Analysing the effect of growth factors on Brn-3b promoter activity. (a) Brn-3b promoter (BSX) activity was measured following transfection of the reporter construct into MCF-7 cells and treatment with different growth factors. Values were equalised with internal control and Renilla luciferase activity and expressed as a percentage of promoter only (set at 100%). The data shown represent means ± SD from at least three independent experiments. NGF, nerve growth factor; EGF, epidermal growth factor; IGF, insulin-like growth factor; TGF, transforming growth factor; cAMP, cyclic adenosine monophosphate. (b) Schematic showing the position of growth factor response element (EGRF) and serum response element (SRE) sites in the Brn-3b promoter. The location of two Sma1 restriction enzyme sites, which were used to generate the deletion (Sma1/Sma1) construct, BS-SS, is shown in relation to the DNA binding sites. The resultant truncated promoter is represented schematically below. (c) Luciferase activity of intact (BS) promoter (control) or Sma1/Sma1 deletion promoter (BS-SS) is shown following transfection into MCF-7 cells. Grey bars represent WT promoter activity either alone or following treatment with NGF or EGF, whereas stippled bars show the activity of the Sma1/Sma1 deletion construct with or without growth factors. Values represent means ± SE of three independent experiments.