A novel site-specific recombination system derived from bacteriophage φMR11

We report identification of a novel site-specific DNA recombination system that functions in both it? vivo and ill Vitro, derived from lysogenic Staphylococcus aureus phage phi MR11. In silico analysis of the phi MR11 genome indicated orf1 as a putative integrase gene. Phage and bacterial attachment sites (attP and attB, respectively) and attachment junctions were determined and their nucleotide sequences decoded. Sequences of attP and attB were mostly different to each other except for a two bp common core that was the crossover point. We found several inverted repeats adjacent to the core sequence of attP as potential protein binding sites. The precise and efficient integration properties of phi MR11 integrase were shown on attP and attB in Escherichia coli and the minimum size of attP was found to be 34 bp. In in vitro assays using crude or purified integrase, only buffer and substrate DNAs were required for the recombination reaction, indicating that other bacterially encoded factors are not essential for activity. (C) 2008 Elsevier Inc. All rights reserved.