Analysis of a pair of ENDsup(+) and ENDsup(-) viruses derived from the same bovine viral diarrhea virus stock reveals the amino acid determinants in Nsup(pro) responsible for inhibition of type I interferon production
2015
Kozasa, T. ((Food Safety and Consumer Affairs Bureau, Ministry of Agriculture, Forestry and Fisheries, Chiyoda-ku, Tokyo (Japan)), (National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, Kokubunji, Tokyo (Japan))) | Abe, Y. | Mitsuhashi, K. | Tamura, T. | Aoki, H. | Ishimaru, M. | Nakamura, S. | Okamatsu, M. | Kida, H. | Sakoda, Y.
The Exaltation of Newcastle disease virus (END) phenomenon is induced by the inhibition of type I interferon in pestivirus-infected cells in vitro, via proteasomal degradation of cellular interferon regulatory factor (IRF)-3 with the property of the viral autoprotease protein Nsup(pro). Reportedly, the amino acid residues in the zinc-binding TRASH motif of Nsup(pro) determine the difference in characteristics between END-phenomenon-positive (ENDsup(+)) and END-phenomenon-negative (ENDsup(-)) classical swine fever viruses (CSFVs). However, the basic mechanism underlying this function in bovine viral diarrhea virus (BVDV) has not been elucidated from the genomic differences between ENDsup(+) and ENDsup(-) viruses using reverse genetics till date. In the present study, comparison of complete genome sequences of a pair of ENDsup(+) and ENDsup(-) viruses isolated from the same virus stock revealed that there were only four amino acid substitutions (D136G, I2623V, D3148G and D3502Y) between two viruses. Based on these differences, viruses with and without mutations at these positions were generated using reverse genetics. The END assay, measurements of induced type I interferon and IRF-3 detection in cells infected with these viruses revealed that the aspartic acid at position 136 in the zinc-binding TRASH motif of Nsup(pro) was required to inhibit the production of type I interferon via the degradation of cellular IRF-3, consistently with CSFV.
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