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Vol. 18, Issue 6, 2216-2225, June 2007

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Mitotic Chromosome Biorientation in Fission Yeast Is Enhanced by Dynein and a Minus-end–directed, Kinesin-like Protein

Ekaterina L. Grishchuk^*,, Ilia S. Spiridonov^*,, and J. Richard McIntosh^*

*Molecular, Cellular, and Developmental Biology Department, University of Colorado at Boulder, Boulder, CO 80309; Institute of General Pathology and Pathophysiology, Moscow 125315, Russia; and National Research Center for Hematology, Moscow 125167, Russia

Submitted November 6, 2006; Revised February 27, 2006; Accepted March 22, 2007
Monitoring Editor: Kerry Bloom

Chromosome biorientation, the attachment of sister kinetochores to sister spindle poles, is vitally important for accurate chromosome segregation. We have studied this process by following the congression of pole-proximal kinetochores and their subsequent anaphase segregation in fission yeast cells that carry deletions in any or all of this organism's minus end–directed, microtubule-dependent motors: two related kinesin 14s (Pkl1p and Klp2p) and dynein. None of these deletions abolished biorientation, but fewer chromosomes segregated normally without Pkl1p, and to a lesser degree without dynein, than in wild-type cells. In the absence of Pkl1p, which normally localizes to the spindle and its poles, the checkpoint that monitors chromosome biorientation was defective, leading to frequent precocious anaphase. Ultrastructural analysis of mutant mitotic spindles suggests that Pkl1p contributes to error-free biorientation by promoting normal spindle pole organization, whereas dynein helps to anchor a focused bundle of spindle microtubules at the pole.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Ekaterina L. Grishchuk (Katya{at}colorado.edu)

Abbreviations used: DAPI, 4',6'-diamidino-2-phenylindole dihydrochloride; EM, electron microscopy; ET, electron tomography; GFP, green fluorescent protein; MT, microtubule; SPB, spindle pole body.