Department of Medical Genetics, University of British Columbia, Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Vancouver, British Columbia V5Z 4H4, Canada.
J Biol Chem. 2010 Nov 5;285(45):35113-22. doi: 10.1074/jbc.M110.116855. Epub 2010 Sep 1.
Genomic integrity is maintained by the coordinated interaction of many DNA damage response pathways, including checkpoints, DNA repair processes, and cell cycle restart. In Saccharomyces cerevisiae, the BRCA1 C-terminal domain-containing protein Rtt107/Esc4 is required for restart of DNA replication after successful repair of DNA damage and for cellular resistance to DNA-damaging agents. Rtt107 and its interaction partner Slx4 are phosphorylated during the initial phase of DNA damage response by the checkpoint kinases Mec1 and Tel1. Because the natural chromatin template plays an important role during the DNA damage response, we tested whether chromatin modifications affected the requirement for Rtt107 and Slx4 during DNA damage repair. Here, we report that the sensitivity to DNA-damaging agents of rtt107Δ and slx4Δ mutants was rescued by inactivation of the chromatin regulatory pathway leading to H3 K79 trimethylation. Further analysis revealed that lack of Dot1, the H3 K79 methyltransferase, led to activation of the translesion synthesis pathway, thereby allowing the survival in the presence of DNA damage. The DNA damage-induced phosphorylation of Rtt107 and Slx4, which was mutually dependent, was not restored in the absence of Dot1. The antagonistic relationship between Rtt107 and Dot1 was specific for DNA damage-induced phenotypes, whereas the genomic instability caused by loss of Rtt107 was not rescued. These data revealed a multifaceted functional relationship between Rtt107 and Dot1 in the DNA damage response and maintenance of genome integrity.
基因组完整性是通过许多 DNA 损伤反应途径的协调相互作用来维持的，包括检查点、DNA 修复过程和细胞周期的重新启动。在酿酒酵母中，BRCA1 C 端结构域包含蛋白 Rtt107/Esc4 是成功修复 DNA 损伤后 DNA 复制重新启动所必需的，也是细胞抵抗 DNA 损伤剂所必需的。在 DNA 损伤反应的初始阶段，检查点激酶 Mec1 和 Tel1 使 Rtt107 和其相互作用伙伴 Slx4 磷酸化。由于天然染色质模板在 DNA 损伤反应中起着重要作用，我们测试了染色质修饰是否影响 DNA 损伤修复过程中对 Rtt107 和 Slx4 的需求。在这里，我们报告说，rtt107Δ 和 slx4Δ 突变体对 DNA 损伤剂的敏感性可以通过失活导致 H3 K79 三甲基化的染色质调节途径来挽救。进一步的分析表明，缺乏 Dot1，即 H3 K79 甲基转移酶，导致跨损伤合成途径的激活，从而允许在存在 DNA 损伤的情况下存活。相互依赖的 DNA 损伤诱导的 Rtt107 和 Slx4 磷酸化在缺乏 Dot1 的情况下没有恢复。Rtt107 和 Dot1 之间的拮抗关系是特定于 DNA 损伤诱导表型的，而 Rtt107 缺失引起的基因组不稳定性则不能挽救。这些数据揭示了 Rtt107 和 Dot1 在 DNA 损伤反应和基因组完整性维持中的多方面功能关系。
