A conserved family of small ubiquitin-like modifier proteins which become covalently conjugated to target proteins and modify the properties of these proteins. A SUMO protein is structurally related to ubiquitin (q.v.), and like ubiquitin, binds by its C terminus (q.v.) end to a lysine residue in the target protein. However, protein modification by SUMO does not lead to protein degradation; rather, the modified protein plays a role in regulating a diverse range of functions, such as nucleocytoplasmic transport, gene transcription, chromosome separation, DNA repair, and protein stability. SUMO proteins, like those of the Polycomb group, sometimes also silence genes by inducing the condensation of localized chromosomal regions. The posttranslational modification of a substrate protein by SUMO ligation is called sumoylation. Sumoylation is a reversible, dynamic process, and many enzymes involved in SUMO activation, conjugation, and deconjugation have been identified. SUMO proteins are found in animals, fungi, and plants. In humans there are at least four SUMO isoforms, with distinct functions and subcellular localization. See Polycomb (Pc), ubiquitin-proteasome pathway (UPP).
Subjects: Genetics and Genomics.