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:The specialized structure of the centromere is critical for effective chromosome segregation, but its repetitive nature and configuration makes it vulnerable to rearrangements. Centromere fragility can drive tumorigenesis, but protective mechanisms preventing fragility are still not fully understood. To identify core functions of the tumor suppressor PBRM1, a subunit of the PBAF remodelling complex, we created a panel of isogenic cell lines. We found that compromised centromere integrity is a general feature of cells lacking PBRM1. This defect creates a dependence on the spindle assembly checkpoint, which can be therapeutically exploited. We map the SMARCA4 subunit of PBAF across centromeric and pericentromeric chromatin and find PBRM1-dependent association with specific sequences. We further find that loss of PBRM1 leads to altered transcription of pericentromere-associated genes and transposable elements. These data identify PBAF as a protector of centromere structure with profound consequences for genome integrity.
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: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:MicroRNAs (miRNAs) are essential regulators involved in multiple biological processes. To achieve their gene repression function, they are loaded in miRNA-specific Argonautes to form the miRNA-induced silencing complex (miRISC). Mammals and C. elegans possess more than one paralog of miRNA-specific Argonautes but the dynamic between them remains unclear. Here, we report the conserved dipeptidyl peptidase DPF-3 as a new interactor of the miRNA-specific Argonautes ALG-1 and ALG-2 in C. elegans. Knockout of dpf-3 increases ALG-2 levels and miRISC formation in alg-1 null animals, thereby compensating for ALG-1 loss and rescuing miRNA-related defects observed. DPF-3 can cleave an ALG-2 N-terminal peptide in vitro but does not appear to rely on this catalytic activity to regulate ALG-2 in vivo. This study uncovers the importance of DPF-3 in the miRNA pathway and provides insights on how multiple miRNA Argonautes contribute to achieve proper miRNA-mediated gene regulation in animals.
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.