Fig. 3.

Site-specific genome integration in vivo.(A) Kinetic profiles of SEAP in treated mouse sera. Normal CD1 mice were injected with the integrating plasmid containing the SEAP expression cassette and buffer, plasmids expressing the normal integrase, or NLS-modified integrase. In the normal integrase treatment group (open circles), SEAP expression reached its peak at 24 h postinjection, then decreased in 2 weeks and remained stable at a low level. The group treated with modified integrase (filled squares) had higher levels of SEAP in their serum samples (P < 0.05). In the integrase-negative group (filled triangles), no SEAP expression was detected at 2 weeks postinjection. (B) In vivo integration frequency. The genomic DNA samples from the livers of treated mice were used for real-time PCR assays to determine the integration frequencies at various pseudo-attP sites. More than 95% of integration events occurred at the major site mpsP3 (1.762% per haploid genome). Another 4% of integration events occurred in the two minor sites mpsP5 and mpsP7 (0.048% and 0.044% per haploid genome). Less than 1% of integration events occurred in the other minor sites.