP-seq experiments using Tet1 antibodies in control knockdown (KD) and Tet1 KD ES cells.
Project description:Epigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators. Mouse ES cells infected with control knockdown (KD) or Tet1 KD lentiviruses were FACS-sorted for RNA extraction and hybridization on Affymetrix microarrays. We also investigated the effect of Nanog overexpression (OE) in Tet1 KD mouse ES cells on dys-regulated Tet1 targets. We have collected four biologically independent replicates for each treatment.
Project description:Epigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators. Chromatin or genomic DNA extracted from control (Con) or Tet1 knockdown (KD) mouse ES cells was immunoprecipitated with indicated antibodies and analyzed by NimbleGen 2.1M mouse whole genome tiling microarrays (a 4-array set covering the entired non-repetitive portion of mouse genome). Whole cell extract (WCE) was used as input controls in IP/input experiments. In IP/IP experiments, immunoprecipitated DNA from Con KD and Tet1 KD ES cells was directly compared on the same microarrays.
Project description:Epigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators.
Project description:Epigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators.
Project description:Epigenetic modification of the mammalian genome by DNA methylation (5-methylcytosine) has a profound impact on chromatin structure, gene expression and maintenance of cellular identity. Recent demonstration that members of the Ten-eleven translocation (Tet) family proteins can convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) raised the possibility that Tet proteins are capable of establishing a distinct epigenetic state. We have recently demonstrated that Tet1 is specifically expressed in murine embryonic stem (ES) cells and is required for ES cell self-renewal and maintenance. Using chromatin immunoprecipitation coupled with high-throughput DNA sequencing (ChIP-seq), here we show that Tet1 is preferentially bound to CpG-rich sequences at promoters of both transcriptionally active and Polycomb-repressed genes. Despite a general increase in levels of DNA methylation at Tet1 binding-sites, Tet1 depletion does not lead to down-regulation of all the Tet1 targets. Interestingly, while Tet1-mediated promoter hypomethylation is required for maintaining the expression of a group of transcriptionally active genes, it is also required for repression of Polycomb-targeted developmental regulators. Tet1 contributes to silencing of this group of genes by facilitating recruitment of PRC2 to CpG-rich gene promoters. Thus, our study not only establishes a role for Tet1 in modulating DNA methylation levels at CpG-rich promoters, but also reveals a dual function of Tet1 in promoting transcription of pluripotency factors as well as participating in the repression of Polycomb-targeted developmental regulators.
Project description:We report the application of single-molecule-based sequencing technology for high-throughput profiling of histone modifications in mammalian cells and characterized genome-wide SetDB1 binding and H3K9 trimethylation (H3K9me3) profiles in mouse ES cells and uncovered two distinct classes of SetDB1 binding sites, termed solo and ensemble peaks. The solo peaks were devoid of H3K9me3 and enriched near developmental regulators while the ensemble peaks were associated with H3K9me3. A subset of the SetDB1 solo peaks, particularly those near neural development related genes, was found to be associated with Polycomb Repressive Complex 2 (PRC2) as well as PRC2-interacting proteins Jarid2 and Mtf2. Genetic deletion of Setdb1 dramatically reduced Ezh2 binding as well as histone 3 lysine 27 (H3K27) trimethylation level at SetDB1 solo peaks and facilitated neural differentiation. Furthermore, we found that H3K27me3 inhibits SetDB1 methyltransferase activity in vitro. The currently identified reciprocal action between SetDB1 and PRC2 reveals a novel mechanism underlying ES cell pluripotency and differentiation regulation. Examination of 2 different histone modifications in 2 cell status.
Project description:Polycomb group proteins are essential for early development in metazoans but their contributions to human development are not yet well understood. We have mapped the Polycomb Repressive Complex 2 (PRC2) subunit Suz12 across the entire non-repeat portion of the genome in human embryonic stem (ES) cells. We found that Suz12 is distributed across large portions of over two hundred genes encoding key developmental regulators. These genes are occupied by nucleosomes trimethylated at histone H3K27, are transcriptionally repressed, and contain some of the most highly conserved non-coding elements in the vertebrate genome. We found that preferential activation of PRC2 target genes occurs during differentiation of ES cells into other cell types. The ES cell transcriptional regulators Oct4, Sox2 and Nanog co-occupied a significant subset of these genes, further supporting a link between repression of developmental regulators and stem cell pluripotency. These results indicate that PRC2 occupies a special set of developmental genes in ES cells that must be repressed to maintain pluripotency and that are poised for activation during ES cell differentiation.