Site-specific recombination between cloned attP and attB sites from the Haemophilus influenzae bacteriophage HP1 propagated in recombination-deficient Escherichia coli.

Plasmids were constructed which contain both attP and attB DNA segments derived from the insertion sites of the lysogenic bacteriophage HP1 and its host, Haemophilus influenzae. Similar plasmids containing the two junction segments (attL and attR regions) between the phage genome and the lysogenic host chromosome were also prepared. The formation of recombinant dimer plasmids was observed when attP-attB plasmids were propagated in Escherichia coli HB101 (recA), while plasmids containing the junction segments did not form recombinant dimers. Deletion of the phage DNA segment adjacent to the attP site from the attP-attB constructions eliminated detectable recombination, suggesting that this sequence contains the gene encoding the HP1 integrase. No plasmid recombination was observed in strains of E. coli defective in integration host factor. This suggests that integration host factor is important in the expression or activity of the system which produces the site-specific recombination of sequences derived from HP1 and H. influenzae. Further, it suggests that a protein functionally analogous to E. coli integration host factor may be present in H. influenzae.