乙酰化修饰降低Ku蛋白的DNA结合活性

【目的】研究乙酰化修饰对Ku蛋白活性的影响。【方法】利用耻垢分枝杆菌为表达菌株,转入Ku蛋白表达质粒,纯化具有乙酰化修饰的Ku蛋白和无乙酰化的Ku蛋白突变体,比较两类蛋白的生化活性;分析氧化压力和酸性环境下耻垢分枝杆菌细胞内Ku蛋白乙酰化水平的变化。【结果】Ku蛋白过量表达的耻垢分枝杆菌比转入空质粒的对照菌株生长缓慢;乙酰化Ku蛋白比未发生乙酰化Ku蛋白修复断裂DNA的活性降低、DNA结合活性降低;氧化压力和酸性压力环境下,耻垢分枝杆菌细胞内Ku蛋白数量降低,乙酰化Ku蛋白数量变化不大。【结论】乙酰化修饰能够调节Ku蛋白的DNA结合活性,从而调节非同源末端连接修复系统的活性;Ku蛋白乙酰化程度升高是耻垢分枝杆菌对不良生长环境的反应。

Acetylation reduced the DNA binding activity of Ku protein

[Objective] To understand the role of acetylation modification on the activity of Ku protein.[Methods] Acetylated Ku protein and its non-acetylated mutant were expressed and purified using M smegmatis expression system, and then their biochemical activities were compared. The effect of oxidative stress and acidic environment on Ku protein acetylation level were analyzed in M. smegmatis. [Results] Ku protein over-expression M. smegmatis strain grew slower than the control strain transformed with the empty plasmid. Acetylated Ku protein had lower DNA repair activity and DNA binding activity than the non-acetylated Ku. Quantity of Ku protein in M. smegmatis cells under oxidative and acidic stress decreased, whereas there was subtle change of acetylated Ku protein. [Conclusion] Acetylation modification can regulate the DNA binding activity of Ku protein, thus regulate the activity of Non-homologous end joining system. The increase of acetylation level of Ku protein is the response of mycobacteria against the adverse growth environment.