The Arabidopsis SUMO E3 Ligase AtMMS21 Dissociates the E2Fa/DPa Complex in Cell Cycle Regulation

Abstract

Development requires the proper execution and regulation of the cell cycle via precise, conserved mechanisms. Critically, the E2F/DP complex controls the expression of essential genes during cell cycle transitions. Here, we discovered the molecular function of the <i>Arabidopsis thaliana</i> SUMO E3 ligase METHYL METHANESULFONATE SENSITIVITY GENE21 (AtMMS21) in regulating the cell cycle via the E2Fa/DPa pathway. DPa was identified as an AtMMS21-interacting protein and AtMMS21 competes with E2Fa for interaction with DPa. Moreover, DPa is a substrate for SUMOylation mediated by AtMMS21, and this SUMOylation enhances the dissociation of the E2Fa/DPa complex. AtMMS21 also affects the subcellular localization of E2Fa/DPa. The E2Fa/DPa target genes are upregulated in the root of <i>mms21-1</i> and <i>mms21-1</i> mutants showed increased endoreplication. Overexpression of <i>DPa</i> affected the root development of <i>mms21-1</i>, and overexpression of <i>AtMMS21</i> completely recovered the abnormal phenotypes of <i>35S:E2Fa-DPa</i> plants. Our results suggest that AtMMS21 dissociates the E2Fa/DPa complex via competition and SUMOylation in the regulation of plant cell cycle.