FIG. 4.

Kinetics of virus-induced transcriptional activation of the wild-type (wt) and mutI.cg muIFN-β promoters transiently or stably transfected. (A) HeLa cells were transiently transfected with the muIFN-β promoter (positions −330 to +20), either wild type (pBLCAT3-muIFN-β wt) or mutated on the upstream HMGI binding site (pBLCAT3-muIFN-β mutI.g) and fused to the CAT gene. (B) Kinetics of virus-induced transcriptional activation of short wild-type (pBLCAT3-muIFN-β wt150) and mutI.cg150 (pBLCAT3-muIFN-β mutI.cg150) muIFN-β promoters (positions −150 to +20) transiently transfected into HeLa cells. (C and D) Kinetics of virus-induced transcriptional activation of wild-type and mutI.cg muIFN-β promoters stably transfected into L929 cells. L929 cells were stably transfected with the muIFN-β promoter (positions −330 to +20), either wild type or mutated on the upstream HMGI binding site (mutI.cg) and fused to the CAT gene. For all experiments, the cells were induced (i) or mock induced (mi) with NDV. The absolute CAT activities (induced minus mock induced) of the cells collected at different times postinduction were measured as indicated in Materials and Methods. The corresponding values are expressed as a percentage of the CAT activity reached by the wild-type promoter at 18 h postinduction (24 h for panel D), which we have considered to correspond to 100%. Except for panel D, the values shown correspond to the average values obtained from three independent experiments, with duplicate determinations for each induced and mock-induced point.