West S C, Howard-Flanders P
Cell. 1984 Jun;37(2):683-91. doi: 10.1016/0092-8674(84)90401-x.
Using gapped circular DNA and homologous duplex DNA cut with restriction nucleases, we show that E. coli RecA protein promotes strand exchanges past double-strand breaks. The products of strand exchange are heteroduplex DNA molecules that contain nicks, which can be sealed by DNA ligase, thereby effecting the repair of double-strand breaks in vitro. These results show that RecA protein can promote pairing interactions between homologous DNA molecules at regions where both are duplex. Moreover, pairing leads to strand exchanges and the formation of heteroduplex DNA. In contrast, strand exchanges are unable to pass a double-strand break in the gapped substrate. This apparent paradox is discussed in terms of a model for RecA-DNA interactions in which we propose that each RecA monomer contains two nonequivalent DNA-binding sites.
利用缺口环状DNA和经限制性核酸酶切割的同源双链DNA，我们发现大肠杆菌RecA蛋白能促进链交换越过双链断裂处。链交换的产物是含有切口的异源双链DNA分子，这些切口可被DNA连接酶封闭，从而在体外实现双链断裂的修复。这些结果表明，RecA蛋白能够在同源DNA分子均为双链的区域促进它们之间的配对相互作用。此外，配对会导致链交换并形成异源双链DNA。相比之下，链交换无法越过缺口底物中的双链断裂处。我们根据RecA-DNA相互作用模型讨论了这一明显的矛盾，在该模型中我们提出每个RecA单体含有两个不等价的DNA结合位点。
