Molecular interactions of steroid hormone receptor with its enhancer element: Evidence for receptor dimer formation

A steroid hormone responsive element ( GRE PRE), sufficient to confer glucocorticoid and progesterone inducibility when linked to a reporter gene, was used in band-shift assays to examine its molecular interactions with steroid hormone receptors. Both progesterone and glucocorticoid receptors bound directly and specifically to the GRE PRE. The purine contact sites for both form A and form B chicken progesterone receptor, as well as those for rat glucocorticoid receptor, are identical. A peptide fragment produced in bacteria that primarily contain the DNA binding domain of the glucocorticoid receptor binds first to the TGTTCT half-site of the GRE PRE, and a second molecule binds subsequently to the TGTACA (half-site) of the GRE PRE in a cooperative manner. Utilizing the peptide fragment and the protein A-linked fragment, we demonstrated that the receptor interacts with its cognate enhancer as a dimer.