centriole disengagement Centriole disengagement involves the disorientation and physi- cal separation of mother and daughter centrioles at the end of mitosis. Disengagement is an important licensing step for the next round of centrosome replication, preventing reduplication within one cell cycle.' Engagement is thought to be a critical block to reduplication inherent to centrioles. Consistent with this, physical removal of the daughter centriole by laser ablation induces reduplication of the daughter on the mother centriole
The mechanism of centriole disengagement is similar to that of sister chromatid separation at anaphase. Sister chromatids are held together by the ring cohesin complex, which consists of the 4 units Scci, Smci, Smc3, and SAI/SA2; dissociation of this complex by separase mediated cleavage of sccl allows segregation of sister chromatids. The cohesin complex a Localizes to the junction of engaged centrioles and is cleaved there by separase mediated Sccl proteolysis separase is acti vated when its inhibitor securin is targeted for degradation by the E3 ligase anaphase promoting complex/cyclosome(APC/C) -Cbc20 and thus contributes to centriole disengagement. The serine/threonine protein kinase polo like kinase l(Plki) functions in cooperation with parase to trigger centriole