The polo-like kinase family plays a vital role in many cell cycle related events. The family includes mammalian Plkl, Snk (Plk2), and Fnk/Prk (Plk3), Xenopus laevis Plxl,Drosophila polo, fission yeast Plol, and budding yeast Cdc5. These enzymes, in addition to a conserved kinase domain at the N-terminus, have highly conserved sequences called polo-box(s) in the non-catalytic C-terminal domain. Genetic and biochemical experiments with several different organisms have documented that polo-like kinases are involved in many aspects of the cell cycle, such as activation of Cdc2, centrosome assembly and maturation, activation of the anaphase-promoting complex (APC) during the metaphase-anaphase transition, and cytokinesis.