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J. Virol., 01 1998, 20-31, Vol 72, No. 1
S Mueller and E Wimmer
Using a strategy developed by R. Andino, D. Silvera, S. D. Suggett, P. I.
Achacoso, C. J. Miller, D. Baltimore, and M. B. Feinberg (Science
265:1448-1451, 1994), we constructed recombinant polioviruses by fusing the
open reading frame (ORF) of the green fluorescent protein gene (gfp) of
Aequorea victoria or the gag gene (encoding p17-p24) of human
immunodeficiency virus type 1 (HIV-1) to the N terminus of the poliovirus
polyprotein. All poliovirus expression vectors constructed by us and those
obtained from Andino et al. were found to be severely impaired in viral
replication and genetically unstable. Upon replication, inserted sequences
were rapidly deleted as early as the first growth cycle in HeLa cells.
However, the vector viruses did not readily revert to the wild-type
sequence but rather retained some of the insert plus the artificial
3Cpro/3CDpro cleavage site, engineered between the heterologous sequence
and the poliovirus polyprotein, to give rise to genotypes reminiscent of
cardioviruses. These virus variants that carry a small leader polypeptide
were now relatively stable, and they grew better than their progenitor
strains. Reverse transcription followed by PCR and sequence analysis of the
genomic RNAs reproducibly revealed a few preferred genotypes among the
isolated deletion variants. The remaining truncated inserts were retained
through subsequent passages. In the immediate vicinity of the deletion
borders, we observed short direct sequence repeats that we propose are
involved in aligning RNA strands for illegitimate (nonhomologous) RNA
recombination during minus-strand synthesis. On the basis of our results,
which are at variance with published data, the utility of poliovirus
vectors to express proteins > 10 kDa in size through fusion with the
polyprotein needs to be reevaluated.
Copyright © 1998, American Society for Microbiology
Expression of foreign proteins by poliovirus polyprotein fusion: analysis of genetic stability reveals rapid deletions and formation of cardioviruslike open reading frames
Department of Molecular Genetics and Microbiology, School of Medicine, State University of New York at Stony Brook, 11794, USA. mueller@asterix.bio.sunysb.edu
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