title: Aurora B regulates spindle bipolarity in meiosis in vertebrate oocytes.
abstract: Aurora B (Aur-B) plays multiple roles in mitosis, of which the best known are to ensure bi-orientation of sister chromatids by destabilizing incorrectly attached kinetochore microtubules and to participate in cytokinesis. Studies in Xenopus egg extracts, however, have indicated that Aur-B and the chromosome passenger complex play an important role in stabilizing chromosome-associated spindle microtubules. Aur-B stabilizes spindle microtubules in the egg extracts by inhibiting the catastrophe kinesin MCAK. Whether or not Aur-B plays a similar role in intact oocytes remains unknown. Here we have employed a dominant-negative Aur-B mutant (Aur-B122R, in which the ATP-binding lysine(122) is replaced with arginine) to investigate the function of Aur-B in spindle assembly in Xenopus oocytes undergoing meiosis. Overexpression of Aur-B122R results in short bipolar spindles or monopolar spindles, with higher concentrations of Aur-B122R producing mostly the latter. Simultaneous inhibition of MCAK translation in oocytes overexpressing Aur-B122R results in suppression of monopolar phenotype, suggesting that Aur-B regulates spindle bipolarity by inhibiting MCAK. Furthermore, recombinant MCAK-4A protein, which lacks all four Aur-B phosphoryaltion sites and is therefore insensitive to Aur-B inhibition but not wild-type MCAK, recapitulated the monopolar phenotype in the oocytes. These results suggest that in vertebrate oocytes that lack centrosomes, one major function of Aur-B is to stabilize chromosome-associated spindle microtubules to ensure spindle bipolarity.
authors: Ottawa Hospital Research Institute, Ottawa Hospital Civic Campus, Ottawa, ON, Canada.
authors: Hua
authors: H
authors: Shao
authors: Chunqi
authors: C
authors: Ma
authors: Xuan
authors: X
authors: Zhang
authors: Ruizhen
authors: R
authors: Li
authors: Ann L
authors: AL
authors: Miller
authors: William M
authors: WM
authors: Bement
authors: X Johné
authors: XJ
authors: Liu
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D064127:Aurora Kinases; D016547:Kinesins / Q000378:metabolism*; D008540:Meiosis; D009865:Oocytes / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism*; D014982:Xenopus laevis / Q000254:growth & development / Q000378:metabolism
chemical_list: D029867:Xenopus Proteins; C509242:mitotic centromere-associated kinesin, Xenopus; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D016547:Kinesins