Activation of a small GTP-binding protein by nucleoside diphosphate kinase

Abstract

The centrosome, consisting of a pair of centrioles surrounded by pericentriolar material, directs the formation of bipolar spindles during mitosis. Aberrant centrosome number can promote chromosome instability, which is implicated in tumorigenesis [1, 2]. Thus, centrosome duplication needs to be tightly regulated to occur only once per cell cycle. Separase, a cysteine protease that triggers sister chromatid separation [3], is involved in centriole disengagement, which licenses centrosomes for the next round of duplication [4, 5, 6, 7, 8]. However, at least two questions remain unsolved: what is the substrate relevant to the disengagement, and how does separase, activated at anaphase onset, act on the disengagement that occurs during late mitosis [6, 7, 9, 10]. Here, we show that kendrin, also named pericentrin, is cleaved by activated separase at a consensus site in vivo and in vitro, and this leads to the delayed release of kendrin from the centrosome later in mitosis. Furthermore, we demonstrate that expression of a noncleavable kendrin mutant suppresses centriole disengagement and subsequent centriole duplication. Based on these results, we propose that kendrin is a novel and crucial substrate for separase at the centrosome, protecting the engaged centrioles from premature disengagement and thereby blocking reduplication until the cell passes through mitosis.