Molecular basis of Cancer-specific cell cycle

哺乳动物Aurora-A与一种丝氨酸/苏氨酸蛋白激酶有关，它最初被认为与酿酒酵母IpI1p和黑腹果蝇极光密切同源，后者是有丝分裂事件编排的关键调节因子。Aurora-A的蛋白水平、有丝分裂过程中的最高激酶活性以及它的激活都归因于磷酸化。在这里，我们证明该酶是一种精氨酸导向的激酶，并确定其底物的专一性。我们还发现，激活环中的Thr288是体外激活磷酸化事件的关键残基，它在体内被限制在复制的中心体和两极附近的纺锤体微管上有丝分裂的一个短暂窗口。免疫耗竭分析表明，哺乳动物细胞中除了自身磷酸化外，还可能存在Aurora-A的上游激酶(S)。此外，人激活的Aurora-A与Thr320上被负磷酸化的负调控蛋白丝氨酸/苏氨酸磷酸酶1(PP1)形成复合体。有趣的是，磷酸特异的Aurora-A单抗在体外抑制Aurora-A激酶的活性，提供了进一步的治疗途径来探索。

Mammalian Aurora-A is related to a serine/threonine protein kinase that was originally identified by its close homology with Saccharomyces cerevisiae IpI1p and Drosophila melanogaster aurora that are key regulators in the orchestration of mitotic events. The protein level of Aurora-A, its peak kinase activity during mitosis and its activation have been attributed to phosphorylation. Here we show that this enzyme is an arginine-directed kinase and define its substrate specificity. We also found that Thr288 within the activation loop is a critical residue for activating phosphorylation events in vitro and that it is spatiotemporally restricted to a brief window at mitosis on duplicated centrosomes and on spindle microtubules proximal to the poles in vivo. Immunodepletion assays indicated that an upstream kinase(s) of Aurora-A might exist in mammalian cells in addition to autophosphorylation. Furthermore, human activated Aurora-A forms complexes with the negative regulator protein serine/threonine phosphatase type 1 (PP1) that was negatively phosphorylated on Thr320. Interestingly, phospho-specific Aurora-A monoclonal antibodies restrain Aurora-A kinase activity in vitro, providing further therapeutic avenues to explore.