The differential effect of interferon on T antigen production in simian virus 40-infected or transformed cells.

The ability of interferon (IF) to inhibit T antigen (Ag) production in simian virus 40 (SV40)-infected or transformed cells was studied primarily through the use of immunoprecipitation followed by gel electrophoresis and autoradiography. Addition of IF to monkey cells prior to or subsequent to inoculation with SV40 resulted in an inhibition in the amount of T Ag that was synthesized late in infection. In contrast when a similar experiment was performed with a is mutant of SV40, tsA58, which does not replicate at the nonpermissive temperature, there was no inhibition in the amount of immunoprecipitable T Ag when IF was added at 30 hr postinfection at 40.5°. The effect of IF on an integrated versus nonintegrated genome within the same cell population was studied in an SV40-transformed mouse cell, H6-15, which is temperature sensitive for the transformed phenotype and for expression of T antigen. In shift-down experiments it was shown that the reappearance of SV40 T Ag was insensitive to the addition of IF whereas superinfection of these same cells with polyoma virus resulted in a dose-dependent inhibition of polyoma T Ag infection. An SV40-transformed mouse cell line (nonpermissive) and two SV40-transformed human cell lines (semipermissive) were passaged in the presence of IF for four generations. Approximately the same amount of labeled T Ag could be immunoprecipitated from IF-treated compared to control mouse cultures whereas, there was a marked decrease in the amount of newly synthesized T Ag in IF-treated human cultures. All these results are compatible with the hypothesis that IF affects differentially the expression of early viral genes whether the viral DNA is integrated or not integrated.