A Conserved Motif in Region V of the Large Polymerase Proteins of Nonsegmented Negative-Sense RNA Viruses That Is Essential for mRNA Capping
Whelan, Sean J.
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CitationLi, J., A. Rahmeh, M. Morelli, and S. P. J. Whelan. 2007. “A Conserved Motif in Region V of the Large Polymerase Proteins of Nonsegmented Negative-Sense RNA Viruses That Is Essential for mRNA Capping.” Journal of Virology 82 (2): 775–84. https://doi.org/10.1128/jvi.02107-07.
AbstractNonsegmented negative-sense (NNS) RNA viruses cap their mRNA by an unconventional mechanism. Specifically, 5 ' monophosphate mRNA is transferred to GDP derived from GTP through a reaction that involves a covalent intermediate between the large polymerase protein L and mRNA. This polyribonucleotidyltransferase activity contrasts with all other capping reactions, which are catalyzed by an RNA triphosphatase and guanylyltransferase. In these reactions, a 5 ' diphosphate mRNA is capped by transfer of GMP via a covalent enzyme-GMP intermediate. RNA guanylyltransferases typically have a KxDG motif in which the lysine forms this covalent intermediate. Consistent with the distinct mechanism of capping employed by NNS RNA viruses, such a motif is absent from L. To determine the residues of L protein required for capping, we reconstituted the capping reaction of the prototype NNS RNA virus, vesicular stomatitis virus, from highly purified components. Using a panel of L proteins with single-amino-acid substitutions to residues universally conserved among NNS RNA virus L proteins, we define a new motif, GxxT[n]HR, present within conserved region V of L protein that is essential for this unconventional mechanism of mRNA cap formation.
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