Dna2在DNA核苷酸切除修复途径中的作用研究

The DNA in cells is constantly insulted by DNA-damaging agents produced either in the external environment or intracellularly as by-products of oxidative metabolism. If not correctly fixed, these DNA errors will often cause cell senescence, cell death or tumorigenesis. There are three different DNA damage repair pathways: nucleotide excision repair (NER), base excision repair (BER) and miss match repair. The NER pathway is the most versatile mechanism of DNA repair, recognizing and dealing with a variety of helix-distorting lesions. There are three sequential steps of the eukaryotic NER mechanism, from lesion recognition to damage removal and DNA synthesis. Mutations of NER proteins can cause severe human diseases, and increase the susceptibility to carcinogenesis. .Our group demonstrates for the first time that the DNA helicase and nuclease protein Dna2 is a component of the NER pathway. Loss of Dna2 function will lead cells sensitive to MMS. In this project, we will further study the molecular mechanism of Dna2 in the NRE pathway. This will contribute significantly to our understanding of how the NER pathway works and will provide a new path for our understanding to cancer development.

细胞中的DNA不断受到内外源因素的攻击而被损伤，如不及时准确的修复，将引起细胞衰老、凋亡或者因为基因组不稳定而发生癌变。DNA损伤修复方式包括核苷酸切除修复（NER）、碱基切除修复（BER）和错配修复（MMR）等。其中核苷酸切除修复是最主要的修复手段，可以识别并修复多种DNA损伤类型。DNA核苷酸切除修复途径包括DNA损伤的识别、损伤核苷酸的切除、以为损伤链为模板重新合成DNA等步骤。如果NER修复途径相关蛋白的基因突变，将会导致多种严重的人类疾病，大大提高皮肤癌的发病率。.本项目首次证明Dna2蛋白参与DNA核苷酸切除修复途径，Dna2功能缺陷导致细胞对MMS敏感。我们将进一步深入研究Dna2参与NER途径的分子机制，这将大大增加我们对DNA核苷酸切除修复分子机理的理解，并对今后研究癌症等疾病的发生发展提供新的研究方向。

细胞中的DNA不断受到内外源因素的攻击而被损伤，如不及时准确的修复，将引起细胞衰老、凋亡或者因为基因组不稳定而发生癌变。DNA损伤修复方式包括核苷酸切除修复（NER）、碱基切除修复（BER）和错配修复（MMR）等。其中核苷酸切除修复是最主要的修复手段，可以识别并修复多种DNA损伤类型。DNA核苷酸切除修复途径包括DNA损伤的识别、损伤核苷酸的切除、以为损伤链为模板重新合成DNA等步骤。如果NER修复途径相关蛋白的基因突变，将会导致多种严重的人类疾病，大大提高皮肤癌的发病率。本项目首次证明Dna2蛋白参与DNA核苷酸切除修复途径，Dna2功能缺陷导致细胞对低剂量MMS敏感，其分子机制正在阐明。我们还通过电镜、遗传及生化等手段，首次证明真核细胞DNA复制后随链冈崎片段的RNA-DNA primer 是通过形成翘起结构（flap）而被移除的，并且证明Fen1和Dna2 直接参与了该翘起结构的移除过程。全面阐明了真核细胞DNA复制过程中后随链冈崎片段加工成熟的分子机制。