Ser/Thr-protein kinase involved in the mitotic exit network (MEN) and required after the metaphase to anaphase cell cycle transition. Required for proper nuclear segregation, mitotic spindle organization, actomyosin ring contraction, primary septum assembly, and normal hyphal morphogenesis. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] In small unbudded G1 cells, localizes to the spindle pole body (SPB). At the G1/S transition, remains associated with the SPB but also starts to accumulate in a linear structure in the nuclei of the cells. During mitosis, a very faint signal along the mother-bud axis is observed, suggesting association with the mitotic spindle during this part of the cell cycle. Finally, localizes to the bud neck at the end of mitosis and cytokinesis. Cell cycle-regulated with a peak during M/G1. Leads to inviable cells. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.