sumi1

Sumi1, commonly referred to as SUMO1, is a small ubiquitin-like modifier protein that participates in sumoylation, a reversible post-translational modification of target proteins. SUMO1 belongs to the SUMO family of proteins that regulate diverse cellular processes by covalently attaching to lysine residues on substrates.

SUMO1 is produced as a precursor that is matured by SUMO proteases to expose a C-terminal di-glycine motif required for conjugation. The conjugation process uses an E1 activating enzyme (SAE1/SAE2) and the E2 conjugating enzyme Ubc9, with E3 ligases such as members of the PIAS family or RanBP2 guiding substrate specificity. SUMO1 can be deconjugated by SENP proteases, enabling dynamic cycles of attachment and removal.

Functionally, sumoylation modulates a range of properties including protein stability, interactions, subcellular localization, transcriptional regulation, and the DNA damage response. SUMO1 primarily localizes to the nucleus and is enriched in nuclear bodies under certain conditions, though it also appears in the cytoplasm. Many substrates have been identified, including transcription factors, PML, and RanGAP1, illustrating the broad impact of SUMO1 on cellular networks. SUMO1 sumoylation often contrasts with SUMO2/3 in its ability to form poly-SUMO chains, which influences signaling outcomes.

In humans, SUMO1 is encoded by the SUMO1 gene, and orthologs are found across eukaryotes, highlighting evolutionary conservation. Abnormal sumoylation patterns have been linked to various diseases, including cancer and neurodegenerative disorders, and to altered antiviral responses.