Activating transcription factor 3 ( ATF3 ) is an adaptive-response gene that participates in cellular processes to adapt to extra- and/or intra-cellular changes, where it transduces signals from various receptors to activate or repress gene expression, depending on the promoter and cellular context. It is a member of the ATF/cyclic AMP response element-binding ( ATF/CREB ) family of transcription factors, which has a extensive transcriptional regulation. ATF3 plays an important role in cell cycle, immunoloregulation, endocrine regulation and tumorigenicity.