Transcriptional slippage in the positive-sense RNA virus family Potyviridae

EMBO Rep. 2015 Aug;16(8):995-1004. doi: 10.15252/embr.201540509. Epub 2015 Jun 25.


The family Potyviridae encompasses ~30% of plant viruses and is responsible for significant economic losses worldwide. Recently, a small overlapping coding sequence, termed pipo, was found to be conserved in the genomes of all potyvirids. PIPO is expressed as part of a frameshift protein, P3N-PIPO, which is essential for virus cell-to-cell movement. However, the frameshift expression mechanism has hitherto remained unknown. Here, we demonstrate that transcriptional slippage, specific to the viral RNA polymerase, results in a population of transcripts with an additional "A" inserted within a highly conserved GAAAAAA sequence, thus enabling expression of P3N-PIPO. The slippage efficiency is ~2% in Turnip mosaic virus and slippage is inhibited by mutations in the GAAAAAA sequence. While utilization of transcriptional slippage is well known in negative-sense RNA viruses such as Ebola, mumps and measles, to our knowledge this is the first report of its widespread utilization for gene expression in positive-sense RNA viruses.

Keywords: P3N‐PIPO; Potyvirus; RNA virus; gene expression; transcriptional slippage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA-Directed RNA Polymerases / genetics*
  • Frameshifting, Ribosomal
  • Gene Expression Regulation, Viral
  • Genome, Viral*
  • High-Throughput Nucleotide Sequencing
  • Open Reading Frames
  • Plant Leaves / virology
  • Potyvirus / genetics*
  • RNA, Viral / genetics*
  • Tobacco / virology*
  • Transcription, Genetic*
  • Viral Proteins / genetics


  • RNA, Viral
  • Viral Proteins
  • DNA-Directed RNA Polymerases