Departamento de Biología Molecular, Centro Andaluz de Biología Molecular y Medicina Regenerativa, Consejo Superior de Investigaciones Científicas, Seville, Spain.
PLoS Genet. 2011 Nov;7(11):e1002376. doi: 10.1371/journal.pgen.1002376. Epub 2011 Nov 10.
Chromatin assembly mutants accumulate recombinogenic DNA damage and are sensitive to genotoxic agents. Here we have analyzed why impairment of the H3K56 acetylation-dependent CAF1 and Rtt106 chromatin assembly pathways, which have redundant roles in H3/H4 deposition during DNA replication, leads to genetic instability. We show that the absence of H3K56 acetylation or the simultaneous knock out of CAF1 and Rtt106 increases homologous recombination by affecting the integrity of advancing replication forks, while they have a minor effect on stalled replication fork stability in response to the replication inhibitor hydroxyurea. This defect in replication fork integrity is not due to defective checkpoints. In contrast, H3K56 acetylation protects against replicative DNA damaging agents by DNA repair/tolerance mechanisms that do not require CAF1/Rtt106 and are likely subsequent to the process of replication-coupled nucleosome deposition. We propose that the tight connection between DNA synthesis and histone deposition during DNA replication mediated by H3K56ac/CAF1/Rtt106 provides a mechanism for the stabilization of advancing replication forks and the maintenance of genome integrity, while H3K56 acetylation has an additional, CAF1/Rtt106-independent function in the response to replicative DNA damage.
染色质组装突变体会积累易发生重组的 DNA 损伤，并对遗传毒性药物敏感。在这里，我们分析了为什么在 DNA 复制过程中，依赖于 H3K56 乙酰化的 CAF1 和 Rtt106 染色质组装途径的功能障碍会导致遗传不稳定性，而这两种途径在 H3/H4 沉积中具有冗余作用。我们发现，缺乏 H3K56 乙酰化或同时敲除 CAF1 和 Rtt106 会通过影响前进复制叉的完整性来增加同源重组，而在复制抑制剂羟基脲引起的停滞复制叉稳定性方面，它们的影响较小。这种复制叉完整性的缺陷不是由于有缺陷的检查点。相反，H3K56 乙酰化通过不需要 CAF1/Rtt106 的 DNA 修复/耐受机制来保护免受复制性 DNA 损伤剂的侵害，并且可能发生在复制偶联核小体沉积之后。我们提出，H3K56ac/CAF1/Rtt106 在 DNA 复制过程中介导的 DNA 合成和组蛋白沉积之间的紧密联系提供了一种稳定前进复制叉和维持基因组完整性的机制，而 H3K56 乙酰化在复制性 DNA 损伤的反应中具有 CAF1/Rtt106 独立的额外功能。
