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We identified and characterized elements which confer tissue specificity and cyclic AMP (cAMP) responsiveness to the human glycoprotein alpha-subunit gene. An enhancer containing an 18-base-pair repeat conferred cAMP responsiveness in a non-tissue-specific fashion. DNase I protection assays revealed DNA-binding factors that bound to this element in both placental and nonplacental cells. It also enhanced the alpha-subunit promoter in a tissue-specific manner but had a negligible effect on a heterologous promoter. A unique element found upstream of this enhancer had no independent activity but, in combination with the cAMP-responsive enhancer, distinctly increased the tissue-specific activity of both the alpha-subunit promoter and a heterologous promoter. A factor that bound to this upstream element was found in placental but not nonplacental cells. We conclude that this novel element acts, perhaps through a specific trans-acting factor, in concert with a cAMP-responsive enhancer to confer tissue specificity to the alpha-subunit gene.
Delegeane et al. (1987) studied this question.