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Basic leucine zipper (bZIP) domain of CCAAT/enhancer-binding protein delta (CEBPD): a DNA-binding and dimerization domain CEBPD is an inflammatory response gene that is induced by Toll-like receptor 4 (TLR4) and is essential in the expression of many lipopolysaccharide (LPS)-induced genes and the clearance of bacterial infection. Its expression is increased in response to various extracellular stimuli and it induces growth arrest and apoptosis in cancer cells. It is thought to function as a tumor suppressor and its expression is found reduced by site-specific methylation in many cancers including breast, cervical, and hepatocellular carcinoma. CEBPs (or C/EBPs) are Basic leucine zipper (bZIP) transcription factors that regulate many cellular processes. There are six CEBP proteins in mammalian cells including CEBPA (alpha), CEBPB (beta), CEBPG (gamma), CEBPD (delta), and CEBPE (epsilon), which all contain highly conserved bZIP domains at their C-termini and variations at their N-terminal regions. 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.
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