Site-specific recombination in human cells catalyzed by the wild-type integrase protein of coliphage HK022

The activity of the Integrase (Int) protein encoded by coliphage HK022 was tested in a human cell culture. Plasmids were constructed as substrates that carry the sites of the integration reaction (attP and attB) or the sites of excision (attL and attR). The site-specific recombination reactions were monitored in cis and in trans configurations by the expression of the green fluorescent protein (GFP) as a reporter. Cells cotransfected with the substrate plasmid(s) and with a plasmid that expresses the wild-type Int show efficient integration as well as excision in both configurations. The wild-type Int was active in the human cells without the need to supply the accessory proteins integration host factor (IHF) and excisionase (Xis) that are indispensable for the reaction in the bacterial host.