DNA REPLICATION CHECKPOINT

真核细胞使用细胞周期检查点来确保有丝分裂被延迟，直到染色体完全复制和修复。酵母和哺乳动物细胞中的检查点突变体对抑制DNA合成或损伤DNA的试剂过敏。 哺乳动物细胞中的检查点突变体也容易发生染色体重排、断裂或丢失，这些事件通常与癌症和其他疾病有因果关系。 该项目的目的是在一个非常基本的水平上了解当DNA复制被药物羟基脲（HU）减慢或停止时所参与的检查点事件。 这种复制或HU检查点阻止有丝分裂的开始。 研究将使用裂殖酵母粟酒裂殖酵母进行。 这种生物体已成为研究细胞周期和检查点控制的杰出模型系统，这些细胞周期和检查点控制通常在大多数物种（包括人类）中保守。 研究将集中在Cds1上，这是一种蛋白激酶，似乎在复制检查点中起着核心作用。 该项目有三个具体目标。 第一个目标是了解Cds 1如何帮助强制执行复制检查点。 调节有丝分裂开始的蛋白质将作为Cds1的靶标进行评价。 第二个目的是了解Cds1是如何调节的。 将研究激活Cds1并使其磷酸化其底物的机制。 第三个目的是揭示限制Cds1的核定位到细胞周期的DNA合成（S）期的机制。 这些研究将提高对Cds1作为裂变酵母中检查点机制的重要元素的理解，并将为研究人类同源蛋白质的功能提供框架。

Eukaryotic cells use cell cycle checkpoints to ensure that mitosis is delayed until chromosomes are completely replicated and repaired. Checkpoint mutants in yeast and mammalian cells are hypersensitive to agents that inhibit DNA synthesis or damage DNA. Checkpoint mutants in mammalian cells are also prone to rearrangement, fragmentation or loss of chromosomes, events that are often causally associated with cancer and other diseases. The aim of this project is to understand at a very basic level the checkpoint events that are engaged when DNA replication is slowed or halted by the drug hydroxyurea (HU). This replication or HU checkpoint prevents the onset of mitosis. The studies will be carried out with the fission yeast Schizosaccharomyces pombe. This organism has served as an outstanding model system for the investigation of cell cycle and checkpoint controls that are generally conserved amongst most species, including humans. The investigations will focus on Cds1, a protein kinase that appears to play a central role in the replication checkpoint. The project has three specific aims. The first aim is to understand how Cds1 helps to enforce the replication checkpoint. Proteins that regulate the onset of mitosis will be evaluated as targets of Cds1. The second aim is to understand how Cds1 is regulated. Mechanisms that activate Cds1 and cause it to phosphorylate its substrates will be investigated. The third aim is to uncover the mechanism that restricts nuclear localization of Cds1 to the DNA synthesis (S) phase of the cell cycle. These studies will improve the understanding of Cds1 as an important element of checkpoint mechanisms in fission yeast and will provide a framework for investigating the functions of homologous proteins in humans.