"Mechanisms of Damage-Induced Homologous Recombination"

每次细胞分裂时，数十亿个碱基对的信息必须在面对一个 DNA损伤的冲击。同源重组（HR）提供了耐受和 修复受损的DNA虽然人力资源通常是有益的，人力资源过程中的失调可能会导致 致瘤序列重排。尽管其基本的重要性，很少有人知道HR在体内， 主要是因为检测HR的技术困难。 其中荧光重组细胞可以在完整胰腺组织内直接检测到的动物， 首次这项技术突破使得评估基因和环境 因子调节重组细胞随时间的积累。胰腺癌是第四大 胰腺癌的危险因素包括慢性炎症和暴露于 烷化剂，已知这两种物质均诱导通过碱基切除修复的受损碱基 修复（BER）途径。在上一个资助周期中，我们发现未修复的病变和下游 BER中间体在体外可诱导HR。在这里，我们建议进行有史以来第一次研究， BER对在体胰腺组织HR影响特别是，我们将集中在Aag DNA糖基化酶， 其去除了广泛的病变，包括许多由烷基化损伤产生的病变， 炎症化学物质。我们的假设是BER底物和中间体诱导HR， 损伤的影响会因慢性炎症或炎症诱导的 促有丝分裂刺激在DNA损伤方面，我们将关注通常由Aag修复的DNA损伤， 下游BER中间体。我们的具体目标是I）揭示Aag底物或下游BER 中间体调节体内自发或烷基化诱导的重组; II）研究 慢性胰腺炎症和胰腺诱导的体内细胞分裂的重组作用;和 III）确定炎症或促有丝分裂刺激是否调节DNA损伤对HR的影响或改变 重组细胞在体内克隆扩增的程度。这项工作的长期目标是 为了阐明影响一个人对自发性， 环境诱导的和癌症治疗诱导的DNA序列重排。

Every time a cell divides, billions of base pairs of information must be accurately copied in the face of an onslaught of DNA damage. Homologous recombination (HR) provides a critical mechanism for tolerating and repairing damaged DNA. Although HR is generally beneficial, misalignments during HR can lead to tumorigenic sequence rearrangements. Despite its fundamental importance, little is known about HR in vivo, primarily because of technical difficulties associated with detecting HR. We have recently created transgenic animals in which fluorescent recombinant cells can be directly detected within intact pancreatic tissue for the first time. This technological breakthrough makes it possible to assess how genetic and environmental factors modulate the accumulation of recombinant cells over time. Pancreatic cancer is the fourth leading cause of cancer death, and risk factors for pancreatic cancer include chronic inflammation and exposure to alkylating agents, both of which are known to induce damaged bases that are repaired by the base excision repair (BER) pathway. In the previous grant cycle, we found that both unrepaired lesions and downstream BER intermediates can induce HR in vitro. Here, we propose to undertake the first ever studies of the influence of BER on HR in pancreatic tissue in vivo. In particular, we will focus on the Aag DNA glycosylase, which removes a broad range of lesions, including many that are created by alkylation damage and inflammatory chemicals. Our hypothesis is that BER substrates and intermediates induce HR, and that the effects of damage are exacerbated by conditions of chronic inflammation or by hormonally-induced mitogenic stimulation. In terms of DNA damage, we will focus on DNA lesions normally repaired by Aag, and on downstream BER intermediates. Our Specific Aims are I) Reveal if Aag substrates or downstream BER intermediates modulate spontaneous or alkylation-induced recombination in vivo; II) Study the potential recombinogenic effects of chronic pancreatic inflammation and hormonally induced cell division in vivo; and III) Determine if inflammation or mitogenic stimulation modulates the effects of DNA damage on HR or alters the extent of clonal expansion of recombinant cells in vivo. The broad long term objectives of this work are to shed light on the molecular and cellular processes that influence a person's susceptibility to spontaneous, environmentally-induced, and cancer therapy-induced DNA sequence rearrangements.