FIG. 5.

The V protein of SV5, but not P, blocks activation of an IFN-α/β-responsive promoter in human cells. 2fTGH cells were transfected with a mixture of plasmids that contained the luciferase gene under the control of either the herpes simplex virus TK promoter (a) or an IFN-α/β-responsive promoter (b; 0.1 μg), together with 0.3 μg of pEFlink2 (control), pEF.SV5-P (expressing the SV5 P protein), or pEF.SV5-V (expressing the SV5 V protein). Also included in the transfection mix was 0.1 μg of plasmid pJATlacZ, in which the lacZ gene is under the control of the rat β-actin promoter. At 40 h posttransfection, the culture medium was (+) or was not (−) supplemented with IFN. Four hours later, luciferase and β-galactosidase activities in cellular lysates were measured. Luciferase activity, expressed in relative light units, was normalized to β-galactosidase activity.