Mechanisms of mistranslation-mediated mutator response

误译介导的突变反应机制

• 批准号: 6873088
• 负责人: M. ZAFRI HUMAYUN
• 金额: $ 28.49万
• 依托单位: UNIV OF MED/DENT OF NJ-NJ MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6873088
• 关键词: DNA damage; DNA directed DNA polymerase; DNA replication; bacteriophage T4; beta lactamase; enzyme mechanism; gene mutation; genetic recombination; genetic regulation; genetic translation; phenotype; posttranslational modifications; streptomycin; tissue /cell culture; transfer RNA

DESCRIPTION (provided by applicant): Mutations play critical roles in cancer initiation and genetic disorders, as well as in microbial pathogenesis and resistance to drugs. Because mutations also generate genetic variability that is required for evolution, cells have mechanisms not only for avoiding excess mutation during normal growth conditions, but also for promoting mutations in response to environmental and physiological stress. In this proposal we will investigate of a recently discovered pathway for mutagenesis that was found to be triggered, surprisingly, by a mutation (mutA) in a gene coding for a tRNA. Our investigation in the previous funding period has led to several important discoveries: mistranslation induced by genetic defects in protein synthesis, or exposure to the antibiotic streptomycin, can induce this mutagenic pathway, named TSM for translational stress-induced mutagenesis. TSM is distinct from the well known SOS mutagenesis pathway, and appears to require homologous recombination functions under certain conditions. TSM appears to be mediated by error-prone DMA synthesis by a modified form of DMA polymerase III. These findings imply the existence of previously undescribed links between translation and DMA replication, and raise the possibility that mutator phenotypes with significance for cell survival, adaptation, cancer initiation, and aging can arise through defects in a much larger repertoire of target genes than previously recognized. The induction of this pathway by antibiotic exposure, and potentially by amino acid starvation suggest that environmental and physiological stress can also increase mutagenesis by this pathway. Our work further shows that aminoglycoside antibiotics pose a mutagenic risk through this previously unrecognized mechanism. Here, we propose to investigate the mechanisms by which mistranslation leads this mutator phenotype through the following three Specific Aims. (1) Test the hypothesis that direct mistranslation of a replicative DMA polymerase leads to the TSM phenotype. (2) Test the hypothesis that in Rec- mutA cells there is selective killing of cells undergoing episodic aberrant replication cycles. (3) Test the hypothesis that the TSM phenotype results from episodic hyper-mutagenesis cycles.

描述(由申请人提供)：突变在癌症的发生和遗传紊乱中起关键作用，也在微生物发病机制和药物耐药性中发挥关键作用。由于突变还会产生进化所需的遗传变异性，因此细胞不仅有机制避免在正常生长条件下过度突变，而且还有机制促进突变以应对环境和生理压力。在这个提案中，我们将调查最近发现的一条突变途径，令人惊讶的是，该途径被发现是由编码tRNA的基因的突变(Muta)触发的。我们在前一个资助期的研究已经导致了几个重要的发现：蛋白质合成中的遗传缺陷引起的翻译错误，或者接触抗生素链霉素，都可以诱导这种突变途径，称为TSM，即翻译应激诱导突变。TSM不同于众所周知的SOS突变途径，在某些条件下似乎需要同源重组功能。TSM似乎是由一种修改形式的DMA聚合酶III容易错误地合成DMA所介导的。这些发现暗示了翻译和DMA复制之间存在先前未描述的联系，并提出了一种可能性，即对细胞存活、适应、癌症启动和衰老具有重要意义的突变体表型可能是通过比先前认识的更大的靶基因库中的缺陷而产生的。通过抗生素暴露和潜在的氨基酸饥饿诱导的这一途径表明，环境和生理应激也可以通过这一途径增加突变。我们的工作进一步表明，氨基糖苷类抗生素通过这一以前未知的机制构成了突变风险。在这里，我们建议通过以下三个具体目标来研究误翻译导致这种突变子表型的机制。(1)验证复制的DMA聚合酶的直接错误翻译导致TSM表型的假设。(2)验证在Rec-Muta细胞中存在选择性杀伤经历周期性异常复制周期的细胞的假设。(3)验证TSM表型是间歇性超突变周期的结果的假设。