Abstract
Sumoylation regulates a wide range of cellular processes. However, little is known about the regulation of the SUMO machinery. In this study, we demonstrate that two lysine residues (Lys-153 and Lys-157) in the C-terminal region of the yeast E2-conjugating enzyme Ubc9 are the major and minor autosumoylation sites, respectively. Surprisingly, mutation of Lys-157 (ubc9(K157R)) significantly stimulates the level of Ubc9 autosumoylation at Lys-153. The functional role of Ubc9 autosumoylation is exemplified in our findings that cell cycle-dependent sumoylation of cytoskeletal septin proteins is inversely correlated with the Ubc9 autosumoylation level and that mutation of the Ubc9 autosumoylation sites results in aberrant cell morphology. Our study elucidates a regulatory mechanism that utilizes automodification of the E2 enzyme of the sumoylation machinery to control substrate sumoylation.
Highlights
Signal transduction relies on post-translational modifications, such as acetylation, methylation, phosphorylation, carboxylation, glycosylation, ubiquitination, and sumoylation, to transmit information within and across cells [1]
Modification of Yeast Ubc9 by Smt3—Utilizing an in vitro sumoylation assay, we observed in our previous work that human Ubc9 is sumoylated [25]
We found that K153RUbc9 still maintained a certain level of Ubc9 sumoylation, suggesting that Ubc9 contains at least two lysine residues for isopeptide bond formation with Smt3
Summary
Signal transduction relies on post-translational modifications, such as acetylation, methylation, phosphorylation, carboxylation, glycosylation, ubiquitination, and sumoylation, to transmit information within and across cells [1]. We demonstrate that two lysine residues (Lys-153 and Lys-157) in the C-terminal region of the yeast E2-conjugating enzyme Ubc9 are the major and minor autosumoylation sites, respectively. We mutated Lys-153 of yeast Ubc9 to arginine and confirmed that Lys-153 is the major in vitro SUMO conjugation site.
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