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J. Virol., Mar 1995, 1600-1605, Vol 69, No. 3
TJ Chambers, A Nestorowicz and CM Rice
The determinants of cleavage site specificity of the yellow fever virus
(YF) NS3 proteinase for its 2B/3 cleavage site have been studied by using
site-directed mutagenesis. Mutations at residues within the GARR decreases
S sequence were tested for effects on cis cleavage of an NS2B- 3(181)
polyprotein during cell-free translation. At the P1 position, only the
conservative substitution R-->K exhibited significant levels of
cleavage. Conservative and nonconservative substitutions were tolerated at
the P1' and P2 positions, resulting in intermediate levels of cleavage.
Substitutions at the P3 and P4 positions had no effects on cleavage
efficiency in the cell-free assay. Processing at other dibasic sites was
studied by using transient expression of a sig2A-5(356) polyprotein.
Cleavage at the 2B/3 site was not required for processing at downstream
sites. However, increased accumulation of high-molecular- weight viral
polyproteins was generally observed for mutations which reduced cleavage
efficiency at the 2B/3 site. Several mutations were also tested for their
effects on viral replication. Virus was not recovered from substitutions
which blocked or substantially reduced cleavage in the cell-free assay,
suggesting that efficient cleavage at the 2B/3 site is required for
flavivirus replication.
Copyright © 1995, American Society for Microbiology
Mutagenesis of the yellow fever virus NS2B/3 cleavage site: determinants of cleavage site specificity and effects on polyprotein processing and viral replication
Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110-1093.
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