FIG. 4.

Effect of viruses containing wt or mutant M proteins on the activity of the IFN-β promoter. HeLa cells were transfected with 1 μg of pβlux plasmid DNA encoding luciferase under control of the IFN-β promoter. At 24 h posttransfection, cells were infected with viruses containing wt or mutant M proteins at a multiplicity of 20 PFU/cell. Cells were harvested at 3, 6, and 9 h postinfection, and luciferase activity was determined. Cells were transfected with pβlux DNA and mock infected as negative controls (Con), and cells were transfected with pβlux DNA and then treated with poly(I)-poly(C) (pI:pC) as positive controls. Data are expressed as a percentage of the luciferase activity expressed by uninfected cells transfected with 250 ng of pGL3 plasmid DNA to detect constitutive luciferase activity from the SV40 promoter. Data shown are means ± standard errors of the means for four independent experiments.