Polo Kinase and Separase Regulate the Mitotic Licensing of Centriole Duplication in Human Cells

Abstract

It has been proposed that separase-dependent centriole disengagement at anaphase licenses centrosomes for duplication in the next cell cycle. Here we test whether such a mechanism exists in intact human cells. Loss of separase blocked centriole disengagement during mitotic exit and delayed assembly of new centrioles during the following S phase; however, most engagements were eventually dissolved. We identified Polo-like kinase 1 (Plk1) as a parallel activator of centriole disengagement. Timed inhibition of Plk1 mapped its critical period of action to late G2 or early M phase, i.e., prior to securin destruction and separase activation at anaphase onset. Crucially, when cells exited mitosis after downregulation of both separase and Plk1, centriole disengagement failed completely, and subsequent centriole duplication in interphase was also blocked. Our results indicate that Plk1 and separase act at different times during M phase to license centrosome duplication, reminiscent of their roles in removing cohesin from chromosomes.

Centrobin-mediated Regulation of the Centrosomal Protein 4.1-associated Protein (CPAP) Level Limits Centriole Length during Elongation Stage

“…It has been shown that CPAP is degraded through proteasome targeting, and persistence of CPAP can lead to long, abnormal centrioles (44). Our results show that centrobin-overexpressing cells have abnormal, elongated centrioles (Fig.…”

“…Interestingly, the elongation phase of centriole duplication, which determines centriole length, is completed by the time cells reach mitosis (44). Although CEP120 and SPICE1 are known to promote centriole elongation and interact with CPAP (45,46), they act downstream of CPAP in the centriole duplication process.…”

Let's huddle to prevent a muddle: centrosome declustering as an attractive anticancer strategy

“…[37][38][39][40] Furthermore, knockdown of an isoform of the cohesin-binding protein, SGO1 (shugoshin), causes centriole splitting. 41 Intriguingly, experimental evidence also suggests that cleaved cohesin promotes continued centriole engagement, 34,38,42 perhaps by delivering 'engagement factors' to the centrosome to preserve centriole cohesion until G1. 38 Clearly, more data are awaited to clarify how centrioles remain engaged for the appropriate segment of the cell cycle and subsequently part ways in an exquisitely timed manner.…”

“…43 Nevertheless, Plk1 activity slowly rises from S through G2 and peaks in mitosis. Plk1 not only mediates centriole maturation 42,44,45 but also primes centrioles for disengagement 34 by phosphorylating cohesin and accelerating its cleavage by separase. 46 In addition, Plk1 may regulate centrosomal localization of shugoshin and mediate centriole disengagement by modifying shugoshin's activity in preserving centriole cohesion.…”

“…31,[33][34][35] The cell utilizes separase's protease activity to cleave the tight intercentriolar linker to license duplication, thereby coupling centriole duplication mechanistically to the onset of sister-chromatid separation. 34,36 These data engendered the hypothesis that cohesin forms the tight intercentriolar linker. In support of this idea, all elements of the cohesin complex are found in the centrosome, and cohesin depletion results in centriole disengagement.…”