Spliceosomal disruption of the non-canonical BAF complex in cancer
Ontology highlight
ABSTRACT: SF3B1 is the most commonly mutated RNA splicing factor in cancer, but the mechanisms by which SF3B1 mutations promote malignancy are poorly understood. Here, we integrated pan-cancer RNA sequencing to identify mutant SF3B1-dependent aberrant splicing with a positive enrichment CRISPR screen to prioritize splicing alterations that functionally promote tumorigenesis. We identify that diverse, recurrent SF3B1 mutations converge on repression of BRD9, a core component of the recently described non-canonical BAF (ncBAF) complex. Mutant SF3B1 recognizes an aberrant deep intronic branchpoint within BRD9, thereby inducing inclusion of an endogenous retrovirus-derived poison exon and BRD9 mRNA degradation. BRD9 depletion causes loss of ncBAF at CTCF-bound loci and promotes melanomagenesis. We demonstrate that BRD9 is a potent tumor suppressor in uveal melanoma, such that correcting BRD9 mis-splicing in SF3B1-mutant cell lines and patient-derived melanoma xenografts with antisense oligonucleotides (ASOs) or by directly targeting its poison exon with CRISPR-directed mutagenesis profoundly suppresses tumor growth. Our results implicate disruption of ncBAF in the diverse malignancies characterized by SF3B1 mutations, identify a single aberrant splicing event which functionally contributes to the pathogenesis of SF3B1-mutant cancers, and suggest a mechanism-based therapeutic for these malignancies.
ORGANISM(S): Homo sapiens
PROVIDER: GSE124720 | GEO | 2019/06/19
REPOSITORIES: GEO
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