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A more recent version of this article appeared on August 1, 2007
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Submitted on February 8, 2007
Revised on May 9, 2007
Accepted on May 23, 2007
*Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755;
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195
Monitoring Editor: Ted Salmon
The human genome has three unique genes coding for kinesin-13 proteins called Kif2a, Kif2b, and MCAK (Kif2c). Kif2a and MCAK have documented roles in mitosis, but the function of Kif2b has not been defined. Here, we show that Kif2b is expressed at very low levels in cultured cells and that GFP-Kif2b localizes predominately to centrosomes and midbodies, but also to spindle microtubules and transiently to kinetochores. Kif2b-deficient cells assemble monopolar or disorganized spindles. Chromosomes in Kif2b-deficient cells show typical kinetochore-microtubule attachments, but the velocity of movement is reduced
80% compared with control cells. Some Kif2b-deficient cells attempt anaphase, but the cleavage furrow regresses and cytokinesis fails. Like Kif2a-deficient cells, bipolar spindle assembly can be restored to Kif2b-deficient cells by simultaneous deficiency of MCAK or Nuf2 or treatment with low doses of nocodazole. However, Kif2b-deficient cells are unique in that they assemble bipolar spindles when the pole focusing activities of NuMA and HSET are perturbed. These data demonstrate that Kif2b function is required for spindle assembly and chromosome movement and that the microtubule depolymerase activities of Kif2a, Kif2b and MCAK fulfill distinct functions during mitosis in human cells.
These authors contributed equally to this work.
Address correspondence to:
Duane A. Compton (duane.a.compton{at}dartmouth.edu)
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