MECHANISM OF DELETION MUTAGENESIS

缺失诱变机制

• 批准号: 2190453
• 负责人: SUSAN THOMAS LOVETT
• 金额: $ 12.49万
• 依托单位: BRANDEIS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2190453
• 关键词: DNA repair; Escherichia coli; bacterial genetics; dimer; gene deletion mutation; gene frequency; genetic crossing over; genetic strain; mutant; nucleic acid repetitive sequence; plasmids; pyrimidine dimers; recombinase

DESCRIPTION: Sequence analysis of deletion mutations in both E. coli and humans has shown that deletions occur most frequently between short repeated sequences. Models to explain this observation have been of two main types: recombinational (unequal crossing over) and replicational (strand slippage or misalignment). There has been a tendency to discount recombinational mechanisms because deletion mutations in E. coli lack two traditional hallmarks of homologous recombination: the repeated sequences are very often much shorter than necessary to serve as a substrate for RecA protein, and the deletions occur quite readily in RecA deletion strains, in which conventional recombination is eliminated. Recent work by Dr. Lovett using a plasmid-based system for monitoring deletions has shown, unexpectedly, that RecA-independent deletion formation can have unmistakable recombinational features, most notably, deletion-associated plasmid dimerization. On the basis of this and related observations, Dr. Lovett has proposed a mechanism for deletion formation initiated by RecA-independent pairing between nascent strands in the vicinity of an arrested replication fork to form a Holiday junction, followed by processing by other enzymes associated with homologous recombination reactions. Dr. Lovett furthermore proposes that the same mechanism may apply to recombinational "postreplication" repair observed on damaged DNA templates, whose mechanism has been obscure. In this application, Dr. Lovett proposes to continue her study on the mechanism of deletion formation and its relationship to recombinational DNA repair and sister strand exchange (plasmid dimerization) in E. coli. The proposed work has two broad components. In one component, Dr. Lovett will analyze the effect of single DNA lesions (thymine dimers) on the occurrence of deletions and plasmid dimerization.Using variations of this basic idea, she will examine if a thymine dimer has different effects when placed in the leading vs. lagging strand vs. both together; when placed in different locations relative to the tandemly repeated sequences that are recombining; and when processed in strains with mutations in various components of recombination or replication. In the other part of the investigation, Dr. Lovett will define the genetics of recA-independent deletion formation by examining the effects of known components of replication and recombination on deletion formation, and by searching for novel genes that affect the frequency of deletion formation.

描述：大肠杆菌中缺失突变的序列分析 人类已经表明删除最常发生在短之间 重复序列。 解释这一观察的模型是两个 主要类型：重组（不平等越过）和复制 （链条打滑或错位）。 有一个趋势 折扣重组机制，因为大肠杆菌的缺失突变 缺乏两个传统的同源重组标志：重复 序列通常比用作用作的序列要短得多 RECA蛋白的底物，缺失很容易出现 RECA缺失菌株，其中常规重组是 淘汰。 Lovett博士的最新工作使用基于质粒的系统 监视缺失已出乎意料地表明 删除形成可以具有明确的重组特征，大多数 值得注意的是，缺失相关的质粒二聚化。 基于此 和相关的观察，洛维特博士提出了一种机制 删除形成由新生之间的独立配对引发 被捕的复制叉附近的链形成了A 节日交界处，然后是与其他酶相关的处理 与同源重组反应。 洛维特博士 提出相同的机制可能适用于重组 在受损的DNA模板上观察到的“后放置”修复 机制是晦涩的。 在此应用程序中，洛维特​​博士建议继续学习 缺失形成的机制及其与重组的关系 大肠杆菌中的DNA修复和姐妹链交换（质粒二聚化）。 拟议的工作有两个广泛的组成部分。 在一个组件中，博士 Lovett将分析单个DNA病变（胸腺胺）的影响 关于缺失和质粒二聚化的发生。 在这个基本思想中，她将检查胸腺二二聚体是否不同 效果将效果放在领先的滞后链与滞后链中与两者一起； 当放置在不同位置相对于串联重复的位置时 重组的序列； 当与 重组或复制各个组成部分中的突变。 在 调查的其他部分，洛维特博士将定义 通过检查已知的效果，独立于RECA的缺失形成 关于缺失形成的复制和重组的组成部分，以及 通过寻找影响缺失频率的新基因 形成。