Cross-links At Abasic Sites in Duplex DNA

描述（由申请人提供）：来自双链体DNA中非碱性位点的交联。 在癌症研究和环境毒理学中，一个重要的正在进行的奋进涉及鉴定重要的DNA损伤病变和表征其诱导细胞凋亡的能力。 死亡或致癌突变。拟议的工作将表征一个新的家庭的DNA损伤，来自脱嘌呤/脱碱基（AP）位点的双链体DNA。AP位点由多种过程产生，并且可能是细胞DNA所持续的最常见类型的损伤。该建议建立在我们最近的观察基础上，即AP位点可以通过与双螺旋相对链上的核碱基反应产生链间DNA-DNA交联。令人惊讶的是，AP位点可以产生链间交联，这通常被认为是所有DNA损伤中最有害的。交联对人类细胞中的DNA修复机制提出了特殊的挑战。交联的修复可能是容易出错的，并且遗传密码中产生的突变可能导致自发性和化学诱导的癌症的病因。如果不修复，交联可能会阻止DNA转录和复制。对这些交联的细胞反应的确切性质可能受到个体基因组成的影响，特别是关于其DNA损伤反应和修复机制中的缺陷或多态性。拟议的工作是重要的，因为它将表征交联如何有助于内源性或化学诱导的脱碱基位点的倾向，导致诱变，癌症，细胞功能障碍，衰老和人类衰老。我们的研究代表了第一次努力来表征这些最近发现的DNA损伤的形成和生物学后果。拟议的工作将：（目的1和2）表征双链体DNA中两种不同AP衍生的交联的形成和化学结构，（目的3）使用质谱方法定量测量暴露于诱导AP位点的试剂（包括辐解和临床使用的烷化剂）的人细胞中AP衍生的交联的形成和修复，和（目的4）评估转录旁路、复制，和使用穿梭载体方法修复人细胞中的dG-AP交联。

DESCRIPTION (provided by applicant): Cross-links From Abasic Sites in Duplex DNA. A significant ongoing endeavor in cancer research and environmental toxicology involves the identification of important DNA-damage lesions and characterization of their ability to induce cell death or cancer-causing mutations. The proposed work will characterize a novel family of DNA lesions that are derived from apurinic/abasic (AP) sites in duplex DNA. AP sites are generated by a wide variety of processes and may be the most common type of damage sustained by cellular DNA. This proposal builds upon our recent observations that AP sites can generate interstrand DNA-DNA cross-links via reactions with nucleobases on the opposing strand of the double helix. It is striking that AP sites can generate interstrand cross-links, which generally ar thought to be the most deleterious of all DNA lesions. Cross-links present an exceptional challenge to the DNA-repair machinery in human cells. The repair of cross-links may be error- prone and the resulting mutations in the genetic code could contribute to the etiology of both spontaneous and chemical-induced cancers. Left unrepaired, cross-links may block DNA transcription and replication. The exact nature of the cellular response(s) to these cross-links may be influenced by an individual's genetic makeup, especially with regard to defects or polymorphisms in their DNA damage response and repair machinery. The proposed work is significant because it will characterize how cross-links contribute to the propensity for endogenous or chemically-induced abasic sites to cause mutagenesis, cancer, cell dysfunction, senescence, and aging in humans. Our studies represent the first efforts to characterize the formation and biological consequences of these recently discovered DNA lesions. The proposed work will: (Aims 1 and 2) characterize the formation and chemical structures of two different AP-derived cross-links in duplex DNA, (Aim 3) use mass spectrometric methods to quantitatively measure the formation and repair of AP-derived cross-links in human cells exposed to agents that induce AP sites, including radiolysis and clinically-used alkylating agents and, (Aim 4) assess transcriptional bypass, replication, and repair of the dG-AP cross- link in human cells using a shuttle-vector methodology.