No abstract

Two cell lines, RVP3 and RVA4, derived originally from mouse tumors induced by the Prague and Schmidt-Ruppin strain of RSV, respectively, were studied. tall attempts failed to induce infectious virus production in RVP3 cells by fusion with chicken fibroblasts even if the cells were infected with avian leukosis viruses. Also, attempts to rescue the viral genome by transfection were unsuccessful. RVP3 cells harboured 31-45% of the viral genome sequences, as was shown by molecular hybridization, and therefore they were designated cryptovirogenic. The tumour cell line RVA4 did not contain any detectable viral sequences. The significance of the detection of the incomplete Rous virus genome sequences in mammalian cells is discussed.

No abstract

The rescue of RSV from the "poorly '' virogenic RSV-transformed rat lines L W13-RsKI and L W13-RsK4 was achieved only after treatment with 5-brornodeoxyuridine (BUdR) before fusion with chicken embryo fibroblasts. Treatment of these lines with mitomycin C ( M C ) before fusion did not result in R S V rescue. Treatment of RSV-transformed non-virogenic mouse lines, R VA4 and RVP3, with BUdR or MC before fusion with chick embryo fibroblasts did not lead to the production of RSV.