Affiliation:
1. Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892
Abstract
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.
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
Cited by
10 articles.
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