FIG. 9.

De novo SV5 protein synthesis is required for STAT1 degradation in IFN-pretreated cells but not in untreated cells. (a) 2fTGH cells were (+IFN) or were not (−IFN) pretreated with IFN-α (1,000 IU ml) for 18 h prior to being mock infected (lane 1) or infected with “infectious” SV5 (lane 2) or UV-inactivated virus (lane 3; the efficiency of UV inactivation was demonstrated by showing that even after 24 h of infection, no virus protein synthesis had occurred, as judged by immunofluorescence). At 8 h p.i., total cell extracts were made, and STAT1 was detected by immunoblot analysis. (b) 2fTGH cells were (+IFN) or were not (−IFN) pretreated with IFN-α for 18 h prior to being mock infected (lane 1) or infected with “infectious” SV5 (lane 2). From the time of infection, cells were cultured in the presence of cycloheximide (+CX; 50 μg/ml). At 8 h p.i., total cell extracts were made, and STAT1 was detected by immunoblot analysis.