Cellular RNA-dependent RNA polymerase involved in posttranscriptional gene silencing has two distinct activity modes.
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.
Makeyev
Eugene V
EV
Department of Biosciences and Institute of Biotechnology, University of Helsinki, P.O. Box 56, 5, FIN-00014, Viikinkaari, Finland.
Bamford
Dennis H
DH
D000595:Amino Acid Sequence; D001483:Base Sequence; D016384:Consensus Sequence; D017931:DNA Primers; D020868:Gene Silencing; D008969:Molecular Sequence Data; D009492:Neurospora crassa / Q000201:enzymology / Q000235:genetics*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012323:RNA Processing, Post-Transcriptional; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013698:Templates, Genetic
D017931:DNA Primers; D011994:Recombinant Proteins; D012324:RNA-Dependent RNA Polymerase