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Journal of Virology, February 2002, p. 2003-2008, Vol. 76, No. 4
0022-538X/01/$04.00+0     DOI: 10.1128/JVI.76.4.2003-2008.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Processing of Nonstructural Protein 1a of Human Astrovirus

Ute Geigenmüller, Teri Chew,^, Nancy Ginzton, and Suzanne M. Matsui^*

Division of Gastroenterology and Hepatology, Department of Medicine, Stanford University School of Medicine, Stanford, California 94305, and Gastroenterology Section, Department of Medicine, VA Palo Alto Health Care System, Palo Alto, California 94304

Received 9 July 2001/ Accepted 13 November 2001

Astrovirus contains three open reading frames (ORF) on its genomic RNA, ORF1a, ORF1b, and ORF2. ORF1a encodes a 920-amino-acid (aa) nonstructural protein, nsP1a, which displays a 3C-like serine protease motif. Little is known about the processing of nsP1a or whether the protease it contains is active and involved in autocatalytic processing. Here we address both of these matters. Intact and N-terminally deleted forms of ORF1a from human astrovirus serotype 1 were expressed in BHK cells, and nsP1a-derived processing products were immunoprecipitated with an nsP1a-specific antibody or an antibody specific for an N-terminally linked epitope tag. The mapping of the main processing products, p20 and p27, suggests cleavage sites near aa 170, 410, and 655 of nsP1a. Cleavages at around aa 410 and 655, but not aa 170, were abolished when a 9-aa substitution was introduced into the protease motif in nsP1a. The p27 processing product was also found in Caco-2 cells that had been infected with human astrovirus serotype 1, confirming the presence of the cleavage sites at approximately aa 410 and 655.

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* Corresponding author. Mailing address: Gastroenterology Section (111-GI), VA Palo Alto Health Care System, 3801 Miranda Ave., Palo Alto, CA 94304. Phone: (650) 493-5000, ext. 63179. Fax: (650) 852-3295. E-mail: sumatsui{at}stanford.edu.

Present address: University of California, San Francisco, School of Medicine, San Francisco, Calif.

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Journal of Virology, February 2002, p. 2003-2008, Vol. 76, No. 4
0022-538X/01/$04.00+0     DOI: 10.1128/JVI.76.4.2003-2008.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

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