engleski

Relaxation of interkinetochore tension after severing of a k-fiber depends on the length of the k-fiber stub

During mitosis, tension forces acting on kinetochores are required for passage through the spindle assembly checkpoint and for chromatid segregation. It is generally thought that the interkinetochore tension is generated by molecular events occurring at the ends of k-fibers, bundles of microtubules bound to kinetochores. However, recent work has shown that bridging microtubules, which interact laterally with sister k-fibers and act as a bridge between sister kinetochores, contribute to interkinetochore tension. We set out to test the role of the bridging fibers in the origin of interkinetochore tension during metaphase in human U2OS and rat-kangaroo PtK1 cells. We severed k-fibers at different distances from the kinetochore and measured the change in the interkinetochore distance, which we use as a readout of the change in interkinetochore tension. We found that severing of a k-fiber closer to the kinetochore results in a larger relaxation of the interkinetochore tension than severing far from the kinetochore. These findings imply that a long k- fiber stub, which remains connected to the bridging fiber, withstands the interkinetochore tension and prevents relaxation of the interkinetochore distance, whereas a short stub does not. Thus, our results are consistent with a role of bridging microtubules in the origin of interkinetochore tension.

microtubules, mitosis ; kinetochore ; mitotic spindle ; laser microsurgery

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