To evaluate the applicability and selectivity of the assay, we expressed, purified, and tested members of three other DUB families and compared these to USP2: UCHL3 as a member of the ubiquitin C-terminal hydrolase family, JOSD2 as a member of the Machado-Joseph domain-containing proteases, and OTUB1 as a member of the ovarian tumor protease family were selected (Figs. 2 and S3). The gene discussed is OTUB1; the disease is ovarian neoplasm.