Molecular Mechanism for Maintainance of Genetic Information

本研究的目的是分析包括人类在内的高等真核生物遗传信息维持的分子机制，并分析其在胚胎发生、发育、衰老和致癌中的作用。本研究的主要成果如下：第一组：从原核生物、袋鼠大鼠、黑腹果蝇和金鱼中克隆了嘧啶二聚体和（6-4）光产物的光裂解酶基因。这些光解酶基因的人类同源基因也已被克隆，其功能分析正在进行中。我们克隆了色素干皮病A、C和G组的基因，并分析了它们在核苷酸切除修复的早期阶段的作用及其缺陷的分子基础。三种DNA修复蛋白的高阶结构已被x射线晶体学揭示。第二组：我们阐明了PCNA和DNA聚合酶β基因表达的调控机制。我们克隆了一个错配修复基因MSH3，发现在RER阳性的白血病细胞中，MSH3基因的表达减少。结果表明，氧胁迫、吸烟和老化等处理均能提高8-OH-Gua修复酶的活性。第三组：采用小鼠ES细胞基因靶向的方法，建立xpa -缺陷或xpg -缺陷小鼠，o6 -甲基鸟嘌呤- dna -甲基转移酶缺陷或8-氧- dgtpase缺陷小鼠。我们还建立了rad51缺陷小鼠，这些小鼠在胚胎期死亡。xpa缺乏小鼠对uvb诱导的皮肤癌非常敏感。基于这些结果，我们认为我们已经完成了重要DNA修复基因的分子克隆、DNA修复蛋白的x射线晶体学结构分析和基因靶向构建DNA修复基因缺陷小鼠等初步研究项目。这些成果为突破揭示遗传信息维持的分子机制奠定了基础。少

The aim of this research is to analyze a molecular mechanism for maintainance of genetic information in higher eukaryotes including human and to analyze its role in embryogenesis, development, aging and carcinogenesis. Major achievements in this research are as follows. Group I : We cloned genes of photolyases for pyrimidine dimer and (6-4) photoproduct from prokaryotes, kangaroo rat, drosophila melanogaster, and goldfish. Human homologue of these photolyase genes has been cloned as well and functional analysis of the human homologue is in progress. We cloned the genes responsible for xeroderma pigmentosum groups A,C,and G,and analyzed their roles in the early steps of nucleotide excision repair and molecular basis of their deficiencies. Higher order structures of the three DNA repair proteins have been revealed by X-ray crystallography. Group II : We elucidated the control mechanisms of gene expression for PCNA and DNA polymerase beta. We cloned a mismatch repair gene MSH3 and found t … More hat the expression of the MSH3 gene was reduced in the leukemic cells which were RER positive. We found that the enzyme activity to repair 8-OH-Gua damage caused by the active oxygen was increased by the treatment with oxygen stress, smoking and aging. Group III : By the method of gene targeting in mouse ES cells, we established XPA-deficient or XPG-deficient mice, and O6-methylguanine-DNA-methyltransferase-deficient or 8-oxo-dGTPase-deficient mice. We also established RAD51-deficient mice which were lethal at the embryonal stage. The XPA-deficient mice were highly susceptible to UVB-induced skin carcinogenesis. Based on these results we concluded that we have accomplished the initial research projects such as molecular cloning of the important DNA repair genes, structural analysis of DNA repair proteins by X-ray crystallography and establishment of DNA repair gene-deficient mice by gene targeting. These achievements provide a basis for the breakthrough to unveiling the molecular mechanism for maintainance of genetic information. Less