Small molecule screen identifies non-catalytic USP3 chemical handle

Zinc-finger ubiquitin binding domains (ZnF-UBDs) are non-catalytic domains mostly found in deubiquitylases (DUBs). They represent an underexplored opportunity for the development of deubiquitylase-targeting chimeras (DUBTACs) to pharmacologically induce the deubiquitination of target proteins. We have previously shown that ZnF-UBDs are ligandable domains. Here, a focused small molecule library screen against a panel of eleven ZnF-UBDs led to the identification of 59, a ligand engaging the ZnF-UBD of USP3 with a KD of 14 {micro}M. The compound binds the expected C-terminal ubiquitin binding pocket of USP3 as shown by hydrogen-deuterium exchange mass spectrometry experiments and does not inhibit the cleavage of K48-linked di-ubiquitin by USP3. As such this compound could serve as a chemical starting point to develop bifunctional DUBTACs recruiting USP3 for targeted deubiquitination. Table of contents graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=93 SRC="FIGDIR/small/530657v3_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@d4e702org.highwire.dtl.DTLVardef@18a506dorg.highwire.dtl.DTLVardef@1a64ef4org.highwire.dtl.DTLVardef@1898461_HPS_FORMAT_FIGEXP M_FIG C_FIG