Binding of steroid receptors to the HREs of mouse mammary tumor virus, chicken and xenopus vitellogenin and rabbit uteroglobin genes: correlation with induction.

Binding to hormone responsive elements (HRE) is an essential step in gene regulation by steroid hormones. Using a combination of in vivo and in vitro studies we have analyzed the interactions of the estrogen receptor with genes from three different systems: the long terminal repeat (LTR) of the mouse mammary tumor virus (MMTV), the chicken and xenopus vitellogenin genes and the rabbit uteroglobin gene. The estrogen receptor binds to all four genes in vitro, but the MMTV LTR does not respond to estrogen in gene transfer experiments. Similarly, the xenopus vitellogenin gene binds the progesterone and glucocorticoid receptors in vitro, but only estrogen induces the xenopus vitellogenin gene in gene transfer. These results suggest that events distal to DNA binding are essential for transcriptional activation, and that the function of the HRE is not simply to position the hormone receptor in the vicinity of the regulated promoter.