title: Kinetochores accelerate centrosome separation to ensure faithful chromosome segregation.
abstract: At the onset of mitosis, cells need to break down their nuclear envelope, form a bipolar spindle and attach the chromosomes to microtubules via kinetochores. Previous studies have shown that spindle bipolarization can occur either before or after nuclear envelope breakdown. In the latter case, early kinetochore-microtubule attachments generate pushing forces that accelerate centrosome separation. However, until now, the physiological relevance of this prometaphase kinetochore pushing force was unknown. We investigated the depletion phenotype of the kinetochore protein CENP-L, which we find to be essential for the stability of kinetochore microtubules, for a homogenous poleward microtubule flux rate and for the kinetochore pushing force. Loss of this force in prometaphase not only delays centrosome separation by 5-6 minutes, it also causes massive chromosome alignment and segregation defects due to the formation of syntelic and merotelic kinetochore-microtubule attachments. By contrast, CENP-L depletion has no impact on mitotic progression in cells that have already separated their centrosomes at nuclear envelope breakdown. We propose that the kinetochore pushing force is an essential safety mechanism that favors amphitelic attachments by ensuring that spindle bipolarization occurs before the formation of the majority of kinetochore-microtubule attachments.
authors.affiliation: Institute of Biochemistry, ETH Zurich, Schafmattstrasse 18, 8093 Zürich,  Switzerland.
authors.forename: Nunu
authors.initials: N
authors.lastname: McHedlishvili
authors.forename: Samuel
authors.initials: S
authors.lastname: Wieser
authors.forename: René
authors.initials: R
authors.lastname: Holtackers
authors.forename: Julien
authors.initials: J
authors.lastname: Mouysset
authors.forename: Mukta
authors.initials: M
authors.lastname: Belwal
authors.forename: Ana C
authors.initials: AC
authors.lastname: Amaro
authors.forename: Patrick
authors.initials: P
authors.lastname: Meraldi
mesh_terms: D018797:Cell Cycle Proteins / Q000172:deficiency / Q000378:metabolism; D018385:Centrosome / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone; D020090:Chromosome Segregation; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints; D008869:Microtubule-Associated Proteins / Q000172:deficiency / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism; D049468:Prometaphase; D008941:Spindle Apparatus / Q000378:metabolism
chemical_list: C579361:CENPL protein, human; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D008869:Microtubule-Associated Proteins