K-fiber bundles in the mitotic spindle are mechanically reinforced by Kif15

Abstract

The mammalian kinetochore fiber (k-fiber) connects chromosomes to the spindle and supports segregation. We cut k-fibers by laser ablation to probe mechanical connections of microtubules within the bundle. We find that kinesin-12 Kif15 cross-links mediate k-fiber bundling. K-fiber bundling forces are in active competition with forces that cluster microtubule minus-ends.