Site-specific Recombination of Bacteriophage : The Role of Host Gene Products

Abstract

Integration of the DNA of bacteriophage λ into the chromosome of Escherichia coli occurs by recombination at two unique genetic loci: attP on the phage genome and attB on the bacterial chromosome. This reaction is therefore an example of site-specific recombination. The only phage-encoded protein required for recombination at these att (attachment) sites is Int, the product of the phage int gene. Integration of λ generates a prophage that is flanked by two new att sites, attL and attR. Excision, recombination between attL and attR, requires Xis, the product of the phage xis gene, as well as Int (for review, see Weisberg et al. 1977).