Integrative recombination of bacteriophage lambda requires perfect homology between partners over a short segment of DNA, the overlap region, that separates the positions of top and bottom strand exchange. We constructed a specific cross-link between complementary strands in the overlap region of one partner, using a method designed to introduce minimal distortion of DNA. The modified attachment site could initiate recombination, forming a Holliday junction, but could not resolve this junction so as to complete the recombination. This demonstrates that the ability of complementary base-pairs to dissociate is important for overlap region function and strongly supports the view that branch migration across this region is the way homology is sensed during integrative recombination. © 1991.
Cowart, M., Benkovic, S. J., & Nash, H. A. (1991). Behavior of a cross-linked attachment site: Testing the role of branch migration in site-specific recombination. Journal of Molecular Biology, 220(3), 621–629. https://doi.org/10.1016/0022-2836(91)90105-F