This protein binds the cAMP response element (CRE) (consensus: 5'-GTGACGT[AC][AG]-3'), a sequence present in many viral and cellular promoters. Represses transcription from promoters with ATF sites. It may repress transcription by stabilizing the binding of inhibitory cofactors at the promoter. Activates transcription presumably by sequestering inhibitory cofactors away from the promoters. Stress-induced isoform, counteracts the transcriptional repression of isoform 1. Binds DNA as a homodimer or a heterodimer. Interacts with KAT5; promoting KAT5 autoacetylation and KAT5 deubiquitination by USP7 (PubMed:25865756). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the bZIP family. ATF subfamily.