Chemoproteomic Screening of Covalent Ligands Reveals UBA5 As a Novel Pancreatic Cancer Target

Chemical genetic screening of small-molecule libraries has been a promising strategy for discovering unique and novel therapeutic,compounds. However, identifying the targets of lead molecules that arise from these screens has remained 4 major bottleneck in uuderstanding the mechanism of action of these compounds. Here, we have coupled the screening of a crysteine reactive fragment-based covalent ligand library with an isotopic tandem orthogonal proteolysis::enabled activity-basect pratein profiling (lsoTOP-ABPP) chemoproteomic platform to rapidly couple the discovery of lead small molecules that impair pancreatic cancer pathogenicity with the identification of druggable hotspots for :potential cancer therapy. Through this coupled approach, we have discovered a covalent ligand DKM 2-93 that impair pancreatic cancer cell survival and in vivo tumor growth through covalently modifying the catalytic cysteine of the ubiquitin-ilike modifier activating enzyme 5 (UBA5), thereby inhibiting its activity as a protein that activates the ubiquitin-like protein UFM1 to UFMylate proteins. We show that is a novel pancreatic cancer therapeutic target and show DKM 2-93 as relatively Selective lead inhibitor of UBA5. Our results underscore the utility of coupling the screening of covalent ligand libraries with isoTOP-ABPP platforms for, Mining the proteome for druggable hotspots for cancer therapy.