Hauer B, Shapiro J A
Mol Gen Genet. 1984;194(1-2):149-58. doi: 10.1007/BF00383510.
Our isolate of Tn7 (named Tn7S ) contains an IS1 insertion, and this IS1 can be converted into Tn9. In vitro and in vivo deletions of Tn7S and Tn7S ::Tn9 define regions of the transposon required for antibiotic resistance and transposition. Complementation of deletion mutants by cloned Tn7 fragments indicates the existence of two regions, denoted tnp7A and tnp7B , required for all transposition events. Another region, denoted tnp7C , is required for transposition from the chromosome to RP1 but not for transposition from a small IncP-1 replicon to the chromosome. The presence of Tn7S terminal sequences in an RP1 replicon reduces the transposition of a second Tn7S derivative from the chromosome by about one order of magnitude. The measured frequency of Tn7S transpositions from a small IncP-1 replicon to the chromosome depends on the particular incompatibility system used to eliminate that replicon. Genetic and physical data indicate that high frequencies of Tn7S transposition to the chromosome (greater than or equal to 40%) are triggered by the IncP-1 incompatibility reaction, thus suggesting the existence of a Tn7 mechanism for sensing the state of the carrier replicon.
我们分离得到的Tn7（命名为Tn7S）含有一个IS1插入序列，并且这个IS1可以转化为Tn9。Tn7S和Tn7S::Tn9在体外和体内的缺失确定了转座子中对抗生素抗性和转座所必需的区域。通过克隆的Tn7片段对缺失突变体进行互补分析表明存在两个区域，分别记为tnp7A和tnp7B，它们是所有转座事件所必需的。另一个区域，记为tnp7C，是从染色体向RP1转座所必需的，但不是从小的IncP-1复制子向染色体转座所必需的。RP1复制子中Tn7S末端序列的存在使第二个Tn7S衍生物从染色体上的转座频率降低了约一个数量级。测量得到的Tn7S从小的IncP-1复制子向染色体转座的频率取决于用于消除该复制子的特定不相容性系统。遗传和物理数据表明，IncP-1不相容反应触发了Tn7S向染色体的高频转座（大于或等于40%），因此表明存在一种用于感知载体复制子状态的Tn7机制。
