To assemble a bipolar spindle, microtubules emanating from two poles must bundle into an antiparallel midzone, where plus end–directed motors generate outward pushing forces to drive pole separation. Midzone cross-linkers and motors display only modest preferences for antiparallel filaments, and duplicated poles are initially tethered together, an arrangement that instead favors parallel interactions. Pivoting of microtubules around spindle poles might help overcome this geometric bias, but the intrinsic pivoting flexibility of the microtubule–pole interface has not been directly measured, nor has its importance during early spindle assembly been tested. By measuring the pivoting of microtubules around isolated yeast spindle poles, we show that pivoting flexibility can be modified by mutating a microtubule-anchoring pole component, Spc110. By engineering mutants with different flexibilities, we establish the importance of pivoting in vivo for timely pole separation. Our results suggest that passive thermal pivoting can bring microtubules from side-by-side poles into initial contact, but active minus end–directed force generation will be needed to achieve antiparallel alignment.
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January 19 2021
Microtubule pivoting enables mitotic spindle assembly in S. cerevisiae
Kimberly K. Fong
,
Kimberly K. Fong
1
Department of Physiology and Biophysics, University of Washington, Seattle, WA
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Trisha N. Davis
,
2
Department of Biochemistry, University of Washington, Seattle, WA
Trisha N. Davis: tdavis@uw.edu
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Charles L. Asbury
1
Department of Physiology and Biophysics, University of Washington, Seattle, WA
Correspondence to Charles L. Asbury: casbury@uw.edu
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Kimberly K. Fong
1
Department of Physiology and Biophysics, University of Washington, Seattle, WA
Trisha N. Davis
2
Department of Biochemistry, University of Washington, Seattle, WA
Charles L. Asbury
1
Department of Physiology and Biophysics, University of Washington, Seattle, WA
Correspondence to Charles L. Asbury: casbury@uw.edu
Trisha N. Davis: tdavis@uw.edu
Received:
July 31 2020
Revision Received:
December 07 2020
Accepted:
December 16 2020
Online Issn: 1540-8140
Print Issn: 0021-9525
Funding:
National Institutes of Health
(P01GM105537, R35GM134842, R35GM130293)
© 2021 Fong et al.
2021
This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms/). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/).
J Cell Biol (2021) 220 (3): e202007193.
Article history
Received:
July 31 2020
Revision Received:
December 07 2020
Accepted:
December 16 2020
Citation
Kimberly K. Fong, Trisha N. Davis, Charles L. Asbury; Microtubule pivoting enables mitotic spindle assembly in S. cerevisiae. J Cell Biol 1 March 2021; 220 (3): e202007193. doi: https://doi.org/10.1083/jcb.202007193
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