Aix-Marseille Univ, CNRS, Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, Marseille, France.
Department of Biochemistry, University of Wisconsin-Madison, Wisconsin-Madison, United States.
Elife. 2021 Feb 19;10:e63747. doi: 10.7554/eLife.63747.
Reactive oxygen species (ROS) cause damage to DNA and proteins. Here, we report that the RecA recombinase is itself oxidized by ROS. Genetic and biochemical analyses revealed that oxidation of RecA altered its DNA repair and DNA recombination activities. Mass spectrometry analysis showed that exposure to ROS converted four out of nine Met residues of RecA to methionine sulfoxide. Mimicking oxidation of Met35 by changing it for Gln caused complete loss of function, whereas mimicking oxidation of Met164 resulted in constitutive SOS activation and loss of recombination activity. Yet, all ROS-induced alterations of RecA activity were suppressed by methionine sulfoxide reductases MsrA and MsrB. These findings indicate that under oxidative stress MsrA/B is needed for RecA homeostasis control. The implication is that, besides damaging DNA structure directly, ROS prevent repair of DNA damage by hampering RecA activity.
活性氧（ROS）会对 DNA 和蛋白质造成损伤。在这里，我们报告 RecA 重组酶本身会被 ROS 氧化。遗传和生化分析表明，RecA 的氧化改变了其 DNA 修复和 DNA 重组活性。质谱分析表明，暴露于 ROS 会将 RecA 中的九个 Met 残基中的四个转化为甲硫氨酸亚砜。用 Gln 取代 Met35 的氧化模拟导致完全丧失功能，而模拟 Met164 的氧化导致持续的 SOS 激活和重组活性丧失。然而，所有由 ROS 引起的 RecA 活性改变都被甲硫氨酸亚砜还原酶 MsrA 和 MsrB 抑制。这些发现表明，在氧化应激下，MsrA/B 对于 RecA 同源性控制是必需的。这意味着，ROS 除了直接破坏 DNA 结构外，还通过阻碍 RecA 活性来阻止 DNA 损伤的修复。
