Nuclear localization of the Nipah virus W protein allows for inhibition of both virus- and toll-like receptor 3-triggered signaling pathways.
The Nipah virus V and W proteins, which are encoded by the P gene via RNA editing, have a common N-terminal domain but unique C-terminal domains. They localize to the cytoplasm and nucleus, respectively, and have both been shown to function as inhibitors of JAK/STAT signaling. Here we report that V and W proteins also block virus activation of the beta interferon (IFN-beta) promoter and the IFN regulatory factor 3 (IRF3)-responsive IFN-stimulated gene 54 promoter. Surprisingly, only W protein shows strong inhibition of promoter activation in response to stimulation of Toll-like receptor 3 (TLR3) by extracellular double-stranded RNA. This activity is dependent on the nuclear localization of W protein. Within the unique C-terminal domain of W protein, we have identified a nuclear localization signal (NLS) that requires basic residues at positions 439, 440, and 442. This NLS is responsible for mediating the preferential interaction of W protein with karyopherin-alpha 3 and karyopherin-alpha 4. Nuclear localization of W protein therefore enables it to target both virus and TLR3 pathways, whereas the cytoplasmic V protein is restricted to inhibiting the virus pathway. We propose that this discrepancy is in part due to the V protein being less able to block signaling in response to the kinase, TBK-1, whereas both V and W can prevent promoter activation in response to IKKepsilon. We demonstrate that, when the TLR3 pathway is stimulated, the levels of phosphorylated IRF3 are reduced in the presence of W protein but not V protein, confirming the differential effects of these proteins and illustrating that W protein-mediated inhibition is due to a loss of active IRF3.
Shaw
Megan L
ML
Department of Microbiology, Box 1124, Mount Sinai School of Medicine, One Gustave L. Levy Pl., New York, NY 10029, USA. megan.shaw@mssm.edu
Cardenas
Washington B
WB
Zamarin
Dmitriy
D
Palese
Peter
P
Basler
Christopher F
CF
D000595:Amino Acid Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000821:virology; D004268:DNA-Binding Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D050838:Interferon Regulatory Factor-3; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008969:Molecular Sequence Data; D045405:Nipah Virus / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011991:Receptors, Virus / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction; D051196:Toll-Like Receptor 3; D051193:Toll-Like Receptors; D014157:Transcription Factors / Q000378:metabolism; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication; D028901:alpha Karyopherins / Q000378:metabolism
D004268:DNA-Binding Proteins; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; C106306:KPNA3 protein, human; C106259:KPNA4 protein, human; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011991:Receptors, Virus; C495344:TLR3 protein, human; D051196:Toll-Like Receptor 3; D051193:Toll-Like Receptors; D014157:Transcription Factors; D014764:Viral Proteins; C501252:W protein, Nipah virus; D028901:alpha Karyopherins; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human