TY - JOUR
T1 - Modulation of gene silencing by Cdc7p via H4 K16 acetylation and phosphorylation of chromatin assembly factor CAF-1 in saccharomyces cerevisiae
AU - Young, Tiffany J.
AU - Cui, Yi
AU - Irudayaraj, Joseph
AU - Kirchmaier, Ann L.
N1 - Publisher Copyright:
© 2019 by the Genetics Society of America.
PY - 2019/4
Y1 - 2019/4
N2 - 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, HMRae**. Here, we observed that loss of Cac1Δ, the largest subunit of CAF-1, also restores silencing at HMRae**, and silencing in both cac1D 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 HMRae** 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 replicationand repair-coupled chromatin assembly per se are functional in the absence of phosphorylation of Cdc7p consensus sites on CAF-1.
AB - 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, HMRae**. Here, we observed that loss of Cac1Δ, the largest subunit of CAF-1, also restores silencing at HMRae**, and silencing in both cac1D 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 HMRae** 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 replicationand repair-coupled chromatin assembly per se are functional in the absence of phosphorylation of Cdc7p consensus sites on CAF-1.
KW - CAC1
KW - CAF-1
KW - CDC7
KW - Histone H4 K16
KW - SAS2
KW - Silencing
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U2 - 10.1534/genetics.118.301858
DO - 10.1534/genetics.118.301858
M3 - Article
C2 - 30728156
AN - SCOPUS:85064721810
SN - 0016-6731
VL - 211
SP - 1219
EP - 1237
JO - Genetics
JF - Genetics
IS - 4
ER -