Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan.
J Bacteriol. 2018 Jul 25;200(16). doi: 10.1128/JB.00201-18. Print 2018 Aug 15.
NurA and HerA are thought to be essential proteins for DNA end resection in archaeal homologous recombination systems. , an extremely thermophilic eubacterium, has proteins that exhibit significant sequence similarity to archaeal NurA and HerA. To unveil the cellular function of NurA and HerA in , we performed phenotypic analysis of disruptant mutants of and with or without DNA-damaging agents. The and genes were not essential for survival, and their deletion had no effect on cell growth and genome integrity. Unexpectedly, these disruptants of showed increased resistance to UV irradiation and mitomycin C treatment. Further, these disruptants and the wild type displayed no difference in sensitivity to oxidative stress and a DNA replication inhibitor. NurA had nuclease activity, and HerA had ATPase. The overexpression of loss-of-function mutants of and in the respective disruptants showed no complementation, suggesting their enzymatic activities were involved in the UV sensitivity. In addition, NurA and HerA interacted with each other and , forming a complex with 2:6 stoichiometry. These results suggest that the NurA-HerA complex has an architecture similar to that of archaeal counterparts but that it impairs, rather than promotes, the repair of photoproducts and DNA cross-links in cells. This cellular function is distinctly different from that of archaeal NurA and HerA. Many nucleases and helicases are engaged in homologous recombination-mediated DNA repair. Previous analyses in archaea indicated that NurA and HerA are the recombination-related nuclease and helicase. However, their cellular function had not been fully understood, especially in bacterial cells. In this study, we performed analyses to address the cellular function of and in an extremely thermophilic bacterium, As a result, NurA and HerA exhibited an interfering effect on the repair of several instances of DNA damage in the cell, which is in contrast to the results in archaea. This finding will facilitate our understanding of the diverse cellular functions of the recombination-related nucleases and helicases.
NurA 和 HerA 被认为是古菌同源重组系统中 DNA 末端切除所必需的蛋白质。作为一种极端嗜热的真细菌，具有与古菌 NurA 和 HerA 具有显著序列相似性的蛋白质。为了揭示 NurA 和 HerA 在 中的细胞功能，我们对带有或不带有 DNA 损伤剂的突变体进行了表型分析。和 基因对于生存不是必需的，它们的缺失对细胞生长和基因组完整性没有影响。出乎意料的是，这些 的突变体对紫外线照射和丝裂霉素 C 处理表现出更高的抗性。此外，这些突变体和野生型在对氧化应激和 DNA 复制抑制剂的敏感性方面没有差异。NurA 具有核酸酶活性，而 HerA 具有 ATP 酶活性。在各自的突变体中过表达丧失功能的突变体，没有互补作用，表明它们的酶活性参与了对紫外线的敏感性。此外，NurA 和 HerA 相互作用，形成一个 2:6 摩尔比的复合物。这些结果表明，NurA-HerA 复合物具有与古菌类似的结构，但它会阻碍而不是促进 细胞中光产物和 DNA 交联的修复。这种细胞功能与古菌 NurA 和 HerA 明显不同。许多核酸酶和解旋酶参与同源重组介导的 DNA 修复。以前在古菌中的分析表明，NurA 和 HerA 是与重组相关的核酸酶和解旋酶。然而，它们的细胞功能尚未完全理解，特别是在细菌细胞中。在这项研究中，我们进行了 分析，以解决 在一种极端嗜热细菌中的细胞功能。结果表明，NurA 和 HerA 对细胞中几种 DNA 损伤的修复有干扰作用，这与古菌的结果相反。这一发现将有助于我们理解与重组相关的核酸酶和解旋酶的不同细胞功能。
