Regulation of nrf operon expression in pathogenic enteric bacteria: sequence divergence reveals new regulatory complexity.
Regulation of nrf operon expression in pathogenic enteric bacteria: sequence divergence reveals new regulatory complexity.
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DOI：
10.1111/mmi.13647
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发表时间：
2017-05
影响因子：
3.6
通讯作者：
Browning DF
中科院分区：
文献类型：
--
作者：
Godfrey RE;Lee DJ;Busby SJW;Browning DF
大肠杆菌K-12 nrf操纵子编码周质亚硝酸盐还原酶，其表达由单个启动子pnrf驱动。来自pnrf的表达响应于厌氧被FNR转录因子激活，并且响应于亚硝酸盐被响应调节蛋白NarL和NarP进一步增加。FNR依赖性转录被两种类核相关蛋白IHF和Fis的结合抑制。随着在丰富培养基中生长的细胞中Fis水平的增加，其结合位点的定位与启动子-10元件重叠，确保pnrf被急剧抑制。在这里，我们调查的nrf操纵子启动子从各种致病性肠道细菌的表达。我们表明，pnrf从肠出血性大肠杆菌。大肠杆菌比其K-12对应物更活跃，表现出大量的FNR-独立活性，并且由于改进的-10元素而对营养质量不敏感。我们还表明，沙门氏菌血清型鼠伤寒核心启动子比以前认为的更活跃，由于转录起始位点周围的差异，其表达被下游序列抑制。我们确定了CsrA RNA结合蛋白作为负责这一点，并表明，CsrA差异调节E。大肠杆菌K-12和沙门氏菌nrf操纵子。
The Escherichia coli K‐12 nrf operon encodes a periplasmic nitrite reductase, the expression of which is driven from a single promoter, pnrf. Expression from pnrf is activated by the FNR transcription factor in response to anaerobiosis and further increased in response to nitrite by the response regulator proteins, NarL and NarP. FNR‐dependent transcription is suppressed by the binding of two nucleoid associated proteins, IHF and Fis. As Fis levels increase in cells grown in rich medium, the positioning of its binding site, overlapping the promoter −10 element, ensures that pnrf is sharply repressed. Here, we investigate the expression of the nrf operon promoter from various pathogenic enteric bacteria. We show that pnrf from enterohaemorrhagic E. coli is more active than its K‐12 counterpart, exhibits substantial FNR‐independent activity and is insensitive to nutrient quality, due to an improved −10 element. We also demonstrate that the Salmonella enterica serovar Typhimurium core promoter is more active than previously thought, due to differences around the transcription start site, and that its expression is repressed by downstream sequences. We identify the CsrA RNA binding protein as being responsible for this, and show that CsrA differentially regulates the E. coli K‐12 and Salmonella nrf operons.