FIG. 3.

MCMV infection transactivates the TS promoter in quiescent NIH 3T3 cells. DNA (2 μg) from construct pTLG or pTLG:I1d1.0 was transiently transfected along with carrier DNA (10 μg of pBluescript SK) into NIH 3T3 cells as described in Materials and Methods. After 18 h, cells were washed and growth arrested in 0.5% calf serum for 48 h. Thereafter, transfectants were infected with MCMV or UV-irradiated MCMV, mock infected, or serum stimulated to reenter the cell cycle. Total cytoplasmic extracts were isolated at the indicated times after virus infection or serum stimulation and assayed for luciferase activity. Reporter gene activity was normalized to the amount of plasmid DNA introduced into recipient cells by DNA dot blot analysis. The resulting luciferase activity is expressed as fold induction relative to basal levels measured in cells transfected with pTLG or pTLG:I1d1.0 and then mock infected, which was set at 1. The experiment was repeated twice, and representative results are reported.