MEN, destruction and separation: mechanistic links between mitotic exit and cytokinesis in budding yeast

Cellular events must be executed in a certain sequence during the cell division in order to maintain genome integrity and hence ensure a cell's survival. In M phase, for instance, chromosome segregation always precedes mitotic exit (characterized by mitotic kinase inactivation via cyclin destruction); this is then followed by cytokinesis. How do cells impose this strict order? Recent findings in budding yeast have suggested a mechanism whereby partitioning of chromosomes into the daughter cell is a prerequisite for the activation of mitotic exit network (MEN). So far, however, a regulatory scheme that would temporally link the initiation of cytokinesis to the execution of mitotic exit has not been determined. We propose that the requirement of MEN components for cytokinesis, their translocation to the mother-daughter neck and triggering of this translocation by inactivation of the mitotic kinase may be the three crucial elements that render initiation of cytokinesis dependent on mitotic exit.