Human Molecular Genetics Advance Access originally published online on October 9, 2007
Human Molecular Genetics 2008 17(2):215-224; doi:10.1093/hmg/ddm298
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ASAP is a novel substrate of the oncogenic mitotic kinase Aurora-A: phosphorylation on Ser625 is essential to spindle formation and mitosis
1 Groupe Microtubules et Cycle Cellulaire and 2 Groupe Cycle Cellulaire et Myogenèse, Institut de Génétique Humaine, CNRS UPR 1142, rue de la cardonille, 34396 Montpellier cédex 5, France 3 CNRS UMR 6061, Institut de Génétique et Développement, Université de Rennes I, IFR 140, 2 Avenue du Pr Léon Bernard, 35043 Rennes, France
* To whom correspondence should be addressed. Tel: +33 499619935; Fax: +33 499619901; Email: rouquier{at}igh.cnrs.fr
Received August 28, 2007; Revised August 28, 2007; Accepted October 5, 2007
Proper chromosome segregation is required to maintain the appropriate number of chromosomes from one cell generation to another and to prevent aneuploidy, which is mainly found in solid cancers. A correct mitotic spindle is necessary to accomplish such a process. Aurora kinases play critical roles in chromosome segregation and cell division; their deregulation impairs spindle assembly, checkpoint function and cell division causing chromosome mis-segregation. These kinases have been implicated in tumorigenesis. Aurora-A (AurA), in particular has been identified as a cancer-susceptibility gene, is overexpressed in a number of tumors and is required for G2/M transition and spindle assembly. ASAP is a novel spindle-associated protein, the deregulation of which induces severe mitotic defects. We show here that ASAP is a novel substrate of AurA kinase. We have identified serine 625 as the major phosphorylation site for AurA in vivo and localized the phosphorylated form of ASAP to centrosomes from late G2 to telophase, and around the midbody during cytokinesis. AurA depletion induces a proteasome-dependent degradation of ASAP. ASAP depletion induces spindle defects rescued by the expression of the phosphorylation-mimetic mutant ASAP-S625E and not by the non-phosphorylatable mutant ASAP-S625A. Microinjection of mono-specific S625 phospho-antibodies also impaired spindle formation and mitosis. These results strongly indicate that the phosphorylation of ASAP on S625 by AurA is required for bipolar spindle assembly and is essential for a correct mitotic progression. All together, these results suggest that we have identified a novel AurA substrate, pointing out ASAP as a new potential target for antitumoral drugs.