Figure 5.

Transcriptional activation of a heterologous SRF in response to PDGF and MEK-1 stimulation is reduced in KO cells. (A) Schematic representation of the heterologous SRF-reporter system with a fusion protein of the Gal-4–DNA-binding domain (amino acids 1–147 of Gal-4) and human SRF (amino acids 10–301 of SRF). (B) WT and KO cells were cotransfected with the described reporter plasmid. After overnight culture in serum-free medium, cells were left untreated or treated with PDGF for 3 hr before lysis. Data represent the stimulation of luciferase activity/β-galactosidase activity in stimulated vs. untreated cells. Data are the mean of four independent experiments ± SEM. (C) Cotransfections were performed as described for B with the exception that PDGF stimulation was replaced by cotransfection of an MEK-1 expression plasmid (**, P < 0.01).