Journal of Biological Chemistry · 2004 · 135 citations · 50 references
Life SciencesBiologyMolecular BiologyMolecular VirologyTranscriptionVirologyRna Polymerase FunctionRna Polymerase Ii TranscriptionRna Polymerase RegulationRna-protein InteractionsViral Rna BiologyViral TranscriptionInterferon Response To Viral InfectionRna Polymerase Ii ActivationViral Polymerase InhibitorsViral Rna Interferon AntagonismViral Rna-protein Interactions
Many viruses subvert the cellular interferon (IFN) system with so-called IFN antagonists.Bunyamwera virus (BUNV) belongs to the family Bunyaviridae and is transmitted by arthropods.We have recently identified the nonstructural protein NSs of BUNV as a virulence factor that inhibits IFN- gene expression in the mammalian host.Here, we demonstrate that NSs targets the RNA polymerase II (RNAP II) complex.The C-terminal domain (CTD) of RNAP II consists of 52 repeats of the consensus sequence YSPTSPS.Phosphorylation at serine 5 is required for efficient initiation of transcription, and subsequent phosphorylation at serine 2 is required for mRNA elongation and 3-end processing.In BUNVinfected mammalian cells, serine 5 phosphorylation occurred normally.Furthermore, RNAP II was able to bind to the IFN- gene promoter as revealed by chromatin immunoprecipitation analysis, indicating that the initiation of transcription was not disturbed by NSs.However, NSs prevented CTD phosphorylation at serine 2, suggesting a block in transition from initiation to elongation.Surprisingly, no interference with CTD phosphorylation was observed in insect cells.Our results indicate that BUNV uses an unconventional mechanism to block IFN synthesis in the mammalian host by directly dysregulating RNAP II.Moreover, by inducing a general transcriptional block, NSs may contribute to the lytic infection observed in mammalian cells as opposed to persistent infection in the insect host./ interferons (IFN-/) 1 play a key role in host defense against invading viruses (1).The induction of IFN gene expression is best understood for IFN-.The IFN- promoter has binding sites for the stress-activated transcription factors NF-B and AP-1 and for the IFN regulatory factors IRF-3 and IRF-7.These factors normally reside in the cytoplasm.Upon activation by virus infection or double-stranded RNA, they move to the nucleus and associate with RNA polymerase II (RNAP II) to initiate transcription of the IFN- gene (2, 3).
50