Site-specific integration by adeno-associated virus is directed by a cellular DNA sequence.

Different regions of an 8.2-kb cloned DNA segment containing the target for adeno-associated virus (AAV) integration in human chromosome 19q13-3-qter (AAVS1 locus) were subcloned in an Epstein-Barr virus-based shuttle vector and propagated as episomes in a derivative of the 293 human embryonic kidney cell line. Preferential recombination with an infecting AAV genome was assessed by measuring the frequency of recombinants among the shuttle vectors recovered in Escherichia coli. The signals which direct recombination with the AAV genome were localized to a 510-nt region at the 5' end of the 8.2-kb AAVS1 DNA. Hence, the results indicate that site-specific integration of AAV is directed by a specific DNA sequence on human chromosome 19. An unusual degree of DNA heterogeneity in the recovered vector was also associated with the 510 nt at the 5' end of AAVS1 DNA, suggesting that the AAV chromosomal integration locus may be involved in genomic instability.