[A basic leucine zipper transcription factor that is highly homologous to ACTIVATING TRANSCRIPTION FACTOR 2. It binds the consensus site TGACGTCA of the cyclic AMP response element in partnership with either PROTO-ONCOGENE PROTEINS C-JUN or activating transcription factor 2. ( MSH )] (UMLS (CSP) C0213709) =Amino Acid, Peptide, or Protein; Biologically Active Substance