Ubiquitin carboxyl-terminal hydrolase 12 (USP12) is a specialized cysteine protease with a predicted molecular weight of 43 kDa. USP12 is a member of the peptidase C19 family and USP12/USP46 subfamily, and the human protein shares 98% amino acid sequence identity with its mouse ortholog. Like USP1 and USP46, USP12 lacks appreciable activity in the absence of its co-activator UAF1. Addition of UAF1 increases the in vitro activity of USP12 20-fold or more. WDR20 is often found in complex with both USP12 and UAF1, and the ternary complex is reported to be more active than the USP12/UAF1 complex. Biologically, USP12 has been implicated as a positive regulator of Androgen Receptor (AR) activity via a mechanism that involves down-regulation of Akt activity. As such, it has been proposed that USP12 inhibition could offer a therapeutic target for some forms of prostate cancer. Recombinant USP12 contains a C-terminal 6-His tag. Recombinant UAF1 also contains a C-terminal 6-His tag. The assembled complex contains 25 μg USP12 and 45 μg UAF1, resulting in a 1:1 stoichiometry.