Project description:The Polycomb Repressive Complex 2 (PRC2) and its trimethylation of histone H3 at lysine 27 (H3K27me3) control gene silencing, genome organization, cell-fate determination, as well as normal and pathological development. To date, functional transduction of H3K27me3 is believed to be achieved through the H3K27me3-‘recognizing’ chromodomain harbored within the chromobox (CBX) subunit of Polycomb Repressive Complex 1 (PRC1), which mediates gene silencing partly through H2A monoubiquitination. Here, we report a novel H3K27me3-readout mechanism in mammal, which utilizes an evolutionarily conserved Bromo-adjacent homology (BAH) domain of BAHCC1 (BAH domain and Coiled-Coil Containing 1) for silencing polycomb gene targets. Biochemical, structural and chromatin-immunoprecipitation followed by sequencing (ChIP-seq) analyses revealed that the BAH domain of BAHCC1 specifically engage H3K27me3 through a hydrophobic trimethyl-lysine-binding cage and multiple intermolecular interactions to its flanking residues, mediating co-localization of BAHCC1 with H3K27me3-marked genomic regions in cells. Additionally, we find that BAHCC1 is overexpressed in several human leukemia subtypes including T-cell acute lymphoblastic leukemia (T-ALL), and interacts with transcriptional repressors SAP30-binding protein (SAP30BP) and histone deacetylase 1 (HDAC1). BAHCC1 loss, or disrupting the BAH-mediated interaction of BAHCC1 with H3K27me3 via structure-based mutagenesis, causes chromatin remodeling at the H3K27me3-targeted loci and reactivates polycomb-related gene-silencing programs intimately associated with tumor suppression and cell differentiation, which leads to significantly suppressed T-ALL tumor growth in vitro and in vivo.
Project description:T cell development is accompanied by epigenetic changes that ensure the silencing of stem cell-related, and the activation of lymphocyte-specific programs. How transcription factors influence these changes remains unclear. We show that the Ikaros transcription factor interacts with the Polycomb Repressive Complex 2 (PRC2) in CD4-CD8- thymocytes, and allows its binding to >200 developmentally-regulated genes, many of which are expressed in hematopoietic stem cells. Loss of Ikaros in CD4-CD8- cells leads to diminished histone H3 Lys27 (H3K27) trimethylation and ectopic expression of these genes. Ikaros binding triggers PRC2 recruitment and H3K27 trimethylation. Furthermore, Ikaros interacts with PRC2 independently of the Nucleosome Remodeling and Deacetylation complex. Our results identify Ikaros as a fundamental regulator of PRC2 function in developing T cells.
Project description:T cell development is accompanied by epigenetic changes that ensure the silencing of stem cell-related, and the activation of lymphocyte-specific programs. How transcription factors influence these changes remains unclear. We show that the Ikaros transcription factor interacts with the Polycomb Repressive Complex 2 (PRC2) in CD4-CD8- thymocytes, and allows its binding to >200 developmentally-regulated genes, many of which are expressed in hematopoietic stem cells. Loss of Ikaros in CD4-CD8- cells leads to diminished histone H3 Lys27 (H3K27) trimethylation and ectopic expression of these genes. Ikaros binding triggers PRC2 recruitment and H3K27 trimethylation. Furthermore, Ikaros interacts with PRC2 independently of the Nucleosome Remodeling and Deacetylation complex. Our results identify Ikaros as a fundamental regulator of PRC2 function in developing T cells. Genome-wide comparison of different histone modifications, Ikaros, Suz12 and NuRD binding in different stages of T cell development in WT and Ikaros mutant mice. Profiling of H3K27me3 in DN1, DN2, DN3, DN4 and DP thymocytes and hematopoietic stem and progenitor cells (LSK cells) of WT and Ikaros mutant mice. Profiling of H3K4me3 and H3ac in WT and Ikaros mutant DP thymocytes. Global analysis of Ikaros binding in WT DN3, DN4 and DP cells, Suz12 binding in WT and Ikaros mutant DN3 cells, and Mta2 and Mi2beta binding in WT DN3 cells. Genome-wide profiling of Ikaros binding and H3K27me3 upon Ikaros activation in Ikaros-deficient leukemic T cells.
Project description:CpG island elements are associated with most mammalian gene promoters, yet how they contribute to gene regulation remains poorly understood. Recently it has become clear that a subset of CpG islands in embryonic stem cells can act as polycomb response elements and are recognized by the polycomb silencing systems to regulate the expression of genes involved in pluripotency and early developmental transcription programs. How CpG islands function mechanistically as nucleation sites for polycomb repressive complexes remains unknown. Here we discover that the KDM2B protein, by virtue of its ZF-CxxC DNA binding domain, specifically recognizes non-methylated DNA in CpG islands elements genome-wide. Through a physical interaction with the polycomb repressive complex 1 (PRC1), KDM2B targets PRC1 to CpG islands where it contributes to H2AK119ub1 and gene repression at a subset of polycomb targets. Unexpectedly, we also find that CpG islands are occupied by low levels of PRC1 throughout the genome, suggesting that the KDM2B-PRC1 complex may sample CpG island associated genes for susceptibility to polycomb mediated silencing. These observations demonstrate an unexpected and direct link between recognition of CpG islands by KDM2B and targeting of the polycomb repressive system. This provides the basis for a new model describing the functionality of CpG islands as mammalian PREs. ChIP-Seq to compare KDM2A vs. KDM2B genome-wide binding profiles and to understand the contribution of KDM2B to RING1B nucleation. Binding of Kdm2a and Kdm2b to the genome was examined in wildtype mESC, and Kdm2b and Ring1b in mESC where Kdm2b has been stably knocked down by shRNA.
Project description:This SuperSeries is composed of the following subset Series: GSE33653: Direct Recruitment of Polycomb Repressive Complex 1 (PRC1) to Chromatin by Core Binding Transcription Factors (ChIP-Seq) GSE33659: Direct Recruitment of Polycomb Repressive Complex 1 (PRC1) to Chromatin by Core Binding Transcription Factors (microarray) Refer to individual Series
Project description:This SuperSeries is composed of the following subset Series: GSE33546: Polycomb repressive complex 2-dependent and M-bM-^@M-^Sindependent functions of Jarid2 in transcriptional regulation in Drosophila [ChIP-Seq] GSE36038: Polycomb repressive complex 2-dependent and M-bM-^@M-^Sindependent functions of Jarid2 in transcriptional regulation in Drosophila [Affymetrix] Refer to individual Series