1. Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
2. The Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143, USA
3. Medical Sciences Program, Indiana University, Bloomington, Indiana 47405, USA
4. Center for Genetics and Development and Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA

Correspondence to: David J. Sharp¹ Correspondence and requests for materials should be addressed to D.J.S. (Email: dsharp@aecom.yu.edu).

Abstract

During anaphase identical sister chromatids separate and move towards opposite poles of the mitotic spindle^{1, 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 tracks^{4, 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.

1. Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
2. The Howard Hughes Medical Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143, USA
3. Medical Sciences Program, Indiana University, Bloomington, Indiana 47405, USA
4. Center for Genetics and Development and Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA

Correspondence to: David J. Sharp¹ Correspondence and requests for materials should be addressed to D.J.S. (Email: dsharp@aecom.yu.edu).

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