Roles of RNA polymerase IV in gene silencing

Trends Plant Sci. 2008 Jul;13(7):390-7. doi: 10.1016/j.tplants.2008.04.008.


Eukaryotes typically have three multi-subunit enzymes that decode the nuclear genome into RNA: DNA-dependent RNA polymerases I, II and III (Pol I, II and III). Remarkably, higher plants have five multi-subunit nuclear RNA polymerases: the ubiquitous Pol I, II and III, which are essential for viability; plus two non-essential polymerases, Pol IVa and Pol IVb, which specialize in small RNA-mediated gene silencing pathways. There are numerous examples of phenomena that require Pol IVa and/or Pol IVb, including RNA-directed DNA methylation of endogenous repetitive elements, silencing of transgenes, regulation of flowering-time genes, inducible regulation of adjacent gene pairs, and spreading of mobile silencing signals. Although biochemical details concerning Pol IV enzymatic activities are lacking, genetic evidence suggests several alternative models for how Pol IV might function.

Publication types

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

MeSH terms

  • Catalytic Domain
  • DNA-Directed RNA Polymerases / chemistry
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism*
  • Flowers / genetics
  • Flowers / growth & development
  • Gene Expression Regulation, Developmental
  • Gene Expression Regulation, Plant
  • Gene Silencing*
  • Models, Molecular
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*


  • Plant Proteins
  • DNA-Directed RNA Polymerases