miRNA-Mediated KHSRP Silencing Rewires Distinct Post-transcriptional Programs during TGF-β-Induced Epithelial-to-Mesenchymal Transition

Epithelial-to-mesenchymal transition (EMT) confers several traits to cancer cells that are required for malignant progression. Here, we report that miR-27b-3p-mediated silencing of the single-strand RNA binding protein KHSRP is required for transforming growth factor β (TGF-β)-induced EMT in mammary gland cells. Sustained KHSRP expression limits TGF-β-dependent induction of EMT factors and cell migration, whereas its knockdown in untreated cells mimics TGF-β-induced EMT. Genome-wide sequencing analyses revealed that KHSRP controls (1) levels of mature miR-192-5p, a microRNA that targets a group of EMT factors, and (2) alternative splicing of a cohort of pre-mRNAs related to cell adhesion and motility including Cd44 and Fgfr2. KHSRP belongs to a ribonucleoprotein complex that includes hnRNPA1, and the two proteins cooperate in promoting epithelial-type exon usage of select pre-mRNAs. Thus, TGF-β-induced KHSRP silencing is central in a pathway leading to gene-expression changes that contribute to the cellular changes linked to EMT.