title: STAT1-independent cell type-specific regulation of antiviral APOBEC3G by IFN-alpha.
abstract: APOBEC3G (A3G) has broad antiviral activity against retroviruses and hepatitis B virus. However, the role of IFNs in regulating A3G during innate immunity has not been established. In this study, we show that the A3G gene is uniquely regulated by IFNs in a cell type-dependent manner. A3G was up-regulated by IFN-alpha in liver cells and macrophages, but not in T lymphoid cells or epithelial 293T cells. In contrast, other IFN-alpha-stimulated genes such as dsRNA-activated protein kinase were induced in all these cells, suggesting additional cellular factors may regulate IFN-alpha-induced A3G expression. Consistent with this idea, IFN-alpha-mediated induction of A3G, but not other IFN-alpha-stimulated genes, was potently inhibited by the drug Rottlerin, through a mechanism independent of STAT1 activation. The canonical IFN-alpha-mediated pathway of gene transcription requires both STAT1 and STAT2. Surprisingly, induction of A3G was STAT1 independent, but STAT2 dependent in liver cells. However, STAT1 signaling was functional and required for IFN-gamma induction of A3G in these cells. Our results indicate that A3G may participate in antiviral cellular defenses through a novel IFN-mediated signaling pathway.
authors.affiliation: Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA.
authors.forename: Phuong Thi Nguyen
authors.initials: PT
authors.lastname: Sarkis
authors.forename: Songcheng
authors.initials: S
authors.lastname: Ying
authors.forename: Rongzhen
authors.initials: R
authors.lastname: Xu
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Yu
mesh_terms: D000071480:APOBEC-3G Deaminase; D000098:Acetophenones / Q000494:pharmacology; D001578:Benzopyrans / Q000494:pharmacology; D002478:Cells, Cultured; D003564:Cytidine Deaminase; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism; D022781:Hepatocytes / Q000276:immunology / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D016898:Interferon-alpha / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D018448:Models, Immunological; D009700:Nucleoside Deaminases / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D012097:Repressor Proteins / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D050795:STAT2 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014780:Viruses / Q000276:immunology*
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D004791:Enzyme Inhibitors; D016898:Interferon-alpha; D012097:Repressor Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050795:STAT2 Transcription Factor; C085746:rottlerin; D009700:Nucleoside Deaminases; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase