GDP polyribonucleotidyltransferase domain of vesicular stomatitis virus polymerase regulates leader-promoter escape and polyadenylation-coupled termination during stop-start transcription

PLoS Pathog. 2022 Feb 2;18(2):e1010287. doi: 10.1371/journal.ppat.1010287. eCollection 2022 Feb.


The unconventional mRNA capping enzyme (GDP polyribonucleotidyltransferase, PRNTase) domain of the vesicular stomatitis virus (VSV) L protein possesses a dual-functional "priming-capping loop" that governs terminal de novo initiation for leader RNA synthesis and capping of monocistronic mRNAs during the unique stop-start transcription cycle. Here, we investigated the roles of basic amino acid residues on a helix structure directly connected to the priming-capping loop in viral RNA synthesis and identified single point mutations that cause previously unreported defective phenotypes at different steps of stop-start transcription. Mutations of residue R1183 (R1183A and R1183K) dramatically reduced the leader RNA synthesis activity by hampering early elongation, but not terminal de novo initiation or productive elongation, suggesting that the mutations negatively affect escape from the leader promoter. On the other hand, mutations of residue R1178 (R1178A and R1178K) decreased the efficiency of polyadenylation-coupled termination of mRNA synthesis at the gene junctions, but not termination of leader RNA synthesis at the leader-to-N-gene junction, resulting in the generation of larger amounts of aberrant polycistronic mRNAs. In contrast, both the R1183 and R1178 residues are not essential for cap-forming activities. The R1183K mutation was lethal to VSV, whereas the R1178K mutation attenuated VSV and triggered the production of the polycistronic mRNAs in infected cells. These observations suggest that the PRNTase domain plays multiple roles in conducting accurate stop-start transcription beyond its known role in pre-mRNA capping.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Cell Line
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism
  • Mutation
  • Nucleotidyltransferases / metabolism
  • Polyribonucleotide Nucleotidyltransferase / genetics
  • Polyribonucleotide Nucleotidyltransferase / metabolism*
  • Protein Conformation
  • Protein Domains
  • RNA Precursors / metabolism
  • RNA, Viral / metabolism*
  • RNA-Dependent RNA Polymerase / genetics*
  • RNA-Dependent RNA Polymerase / metabolism*
  • Transcription, Genetic
  • Vesicular Stomatitis / virology*
  • Vesicular stomatitis Indiana virus / genetics*
  • Vesicular stomatitis Indiana virus / metabolism*
  • Viral Proteins / genetics*
  • Viral Proteins / metabolism*
  • Virus Replication


  • RNA Precursors
  • RNA, Viral
  • Viral Proteins
  • Nucleotidyltransferases
  • L protein, vesicular stomatitis virus
  • RNA-Dependent RNA Polymerase
  • mRNA guanylyltransferase
  • DNA-Directed RNA Polymerases
  • Polyribonucleotide Nucleotidyltransferase