title: Preferential integration of adeno-associated virus type 2 into a polypyrimidine/polypurine-rich region within AAVS1.
abstract: Adeno-associated virus type 2 (AAV2) preferentially integrates its genome into the AAVS1 locus on human chromosome 19. Preferential integration requires the AAV2 Rep68 or Rep78 protein (Rep68/78), a Rep68/78 binding site (RBS), and a nicking site within AAVS1 and may also require an RBS within the virus genome. To obtain further information that might help to elucidate the mechanism and preferred substrate configurations of preferential integration, we amplified junctions between AAV2 DNA and AAVS1 from AAV2-infected HeLaJW cells and cells with defective Artemis or xeroderma pigmentosum group A genes. We sequenced 61 distinct junctions. The integration junction sequences show the three classical types of nonhomologous-end-joining joints: microhomology at junctions (57%), insertion of sequences that are not normally contiguous with either the AAV2 or the AAVS1 sequences at the junction (31%), and direct joining (11%). These junctions were spread over 750 bases and were all downstream of the Rep68/78 nicking site within AAVS1. Two-thirds of the junctions map to 350 bases of AAVS1 that are rich in polypyrimidine tracts on the nicked strand. The majority of AAV2 breakpoints were within the inverted terminal repeat (ITR) sequences, which contain RBSs. We never detected a complete ITR at a junction. Residual ITRs at junctions never contained more than one RBS, suggesting that the hairpin form, rather than the linear ITR, is the more frequent integration substrate. Our data are consistent with a model in which a cellular protein other than Artemis cleaves AAV2 hairpins to produce free ends for integration.
authors.affiliation: Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health/DHHS, 8 Center Drive MSC 0840, Bethesda, MD 20892-0840, USA.
authors.forename: Victor J
authors.initials: VJ
authors.lastname: McAlister
authors.forename: Roland A
authors.initials: RA
authors.lastname: Owens
mesh_terms: D001665:Binding Sites / Q000502:physiology; D002888:Chromosomes, Human, Pair 19 / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D053904:DNA Breaks, Single-Stranded; D004268:DNA-Binding Proteins / Q000378:metabolism; D000229:Dependovirus / Q000235:genetics / Q000378:metabolism*; D004720:Endonucleases; D016679:Genome, Viral / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D009687:Nuclear Proteins / Q000172:deficiency / Q000378:metabolism; D040641:Quantitative Trait Loci / Q000235:genetics; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D020079:Terminal Repeat Sequences / Q000502:physiology*; D014764:Viral Proteins / Q000378:metabolism; D016662:Virus Integration / Q000502:physiology*; D051760:Xeroderma Pigmentosum Group A Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D014764:Viral Proteins; D051760:Xeroderma Pigmentosum Group A Protein; C068734:rep proteins, Adeno-associated virus 2; C426344:DCLRE1C protein, human; D004720:Endonucleases