Saing K M, Orii H, Tanaka Y, Yanagisawa K, Miura A, Ikeda H
Institute of Biological Sciences, University of Tsukuba, Ibaraki, Japan.
Mol Gen Genet. 1988 Sep;214(1):1-5. doi: 10.1007/BF00340170.
We constructed a recombinant plasmid containing the 2.1 kb HindIII fragment of plasmid pDG1, isolated from the cellular slime mold (Dictyostelium sp. strain GA11), and using pAG60 as cloning vector. We found that deletions of the recombinant plasmid took place frequently in Escherichia coli wild-type cells. However, the deletion was not observed when the plasmid was introduced into a strain that was an isogenic temperature-sensitive mutant of the gyrA gene. These results suggest that E. coli DNA gyrase is involved in the mechanisms of the deletion formation. It was shown that the 1.0 kb deletant derived from the 2.1 kb HindIII insert was produced by elimination of a 1.1 kb region. Sequence analysis of the deletants showed that cutting and rejoining took place between two out of the six nearly perfect direct repeats [21 bp palindromic sequences; AAAAAA(T/C)GGC(G/C)GCC(A/G)TTTTTT], located near the distal ends of the inverted repeats, preserving one copy of the repeats. These sequences consist of local short inverted repeats, where cutting and rejoining occur at one of the two regions.
我们构建了一个重组质粒，该质粒包含从细胞黏菌（盘基网柄菌属GA11菌株）中分离出的质粒pDG1的2.1 kb HindIII片段，并使用pAG60作为克隆载体。我们发现该重组质粒在大肠杆菌野生型细胞中频繁发生缺失。然而，当将该质粒导入gyrA基因的同基因温度敏感突变体菌株时，未观察到缺失现象。这些结果表明，大肠杆菌DNA促旋酶参与了缺失形成的机制。结果表明，源自2.1 kb HindIII插入片段的1.0 kb缺失体是通过消除1.1 kb区域产生的。对缺失体的序列分析表明，切割和重新连接发生在位于反向重复序列远端附近的六个近乎完美的直接重复序列（21 bp回文序列；AAAAAA(T/C)GGC(G/C)GCC(A/G)TTTTTT）中的两个之间，保留了一份重复序列。这些序列由局部短反向重复序列组成，切割和重新连接发生在两个区域之一。
