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Journal of Virology, April 2007, p. 3866-3876, Vol. 81, No. 8
0022-538X/07/$08.00+0     doi:10.1128/JVI.02075-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Capsid Protein of Eastern Equine Encephalitis Virus Inhibits Host Cell Gene Expression

Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029,¹ Center for Biodefense and Emerging Infectious Diseases,² Department of Pathology, University of Texas Medical Branch, Galveston, Texas 77555-0609³

Received 21 September 2006/ Accepted 18 January 2007

Eastern equine encephalitis virus (EEEV) causes sporadic but often severe cases of human and equine neurological disease in North America. To determine how EEEV may evade innate immune responses, we screened individual EEEV proteins for the ability to rescue the growth of a Newcastle disease virus expressing green fluorescent protein (NDV-GFP) from the antiviral effects of interferon (IFN). Only expression of the EEEV capsid facilitated NDV-GFP replication. Inhibition of the antiviral effects of IFN by the capsid appears to occur through a general inhibition of cellular gene expression. For example, the capsid inhibited the expression of several reporter genes under the control of RNA polymerase II promoters. In contrast, capsid did not inhibit expression from a T7 RNA polymerase promoter construct, suggesting that the inhibition of gene expression is specific and is not a simple manifestation of toxicity. The inhibition correlated both with capsid-induced phosphorylation of eukaryotic initiation factor 2 alpha and with capsid-mediated inhibition of cellular mRNA accumulation. Mapping analysis identified the N terminus as the region important for the inhibition of host gene expression, suggesting that this inhibition is independent of capsid protease activity. Finally, when cell lines containing EEEV replicons encoding capsid were selected, replicons consistently acquired mutations that deleted all or part of the capsid, for example, amino acids 18 to 135. Given that the amino terminus of the capsid is required to inhibit host cell gene expression, these data suggest that capsid expression from the replicons is ultimately toxic to host cells, presumably because of its ability to inhibit gene expression.

Published ahead of print on 31 January 2007.

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