The 4-cysteine zinc-finger motif of the RNA polymerase regulator DksA serves as a thiol switch for sensing oxidative and nitrosative stress.
The 4-cysteine zinc-finger motif of the RNA polymerase regulator DksA serves as a thiol switch for sensing oxidative and nitrosative stress.
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DOI：
10.1111/mmi.12498
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发表时间：
2014-02
影响因子：
3.6
通讯作者：
Vázquez-Torres A
中科院分区：
文献类型：
--
作者：
Henard CA;Tapscott T;Crawford MA;Husain M;Doulias PT;Porwollik S;Liu L;McClelland M;Ischiropoulos H;Vázquez-Torres A
我们发现，巯基在4-半胱氨酸锌指基序的DksA，RNA聚合酶辅助蛋白已知调节严格的反应，感觉氧化和亚硝化应激。过氧化氢或一氧化氮（NO）介导的DksA 4-半胱氨酸锌指基序中硫醇的修饰释放金属辅因子，并驱动蛋白质α螺旋度的可逆变化。野生型和relA spoT突变沙门氏菌，但不是同基因dksA缺陷型细菌，经历下调的r-蛋白和氨基酸转运表达后，NO处理，这表明DksA可以调节基因表达，在响应NO同系物独立的ppGpp报警。氧化应激增强了DksA依赖的抑制rpsM，同时防止激活的livJ和hisG基因的转录，这是支持减少，锌结合DksA。氧化的DksA对转录的抑制作用是可逆的二硫苏糖醇。我们的研究表明，通过DksA氧化还原活性硫醇的反应物种的传感微调的翻译机器和氨基酸的同化和生物合成的表达雅阁符合氧化和亚硝化应激所施加的代谢应激。考虑到Cys 114的保守性，以及DksA直向同源物中邻近的疏水性和带电氨基酸，遗传多样性微生物可以使用DksA巯基开关来调节对氧化和亚硝化应激的转录响应。
We show that thiols in the 4-cysteine zinc-finger motif of DksA, an RNA polymerase accessory protein known to regulate the stringent response, sense oxidative and nitrosative stress. Hydrogen peroxide- or nitric oxide (NO)-mediated modifications of thiols in the DksA 4-cysteine zinc-finger motif release the metal cofactor and drive reversible changes in the α-helicity of the protein. Wild-type and relA spoT mutant Salmonella, but not isogenic dksA-deficient bacteria, experience the downregulation of r-protein and amino acid transport expression after NO treatment, suggesting that DksA can regulate gene expression in response to NO congeners independently of the ppGpp alarmone. Oxidative stress enhances the DksA-dependent repression of rpsM, while preventing the activation of livJ and hisG gene transcription that is supported by reduced, zinc-bound DksA. The inhibitory effects of oxidized DksA on transcription are reversible with dithiothreitol. Our investigations indicate that sensing of reactive species by DksA redox active thiols fine-tunes the expression of translational machinery and amino acid assimilation and biosynthesis in accord with the metabolic stress imposed by oxidative and nitrosative stress. Given the conservation of Cys114, and neighboring hydrophobic and charged amino acids in DksA orthologues, phylogenetically diverse microorganisms may use the DksA thiol switch to regulate transcriptional responses to oxidative and nitrosative stress.
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