SUMO ylation

Abstract SUMOs are Small Ubiquitin ‐like MOdifier proteins that are covalently attached to hundreds of known target proteins to regulate their function. SUMOylation is the process of conjugating SUMOs to target proteins via E1 , E2 and E3 enzymes and occurs mostly at specific SUMOylation consensus sites in targets. SUMOylation is a reversible process; SUMO‐specific proteases remove SUMOs from target proteins. It has been established that reversible protein SUMOylation is critical for eukaryotic life. A wide variety of cellular processes are regulated by SUMOylation including deoxyribonucleic acid (DNA) metabolism, transport, ribosome biogenesis and translation. Proteins can also associate with SUMO noncovalently via SUMO interaction motifs (SIMs). This affects target protein function and can also affect the subcellular localization of target proteins. Similar to ubiquitin , SUMOs can form polymers via internal SUMOylation sites. Crosstalk between SUMOylation and other posttranslational modifications such as phosphorylation, acetylation and ubiquitination is required for appropriate control of target protein activity. Key concepts: SUMOs are Small Ubiquitin‐like MOdifiers that are covalently attached to lysines in target proteins. SUMOylation, the process of SUMO conjugation to a target protein, frequently occurs on a lysine situated in a SUMOylation consensus site. Conjugated SUMOs can be removed from target proteins by SUMO‐specific proteases. Vertebrates express three different SUMO isoforms, SUMO‐1, SUMO‐2 and SUMO‐3, encoded by three different genes. SUMOs can form polymers via internal SUMOylation sites in SUMO‐2 and SUMO‐3. Several proteins can bind noncovalently to SUMOs via SUMO interaction motifs (SIMs). A finely balanced SUMOylation/deSUMOylation system is required for eukaryotic life. Crosstalk between SUMOylation and other posttranslational modifications like acetylation, phosphorylation and ubiquitination, is important for full control of target protein activity.