MST1 and neoplasm: This modification promotes MST2 homodimer formation, enhances MST2 kinase activity, and functionally inactivates YAP, thereby inhibiting EMT.378 RNF128 regulates MST protein stability and the expression of Hippo pathway target genes.379 Additionally, Smurf1-mediated polyUb at K285/K282 of MST1/2 destabilizes these kinases, attenuating their tumor-suppressor functions.380 Ubiquitination and deubiquitination critically regulate the Hippo pathway, which governs organ size, tissue homeostasis, and tumor suppression.