Ajuba: a new microtubule-associated protein that interacts with BUBR1 and Aurora B at kinetochores in metaphase.
BACKGROUND
The role of the LIM-domain-containing protein Ajuba was initially described in cell adhesion and migration processes and recently in mitosis as an activator of the Aurora A kinase.


RESULTS
In the present study, we show that Ajuba localizes to centrosomes and kinetochores during mitosis. This localization is microtubule-dependent and Ajuba binds microtubules in vitro. A microtubule regrowth assay showed that Ajuba follows nascent microtubules from centrosomes to kinetochores. Owing to its contribution to mitotic commitment and its microtubule-dependent localization, Ajuba could also play a role during the metaphase-anaphase transition. We show that Ajuba interacts with Aurora B and BUBR1 [BUB (budding uninhibited by benomyl)-related 1], two major components of the mitotic checkpoint. Inhibition of BUBR1 by siRNA (small interfering RNA) disrupts chromosome alignment at the metaphase plate and modifies Ajuba localization due to premature mitotic exit.


CONCLUSIONS
Ajuba is a microtubule-associated protein that collaborates with Aurora B and BUBR1 at the metaphase-anaphase transition and this may be important to ensure proper chromosome segregation.
Ferrand
Alexia
A
Centre de Recherche en Cancérologie de Marseille, Laboratoire d'Oncologie Moléculaire, UMR891 Inserm, Institut Paoli-Calmettes, Marseille 13009, France.
Chevrier
Véronique
V
Chauvin
Jean-Paul
JP
Birnbaum
Daniel
D
D000818:Animals; D064107:Aurora Kinase B; D064127:Aurora Kinases; D002460:Cell Line; D018385:Centrosome / Q000378:metabolism / Q000648:ultrastructure; D000072159:Dynactin Complex; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018386:Kinetochores / Q000378:metabolism* / Q000648:ultrastructure; D060588:LIM Domain Proteins; D008677:Metaphase / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism
C485608:AJUBA protein, human; D000072159:Dynactin Complex; C405804:EB1 microtubule binding proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; C502810:SS18L1 protein, human; D015534:Trans-Activators; C576921:AURKB protein, human; D064107:Aurora Kinase B; D064127:Aurora Kinases; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases