A Kaposi's sarcoma-associated herpesviral protein inhibits virus-mediated induction of type I interferon by blocking IRF-7 phosphorylation and nuclear accumulation.
Interferons constitute the earliest immune response against viral infection. They elicit antiviral effects as well as multiple biological responses involved in cell growth regulation and immune activation. Because the interferon-induced cellular antiviral response is the primary defense mechanism against viral infection, many viruses have evolved strategies to antagonize the inhibitory effects of interferon. Here, we demonstrate a strategy that Kaposi's sarcoma-associated herpesvirus uses to block virus-mediated induction of type I interferon. We found that a viral immediate-early protein, namely ORF45, interacts with cellular interferon-regulatory factor 7 (IRF-7). In consequence, IRF-7 phosphorylation is inhibited and the accumulation of IRF-7 in the nucleus in response to viral infection is blocked. IRF-7 is a transcription regulator that is responsible for virus-mediated activation of type I interferon genes. By blocking the phosphorylation and nuclear translocation of IRF-7, ORF45 efficiently inhibits the activation of interferon alpha and beta genes during viral infection. Inhibition of interferon gene expression through a viral protein blocking the activation and nuclear translocation of a crucial transcription factor is a novel mechanism for viral immune evasion.
Zhu
Fan Xiu
FX
Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104, USA.
King
Sonya M
SM
Smith
Eric J
EJ
Levy
David E
DE
Yuan
Yan
Y
D021581:Active Transport, Cell Nucleus; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins; D019288:Herpesvirus 8, Human / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D050839:Interferon Regulatory Factor-7; D007370:Interferon Type I / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016366:Open Reading Frames; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029082:Sendai virus / Q000378:metabolism; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000737:chemistry* / Q000502:physiology*
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C494234:IRF7 protein, human; D017874:Immediate-Early Proteins; D050839:Interferon Regulatory Factor-7; D007370:Interferon Type I; D008164:Luminescent Proteins; C456286:ORF45 protein, Kaposi's sarcoma-associated herpesvirus; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D049452:Green Fluorescent Proteins; D008156:Luciferases; D005982:Glutathione Transferase