Dynamic Plk1 recruitment to the inner centromere

Mitosis is carefully orchestrated by reversible phosphorylation events. Polo-like kinase 1 (Plk1) regulates multiple functions across the kinetochore during mitotic progression. Recently, Bub1 (outer kinetochore) and CENP-U (inner kinetochore) were described as two major sites of Plk1 recruitment to the kinetochore. Here, we report an additional dynamic site of Plk1 recruitment to the inner centromere. Inner centromere docking occurs during late prometaphase and metaphase, exhibiting transient residency at multiple chromosomes. Chromosomes with inner centromere-localized Plk1 have end-on attached microtubules, diminished Spindle Assembly Checkpoint (SAC) components, and low Shugoshin 1 (Sgo1) levels at the inner centromere. Mechanistically, recruitment is driven by Cdk1 activity and requires Plk1s Polo-Box Domain (PBD). Moreover, inhibition of Bub1 or Protein Phosphatase 2A (PP2A) increases Plk1 recruitment and residency at the inner centromere. Collectively, our data identify a novel pathway for Plk1 recruitment to the inner centromere that is dynamically regulated by counteracting activities of Cdk1 and Bub1/PP2A.