Structural basis of transcriptional activation by the Mycobacterium tuberculosis intrinsic antibiotic-resistance transcription factor WhiB7

• Published in: Molecular cell 2021-07, Vol.81 (14), p.2875-2886.e5
• Main Authors: Lilic, Mirjana, Darst, Seth A., Campbell, Elizabeth A.
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; antibiotic resistance; Bacterial Proteins - genetics; cryo-EM; Cryoelectron Microscopy - methods; DNA-Directed RNA Polymerases - genetics; Drug Resistance, Multiple, Bacterial - genetics; Gene Expression Regulation, Bacterial - genetics; Intrinsic Factor - genetics; iron cluster; Mycobacterium tuberculosis - drug effects; Mycobacterium tuberculosis - genetics; Promoter Regions, Genetic - genetics; RNA polymerase; Sigma Factor - genetics; transcription; transcription factor; Transcription Factors - genetics; transcription initiation; Transcriptional Activation - genetics; WhiB7
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2021.05.017

In pathogenic mycobacteria, transcriptional responses to antibiotics result in induced antibiotic resistance. WhiB7 belongs to the Actinobacteria-specific family of Fe-S-containing transcription factors and plays a crucial role in inducible antibiotic resistance in mycobacteria. Here, we present cryoelectron microscopy structures of Mycobacterium tuberculosis transcriptional regulatory complexes comprising RNA polymerase σA-holoenzyme, global regulators CarD and RbpA, and WhiB7, bound to a WhiB7-regulated promoter. The structures reveal how WhiB7 interacts with σA-holoenzyme while simultaneously interacting with an AT-rich sequence element via its AT-hook. Evidently, AT-hooks, rare elements in bacteria yet prevalent in eukaryotes, bind to target AT-rich DNA sequences similarly to the nuclear chromosome binding proteins. Unexpectedly, a subset of particles contained a WhiB7-stabilized closed promoter complex, revealing this intermediate’s structure, and we apply kinetic modeling and biochemical assays to rationalize how WhiB7 activates transcription. Altogether, our work presents a comprehensive view of how WhiB7 serves to activate gene expression leading to antibiotic resistance. [Display omitted] •Structure of an M. tuberculosis transcription initiation complex with regulator WhiB7•WhiB7 interacts with initiation complex via protein-protein contacts with σ-factor•WhiB7-AT-hook interacts with promoter DNA via upstream AT-rich sequence•WhiB7 activates transcription by stabilizing a closed promoter complex Mycobacteria cause diseases, including tuberculosis. The transcription factor WhiB7 induces resistance to certain antibiotics used for treatment. Lilic et al. provide the structural basis of WhiB7 activity. They show that WhiB7 interacts with DNA similarly to several eukaryotic chromosomal-binding proteins. They also present a structure of a WhiB7-stabilized transcriptional intermediate.