|MoBio||Site-specific Recombination||Chapter 8|
Site-specific recombination occurs at a specific DNA sequence. The first example was found in the integration between λ DNA and E. coli DNA. Both of them contain a sequence, 5'-TTTATAC-3', called the attachment site, which allows the two DNA molecules to attach together by base pairing. Once attached, the enzyme integrase catalyzes two single strand breaks as in the Holliday model. After a short branch migration, the integrase exerts a second strand cuts on two other strands. Resolution of two Holliday junctions completes the integration process.