Glucocorticoid receptor-cAMP response element-binding protein interaction and the response of the phosphoenolpyruvate carboxykinase gene to glucocorticoids.

The phosphoenolpyruvate carboxykinase (PEPCK) gene encodes the rate-limiting enzyme in gluconeogenesis. Glucocorticoids enhance PEPCK gene expression through a multicomponent regulatory complex. We show that a full response to glucocorticoids requires two DNA segments: 1) a glucocorticoid response unit (GRU), centered at about position -400, which contains two accessory factor elements (AF1 and AF2) and two glucocorticoid receptor binding sites (GR1 and GR2), and 2) a basal promoter/cyclic AMP response element (E/CRE) at about position -90, which binds the transcription factor CREB. A protein-protein interaction was observed in vitro between GR and CREB that might account for the role of the E/CRE in the glucocorticoid response of the PEPCK gene.