Microtubule Stabilization Triggers the Plus-End Accumulation of Kif18A/kinesin-8.

The precise control of spindle microtubule (MT) dynamics is essential for chromosome capture and alignment. Kif18A/kinesin-8, an essential regulator of kinetochore MT dynamics, accumulates at its plus-ends in metaphase but not prometaphase cells. The underlying mechanism of time-dependent and kinetochore MT-specific plus-end accumulation of Kif18A is unknown. Here, we examined the factors required for the MT plus-end accumulation of Kif18A. In Eg5 inhibitor-treated cells, Kif18A localized along the MTs in the monopolar spindle and rarely accumulated at their plus-ends, indicating that MT-kinetochore association was not sufficient to induce Kif18A accumulation. In contrast, taxol treatment triggered the rapid MT plus-end accumulation of Kif18A regardless of kinetochore association. Furthermore, Aurora B inhibitor-induced stabilization of the plus-ends of kinetochore MTs promoted the plus-end accumulation of Kif18A. In the absence of Kif18A, treatment with taxol but not Eg5 inhibitor causes highly elongated mitotic MTs, suggesting the importance of plus-end accumulation for the MT length-controlling activity of Kif18A. Taken together, we propose that there is a mutual regulation of kinetochore MT plus-end dynamics and Kif18A accumulation, which may contribute to the highly regulated and ordered changes in kinetochore MT dynamics during chromosome congression and oscillation.