Conserved Ets transcription factor binding sites are required for promoter activity. (A) Nucleotide sequence alignment of the promoter region (E3) with conserved Ets binding sites marked in black (1-4) and other conserved sequence blocks in gray. (B) Shown on the left are the reporter constructs of human wild-type and mutated E3 fragments inserted upstream of the promoterless pGL2basic vector. The conserved Ets binding sites are represented as circles numbered 1-4 and are crossed out where mutated. Shown on the right are the results of stable transfection assays in MS1 cells corresponding to each construct. The luciferase activities are given as fold increases over the activity of the basic (pGL2B) vector. Each bar is the mean of the relative luciferase activity from at least 2 experiments performed in triplicate ± SD.