Deciphering the Mechanism of Defective Interfering RNA (DI RNA) Biogenesis Reveals That a Viral Protein and the DI RNA Act Antagonistically in Virus Infection

J Virol. 2013 Jun;87(11):6091-103. doi: 10.1128/JVI.03322-12. Epub 2013 Mar 20.

Abstract

Potato mop-top virus (PMTV) produces a defective RNA (D RNA) encompassing the 5'-terminal 479 nucleotides (nt) and 3'-terminal 372 nt of RNA-TGB (where TGB is triple gene block). The mechanism that controls D RNA biogenesis and the role of D RNA in virus accumulation was investigated by introducing deletions, insertions, and point mutations into the sequences of the open reading frames (ORFs) of TGB1 and the 8-kilodalton (8K) protein that were identified as required for efficient production of the D RNA. Transient expression of RNA-TGB in the absence of RNA-Rep (which encodes the replicase) did not result in accumulation of D RNA, indicating that its production is dependent on PMTV replication. The D RNA could be eliminated by disrupting a predicted minus-strand stem-loop structure comprising complementary sequences of the 5' TGB1 ORF and the 3' 8K ORF, suggesting intramolecular template switching during positive-strand synthesis as a mechanism for the D RNA biogenesis. Virus accumulation was reduced when the 8K ORF was disrupted but D RNA was produced. Conversely, the virus accumulated at higher titers when the 8K ORF was intact and D RNA production was blocked. These data demonstrate that the D RNA interferes with virus infection and therefore should be referred to as a defective interfering RNA (DI RNA). The 8K protein was shown to be a weak silencing suppressor. This study provides an example of the interplay between a pathogen and its molecular parasite where virus accumulation was differentially regulated by the 8K protein and DI RNA, indicating that they play antagonistic roles and suggesting a mechanism by which the virus can attenuate replication, decreasing viral load and thereby enhancing its efficiency as a parasite.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Defective Viruses / chemistry
  • Defective Viruses / genetics*
  • Defective Viruses / metabolism
  • Humans
  • Inverted Repeat Sequences
  • Molecular Sequence Data
  • Open Reading Frames
  • Plant Diseases / virology*
  • RNA Interference*
  • RNA Viruses / chemistry
  • RNA Viruses / genetics*
  • RNA Viruses / metabolism
  • RNA, Viral / chemistry
  • RNA, Viral / genetics*
  • RNA, Viral / metabolism
  • Tobacco / virology*
  • Viral Proteins / chemistry
  • Viral Proteins / genetics*
  • Viral Proteins / metabolism

Substances

  • RNA, Viral
  • Viral Proteins