Proliferating cell nuclear antigen and ASF1 modulate silent chromatin in Saccharomyces cerevisiae via lysine 56 on histone H3

Genetics. 2008 Jun;179(2):793-809. doi: 10.1534/genetics.107.084525.


The formation and stability of epigenetically regulated chromatin is influenced by DNA replication and factors that modulate post-translational modifications on histones. Here we describe evidence that PCNA can affect silencing in Saccharomyces cerevisiae by facilitating deposition of H3 K56ac onto chromosomes. We propose that PCNA participates in this process through a pathway that includes replication factor C, the chromatin assembly factor Asf1p, and the K56-specific acetyltransferase Rtt109p. We show that mutation of POL30 or loss of K56-acetylation in rtt109 and histone H3 mutants enhances silencing at the crippled HMR locus HMRae via restoring Sir binding and that pol30 mutants with silencing phenotypes have reduced levels of H3 K56ac. Although loss of acetylation on H3 K56 was generally compatible with silencing, mutations at this residue also led to defects in silencing an ADE2 reporter at HMR and abolished silencing when combined with cac1 or pol30-8. These silencing phenotypes are analogous to those in asf1 mutants or pol30-6 and pol30-79 mutants with defects in ASF1-dependent pathways. On the basis of these findings, we propose that mutations in DNA replication factors alter acetylation of H3 K56. We show that this defect, in turn, contributes to misregulation of epigenetic processes as well as of cellular responses to DNA damage.

Publication types

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

MeSH terms

  • Cell Cycle Proteins / genetics*
  • Chromatin / genetics
  • DNA Damage
  • Epigenesis, Genetic
  • Gene Silencing
  • Genes, Fungal
  • Histone Acetyltransferases / genetics
  • Histone Acetyltransferases / metabolism
  • Histones / chemistry
  • Histones / genetics*
  • Histones / metabolism
  • Lysine / chemistry
  • Models, Genetic
  • Molecular Chaperones
  • Mutation
  • Proliferating Cell Nuclear Antigen / genetics*
  • Proliferating Cell Nuclear Antigen / metabolism
  • Protein Processing, Post-Translational
  • Replication Protein C / genetics
  • Replication Protein C / metabolism
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Telomere / genetics


  • ASF1 protein, S cerevisiae
  • Cell Cycle Proteins
  • Chromatin
  • Histones
  • Molecular Chaperones
  • Proliferating Cell Nuclear Antigen
  • Saccharomyces cerevisiae Proteins
  • Histone Acetyltransferases
  • Rtt109 protein, S cerevisiae
  • Replication Protein C
  • Lysine