目的 研究副溶血弧菌H-NS对vp1667的转录调控机制.方法 提取副溶血弧菌hns突变株(Δhns)和野生株(WT)的总RNA,采用实时定量RT-PCR的方法验证H-NS对vp1667的转录调控关系;采用引物延伸实验研究vp1667的转录起始位点,并根据产物的丰度判断H-NS对vp1667的调控关系;将vp1667的启动子区克隆入pHRP309质粒的β-半乳糖苷酶基因上游,构建LacZ重组质粒,并将该重组质粒转入Δhns和WT中获得LacZ菌株.通过LacZ报告基因融合实验研究H-NS对vp1667的调控关系.PCR扩增vp1667的启动子区序列并纯化His-H-NS蛋白,通过凝胶阻滞实验(EMSA)研究His-H-NS对vp1667启动子区是否具有直接的结合作用;采用DNaseⅠ足迹实验研究His-H-NS对vp1667启动子区的具体结合位点.结果与结论 引物延伸结果显示,vp1667只有一个转录起始位点T(-28)(翻译起始位点为+1),且其转录活性受H-NS的抑制;EMSA和DNaseⅠ足迹实验结果显示,His-H-NS不能结合到vp1667的启动子区,表明H-NS只能间接抑制vp1667的转录.%Objective To study the transcriptional regulation of vp1667 by H-NS in Vibrio parahaemolyticus.Methods Total RNAs were extracted from Δhns and WT strains.Quantitative RT-PCR was carried out to calculate the transcriptional variation of vp1667 between Δhns and WT.Primer extension assay was also employed to detect the transcription start site and the promoter activity (i.e.the amount of primer extension products) of vp1667 in Δhns and that in WT.The promoter DNA region of vp1667 was amplified, purified, and cloned into the corresponding restriction endonuclease sites of pHRP309 that harbors a gentamicin resistance gene and a promoterless lacZ reporter gene.The recombinant pHRP309 plasmid was transformed into Δhns and WT, respectively, while β-galactosidase activity in cellular extracts was measured using a β-galactosidase enzyme assay system.The over-expressed His-H-NS was purified under native conditions with nickel loaded HiTrap Chelating Sepharose columns.The electrophoretic mobility shift assay (EMSA) and DNaseⅠ footprinting were then applied to analyze the DNA-binding activity of His-H-NS to vp1667 promoter region in vitro.Results and Conclusion The primer extension assay detected one transcription start site for vp1667, which was located at 28 bp upstream of vp1667, and its transcribed activity was under the negative control of the H-NS.The EMSA and DNaseⅠ footprinting assay results showed that His-H-NS was unable to bind to the promoter-proximal DNA region of vp1667, suggesting that H-NS indirectly inhibits the transcription of vp1667.
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