JVI Figure table search 04
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ozdarendeli, A.
Right arrow Articles by Brian, D. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ozdarendeli, A.
Right arrow Articles by Brian, D. A.

Journal of Virology, August 2001, p. 7362-7374, Vol. 75, No. 16
0022-538X/01/$04.00+0   DOI: 10.1128/JVI.75.16.7362-7374.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Downstream Sequences Influence the Choice between a Naturally Occurring Noncanonical and Closely Positioned Upstream Canonical Heptameric Fusion Motif during Bovine Coronavirus Subgenomic mRNA Synthesis

Aykut Ozdarendeli, Seulah Ku, Sylvie Rochat, Gwyn D. Williams, Savithra D. Senanayake, and David A. Brian*

Department of Microbiology, University of Tennessee, College of Veterinary Medicine, Knoxville, Tennessee 37996-0845

Received 20 February 2001/Accepted 16 May 2001

Mechanisms leading to subgenomic mRNA (sgmRNA) synthesis in coronaviruses are poorly understood but are known to involve a heptameric signaling motif, originally called the intergenic sequence. The intergenic sequence is the presumed crossover region (fusion site) for RNA-dependent RNA polymerase (RdRp) during discontinuous transcription, a process leading to sgmRNAs that are both 5' and 3' coterminal. In the bovine coronavirus, the major fusion site for synthesis of mRNA 5 (GGUAGAC) does not conform to the canonical motif (UC[U,C]AAAC) at three positions (underlined), yet it lies just 14 nucleotides downstream from such a sequence (UCCAAAC). The infrequently used canonical sequence, by computer prediction, is buried within the stem of a stable hairpin (-17.2 kcal/mol). Here we document the existence of this stem by enzyme probing and examine its influence and that of neighboring sequences on the unusual choice of fusion sites by analyzing transcripts made in vivo from mutated defective interfering RNA constructs. We learned that (i) mutations that were predicted to unfold the stem-loop in various ways did not switch RdRp crossover to the upstream canonical site, (ii) a totally nonconforming downstream motif resulted in no measurable transcription from either site, (iii) the canonical upstream site does not function ectopically to lend competence to the downstream noncanonical site, and (iv) altering flanking sequences downstream of the downstream noncanonical motif in ways that diminish sequence similarity with the virus genome 5' end caused a dramatic switch to the upstream canonical site. These results show that sequence elements downstream of the noncanonical site can dramatically influence the choice of fusion sites for synthesis of mRNA 5 and are interpreted as being most consistent with a mechanism of similarity-assisted RdRp strand switching during minus-strand synthesis.

* Corresponding author. Mailing address: Department of Microbiology, University of Tennessee, Knoxville, TN 37996-0845. Phone: (865) 974-4030. Fax: (865) 974-4007. E-mail: dbrian{at}utk.edu.

Journal of Virology, August 2001, p. 7362-7374, Vol. 75, No. 16
0022-538X/01/$04.00+0   DOI: 10.1128/JVI.75.16.7362-7374.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. Mol. Cell. Biol. Microbiol. Mol. Biol. Rev.
Clin. Vaccine Immunol. ALL ASM JOURNALS

Copyright © 2001 by the American Society for Microbiology. All rights reserved.