Basic leucine zipper (bZIP) domain of blue light (BL) receptor aureochrome (AUREO) and similar bZIP domains
AUREO is a BL-activated transcription factor specific to phototrophic stramenopiles. It has a bZIP and a BL-sensing light-oxygen voltage (LOV) domain. It has been shown to mediate BL-induced branching and regulate the development of the sex organ in Vaucheria frigida. 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. This subgroup also includes the Epstein-Barr virus (EBV) immediate-early transcription factor ZEBRA (BZLF1, Zta, Z, EB1). ZEBRA exhibits a variant of the bZIP fold, it has a unique dimer interface and a substantial hydrophobic pocket; it has a C-terminal moiety which stabilizes the coiled coil involved in dimer formation. ZEBRA functions to trigger the switch of EBV's biphasic infection cycle from latent to lytic infection. It activates the promoters of EBV lytic genes by binding ZEBRA response elements (ZREs) and inducing a cascade of expression of over 50 viral genes. It also down regulates latency-associated promoters, is an essential replication factor, induces host cell cycle arrest, and alters cellular immune responses and transcription factor activity.
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