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Basic leucine zipper (bZIP) domain of Nuclear factor interleukin-3-regulated protein (NFIL3): a DNA-binding and dimerization domain NFIL3, also called E4 promoter-binding protein 4 (E4BP4), is a Basic leucine zipper (bZIP) transcription factor that was independently identified as a transactivator of the IL3 promoter in T-cells and as a transcriptional repressor that binds to a DNA sequence site in the adenovirus E4 promoter. Its expression levels are regulated by cytokines and it plays crucial functions in the immune system. It is required for the development of natural killer cells and CD8+ conventional dendritic cells. In B-cells, NFIL3 mediates immunoglobulin heavy chain class switching that is required for IgE production, thereby influencing allergic and pathogenic immune responses. It is also involved in the polarization of T helper responses. 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",