Different epigenetic layers engage in complex crosstalk to define the epigenetic state of mammalian rRNA genes

Hum Mol Genet. 2007 Apr 15;16 Spec No 1:R21-7. doi: 10.1093/hmg/ddm020.


Eukaryotic cells contain several hundred ribosomal RNA (rRNA) genes (rDNA), a fraction of them being silenced by epigenetic mechanisms. The presence of two epigenetically distinct states of rRNA genes provides a unique opportunity to decipher the molecular mechanisms that establish the euchromatic, i.e. transcriptionally active, and the heterochromatic, i.e. transcriptionally silent, state of rDNA. This article summarizes our knowledge of the epigenetic mechanisms that control rDNA transcription and emphasizes how DNA methyltransferases and histone-modifying enzymes work in concert with chromatin-remodeling complexes and RNA-guided mechanisms to establish a specific chromatin structure that defines the transcriptional state of rRNA genes. These studies exemplify the mutual dependence and complex crosstalk among different epigenetic players in the alteration of the chromatin structure during the process of gene activation or silencing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Chromatin Assembly and Disassembly
  • Chromosomal Proteins, Non-Histone / genetics
  • CpG Islands
  • DNA Methylation
  • DNA, Ribosomal Spacer / genetics
  • Epigenesis, Genetic*
  • Gene Silencing
  • Genes, rRNA*
  • Humans
  • Mammals
  • Models, Genetic
  • Molecular Sequence Data
  • Nucleosomes / genetics
  • Promoter Regions, Genetic


  • Chromosomal Proteins, Non-Histone
  • DNA, Ribosomal Spacer
  • Nucleosomes