DNA MISMATCH REPAIR AND CANCER IN MURINE MODELS

描述：这项研究的目的是研究 错配修复蛋白MSH3和MSH6与癌症易感性突变 在hMSH2基因中导致HNPCC。因为MSH3和MSH6被认为形成了 MSH2的功能复合体，预测基因敲除小鼠在 这些基因很容易罹患癌症。我们对这个问题的大部分理解 哺乳动物DNA错配修复系统的特性源于 大肠杆菌MutHLS系统的生化研究在细菌中 修复DNA错配是DNA复制错误的结果， 由MutS蛋白与不匹配的碱基结合而启动。在……里面 真核生物DNA错配的识别更加复杂，需要 三种不同MutS同源物的子集：MSH2、MSH3和MSH6。研究项目： 酵母菌已经表明DNA错配修复是由两个不同的 络合物：识别单一碱基的MSH2-MSH6络合物 错配和MSH2-MSH3之间的复合体用于识别两个TO 四个碱基对的插入/缺失。因为hMSH2的种系突变 导致HNPCC很可能是与hMSH2相互作用的hMSH3和hMSH6， 也参与了肿瘤的发展。他们在这些事件中的角色 然而，事件仍不清楚。在本提案中，我们计划测试 假设酵母MSH3和MSH6的哺乳动物同源物是相同的 有丝分裂错配修复中的作用及肿瘤易感性分析 携带这些基因的靶向突变的小鼠。三个具体目标 这一建议是：1.培育MSH3和MSH6缺乏的小鼠 并研究这些小鼠系对癌症的敏感性。埃德尔曼博士 将研究MSH3和MSH6缺失对癌症的影响 易感性，特别强调胃肠道癌症的发生。2. 为了检验哺乳动物的msh2、msh3和msh6基因是 在基因上等同于它们的酵母同源物。在酵母中的实验 提示MSH2-MSH3和MSH2-MSH6参与了不同基因的修复 DNA错配的类型。我们将使用msh2、msh3和msh6突变小鼠品系。 和双突变msh3/msh6小鼠品系作为小鼠胚胎的来源 成纤维细胞系分析微卫星不稳定性并测量 细胞提取液中的异源双链错配修复。3.检视 APC抑癌基因MSH2、MSH3和MSH6缺失。结直肠 HMSH2基因突变的癌细胞株在体内积累突变 肿瘤抑制基因APC。我们将产生突变的小鼠品系 Msh3或msh6，A1638等位基因杂合子。对中国传统文化的分析与思考 肿瘤谱与肿瘤形成的发生和发展 指出MSH2、MSH3和MSH6对胃肠道的意义 肿瘤发生，并提供突变谱的详细分析 这是由于这些修复基因中的每一个都缺乏所致。

DESCRIPTION: The purpose of this study is to examine the role of the mismatch repair proteins MSH3 and MSH6 in cancer susceptibility. Mutations in the hMSH2 gene lead to HNPCC. Since MSH3 and MSH6 are thought to form functional complexes with MSH2, the prediction is that knockout mice in these genes will be cancer prone. Most of our understanding of the properties of the mammalian DNA mismatch repair system is derived from biochemical studies of the Escherichia coli MutHLS system. In bacteria the repair of DNA mismatches, which are the result of DNA replication errors, is initiated by the binding of the MutS protein to the mismatched bases. In eukaryotes the recognition of DNA mismatches is more complex and requires subsets of three different MutS homologs: MSH2, MSH3 and MSH6. Studies in yeast have indicated the DNA mismatch repair is initiated by two different complexes: A complex between MSH2-MSH6 for the recognition of single base mismatches and a complex between MSH2-MSH3 for the recognition of two to four base pair insertion/deletions. Because germline mutations in hMSH2 lead to HNPCC it is likely that hMSH3 and hMSH6, which interact with hMSH2, are also involved in the development of neoplasms. Their role in these events, however, remains unclear. In this proposal we plan to test the hypothesis that the mammalian homologs of yeast MSH3 and MSH6 share the same function in mitotic mismatch repair and to analyze the cancer susceptibility of mice carrying targeted mutations in these genes. The 3 specific aims of this proposal are: 1. To generate mice that are deficient in MSH3 and MSH6 and to study the cancer susceptibility of these mouse lines. Dr. Edelmann will study the consequences of loss of MSH3 and MSH6 for cancer susceptibility with special emphasis on gastrointestinal carcinogenesis. 2. To test the hypothesis that the mammalian msh2, msh3 and msh 6 genes are genetically equivalent to their yeast homologs. Experiments in yeast suggest the MSH2-MSH3 and MSH2-MSH6 are involved in the repair of different types of DNA mismatches. We will use msh2, msh3 and msh6 mutant mouse lines and double mutant msh3/msh6 mouse lines as a source for mouse embryonic fibroblast cell lines to analyze microsatellite instability and to measure heteroduplex mismatch repair in cell extracts. 3. To examine the effect of MSH2, MSH3 and MSH6 deficiency of the Apc tumor suppressor gene. Colorectal cancer cell lines with mutations in the hMSH2 gene accumulate mutations in the tumor suppressor gene APC. We will generate mouse lines that are mutant for msh3 or msh6 and heterozygous for the A1638 allele. The analysis of the tumor spectrum and the onset and progression of tumor formation will indicate the significance of MSH2, MSH3 and MSH6 for gastrointestinal tumorigenesis and provide a detailed analysis of the spectrum of mutations that results from deficiency in each of these repair genes.