MUTAGENESIS AND ITS CONTROL IN E COLI

拟议研究的长期目标是从分子水平了解 生物体的突变率是如何定义的， 速率响应于环境诱变剂而增加。 的 菌E.选择大肠杆菌来研究这些问题是因为 它提供了一个相对简单的实验系统， 遗传和生物化学方法。 赠款的具体目的是 学习：（1）定义保真度或DNA的酶机制 复制;（2）诱导SOS反应的调节和范围 损害，其中包括增加突变率和增强能力的DNA 修复. 复制保真度的工作最初将集中在一个生化 分析聚合酶III全酶的α和σ亚基， 似乎是正常复制准确性的主要决定因素 在大肠杆菌 3'到5'的贡献和可能的调节 外切核酸酶（编辑功能）将受到特别关注。 SOS研究 反应将寻求定义：（i）DNA损伤的分子信号， 启动SOS反应;（ii）增加的生化基础， （三）在其他方面的SOS响应的范围 遗传变异的类型，如转座和复制。 一个 了解突变率及其控制可能与以下方面有关： 对癌症起始事件的理解。 许多代理商， 动物体内的致癌物质激活细菌的SOS反应。 癌症可能 通常来源于体细胞中SOS样系统的异常激活， 细胞，其正常目的是在生殖细胞中诱导遗传变异 细胞

The long term goal of the proposed research is a molecular understanding of how the mutation rate of an organism is defined and how this basal mutation rate is increased in response to environmental mutagenic agents. The bacterium E. coli has been chosen for the study of these questions because it provides a relatively simple experimental system amenable to combined genetic and biochemical approaches. Specific aims of the grant are to learn: (1) enzymatic mechanisms that define the fidelity or DNA replication; (2) regulation and scope of the induced SOS response to DNA damage, which includes increased mutation rate and enhanced capacity for DNA repair. Work on replication fidelity will focus initially on a biochemical analysis of the alpha and sigma subnits of polymerase III holoenzyme, which appear to be the primary determinants for the accuracy of normal replication in E. coli. The contribution and possible regulation of the 3' to 5' exonuclease (editing function) will be of special concern. Study of the SOS response will seek to define: (i) the molecular signal of DNA damage that initiates the SOS response; (ii) the biochemical basis for the increase in replication errors; (iii) the scope of the SOS response in terms of other types of genetic variation, such as transposition and duplication. An understanding of mutation rate and its control is likely to be pertinent for an understanding of initiating events in cancer. Many agents that are carcinogenic in animals activate the SOS response in bacteria. Cancer might often derive from the aberrant activation of an SOS-like system in somatic cells, the normal purpose of which is inducible genetic variation in germ cells.