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.
Expressed predominantly in liver.
Belongs to the ubiquitin family. SUMO subfamily. Contains 1 ubiquitin-like domain.
Polymeric chains can be formed through Lys-11 cross-linking. Cleavage of precursor form by SENP1, SENP2 or SENP5 is necessary for function.