Integrated simian virus 40 sequences in transformed cell DNA: analysis using restriction endonucleases

The DNAs from five independent simian virus 40 (SV40) transformants of the BALB/c 3T3 mouse cell line were digested with either the HpaII or the BamHI restriction endonuclease and the resulting fragments were fractionated by gel electrophoresis. The DNA fragments were denatured in situ in the gel and transferred to a membrane filter. Fragments containing viral DNA were detected by hybridization with high specific activity ³²P labeled SV40 complementary RNA (cRNA) synthesized in vitro. Each of the lines yielded a small number of fragments containing SV40 DNA and the fragments from each line were different. This observation shows that the structure of the integrated SV40 DNA and/or its location in the host DNA are different in each line.