During anaphase identical sister chromatids separate and move towards opposite poles of the mitotic spindle1,2. In the spindle, kinetochore microtubules3 have their plus ends embedded in the kinetochore and their minus ends at the spindle pole. Two models have been proposed to account for the movement of chromatids during anaphase. In the ‘Pac-Man’ model, kinetochores induce the depolymerization of kinetochore microtubules at their plus ends, which allows chromatids to move towards the pole by ‘chewing up’ microtubule tracks4,5. In the ‘poleward flux’ model, kinetochores anchor kinetochore microtubules and chromatids are pulled towards the poles through the depolymerization of kinetochore microtubules at the minus ends6. Here, we show that two functionally distinct microtubule-destabilizing KinI kinesin enzymes (so named because they possess a kinesin-like ATPase domain positioned internally within the polypeptide) are responsible for normal chromatid-to-pole motion in Drosophila. One of them, KLP59C, is required to depolymerize kinetochore microtubules at their kinetochore-associated plus ends, thereby contributing to chromatid motility through a Pac-Man-based mechanism. The other, KLP10A, is required to depolymerize microtubules at their pole-associated minus ends, thereby moving chromatids by means of poleward flux.
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The authors declare that they have no competing financial interests.
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We would like to thank B. Kenigsberg, D. Buster, P. Baas, F. McNally, A. Asenjo and H. Sosa for critically reading the manuscript; I. Brust-Mascher for advice on FSM; and A. Desai and J. Minden for help with rhodamine-histone preparations. We also thank C. Sunkel for providing GFP-Polo kinase flies and protocols for isolating mitotic chromosomes. We are grateful to the following individuals for their gifts: GFP–tubulin flies from A. Spradling; GFP-DTACC flies from J. Raff; GFP–Rod flies from R. Karess; GFP-Cid flies from S. Henikoff; and G. Karpen for the anti-Cid antibody. We thank G. Law, P. Franklin and R. Sleeper (PerkinElmer) for their assistance with the Ultraview confocal microscope. This work was supported by grants from the National Institutes of Health to D.J.S., C.E.W, R.D.V. and J.M.S.. C.E.W is a Scholar of the Leukemia and Lymphoma Society.
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The Journal of Cell Biology (2019)
BMC Molecular and Cell Biology (2019)
Molecular Biology of the Cell (2019)
The Journal of Cell Biology (2018)
Biochemical Society Transactions (2018)