ROS-sensing Transcription Factor YchJ Regulates RssB-RpoS Pathway to Protect Salmonella Against Oxidative Attack by Macrophages

Structural analysis revealed that ROS sensing by YchJ is achieved through reversible dimerization mediated by an intermolecular disulfide bond. This conformational switch enables a C-terminal basic-rich region of the dimer to recognize a palindromic sequence in the rssB promoter and repress rssB transcription. Dual-transcriptome analysis further confirmed that YchJ directly activates antioxidant defenses in Salmonella and significantly disrupts host pathways during intramacrophage infection.

Our findings elucidate a previously unrecognized redox-sensing pathway essential for bacterial virulence and uncover a novel transcriptional mechanism controlling RpoS stability, thereby expanding our understanding of the stress-response regulation system in pathogenic bacteria.