NIMA-related kinase 2 (Nek2), a cell-cycle-regulated protein kinase localized to centrosomes, is complexed to protein phosphatase 1

The cell cycle-regulated protein serine/threonine NIMA-related kinase 2 (Ne k2), which shows a predominant localization at centrosomes, is identified a s a protein which interacts with protein phosphatase 1 (PP1) using the yeas t two-hybrid system. Complex formation between Nek2 and PPI is supported by coprecipitation of the two proteins using transfected expression construct s of Nek2 and the endogenous Nek2/PP1 proteins. The sequence KVHF in the C- terminal region of Nek2, which conforms to the consensus PP1-binding motif, is shown to be essential for the interaction of Nek2 with PP1. Nek2 activi ty increases with autophosphorylation and addition of phosphatase inhibitor s and decreases in the presence of PP1. PP1 is a substrate for Nek2 and pho sphorylation of PP1 gamma(1), on two C-terminal sites reduces its phosphata se activity. The presence of a ternary complex containing centrosomal Nek2- associated protein (C-Nap1), Nek2 and PP1 has also been demonstrated, and C -Nap1 is shown to be a substrate for both Nek2 and PP1 ill vitro and in cel l extracts. The implications of kinase-phosphatase complex formation involv ing Nek2 and PP1 are discussed in terms of the coordination of centrosome s eparation with cell cycle progression.