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Potyviral VPg Enhances Viral RNA Translation and Inhibits Reporter mRNA Translation In Planta
Author(s) -
Katri Eskelin,
Anders Hafrén,
Kimmo Rantalainen,
Kristiina Mäkinen
Publication year - 2011
Publication title -
journal of virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.617
H-Index - 292
eISSN - 1070-6321
pISSN - 0022-538X
DOI - 10.1128/jvi.00052-11
Subject(s) - biology , rna , untranslated region , messenger rna , eif4e , translation (biology) , gene expression , microbiology and biotechnology , eukaryotic translation , three prime untranslated region , viral protein , virology , virus , gene , genetics
Viral protein genome-linked (VPg) plays a central role in several stages of potyvirus infection. This study sought to answer questions about the role ofPotato virus A (PVA; genusPotyvirus ) VPg in viral and host RNA expression. When expressed inNicotiana benthamiana leavesin trans , a dual role of VPg in translation is observed. It repressed the expression of monocistronic luciferase (luc ) mRNA and simultaneously induced a significant upregulation in the expression of both replicating and nonreplicating PVA RNAs. This enhanced viral gene expression was due at least to the 5′ untranslated region (UTR) of PVA RNA, eukaryotic initiation factors 4E and iso 4E [eIF4E/eIF(iso)4E], and the presence of a sufficient amount of VPg. Coexpression of VPg with viral RNA increased the viral RNA amount, which was not the case with the monocistronic mRNA. Both mutations at certain lysine residues in PVA VPg and eIF4E/eIF(iso)4E depletion reduced its ability to upregulate the viral RNA expression. These modifications were also involved in VPg-mediated downregulation of monocistronicluc expression. These results suggest that VPg can titrate eIF4Es from capped monocistronic RNAs. Because VPg-mediated enhancement of viral gene expression required eIF4Es, it is possible that VPg directs eIF4Es to promote viral RNA expression. From this study it is evident that VPg can serve as a specific regulator of PVA expression by boosting the viral RNA amounts as well as the accumulation of viral translation products. Such a mechanism could function to protect viral RNA from being degraded and to secure efficient production of coat protein (CP) for virion formation.

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