IONIZING RADIATION INDUCED DNA DAMAGE AND REPAIR

这个项目的目标是增加我们对如何 电离辐射会导致癌症、突变和细胞死亡， 阐明哺乳动物X射线的酶学和遗传学， 诱导DNA修复。 一种直接的方法， X射线诱导DNA修复酶的人类遗传学 修复被描述。 该项目将定义的一级结构和遗传 修复电离损伤所需的人和牛的酶 辐射引起的DNA损伤 牛组织（小牛胸腺）将 用作制备均相酶的来源， 氨基酸测序和抗体生产。 的cDNA 编码修复酶的序列选自λ 用兔抗酶免疫筛选gt11文库 抗体或来自λ gt10文库，通过用混合的 寡核苷酸 一旦牛酶的cDNA 所获得的人cDNA将选自λ gt10或 λ gt11文库通过其核酸同源性或 免疫交叉反应性。 已选择脱嘌呤核酸内切酶作为 在本程序中克隆的原因如下：1）脱嘌呤位点 已知DNA中存在致突变性（可能致癌）2） 脱嘌呤位点对于许多类型的DNA损伤是常见的， 修复包括X射线3）是否一个单一的基因或 多个哺乳动物基因编码AP核酸内切酶， （4）对这种方法的要求已经 满足a）均质酶B）氨基酸序列数据c） 抗体探针和d）来源组织的cDNA文库， 都可以 X射线酶的一级结构知识 诱导的DNA修复将有助于理解这种 酶识别受损的DNA， 修复以及修复失败如何导致生物 X射线的影响。 这些分子探针的可用性 基因将允许研究它们在遗传缺陷中的作用， DNA修复如共济失调与毛细血管扩张症的易感性 个体和肿瘤对X射线的影响。

The goal of this project is to increase our understanding of how ionizing radiation causes cancer, mutation and cell death by elucidating the enzymology and genetics of mammalian X-ray- induced DNA repair. A direct approach for the development of human genetics for the enzymes of repair of X-ray-induced DNA repair is described. This project will define the primary structure and genetics of human and bovine enzymes required for repair of ionizing radiation-induced DNA damage. Bovine tissue (calf thymus) will be used as a source of preparation of homogeneous enzymes for amino acid sequencing and antibody production. The cDNA sequences coding for repair enzymes will be selected from lambda gt11 libraries by immunoscreening with rabbit anti-enzyme antibodies or from lambda gt10 libraries by screening with mixed oligonucleotides. Once the cDNA for the bovine enzyme is obtained the human cDNA will be selected from lambda gt10 or lambda gt11 libraries through its nucleic acid homology or immunologic cross reactivity, respectively. Apurinic endonuclease has been chosen as the initial target for cloning in this program for the following reasons; 1) Apurinic sites in DNA are known to mutagenic (and possibly carcinogenic) 2) apurinic sites are common to many types of DNA damage and repair including X-rays 3) the issue of whether a single gene or multiple mammalian genes code for AP endonuclease is unresolved 4) the requirements for this approach have been fulfilled a) homogeneous enzyme b) amino-acid sequence data c) antibody probes and d) cDNA libraries for the tissue of origin are all available. Knowledge of the primary structure of the enzymes of X-ray induced DNA repair will be useful in understanding how such enzymes recognize damaged DNA, the sequence of events during repair and how failures of repair might lead to the biological effects of X-rays. The availability of molecular probes for these genes will allow studies of their role in the inherited defects of DNA repair such as ataxia telangiectasia and in the susceptibility of individuals and tumors to X-rays effects.