Site-Specific Genomic Integration in Mammalian Cells Mediated by Phage φC31 Integrase

Abstract

We previously established that the phage φC31 integrase, a site-specific recombinase, mediates efficient integration in the human cell environment at attB and attP phage attachment sites on extrachromosomal vectors. We show here that phageattP sites inserted at various locations in human and mouse chromosomes serve as efficient targets for precise site-specific integration. Moreover, we characterize native “pseudo”attP sites in the human and mouse genomes that also mediate efficient integrase-mediated integration. These sites have partial sequence identity to attP. Such sites form naturally occurring targets for integration. This phage integrase-mediated reaction represents an effective site-specific integration system for higher cells and may be of value in gene therapy and other chromosome engineering strategies.

ACKNOWLEDGMENTS

Bhaskar Thyagarajan and Eric C. Olivares contributed equally to this work.

We thank Eddie Baba and Andrew Neviaser for technical support and Man-Wah Tan for comments on the manuscript.

National Institutes of Health grants DK55569 and DK58187 provided support to the Calos lab. E.C.O. was supported by a graduate fellowship from the Ford Foundation, D.G. was supported by a graduate training grant from the NIH, and B.T. was partially supported by PHS grant CA09302 from the National Cancer Institute.