RELATIONSHIP OF THE DAM GENE AND DNA ADENINE METHYLASE

DNA腺嘌呤甲基化酶是大肠杆菌dam基因所特有的。大肠杆菌中， 在自发突变中。 自发变异性大幅增加 如果这种酶不存在或过度产生。 这构成了两个 问题：（i）dam基因是如何调控的？（二）什么是 过量产生酶或不产生酶的细胞中的突变谱 生产的所有？ 这项建议旨在通过一项 结合体外和体内方法。 体外操作和 体内产生的突变将用于鉴定启动子， 控制dam基因表达的其它调节元件。 在 体内产生的小阻遏物基因突变将通过在 体外DNA测序以在核苷酸水平鉴定突变。 一个 光谱分析将检验甲基化依赖的模型 错配修复是去除潜在移码的主要机制 突变。 这项建议也试图确定哪些基因的E。杆菌 可以通过DNA甲基化改变它们的表达。 会来做这项工作 在存在或不存在DNA腺嘌呤的情况下检查融合基因的表达 甲基化酶 DNA腺嘌呤甲基化酶在DNA修复中的作用研究 和E.大肠杆菌模型系统提供了一种新的方法， 阐明突变的起源和维持，因此， 有助于更全面地了解这一过程 将致癌作用与人类先天性异常联系起来。

The DNA adenine methylase, specified by the dam gene of E. coli, has a role in spontaneous mutability. Spontaneous mutability increases substantially if the enzyme is absent or if it is overproduced. This poses two questions: (i) How is the dam gene regulated?, and (ii) What is the mutation spectrum in cells overproducing the enzyme or in which it is not produced at all? This proposal seeks to answer these questions through a combined in vitro and in vivo approach. In vitro manipulations and mutations generated in vivo will be used to identify the promoter(s) and other regulatory elements which control the expression of the dam gene. In vivo generated mutations in a small repressor gene will be analyzed by in vitro DNA sequencing to identify mutations at the nucleotide level. An analysis of the spectrum will test the model that methylation dependent mismatch repair is a major mechanism for removal of potential frameshift mutations. This proposal also seeks to determine which genes of E. coli can have their expression altered by DNA methylation. This will be done by examing expression of fused genes in the presence or absence of DNA adenine methylase. The studies with DNA adenine methylase function in DNA repair and gene expression in the E. coli model systems offers a new approach to the elucidation of the origin and maintenance of mutations and, thus, may contribute significantly to a more thorough understanding of the process linking carcinogenesis and spontaneous congenital abnormalities in man.