Upstream sequence-dependent suppression and AtxA-dependent activation of protective antigens in Bacillus anthracis
Upstream sequence-dependent suppression and AtxA-dependent activation of protective antigens in Bacillus anthracis
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DOI：
10.7717/peerj.6718
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发表时间：
2019-04
期刊：
影响因子：
2.7
通讯作者：
Kochi Toyomane;Y. Furuta;D. Fujikura;H. Higashi
中科院分区：
文献类型：
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作者：
Kochi Toyomane;Y. Furuta;D. Fujikura;H. Higashi
炭疽毒素是炭疽杆菌产生的毒力因子。炭疽毒素基因的转录由转录因子 AtxA 控制。因此，AtxA被认为是炭疽芽孢杆菌致病性的关键因素。尽管 AtxA 在炭疽杆菌感染中发挥重要作用，但 AtxA 控制炭疽毒素表达的分子机制仍不清楚。本研究旨在表征 AtxA 介导的保护性抗原 (PA) 调节的分子机制，保护性抗原 (PA) 是由 pagA 基因编码的炭疽毒素的组成部分。首先，通过构建上游区域与营养缺陷型标记的转录融合来体内评估pagA和AtxA上游区域之间的相互作用。结果表明，(i) pagA 的上游区域抑制了下游基因的转录，(ii) AtxA 恢复了抑制的转录。其次，使用凝胶迁移率变化测定进行体外分析，以评估 AtxA-DNA 相互作用的结合特异性。结果显示 AtxA 与 DNA 的结合与序列无关。综上所述，我们的研究结果表明 PA 的表达受到 pagA 上游区域的抑制，而 AtxA 和上游区域的相互作用释放了这种抑制。
The anthrax toxin is a virulence factor produced by the bacterium Bacillus anthracis. Transcription of anthrax toxin genes is controlled by the transcription factor AtxA. Thus, AtxA is thought to be a key factor for the pathogenicity of B. anthracis. Despite its important role in B. anthracis infection, the molecular mechanism by which AtxA controls expression of anthrax toxin remains unclear. This study aimed to characterize the molecular mechanism of AtxA-mediated regulation of protective antigen (PA), a component of anthrax toxin encoded by the pagA gene. First, the interaction between the upstream region of pagA and AtxA was evaluated in vivo by constructing a transcriptional fusion of the upstream region with an auxotrophic marker. The results showed that (i) the upstream region of pagA suppressed transcription of the downstream gene and (ii) AtxA recovered suppressed transcription. Second, in vitro analysis using a gel mobility shift assay was performed to evaluate binding specificity of the AtxA–DNA interaction. The result showed sequence-independent binding of AtxA to DNA. Taken together, our findings suggest that the expression of PA was suppressed by the upstream region of pagA and that an interaction of AtxA and the upstream region releases the suppression.