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Journal of Virology, January 1999, p. 307-315, Vol. 73, No. 1
Department of Microbiology, The Medical
School, University of Alabama at Birmingham, Birmingham, Alabama
35294
Received 6 August 1998/Accepted 5 October 1998
The cis-acting genomic RNA requirements for the
assembly of vesicular stomatitis virus (VSV) ribonucleocapsids into
infectious particles were investigated. Using a biological assay based
on particle infectivity, we demonstrated that subgenomic replicons that
contained all four possible combinations of the natural genomic termini, the 3' leader (Le) and 5' trailer (Tr) regions, were replication competent; however, a 3' copyback replicon (3'CB), containing the natural 3' terminus but having the 5' Tr replaced by a
sequence complementary to the 3' Le for 46 nucleotides, was unable to
assemble infectious particles, despite efficient replication. When a
copy of Tr was inserted 51 nucleotides from the 5' end of 3'CB,
infectious particles were produced. However, analysis of the
replication products of these particles showed that the 51 nucleotides
which corresponded to the Le complement sequences at the 5' terminus
were removed during RNA replication, thus restoring the wild-type 5' Tr
to the exact 5' terminus. These data showed that a
cis-acting signal was necessary for assembly of VSV RNAs into infectious particles and that this signal was supplied by Tr when
located at the 5' end. The regions within Tr required for assembly were
analyzed by a series of deletions and exchanges for Le complement
sequences, which demonstrated that the 5' terminal 29 nucleotides of Tr
allowed assembly of infectious particles but that the 5' terminal 22 nucleotides functioned poorly. Deletions in Tr also altered the balance
between negative- and positive-strand genomic RNA and affected levels
of replication. RNAs that retained fewer than 45 but at least 22 nucleotides of the 5' terminus could replicate but were impaired in RNA
replication, and RNAs that retained only 14 nucleotides of the 5'
terminus were severely reduced in ability to replicate. These data
define the VSV Tr as a position-dependent, cis-acting
element for the assembly of RNAs into infectious particles, and they
delineate RNA sequences that are essential for negative-strand RNA
synthesis. These observations are consistent with, and offer an
explanation for, the absence of 3' copyback defective interfering
particles in nature.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The 5' Terminal Trailer Region of Vesicular
Stomatitis Virus Contains a Position-Dependent cis-Acting
Signal for Assembly of RNA into Infectious Particles
*
Corresponding author. Department of Microbiology, The
Medical School, University of Alabama at Birmingham, BBRB17 Room 366, 845 19th St. South, Birmingham, AL 35294. Phone: (205) 934-0453. Fax:
(205) 934-1636. E-mail: gail_wertz{at}microbio.uab.edu.
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