Project description:The PBAF chromatin-remodeling complex is essential for transcription in mammalian cells. We found that PHF10 specific subunit of PBAF lacking C-terminal DPF is expressed in neurons of adult mouse and human brain. We purified the neuronal PBAF of newborn and adult mouse brain using antibodies against PHF10. We found that specific PBAF, designated as dcPBAF, is dominant in mature neurons. dcPBAF is associated with TAF4, TAF5, TAF6, TAF9 subunits of TFIID, does not contain BRD7 and is characterized by the presence of PHF10 isoform lacking N-terminal amino acids and DPF. The dcPBAF binds promoters of actively transcribed housekeeping and neuron specific genes in terminally differentiated neurons of adult mouse. It maintains high transcription level of neuron specific genes in differentiated human neuronal cell. These data indicate some specific features of PBAF mediated chromatin in terminally differentiated mammalian cells.
Project description:The specialised structure of the centromere is critical for effective chromosome segregation, but its repetitive nature makes it vulnerable to rearrangements. Centromere fragility can drive tumorigenesis, but protective mechanisms preventing fragility are still not fully understood. The PBAF chromatin remodelling complex is frequently misregulated in cancer, but its role in cancer is incompletely characterized. Here, we identify PBAF as a protector of centromere and pericentromere structure with profound consequences for genome stability. A conserved feature of isogenic cell lines lacking PBRM1, a subunit of PBAF, is compromised centromere and pericentromere integrity. PBAF is present at these regions, and binding patterns of PBAF and H3K9 methylation change when PBRM1 is absent. PBRM1 loss creates a dependence on the spindle assembly checkpoint, which represents a therapeutic vulnerability. Importantly, we find that even in the absence of any perturbations, PBRM1 loss leads to centromere fragility, thus identifying a new player in centromere protection.
Project description:The specialised structure of the centromere is critical for effective chromosome segregation, but its repetitive nature makes it vulnerable to rearrangements. Centromere fragility can drive tumorigenesis, but protective mechanisms preventing fragility are still not fully understood. The PBAF chromatin remodelling complex is frequently misregulated in cancer, but its role in cancer is incompletely characterized. Here, we identify PBAF as a protector of centromere and pericentromere structure with profound consequences for genome stability. A conserved feature of isogenic cell lines lacking PBRM1, a subunit of PBAF, is compromised centromere and pericentromere integrity. PBAF is present at these regions, and binding patterns of PBAF and H3K9 methylation change when PBRM1 is absent. PBRM1 loss creates a dependence on the spindle assembly checkpoint, which represents a therapeutic vulnerability. Importantly, we find that even in the absence of any perturbations, PBRM1 loss leads to centromere fragility, thus identifying a new player in centromere protection.
Project description:BAF and PBAF are mammalian SWI/SNF family chromatin remodeling complexes that possess multiple histone/DNA-binding subunits and create nucleosome-depleted/free regions for transcription activation. Despite previous structural studies and recent advance of SWI/SNF family complexes, it remains incompletely understood how PBAF-nucleosome complex is organized. Here we determined structure of 13-subunit human PBAF in complex with acetylated nucleosome in ADP-BeF3-bound state. Four PBAF-specific subunits work together with nine BAF/PBAF-shared subunits to generate PBAF-specific modular organization, distinct from that of BAF at various regions. PBAF-nucleosome structure reveals six histone-binding domains and four DNA-binding domains/modules, the majority of which directly bind histone/DNA. This multivalent nucleosome-binding pattern, not observed in previous studies, suggests that PBAF may integrate comprehensive chromatin information to target genomic loci for function. Our study reveals molecular organization of subunits and histone/DNA-binding domains/modules in PBAF-nucleosome complex and provides structural insights into PBAF-mediated nucleosome association complimentary to the recently reported PBAF-nucleosome structure.
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.
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.
Project description:The PBAF complex, a member of SWI/SNF family of chromatin remodelers, plays an essential role in transcriptional regulation. We revealed a disease progression associated elevation of PHF10 subunit of PBAF in clinical samples of melanoma. We demonstrated that in melanoma cell lines, PHF10 interacts with MYC and facilitates the recruitment of PBAF complex to target gene promoters, therefore augmenting MYC transcriptional activation of genes involved in the cell cycle progression. Depletion of either PHF10 or MYC induced G1 accumulation and a senescence-like phenotype. Our data identify PHF10 as a pro-oncogenic mechanism and an essential novel link between chromatin remodeling and MYC-dependent gene transcription.
Project description:The Caenorhabditiselegans somatic gonadal precursors (SGPs) are multipotent progenitors that generate all somatic cells of the adult reproductive system. The two SGPs originate in the mesodermal layer and are born through a division that produces one SGP and one head mesodermal cell (hmc). One hmc terminally differentiates and the other dies by programmed cell death. The PBAF chromatin remodeling complex promotes the multipotent SGP fate. Complete loss of PBAF causes lethality, so we used a combination of Cre/lox recombination and GFP nanobody-directed protein degradation to eliminate PBRM-1, the signature subunit of the PBAF complex, from 83 mesodermal cells, including SGPs, body muscles, and the hmc. We used RNA sequencing to identify genes acting downstream of PBAF in these cells and identified 1955 transcripts that were significantly differentially expressed between pbrm-1(-) and pbrm-1(+) in the mesoderm of L1 larvae.
Project description:ARID2 is an essential subunit of the SWI/SNF PBAF chromatin remodeler and is highly mutate in melanoma. To elucidate the role of ARID2 in melanoma biology and chromatin structure we utilized CRISPR Cas9 methodology to generate isogenic ARID2 WT and KO melanoma clonal cell lines. We further map the genomic localization of several SWI/SNF subunits, open and repressed chromatin markers, and multiple transcription factors to characterize how loss of the PBAF subcomplex alters chromatin accessibility and the melanoma transcription factor network. Finally, we characterized the transcriptional changes produced by PBAF depletion.
Project description:ARID2 is an essential subunit of the SWI/SNF PBAF chromatin remodeler and is highly mutate in melanoma. To elucidate the role of ARID2 in melanoma biology and chromatin structure we utilized CRISPR Cas9 methodology to generate isogenic ARID2 WT and KO melanoma clonal cell lines. We further map the genomic localization of several SWI/SNF subunits, open and repressed chromatin markers, and multiple transcription factors to characterize how loss of the PBAF subcomplex alters chromatin accessibility and the melanoma transcription factor network. Finally, we characterized the transcriptional changes produced by PBAF depletion.