BIOCHEMISTRY AND RADIATION EFFECT DURING THE CELL CYCLE

本项目的总体目标是调查 过程E.大肠杆菌细胞，特别是关于启动和 染色体DNA的复制，细胞分裂的控制和过程， 以及DNA复制与细胞分裂之间的协调 周期 因为决定启动频率的机制 是细胞周期中的关键调节步骤， 关于控制染色体起源oriC起始的研究， 重点介绍 研究计划分为两个基本领域： 生理学研究，旨在确定协调 染色体复制与细胞生长周期在体内，并在体外 oricC指导的DNA复制的分子生物学研究。 许多 的项目在体内和体外将采用各种 微型染色体，即，从一个居民身上复制的小DNA分子 oricC的副本。 具体的项目有：1）确定是否选时 启动染色体复制的E.大肠杆菌可以被调控 所需活动综合体的组成部分 入会仪式 最近的发现导致了一种实验性的发展， 这一战略将使这个问题得到回答。 将 确定，例如，是否明显缺乏再利用 在oricC处引发的引发复合物是 体内调节系统。 2)比较的复制属性 质粒驱动的染色体与oricC驱动的染色体，以确定 oricC起源复合体是否具有生长的独特性质 耦合启动频率调节器。 3)为了表征 单个蛋白质的合成、细胞内容物、稳定性和分离 已知与起始和/或复制相关。 实验 计划将这些发现与阳性的预测性质联系起来， 监管要素。 第二组实验涉及比较 体外和体内微型染色体DNA复制的分析。 的 在复制过程中，染色体通过中间体进行分裂， 沿着对拓扑要求的分析， 复制的 在复制早期形成的分子种类， 将详细检查体外和体内。

The overall objective of this project is to investigate the duplication process of E. coli cells with particular regard to the initiation and replication of chromosomal DNA, the control and process of cel division, and the coordination between DNA replication and the celllar division cycle. Since the mechanisms which determines the frequency of initiation of chromosome replication is a key regulatory step in the cell cycle, studies on the control of initiation from the chromosomal origin, oriC, are emphasized. The research plan is divided into two basic areas: physiological studies aimed at identifying the elements which coordinate chromosome replication with the cellular growth cycle in vivo, and in vitro studies on the molecular biology of oricC-directed DNA replication. Many of the projects in vivo and in vitro will employ a variety of minichromosomes, i.e., small DNA molecules which replicate from a resident copy of oricC. The specific projects are: 1) To determine if the timing of initiation of chromosome replication in E. coli could be regulated positively by components of the complex of activities required for initiation. Recent findings have led to the development of an experimental strategy which will enable this question to be answered. It will be determined, for instance, whether the apparent absence of reutilization of initiation complexes for initiation at oricC is the basis for the regulatory system in vivo. 2) To compare replication properties of plasmid-driven chromosomes with oricC-driven chromosomes to determine whether the oricC origin-complex possesses unique properties of a growth coupled initiation frequency regulator. 3) To characterize the kinetics of synthesis, cellular content, stability and segretion of individual proteins known to be associated with initiation and/or replication. Experiments are planned to relate these findings to the prediced properties of positive regulatory elements. The second series of experiments involves comparative analyses of minichromosome DNA replication in vitro and in vivo. The intermediates through which mninchromosomes progess during replication will be determined, along with an analysis of topological requirements for replication. The molecular species which form early during replication in vitro and in vivo will be examined in detail.