TRANSCRIPTIONAL REGULATION BY CYCLIC-AMP

A number of hormones and growth factors have been shown to stimulate t arget cells via second messenger pathways that in turn regulate the ph osphorylation of specific nuclear factors, The second messenger cyclic AMP, for example, regulates a striking number of physiologic processe s, including intermediary metabolism, cellular proliferation, and neur onal signaling, by altering basic patterns of gene expression. Our und erstanding of cyclic AMP signaling in the nucleus has expanded conside rably over the past decade, owing in large part to the characterizatio n of cyclic AMP-responsive promoter elements, transcription factors th at bind them, and signal-dependent coactivators that mediate target ge ne induction. More importantly, these studies have revealed new insigh ts into biological problems as diverse as biological clocks and long-t erm memory. The purpose of this review is to describe the components o f the cyclic AMP response unit and to analyze how these components coo perate to induce target gene expression in response to hormonal stimul ation.