Figure 4

A model illustrating the self-regulated mechanism of Plk1 localization to the interphase and mitotic centromeres. Early in the cell cycle, PBIP1 accumulates at the interphase kinetochores prior to Plk1 localization (S phase). As Plk1 is expressed in G2, Plk1 interacts with PBIP1 and phosphorylates T78 to create a self-docking site for its PBD (G2 phase). This step is critical to promote its own recruitment to the kinetochores. In early mitosis, a surge in the Plk1 activity induces hyperphosphorylation and delocalization of PBIP1 from the mitotic kinetochores in a manner that is not understood at present (early M phase). As the level of PBIP1 at the kinetochore diminishes, Plk1 liberated from the p-T78 PBIP1 tether binds to other kinetochore components or substrates (marked "X") critical for proper M-phase progression (M phase).