Building a Systems-Level View of Cell Cycle Checkpoints

描述（由申请人提供）：由于细胞周期是所有真核生物生长和发育的基础，并且细胞周期的错误调节是癌症的类型，因此在现代细胞生物学中，实现对细胞周期如何被控制的系统级理解是最重要的目标之一。在高度互动的协作中，将实验生物学与数学建模相结合，为开发对细胞周期控制的全面理解提供了强有力的方法。这种方法被用来发现有丝分裂转变是由迟滞和双稳定性调节的。下一个目标是通过解决一个关键问题来建立这个基础：细胞周期引擎如何受到外部事件的影响，特别是那些威胁基因组完整性的事件。当存在对基因组稳定性的威胁（如未复制或受损的DMA）时，检查点会阻止细胞周期。几乎所有癌细胞都具有检查点控制缺失的特征。检查点将在非洲爪蟾卵和爪蟾胚胎中实验可处理的无细胞提取物中进行研究，其中细胞周期在早期发育期间广泛重塑。为了建立这种理解，将构建DNA复制检查点的数学模型并进行严格的实验测试。该模型应揭示潜在的动力学控制，并作为预测病理和药理学扰动对细胞周期检查点影响的有力工具。为了达到构建DNA复制检查点的系统级视图的目标，将完成以下具体目标：1)构建未复制DNA对核心细胞周期引擎影响的数学模型，优化参数，并将模型在万维网上公开使用。2)同时，将进行关于细胞核浓度和细胞周期酶如何影响DNA复制检查点的关键定量实验，并使用数据为模型提供信息。3)一旦这个关于未复制DNA如何影响细胞周期引擎的基本观点到手，该模型将扩展到包括Chk1激酶信号通路，这是癌症化疗的关键潜在靶点。4)最后，该模型将面临挑战，即在早期发育过程中准确地表示DNA复制检查点的三种不同行为，为模型提供生理测试用例，并告知需要额外数据的地方。

DESCRIPTION (provided by applicant): Because the cell cycle underlies the growth and development of all eukaryotes, and misregulation of the cell cycle typifies cancers, achieving a systems-level understanding of how the cell cycle is controlled ranks among the most important goals in modern cell biology. Pairing experimental biology with mathematical modeling in a highly interactive collaboration creates a powerful approach to develop a comprehensive understanding of cell cycle control. This approach was used to discover that mitotic transitions are regulated by hysteresis and bistability. The next goal is to build on this foundation by addressing a critical issue: how the cell cycle engine is affected by external events, in particular, those events that threaten the integrity of the genome. Checkpoints arrest the cell cycle when a threat to genomic stability, such as unreplicated or damaged DMA, exists. Loss of checkpoint control characterizes nearly all cancer cells. Checkpoints will be investigated in the experimentally tractable cell-free extracts derived from eggs of Xenopus laevis and in Xenopus embryos, where the cell cycle extensively remodels during early development. To build this understanding, a mathematical model of the DNA replication checkpoint will be constructed and subjected to rigorous experimental testing. This model should reveal underlying dynamical controls and serve as a powerful tool for predicting the effect of pathologic and pharmacologic perturbations upon cell cycle checkpoints. To reach the goal of constructing a systems-level view of the DNA replication checkpoint, the following specific aims will be completed: 1) A mathematical model representing the effect of unreplicated DNA on the core cell cycle engine will be constructed, parameters will be optimized, and the model will be made available for public use on the World Wide Web. 2) Concurrently, key quantitative experiments concerning how nuclear concentration and cell cycle enzymes impact the DNA replication checkpoint will be conducted and data used to inform the model. 3) Once this fundamental view of how unreplicated DNA affects the cell cycle engine is in hand, the model will be extended to include the Chk1 kinase signaling pathway, a key potential target for cancer chemotherapeutics. 4) Finally, the model will be challenged to accurately represent three distinct behaviors of the DNA replication checkpoint during early development, providing a physiologic test case for the model and informing where additional data are needed.