Abstract 4546: Ubc9 sumoylation is required for its interaction with CDK6 through SUMO-interacting motif (SIM) and regulates CDK6 sumoylation in glioblastoma

Abstract

Abstract Small ubiquitin-like modifier-1 (SUMO1) is a conserved member of the ubiquitin-related protein family. Recently we have shown that the cell cycle G1 phase cyclin-dependent kinase-6 (CDK6) is modified by SUMO1 in glioblastoma (Bellail et al., Nat Commun. 2014). CDK6 sumoylation stabilizes CDK6 protein and its kinase activity and drives cell cycle progression for the cancer development and progression. SUMO1 is covalently attached to the Lysine 216 of the CDK6 protein through catalytic reactions by an E1 (SUMO-activating enzyme 1/2) and an E2-conjugating enzyme (UBC9). In this study, we further showed that UBC9 is phosphorylated by CDK1 kinase during mitosis and UBC9 phosphorylation increases the interaction of UBC9 with CDK6 and enhances SUMO1-CDK6 conjugation. Knockdown of SUMO1 by small hairpin RNA (shRNA) abolishes the interaction of UBC9 and CDK6 and SUMO1-CDK6 conjugation. UBC9 is conjugated by SUMO1 and recognizes its substrate protein through interaction of SUMO1 and SUMO-Interacting motif (SIMs) on the substrate protein. Indeed, the survey of CDK6 amino acid sequence and structure identified four SIMs on CDK6 protein. Each SIM was mutated to abrogate its binding property. Of the 4 SIMs, the CDK6-SIM4 is responsible for UBC9-CDK6 interaction as demonstrated by the finding that mutation of the first two amino-acids of the SIM sequence abolishes UBC9-CDK6 interaction and SUMO1-CDK6 conjugation. Our data show that UBC9 sumoylation is required for its interaction with CDK6 protein through SIM and thus involved in glioblastoma progression. Citation Format: Anita Bellail, Chunhai Hao. Ubc9 sumoylation is required for its interaction with CDK6 through SUMO-interacting motif (SIM) and regulates CDK6 sumoylation in glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4546.