HlyU acts as an H-NS antirepressor in the regulation of the RTX toxin gene essential for the virulence of the human pathogen Vibrio vulnificus CMCP6.
HlyU acts as an H-NS antirepressor in the regulation of the RTX toxin gene essential for the virulence of the human pathogen Vibrio vulnificus CMCP6.
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DOI：
10.1111/j.1365-2958.2009.06664.x
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发表时间：
2009-04
影响因子：
3.6
通讯作者：
Crosa JH
中科院分区：
文献类型：
--
作者：
Liu M;Naka H;Crosa JH
在创伤弧菌中，HlyU 上调大 RTX 毒素基因的表达。在这项工作中，我们鉴定了 HlyU 与 rtxA1 操纵子转录起始位点 -417 至 -376 bp 的结合位点。 rtxA1 操纵子启动子的一系列渐进性缺失的 lacZ 融合表明，当 HlyU 结合位点缺失时，转录活性的增加独立于 HlyU。因此，HlyU 必须通过拮抗负调节因子来调节 rtxA1 操纵子的表达。同时我们发现 hns 突变体导致 rtxA1 操纵子基因表达增加。 HlyU 的多个拷贝只有在 H-NS 存在的情况下才能增加启动子活性，这强调了 HlyU 必须减轻该蛋白的抑制的假设。 H-NS 结合到 rtxA1 操纵子启动子上游和下游延伸的区域。在上游区域，它与五个富含 AT 的位点结合，其中两个与 HlyU 结合位点重叠。竞争性足迹和凝胶位移数据表明，与 H-NS 相比，HlyU 具有更高的亲和力，从而导致 rtxA1 操纵子的去抑制和相应的表达增加。
In Vibrio vulnificus, HlyU up-regulates the expression of the large RTX toxin gene. In this work we identified the binding site of HlyU to -417 to -376 bp of the rtxA1 operon transcription start site. lacZ fusions for a series of progressive deletions from the rtxA1 operon promoter showed that transcriptional activity increased independently of HlyU when its binding site was absent. Thus HlyU must regulate the rtxA1 operon expression by antagonizing a negative regulator. Concomitantly we found that an hns mutant resulted in an increase in the expression of the rtxA1 operon genes. Multiple copies of HlyU can increase the promoter activity only in the presence of H-NS underscoring the hypothesis that HlyU must alleviate the repression by this protein. H-NS binds to a region that extends upstream and downstream of the rtxA1 operon promoter. In the upstream region it binds to five AT-rich sites of which two overlap the HlyU binding site. Competitive footprinting and gel shift data demonstrate HlyU’s higher affinity as compared to H-NS resulting in the de-repression and a corresponding increased expression of the rtxA1 operon.