Transcriptional coactivator of the p300/CBP-mediated transcription complex. Activates transactivation through cAMP response element (CRE) sites. Protects against cell death by inducing antiapoptotic and repressing pro-apoptotic transcripts. Stimulates transcription from the estrogen-responsive or BCL-2 promoters. Required for depolarization-induced transcription activation of the C-FOS promoter in neurons. Associates with chromatin to the estrogen-responsive C3 promoter region. Homodimer. Interacts with CREB1; the interaction is not depolarization dependent. Interacts with CREBBP (via C-terminus) (By similarity). Interacts (via HGM box) with CITED1 (via C-terminus); the interaction increases estrogen-response element (ERE)-dependent transcription and protection against cell death. Interacts with CREB1 (phosphorylated form). Expressed mainly in epithelial cells. Expressed in the central nervous system (CNS), in the ileum and within the brain in the frontal and occipital lobe. Up-regulated by GPR39 in neuronal cells. the C-terminus is required for calcium responsiveness but not for transactivation activity. The N-terminus is absolutely necessary for transactivation activity.