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J. Virol., Feb 1995, 864-870, Vol 69, No. 2
EV Pilipenko, AP Gmyl, SV Maslova, EV Khitrina and VI Agol
A set of Theiler's murine encephalomyelitis virus mutants with engineered
alterations in the conserved oligopyrimidine/AUG tandem (E. V. Pilipenko,
A. P. Gmyl, S. V. Maslova, G. A. Belov, A. N. Sinyakov, M. Huang, T. D. K.
Brown, and V. I. Agol, J. Mol. Biol. 241:398-414, 1994) were assayed for
their growth potential in BHK-21 cells (as reflected in plaque size) and
for neurovirulence upon intracerebral inoculation of mice.
Tandem-destroying mutations, which included substitutions in the
oligopyrimidine moiety and extended insertions into the oligopyrimidine/AUG
spacer, exerted relatively little effect on the plaque size but ensured a
high level of attenuation. The attenuated mutants exhibited remarkable
genetic stability upon growth in BHK-21 cells. However, the brains of rare
animals that developed symptoms after the inoculation with high doses of
these mutants invariably contained pseudorevertants with the
oligopyrimidine/AUG tandem restored by diverse deletions or an
AUG-generating point mutation. The AUG moiety of the tandem in the
revertant genomes was represented by either a cryptic codon or initiator
codon. The results demonstrate that the tandem, while dispensable for the
Theiler's murine encephalomyelitis virus growth in BHK-21 cells, is
essential for neurovirulence in mice. Thus, the oligopyrimidine/AUG tandem
is a host- dependent cis-acting control element that may be essential for
virus replication under certain conditions. The functional activity of the
tandem was retained when its oligopyrimidine or AUG moieties were made
double stranded. A possible role of the tandem in the cap-independent
internal initiation of translation on the picornavirus RNA templates is
discussed.
Copyright © 1995, American Society for Microbiology
Attenuation of Theiler's murine encephalomyelitis virus by modifications of the oligopyrimidine/AUG tandem, a host-dependent translational cis element
Institute of Poliomyelitis and Viral Encephalitides, Russian Academy of Medical Sciences, Moscow Region.
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