The ubiquitin system regulates essential cellular processes in eukaryotes. Ubiquitin is
ligated to substrate proteins as monomers or chains and the topology of ubiquitin
modifications regulates substrate interactions with specific proteins. Thus ubiquitination
directs a variety of substrate fates including proteasomal degradation 1. Deubiquitinase
enzymes cleave ubiquitin from substrates and are implicated in disease 2; for example,
ubiquitin-specific protease-7 (USP7) regulates stability of the p53 tumour suppressor and
other proteins critical for tumour cell survival 3. However, developing selective
deubiquitinase inhibitors has been challenging 4 and no co-crystal structures have been
solved with small-molecule inhibitors. Here, using nuclear magnetic resonance-based
screening and structure-based design, we describe the development of selective USP7