FIGURE 4.

Interplay between substrate SUMOylation and phosphorylation. A: phosphorylation of some substrates, such as MEF2A and GATA-1, promotes SUMOylation via enhaced recruitment of Ubc9. This is due to the negative charge of the phosphate group interacting with a cognate basic patch on Ubc9. Other substrates, such as Elk-1, are efficiently modified by SUMO due to the presence of a negatively charged region immediately COOH-terminal to the modified lysine, mimicking the effect of phosphorylation, a motif known as an NDSM (negatively charged SUMOylation motif). B: conversely, phosphorylation can also reduce SUMOylation of some substrates. For example, phosphorylation of SATB1 reduces its SUMOylation through blocking binding to the E3, PIAS1.