BACTERIOPHAGE-LAMBDA SITE-SPECIFIC RECOMBINATION PROCEEDS WITH A DEFINED ORDER OF STRAND EXCHANGES
BACTERIOPHAGE-LAMBDA SITE-SPECIFIC RECOMBINATION PROCEEDS WITH A DEFINED ORDER OF STRAND EXCHANGES
复制标题
DOI：
10.1016/0022-2836(88)90602-x
复制
发表时间：
1988-11-05
影响因子：
5.6
通讯作者：
NASH, HA
中科院分区：
文献类型：
--
作者：
KITTS, PA;NASH, HA
先前的工作已经建立了噬菌体基因组的整合。进入其细菌宿主染色体的过程是通过两个独立的链交换进行的，这产生并随后分解一个霍利迪结构中间体。我们发现，一个硫代磷酸酯取代的重组位点的一条链中的交换位点抑制霍利迪结构的产量远远超过一个类似的取代在另一条链。此外，我们表明，霍利迪结构，积累在畅通的反应都是由一个特定的一对链的重组。我们的结论是，有一个强烈的偏见，在选择链，启动交叉。切除，即切除整合的原噬菌体的重组反应，表现出与整合相同的偏倚。这证明，至少在链交换的水平上，切除不是整合的简单逆转。我们已经改变了部分的噬菌体附着位点，attP的相对方向，以证明链交换的偏见是由周围的交换点的核心attP，但更远的元素在其武器的本地环境决定。这表明链交换的顺序是由不对称性决定的，在attP处形成的核小体样结构在链交换之前将细菌位点attB带入双转位。最后，我们使用改变的attP来表明，attP和attB之间的同源性是最关键的，当它是相邻的点的链交换。
Previous work has established that integration of the genome of bacteriophage .lambda. into the chromosome of its bacterial host proceeds via two independent strand exchange, which make and then resolve a Holliday-structure intermediate. We find that a phosphorothioate substitution at the site of exchange in one strand of a recombination site depresses the yield of Holliday structures much more than a similar substitution in the other strand. Furthermore, we show that the Holliday structures that accumulate in unblocked reactions have all been made by recombinations of one particular pair of strands. We conclude that there is a strong bias in the choice of strands that initiate crossing-over. Excision, the recombination reaction that excises the integrated prophage, exhibits the same bias as integration. This proves, at least at the level of strand exchange, that excision is not the simple reversal of integration. We have altered the relative orientation of parts of the phage attachment site, attP, to demonstrate that the strand-exchange bias is determined not by the local environment around the point of exchange in the core of attP but by more distant elements in its arms. This suggests that the order of the strand exchanges is dictated by an asymmetry in the way that the nucleosome-like structure that forms at attP brings the bacterial site, attB, into juxataposition prior to strand exchange. Finally, we use the the altered attP to show that homology between attP and attB is most critical when it is adjacent to the point of strand exchange.