MECHANISMS OF CHEMICAL CARCINOGEN INDUCED P53 MUTATIONS

环境致癌物对DNA的损伤被认为是一个原则 基因突变和癌症发展的诱导因素， 人类 p53肿瘤抑制基因是最常见的突变基因 在人类恶性肿瘤中。 一个流行的假设是， 在不同癌症中发现的突变可能带有 诱变过程 为了验证这一假设，我们将进行一项 详细分析了p53基因座的诱变过程， 体外系统 作为这个方向的第一步，我们将在不同的细胞中进行研究， 在关键的p53外显子上的染色质结构类型，包括 核小体结合和DNA结合蛋白的分析。 为了了解诱变的机制，我们将分析DNA损伤 和DNA序列水平上的DNA修复事件 几种不同的诱变剂和致癌物。 我们将应用 连接介导的聚合酶链反应（LMPCR），一种独特敏感的 DNA加合物的体内作图技术，以确定频率 在每个核苷酸位置上有许多不同的诱变DNA加合物 p53基因第五到第九个外显子 选定DNA的修复率 分析加合物以确定修复是否是序列特异性的。 一个 在特定条件下，加合物频率增加和/或修复率降低 核苷酸位置可以产生突变热点。 染色质结构分析数据，序列依赖性加合物 频率图和修复率将与公布的 在各种人类癌症中发现的突变体的频率， 因为怀疑与环境致癌物有关。 因此 我们将尝试提供体外模型系统来研究基本的 导致p53基因突变的分子机制。

Damage of DNA by environmental carcinogens is assumed to be a principle factor in the induction of mutations and the development of cancer in humans. The p53 tumor suppressor gene is the most frequently mutated gene in human malignancies. One popular hypothesis is that the spectrum of mutations found in different cancers may bear the signature of the mutagenesis process. To test this hypothesis, we will undertake a detailed analysis of the mutagenesis process at the p53 locus using in vitro systems. As a first step in this direction, we will investigate in different cell types the chromatin structure at the critical p53 exons including an analysis of nucleosome association and DNA binding proteins. To understand the mechanisms of mutagenesis, we will analyze DNA damage and DNA repair events at the DNA sequence level in human cells treated with several different mutagens and carcinogens. We will apply the ligation-mediated polymerase chain reaction (LMPCR), a uniquely sensitive technique for in vivo mapping of DNA adducts, to determine the frequency of a number of different mutagenic DNA adducts at each nucleotide position of the p53 gene's exons five through nine. Repair rates for selected DNA adducts will analyzed to determine if repair is sequence-specific. An increased adduct frequency and/or decreased repair rates at specific nucleotide positions may create mutation hot spots. Data from analysis of chromatin structure, sequence-dependent adduct frequency maps, and repair rates will be compared with published frequencies of mutants found in a variety of human cancers including those for with involvement of an environmental carcinogen is suspected . Thus we will attempt to provide in vitro model systems to study the basic molecular mechanism that give rise to mutations in the p53 gene.