Phosphorylation-dependent activity of the deubiquitinase DUBA

Protease phosphorylation has been reported to affect many signaling pathways connected to proteolytic activity, but the underlying mechanisms have not been clearly elucidated. Structural and biochemical analyses of the deubiquitinase DUBA reveal that phosphorylation is necessary for productive ubiquitin substrate recognition and for enzyme activity. Addition and removal of ubiquitin or ubiquitin chains to and from proteins is a tightly regulated process that contributes to cellular signaling and protein stability. Here we show that phosphorylation of the human deubiquitinase DUBA (OTUD5) at a single residue, Ser177, is both necessary and sufficient to activate the enzyme. The crystal structure of the ubiquitin aldehyde adduct of active DUBA reveals a marked cooperation between phosphorylation and substrate binding. An intricate web of interactions involving the phosphate and the C-terminal tail of ubiquitin cause DUBA to fold around its substrate, revealing why phosphorylation is essential for deubiquitinase activity. Phosphoactivation of DUBA represents an unprecedented mode of protease regulation and a clear link between two major cellular signal transduction systems: phosphorylation and ubiquitin modification.