Effect of E1A-13S or E1A-d30-76 proteins on the activity of the K18 promoter. SW613-3 (T) or SW613-B3 (NT) cells were transfected with plasmid pK18(80)luc (A) or plasmid pK18(41)luc (B) alone (none) or in the presence of plasmid pE1A-13S or pE1A-d30-76, as indicated. Luciferase activities are expressed relative to that obtained with the reporter plasmid alone for each cell clone. Error bars represent the standard deviation of the mean of two experiments. (C) Structure of the promoter of the human K18 gene. The binding site of the Sp1 transcription factor, the initiation site (arrow at position -11; we have shown that the initiation is located 11 bp upstream of previously published +1 position ) and the TATA box are indicated. Numbers indicate positions in nucleotides. K18(80) and K18(41), the two forms of the promoter inserted into luciferase expression vectors are shown.