Glucocorticoids Stimulate CREB Binding to a Cyclic-AMP Response Element in the Rat Serine Dehydratase Gene

Transcription of the rat serine dehydratase (SDH) gene, which is stimulated in hepatocytes by glucagon through the activity of the second messenger, cAMP, is augmented by pretreatment with glucocorticoids. A putative cAMP response element (CRE) located approximately 3.5 kbp upstream of the transcriptional start site was hypothesized to be responsible for this effect. Here we have demonstrated by DNaseI footprinting and site-directed mutagenesis that the phosphorylated cAMP response element binding protein (CREB) binds to a cAMP response element different from that described previously. While the amount of CREB in the extracts is unaltered by hormone treatment, more CREB is capable of binding the response element upon addition of dexamethasone (Dex). These studies suggest that synergistic induction of the SDH gene by cAMP and Dex is through a CRE and is due, in part, to regulation of CREB–DNA binding by treatment of the cells with glucocorticoids.