What are memories made of? How Polycomb and Trithorax proteins mediate epigenetic memory

Nat Rev Mol Cell Biol. 2014 May;15(5):340-56. doi: 10.1038/nrm3789.


In any biological system with memory, the state of the system depends on its history. Epigenetic memory maintains gene expression states through cell generations without a change in DNA sequence and in the absence of initiating signals. It is immensely powerful in biological systems - it adds long-term stability to gene expression states and increases the robustness of gene regulatory networks. The Polycomb group (PcG) and Trithorax group (TrxG) proteins can confer long-term, mitotically heritable memory by sustaining silent and active gene expression states, respectively. Several recent studies have advanced our understanding of the molecular mechanisms of this epigenetic memory during DNA replication and mitosis.

Publication types

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

MeSH terms

  • Animals
  • Chromatin / metabolism
  • Chromatin Assembly and Disassembly*
  • Chromosomal Proteins, Non-Histone / genetics*
  • Chromosomal Proteins, Non-Histone / metabolism
  • DNA Replication
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / metabolism
  • Drosophila melanogaster / genetics*
  • Drosophila melanogaster / growth & development
  • Drosophila melanogaster / metabolism
  • Epigenesis, Genetic*
  • Gene Expression
  • Genes, Homeobox
  • Larva / genetics*
  • Larva / growth & development
  • Larva / metabolism
  • Mitosis / genetics
  • Polycomb-Group Proteins / genetics*
  • Polycomb-Group Proteins / metabolism


  • Chromatin
  • Chromosomal Proteins, Non-Histone
  • Drosophila Proteins
  • Polycomb-Group Proteins
  • trx protein, Drosophila