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 (By similarity). Homodimer. 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). Interacts with CREB1; the interaction is not depolarization dependent. Interacts with CREBBP (via C-terminus) (By similarity). the C-terminus is required for calcium responsiveness but not for transactivation activity. The N-terminus is absolutely necessary for transactivation activity.