Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC, 41092 Seville, Spain.
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain.
Genetics. 2022 Aug 30;222(1). doi: 10.1093/genetics/iyac108.
The stability of the genome is occasionally challenged by the formation of DNA-RNA hybrids and R-loops, which can be influenced by the chromatin context. This is mainly due to the fact that DNA-RNA hybrids hamper the progression of replication forks, leading to fork stalling and, ultimately, DNA breaks. Through a specific screening of chromatin modifiers performed in the yeast Saccharomyces cerevisiae, we have found that the Rtt109 histone acetyltransferase is involved in several steps of R-loop-metabolism and their associated genetic instability. On the one hand, Rtt109 prevents DNA-RNA hybridization by the acetylation of histone H3 lysines 14 and 23 and, on the other hand, it is involved in the repair of replication-born DNA breaks, such as those that can be caused by R-loops, by acetylating lysines 14 and 56. In addition, Rtt109 loss renders cells highly sensitive to replication stress in combination with R-loop-accumulating THO-complex mutants. Our data evidence that the chromatin context simultaneously influences the occurrence of DNA-RNA hybrid-associated DNA damage and its repair, adding complexity to the source of R-loop-associated genetic instability.
基因组的稳定性偶尔会受到 DNA-RNA 杂交体和 R 环的形成的挑战，而这些结构会受到染色质环境的影响。这主要是因为 DNA-RNA 杂交体阻碍了复制叉的前进，导致叉停顿，最终导致 DNA 断裂。通过在酵母酿酒酵母中对染色质修饰物进行特定筛选，我们发现 Rtt109 组蛋白乙酰转移酶参与 R 环代谢及其相关遗传不稳定性的几个步骤。一方面，Rtt109 通过乙酰化组蛋白 H3 赖氨酸 14 和 23 来防止 DNA-RNA 杂交，另一方面，它还参与复制产生的 DNA 断裂的修复，例如由 R 环引起的断裂，通过乙酰化赖氨酸 14 和 56。此外，Rtt109 的缺失使细胞对复制应激非常敏感，与积累 R 环的 THO 复合物突变体结合使用时更是如此。我们的数据表明，染色质环境同时影响 DNA-RNA 杂交体相关 DNA 损伤的发生及其修复，这为 R 环相关遗传不稳定性的来源增加了复杂性。
