Deciphering the regulatory mechanisms and biological implications of ARID1A missense mutations in cancer.

ARID1A is a key component of the switch/sucrose non-fermentable (SWI/SNF) chromatin remodeling complex and functions as a critical tumor suppressor in various cancers. In this study, we find that tumor cells with hotspot missense mutations in ARID1A (AT-rich interactive domain-containing protein 1A) exhibit a malignant phenotype. Mechanistically, these mutations facilitate the translocation of ARID1A mutant proteins to the cytoplasm by the nucleocytoplasmic shuttler XPO1 (exportin 1). Subsequently, the E3 ubiquitin ligase STUB1 ubiquitinates the ARID1A mutant protein, marking it for degradation. Knocking down STUB1 or inhibiting XPO1 stabilizes the ARID1A mutant protein, retaining it in the nucleus, which restores the assembly of the cBAF complex, the chromatin remodeling function, and the normal expression of genes related to the MAPK and anti-apoptotic pathways, thereby decreasing the tumor burden. Our research shows that nuclear-localized mutated ARID1A proteins retain tumor-suppressive function. We identify promising strategies to treat cancers harboring missense mutations in the BAF complex.