Fubylation as a Druggable Ubiquitin-Like Conjugation System Controlling Hippo Pathway Activity
The functionally and evolutionarily conserved Hippo-YAP signaling pathway plays a critical role in regulating cellular proliferation, organ size control, and regeneration. Accordingly, activators of YAP-driven transcription hold therapeutic promise for treating disease states driven by insufficient proliferative repair, yet only a handful of pharmacological mechanisms exist for augmenting YAP activity. Here we report the discovery of sCMF231, a small molecule activator of YAP discovered from high throughput screening that acts by targeting the poorly characterized ubiquitin-like protein FUBI. Using canonical ubiquitin conjugation machinery--UBA1, UBE2C, and APC/C--FUBI covalently modifies the Hippo pathway protein Annexin A2, reinforcing its YAP suppressive role at the plasma membrane. Binding of sCMF231 to FUBI discourages its conjugation to Annexin A2, resulting in the membrane delocalization of Annexin A2 and a liberated, transcriptionally active form of YAP. This work provides the first definitive evidence of covalent modification of proteins by FUBI, a post-translational modification termed fubylation, and defines how fubylation regulates the activity of a central growth pathway.