dsRNA with 5′ overhangs contributes to endogenous and antiviral RNA silencing pathways in plants

Ryuya Fukunaga, Jennifer A. Doudna

Research output: Contribution to journalArticlepeer-review

100 Scopus citations


In plants, SGS3 and RNA-dependent RNA polymerase 6 (RDR6) are required to convert single- to double-stranded RNA (dsRNA) in the innate RNAi-based antiviral response and to produce both exogenous and endogenous short-interfering RNAs. Although a role for RDR6-catalysed RNA-dependent RNA polymerisation in these processes seems clear, the function of SGS3 is unknown. Here, we show that SGS3 is a dsRNA-binding protein with unexpected substrate selectivity favouring 5′-overhang-containing dsRNA. The conserved XS and coiled-coil domains are responsible for RNA-binding activity. Furthermore, we find that the V2 protein from tomato yellow leaf curl virus, which suppresses the RNAi-based host immune response, is a dsRNA-binding protein with similar specificity to SGS3. In competition-binding experiments, V2 outcompetes SGS3 for substrate dsRNA recognition, whereas a V2 point mutant lacking the suppressor function in vivo cannot efficiently overcome SGS3 binding. These findings suggest that SGS3 recognition of dsRNA containing a 5′ overhang is required for subsequent steps in RNA-mediated gene silencing in plants, and that V2 functions as a viral suppressor by preventing SGS3 from accessing substrate RNAs.

Original languageEnglish (US)
Pages (from-to)545-555
Number of pages11
JournalEMBO Journal
Issue number5
StatePublished - Mar 4 2009
Externally publishedYes


  • Overhang
  • Plant
  • RNA silencing
  • Viral suppressor
  • dsRNA-binding

ASJC Scopus subject areas

  • General Neuroscience
  • Molecular Biology
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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