首页> 外文期刊>Journal of bacteriology >Complex Regulation of the Organic Hydroperoxide Resistance Gene (ohr) from XanthomonasInvolves OhrR, a Novel Organic Peroxide-Inducible Negative Regulator, and Posttranscriptional Modifications
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Complex Regulation of the Organic Hydroperoxide Resistance Gene (ohr) from XanthomonasInvolves OhrR, a Novel Organic Peroxide-Inducible Negative Regulator, and Posttranscriptional Modifications

机译:Xanthomonas的有机氢过氧化物抗性基因(ohr)的复杂调节涉及OhrR,一种新型的有机过氧化物诱导的负性调节剂和转录后修饰。

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Analysis of the sequence immediate upstream of ohrrevealed an open reading frame, designated ohrR, with the potential to encode a 17-kDa peptide with moderate amino acid sequence homology to the MarR family of negative regulators of gene expression. ohrR was transcribed as bicistronic mRNA with ohr, while ohr mRNA was found to be 95% monocistronic and 5% bicistronic with ohrR. Expression of both genes was induced by tert-butyl hydroperoxide (tBOOH) treatment. High-level expression ofohrR negatively regulated ohr expression. This repression could be overcome by tBOOH treatment. In vivo promoter analysis showed that the ohrR promoter (P1) has organic peroxide-inducible, strong activity, while the ohrpromoter (P2) has constitutive, weak activity. Only P1 is autoregulated by OhrR. ohr primer extension results revealed three major primer extension products corresponding to the 5′ ends ofohr mRNA, and their levels were strongly induced by tBOOH treatment. Sequence analysis of regions upstream of these sites showed no typical Xanthomonas promoter. Instead, the regions can form a stem-loop secondary structure with the 5′ ends ofohr mRNA located in the loop section. The secondary structure resembles the structure recognized and processed by RNase III enzyme. These findings suggest that the P1 promoter is responsible for tBOOH-induced expression of the ohrR-ohr operon. The bicistronic mRNA is then processed by RNase III-like enzymes to give high levels of ohr mRNA, while ohrR mRNA is rapidly degraded.
机译: ohr 上游序列的分析揭示了一个开放阅读框,称为 ohrR ,具有编码与MarR具有中等氨基酸序列同源性的17-kDa肽的潜力基因表达的负调节子家族。 ohrR ohr转录为双顺反子mRNA,而 ohr mRNA与 ohrR <95%合成为单顺反子和5%双顺反子。 / em>。叔丁基过氧化氢(tBOOH)处理可诱导两个基因的表达。 ohrR 的高水平表达负调控 ohr 的表达。这种抑制可以通过tBOOH处理来克服。体内启动子分析表明, ohrR 启动子(P1)具有有机过氧化物诱导的强活性,而 ohr 启动子(P2)具有组成型,弱活性。 OhrR仅自动调节P1。 ohr 引物延伸结果显示了与 ohr mRNA 5'末端相对应的三种主要引物延伸产物,它们的水平受到tBOOH处理的强烈诱导。这些位点上游区域的序列分析表明没有典型的 Xanthomonas 启动子。取而代之的是,这些区域可以形成茎环二级结构,其中 ohr mRNA的5'端位于环区。二级结构类似于被RNase III酶识别和加工的结构。这些发现表明,P1启动子负责tBOOH诱导的 ohrR-ohr 操纵子的表达。然后,双顺反子mRNA被类RNase III酶处理,从而产生高水平的 ohr mRNA,而 ohrR mRNA则迅速降解。

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