Figure 1.

SUMOylation and deSUMOylation are dynamically balanced under physiological conditions. SUMO proteins are proteolytically cleaved by SUMO/ SENP to form mature forms. The matured SUMOs are activated by SAE1/SAE2 in an ATP-dependent manner. E2 UBC9 catalyzes the transesterification to form E2 UBC9 conjugate while the SUMO E3 ligase catalyzes the SUMOylation by transferring SUMOs to the target protein at the specific lysine residues. On the other hand, the SUMOylated proteins undergo deconjugation to dissociate the target protein-SUMO conjugates by SENP. Under physiological conditions, SUMOylation and deSUMOylation are dynamically balanced.