Specificity of small molecule inhibitors for deubiquitinating enzymes in living cells assessed by activity-based proteomics

Small molecular compounds (PR-619 and P22077) was assessed for their abilities to inhibit DUB function in crude extracts and in cells. Activity-based profiling combined with quantitative mass spectrometry revealed the inhibitory capacity of a broad range of DUBs by the PR-619, whereas P22077 showed specificity towards subsets of DUBs including USP7 in cells. Our results demonstrate the usefulness of activity-based quantitative proteomics to monitor inhibition of endogenous DUBs in vivo.