The Deubiquitinase USP36 Regulates Growth and Spermatogenesis Through Catalytic-Dependent and -Independent Mechanisms in Drosophila

Deubiquitinases (DUBs) form a specific class of proteases removing ubiquitin from target proteins. They are involved in the regulation of many cellular processes including cell growth and proliferation. Among them, USP36 is a key regulator of the oncogenic transcription factor c-Myc, preventing its degradation by the proteasome. These two proteins form an evolutionary conserved complex providing the opportunity to investigate USP36 mechanisms of action in vivo in a genetically tractable model such as Drosophila melanogaster. Null mutants of dUsp36 die early during larval development and exhibit severe growth defects. Strikingly, we report here that flies carrying a CRISPR/Cas9-induced catalytic mutation of dUsp36 survive to adulthood with only minor growth defects, yet males are infertile. This finding indicates that dUSP36 deubiquitinating activity is dispensable for cell growth but essential for spermatogenesis. Our results thus reveal that dUSP36 functions through both catalytic-dependent and catalytic-independent mechanisms, highlighting a dual mode of action with implications for the understanding of DUBs mechanism of action.