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: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.
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 composition of chromatin remodeling complexes dictates how these enzymes control transcriptional programs and cellular identity. Here, we investigate the composition of SWI/SNF complexes in embryonic stem cells (ESCs). In contrast to differentiated cells, ESCs have a biased incorporation of certain paralogous SWI/SNF subunits, with low levels of Brm, BAF170 and ARID1B. Upon differentiation, the expression of these subunits increases, resulting in a higher diversity of compositionally distinct SWI/SNF enzymes. We also identify Brd7 as a novel component of the PBAF complex in both ESCs and differentiated cells. Using shRNA-mediated depletion of Brg1, we show that SWI/SNF can function as both a repressor and an activator in pluripotent cells, regulating expression of developmental modifiers and signaling components such as Nodal, ADAMTS1, Bmi-1, CRABP1 and TRH. Knock-down studies of PBAF-specific Brd7 and of a signature subunit within the BAF complex, ARID1A, show that these two sub-complexes affect SWI/SNF target genes differentially, in some cases even antagonistically. This may be due to their different biochemical properties. Finally, we examine the role of SWI/SNF in regulating its target genes during differentiation. We find that SWI/SNF affects recruitment of components of the pre-initiation complex in a promoter-specific manner, to modulate transcription positively or negatively. Taken together, our results provide insight into the function of compositionally diverse SWI/SNF enzymes that underlie their inherent gene-specific mode of action. R1 ESCs were infected in duplicates with shRNA targeting Brg1 or GLUT4 (as a control). Knockdown of Brg1 mRNA affected Brg1 protein levels efficiently. RNA was isolated 67 hours post-infection and analyzed using microarrays.
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 composition of chromatin remodeling complexes dictates how these enzymes control transcriptional programs and cellular identity. Here, we investigate the composition of SWI/SNF complexes in embryonic stem cells (ESCs). In contrast to differentiated cells, ESCs have a biased incorporation of certain paralogous SWI/SNF subunits, with low levels of Brm, BAF170 and ARID1B. Upon differentiation, the expression of these subunits increases, resulting in a higher diversity of compositionally distinct SWI/SNF enzymes. We also identify Brd7 as a novel component of the PBAF complex in both ESCs and differentiated cells. Using shRNA-mediated depletion of Brg1, we show that SWI/SNF can function as both a repressor and an activator in pluripotent cells, regulating expression of developmental modifiers and signaling components such as Nodal, ADAMTS1, Bmi-1, CRABP1 and TRH. Knock-down studies of PBAF-specific Brd7 and of a signature subunit within the BAF complex, ARID1A, show that these two sub-complexes affect SWI/SNF target genes differentially, in some cases even antagonistically. This may be due to their different biochemical properties. Finally, we examine the role of SWI/SNF in regulating its target genes during differentiation. We find that SWI/SNF affects recruitment of components of the pre-initiation complex in a promoter-specific manner, to modulate transcription positively or negatively. Taken together, our results provide insight into the function of compositionally diverse SWI/SNF enzymes that underlie their inherent gene-specific mode of action.