中文摘要：

Rdr1是出芽酵母Saccharomyces cerevisiae的一个转录抑制因子,参与控制细胞的多重药物耐受性,并可能与细胞胁迫应答相关.利用PCR方法扩增RDR1基因片段,将其克隆至高拷贝表达载体pYES2/NTA上并诱导Rdr1蛋白在酵母细胞中过表达.为了揭示转录抑制因子Rdr1在胁迫应答中的作用,比较了RDR1过表达细胞、RDR1缺失突变体细胞和野生型细胞在过氧化氢处理、热胁迫和高盐处理条件下的生长状态,结果显示,RDR1过表达导致细胞对上述3种胁迫作用更敏感,而RDR1缺失则使细胞对这些胁迫作用的耐受性不受影响或有一定增强.为了揭示上述不同细胞在胁迫条件下生长状态的差异与细胞内抗氧化酶活性之间的关系,测定并比较了RDR1过表达细胞、RDR1缺失突变体细胞和野生型细胞中超氧化物岐化酶（superoxide dismutase SOD）、过氧化氢酶、葡萄糖-6-磷酸脱氢酶（glucose-6-phosphate dehydrogenase G6PDH）、谷胱甘肽还原酶（glutathione reductase GR）的活性.结果表明,RDR1缺失突变体细胞具高活性的SOD、过氧化氢酶、G6PDH和GR,而Rdr1过表达细胞中SOD、过氧化氢酶、G6PDH和GR的活性较低．RDR1对SOD和过氧化氢酶活性的影响要大于G6PDH和GR．细胞抗氧化酶活性的变化初步揭示，RDR1过表达细胞对胁迫的敏感和RDR1缺失突变体细胞对胁迫耐受性增加的原因．为转录抑制因子Rdr1在胁迫应答中的负调控作用及其机理提供了初步的遗传学和生物化学证据．

英文摘要：

The study of signal transduction and gene expression regulation in yeast cells has contributed to understand the fundamental principle and molecular mechanism of cellular processes in higher eukaryotes. Rdrl is a transcriptional repressor in budding yeast Saccharomyces cerevisiae, which was supposed to control pleiotropic drug resistance of cell and probably regulate genes involved in stress response. It still lacks enough evidence to conclude that Rdrl involves in stress response. RDR1 gene was cloned by PCR and ligated into multicopy vector pYES2/NTA resulting an overexpression plasmid pYES2/NTA-RDR1. The overexpression of Rdrl protein was induced by 2% galactose to achieve a gain-of-function phenotype. In order to reveal the function of transcription repressor Rdrl in stress response, the growth state of wild type cells, cells with overexpressed Rdrl protein and RDR1 mutant cells under H2O2, heat-shock and salt stress treatments were compared. The data demonstrated that cells with overexpressed Rdrl protein were hypersensitive to above three stress treatments, while RDR1 mutant cells were equal or more tolerant to theses stress treatments compared to wild type cells. Yeast cells elevate antioxidant enzymes activity when challenged with different stressors. The role of RDR1 in stress response may relate to its regulation of antioxidant enzymes activity. To verify this hypothesis, the activities of antioxidant enzymes including superoxide dismutase （SOD）, catalase, glucose-6-phosphate dehydrogenase （G6PDH）, glutathione reductase （GR） were measured. It was showed that RDR1 mutant cells had higher activities of SOD, catalase, G6PDH and GR compared to wild type cells, while cells with overexpressed Rdrl protein had lower activities of SOD, catalase, G6PDH and GR. The negative effect of RDR1 on activities of SOD and catalase was more intense than it on activities of G6PDH and GR. The results might explain the phenomenon that overexpressed Rdrl protein were hypersensitive to above three stress treatments,