Chromosomal attachments set length and microtubule number in the Saccharomyces cerevisiae mitotic spindle.
Bottom Line: 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 micro-tubules 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.
Affiliation: Molecular and Cellular Biology Department, Harvard University, Cambridge, MA 02138 FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138.Show MeSH
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Mentions: Adding extra kinetochores to wild-type cells should shorten their spindles by creating more attachments between the spindle poles and the chromosomes (Figure 1D). We introduced additional kinetochores in the form of minichromosomes or centromeric plasmids (Figure 5A), which assemble a fully functional kinetochore (Clarke and Carbon, 1980). Multiple centromeric plasmids slow the cell cycle (Futcher and Carbon, 1986), but this delay depends on the spindle checkpoint and is completely eliminated in mad2∆ strains (Wells and Murray, 1996), which lack the checkpoint. We therefore used checkpoint-deficient cells to allow us to add substantial numbers of extra kinetochores without delaying progress through mitosis.
Affiliation: Molecular and Cellular Biology Department, Harvard University, Cambridge, MA 02138 FAS Center for Systems Biology, Harvard University, Cambridge, MA 02138.