Kinetochore-generated pushing forces separate centrosomes during bipolar spindle assembly.
In animal somatic cells, bipolar spindle formation requires separation of the centrosome-based spindle poles. Centrosome separation relies on multiple pathways, including cortical forces and antiparallel microtubule (MT) sliding, which are two activities controlled by the protein kinase aurora A. We previously found that depletion of the human kinetochore protein Mcm21R(CENP-O) results in monopolar spindles, raising the question as to whether kinetochores contribute to centrosome separation. In this study, we demonstrate that kinetochores promote centrosome separation after nuclear envelope breakdown by exerting a pushing force on the kinetochore fibers (k-fibers), which are bundles of MTs that connect kinetochores to centrosomes. This force is based on poleward MT flux, which incorporates new tubulin subunits at the plus ends of k-fibers and requires stable k-fibers to drive centrosomes apart. This kinetochore-dependent force becomes essential for centrosome separation if aurora A is inhibited. We conclude that two mechanisms control centrosome separation during prometaphase: an aurora A-dependent pathway and a kinetochore-dependent pathway that relies on k-fiber-generated pushing forces.
Toso
Alberto
A
Institute of Biochemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
Winter
Jennifer R
JR
Garrod
Ainslie J
AJ
Amaro
Ana C
AC
Meraldi
Patrick
P
McAinsh
Andrew D
AD
D000818:Animals; D064127:Aurora Kinases; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D018385:Centrosome / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D013314:Stress, Mechanical
D018797:Cell Cycle Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases