Mechanisms of Mitotic Activation of the ATM kinase

描述（申请人提供）：ATM突变可导致人类常染色体隐性疾病共济失调-毛细血管扩张症（ataxia - telangiecasia, a- t），在维持遗传稳定性和预防癌症形成中起关键作用。ATM是一种类似PI-3的激酶，在DNA损伤反应中起传感器和信号换能器的作用。目前，大多数对ATM功能的研究都集中在其在电离辐射诱导的DNA双链断裂的细胞反应中的重要作用上。然而，由于A-T表型的复杂性和许多A-T表型不能简单地解释为缺乏最佳的DNA损伤反应，在没有DNA损伤的情况下，ATM的功能必须进一步研究。我们发现，ATM是激活纺锤体检查点所必需的，纺锤体检查点是通过延迟姐妹染色单体分离来防止染色体错误分离的过程。我们的初步数据表明，在没有DNA损伤的情况下，ATM在有丝分裂期间被激活。有丝分裂依赖性的ATM激活需要功能性的Aurora-B。此外，我们发现Aurora-B在体外和体内都磷酸化了ATM的Ser1403位点。深入研究发现，在有丝分裂过程中，Aurora-B与ATM相关，而ATM是Bub1活性所必需的。进一步，我们发现ATM使Bub1（在Ser314处）和Mad 1（在Ser214处）磷酸化。我们在这一提议中的一般假设是，ATM的有丝分裂激活是由Aurora-B控制的，并且在纺锤体检查点的调节中具有功能意义。因此，我们建议研究ATM的有丝分裂激活机制，并剖析纺锤体检查点的ATM通路。提出了三个具体目标。目的1将重点研究ATM活化的分子机制。目的2将研究ATM Ser1403磷酸化在有丝分裂进程和纺锤体检查点中的作用。目的3将重点研究有丝分裂依赖的ATM下游靶标磷酸化的功能意义。我们这个项目的长期目标是更好地了解ATM在有丝分裂细胞周期控制中的作用，作为深入了解癌变、细胞生长和细胞死亡的一般机制的基础。剖析ATM在有丝分裂中的重要作用可能有助于理解许多a - t表型并找到治疗该疾病的方法。

DESCRIPTION (provided by applicant): ATM, mutation of which leads to the human autosomal recessive disorder Ataxia-Telangiectasia (A-T), plays a critical role in maintaining genetic stability and preventing cancer formation. ATM is a PI-3 like kinase that functions as a sensor and signal transducer in DNA damage responses. Currently, most of the functional studies of ATM focus on its essential role in the cellular response to ionizing radiation-induced DNA double strand breaks. However, because of the complexity of A-T phenotypes and many of the A-T phenotypes cannot be simply explained by the lack of an optimal DNA damage response, functions of ATM in the absence of DNA damage must be further examined. We have found that ATM was required for the activation of the spindle checkpoint, a process that protects against chromosome missegregation by delaying sister chromatid separation. Our preliminary data demonstrated that ATM was activated during mitosis in the absence of DNA damage. The mitosis-dependent activation of ATM requires functional Aurora-B. Furthermore we found that Aurora-B phosphorylated ATM at Ser1403 both in vitro and in vivo. In depth studies have found that Aurora-B associated with ATM during mitosis and ATM was required for the activity of Bub1. Further we found that ATM phosphorylated Bub1 (at Ser314) and Mad 1(at Ser214). Our general hypothesis in this proposal is that mitotic activation of ATM is governed by Aurora-B and has functional significance in regulation of the spindle checkpoint. Therefore we propose to study the mechanisms of mitotic activation of ATM and to dissect the ATM pathways in the spindle checkpoint. Three specific aims are proposed. Aim 1 will focus on investigate the molecular mechanism of the ATM activation. Aim 2 will study the role of ATM Ser1403 phosphorylation on mitotic progression and the spindle checkpoint. Aim 3 will focus on studying the functional significance of mitotic- dependent ATM phosphorylation of its downstream target. Our long-term goal of this project is to better understand the role of ATM in mitotic cell cycle control as a basis for providing insights into general mechanisms of carcinogenesis, cell growth and cell death. Dissecting the important role of ATM in mitosis may help understand many A-T phenotypes and find a cure for the disease.