The transcriptional regulator CasR controls mycobacterial antioxidant defense and biofilm formation via multiple direct targets.

Huizi Chen; Yuanpeng Li; Jiachen Zheng; Xiaolin Liu; Jie Lu; Weihui Li

doi:10.1093/jambio/lxag210

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The transcriptional regulator CasR controls mycobacterial antioxidant defense and biofilm formation via multiple direct targets.

Huizi Chen·Yuanpeng Li·Jiachen Zheng·Xiaolin Liu·Jie Lu·Weihui Li

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Abstract

AIMS: The antioxidant defense system of Mycobacterium tuberculosis is critical for pathogenicity and persistence within macrophages, yet the regulatory networks remain poorly understood. This study aims to elucidate the molecular mechanism by which the transcription factor CasR regulates antioxidant defense in mycobacteria through delineation of the regulatory axis linking CasR activity, target gene expression, and the antioxidant phenotype. METHODS AND RESULTS: Using Mycobacterium smegmatis as a model organism, we demonstrate that overexpression of CasR renders the bacteria significantly susceptible to hydrogen peroxide. Electrophoretic mobility shift assay (EMSA) and β-galactosidase reporter analyses reveal that CasR directly binds and represses the promoter of cyp144, an uncharacterized cytochrome P450-encoding gene. Deletion of casRMsmreduces biofilm formation, consistent with the expected derepression of cyp144Msm, a gene that negatively regulates both biofilm and oxidative stress tolerance. EMSA and β-galactosidase activity assays also demonstrate that CasR negatively regulates antioxidant gene katGI, suggesting that CasR exerts a broader, global regulatory role within the mycobacterial antioxidant defense network. Furthermore, we identify isoleucine 18 as a critical residue for the DNA-binding and regulatory function of CasR. CONCLUSION: This study establishes CasR as a pleiotropic transcriptional regulator that directly controls multiple antioxidant genes, including cyp144 and katGI, in mycobacteria. We report a previously unrecognized role for a cytochrome P450 family member in suppressing bacterial antioxidant capacity, as cyp144 overexpression reduces biofilm formation. These findings provide a valuable reference for further investigation into mycobacterial antioxidant mechanisms and identify CasR and Cyp144 as potential targets for the development of anti-tuberculosis drugs.

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Biofilms Mycobacterium smegmatis Gene Expression Regulation, Bacterial Bacterial Proteins Antioxidants Oxidative Stress Transcription Factors Hydrogen Peroxide Promoter Regions, Genetic Cytochrome P-450 Enzyme System Mycobacterium tuberculosis Electrophoretic Mobility Shift Assay antioxidant defense cytochrome p450 transcription factor Journal Article

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Huizi Chen, Yuanpeng Li, Jiachen Zheng, Xiaolin Liu, Jie Lu, Weihui Li. 2026-09-02. The transcriptional regulator CasR controls mycobacterial antioxidant defense and biofilm formation via multiple direct targets.. https://doi.org/10.1093/jambio%2Flxag210

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