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J Virol, March 1998, p. 2398-2405, Vol. 72, No. 3
Department of Microbiology,
Received 28 July 1997/Accepted 30 November 1997
Four mutants of the virulent Mahoney strain of poliovirus were
generated by introducing mutations in nucleotides (nt) 128 to 134 of
the genome, a region that contains a part of the stem-loop II (SLII)
structure located within the internal ribosomal entry site (IRES; nt
120 to 590) (K. Shiroki, T. Ishii, T. Aoki, Y. Ota, W.-X. Yang, T. Komatsu, Y. Ami, M. Arita, S. Abe, S. Hashizume, and A. Nomoto, J. Virol. 71:1-8, 1997). These mutants (SLII mutants) replicated well in
human HeLa cells but not in mouse TgSVA cells that had been established
from the kidney of a poliovirus-sensitive transgenic mouse. Their
neurovirulence in mice was also greatly attenuated compared to that of
the parental virus. The poor replication activity of the SLII mutants
in TgSVA cells appeared to be attributable to reduced activity of the
IRES. Two and three naturally occurring revertants that replicated well
in TgSVA cells were isolated from mutants SLII-1 and SLII-5,
respectively. The revertants recovered IRES activity in a cell-free
translation system from TgSVA cells and returned to a neurovirulent
phenotype like that of the Mahoney strain in mice. Two of the revertant
sites that affected the phenotype were identified as being at nt 107 and within a region from nt 120 to 161. A mutation at nt 107, specifically a change from uridine to adenine, was observed in all the
revertant genomes and exerted a significant effect on the revertant
phenotype. Exhibition of the full revertant phenotype required
mutations in both regions. These results suggested that nt 107 of
poliovirus RNA is involved in structures required for the IRES activity
in mouse cells.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
A New Internal Ribosomal Entry Site 5' Boundary Is
Required for Poliovirus Translation Initiation in a Mouse
System
*
Corresponding author. Mailing address: Department of
Microbiology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan. Phone: 81-3-5449-5501. Fax: 81-3-5449-5408.
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