Journal
CURRENT BIOLOGY
Volume 16, Issue 13, Pages 1280-1289Publisher
CELL PRESS
DOI: 10.1016/j.cub.2006.06.023
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Funding
- NCRR NIH HHS [RR020839] Funding Source: Medline
- NIGMS NIH HHS [GM62385] Funding Source: Medline
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Background: Acetylation of histone H3 lysine 56 (K56Ac) occurs transiently in newly synthesized H3 during passage through S phase and is removed in G2. However, the physiologic roles and effectors of K56Ac: turnover are unknown. Results: The sirtuins Hst3p and, to a lesser extent, Hst4p maintain low levels of K56Ac outside of S phase. In hst3 hst4 mutants, K56 hyperacetylation nears 100%. Residues corresponding to the nicotinamide binding pocket of Sir2p are essential for Hst3p function, and H3 K56 deacetylation is inhibited by nicotinamide in vivo. Rapid inactivation of Hst3/Hst4p prior to S phase elevates K56Ac to 50% in G2, suggesting that K56-acetylated nucleosomes are assembled genome-wide during replication. Inducible expression of Hst3p in G1 or G2 triggers deacetylation of mature chromatin. Cells lacking Hst3/Hst4p exhibit many phenotypes: spontaneous DNA damage, chromosome loss, thermosensitivity, and acute sensitivity to genotoxic agents. These phenotypes are suppressed by mutation of histone H3 K56 into a nonacetylatable residue or by loss of K56Ac in cells lacking the histone chaperone Asf1. Conclusions: Our results underscore the critical importance of Hst3/Hst4p in controlling histone H3 K56Ac and thereby maintaining chromosome integrity.
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