Regensburg 2016 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 58: Cytoskeletal Filaments
BP 58.2: Vortrag
Donnerstag, 10. März 2016, 10:00–10:15, H44
Overlap microtubules link sister k-fibers and balance the forces on bioriented kinetochores — •Maja Novak1, Janko Kajtez2, Anastasia Solomatina2, Iva M. Tolic3,2, and Pavin Nenad1 — 1Department of Physics, Faculty of Science, University of Zagreb, Bijenicka cesta 32, 10000 Zagreb, Croatia — 2Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany — 3Division of Molecular Biology, Rudjer Boskovic Institute, Bijenicka cesta 54, 10000 Zagreb, Croatia
During metaphase, forces on kinetochores are exerted by k-fibers, bundles of microtubules that end at the kinetochore. Interestingly, non-kinetochore microtubules have been observed between sister kinetochores, but their function is unknown. Here we show by laser-cutting of a k-fiber in HeLa and PtK1 cells that a bundle of non-kinetochore microtubules, which we term 'bridging fiber', bridges sister k-fibers and balances the inter-kinetochore tension [1]. We found PRC1 and EB3 in the bridging fiber, suggesting that it consists of anti-parallel dynamic microtubules. By using a theoretical model that includes a bridging fiber, we show that the forces at the pole and at the kinetochore depend on the bridging fiber thickness. Moreover, our theory and experiments show larger relaxation of the inter-kinetochore distance for cuts closer to kinetochores. We conclude that the bridging fiber, by linking sister k-fibers, withstands the tension between sister kinetochores and enables the spindle to obtain a curved shape.
[1] Kajtez, Solomatina, Novak et al., Nature Communnications (Accepted)