title: Regulation of Xenopus Aurora A activation by TPX2.
abstract: The oncogenic protein kinase Aurora A is a critical regulator of meiotic and mitotic cell cycles in eukaryotic cells. Aurora A autoactivation by autophosphorylation is promoted by specific non-catalytic binding proteins. One such protein is TPX2, a required spindle assembly factor in higher eukaryotes whose ability to activate Aurora A by direct binding to the kinase catalytic domain has been established by biochemical and structural analysis. In this report we clarify the autoactivation mechanism of Aurora A by demonstrating that of seven amino acids which become autophosphorylated by Aurora A, only Thr-295 is required for activity. Association of Aurora A with TPX2 leads to activation of the kinase, in parallel with phosphorylation of TPX2. We identify the sites as three Ser residues in the N terminus of TPX2; however, mutation of these residues does not affect Aurora A activation by TPX2. In contrast, the mutation of a putative Aurora A-binding motif in TPX2 abolishes both phosphorylation of TPX2 and activation of Aurora A. We have also investigated the interaction between Xenopus p53 and Xenopus Aurora A. p53 blocks the activity of either full-length Aurora A or the isolated catalytic domain. Interestingly, inhibition is blocked by TPX2, suggesting that the ability of Aurora A to transform cells could be regulated by p53, TPX2, or other binding proteins.
authors.affiliation: Howard Hughes Medical Institute and Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado 80262, USA.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Eyers
authors.forename: James L
authors.initials: JL
authors.lastname: Maller
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064127:Aurora Kinases; D001665:Binding Sites / Q000235:genetics; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D009154:Mutation; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D013379:Substrate Specificity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis
chemical_list: D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; C486551:TPX2 protein, Xenopus; D016159:Tumor Suppressor Protein p53; D029867:Xenopus Proteins; D011494:Protein Kinases; C112134:AURKA protein, Xenopus; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases