Transcription factor that may act during endoplasmic reticulum (ER) stress by activating unfolded protein response target genes. Activated in response to cAMP stimulation. Binds to the cAMP response element (CRE). Activates transcription through box-B element. Activates transcription through CRE. May function synergistically with ATF6. In acute inflammatory response, may activate expression of acute phase response (APR) genes. May be involved in growth suppression. Regulates FGF21 transcription. Plays a crucial role in the regulation of triglyceride metabolism and is required for the maintenance of normal plasma triglyceride concentrations