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Journal of Virology, October 2000, p. 9062-9070, Vol. 74, No. 19
Department of Virology, Center of Infectious
Diseases, Leiden University Medical Center, Leiden, The Netherlands
Received 23 March 2000/Accepted 10 July 2000
Equine arteritis virus (EAV), the prototype
arterivirus, is an enveloped plus-strand RNA virus with a genome of
approximately 13 kb. Based on similarities in genome organization and
protein expression, the arteriviruses have recently been grouped
together with the coronaviruses and toroviruses in the newly
established order Nidovirales. Previously, we reported the
construction of pEDI, a full-length cDNA copy of EAV DI-b, a natural
defective interfering (DI) RNA of 5.6 kb (R. Molenkamp et al., J. Virol. 74:3156-3165, 2000). EDI RNA consists of three noncontiguous
parts of the EAV genome fused in frame with respect to the replicase gene. As a result, EDI RNA contains a truncated replicase open reading
frame (EDI-ORF) and encodes a truncated replicase polyprotein. Since
some coronavirus DI RNAs require the presence of an ORF for their
efficient propagation, we have analyzed the importance of the EDI-ORF
in EDI RNA replication. The EDI-ORF was disrupted at different
positions by the introduction of frameshift mutations. These were found
either to block DI RNA replication completely or to be removed within
one virus passage, probably due to homologous recombination with the
helper virus genome. Using recombination assays based on EDI RNA and
full-length EAV genomes containing specific mutations, the rates of
homologous RNA recombination in the 3'- and 5'-proximal regions of the
EAV genome were studied. Remarkably, the recombination frequency in the
5'-proximal region was found to be approximately 100-fold lower than
that in the 3'-proximal part of the genome.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Efficient Homologous RNA Recombination and
Requirement for an Open Reading Frame during Replication of Equine
Arteritis Virus Defective Interfering RNAs
*
Corresponding author. Mailing address: Department of
Virology, Center of Infectious Diseases, Leiden University Medical
Center, LUMC P4-26, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
Phone: 31 71 5261657. Fax: 31 71 5266761. E-mail:
E.J.Snijder{at}LUMC.nl.
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