Activity of the –8 core enhancer requires conserved Ets transcription factor binding sites. (A) Nucleotide sequence alignment of the –8 enhancer (E1) 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 E1 fragments inserted upstream of the SV promoter of the pGL2p vector. As in Figure 3, the conserved Ets binding sites are represented as circles numbered 1-4 and are crossed out where mutated. The constructs were stably transfected into MS1 cells and the results are shown on the right. The luciferase activities are given as fold increases over the activity of the pGL2p vector and represent the mean results of at least 2 experiments performed in triplicate ± SD. (C) Shown on the left are reporter constructs of wild-type and mutated E1 fragments inserted upstream of the wild-type and mutated promoter (E3) fragment. The constructs were stably transfected into MS1 cells, and the results are shown on the right. The luciferase activities are given as fold increases over the activity of the construct with mutation of all Ets binding sites in E1 and E3.