Glucocorticoid and progesterone receptors bind to the same sites in two hormonally regulated promoters.

The glucocorticoid receptor of rat liver recognizes nucleotide sequences near the promoter of mouse mammary tumour virus (MMTV) required for hormonal induction in gene transfer experiments. Similar nucleotide sequences have been found in the human metallothionein gene IIA and in the chicken lysozyme gene, the later induced also by oestrogen, progesterone and androgens. In microinjection experiments, deletion of only 44 base pairs (bp) of the lysozyme promoter (from -208 to -164) results in coordinated loss of progesterone and glucocorticoid-dependent gene expression. We show here that purified glucocorticoid receptor from rat liver and progesterone receptor from rabbit uterus yield similar or overlapping exonuclease III footprints in the promoter regions of MMTV and chicken lysozyme. Thus, the regulatory elements for different steroid hormones may be similar or at least share structural features.