Journal of Virology, March 2001, p. 2097-2106, Vol. 75, No. 5
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.5.2097-2106.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
9 Fatty Acid Desaturase
Inhibits Brome Mosaic Virus RNA Replication between Template
Recognition and RNA Synthesis
Howard Hughes Medical
Institute1 and Institute for Molecular
Virology,2 University of Wisconsin
Madison,
Madison, Wisconsin 53706
Received 18 July 2000/Accepted 30 November 2000
All positive-strand RNA viruses assemble their RNA replication
complexes on intracellular membranes. Brome mosaic virus (BMV) replicates its RNA in endoplasmic reticulum (ER)-associated complexes in plant cells and the yeast Saccharomyces cerevisiae. BMV
encodes RNA replication factors 1a, with domains implicated in RNA
capping and helicase functions, and 2a, with a central polymerase-like domain. Factor 1a interacts independently with the ER membrane, viral
RNA templates, and factor 2a to form RNA replication complexes on the
perinuclear ER. We show that BMV RNA replication is severely inhibited
by a mutation in OLE1, an essential yeast chromosomal gene
encoding
9 fatty acid desaturase, an integral ER membrane protein
and the first enzyme in unsaturated fatty acid synthesis. OLE1 deletion and medium supplementation show that BMV RNA
replication requires unsaturated fatty acids, not the Ole1 protein, and
that viral RNA replication is much more sensitive than yeast growth to
reduced unsaturated fatty acid levels. In ole1 mutant
yeast, 1a still becomes membrane associated, recruits 2a to the
membrane, and recognizes and stabilizes viral RNA templates normally.
However, RNA replication is blocked prior to initiation of
negative-strand RNA synthesis. The results show that viral RNA
synthesis is highly sensitive to lipid composition and suggest that
proper membrane fluidity or plasticity is essential for an early step
in RNA replication. The strong unsaturated fatty acid dependence also
demonstrates that modulating fatty acid balance can be an effective
antiviral strategy.
Madison, 1525 Linden Dr., Madison, WI 53706-1596. Phone: (608) 263-5916. Fax: (608) 265-9214. E-mail: ahlquist{at}facstaff.wisc.edu.
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