title: Oestradiol induction of a glucocorticoid-responsive gene by a chimaeric receptor.
abstract: Steroid hormone receptors are a class of cell-specific trans-acting transcription regulatory factors whose activity is controlled by specific binding of the hormone. The hormone-receptor complex appears to associate with promoter/enhancer elements of specific target genes, resulting in activation of transcription (see refs 1 and 2 for reviews). Sequence comparison between the oestrogen, glucocorticoid and progesterone receptors (refs 7, 8 and unpublished results) and site-directed mutation analysis, has identified in each at least two functional domains important for steroid receptor function. Region E (Fig. 1a), is the hormone-binding domain; region C is a 66-amino-acid region (Figs 1a,b) that is more highly conserved than the hormone-binding domain and has the potential to form at least two zinc-stabilized 'DNA-binding fingers' analogous to those proposed for the Xenopus transcription factor TFIIIA. We and others have suggested that this region may be the receptor's DNA-binding domain. We show here that point mutations replacing two cysteines by two histidines in the first potential DNA-binding finger of the human oestrogen receptor (hER) prevent it from activating gene transcription. We further show that a chimaeric receptor formed by replacing this 66-amino-acid region of the hER with that of the human glucocorticoid receptor (hGR) activates expression of a glucocorticoid-inducible gene, but not of an oestrogen-inducible gene, in the presence of oestradiol. Thus, region C determines the receptor's specificity for target genes.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002678:Chimera; D004958:Estradiol / Q000494:pharmacology*; D005470:Fluorometry; D005786:Gene Expression Regulation / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D051379:Mice; D011960:Receptors, Estrogen / Q000235:genetics*; D011965:Receptors, Glucocorticoid / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014981:Xenopus
chemical_list: D005938:Glucocorticoids; D011960:Receptors, Estrogen; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D004958:Estradiol