Novel Mechanism & Developmental Roles of Repair・Recombination

DNA解旋酶Q1是我们在人类细胞中发现的大肠杆菌DNA解旋酶RecQ的人类同源物。RecQ同源物在人细胞中的存在表明真核细胞存在一个涉及真核RecQ的DNA修复-重组系统。在这项研究中，我们打算阐明真核RecQ在新的DNA修复-重组系统中的功能，以及在酵母、小鼠和苍蝇的发育过程中利用Sgs1基因干扰物对酵母RecQ （Sgs1）基因的功能分析以人DNA解旋酶Q1 cDNA为探针克隆酵母RecQ基因，发现克隆的基因与酿酒酵母拓扑异构酶III突变体生长缓慢表型的抑制基因Sgs1相同。我们分析了SGS1基因干扰物对各种遗传毒性物质的敏感性。与野生型细胞相比，干扰物对甲基磺酸甲酯、甲基磺酸乙酯（MMS）和羟基脲（HU）等烷基化剂的敏感性更高。当纯合子SGS1干扰物转移到产孢培养基时，观察到产孢不良和减数分裂重组频率降低。此外，将野生型细胞用MMS处理或转移到孢子培养基中诱导减数分裂时，观察到SGS1 mRNA的表达诱导。这些结果表明，Sgs1参与了某些类型DNA损伤的修复和减数分裂DNA重组。2小鼠DNA解旋酶Q1的cDNA克隆及Q1 mrna的表达分析我们克隆了一个编码小鼠DNA解旋酶Q1的cDNA，并检测了Q1信息在小鼠各组织中的表达。mRNA在睾丸中表达量最高，胸腺中表达量较高，在脑、心、肾、肝、肺、肌肉、卵巢和脾脏中表达量较低。出生后监测睾丸中Q1 mRNA的表达，出生后第14天观察到mRNA水平升高，颧线和粗线细胞增加，发生DNA重组。3 Dorosophila DNA解旋酶Q1 cDNA的克隆我们成功地分离到了一个Dorosophila DNA解旋酶Q1 cDNA。然而，Q1在转基因果蝇发育过程中的作用有待进一步研究。少

DNA helicase Q1 is a human homologue of the Escherichia coli DNA helicase RecQ,which we found in human cells. The existence of a RecQ homologue in human cells indicated that eukaryotic cells had a DNA repair-recombination system involving eukaryotic RecQ.In this study, we intended to clarify functions of eukaryoric RecQ in the novel DNA repair-recombination system and in the process of development using yeast, mouse, and fly.1 Analysis of the function of yeast RecQ (Sgs1) with SGS1 gene disruptantsWe cloned a yeast RecQ gene by using human DNA helicase Q1 cDNA as a probe and found that the cloned gene was identical to SGS1 which was cloned as a suppresser of the slow growth phenotype of topoisomerase III mutants of Saccharomyces cerevisiae. We analyzed the sensitivity of SGS1 gene disruptants to various genotoxic agents. Disruptants showed higher sensitivity to alkylating agents such as methy methanesulfonate and ethyl methanesulfonate (MMS) and hydroxyurea (HU) as compared with wild-t … More ype cells. When homozygous SGS1 disruptants were transferred to sporulation medium, poor sporulation and a reduced frequency of meiotic recombination were observed. In addition, the induction of expression of SGS1 mRNA was observed when wild-type cells were treated with MMS or transferred to sporulation medium to induce meiosis. These results indicates that Sgs1 is involved in the repair of some type of DNA lesions and meiotic DNA recombination.2 cDNA cloning of mouse DNA helicase Q1 and analysis of expression of Q1 mRNAWe cloned a cDNA encoding mouse DNA helicase Q1 and examined expression of Q1 message in various mouse tissues. The mRNA was expressed in the highest level in testis, a higher level in thymus and was poorly expressed in brain, heart, kidney, liver, lung, muscle, ovary, and spleen. When the expression of Q1 mRNA in testis was monitored after birth, an increase in the level of the mRNA was observed 14th day after birth when cells in zygotene and pachytene increased, in which DNA recombination took place.3 cDNA cloning of Dorosophila DNA helicase Q1We have succeeded to isolate a Dorosophila DNA helicase Q1 cDNA.However, the analysis of roles of Q1 during development by making transgenic flies has remained for future study. Less