DNA REPAIR AND REPLICATION RE START IN VIVO

遗传不稳定性是一种主要的细胞事件， 癌症、肿瘤进展和对化疗药物的抗性。 涉及的染色体变化包括同源染色体之间的体细胞重组 染色体，促进杂合性丢失，易位之间 非同源染色体，基因扩增和其他DNA重排， 除了突变。这些不同形式的遗传不稳定性是由 DNA修复事件。许多与遗传有关的人类蛋白质 不稳定性在真细菌中具有类似物， 其中许多参与DNA修复，包括双链修复 断裂（DSB）和单链缺口。引起病变的药物， 需要修复的主要致癌物质，人类遗传性疾病，其中 细菌修复蛋白的同源物被改变，显示出癌症倾向。 尽管基因重排和DNA复制被认为是 单独的事件，并已分别研究，许多线的最近 来自几种生物的证据现在暗示了一种深刻的联系--促进 双链DNA断裂修复（DSBR）仅在一个 细胞（非病毒）系统是否有这种联系， 证明：DSBR在E.大肠杆菌大约有一半的时间发生在 复制促进事件，另一半通过重组， 复制的本文对DSBR在大肠杆菌中的分子机理进行了初步探讨。杆菌 以阐明DNA结构为目标，研究了一个模型系统 过程中的中间体和产品，识别所有相关的 参与的蛋白质，以及理解复制与 非复制机制。这些信息将与遗传有关。 在癌症中的不稳定性，以及在某些情况下，E.杆菌 还将检查修复蛋白。因为DNA的直接物理分析， 以及复杂的遗传工具，在这个模型系统中， 要获得的分子机制的详细程度在其他方法中是无与伦比的。 有机体因为目前鉴定的蛋白质与人类同源， 癌蛋白（例如Blm、Gln、hRad 51，其与Brca蛋白一起发挥作用， DSBR），它们的功能是保守的，信息是直接 适用于遗传不稳定的机制，导致，促进， 产生抗药性的人类癌症。

Genetic instability is a primary cellular event leading to cancers, tumor progression, and resistance to chemotherapeutic drugs. Chromosomal changes involved include somatic recombination between homologous chromosomes, promoting loss of heterozygosity, translocations between non-homologous chromosomes, gene amplification, and other DNA rearrangements in addition to mutation. These various forms of genetic instability are provoked by DNA repair events. Many of the human proteins implicated in genetic instability have homologs in eubacteria which appear to function similarly, many of which participate in DNA repair including repair of double-strand breaks (DSBs) and single-strand gaps. Agents that cause the lesions that require repair are primary carcinogens, and human genetic diseases in which homologs of the bacterial repair proteins are altered display cancer-proneness. Although genetic rearrangements and DNA replication have been thought of as separate events, and have been studied separately, many lines of recent evidence from several organisms now imply a profound connection--the promotion of DNA replication by double-strand DNA break-repair (DSBR). In only one cellular (non-viral) system has this connection been firmly and directly demonstrated: DSBR in E. coli occurs roughly half the time as a replication-promoting event, and the other half via recombination without replication. In this proposal the molecular mechanism of DSBR in the E. coli model system is investigated with the goals of elucidating structures of DNA intermediates in and products of the process, identifying all of the relevant proteins involved, and understanding control of replicative versus non-replicative mechanisms. This information will be related to genetic instability in cancer, and, in some cases, the human orthologs of E. coli repair proteins will also be examined. Because direct physical analysis of DNA, as well as sophisticated genetic tools are available in this model system, the level of detail of molecular mechanism to be obtained is unparalleled in other organisms. Because the proteins so far identified are homologous with human cancer proteins (e.g. Blm, Wrn, hRad51 which functions with Brca proteins in DSBR), and their functions are conserved, the information is directly applicable to the mechanisms of genetic instability that cause, promote, and make drug-resistant, human cancers.