A mechanism for coupling exit from mitosis to partitioning of the nucleus

Exit from mitosis must not occur prior to partitioning of chromosomes betwe en daughter cells. We find that the GTP binding protein Tem1, a regulator o f mitotic exit, is present on the spindle pole body that migrates into the bud during S phase and mitosis. Tem1's exchange factor, Lte1, localizes to the bud. Thus, Tem1 and Lte1 are present in the same cellular compartment ( the bud) only after the nucleus enters the bud during nuclear division. We also find that the presence of Tem1 and Ltel in the bud is required for mit otic exit. Our results suggest that the spatial segregation of Tem1 and Lte l ensures that exit from mitosis only occurs after the genetic material is partitioned between mother and daughter cell.