BOUNDARIES OF THE NICKING REGION FOR THE F-PLASMID TRANSFER ORIGIN, ORIT
BOUNDARIES OF THE NICKING REGION FOR THE F-PLASMID TRANSFER ORIGIN, ORIT
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DOI：
10.1111/j.1365-2958.1995.tb02353.x
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发表时间：
1995-03-01
影响因子：
3.6
通讯作者：
DEONIER, RC
中科院分区：
文献类型：
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作者：
LUO, YN;GAO, Q;DEONIER, RC
F 质粒 oriT 切口区域的范围是根据从碱基对 121 到碱基对 174 的区域中连续取代突变的特性以及由 tra 基因产物在体内诱导的 DNA 结构扭曲的 KMnO4 探测来确定的。切口和转移测定表明oriT的左边缘主要位于切口位点，并且切口结构域主要位于切口右侧17bp内。一些擅长切口的突变体显示终止频率降低，表明 oriT 切口不能保证有效终止。当供体中存在 tra 基因产物时，切口附近的 DNA（切口链上的 G(137)、T-138、G(140) 和 T-141）显示出对 KMnO4 的敏感性升高。无切口链上的碱基 C-145、C-146、C-147、C-149 和 G(150) 在 tra(+) 条件下也对氧化变得更加敏感。被 KMnO4 优先氧化的碱基位于切口结构域内，如取代突变体所定义，并且它们包括可以在 DNA 中产生扭结的二核苷酸。据计算，切口区域中的碱基对比侧翼区域中的碱基对在热力学上更稳定。
The extent of the F plasmid oriT nicking region was determined from the properties of successive substitution mutations in the region from base pair 121 to base pair 174 and from KMnO4 probing of DNA structural distortions induced in vivo by tra gene products. Nicking and transfer assays indicated that the left margin of oriT lies predominantly at the nick site, and that the nicking domain primarily lies within 17 bp to the right of the nick. Some mutants that were proficient for nicking showed reduced frequencies of termination, indicating that oriT nicking does not guarantee efficient termination. DNA in the vicinity of the nick (G(137), T-138, G(140), and T-141 on the nicked strand) showed elevated sensitivity to KMnO4 when tra gene products were present in the donor. Bases C-145, C-146, C-147, C-149, and G(150) on the un-nicked strand also became more sensitive to oxidation under tra(+) conditions. The bases preferentially oxidized by KMnO4 lie within the nicking domain, as defined by the substitution mutants, and they include dinucleotides that can produce kinks in the DNA. Base pairs in the nicking region are calculated to be more thermodynamically stable than base pairs in the flanking regions.