title: Centrobin regulates the assembly of functional mitotic spindles.
abstract: The proper function of the spindle is crucial to the high fidelity of chromosome segregation and is indispensable for tumor suppression in humans. Centrobin is a recently identified centrosomal protein that has a role in stabilizing the microtubule structure. Here we functionally characterize the defects in centrosome integrity and spindle assembly in Centrobin-depleted cells. Centrobin-depleted cells show a range of spindle abnormalities including unfocused poles that are not associated with centrosomes, S-shaped spindles and mini spindles. These cells undergo mitotic arrest and subsequently often die by apoptosis, as determined by live cell imaging. Co-depletion of Mad2 relieves the mitotic arrest, indicating that cells arrest due to a failure to silence the spindle checkpoint in metaphase. Consistent with this, Centrobin-depleted metaphase cells stained positive for BubR1 and BubR1 S676. Staining with a panel of centrosome markers showed a loss of centrosome anchoring to the mitotic spindle. Furthermore, these cells show less cold-stable microtubules and a shorter distance between kinetochore pairs. These results show a requirement of Centrobin in maintaining centrosome integrity, which in turn promotes anchoring of mitotic spindle to the centrosomes. Furthermore, this anchoring is required for the stability of microtubule-kinetochore attachments and biogenesis of tension-ridden and properly functioning mitotic spindle.
authors.affiliation: Signal Transduction Laboratory, Cancer and Cell Biology Division, Queensland Institute of Medical Research, Brisbane, Queensland, Australia.
authors.forename: J M
authors.initials: JM
authors.lastname: Jeffery
authors.forename: A J
authors.initials: AJ
authors.lastname: Urquhart
authors.forename: V N
authors.initials: VN
authors.lastname: Subramaniam
authors.forename: R G
authors.initials: RG
authors.lastname: Parton
authors.forename: K K
authors.initials: KK
authors.lastname: Khanna
mesh_terms: D034961:Antigens, Nuclear / Q000032:analysis; D002135:Calcium-Binding Proteins / Q000502:physiology; D018797:Cell Cycle Proteins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D064246:Mad2 Proteins; D000072379:NIMA-Related Kinases; D034521:Nuclear Matrix-Associated Proteins / Q000032:analysis; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D012097:Repressor Proteins / Q000502:physiology; D008941:Spindle Apparatus / Q000502:physiology*; D014404:Tubulin / Q000032:analysis; D000097869:Polo-Like Kinase 1
chemical_list: D034961:Antigens, Nuclear; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D064246:Mad2 Proteins; D000072379:NIMA-Related Kinases; D034521:Nuclear Matrix-Associated Proteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D014404:Tubulin; D000097869:Polo-Like Kinase 1; C507203:CNTROB protein, human; C577697:MAD2L1 protein, human; C050045:NUMA1 protein, human; C089441:NEK2 protein, human