Regulatory elements of the pro-opiomelanocortin gene: pituitary specificity and glucocorticoid repression

A short 543-bp fragment o f the pro-opiomelanocortin gene is sufficient for pituitary-specific expression and, in the anterior pituitary gland, for repression of pro-opiomelanocortin transcription by glucocorticoids. Within this 5'-flanking fragment of the gene, multiple regulatory elements contribute to tissue-specific expression and a single glucocorticoid receptor binding site acts as a "negative glucocorticoid response element." The current model for glucocorticoid repression depends on the mutually exclusive binding of the glucocorticoid receptor and of a positive transcription factor, the chicken ovalbumin upstream promoter element transcription factor, to overlapping DNA sequences within the negative glucocorticoid response element.