MOLECULAR CLONING OF A RADIATION REPAIR GENE XRCC5

真核生物对DNA损伤剂的反应，如电离 辐射，是由各种DNA修复的有效性决定的 系统. 缺陷修复，表现为 准确的维修或通过不准确的维修过程，可能会导致 涉及控制细胞增殖的基因的突变 增殖理解这些修复过程的本质是 核心的阐明机制，通过随后的 对健康的不利影响，如突变、胎儿畸形和癌症 表达了。电离辐射可诱导多种类型的DNA损伤， 哺乳动物细胞包括DNA单链断裂（SSB），DNA双链断裂 链断裂（DSB），DNA-蛋白质交联，DNA-DNA链间 交联和改变的DNA碱基虽然-很明显，人类 细胞可以修复许多这些病变，但很少有详细的知识 基因和控制这些基因的编码酶的性质 修复过程。 为了了解DNA修复是如何调节 辐射敏感性、癌基因表达和重组相关 遗传疾病，辐射特异性DNA修复基因必须被分离出来 和表征了 在本项目的当前供资期间， 定位克隆人的战略和所有基本依据 DSB修复基因XRCC 5已在本实验室建立。 因此 这次更新申请的主要目的是继续我们的努力， 人XRCC 5基因的分离和鉴定。 具体 目的：1）XRCC 5基因在2号染色体上的区域定位， 2）建造一个修复能力强的X射线混合体 图，每个杂交体含有人2号染色体的片段（1-3 Mb） 3）候选XRCC 5的位置克隆 重组克隆和这些克隆的功能分析; 克隆的XRCC 5基因的表征。 我们认为，这一步- 利用先进分子遗传技术逐步方法将 基本上有利于第一次人体辐射修复的隔离 负责电离辐射诱导的DNA重新连接的基因 双链断裂

The response of eukaryotes to DNA damaging agents, such as ionizing radiation, is determined by the effectiveness of a variety of DNA repair systems. Defective repair, in the form of a diminished capacity for accurate repair or through inaccurate repair processes, can lead to mutations involving genes responsible for the control of cell proliferation. Understanding the nature of these repair processes is central to the elucidation of the mechanisms through which subsequent adverse health effects such as mutations, fetal malformations, and cancers are expressed. Ionizing radiation induces various types of DNA damage in mammalian cells including DNA single-strand breaks (SSB), DNA double strand breaks (DSB), DNA-protein crosslinks, DNA-DNA interstrand crosslinks, and altered DNA bases. Although- it is obvious that human cells can repair many of these lesions, there is little detailed knowledge of the nature of the genes and the encoded enzymes that control these repair processes. ln order to understand how DNA repair modulates radiation sensitivity, oncogene expression, and recombination-related genetic diseases, radiation-specific DNA repair genes have to be isolated and characterized. During the current funding period of this project, a comprehensive strategy and all the basic grounds for the positional cloning of a human DSB repair gene XRCC5 have been established in our laboratory. Thus, the primary objective of this renewal application is to continue our efforts on the isolation and characterization of human XRCC5 gene. The specific aims are: 1) Regional localization of human XRCC5 gene in chromosome 2 (at the megabases level); 2) Construction of a repair-proficient X-ray hybrid panel, each hybrid containing a fragment of human chromosome 2 (1-3 Mb) where the XRCC5 has been assigned ;3) Position cloning of candidate XRCC5 recombinant clones and functional analysis of these clones; 4) Molecular characterization of the cloned XRCC5 gene. We believe that this step-by- step approach utilizing advanced molecular genetic technologies will substantially facilitate the isolation of the first human radiation repair gene(s) responsible for the rejoining of ionizing radiation-induced DNA double-strand breaks.