TrxG and PcG proteins but not methylated histones remain associated with DNA through replication

Cell. 2012 Aug 31;150(5):922-33. doi: 10.1016/j.cell.2012.06.046. Epub 2012 Aug 23.

Abstract

Propagation of gene-expression patterns through the cell cycle requires the existence of an epigenetic mark that re-establishes the chromatin architecture of the parental cell in the daughter cells. We devised assays to determine which potential epigenetic marks associate with epigenetic maintenance elements during DNA replication in Drosophila embryos. Histone H3 trimethylated at lysines 4 or 27 is present during transcription but, surprisingly, is replaced by nonmethylated H3 following DNA replication. Methylated H3 is detected on DNA only in nuclei not in S phase. In contrast, the TrxG and PcG proteins Trithorax and Enhancer-of-Zeste, which are H3K4 and H3K27 methylases, and Polycomb continuously associate with their response elements on the newly replicated DNA. We suggest that histone modification enzymes may re-establish the histone code on newly assembled unmethylated histones and thus may act as epigenetic marks.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chromosomal Proteins, Non-Histone / metabolism*
  • DNA Replication*
  • Drosophila / cytology
  • Drosophila / genetics
  • Drosophila / metabolism*
  • Drosophila Proteins / metabolism*
  • Embryo, Nonmammalian / metabolism
  • Epigenesis, Genetic
  • Histone Code*
  • Histones / metabolism*
  • Polycomb Repressive Complex 1
  • Proliferating Cell Nuclear Antigen / metabolism
  • Protein Processing, Post-Translational
  • S Phase

Substances

  • Chromosomal Proteins, Non-Histone
  • Drosophila Proteins
  • Histones
  • Pc protein, Drosophila
  • Proliferating Cell Nuclear Antigen
  • trx protein, Drosophila
  • Polycomb Repressive Complex 1