Reorganization of PBAF/cBAF remodelers on H3.3 chromatin regulates BMAL1 activity in the absence of circadian negative feedback
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ABSTRACT:
PROVIDER: PRJNA1197484 | ENA |
REPOSITORIES: ENA
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Project description:Circadian rhythms in gene expression are coincident with 24hr dynamics in the recruitment of the core-clock transcription factor heterodimer CLOCK-BMAL1 to chromatin. In the liver, circadian chromatin is characterized by rhythmic histone modifications and the deposition of histone variant H2A.Z. However, other histone variants and the remodelers that work in conjunction with CLOCK-BMAL1 on variant chromatin remain poorly understood. Here, we reveal that H3.3 variant histone deposition peaks during the daytime in liver chromatin and that CLOCK-BMAL1 is recruited to H3.3 nucleosomes. Moreover, H3.3:CLOCK-BMAL1 associates with PBAF and BRG1/cBAF complexes - members of the SWI/SNF remodeler family - only during the active phase of the circadian cycle. In clock-disrupted Per1-/-; Per2-/- livers, we observe a depletion in ARID2, the central cog in the molecular assembly of the PBAF complex, accompanied by an increase in H3.3 incorporation. Remarkably, a disassembly of PBAF complex and the concurrent reduction in BRG1 triggers a remodeler reorganization in Per knockout livers, where BRM/cBAF now targets BMAL1 at readily-accessible genomic sites. An abundance of fragile acetylated H3.3 nucleosomes and a remodeler reorganization provide a mechanistic basis for BMAL1 activity in the absence of PER-mediated negative feedback.
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Project description:Circadian rhythms in gene expression are coincident with 24hr dynamics in the recruitment of the core-clock transcription factor heterodimer CLOCK-BMAL1 to chromatin. In the liver, circadian chromatin is characterized by rhythmic histone modifications and the deposition of histone variant H2A.Z. However, other histone variants and the remodelers that work in conjunction with CLOCK-BMAL1 on variant chromatin remain poorly understood. Here, we reveal that H3.3 variant histone deposition peaks during the daytime in liver chromatin and that CLOCK-BMAL1 is recruited to H3.3 nucleosomes. Moreover, H3.3:CLOCK-BMAL1 associates with PBAF and BRG1/cBAF complexes - members of the SWI/SNF remodeler family - only during the active phase of the circadian cycle. In clock-disrupted Per1-/-; Per2-/- livers, we observe a depletion in ARID2, the central cog in the molecular assembly of the PBAF complex, accompanied by an increase in H3.3 incorporation. Remarkably, a disassembly of PBAF complex and the concurrent reduction in BRG1 triggers a remodeler reorganization in Per knockout livers, where BRM/cBAF now targets BMAL1 at readily-accessible genomic sites. An abundance of fragile acetylated H3.3 nucleosomes and a remodeler reorganization provide a mechanistic basis for BMAL1 activity in the absence of PER-mediated negative feedback.
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Project description:The mammalian SWI/SNF (mSWI/SNF) family of chromatin remodelers govern cell type-specific chromatin accessibility and gene expression and assemble as three distinct complexes: canonical BAF (cBAF), Polybromo-associated BAF (PBAF), and non-canonical BAF (ncBAF). ARID1A and ARID1B are paralog subunits that specifically nucleate the assembly of cBAF complexes and are frequently dual deleted in highly aggressive differentiated endometrial carcinomas (DECs). Here, in cellular models and primary human tumors, we find that ARID1A/B-mediated cBAF loss results in increased ncBAF and PBAF biochemical abundance and function genome-wide to maintain the DEC oncogenic signature. Further, treatment of ARID1A/1B-mutant cell lines and PDX models in vivo with a clinical-grade SMARCA4/2 ATPase inhibitor, FHD-286, markedly attenuates cell proliferation and tumor growth, and synergizes with carboplatin-based chemotherapy. Taken together, these findings reveal the oncogenic contributions of shifted of mSWI/SNF family complex abundance and chromatin-level gene regulatory functions and suggest therapeutic utility of mSWI/SNF complex small molecule inhibitors in dedifferentiated endometrial carcinoma and other cBAF-disrupted cancer types.
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Project description:Multimeric SWI/SNF chromatin remodelers assemble in distinct conformations, with individual functions difficult to dissect. Importantly, mutations in specific SWI/SNF genes are enriched in distinct cancers, as the PBAF-specific component ARID2 in melanoma. Through comprehensive epigenomic profiling of SWI/SNF complexes and their associated chromatin states in melanoma and melanocytes, we found that a subset of PBAF-exclusive regions unexpectedly coexists with PRC2 and repressed chromatin. Time-resolved approaches revealed that PBAF regions are generally less sensitive to ATPase-mediated remodeling compared to BAF sites. Notably, PBAF/PRC2-bound loci are enriched for REST, a transcription factor that represses neuronal genes. In turn, absence of ARID2 and consequent PBAF loss hinders REST ability to bind and inactivate its targets, leading to upregulation of neuronal and synaptic transcripts, a gene signature also associated with ARID2 mutations in melanoma patients. In sum, we demonstrate a unique role for PBAF in generating accessibility for a silencing transcription factor at repressed chromatin.
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Project description:Multimeric SWI/SNF chromatin remodelers assemble in distinct conformations, with individual functions difficult to dissect. Importantly, mutations in specific SWI/SNF genes are enriched in distinct cancers, as the PBAF-specific component ARID2 in melanoma. Through comprehensive epigenomic profiling of SWI/SNF complexes and their associated chromatin states in melanoma and melanocytes, we found that a subset of PBAF-exclusive regions unexpectedly coexists with PRC2 and repressed chromatin. Time-resolved approaches revealed that PBAF regions are generally less sensitive to ATPase-mediated remodeling compared to BAF sites. Notably, PBAF/PRC2-bound loci are enriched for REST, a transcription factor that represses neuronal genes. In turn, absence of ARID2 and consequent PBAF loss hinders REST ability to bind and inactivate its targets, leading to upregulation of neuronal and synaptic transcripts, a gene signature also associated with ARID2 mutations in melanoma patients. In sum, we demonstrate a unique role for PBAF in generating accessibility for a silencing transcription factor at repressed chromatin.
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Project description:Multimeric SWI/SNF chromatin remodelers assemble in distinct conformations, with individual functions difficult to dissect. Importantly, mutations in specific SWI/SNF genes are enriched in distinct cancers, as the PBAF-specific component ARID2 in melanoma. Through comprehensive epigenomic profiling of SWI/SNF complexes and their associated chromatin states in melanoma and melanocytes, we found that a subset of PBAF-exclusive regions unexpectedly coexists with PRC2 and repressed chromatin. Time-resolved approaches revealed that PBAF regions are generally less sensitive to ATPase-mediated remodeling compared to BAF sites. Notably, PBAF/PRC2-bound loci are enriched for REST, a transcription factor that represses neuronal genes. In turn, absence of ARID2 and consequent PBAF loss hinders REST ability to bind and inactivate its targets, leading to upregulation of neuronal and synaptic transcripts, a gene signature also associated with ARID2 mutations in melanoma patients. In sum, we demonstrate a unique role for PBAF in generating accessibility for a silencing transcription factor at repressed chromatin.
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