Modulation of Gene Silencing by Cdc7p via H4 K16 Acetylation and Phosphorylation of Chromatin Assembly Factor CAF-1 in Saccharomyces cerevisiae

Genetics. 2019 Apr;211(4):1219-1237. doi: 10.1534/genetics.118.301858. Epub 2019 Feb 6.


CAF-1 is an evolutionarily conserved H3/H4 histone chaperone that plays a key role in replication-coupled chromatin assembly and is targeted to the replication fork via interactions with PCNA, which, if disrupted, leads to epigenetic defects. In Saccharomyces cerevisiae, when the silent mating-type locus HMR contains point mutations within the E silencer, Sir protein association and silencing is lost. However, mutation of CDC7, encoding an S-phase-specific kinase, or subunits of the H4 K16-specific acetyltransferase complex SAS-I, restore silencing to this crippled HMR, HMR a e** Here, we observed that loss of Cac1p, the largest subunit of CAF-1, also restores silencing at HMR a e**, and silencing in both cac1Δ and cdc7 mutants is suppressed by overexpression of SAS2 We demonstrate Cdc7p and Cac1p interact in vivo in S phase, but not in G1, consistent with observed cell cycle-dependent phosphorylation of Cac1p, and hypoacetylation of chromatin at H4 K16 in both cdc7 and cac1Δ mutants. Moreover, silencing at HMR a e** is restored in cells expressing cac1p mutants lacking Cdc7p phosphorylation sites. We also discovered that cac1Δ and cdc7-90 synthetically interact negatively in the presence of DNA damage, but that Cdc7p phosphorylation sites on Cac1p are not required for responses to DNA damage. Combined, our results support a model in which Cdc7p regulates replication-coupled histone modification via a CAC1-dependent mechanism involving H4 K16ac deposition, and thereby silencing, while CAF-1-dependent replication- and repair-coupled chromatin assembly per se are functional in the absence of phosphorylation of Cdc7p consensus sites on CAF-1.

Keywords: CAC1; CAF-1; CDC7; SAS2; histone H4 K16; silencing.

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

  • Acetylation
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Chromatin Assembly Factor-1 / genetics
  • Chromatin Assembly Factor-1 / metabolism
  • Gene Expression Regulation, Fungal
  • Gene Silencing*
  • Histone Code*
  • Histones / metabolism*
  • Phosphorylation
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*


  • Cell Cycle Proteins
  • Chromatin Assembly Factor-1
  • Histones
  • RLF2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • CDC7 protein, S cerevisiae
  • Protein Serine-Threonine Kinases

Associated data

  • figshare/10.25386/genetics.7427468