Mitotic chromosomes move dynamically along the spindle microtubules using the forces generated by motor proteins including chromokinesin Kid/kinesin-10. Kid generates a polar ejection force and contributes to alignment of the chromosome arms during the prometaphase and metaphase, while during anaphase Kid contributes to chromosome compaction. How Kid is regulated and how this regulation is important for chromosome dynamics remains unclear. Here we address these questions by expressing mutant forms of Kid in Kid-deficient cells. We demonstrate that Cdk1-mediated phosphorylation and dephosphorylation of Thr463 are required to generate and to stop generating the polar ejection force on Kid-binding chromosomes, respectively. In addition to the second microtubule-binding domain activated by Thr463-dephosphorylation, the coiled-coil domain is essential to suspend the polar ejection force, and thereby prevent separated chromosomes from becoming recongressed during anaphase. We propose that phosphorylation of Thr463 switches the mitotic chromosome movement from anti-poleward to poleward by converting the Kid functional mode from polar-ejection-force-ON to -OFF during the metaphase-anaphase transition, and that both the second microtubule-binding domain and the coiled-coil domain are the operation units involved in this switching process.
- Received March 30, 2016.
- Accepted August 17, 2016.
- © 2016. Published by The Company of Biologists Ltd