Estrogen-responsive element of the human pS2 gene is an imperfectly palindromic sequence.

Using chimeric recombinants transfected into HeLa cells and a transient expression assay, we demonstrate that the 5'-flanking region of the pS2 gene from position -428 to position -324 exhibits both constitutive and estrogen-inducible enhancer activity. The estrogen-inducible activity, but not the constitutive activity, was inhibited by antiestrogens. ICI 164,384 behaved as a pure antagonist, whereas hydroxytamoxifen was a partial agonist-antagonist. The estrogen-responsive element of the pS2 gene has been narrowed down by site-directed deletion mutagenesis to a 13-base-pair (position -405 to position -393) imperfectly palindromic sequence, which in isolation can confer estrogen inducibility to the heterologous rabbit beta-globin gene promoter. On the other hand, the sequences responsible for the constitutive enhancer activity are spread over the entire region.