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Journal of Virology, August 1999, p. 6335-6345, Vol. 73, No. 8
Department of Virology,
Received 24 November 1998/Accepted 12 April 1999
Arteriviruses are positive-stranded RNA viruses with an efficiently
organized, polycistronic genome. A short region between the replicase
gene and open reading frame (ORF) 2 of the equine arteritis virus (EAV)
genome was previously assumed to be untranslated. However, here we
report that this segment of the EAV genome contains the 5' part of a
novel gene (ORF 2a) which is conserved in all arteriviruses. The 3'
part of EAV ORF 2a overlaps with the 5' part of the former ORF 2 (now
renamed ORF 2b), which encodes the GS glycoprotein. Both
ORF 2a and ORF 2b appear to be expressed from mRNA 2, which thereby
constitutes the first proven example of a bicistronic mRNA in
arteriviruses. The 67-amino-acid protein encoded by EAV ORF 2a, which
we have provisionally named the envelope (E) protein, is very
hydrophobic and has a basic C terminus. An E protein-specific antiserum
was raised and used to demonstrate the expression of the novel gene in
EAV-infected cells. The EAV E protein proved to be very stable, did not
form disulfide-linked oligomers, and was not N-glycosylated.
Immunofluorescence and immunoelectron microscopy studies showed that
the E protein associates with intracellular membranes both in
EAV-infected cells and upon independent expression. An analysis of
purified EAV particles revealed that the E protein is a structural
protein. By using reverse genetics, we demonstrated that both the
EAV E and GS proteins are essential for the production of
infectious progeny virus.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Identification of a Novel Structural Protein
of Arteriviruses
*
Corresponding author. Mailing address: Department of
Virology, Leiden University Medical Center, LUMC P4-26, P.O. Box 9600, 2300 RC Leiden, The Netherlands. Phone: 31 71 5261657. Fax: 31 71 5266761. E-mail: Snijder{at}Virology.AZL.NL.
Present address: Center for Biotechnology (CBT), Department of
Biosciences at Novum, Karolinska Institutet, 14157 Huddinge, Sweden.
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