Figure 1.

The centrosome cycle with special focus on centriole disengagement. The centrosome cycle starts in early S-phase when the daughter centriole assembles next to the mother centriole. Short daughter centrioles are formed in early S-phase and further elongate in G2. With cytokinesis each daughter cell inherits one centrosome with two joint centrioles. In late mitosis/G1, the two centrioles separate from each other. This process is called ‘centriole disengagement’ (depicted in the enlargement at the right) and is regulated by the protease separase. Cleavage of the cohesin subunit Rad21^Scc1 and kendrin stimulates centriole separation [11,12]. It is unclear whether separase is regulated similarly at the centrosome and centromere. Securin and cyclin B1 are inhibitors of separase. At centrosomes a splice variant of Sgo1, sSgo1, additionally protects premature centriole disengagement. Moreover, Aki1 and astrin have been implicated as centrosome specific inhibitors of separase [13,14].