Project description:Tri-methylation of histone H3 lysine 27 (H3K27me3) regulates transcriptional repression, cell-fate determination and differentiation. We report that a conserved Bromo-Adjacent Homology (BAH) module harbored within BAHCC1, a previously uncharacterized chromatin regulator, ‘recognizes’ H3K27me3 specifically and enforces silencing of H3K27me3-demarcated genes in mammalian cells. Biochemical, structural and ChIP-seq-based analyses demonstrate that direct ‘readout’ of H3K27me3 by BAHCC1 is achieved through a hydrophobic trimethyl-lysine-binding ‘cage’ formed by the BAH domain, mediating co-localization of BAHCC1 and H3K27me3-marked genes. BAHCC1 is significantly overexpressed in human acute leukemia and biochemically, BAHCC1 interacts with repressors SAP30BP and HDAC. In acute leukemia, depletion of BAHCC1, or disruption of the BAHCC1 BAH-mediated ‘readout’ of H3K27me3, causes de-repression of H3K27me3-targeted genes that are involved in tumor suppression and cell differentiation, leading to the suppressed tumor growth. In mice, introduction of a germ-line mutation at Bahcc1 to disrupt its H3K27me3 engagement causes postnatal lethality, supporting a role of this pathway in development. Collectively, this study unveils a novel H3K27me3-directed transduction pathway in mammal cells that relies on a conserved BAH ‘reader’, deregulation of which contributes to oncogenesis.
Project description:Tri-methylation of histone H3 lysine 27 (H3K27me3) regulates transcriptional repression, cell-fate determination and differentiation. We report that a conserved Bromo-Adjacent Homology (BAH) module harbored within BAHCC1, a previously uncharacterized chromatin regulator, ‘recognizes’ H3K27me3 specifically and enforces silencing of H3K27me3-demarcated genes in mammalian cells. Biochemical, structural and ChIP-seq-based analyses demonstrate that direct ‘readout’ of H3K27me3 by BAHCC1 is achieved through a hydrophobic trimethyl-lysine-binding ‘cage’ formed by the BAH domain, mediating co-localization of BAHCC1 and H3K27me3-marked genes. BAHCC1 is significantly overexpressed in human acute leukemia and biochemically, BAHCC1 interacts with repressors SAP30BP and HDAC. In acute leukemia, depletion of BAHCC1, or disruption of the BAHCC1 BAH-mediated ‘readout’ of H3K27me3, causes de-repression of H3K27me3-targeted genes that are involved in tumor suppression and cell differentiation, leading to the suppressed tumor growth. In mice, introduction of a germ-line mutation at Bahcc1 to disrupt its H3K27me3 engagement causes postnatal lethality, supporting a role of this pathway in development. Collectively, this study unveils a novel H3K27me3-directed transduction pathway in mammal cells that relies on a conserved BAH ‘reader’, deregulation of which contributes to oncogenesis.
Project description:Tri-methylation of histone H3 lysine 27 (H3K27me3) regulates transcriptional repression, cell-fate determination and differentiation. We report that a conserved Bromo-Adjacent Homology (BAH) module harbored within BAHCC1, a previously uncharacterized chromatin regulator, ‘recognizes’ H3K27me3 specifically and enforces silencing of H3K27me3-demarcated genes in mammalian cells. Biochemical, structural and ChIP-seq-based analyses demonstrate that direct ‘readout’ of H3K27me3 by BAHCC1 is achieved through a hydrophobic trimethyl-lysine-binding ‘cage’ formed by the BAH domain, mediating co-localization of BAHCC1 and H3K27me3-marked genes. BAHCC1 is significantly overexpressed in human acute leukemia and biochemically, BAHCC1 interacts with repressors SAP30BP and HDAC. In acute leukemia, depletion of BAHCC1, or disruption of the BAHCC1 BAH-mediated ‘readout’ of H3K27me3, causes de-repression of H3K27me3-targeted genes that are involved in tumor suppression and cell differentiation, leading to the suppressed tumor growth. In mice, introduction of a germ-line mutation at Bahcc1 to disrupt its H3K27me3 engagement causes postnatal lethality, supporting a role of this pathway in development. Collectively, this study unveils a novel H3K27me3-directed transduction pathway in mammal cells that relies on a conserved BAH ‘reader’, deregulation of which contributes to oncogenesis.
Project description:Tri-methylation of histone H3 lysine 27 (H3K27me3) regulates transcriptional repression, cell-fate determination and differentiation. We report that a conserved Bromo-Adjacent Homology (BAH) module harbored within BAHCC1, a previously uncharacterized chromatin regulator, ‘recognizes’ H3K27me3 specifically and enforces silencing of H3K27me3-demarcated genes in mammalian cells. Biochemical, structural and ChIP-seq-based analyses demonstrate that direct ‘readout’ of H3K27me3 by BAHCC1 is achieved through a hydrophobic trimethyl-lysine-binding ‘cage’ formed by the BAH domain, mediating co-localization of BAHCC1 and H3K27me3-marked genes. BAHCC1 is significantly overexpressed in human acute leukemia and biochemically, BAHCC1 interacts with repressors SAP30BP and HDAC. In acute leukemia, depletion of BAHCC1, or disruption of the BAHCC1 BAH-mediated ‘readout’ of H3K27me3, causes de-repression of H3K27me3-targeted genes that are involved in tumor suppression and cell differentiation, leading to the suppressed tumor growth. In mice, introduction of a germ-line mutation at Bahcc1 to disrupt its H3K27me3 engagement causes postnatal lethality, supporting a role of this pathway in development. Collectively, this study unveils a novel H3K27me3-directed transduction pathway in mammal cells that relies on a conserved BAH ‘reader’, deregulation of which contributes to oncogenesis.
Project description:Trimethylation of histone H3 lysine 27 (H3K27me3) regulates gene repression, cell-fate determination and differentiation. We report that a conserved Bromo-Adjacent Homology (BAH) module of BAHCC1 (BAHCC1BAH) ‘recognizes’ H3K27me3 specifically and enforces silencing of H3K27me3-demarcated genes in mammalian cells. Biochemical, structural and ChIP-seq-based analyses demonstrate that direct readout of H3K27me3 by BAHCC1 is achieved through a hydrophobic trimethyl-lysine-binding ‘cage’ formed by BAHCC1BAH, mediating co-localization of BAHCC1 and H3K27me3-marked genes. BAHCC1 is overexpressed in human acute leukemias and interacts with transcriptional co-repressors. In leukemia, depletion of BAHCC1, or disruption of the BAHCC1BAH:H3K27me3 interaction, causes de-repression of H3K27me3-targeted genes that are involved in tumor suppression and cell differentiation, leading to suppression of oncogenesis. In mice, introduction of a germ-line mutation at Bahcc1 to disrupt its H3K27me3 engagement causes partial postnatal lethality, supporting a role in development. This study unveils a novel H3K27me3-directed transduction pathway in mammals that relies on a conserved BAH ‘reader’.
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.