Small ubiquitin-related modifier 3 (SUMO3)

Ubiquitin-like protein which may be covalently attached to target lysines either as a monomer or as a lysine-linked polymer. Does not appear to be involved in protein degradation and might function as an antagonist of ubiquitin in the degradation process.

Plays a role in several of cellular processes such as nuclear transport, DNA replication and repair, mitosis and signal transduction. Covalent attachment to its substrates requires prior activation by the E1 complex SAE1-SAE2 and linkage to the E2 enzyme UBE2I, and may be promoted by means of an E3 ligase such as PIAS1-4, RANBP2 or CBX4 (PubMed:11451954, PubMed:18538659, PubMed:21965678).