3qu3 | pdb_00003qu3
Crystal structure of IRF-7 DBD apo form
Structural highlights
Function[IRF7_MOUSE] Key transcriptional regulator of type I interferon (IFN)-dependent immune responses and plays a critical role in the innate immune response against DNA and RNA viruses. Regulates the transcription of type I IFN genes (IFN-alpha and IFN-beta) and IFN-stimulated genes (ISG) by binding to an interferon-stimulated response element (ISRE) in their promoters. Can efficiently activate both the IFN-beta (IFNB) and the IFN-alpha (IFNA) genes and mediate their induction via both the virus-activated, MyD88-independent pathway and the TLR-activated, MyD88-dependent pathway. Required during both the early and late phases of the IFN gene induction but is more critical for the late than for the early phase. Exists in an inactive form in the cytoplasm of uninfected cells and following viral infection, double-stranded RNA (dsRNA), or toll-like receptor (TLR) signaling, becomes phosphorylated by IKBKE and TBK1 kinases. This induces a conformational change, leading to its dimerization and nuclear localization where along with other coactivators it can activate transcription of the type I IFN and ISG genes. Can also play a role in regulating adaptive immune responses by inducing PSMB9/LMP2 expression, either directly or through induction of IRF1. Binds to the Q promoter (Qp) of EBV nuclear antigen 1 a (EBNA1) and may play a role in the regulation of EBV latency. Can activate distinct gene expression programs in macrophages and regulate the anti-tumor properties of primary macrophages.[1] [2] [3] [4] Publication Abstract from PubMedInterferon regulatory factors IRF-3 and IRF-7 are transcription factors essential in the activation of interferon-beta (IFN-beta) gene in response to viral infections. Although, both proteins recognize the same consensus IRF binding site AANNGAAA, they have distinct DNA binding preferences for sites in vivo. The X-ray structures of IRF-3 and IRF-7 DNA binding domains (DBDs) bound to IFN-beta promoter elements revealed flexibility in the loops (L1-L3) and the residues that make contacts with the target sequence. To characterize the conformational changes that occur on DNA binding and how they differ between IRF family members, we have solved the X-ray structures of IRF-3 and IRF-7 DBDs in the absence of DNA. We found that loop L1, carrying the conserved histidine that interacts with the DNA minor groove, is disordered in apo IRF-3 but is ordered in apo IRF-7. This is reflected in differences in DNA binding affinities when the conserved histidine in loop L1 is mutated to alanine in the two proteins. The stability of loop L1 in IRF-7 derives from a unique combination of hydrophobic residues that pack against the protein core. Together, our data show that differences in flexibility of loop L1 are an important determinant of differential IRF-DNA binding. Structures of apo IRF-3 and IRF-7 DNA binding domains: effect of loop L1 on DNA binding.,De Ioannes P, Escalante CR, Aggarwal AK Nucleic Acids Res. 2011 May 19. PMID:21596780[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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