Cell Cycle and Checkpoint Control

描述（由申请人提供）：本提案的长期目标是了解在正常细胞周期中如何调节细胞分裂周期（细胞周期控制）以及当检测到未复制或损坏的DNA时如何阻止细胞周期进程（检查点控制）。细胞从细胞周期的一个阶段进入下一个阶段是由几个不同的控制因素调节的，这些控制因素作用于细胞周期蛋白基因的转录；细胞周期蛋白的降解；细胞周期蛋白依赖性蛋白激酶（Cdks）通过可逆磷酸化和与调控亚基的关联进行修饰；最后是细胞周期蛋白/Cdk组分及其调节因子的细胞内区隔化。Cdc25蛋白磷酸酶通过激活CDKs积极调节细胞分裂周期，它们也是检查点控制的靶点。在人类和啮齿动物中，Cdc25家族有三个成员，分别是Cdc25A、B和c。研究旨在阐明Cdc25A蛋白磷酸酶如何在整个细胞分裂周期中受到调节，并响应检查点激活。此外，还提出了旨在区分Cdc25A、Cdc25B和Cdc25C在小鼠和人类细胞中对细胞周期进程和检查点控制的个体贡献的研究。最后，研究将阐明检查点激酶、Chkl和Chk2如何被未复制的DNA和/或基因毒性应激激活，以及这些激酶如何与细胞周期机制相结合，在未复制或受损DNA存在的情况下导致细胞周期延迟。由于许多癌症既不能用现有的策略治愈，也不能在早期发现，因此需要确定既可以用作诊断探针又可以用作治疗靶点的新靶点。本研究概述了细胞周期控制和检查点控制的基本机制。参与这些途径的蛋白质可能有一天会被用作诊断标记物或设计抗增殖药物的靶标。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to understand how the cell division cycle is regulated during a normal cell cycle (cell cycle control) and how cell cycle progression is prevented when unreplicated or damaged DNA is detected (checkpoint control). The passage of cells from one stage of the cell cycle to the next is regulated by several distinct controls that act on the transcription of cyclin genes; the degradation of cyclin proteins; the modification of the cyclin-dependent protein kinases (Cdks) by both reversible phosphorylation and by association with regulatory subunits; and finally by intracellular compartmentalization of cyclin/Cdk components and their regulators. The Cdc25 protein phosphatases positively regulate the cell division cycle by activating CDKs and they are also targets of checkpoint control. In humans and rodents, there are three members of the Cdc25 family, designated Cdc25A, B and C. Studies aimed at elucidating how the Cdc25A protein phosphatase is regulated throughout the cell division cycle and in response to checkpoint activation are proposed. In addition, studies aimed at distinguishing the individual contributions made by Cdc25A, Cdc25B and Cdc25C to cell cycle progression and checkpoint control in both mouse and human cells are proposed. Finally, studies will be performed to elucidate how the checkpoint kinases, Chkl and Chk2 are activated by unreplicated DNA and/or genotoxic stress and how these kinases interface with the cell cycle machinery to cause cell cycle delays in the presence of unreplicated or damaged DNA. Because many cancers are neither curable using existing strategies nor readily detectable at early stages there is a need to identify new targets that can be used both as diagnostic probes and as therapeutic targets. The studies outlined in this proposal investigate basic mechanisms of cell cycle control and checkpoint control. Proteins involved in these pathways may one day be used as diagnostic markers or as targets for designing anti-proliferative drugs.