Replicative and conservative transposition in bacteria
Replicative and conservative transposition in bacteria
复制标题
细菌中的复制性和保守性转座
DOI：
10.1016/0092-8674(86)90586-6
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发表时间：
1986
期刊：
影响因子：
64.5
通讯作者：
N. Grindley
中科院分区：
文献类型：
--
作者：
K. Derbyshire;N. Grindley
当一个细菌转座子跳到一个新的基因组位置时，它是在这个过程中复制自己从而产生两个转座子拷贝，还是从旧位点切除自己并整合到新位点而不复制？是重复的还是保守的：这一直是关于转座机制的中心问题。缺乏任何良好的特点，在体外系统研究转座（噬菌体Mu系统除外）限制了进展。然而，由于一些优雅的遗传学实验，答案现在似乎更清晰了。复制转座大多数的转座子机制研究都是用三种常见的细菌转座子进行的：（i）插入序列（IS）及其复合转座子;（ii）转座子的Tn 3家族;（iii）转座噬菌体Mu。转座的复制机制很早就被确立了，而且是一个强有力的例子。它来自两个方面--来自Tn 3和噬菌体Mu的研究。Tn 3和相关元件的转座通常通过两步过程发生（参见Grindley，Cell 32，3-5，1983; Heffron，在移动的遗传元件中，J. Shapiro编辑，Academic Press，1983，pp. 223-260）。首先，供体和靶复制子融合以形成共整合分子，其在靶和供体DNA的每个连接处具有转座子的拷贝（图1）。然后，两个转座子拷贝之间的位点特异性重组将共整合体减少到其两个组成复制子中，再生供体并通过简单的插入形成靶。这两个步骤涉及两种蛋白质的连续作用，转座酶和解离酶，两者都由转座子编码。转座酶依赖性步骤的复制性质从共整合中间体的性质是清楚的;虽然由具有单个转座子拷贝的靶和供体形成，但它含有两个转座子拷贝。
When a bacterial transposon jumps to a new genomic location, does it replicate itself in the process thus generating two transposon copies, or does it excise itself from the old site and integrate into the new site without duplication? eplicative or conservative: this has been a central question concerning the mechanism of transposition. The lack of any well-characterized in vitro systems for studying transposition (with the exception of the bacteriophage Mu system) has restricted progress. However, thanks to some elegant genetic experiments, the answer now seems much clearer.Replicative Transposition Most mechanistic studies have been performed with members of three common groups of bacterial transposons:(i) the insertion sequences (IS) and their composite transposons;(ii) the Tn3 family of transposons; and (iii) the transposing bacteriophage Mu. The case for a replicative mechanism of transposition was established early and was a strong one. It came on two fronts-from studies of Tn3 and bacteriophage Mu. Transposition of Tn3 and related elements generally occurs by a two-step process (see Grindley, Cell 32, 3-5, 1983; Heffron, in Mobile Genetic Elements, ed. J. Shapiro, Academic Press, 1983, pp. 223-260). First, the donor and target replicons are fused to form a cointegrate molecule, which has a copy of the transposon at each junction of target and donor DNA (Figure 1). A site-specific recombination between the two transposon copies then reduces the cointegrate into its two constituent replicons, regenerating the donor and forming the target with a simple insertion. The two steps involve the consecutive action of two proteins, transposase and resolvase, both encoded by the transposon. The replicative nature of the transposasedependent step is clear from the nature of the cointegrate intermediate; although formed from a target and a donor with a single transposon copy, it contains two copies of the transposon.