U2AF1 mutations rescue deleterious exon skipping induced by KRAS mutations [RNA-Seq]

The mechanisms by which mutations of the splicing factor gene U2AF1 contribute to lung adenocarcinoma pathogenesis are not well understood. Here, we used prime editing to modify the endogenous U2AF1 gene in lung adenocarcinoma cells and assessed the resulting impact on alternative splicing. One specific KRAS mutation, G12S, leads to skipping of KRAS exon 2 and generation of a non-functional KRAS transcript. However, expression of the U2AF1 S34F mutant reverts this exon skipping and restores KRAS function, leading to an enrichment of U2AF1 S34F mutations in KRAS G12S-mutant lung adenocarcinomas. A comprehensive analysis of splicing factor/oncogene mutation co-occurrence in cancer genomes also revealed significant co-enrichment of KRAS Q61R and U2AF1 I24T mutations. Experimentally, KRAS Q61R mutation leads to KRAS exon 3 skipping, which in turn can be rescued by the expression of U2AF1 I24T. Our findings provide evidence that splicing factor mutations can rescue splicing defects caused by oncogenic mutations in a dynamic process of cascading selection.