E2 ubiquitin-like--protein ligase mediating SUMO/Smt3 attachment to septins and PCNA. Seems to be involved in degradation of S- (CLB5) and M-phase cyclins (CLB2). Protein modification; protein sumoylation. Interacts with SIZ1. Present with 2600 molecules/cell in log phase SD medium. Belongs to the ubiquitin-conjugating enzyme family.