Assay methods for small ubiquitin-like modifier (SUMO)–SUMO-interacting motif (SIM) interactions in vivo and in vitro using a split-luciferase complementation system

SUMOylation is a posttranslational process that attaches a small ubiquitin-like modifier (SUMO) to its target proteins covalently. SUMOylation controls multiple cellular processes through the recognition of SUMO by a SUMO-interacting motif (SIM). In this study, we developed assay systems for detecting noncovalent interactions between SUMO and SIM in cells using split-luciferase complementation. We applied a version of this assay to the detection of in vitro SUMO–SIM interactions using a bacterial expression system. These novel assays enable screening of inhibitors of SUMO-dependent protein–protein interactions, either in vivo or in vitro, in a high-throughput manner.