Bacteriophage P2 integrase: another possible tool for site-specific recombination in eukaryotic cells

Abstract

To investigate if the site-specific tyrosine integrase (Int) from phage P2 has features that would make it interesting for use of gene transfer into eukaryotic cells. These include the possibility of promoting recombination with a nonphage sequence, abolishing the requirement for the bacterial DNA-binding and -bending protein integration host factor (IHF), and localization to the nucleus of eukaryotic cells. We show that the Int protein catalyzes site-specific recombination using a human sequence in Escherichia coli and in vitro although not as efficiently as with the wild-type bacterial sequence, and that insertion of high mobility group recognition boxes in the phage attachment site substrate abolish the requirement of IHF and allows efficient recombination in vitro in a eukaryotic cell extract. Furthermore, we show by fluorescence that the Int protein contains a functional intrinsic nuclear localization signal, localizing it to the nucleus in both HeLa and 293 cells. We conclude that P2 Int may be a potential tool for site-specific integration of genes into the human chromosome. The study implies the possibility of using multiple prokaryotic Int proteins with different specific integration sites in human cells for future gene therapy programmes.