MECHANISMS OF DNA REPAIR IN ACTIVE GENES

描述：本提案的总体目标是了解 细胞用来消除DNA损伤的分子机制。精挑细选 从转录的活性基因链中去除DNA损伤，称为 转录偶联核苷酸切除修复(TCNR)，可能是普遍存在的 已经清楚地证明了它可以去除紫外线 诱导的环丁烷嘧啶二聚体。这项研究的重点是 描述了其机制、普遍性和生物学后果 转录偶联修复。对E.Coli的研究之所以被重点报道，是因为 我们用来识别所需基因的突变体的可用性 在这个过程中。研究人员将继续研究大肠杆菌中的TCNR和 将通过检测人类细胞中的TCNR来补充这些研究。 将采取的方法包括：(1)确定组件如何 错配修复影响核苷酸切除修复。Coli使用 遗传和生化方法。研究潜在的生物化学 错配修复的组成部分和错配修复的组成部分之间的相互作用 核苷酸切除修复，我们将尝试建立一个系统，其中 我们可以在体外研究TCNR在E.Coli中的表达。(2)确定突变在 人类错配修复基因对环丁烷嘧啶脱除的影响 肿瘤细胞系和淋巴母细胞系中DHFR基因的二聚体 来自遗传性非息肉病性结直肠癌(HNPCC)患者。如果 人类错配修复基因的突变也取消了转录偶联 修复，那么肿瘤的病因与错配突变有关 修复基因可能受核苷酸切除修复缺陷的影响 和碱基切除修复，除了错配的不足 更正。(3)研究人员还将尝试确定 E.β亚基编码基因突变的机制 Coli RNA聚合酶显著减少核苷酸切除修复 非转录DNA。这些突变体长得很像人类干皮病 C组细胞色素沉着。

DESCRIPTION: The broad objective of this proposal is to understand the molecular mechanisms cells use for removing DNA damage. The selective removal of DNA damage from the transcribed strands of active genes, termed transcription-coupled nucleotide excision repair (TCNR), may be ubiquitous and has been clearly demonstrated for the removal of ultraviolet light induced cyclobutane pyrimidine dimers. This research is focused on characterizing the mechanism, generality and biological consequences of transcription-coupled repair. Studies in E. Coli have been featured because of the availability of mutants that we have used to identify genes required for the process. The researchers will continue to study TCNR in E. Coli and will complement these studies with the examination of TCNR in human cells. Approaches to be taken include the following: (1) Determine how components of mismatch repair influence nucleotide excision repair inE. Coli using genetic and biochemical approaches. To study the potential biochemical interactions between components of mismatch repair and components of nucleotide excision repair, we will attempt to establish a system in which we can study TCNR in E. Coli in vitro. (2) Establish that mutations in human mismatch repair genes influence the removal of cyclobutane pyrimidine dimers from the DHFR gene in tumor cell lines and lymphoblastoid cell lines from patients with hereditary nonpolyposis colorectal carcinoma (HNPCC). If mutations in human mismatch repair genes also abolish transcription-coupled repair, then the etiology of tumors associated with mutations in mismatch repair genes may be influenced by deficiencies in nucleotide excision repair and base excision repair, in addition to the deficiency in mismatch correction. (3) The researchers will also attempt to determine the mechanism by which mutations in the gene encoding the beta subunit of the E. Coli RNA polymerase dramatically reduce nucleotide excision repair in nontranscribed DNA. These mutants pheontypically resemble human xeroderma pigmentosum group C cell lines.