Recruitment of distinct subcellular complexes by RhoGAP DLC1 in governing avian cranial neural crest specification and epithelial-to-mesenchymal transition

Abstract

Rho GTPase-activating (RhoGAP) proteins are known to regulate cytoplasmic RHO signaling in various cell types. Here, we reveal a new mechanism by which the RhoGAP Deleted in Liver Cancer 1 (DLC1) regulates transcriptional and post-translational machineries of avian cranial neural crest (NC) specifiers (SOX9, FOXD3 and SNAIL2) independent of its RhoGAP activity. We found that the neural plate border specifier PAX7 associates with DLC1 and their interaction is required for PAX7 binding to the enhancers of NC specifiers. Nuclear DLC1 further recruits TCEB1, which is essential for DNA binding of elongating RNA polymerase II to maintain transcription of NC specifiers. In vivo biosensor analysis demonstrates that cytoplasmic DLC1 recruits STRAP to stabilize SNAIL2 protein through inhibition of GSK3beta activity that permits NC epithelial-to-mesenchymal transition (EMT). Importantly, both nuclear and cytoplasmic roles of DLC1 are not mediated by its RhoGAP activity. These findings unravel molecular mechanisms by which DLC1 recruits distinct subcellular complexes in governing NC cell fate determination and EMT onset, suggesting a new perspective on the cellular functions of RhoGAP proteins.