Ubiquitin-like protein which can be covalently attached to target lysines either as a monomer or as a lysine-linked polymer. Does not seem to be involved in protein degradation and may function as an antagonist of ubiquitin in the degradation process. Plays a role in a number 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 can be promoted by an E3 ligase such as PIAS1-4, RANBP2 or CBX4. Covalently attached to a number of proteins. Interacts with USP25 (via ts SIM domain); the interaction sumoylates USP25 and inhibits its ubiquitin hydrolyzing activity. Interacts with SAE2 and UBE2I. Expressed predominantly in liver. Belongs to the ubiquitin family. SUMO subfamily. Note: This description may include information from UniProtKB.
Alt. Names/Synonyms: Small ubiquitin-related modifier 3; SMT3 homolog 1; SMT3 suppressor of mif two 3 homolog 1; SMT3 suppressor of mif two 3 homolog 3 (S. cerevisiae); SMT3A; SMT3H1; SUMO-2; SUMO-3; SUMO3; Ubiquitin-like protein SMT3A