Localization of Kinetochore-Associated XKCMl in PtK2 Cells

Abstract

XKCMl (Xenopus Kinesin Catastrophe Modulator 1) is a newly identified kinesin that was shown to be essential for the establishment and the maintenance of mitotic spindles by affecting the microtubule dynamics in Xenopus extracts (Desai et al., 1999). In this research we examined the localization of kinetochore-associated XKCMl in PtK2 cells via immunofluorescence staining of cells treated with the anti-cancer drugs nocodazole and taxol, which disturb the microtubule dynamics. Upon the addition of taxol, microtubule dynamics were suppressed at the plus-ends, which reduced the tension across kinetochores. Nocodazole, on the other hand, destabilized microtubules, producing a pool of tubulin dimers. This treatment decreased the tension across kinetochores by abolishing the microtubule-kinetochore interaction. The length of XKCMl staining was then measured at kinetochores upon the addition of each drug. In both drug treatments, the tension of kinetochores was decreased or completely lost in some cases, as we had hypothesized. The results of the experiments are in agreement with the idea that microtubule dynamics have a direct effect on XKCMl in mammalian cells during mitosis.