MECHANISMS OF MISTRANSLATION MEDIATED MUTATOR RESPONSE

描述：本提案描述了旨在描述 翻译和DNA复制之间可能存在联系。调查员已经 获得了初步证据表明有一种可诱导的突变反应 称为翻译应激诱导突变(TSM)。他发现， MutA和MutC突变基因的反密码子有碱基替换 允许突变的tRNA对天冬氨酸进行译码的lyV或lyW tRNA基因 作为甘氨酸的密码子。突变子的表型是结构性的， 研究人员认为，这种表型不是由于稀有的甘氨酸造成的 DNA聚合酶3的epsilon校对亚基的替换 此外，表型依赖于recA，但不需要功能性 UmuD/C基因。工作假说是该通路是RecA依赖的 但独立于SOS，是对翻译压力的反应，而不是 这是误译本身造成的。可能与epsilon蛋白有关，但 MUTA细胞中的关键事件位于epsilon亚基的上游。Dr。 胡马云建议开展三套实验，以进一步 描述TSM响应的特征。第一组实验将测试 假设翻译应激而不是特定的氨基酸 特定蛋白质中的替换(S)诱导TSM并将定义 引起TSM的平移应力条件的范围。第二套 实验将确定翻译应激是否会改变DNA 通过比较诱导和诱导的DNA复制活性来实现复制保真度 体外系统中的未诱导细胞。第三个项目将以 TSM反应与umuD/C依赖的SOS通路有何不同。

DESCRIPTION: This proposal describes approaches designed to characterize a putative link between translation and DNA replication. The investigator has obtained preliminary evidence that there is an inducible mutagenic response called translational stress-induced mutagenesis (TSM). He found that the mutA and mutC mutator genes have a base substitution in the anticodons of the glyV or glyW tRNA genes that allow the mutant tRNAs to decode aspartate codons as glycine. The mutator phenotype is constitutive and the investigator argues that the phenotype is not due to rare glycine substitutions in the epsilon proofreading subunit of DNA polymerase III. In addition, the phenotype is recA-dependent but does not require functional umuD/C genes. The working hypothesis is that the pathway is recA-dependent but SOS-independent and is a response to translational stress rather than a result of mistranslation itself. The epsilon protein could be involved but the critical events in mutA cells are upstream of the epsilon subunit. Dr. Humayun proposes to carry-out three sets of experiments to further characterize the TSM response. The first set of experiments will test the hypothesis that translational stress rather than a specific amino acid substitution in a particular protein(s) induces TSM and will define the range of translational stress conditions that induce TSM. The second set of experiments will determine if translational stress will alter DNA replication fidelity by comparing DNA replication activities in induced and uninduced cells in an in vitro system. The third project will characterize how the TSM response differs from the umuD/C-dependent SOS pathway.