CREM is a a bZIP transcription factor that binds to the cAMP responsive element found in many viral and cellular promoters. It is derived from a multiexonic gene that encodes both activators and antagonists of cAMP-inducible transcription by differential splicing. Splice variants with antagonistic function lack 2 glutamine-rich domains and block cAMP-induced transcription, whereas an isoform that includes these glutamine-rich domains is a transcriptional activator.