DNA Replication Fidelity and Cancer

描述（由申请人提供）：正常细胞以高保真度复制其基因组（大约10-10个突变/nt/复制周期）。这是通过聚合酶碱基选择性、外切核校对（exo）、错配校正和DNA损伤修复的联合作用来实现的。我们最近在DNA聚合酶d （Pold）的3‘- bbb50 ’核外溶校对结构域创建了一个失活点突变（Pold1D400A）的“敲入”小鼠，并表明纯合突变体发展出独特的早发性上皮肿瘤谱（皮肤和肺，但不包括肠）。在这里，我们建议使用这些新的Pol delta外显小鼠和衍生细胞系来表征Pol delta校对在维持哺乳动物遗传稳定性和避免癌症方面的作用。具体目标是：

DESCRIPTION (provided by applicant): Normal cells replicate their genomes with high fidelity (approximately 10-10 mutations/nt/replication cycle). This is achieved through the combined actions of polymerase base selectivity, exonucleolytic proofreading (exo), mismatch correction and DNA damage repair. We recently created "knock-in" mice with an inactivating point mutation (Pold1D400A) in the 3'-->5' exonucleolytic proofreading domain of DNA polymerase d (Pol d) and showed that homozygous mutants develop a unique spectrum of early-onset epithelial tumors (skin and lung, but not intestine). Here we propose to use these novel Pol delta exo-mice and derivative cell lines to characterize the role of Pol delta proofreading in the maintenance of genetic stability and avoidance of cancer in mammals. The specific aims are: 1. Characterize the mutator phenotype of Pol delta exo-cells and mice. To ascertain the extent and nature of the mutator phenotype conferred by loss of Pol delta proofreading, we will determine rates, frequencies and spectra of spontaneous mutations arising in Poldelta1D400A cells in culture and tissues in vivo. 2. Examine cooperativity of Pol delta proofreading with mismatch repair (MMR). Mice and cells carrying combinations of Pol delta proofreading and MMR alleles will be studied to assess how these error correction systems cooperate in mammals at the phenotypic level (survival, mutator and cancer phenotypes). Together, these studies will significantly contribute to our understanding of mutator phenotypes in cancer and will characterize the contribution of Pol delta proofreading to mutation- and cancer-avoidance in mammals.