Design of high-throughput screening assays and identification of a SUMO1-specific small molecule chemotype targeting the SUMO-interacting motif-binding surface.

Protein-protein interactions are generally challenging to target by small molecules. To address the challenge, we have used a multidisciplinary approach to identify small-molecule disruptors of protein-protein interactions that are mediated by SUMO (small ubiquitin-like modifier) proteins. SUMO modifications have emerged as a target with importance in treating cancer, neurodegenerative disorders, and viral infections. It has been shown that inhibiting SUMO-mediated protein-protein interactions can sensitize cancer cells to chemotherapy and radiation. We have developed highly sensitive assays using time-resolved fluorescence resonance energy transfer (TR-FRET) and fluorescence polarization (FP) that were used for high-throughput screening (HTS) to identify inhibitors for SUMO-dependent protein-protein interactions. Using these assays, we have identified a nonpeptidomimetic small molecule chemotype that binds to SUMO1 but not SUMO2 or 3. NMR chemical shift perturbation studies have shown that the compounds of this chemotype bind to the SUMO1 surface required for protein-protein interaction, despite the high sequence similarity of SUMO1 and SUMO2 and 3 at this surface.