Upstream sequence-dependent suppression and AtxA-dependent activation of protective antigens in Bacillus anthracis

Kochi Toyomane; Yoshikazu Furuta; Daisuke Fujikura; Hideaki Higashi

doi:10.7717/peerj.6718

Upstream sequence-dependent suppression and AtxA-dependent activation of protective antigens in Bacillus anthracis

PeerJ. 2019 Apr 12:7:e6718. doi: 10.7717/peerj.6718. eCollection 2019.

Authors

Kochi Toyomane¹, Yoshikazu Furuta¹, Daisuke Fujikura¹, Hideaki Higashi¹

Affiliation

¹ Division of Infection and Immunity, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan.

Abstract

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.

Keywords: AtxA; Bacillus anthracis; Gene silencing; Protective antigen; Transcription factor.

Grants and funding

This work was supported by grants-in-aid for JSPS Fellows (Grant Number 17J01377) from the Japan Society for the Promotion of Science (JSPS) and by the Program for Leading Graduate Schools (F01) and the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) from the Japanese Ministry of Education, Culture, Sports, Science and Technology. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.