UAF1 forms three distinct deubiquitinating enzyme complexes with USP1,
USP12, and USP46. A, native UAF1, USP1, USP12, and USP46
complexes were purified from HeLa cells and analyzed by immunoblot analysis
using the indicated antibodies. B, alignment of the amino acids
surrounding the catalytic cysteine residue in USP12 and USP46. C,
immunoblot analysis of the USP12 and USP12-C48S complexes using the indicated
antibodies. D, USP12 and USP12-C48S complexes were analyzed for
associated deubiquitinating enzyme activity using ubiquitin-AMC as a
substrate.