Journal of Virology, September 1998, p. 7387-7396, Vol. 72, No. 9
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
Received 19 March 1998/Accepted 22 May 1998
The segmented double-stranded (ds) RNA genome of the rotaviruses is
replicated asymmetrically, with viral mRNA serving as the template for
the synthesis of minus-strand RNA. Previous studies with cell-free
replication systems have shown that the highly conserved termini of
rotavirus gene 8 and 9 mRNAs contain cis-acting signals
that promote the synthesis of dsRNA. Based on the location of the
cis-acting signals and computer modeling of their secondary structure, the ends of the gene 8 or 9 mRNAs are proposed to interact in cis to form a modified panhandle structure that promotes
the synthesis of dsRNA. In this structure, the last 11 to 12 nucleotides of the RNA, including the cis-acting signal
that is essential for RNA replication, extend as a single-stranded tail
from the panhandled region, and the 5' untranslated region folds to
form a stem-loop motif. To understand the importance of the predicted secondary structure in minus-strand synthesis, mutations were introduced into viral RNAs which affected the 3' tail and the 5'
stem-loop. Analysis of the RNAs with a cell-free replication system
showed that, in contrast to mutations which altered the structure of
the 5' stem-loop, mutations which caused complete or near-complete
complementarity between the 5' end and the 3' tail significantly
inhibited (
10-fold) minus-strand synthesis. Likewise, incubation of
wild-type RNAs with oligonucleotides which were complementary to the 3'
tail inhibited replication. Despite their replication-defective
phenotype, mutant RNAs with complementary 5' and 3' termini were shown
to competitively interfere with the replication of wild-type mRNA and
to bind the viral RNA polymerase VP1 as efficiently as wild-type RNA.
These results indicate that the single-strand nature of the 3' end of
rotavirus mRNA is essential for efficient dsRNA synthesis and that the
specific binding of the RNA polymerase to the mRNA template is required
but not sufficient for the synthesis of minus-strand RNA.
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