Transcriptome-wide HITS-CLIP of Quaking (QKI) in TGF-Beta-treated HMLE (Mesenchymal-like) cells

Members of the miR-200 family are critical gatekeepers of the epithelial state, restraining expression of pro-mesenchymal genes that drive epithelial-mesenchymal transition (EMT) and contribute to metastatic cancer progression. Here, we show that miR-200c and another epithelial-enriched miRNA, miR-375, exert widespread control of alternative splicing in cancer cells. This is achieved by their strong suppression of the RNA binding protein Quaking (QKI), which is required to mediate the splicing changes regulated by these miRNAs. During EMT, QKI-5 directly binds to and regulates hundreds of alternative splicing events and exerts pleiotropic effects, such as increasing cell migration and invasion and restraining tumour growth, without appreciably affecting mRNA levels. QKI-5 is both necessary and sufficient to direct EMT alternative splicing changes, and this splicing signature is broadly conserved across many epithelial-derived cancer types. Importantly, several actin cytoskeleton-associated genes are directly targeted both by QKI and miR-200c, revealing coordinated control of alternative splicing and mRNA abundance during EMT. These findings demonstrate the existence of a miR-200/miR-375/QKI axis that impacts cancer-associated epithelial cell plasticity through widespread control of alternative splicing. The purpose of the CLIP experiment was to determine direct targets of QKI. 9 samples: 7 technical replicates of QKI immunoprecipitation, 2 technical replicates of size-matched input samples (controls)