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Journal of Virology, January 2007, p. 718-731, Vol. 81, No. 2
0022-538X/07/$08.00+0 doi:10.1128/JVI.01691-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
The ORF7b Protein of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) Is Expressed in Virus-Infected Cells and Incorporated into SARS-CoV Particles
Scott R. Schaecher,1
Jason M. Mackenzie,3 and
Andrew Pekosz1,2*
Departments of Molecular Microbiology,1
Pathology and Immunology, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, Missouri 63110-1093,2
School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland, Australia 40723
Received 4 August 2006/
Accepted 16 October 2006
Coronavirus replication is facilitated by a number of highly conserved viral proteins. The viruses also encode accessory genes, which are virus group specific and believed to play roles in virus replication and pathogenesis in vivo. Of the eight putative accessory proteins encoded by the severe acute respiratory distress syndrome associated coronavirus (SARS-CoV), only twoopen reading frame 3a (ORF3a) and ORF7ahave been identified in virus-infected cells to date. The ORF7b protein is a putative viral accessory protein encoded on subgenomic (sg) RNA 7. The ORF7b initiation codon overlaps the ORF7a stop codon in a 1 shifted ORF. We demonstrate that the ORF7b protein is expressed in virus-infected cell lysates and from a cDNA encoding the gene 7 coding region, indicating that the sgRNA7 is bicistronic. The translation of ORF7b appears to be mediated by ribosome leaky scanning, and the protein has biochemical properties consistent with that of an integral membrane protein. ORF7b localizes to the Golgi compartment and is incorporated into SARS-CoV particles. We therefore conclude that the ORF7b protein is not only an accessory protein but a structural component of the SARS-CoV virion.
* Corresponding author. Mailing address: Department of Molecular Microbiology, Washington University School of Medicine, Campus Box 8230, 660 S. Euclid Ave., St. Louis, MO 63110-1093. Phone: (314) 747-2132. Fax: (314) 362-7325. E-mail:
pekosz{at}borcim.wustl.edu.
Published ahead of print on 1 November 2006.
Journal of Virology, January 2007, p. 718-731, Vol. 81, No. 2
0022-538X/07/$08.00+0 doi:10.1128/JVI.01691-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
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