MOLECULAR MECHANISM OF ACTION OF DNA DAMAGING AGENTS

本研究项目以细胞周期调控为主要研究对象 化疗敏感性的决定因素。我们的目标是利用细胞周期控制作为 为开发新的化疗策略奠定基础 选择性地杀死肿瘤细胞。研究的方向是分子 解剖人类细胞中的检查点控制系统并发现 肿瘤的缺陷。我们的计划是精确地绘制出这些控制系统 从DNA损伤或未复制的DNA被感知到 阻止细胞周期进程的反应元件。我们也是 寻找分子指标来预测检查点的保真度 控制力。人类淋巴瘤G2检查点的分子解剖 细胞显示，cdc2的活性受到抑制。 磷酸化。未能去除这些磷酸盐与 抑制cdc25C磷酸酶活性。CDC25C活性受以下因素上调 过度磷酸化，这种情况在G2期停滞细胞中没有发生。我们是 现在正在研究调节cdc25C的激酶/磷酸酶对。 对DNA损伤的反应。我们发现G2停滞并不抑制 Cyclin A/cdc2和Cyclin时细胞周期蛋白A/CDK2复合体的激活 B1/cdc2复合体的激活受到抑制。我们建议激活 细胞周期蛋白A/cdc2复合体可能与细胞周期蛋白B1/cdc2复合体共同作用 促进有丝分裂。我们还开始了对G1的描述 人类细胞中的检查点，强调肿瘤的作用 抑癌基因P53在DNA损伤诱导的G1期停滞。我们目前正在 P53与细胞周期蛋白依赖的G1/S期相互作用的研究 激活剂。我们正在研究激酶/磷酸酶抑制剂在 细胞周期控制以寻找可以增强细胞周期的调节器 化疗药物的抗肿瘤活性。例如，我们是 寻找无毒，无DNA损伤剂，延长一半- P53的寿命。这种药物将被用来阻止P53正常的细胞在 G1。然后，带有p53缺陷的肿瘤将被选择性地杀死 针对S和M期的细胞毒剂。

This research project focusses on cell cycle control as a major determinant of chemosensitivity. We aim to utilize cell cycle control as a basis for the development of new chemotherapeutic stratagems to selectively kill tumor cells. Research is oriented towards the molecular dissection of checkpoint control systems in human cells and to uncover defects in neoplasia. Our plan is to precisely map these control systems from the point where DNA damage or unreplicated DNA is sensed to the response elements that arrest cell cycle progression. We are also searching for molecular indicators to predict the fidelity of checkpoint control. Molecular dissection of the G2 checkpoint in human lymphoma cells revealed that the cdc2 kinase activity is suppressed by inhibitory phosphorylations. Failure to remove these phosphates correlated with suppression of the cdc25C phosphatase. Cdc25C activity is up-regulated by hyperphosphorylation and this did not occur in G2 arrested cells. We are now investigating the kinase/phosphatase couple that regulates cdc25C in response to DNA damage. We have found that G2 arrest does not inhibit the activation of cyclin A/cdk2 complexes while cyclin A/cdc2 and cyclin B1/cdc2 complex activation is suppressed. We suggest that activation of cyclin A/cdc2 complexes might act together with cyclin B1/cdc2 complexes to promote mitosis. We have also commenced a characterization of the G1 checkpoint in human cells with emphasis on the role of the tumor suppressor gene, p53 in G1 arrest induced by DNA damage. We are currently characterizing the interaction of p53 with the G1/S phase cyclin-dependent kinases. We are examining the actions of kinase/phosphatase inhibitors on cell cycle control to search for modulators that could enhance the antitumor activity of chemotherapeutic agents. For example, we are searching for non-toxic, non-DNA damaging agents that prolong the half- life of p53. Such agents will be used to arrest cells with normal p53 in G1. Tumors with defective p53 will then be selectively killed with cytotoxic agents specific for S and M phase.