Deletions in plasmid pBR322: replication slippage involving leading and lagging strands.
Deletions in plasmid pBR322: replication slippage involving leading and lagging strands.
复制标题
质粒 pBR322 中的缺失：涉及前导链和滞后链的复制滑移。
DOI：
10.1093/genetics/127.4.649
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发表时间：
1991
期刊：
影响因子：
3.3
通讯作者：
Berg,DE
中科院分区：
文献类型：
--
作者：
Weston-Hafer,K;Berg,DE
我们在这里测试是否有一类删除可能导致的错误在DNA复制过程中出现优先在合成的领导或落后的DNA链。通过逆转pBR 322 amp基因的特定插入突变等位基因获得缺失。等位基因含有插入的回文DNA，由9-bp的amp序列的直接重复包围;此外，回文的一个臂中的bp 2至5与相邻的amp序列的4 bp形成直接重复。先前的工作表明，回复到Ampr的结果是在8或4 bp重复序列中具有端点的缺失，并且优先使用4 bp重复序列，因为其中一个在回文中。为了测试前导链和滞后链合成在缺失形成中的作用，我们通过反转pBR 322复制起点来逆转amp基因的复制方向，并且还构建了具有逆时针而不是顺时针插入的4-bp重复序列的新的突变等位基因。在这两种情况下，优先使用4-bp重复序列作为缺失终点。一个模型中出现的缺失在延长的链，复制回文序列之前，相邻的4-bp重复序列，并在其中优先使用的4-bp重复序列独立的整体方向复制意味着，缺失出现在合成的领先和落后的链。
We test here whether a class of deletions likely to result from errors during DNA replication arise preferentially during synthesis of either the leading or the lagging DNA strand. Deletions were obtained by reversion of particular insertion mutant alleles of the pBR322 amp gene. The alleles contain insertions of palindromic DNAs bracketed by 9-bp direct repeats of amp sequence; in addition, bp 2 to 5 in one arm of the palindrome form a direct repeat with 4 bp of adjoining amp sequence. Prior work had shown that reversion to Ampr results from deletions with endpoints in the 8- or 4-bp repeat, and that the 4-bp repeats are used preferentially because one of them is in the palindrome. To test the role of leading and lagging strand synthesis in deletion formation, we reversed the direction of replication of the amp gene by inverting the pBR322 replication origin, and also constructed new mutant alleles with a 4-bp repeat starting counterclockwise rather than clockwise of the insertion. In both cases the 4-bp repeats were used preferentially as deletion endpoints. A model is presented in which deletions arise during elongation of the strand that copies the palindrome before the adjoining 4-bp repeat, and in which preferential use of the 4-bp repeats independent of the overall direction of replication implies that deletions arise during syntheses of both leading and lagging strands.