Alternative polyadenylation is a determinant of oncogenic Ras function.

Alternative polyadenylation of mRNA has important but poorly understood roles in development and cancer. Activating mutations in the Ras oncogene are common drivers of many human cancers. From a screen for enhancers of activated Ras (let-60) in Caenorhabditis elegans, we identified cfim-1, a subunit of the alternative polyadenylation machinery. Ablation of cfim-1 increased penetrance of the multivulva phenotype in let-60/Ras gain-of-function (gf) mutants. Depletion of the human cfim-1 ortholog CFIm25/NUDT21 in cancer cells with KRAS mutations increased their migration and stimulated an epithelial-to-mesenchymal transition. CFIm25-depleted cells and cfim-1 mutants displayed biased placement of poly(A) tails to more proximal sites in many conserved transcripts. Functional analysis of these transcripts identified the multidrug resistance protein mrp-5/ABCC1 as a previously unidentified regulator of C. elegans vulva development and cell migration in human cells through alternative 3'UTR usage. Our observations demonstrate a conserved functional role for alternative polyadenylation in oncogenic Ras function.