Chromosomal attachments set length and microtubule number in the Saccharomyces cerevisiae mitotic spindle |
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| Authors: | Natalie J Nannas Eileen T O’Toole Mark Winey Andrew W Murray |
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| Institution: | University of Massachusetts;aMolecular and Cellular Biology Department, Harvard University, Cambridge, MA 02138;bFAS Center for Systems Biology, Harvard University, Cambridge, MA 02138;cBoulder Laboratory for 3D Electron Microscopy of Cells, University of Colorado, Boulder, CO 80309;dMolecular, Cellular, and Developmental Biology Department, University of Colorado, Boulder, CO 80309 |
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| Abstract: | The length of the mitotic spindle varies among different cell types. A simple model for spindle length regulation requires balancing two forces: pulling, due to microtubules that attach to the chromosomes at their kinetochores, and pushing, due to interactions between microtubules that emanate from opposite spindle poles. In the budding yeast Saccharomyces cerevisiae, we show that spindle length scales with kinetochore number, increasing when kinetochores are inactivated and shortening on addition of synthetic or natural kinetochores, showing that kinetochore–microtubule interactions generate an inward force to balance forces that elongate the spindle. Electron microscopy shows that manipulating kinetochore number alters the number of spindle microtubules: adding extra kinetochores increases the number of spindle microtubules, suggesting kinetochore-based regulation of microtubule number. |
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