The association of Plk1 with the Astrin-Kinastrin complex promotes formation and maintenance of a metaphase plate

Errors in mitotic chromosome segregation can lead to DNA damage and aneuploidy, both hallmarks of cancer. To achieve synchronous error-free segregation, mitotic chromosomes must align at the metaphase plate with stable amphitelic attachments to microtubules emanating from opposing spindle poles. The Astrin-Kinastrin/SKAP complex, also containing DYNLL1 and MYCBP, is a spindle and kinetochore protein complex with important roles in bipolar spindle formation, chromosome alignment and microtubule-kinetochore attachment. However, the molecular mechanisms by which Astrin-Kinastrin fulfils these diverse roles are not fully understood. Here we characterise a direct interaction between Astrin and the mitotic kinase Plk1. We identify the Plk1-binding site on Astrin as well as four Plk1 phosphorylation sites on Astrin. Regulation of Astrin-Kinastrin by Plk1 is dispensable for bipolar spindle formation and bulk chromosome congression but promotes stable microtubule-kinetochore attachments and metaphase plate maintenance. It is known that Plk1 activity is required for effective microtubule-kinetochore attachment formation, and we suggest that Astrin phosphorylation by Plk1 contributes to this process.Summary We demonstrate that Plk1 binds to and phosphorylates the N-terminus of Astrin. This interaction promotes recruitment of the Astrin-complex to kinetochores and stabilises microtubule-kinetochore-attachments in situations when mitosis is delayed.Competing Interest StatementThe authors have declared no competing interest.View Full Text