Basic leucine zipper (bZIP) domain of Activating Transcription Factor-4 (ATF-4) and similar proteins: a DNA-binding and dimerization domain
ATF-4 was also isolated and characterized as the cAMP-response element binding protein 2 (CREB2). It is a Basic leucine zipper (bZIP) transcription factor that has been reported to act as both an activator or repressor. It is a critical component in both the unfolded protein response (UPR) and amino acid response (AAR) pathways. Under certain stress conditions, ATF-4 transcription is increased; accumulation of ATF-4 induces the expression of genes involved in amino acid metabolism and transport, mitochondrial function, redox chemistry, and others that ensure protein synthesis and recovery from stress. bZIP factors act in networks of homo and heterodimers in the regulation of a diverse set of cellular processes. The bZIP structural motif contains a basic region and a leucine zipper, composed of alpha helices with leucine residues 7 amino acids apart, which stabilize dimerization with a parallel leucine zipper domain. Dimerization of leucine zippers creates a pair of the adjacent basic regions that bind DNA and undergo conformational change. Dimerization occurs in a specific and predictable manner resulting in hundreds of dimers having unique effects on transcription.