Slipped misalignment mechanisms of deletion formation: Analysis of deletion endpoints
Slipped misalignment mechanisms of deletion formation: Analysis of deletion endpoints
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DOI：
10.1006/jmbi.1997.1566
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发表时间：
1998-02-27
影响因子：
5.6
通讯作者：
Lovett, ST
中科院分区：
文献类型：
--
作者：
Feschenko, VV;Lovett, ST
为了深入了解串联重复序列之间缺失形成的机制，研究人员对大肠杆菌质粒进行了工程改造，使其在tetA基因内携带一个101 bp的串联重复序列，这样，其中一个重复序列的缺失可以恢复完整的tetA基因和对细胞的四环素抗性。在一个串联重复序列中引入四个碱基对变化作为遗传标记。选择缺失后，对单个质粒产物进行测序，以推断重复序列中缺失发生的位置。我们的分析表明，大多数缺失是两个重复序列在单个20bp间隔内的融合。这与缺失形成的简单复制滑移对模型是一致的，并表明这个间隔可能具有促进缺失的不寻常特征。二聚体复制子产物除了缺失外，还经历了姐妹染色体交换事件，并携带两个tetA位点：一个被删除的位点与单体产物中端点分布相似，另一个重复位点不变。表面上相互作用的二聚体偶尔会被恢复，它们同时携带一个缺失的和一个三倍的tetA位点。这些并不是真正的相互作用，因为序列分析表明，删除和复制发生在不同的时间间隔。二聚体产物的序列分析与我们的姐妹链交换模型的预测一致，其中新生DNA链的滑移排列诱导了伴随姐妹染色体交换的缺失形成。(C) 1998学术出版社有限公司
To gain insight into the mechanisms of deletion formation between tandem repeats, Escherichia coli plasmids were engineered to carry a 101 bp tandem duplication within the tetA gene such that deletion of one of the repeats restores an intact tetA gene and tetracycline resistance to the cell. Four base-pair changes were introduced into one of the tandem repeats to serve as genetic markers. After selection for deletion, individual plasmid products were sequenced to deduce where within the repeat the deletion had occurred. Our analysis shows most deletions are fusions of the two repeats in a single 20 bp interval. This is consistent with the simple replication slip-pair model for deletion formation and suggests that this interval may have unusual features that promote deletion. Dimer replicon products have experienced a sister-chromosome exchange event in addition to deletion and carry two tetA loci: a deleted locus showing a similar distribution of endpoints as seen in the monomer products and an unchanged repeat locus. Seemingly reciprocal dimers are occasionally recovered which carry both a deleted and a triplicated tetA locus. These are not truly reciprocal in that the sequence analysis showed that the deletion and triplication had occurred in separate intervals. Sequence analysis of the dimeric products is consistent with predictions from our sister-strand exchange model where slipped alignment of nascent DNA strands induces-deletion formation concomitant with sister-chromosome exchange. (C) 1998 Academic Press Limited.