CONTROL OF DNA REPLICATION AND CELL DIVISION

该研究计划的长期目标是调查如何 细胞测量 DNA 复制的状态以维持时间 细胞周期的顺序。 在正常的细胞周期中，进入有丝分裂是 取决于 S 阶段的完成，这种依赖性是 由称为检查点控制的控制机制维护。 酵母的遗传学研究表明，一旦细胞退出 G1 期， 通过START，细胞将进入S期和有丝分裂。 复制复合体的存在向细胞发出信号：它处于 S 状态 阶段并抑制细胞过早进入有丝分裂； 随后复制复合物的分解然后激活 有丝分裂的开始。 我们建议使用裂殖酵母作为模式生物 DNA聚合酶α和δ以及PCNA作为探针 研究哪些基因产物产生信号或感知并传输 启动或停止时抑制细胞进入有丝分裂的信号 由于这些复制之一存在缺陷，复制受到阻碍 酶或蛋白质。 具体目标是： (I) 表征面板 无法抑制细胞过早进入有丝分裂的突变体 由于 DNA 半残疾，S 期进展被延迟 聚合酶δ。 (II) 识别检测起始缺陷的基因 由半失能的 DNA 聚合酶 α 引起，以阻止细胞 来自过早的有丝分裂进入。 (III) 确定 PCNA 的等位基因 参与S期进展，并分离和表征基因 与这些等位基因相互作用的产品。 这些研究将为进一步了解 细胞周期检查点机制。 从裂变中获得的知识 酵母研究将来可以应用于人类细胞，因此将 有助于对分子病因学的基本了解 瘤形成。

The long-term goal of this research program is to investigate how a cell gauges the status of DNA replication to maintain the temporal order of the cell cycle. In a normal cell cycle, entry into mitosis is dependent upon the completion of S phase and this dependency is maintained by a control mechanism termed checkpoint control. Genetic studies of yeast have suggested that once cells exit G1 and pass START, cells are committed to enter both S phase and mitosis. The presence of a replication complex signals the cell that it is in S phase and restrains the cell from entering mitosis prematurely; subsequent disassembly of the replication complex then activates the onset of mitosis. We propose to use fission yeast as a model organism and DNA polymerases alpha and delta and PCNA as probes to investigate what gene products generate a signal or sense and transmit a signal to restrain cells from entering mitosis when initiation or replication is faltered due to defects in one of these replication enzymes or protein. The specific aims are: (I) Characterize a panel of mutants that fail to restrain cells from premature mitotic entry when S-phase progression is delayed due to a semi-disabled DNA polymerase delta. (II) Identify genes that detect the initiation defects caused by a semi-disabled DNA polymerase alpha to prevent cells from premature mitotic entry. (III) Identify alleles of PCNA that are involved in S phase progression, and isolate and characterize gene products that interact with these alleles. These studies will provide a foundation for further understanding of cell cycle checkpoint mechanisms. Knowledge gained from the fission yeast studies can be applied to human cells in the future, and thus will contribute to the basic understanding of the molecular etiology of neoplasia.