Molecular basis of Cancer-specific cell cycle

哺乳动物Aurora-A与丝氨酸/苏氨酸蛋白激酶有关，该蛋白激酶最初通过其与酿酒酵母IpI 1 p和果蝇Aurora的密切同源性而被鉴定，这两种蛋白激酶是有丝分裂事件协调中的关键调节因子。Aurora-A的蛋白质水平、有丝分裂期间其峰值激酶活性及其活化已归因于磷酸化。在这里，我们表明，这种酶是一种丝氨酸定向激酶，并定义其底物特异性。我们还发现，Thr 288内的激活环是一个关键的残基激活磷酸化事件在体外，它是时空限制在一个简短的窗口，在有丝分裂复制中心体和纺锤体微管近端的两极在体内。免疫耗竭分析表明，Aurora-A的上游激酶可能存在于哺乳动物细胞中除了自磷酸化。此外，人激活的Aurora-A与在Thr 320上负磷酸化的负调节蛋白丝氨酸/苏氨酸磷酸酶1型（PP 1）形成复合物。有趣的是，磷酸特异性Aurora-A单克隆抗体在体外抑制Aurora-A激酶活性，提供了进一步的治疗途径。

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.