Discovery of Small Molecule Antagonists of the USP5 Zinc Finger Ubiquitin-Binding Domain

USP5 disassembles unanchored polyubiquitin
chains to recycle free monoubiquitin, and is one of the 12 ubiquitin
specific proteases featuring a zinc finger ubiquitin-binding domain
(ZnF-UBD). This distinct structural module has been associated with
substrate positioning or allosteric modulation of catalytic activity,
but its cellular function remains unclear. We screened a chemical
library focused on the ZnF-UBD of USP5, crystallized hits in complex
with the protein, and generated a preliminary structure–activity
relationship, which enables the development of more potent and selective
compounds. This work serves as a framework for the discovery of a
chemical probe to delineate the function of USP5 ZnF-UBD in proteasomal
degradation and other ubiquitin signaling pathways in health and disease.