Wolkow C A, DeBoy R T, Craig N L
Howard Hughes Medical Institute, Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Genes Dev. 1996 Sep 1;10(17):2145-57. doi: 10.1101/gad.10.17.2145.
Most transposons display target site selectivity, inserting preferentially into sites that contain particular features. The bacterial transposon Tn7 possesses the unusual ability to recognize two different classes of target sites. Tn7 inserts into these classes of target sites through two transposition pathways mediated by different combinations of the five Tn7-encoded transposition proteins. In one transposition pathway, Tn7 inserts into a unique site in the bacterial chromosome, attTn7, through specific recognition of sequences in attTn7; the other transposition pathway ignores the attTn7 target. Here we examine targets of the non-attTn7 pathway and find that Tn7 preferentially inserts into bacterial plasmids that can conjugate between cells. Furthermore, Tn7 appears to recognize preferred targets through the conjugation process, as we show that Tn7 inserts poorly into plasmids containing mutations that block plasmid transfer. We propose that Tn7 recognizes preferred targets through features of the conjugation process, a distinctive target specificity that offers Tn7 the ability to spread efficiently through bacterial populations.
大多数转座子表现出靶位点选择性，优先插入含有特定特征的位点。细菌转座子Tn7具有识别两类不同靶位点的非凡能力。Tn7通过由五种Tn7编码的转座蛋白的不同组合介导的两条转座途径插入这些类别的靶位点。在一条转座途径中，Tn7通过特异性识别attTn7中的序列插入细菌染色体中的一个独特位点attTn7；另一条转座途径则忽略attTn7靶位点。在这里，我们研究了非attTn7途径的靶标，发现Tn7优先插入能够在细胞间进行接合的细菌质粒中。此外，Tn7似乎通过接合过程识别优先靶标，因为我们表明Tn7很难插入含有阻断质粒转移突变的质粒中。我们提出，Tn7通过接合过程的特征识别优先靶标，这种独特的靶标特异性使Tn7能够在细菌群体中高效传播。
