Peripheral Golgi protein GRASP65 is a target of mitotic polo-like kinase (Plk) and Cdc2

Cell division is characterized by orchestrated events of chromosome segrega tion, distribution of cellular organelles, and the eventual partitioning an d separation of the two daughter cells. Mitotic kinases. including polo-lik e kinases (Plk), influence multiple events in mitosis. In yeast two-hybrid screens using mammalian Plk C-terminal domain baits, we have identified Gol gi peripheral protein GRASP65 (Golgi reassembly stacking protein of 65 kDa) as a Plk-binding protein. GRASP65 appears to function in the postmitotic r eassembly of Golgi stacks. In this report we demonstrate binding between Pl k and GRASP65 and provide in vitro and in vivo evidence that Plk is a GRASP 65 kinase. Moreover, we show that Cdc2 can also phosphorylate GRASP65. In a ddition, we present data which support the observation that the conserved C terminus of Plk is important for its function. Deletion or frameshift muta tions in the conserved C-terminal domain of Plk greatly diminish its abilit y to phosphorylate GRASP65. These and previous findings suggest that phosph orylation of Golgi components by mitotic kinases may regulate mechanisms of Golgi inheritance during cell division.