Reed R R
Proc Natl Acad Sci U S A. 1981 Jun;78(6):3428-32. doi: 10.1073/pnas.78.6.3428.
Transposition of the genetically related insertion elements gamma delta and Tn3 is thought to involve two steps. In the case of transposition from one replicon to another, the first step is fusion of the parent and target replicons with the element appearing in direct orientation at the two junctions. In a subsequent reaction, the cointegrate structure is resolved via a site-specific recombination event. I have constructed two plasmids, each carrying segments of gamma delta and Tn3, that contain the internal resolution site. The tnpR gene product encoded by either Tn3 or gamma delta mediates intramolecular recombination between these two sites. The product of this recombination is a hybrid region that contains gamma delta and Tn3 sequences fused at the point of crossover. DNA sequence analysis of such recombinants indicates that the recombination occurs within a 19-base-pair (bp) region of exact homology between gamma delta and Tn3. The site lies in the 160-bp center intercistronic region, 50 bp before the beginning of the tnpA gene. My results therefore suggest a model for the coupled regulation of the repressor (tnpR) and the transposase (tnpA) genes and site-specific recombination of transposition intermediates. The Tn3/gamma delta recombination system and bacteriophage lambda integration are compared.
人们认为，与基因相关的插入元件γδ和Tn3的转座涉及两个步骤。在从一个复制子转座到另一个复制子的情况下，第一步是亲代复制子和靶复制子融合，元件以直接方向出现在两个连接处。在随后的反应中，共整合结构通过位点特异性重组事件得以解析。我构建了两个质粒，每个质粒都携带γδ和Tn3的片段，其中包含内部解析位点。由Tn3或γδ编码的tnpR基因产物介导这两个位点之间的分子内重组。这种重组的产物是一个杂合区域，其中包含在交叉点处融合的γδ和Tn3序列。对此类重组体的DNA序列分析表明，重组发生在γδ和Tn3之间精确同源的19个碱基对（bp）区域内。该位点位于160 bp的中央基因间区域，在tnpA基因起始前50 bp处。因此，我的结果提示了一种阻遏物（tnpR）和转座酶（tnpA）基因的偶联调控以及转座中间体的位点特异性重组的模型。对Tn3/γδ重组系统和噬菌体λ整合进行了比较。
