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Activation of the DNA damage checkpoint in yeast lacking the histone chaperone anti-silencing function 1

Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center at Fitzsimons, P.O. Box 6511, Aurora, CO 80045, USA.
Molecular and Cellular Biology (Impact Factor: 5.04). 01/2005; 24(23):10313-27. DOI: 10.1128/MCB.24.23.10313-10327.2004
Source: PubMed

ABSTRACT The packaging of the eukaryotic genome into chromatin is likely to be important for the maintenance of genomic integrity. Chromatin structures are assembled onto newly synthesized DNA by the action of chromatin assembly factors, including anti-silencing function 1 (ASF1). To investigate the role of chromatin structure in the maintenance of genomic integrity, we examined budding yeast lacking the histone chaperone Asf1p. We found that yeast lacking Asf1p accumulate in metaphase of the cell cycle due to activation of the DNA damage checkpoint. Furthermore, yeast lacking Asf1p are highly sensitive to mutations in DNA polymerase alpha and to DNA replicational stresses. Although yeast lacking Asf1p do complete DNA replication, they have greatly elevated rates of DNA damage occurring during DNA replication, as indicated by spontaneous Ddc2p-green fluorescent protein foci. The presence of elevated levels of spontaneous DNA damage in asf1 mutants is due to increased DNA damage, rather than the failure to repair double-strand DNA breaks, because asf1 mutants are fully functional for double-strand DNA repair. Our data indicate that the altered chromatin structure in asf1 mutants leads to elevated rates of spontaneous recombination, mutation, and DNA damage foci formation arising during DNA replication, which in turn activates cell cycle checkpoints that respond to DNA damage.

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    • "In yeast, it was demonstrated that Asf1 shields H3/H4 from unfavorable DNA interactions and aids the formation of favorable histone-DNA interactions through the formation of disomes (Donham et al., 2011). In addition, yeast cells lacking Asf1 display an increased frequency of genome instability and spontaneous genome rearrangement (Myung et al., 2003; Prado et al., 2004; Ramey et al., 2004). ASF1 is also required to efficiently complete DNA replication in the presence of DNA-damaging agents or compromised replication machinery (Franco et al., 2005). "
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    • "All available data indicate that during double-strand break repair, like nucleotide excision repair, CAF-1 and Asf1 mediate chromatin assembly over the repaired DNA. In yeast, neither CAF-1 nor Asf1 mutants show any clear defects in repair of the double-strand breaks themselves (Linger and Tyler, 2005; Ramey et al., 2004), consistent with a role after rather than before DNA repair. Asf1's role in promoting chromatin assembly after double-strand break repair is an indirect consequence of its requirement to acetylate H3K56 (Chen et al., 2008). "
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    • "Asf1p is a histone H3-H4 chaperone protein present in a complex that repairs dsDNA damage [23]. Lack of the protein leads to a lag in the metaphase cell cycle due to DNA damage checkpoint activation [24]. The Mrc1p is an activator of a DNA replication stress response. "
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