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Interferon regulatory factor 1 is required for mouse Gbp gene activation by gamma interferon.

ABSTRACT: Full-scale transcriptional activation of the mouse Gbp genes by gamma interferon (IFN-gamma) requires protein synthesis in embryonic fibroblasts. Although the Gbp-1 and Gbp-2 promoters contain binding sites for transcription factors Stat1 and IFN regulatory factor 1 (IRF-1), deletion analysis revealed that the Stat1 binding site is dispensable for IFN-gamma inducibility of Gbp promoter constructs in transfected fibroblasts. However, activation of the mouse Gbp promoter by IFN-gamma requires transcription factor IRF-1. Transient overexpression of IRF-1 cDNA in mouse fibroblasts resulted in high-level expression of Gbp promoter constructs. Unlike wild-type cells, IRF-1% embryonic stem cells lacking functional transcription factor IRF-1 contained very low levels of Gbp transcripts that were not increased in response to differentiation or treatment with IFN-gamma. Treatment of IRF-1% mice with IFN-gamma resulted in barely detectable levels of Gbp RNA in spleens, lungs, and livers, whereas such treatment induced high levels of Gbp RNA in the organs of wild-type mice. These observations suggest two alternative pathways for transcriptional induction of genes in response to IFN-gamma: immediate response that results from activation of preformed Stat1 and delayed response that results from induced de novo synthesis of transcription factor IRF-1.

SUBMITTER: Briken V

PROVIDER: S-EPMC231988 | biostudies-other | 1995 Feb

REPOSITORIES: biostudies-other

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Interferon regulatory factor 1 is required for mouse Gbp gene activation by gamma interferon.

Briken V V Ruffner H H Schultz U U Schwarz A A Reis L F LF Strehlow I I Decker T T Staeheli P P

Molecular and cellular biology 19950201 2

Full-scale transcriptional activation of the mouse Gbp genes by gamma interferon (IFN-gamma) requires protein synthesis in embryonic fibroblasts. Although the Gbp-1 and Gbp-2 promoters contain binding sites for transcription factors Stat1 and IFN regulatory factor 1 (IRF-1), deletion analysis revealed that the Stat1 binding site is dispensable for IFN-gamma inducibility of Gbp promoter constructs in transfected fibroblasts. However, activation of the mouse Gbp promoter by IFN-gamma requires tran ...[more]

PMID: 7823961

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Project description:Interferon regulatory factor 8 (IRF8), a myeloid lineage transcription factor, emerges as an essential regulator for microglial activation. However, the precise role of IRF8 during Japanese encephalitis virus (JEV) infection in the brain remains elusive. Here, we report that JEV infection enhances IRF8 expression in the infected mouse brain. Comparative transcriptional profiling of whole-brain RNA analysis and validation by quantitative reverse transcription-PCR (qRT-PCR) reveals an impaired interferon gamma (IFN-γ) and related gene expression in Irf8 knockout (Irf8-/-)-infected mice. Further, Ifnγ knockout (Ifnγ-/-) mice exhibit a reduced level of Irf8. Both Ifnγ-/- and Irf8-/- mice exhibit significantly reduced levels of activated (CD11b+ CD45hi, CD11b+ CD45lo, Cd68, and CD86) and infiltrating immune cells (Ly6C+, CD4, and CD8) in the infected brain compared to those of wild-type (WT) mice. However, a higher level of granulocyte cell (Ly6G+) infiltration is evident in Irf8-/- mice as well as the increased concentration of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein 1 (MCP1) levels in the brain. Interestingly, neither the Irf8-/- nor the Ifnγ-/- conferred protection against lethal JEV challenge to mice and exhibit augmentation in JEV replication in the brain. The gain of function of Irf8 by overexpressing functional IRF8 in an IRF8-deficient cell line attenuates viral replication and enhances IFN-γ production. Overall, we summarize that in the murine model of JEV encephalitis, IRF8 modulation affects JEV replication. We also show that lack of Irf8 affects immune cell abundance in circulation and the infected brain, leading to a reduction in IFN-γ level and increased viral load in the brain. IMPORTANCE Microglial cells, the resident macrophages in the brain, play a vital role in Japanese encephalitis virus (JEV) pathogenesis. The deregulated activity of microglia can be lethal for the brain. Therefore, it is crucial to understand the regulators that drive microglia phenotype changes and induce inflammation in the brain. Interferon regulatory factor 8 (IRF8) is a myeloid lineage transcription factor involved in microglial activation. However, the impact of IRF8 modulation on JEV replication remains elusive. Moreover, the pathways regulated by IRF8 to initiate and amplify pathological neuroinflammation are not well understood. Here, we demonstrated the effect of IRF8 modulation on JEV replication, microglial activation, and immune cells infiltration in the brain.

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Interferon regulatory factor 1 is required for mouse Gbp gene activation by gamma interferon.

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Interferon regulatory factor 1 is required for mouse Gbp gene activation by gamma interferon.

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