A single amino acid change in the L-polymerase protein of vesicular stomatitis virus completely abolishes viral mRNA cap methylation.

Abstract

The vesicular stomatitis virus (VSV) RNA polymerase synthesizes viral mRNAs with 5'-cap structures methylated at the guanine-N7 and 2'-O-adenosine positions (7mGpppA(m)). Previously, our laboratory showed that a VSV host range (hr) and temperature-sensitive (ts) mutant, hr1, had a complete defect in mRNA cap methylation and that the wild-type L protein could complement the hr1 defect in vitro. Here, we sequenced the L, P, and N genes of mutant hr1 and found only two amino acid substitutions, both residing in the L-polymerase protein, which differentiate hr1 from its wild-type parent. These mutations (N505D and D1671V) were introduced separately and together into the L gene, and their effects on VSV in vitro transcription and in vivo chloramphenicol acetyltransferase minigenome replication were studied under conditions that are permissive and nonpermissive for hr1. Neither L mutation significantly affected viral RNA synthesis at 34 degrees C in permissive (BHK) and nonpermissive (HEp-2) cells, but D1671V reduced in vitro transcription and genome replication by about 50% at 40 degrees C in both cell lines. Recombinant VSV bearing each mutation were isolated, and the hr and ts phenotypes in infected cells were the result of a single D1671V substitution in the L protein. While the mutations did not significantly affect mRNA synthesis by purified viruses, 5'-cap analyses of product mRNAs clearly demonstrated that the D1671V mutation abrogated all methyltransferase activity. Sequence analysis suggests that an aspartic acid at amino acid 1671 is a critical residue within a putative conserved S-adenosyl-l-methionine-binding domain of the L protein.

• Authors: Valery Z Grdzelishvili, Sherin Smallwood, Dallas Tower, Richard L Hall, D Margaret Hunt, Sue A Moyer
• Journal: Journal of virology (J Virol) Vol. 79 Issue 12 Pg. 7327-37 (Jun 2005) ISSN: 0022-538X [Print] United States
• PMID: 15919887 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• RNA Caps
• RNA, Messenger
• RNA, Viral
• Viral Proteins
• L protein, vesicular stomatitis virus
• RNA-Dependent RNA Polymerase

Topics

• Amino Acid Sequence
• Amino Acid Substitution
• Animals
• Cell Line
• Cricetinae
• Humans
• Methylation
• Molecular Sequence Data
• Mutation
• RNA Caps (metabolism)
• RNA, Messenger (metabolism)
• RNA, Viral (metabolism)
• RNA-Dependent RNA Polymerase (chemistry, genetics, metabolism)
• Recombination, Genetic
• Temperature
• Vesicular stomatitis Indiana virus (genetics, metabolism, physiology)
• Viral Proteins (chemistry, genetics, metabolism)
• Virus Replication