Histone H2A phosphorylation and H3 methylation are required for a novel Rad9 DSB repair function following checkpoint activation

DNA Repair (Amst). 2006 Jun 10;5(6):693-703. doi: 10.1016/j.dnarep.2006.03.005. Epub 2006 May 2.


In budding yeast, the Rad9 protein is an important player in the maintenance of genomic integrity and has a well-characterised role in DNA damage checkpoint activation. Recently, roles for different post-translational histone modifications in the DNA damage response, including H2A serine 129 phosphorylation and H3 lysine 79 methylation, have also been demonstrated. Here, we show that Rad9 recruitment to foci and bulk chromatin occurs specifically after ionising radiation treatment in G2 cells. This stable recruitment correlates with late stages of double strand break (DSB) repair and, surprisingly, it is the hypophosphorylated form of Rad9 that is retained on chromatin rather than the hyperphosphorylated, checkpoint-associated, form. Stable Rad9 accumulation in foci requires the Mec1 kinase and two independently regulated histone modifications, H2A phosphorylation and Dot1-dependent H3 methylation. In addition, Rad9 is selectively recruited to a subset of Rad52 repair foci. These results, together with the observation that rad9Delta cells are defective in repair of IR breaks in G2, strongly indicate a novel post checkpoint activation role for Rad9 in promoting efficient repair of DNA DSBs by homologous recombination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / chemistry*
  • Cell Cycle Proteins / metabolism
  • Checkpoint Kinase 2
  • Chromatin / metabolism
  • DNA / chemistry
  • DNA Damage
  • DNA Methylation
  • DNA Repair*
  • Green Fluorescent Proteins / metabolism
  • Histone-Lysine N-Methyltransferase
  • Histones / chemistry*
  • Histones / metabolism
  • Intracellular Signaling Peptides and Proteins
  • Lysine / chemistry
  • Methylation
  • Nuclear Proteins / chemistry
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / metabolism
  • Recombination, Genetic
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism


  • Cell Cycle Proteins
  • Chromatin
  • Histones
  • Intracellular Signaling Peptides and Proteins
  • Nuclear Proteins
  • Saccharomyces cerevisiae Proteins
  • rad9 protein
  • Green Fluorescent Proteins
  • DNA
  • Dot1 protein, S cerevisiae
  • Histone-Lysine N-Methyltransferase
  • Checkpoint Kinase 2
  • MEC1 protein, S cerevisiae
  • Protein-Serine-Threonine Kinases
  • RAD53 protein, S cerevisiae
  • Lysine