AUTHOR=Yin Liwen , Liu Qi , Pan Xiaolei , Lv Chenjing , Bai Yuxi , Bai Fang , Cheng Zhihui , Wu Weihui , Ha Un-Hwan , Jin Yongxin 

TITLE=MvaT binds to the PexsC promoter to repress the type III secretion system in Pseudomonas aeruginosa

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1267748

DOI=10.3389/fcimb.2023.1267748

ISSN=2235-2988

ABSTRACT=<p><italic>Pseudomonas aeruginosa</italic> is an opportunistic human pathogen capable of causing a variety of acute and chronic infections. Its type III secretion system (T3SS) plays a critical role in pathogenesis during acute infection. ExsA is a master regulator that activates the expression of all T3SS genes. Transcription of <italic>exsA</italic> is driven by two distinct promoters, its own promoter P<italic><sub>exsA</sub></italic> and its operon promoter P<italic><sub>exsC</sub></italic>. Here, in combination with a DNA pull-down assay and mass spectrometric analysis, we found that a histone-like nucleoid-structuring (H-NS) family protein MvaT can bind to the P<italic><sub>exsC</sub></italic> promoter. Using EMSA and reporter assays, we further found that MvaT directly binds to the P<italic><sub>exsC</sub></italic> promoter to repress the expression of T3SS genes. The repression of MvaT on P<italic><sub>exsC</sub></italic> is independent of ExsA, with MvaT binding to the -429 to -380 bp region relative to the transcription start site of the <italic>exsC</italic> gene. The presented work further reveals the complex regulatory network of the T3SS in <italic>P. aeruginosa</italic>.</p>