Arciszewska L K, Drake D, Craig N L
Department of Microbiology and Immunology, University of California, San Francisco 94143.
J Mol Biol. 1989 May 5;207(1):35-52. doi: 10.1016/0022-2836(89)90439-7.
We have identified and characterized the cis-acting sequences at the termini of the bacterial transposon Tn7 that are necessary for its transposition. Tn7 participates in two kinds of transposition event: high-frequency transposition to a specific target site (attTn7) and low-frequency transposition to apparently random target sites. Our analyses suggest that the same sequences at the Tn7 ends are required for both transposition events. These sequences differ in length and nucleotide structure: about 150 base-pairs at the left end (Tn7L) and about 70 base-pairs at the right end (Tn7R) are necessary for efficient transposition. We also show that the ends of Tn7 are functionally distinct: a miniTn7 element containing two Tn7R ends is active in transposition but an element containing two Tn7L ends is not. We also report that the presence of Tn7's cis-acting transposition sequences anywhere in a target replicon inhibits subsequent insertion of another copy of Tn7 into either an attTn7 target site or into random target sites. The inhibition to an attTn7 target site is most pronounced when the Tn7 ends are immediately adjacent to attTn7. We also show that the presence of Tn7R's cis-acting transposition sequences in a target replicon is necessary and sufficient to inhibit subsequent Tn7 insertion into the target replicon.
我们已经鉴定并表征了细菌转座子Tn7末端的顺式作用序列，这些序列是其转座所必需的。Tn7参与两种转座事件：高频转座至特定靶位点（attTn7）以及低频转座至明显随机的靶位点。我们的分析表明，两种转座事件都需要Tn7末端相同的序列。这些序列在长度和核苷酸结构上有所不同：左端（Tn7L）约150个碱基对和右端（Tn7R）约70个碱基对对于高效转座是必需的。我们还表明，Tn7的末端在功能上是不同的：含有两个Tn7R末端的miniTn7元件在转座中具有活性，但含有两个Tn7L末端的元件则没有。我们还报告称，靶复制子中任何位置存在Tn7的顺式作用转座序列都会抑制随后另一个Tn7拷贝插入attTn7靶位点或随机靶位点。当Tn7末端紧邻attTn7时，对attTn7靶位点的抑制最为明显。我们还表明，靶复制子中存在Tn7R的顺式作用转座序列对于抑制随后Tn7插入靶复制子是必要且充分的。
