SUMO3 is a ubiquitin-like protein that functions as a post-translational modifier involved in diverse cellular processes including nuclear transport, DNA replication and repair, mitosis, and signal transduction 1. Unlike ubiquitin, SUMO3 does not mark proteins for degradation and may antagonize ubiquitin-mediated protein degradation 1. SUMO3 conjugation requires sequential activation by the E1 complex SAE1-SAE2, transfer via E2 enzyme UBE2I, and promotion by E3 ligases such as TRIM28 and PIAS4. Functionally, SUMO3 modification protects target proteins from degradation by inhibiting ubiquitination. For example, TRIM28-mediated SUMO3 conjugation stabilizes NLRP3, facilitating inflammasome activation 2, and protects TDP-43 against aggregation during oxidative stress 3. SUMO3 also regulates nuclear protein localization, such as promoting NSUN2 nuclear transport in gastric cancer progression 4. Dysregulation of SUMO3-mediated signaling correlates with disease pathogenesis: elevated SUMO3 levels promote colitis in inflammatory bowel disease 5 and enhance ferroptosis following spinal cord injury 6. SUMO3 modification can be reversed by SENP3 deSUMOylase, which regulates ferroptosis and aortic aneurysm development 7. These findings establish SUMO3 as a critical regulator of protein stability and cellular localization with significant therapeutic implications.