Protection from feed-forward amplification in an amplified RNAi mechanism

Cell. 2012 Nov 9;151(4):885-899. doi: 10.1016/j.cell.2012.10.022.


The effectiveness of RNA interference (RNAi) in many organisms is potentiated through the signal-amplifying activity of a targeted RNA-directed RNA polymerase (RdRP) system that can convert a small population of exogenously-encountered dsRNA fragments into an abundant internal pool of small interfering RNA (siRNA). As for any biological amplification system, we expect an underlying architecture that will limit the ability of a randomly encountered trigger to produce an uncontrolled and self-escalating response. Investigating such limits in Caenorhabditis elegans, we find that feed-forward amplification is limited by biosynthetic and structural distinctions at the RNA level between (1) triggers that can produce amplification and (2) siRNA products of the amplification reaction. By assuring that initial (primary) siRNAs can act as triggers but not templates for activation, and that the resulting (secondary) siRNAs can enforce gene silencing on additional targets without unbridled trigger amplification, the system achieves substantial but fundamentally limited signal amplification.

Publication types

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

MeSH terms

  • Animals
  • Base Sequence
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / physiology*
  • Caenorhabditis elegans Proteins / metabolism
  • Gene Silencing
  • Molecular Sequence Data
  • RNA Interference*
  • RNA Replicase / metabolism*
  • RNA, Double-Stranded / metabolism
  • RNA, Small Interfering / metabolism*
  • RNA-Binding Proteins / metabolism


  • Caenorhabditis elegans Proteins
  • RDE-4 protein, C elegans
  • RNA, Double-Stranded
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • SEL-1 protein, C elegans
  • rde-1 protein, C elegans
  • RNA Replicase