Project description:In mouse development, long-term silencing by CpG island DNA methylation is specifically targeted to germline genes, however the molecular mechanisms of this specificity remain unclear. Here we demonstrate that the transcription factor E2F6, a member of the polycomb repressive complex 1.6 (PRC1.6), is critical to target and initiate epigenetic silencing at germline genes in early embryogenesis. Genome-wide, E2F6 binds preferentially to CpG islands in embryonic cells. E2F6 cooperates with MGA to silence a subgroup of germline genes in mouse embryonic stem cells and in vivo, a function that critically depends on the E2F6 marked box domain. Inactivation of E2f6 leads to a failure to deposit CpG island DNA methylation at these genes during implantation. Furthermore, E2F6 is required to initiate epigenetic silencing in early embryonic cells but becomes dispensable for the maintenance in differentiated cells. Our findings elucidate the mechanisms of epigenetic targeting of germline genes and provide a paradigm for how transient repression signals by DNA-binding factors in early embryonic cells are translated into long term epigenetic silencing during mammalian development.
Project description:Genome-wide methylation analysis was performed by methylated DNA immunoprecipitation (MeDIP)-CpG island (CGI) microarray analysis to identify the CpG methylation levels of Parp-1 wildtype, Parp-1 deficient or Parp inhibitor treated mouse embryonic stem cells.
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.
Project description:Engineering Pluripotent DNA Methylation by CpG Island Methylation Response (CIMR) to Synthetic CpG-free ssDNA Insertion Cellular differentiation requires global changes to DNA methylation (DNAme), where it functions to regulate transcription factor and chromatin remodeling activity, and genome interpretation. Here, we describe a simple DNAme engineering approach in pluripotent stem cells (PSCs), extending across large stretches of CpG dense “islands (CGIs).” Integration of synthetic CpG free single-stranded DNA (ssDNA) induces a target CpG Island Methylation Response (CIMR) in multiple PSC lines, Nt2d1 embryonal carcinoma cells, and mouse PSCs, but not in highly methylated CpG Island Methylator Phenotype (CIMP) positive cancer lines. CIMR DNAme at MLH1 spans the CGI, is robustly maintained throughout cellular differentiation, suppresses target gene activity, and sensitizes derived cardiomyocytes and thymic epithelial cells to the chemotherapy cisplatin. Additional CIMR DNAme is reported on at TP53 and ONECUT1 CGIs. Collectively, this new resource enables total CpG Island DNAme engineering in pluripotency and the genesis of novel epigenetic models of development and disease
Project description:Integration of synthetic CpG Free DNA induces de novo DNAme in the flanking CpG island. Cellular differentiation requires global changes to DNA methylation (DNAme), where it functions to regulate transcription factor and chromatin remodeling activity, and genome interpretation. Here, we describe a simple DNAme engineering approach in pluripotent stem cells (PSCs), extending across large stretches of CpG dense “islands (CGIs).” Integration of synthetic CpG free single-stranded DNA (ssDNA) induces a target CpG Island Methylation Response (CIMR) in multiple PSC lines, Nt2d1 embryonal carcinoma cells, and mouse PSCs, but not in highly methylated CpG Island Methylator Phenotype (CIMP) positive cancer lines. CIMR DNAme at MLH1 spans the CGI, is robustly maintained throughout cellular differentiation, suppresses target gene activity, and sensitizes derived cardiomyocytes and thymic epithelial cells to the chemotherapy cisplatin. Additional CIMR DNAme is reported on at TP53 and ONECUT1 CGIs. Collectively, this new resource enables total CpG Island DNAme engineering in pluripotency and the genesis of novel epigenetic models of development and disease
Project description:Rnf20 catalyzes lysine 120 mono-ubiquitination of histone H2B (H2Bub1) that has been previously involved in normal differentiation of embryonic stem (ES) and adult stem cells. However, the mechanisms underlying by which Rnf20 is recruited to its target chromosomal loci to generate H2Bub1 are still elusive. Here, we reveal that Fbxl19, a CxxC domain-containing protein, physically interacts with Rnf20, guides it preferentially to CpG island-containing target promoters, and thereby promotes mono-ubiqutination of H2B. We first show that up-regulation of Fbxl19 induces the level of global H2Bub1, while down-regulation of Fbxl19 reduces the level of H2Bub1 in mouse ES cells. Our genome-wide target mapping unveils the preferential occupancy of Fbxl19 on CpG island-containing promoters, and we further show that the binding of Fbxl19 is essential for the recruitment of Rnf20 to its target genes and subsequent H2Bub1. Altogether, our results demonstrate that Fbxl19 plays critical roles in the H2Bub1 pathway by recruiting Rnf20 to CGI target genes specifically and selectively.
Project description:Rnf20 catalyzes lysine 120 mono-ubiquitination of histone H2B (H2Bub1) that has been previously invloved in normal differentiation of embryonic stem (ES) and adult stem cells. However,the mechanims underlying by which Rnf20 is recruited to its target chromosomal loci to generate H2Bub1 is still elusive. Here, we reveal that Fbxl19, a CxxC domain-containing protein, physically interacts with Rnf20, guides it preferentially to CpG island-containing target promoters, and thereby promotes mono-ubiqutination of H2B. We first show that up-regulation of Fbxl19 induces the level of global H2Bub1, while down-regulation of Fbxl19 reduces the level of H2Bub1 in mouse ES cells. Our genome-wide target mapping unveils the preferential occupancy of Fbxl19 on CpG island-containing promoters, and we further show that the binding of Fbxl19 is essential for the recruitment of Rnf20 to its target genes and subsequent H2Bub1. Altogether, our results demonstrate that Fbxl19 plays critical roles in the H2Bub1 pathway by recruiting Rnf20 to CGI target genes specifically and selectively.
Project description:In the mouse, long-term silencing by CpG island DNA methylation is specifically targeted to germline genes in somatic cells, however the molecular mechanisms of this specificity remain unclear. Here we demonstrate that the transcription factor E2F6, a member of the polycomb repressive complex 1.6 (PRC1.6), is critical to target and initiate epigenetic silencing at germline genes in early embryogenesis. Genome-wide, E2F6 binds preferentially to CpG islands in embryonic cells. E2F6 cooperates with MGA to silence a subgroup of germline genes in mouse embryonic stem cells and in vivo, a function that critically depends on the E2F6 marked box domain. Furthermore, inactivation of E2f6 leads to a failure to deposit CpG island DNA methylation at these genes during implantation. Finally, we show that E2F6 is required to initiate epigenetic silencing in early embryonic cells but becomes dispensable for the maintenance in differentiated cells. Our findings elucidate the mechanisms of epigenetic targeting of germline genes and provide a paradigm for how transient repression signals by DNA-binding factors in early embryonic cells are translated into long term epigenetic silencing during mammalian development.