Structure Activity Relationship of USP5 Allosteric Inhibitors

USP5 is a deubiquitinase that has been implicated in a range of diseases, including cancer, but no USP5-targeting chemical probe has been reported to date. Here, we present the progression of a chemical series that occupies the C-terminal ubiquitin-binding site of a poorly characterized zinc-finger ubiquitin binding domain (ZnF-UBD) of USP5 and allosterically inhibits the catalytic activity of the enzyme. Systematic exploration of the structure-activity relationship, complemented with crystallographic characterization of the ZnF-UBD bound to multiple ligands, led to the identification of 64, which binds to the USP5 ZnF-UBD with a KD of 2.8 {micro}M. 64 is selective over the structurally similar ZnF-UBD domain of HDAC6 and inhibits USP5 catalytic activity in vitro with an IC50 of 26 {micro}M. This study provides a chemical and structural framework for the discovery of a chemical probe to delineate USP5 function in cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=86 SRC="FIGDIR/small/444542v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@3fc7bcorg.highwire.dtl.DTLVardef@15233e0org.highwire.dtl.DTLVardef@1cbf34corg.highwire.dtl.DTLVardef@d237d0_HPS_FORMAT_FIGEXP M_FIG Table of Contents Graphic C_FIG