Recombination between viral and cellular sequences generates transforming sarcoma virus

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Abstract
A series of sarcoma viruses was obtained from tumors induced by transformation-defective (td) mutants of the Schmdit-Ruppin strain of Rous sarcoma virus, subgroup A (SR-A). The RNA sequences of these recovered avian sarcoma viruses (rASV) were compared with those of td mutants and of SR-A by oligonucleotide fingerprinting. Of 6 sarcoma-specific oligonucleotides present in SR-A RNA, 3-6 were missing in the RNA of the four td mutants examined. All isolates of rASV examined regained these 6 oligonucleotides. Most rASV RNA have 3 new oligonucleotides not present in the RNA either of td mutants or of SR-A. The newly obtained oligonucleotides are located between 800 and 2600 nucleotides from the 3'' end of rASV RNA, which corresponds to the src region of SR-A RNA mapped previously. Viral RNA of 2 td mutants isolated from a clone of rASV lack most src-specific oligonucleotides, including the 3 new ones. No differences were found among RNA of td, SR-A and rASV in the regions outside of src. Apparently, RNA sequences that rASV acquired from [chicken embryo fibroblast] cells in the process of conversion from td virus to transforming virus are mapped within the src region and segregate with the transforming function. Some sequences are new and some are identical with those in SR-A RNA.