ATF4 is a transcription factor that was originally identified as a widely expressed mammalian DNA binding protein that could bind a tax-responsive enhancer element in the LTR of HTLV1. The encoded protein was also isolated and characterized as the cAMP-response element binding protein 2 (CREB2). The protein encoded by this gene belongs to a family of DNA-binding proteins that includes the AP1 family of transcription factors, cAMP-response element binding proteins (CREBs) and CREB-like protein