Cellular RNA-dependent RNA polymerase involved in posttranscriptional gene silencing has two distinct activity modes

Mol Cell. 2002 Dec;10(6):1417-27. doi: 10.1016/s1097-2765(02)00780-3.


Recent genetic data suggest that proteins homologous to a plant RNA-dependent RNA polymerase (RdRP) play a central role in posttranscriptional gene silencing (PTGS) in many organisms. We show here that purified recombinant protein QDE-1, a genetic component of PTGS ("quelling") in the fungus Neurospora crassa, possesses RNA polymerase activity in vitro. The full-length enzyme and its enzymatically active C-terminal fragment perform two different reactions on single-stranded RNA templates, synthesizing either extensive RNA chains that form template-length duplexes or approximately 9-21-mer complementary RNA oligonucleotides scattered along the entire template. QDE-1 supports both de novo and primer-dependent initiation mechanisms. These results suggest that several distinct activities of cell-encoded RdRPs can be employed for efficient PTGS in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Consensus Sequence
  • DNA Primers
  • Gene Silencing*
  • Molecular Sequence Data
  • Neurospora crassa / enzymology
  • Neurospora crassa / genetics*
  • Plasmids
  • Polymerase Chain Reaction
  • RNA Processing, Post-Transcriptional*
  • RNA-Dependent RNA Polymerase / chemistry
  • RNA-Dependent RNA Polymerase / genetics*
  • RNA-Dependent RNA Polymerase / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Templates, Genetic


  • DNA Primers
  • Recombinant Proteins
  • RNA-Dependent RNA Polymerase