Roles of LIG3 and XRCC1 genes in genome stability.

描述(申请人提供)：人类基因组经常受到内源性和环境DNA损害剂的攻击。如果不修复，DNA损伤将产生突变，进而可能导致癌症形成。DNA修复通路的复杂网络可以移除DNA损伤。为了准确评估暴露于环境DNA损伤剂的生物学意义，有必要了解复杂细胞对DNA损伤反应的分子细节。虽然原核生物和低等真核生物已被证明是高等生物有用的模式系统，但DNA反应的某些方面，包括似乎仅限于高等真核生物的DNA修复途径。例如，低等真核生物缺乏编码DNA连接酶III、XRCC1、聚(ADPribose)聚合酶-1(PARP-1)和DNA聚合酶β的基因的同源性。所有这些蛋白质都与DNA碱基切除修复和DNA单链断裂修复有关。这项资助的目的是阐明LIG3和XRCC1基因产物在维持哺乳动物细胞基因组稳定性方面的作用。在初步研究中，PARP-1和hRAD50/Mre11/NBS复合体已被确定为体细胞中DNA连接酶III-α的伙伴。此外，DNA连接酶III-α被证明以一种依赖于细胞周期的方式被磷酸化，并在DNA损伤时被去磷酸化。在这些结果的基础上，提出了四个目标：(I)描述DNA连接酶III-α与PARP-1相互作用的功能和生物学后果；(Ii)阐明DNA连接酶III-α与Mre11复合体相互作用的功能和生物学后果；(Iii)表征DNA连接酶III-α的细胞周期调节和DNA损伤依赖的修饰；(Iv)通过建立LIG3突变细胞系和动物来确定LIG3基因产物的细胞功能。这些研究将为更复杂的生物体所特有的DNA交易提供新的见解，并将有助于全面了解DNA修复机制如何保护DNA免受暴露于遗传毒性环境制剂所致的DNA损伤和突变。

DESCRIPTION (provided by applicant): The human genome is subject to constant attack by endogenous and environmental DNA damaging agents. If unrepaired, DNA lesions will give rise to mutations that in turn may lead to cancer formation. A complex network of DNA repair pathways operates to remove DNA lesions. In order to accurately assess the biological significance of exposure to environmental DNA damaging agents, it is necessary to understand the molecular details of the complex cellular response to DNA damage. Although prokaryotes and lower eukaryotes have proven to be useful model systems for higher organisms, there are aspects of the DNA response, including DNA repair pathways that appear to be restricted to higher eukaryotes. For example, lower eukaryotes lack homologs of the genes encoding DNA ligase III, XRCC1, poly (ADPribose) polymerase-1 (PARP-1) and DNA polymerase beta. All of these proteins have been implicated in DNA base excision repair and the repair of DNA single-strand breaks. The goal of this grant is to elucidate the roles of the LIG3 and XRCC1 gene products in maintaining genome stability in mammalian cells. In preliminary studies, PARP-1 and the hRAD50/Mre11/Nbs complex have been identified as partners of DNA ligase III-alpha in somatic cells. In addition, DNA ligase III-alpha has been shown to be phosphorylated in a cell-cycle dependent manner and dephosphorylated in response to DNA damage. On the basis of these results, 4 aims are proposed: (i) to delineate the functional and biological consequences of the interaction between DNA ligase III-alpha and PARP-1; (ii) to elucidate the functional and biological consequences of the interaction between DNA ligase III-alpha and the MRE11 complex; (iii) to characterize cell cycle-regulated and DNA damage-dependent modifications of DNA ligase III-alpha; (iv) to determine the cellular functions of the LIG3 gene products by generating lig3 mutant cell lines and animals. These studies will provide novel insights into DNA transactions that are unique to more complex organisms and will contribute to an overall picture of how DNA repair mechanisms protect against DNA damage and mutations induced by exposure to genotoxic environmental agents.