Localization and organization of integrated simian virus 40 sequences in a human cell line

Abstract

We have studied the location and organization of integrated SV40 DNA sequences in a human transformed cell line, GM639. Cells from this line were hybridized with mouse L cells deficient in thymidine kinase. Several independently derived somatic cell hybrids were analyzed for SV40 T-antigen by immunofluorescence and for SV40 sequences by digestion with site-specific restriction endonucleases followed by blot-hybridization with labeled SV40 DNA. The hybrids could be classified into T-ag + and T-ag − hybrids. The T-ag expression in these hybrids correlated with human chromosome 5 and no other human chromosome. The blot-hybridizations revealed that GM639 contained four separate integrated sequences of SV40. Three of these are located on human chromosome 5. The three sequences are relatively close to each other and are interspersed with host DNA sequences. Digestion with combinations of enzymes revealed that the sites within the viral genome which are utilized for integration are different for each SV40 genome. These results along with others indicate that there is no site specificity for integration of SV40 into human cells either at the chromosome level or at the gross viral DNA level.