Harnessing the Deubiquitinase USP1 for Targeted Protein Stabilization.

Deubiquitinase-targeting chimera (DUBTAC) has emerged as a promising technology for targeted protein stabilization (TPS) by harnessing deubiquitinases (DUBs) to remove polyubiquitin chains from target proteins. Despite the presence of over 100 human DUBs, only OTUB1 and USP7 have been utilized in the development of DUBTAC. Hence, there is an urgent need to harness additional DUBs to expand the DUBTAC arsenal. In this work, we demonstrate for the first time that the USP1 deubiquitinase, which is overexpressed in several human cancers, can be leveraged for TPS. We report the development of novel USP1-recruiting DUBTACs by utilizing a noncovalent small-molecule inhibitor of USP1. First, we generated a USP1-based CFTR DUBTAC, MS5310, which effectively stabilized CFTR and is more potent than previously reported CFTR DUBTACs. Next, we developed first-in-class USP1-recruiting UTX DUBTACs, including MS7131, from a small-molecule inhibitor of UTX and JMJD3. Notably, MS7131 effectively stabilized the tumor suppressor UTX in a concentration- and time-dependent manner, while sparing the oncoprotein JMJD3, despite it retaining potent inhibition of JMJD3. Furthermore, UTX stabilization induced by MS7131 was dependent on the engagement of both USP1 and UTX. Consequently, MS7131, but not the parent USP1 inhibitor or UTX inhibitor, effectively reduced histone H3 lysine 27 trimethylation and significantly suppressed the proliferation and clonogenicity of cancer cells. Overall, this study highlights that USP1 can be harnessed for DUBTAC development. Moreover, we developed a valuable chemical tool, MS7131, for the investigation of UTX's distinct functions. This advancement paves the way for leveraging DUBTACs in the treatment of related diseases.