Figure 6.

MEK1 is activated by TGF-β and induces Egr-1. A: Foreskin fibroblasts were incubated with TGF-β for indicated periods and whole-cell lysates were subjected to Western analysis. Representative autoradiograms are shown. B: NIH3T3 fibroblasts were cotransfected with indicated concentrations of constitutively active MEK1 (caMEK1) or empty vector along with Egr-1-luc (left). After incubation for 24 hours, cultures were harvested, and cell lysates were assayed for their luciferase activities. Transfected NIH3T3 fibroblasts were incubated in media containing U0126 for 24 hours (right). Results, normalized with Renilla luciferase, are expressed as means ± SD of triplicate determinations from two independent experiments. C: Whole-cell lysates prepared from transfected NIH3T3 fibroblasts incubated with TGF-β for 24 h were examined by Western analysis. Representative immunoblots are shown.