Toll-like receptor-dependent and -independent viperin gene expression and counter-regulation by PRDI-binding factor-1/BLIMP1
Department of Medicine, Division of Infectious Diseases and Immunology
Adaptor Proteins, Vesicular Transport; Animals; Cells, Cultured; Dendritic Cells; *Gene Expression Regulation; Genes, Reporter; Humans; Interferon Regulatory Factor-3; Interferon-Stimulated Gene Factor 3; Macrophages; Mice; Mice, Inbred C57BL; Mice, Knockout; Myeloid Differentiation Factor 88; Promoter Regions (Genetics); Proteins; Receptors, Interleukin; Repressor Proteins; Toll-Like Receptors; Transcription Factors; Transcription, Genetic
Immunology and Infectious Disease | Life Sciences | Medicine and Health Sciences
Here we identify Viperin as a highly inducible gene in response to lipopolysaccharide (LPS), double-stranded RNA (poly(I-C)) or Sendai virus (SV). The only known function of Viperin relates to its ability to inhibit human Cytomegalovirus replication. Very little data are available on the regulation of this gene. In silico analysis of the promoter identified two interferon (IFN)-stimulated response elements (ISRE), which in other genes bind IRF3 or the IFN-stimulated gene factor-3 (ISGF3) complex. LPS and poly(I-C) induce very high levels of Viperin in wild type cells but not in cells deficient in TRIF, TBK1, IRF3, or the type I IFNalpha/betaR. SV-induced Viperin gene expression was mediated independently of Toll-like receptor (TLR) signaling by retinoic acid-inducible gene (RIG-I) and the downstream adapter, mitochondrial anti-viral signaling (MAVS). Virus-induced Viperin expression was not attenuated in macrophages deficient in either TBK1 or IKKepsilon alone. Moreover, IRF3-deficient, but not IFNalpha/betaR deficient, macrophages still induced Viperin in response to SV. Promoter reporter studies combined with DNA immunoprecipitation assays identified the ISGF3 complex as the key regulator of Viperin gene expression. Moreover, positive regulatory domain I-binding factor 1 (PRDI-BF1, also called BLIMP1) binds the ISRE sites and competes with ISGF3 binding in a virus inducible manner to inhibit Viperin transcription. Collectively, these studies identify Viperin as a tightly regulated ISGF3 target gene, which is counter-regulated by PRDI-BF1.
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Citation: J Biol Chem. 2006 Sep 8;281(36):26188-95. Epub 2006 Jul 18. Link to article on publisher's site