PBAF associates with repressed chromatin to enable REST occupancy [ATAC-Seq]

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.