Preferential integration of the Ad5/SV40 hybrid virus at the highly recombinogenic human chromosomal site 1p36

Human fibroblasts transformed with an adenovirus-5/simian virus 40 recombinant construct (Ad5/SV40) were analyzed to determine the chromosomal site(s) of virus integration. This was firstly done by in situ hybridization using metaphase and prometaphase chromosomes and 125I-labeled Ad5 DNA. Out of seven transformed cell lines (six of clonal origin and one uncloned), six were proven to have integrated the viral genome at the short- or the long-subtelomeric regions of autosome 1, two regions known to include chromosomal modification sites induced by acute infection with Ad12. Characterization of the integration sites was carried out by restriction analysis. Transformed cell lines with the same major chromosomal integration site were found to have the viral genome inserted in restriction fragments of different size, indicating that viral integration has occurred at different sites within a relatively small chromosomal region. Molecular studies carried out on one of the transformed cell lines (H13.1) gave an independent confirmation of the viral integration at the subterminal region of autosome 1 short arm. Nucleotide sequencing at this cellular-viral junction has shown that the virus has integrated within tandemly repeated Alu-like elements and that the cellular flanking sequences have several homologies with variable number of tandem repeats core sequences. Many possible open reading frames were identified in the DNA segment adjacent to the Alu-like elements.