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The kinesin-14 Klp2 organizes microtubules into parallel bundles by an ATP-dependent sorting mechanism


The dynamic organization of microtubules into parallel arrays allows interphase cells to set up multi-lane highways for intracellular transport and M-phase cells to build the mitotic and meiotic spindles. Here we show that a minimally reconstituted system composed of Klp2, a kinesin-14 from the fission yeast Schizosaccharomyces pombe, together with microtubules assembled from purified S. pombe tubulin, autonomously assembles bundles of parallel microtubules. Bundles form by an ATP-dependent sorting mechanism that requires the full-length Klp2 motor. By this mechanism, antiparallel-overlapped microtubules slide over one another until they dissociate from the bundles, whereas parallel-overlapped microtubules are selectively trapped by an energy-dissipating force-balance mechanism. Klp2-driven microtubule sorting provides a robust pathway for the organization of microtubules into parallel arrays. In vivo evidence indicates that Klp2 is required for the proper organization of S. pombe interphase microtubules into bipolar arrays of parallel-overlapped microtubules1,2,3,4, suggesting that kinesin-14-dependent microtubule sorting may have wide biological importance.

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Figure 1: Purified full-length S. pombe
Figure 2: Microtubule bundling requires both the motor-domain and the N-terminal tail region of Klp2.
Figure 3: Full-length Klp2 organizes S. pombe microtubules into parallel bundles.
Figure 4: Force-balance model for motorized microtubule sorting.
Figure 5: Model for the S. pombe interphase IMA organization.

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We thank Joe Howard for the full-length Drosophila kinesin-1 construct and Michael Osei for purification of S. pombe tubulin and EGFP–tubulin. This work was supported by Marie Curie Cancer Care (A.D.M. and R.A.C.) and the Medical Research Council (R.A.C.).

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M.B. conceived, designed and performed the experiments, and contributed to the writing of this study; D.R.D. created S. pombe strains, developed the methodology for purification of S. pombe tubulin and helped write the manuscript; A.D.M. and R.A.C. designed experiments and wrote the manuscript.

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Correspondence to Andrew D. McAinsh.

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The authors declare no competing financial interests.

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Braun, M., Drummond, D., Cross, R. et al. The kinesin-14 Klp2 organizes microtubules into parallel bundles by an ATP-dependent sorting mechanism. Nat Cell Biol 11, 724–730 (2009).

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