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J. Virol., Jan 1995, 247-252, Vol 69, No. 1
SF Yu, P Benton, M Bovee, J Sessions and RE Lloyd
2A protease (2Apro) catalyzes the initial cleavage of the poliovirus
polyprotein which separates the P1 structural protein precursor from the
P2-P3 nonstructural protein precursor. In addition, 2Apro indirectly
induces cleavage of the p220 component of eukaryotic initiation factor 4F,
which is thought to contribute to the specific inhibition of host cell
protein synthesis observed in virus-infected HeLa cells. However, it is
unclear whether the trans function of 2Apro which induces host cell shutoff
is essential or merely facilitates efficient poliovirus replication. In
this study, three point mutations in 2Apro (D38E, Y88L, and Y89L [S. F. Yu
and R. E. Lloyd, Virology 182:615-625, 1991]) which cause specific loss of
trans but not cis cleavage function were independently introduced into the
full-length poliovirus cDNA. In addition, mutations which caused only
partial loss of both cis and trans cleavage activities (Y88S) or resulted
in a wild- type phenotype (Y88F) were individually introduced. When each of
these mutant poliovirus cDNAs was transcribed and translated in vitro,
normal proteolytic processing of the viral polyprotein was observed, and
p220 was not cleaved in those reactions containing proteases defective in
trans function, as expected. Surprisingly, Northern (RNA) blot analysis and
reverse transcriptase-PCRs performed after transfection of COS-7 or HeLa
cells with these viral RNAs revealed that Y88S and Y88L RNAs replicated at
only very low levels. RNA replication could not be detected at all in cells
transfected with D38E and Y89L RNAs. Taken together, the results suggest a
correlation between the function of 2Apro and productive poliovirus RNA
replication in vivo that may be independent of the ability to cause p220
cleavage.
Copyright © 1995, American Society for Microbiology
Defective RNA replication by poliovirus mutants deficient in 2A protease cleavage activity
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
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