Bednarz A L, Boocock M R, Sherratt D J
Institute of Genetics, University of Glasgow, Scotland, UK.
Genes Dev. 1990 Dec;4(12B):2366-75. doi: 10.1101/gad.4.12b.2366.
In site-specific recombination reactions catalyzed by Tn3 resolvase, the right and left arms of the res site are always religated to the correct partner. This poses the problem of how resolvase aligns the two sites correctly for the cleavage/religation reaction. We show that the "accessory" binding subsites II and III of res are important for correct alignment of the adjoining crossover subsite (subsite I). Deletion of subsites II and III from one of the two res sites removes a barrier to recombination between incorrectly aligned crossover subsites. Correct alignment does not require any DNA sequence asymmetry in the crossover subsite, DNA supercoiling, or covalent linkage of the two res sites. Our results suggest that correct subsite I alignment is determined by local, resolvase-mediated interactions of subsites II and III of both partners, consistent with a current model of the synapse. Surprisingly, the topological selectivity for intramolecular resolution in a supercoiled substrate does not require subsites II and III in both recombination partners.
在由Tn3解离酶催化的位点特异性重组反应中，res位点的右臂和左臂总是重新连接到正确的配对位点。这就产生了一个问题，即解离酶如何为切割/重新连接反应正确对齐这两个位点。我们发现，res的“辅助”结合亚位点II和III对于相邻交换亚位点（亚位点I）的正确对齐很重要。从两个res位点之一中删除亚位点II和III消除了不正确对齐的交换亚位点之间重组的障碍。正确对齐不需要交换亚位点中的任何DNA序列不对称、DNA超螺旋或两个res位点的共价连接。我们的结果表明，正确的亚位点I对齐是由两个配对位点的亚位点II和III之间局部的、解离酶介导的相互作用决定的，这与当前的突触模型一致。令人惊讶的是，超螺旋底物中分子内切割的拓扑选择性并不需要两个重组配对位点都有亚位点II和III。
