1978 Articles

Isolation and characterization of T antigen-negative revertants from a line of transformed rat cells containing one copy of the SV40 genome

Steinberg, Bettie; Pollack, Robert; Topp, William; Botchan, Michael

Negative selection with FUdR produced revertants from the transformed rat line 14B, which contains one insertion of the SV40 viral genome (Botchan, Topp and Sambrook, 1976). 14B contains nuclear T antigen, grows to a high density, grows in low serum and is anchorage-independent. The revertants fall into three classes with regard to viral DNA sequences: the SV40 DNA is retained; the SV40 DNA is retained but has undergone a deletion; and the SV40 DNA is lost, generating a cured cell. This heterogeneity is not a result of long-term passage. The revertants arise with a frequency of one in 8.4 x lo5 cells after as few as 12 passages. All three classes of revertants are T antigen-negative, density-sensitive, more serum sensitive than 14B and anchoragedependent. These data argue for a direct role of the functioning viral genome in the maintenance of the transformed state, and that with 148, the phenotypes of transformation are not virus gene dosage-dependent.