Inhibition of RNA polymerase II phosphorylation by a viral interferon antagonist.
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-beta 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 BUNV-infected mammalian cells, serine 5 phosphorylation occurred normally. Furthermore, RNAP II was able to bind to the IFN-beta 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.
Thomas
Daniel
D
Abteilung Virologie, Institut für Medizinische Mikrobiologie und Hygiene, Universität Freiburg, D-79008 Freiburg, Germany.
Blakqori
Gjon
G
Wagner
Valentina
V
Banholzer
Marius
M
Kessler
Nina
N
Elliott
Richard M
RM
Haller
Otto
O
Weber
Friedemann
F
D000818:Animals; D002042:Bunyamwera virus / Q000472:pathogenicity*; D002460:Cell Line; D002522:Chlorocebus aethiops; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D016899:Interferon-beta / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000494:pharmacology*
C423923:NSs protein, Bunyamwera bunyavirus; D017361:Viral Nonstructural Proteins; D016899:Interferon-beta; D012319:RNA Polymerase II