Mechanisms of Toxin Inhibition and Transcriptional Repression by Escherichia coli DinJ-YafQ

• Published in: The Journal of biological chemistry Vol. 289; no. 30; pp. 20559 - 20569
• Main Authors: Ruangprasert, Ajchareeya, Maehigashi, Tatsuya, Miles, Stacey J., Giridharan, Nisha, Liu, Julie X., Dunham, Christine M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25.07.2014; American Society for Biochemistry and Molecular Biology
• Subjects: Bacterial Toxin; Bacterial Toxins - chemistry; Bacterial Toxins - genetics; Bacterial Toxins - metabolism; Crystallography, X-Ray; Energy Metabolism; Escherichia coli - chemistry; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Gene Regulation; Models, Biological; Protein Multimerization - physiology; Protein Structure, Quaternary; Repressor Proteins - chemistry; Repressor Proteins - genetics; Repressor Proteins - metabolism; Ribbon-Helix-Helix Factor; Stress Response; Toxin-Antitoxin Complexes; Transcription Repressor; Transcription, Genetic - physiology; X-ray Crystallography; Energy Metabolism; X-ray Crystallography; Stress Response; Transcription Repressor; Toxin-Antitoxin Complexes; Bacterial Toxin; Ribbon-Helix-Helix Factor
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.573006

Bacteria encounter environmental stresses that regulate a gene expression program required for adaptation and survival. Here, we report the 1.8-Å crystal structure of the Escherichia coli toxin-antitoxin complex YafQ-(DinJ)2-YafQ, a key component of the stress response. The antitoxin DinJ dimer adopts a ribbon-helix-helix motif required for transcriptional autorepression, and toxin YafQ contains a microbial RNase fold whose proposed active site is concealed by DinJ binding. Contrary to previous reports, our studies indicate that equivalent levels of transcriptional repression occur by direct interaction of either YafQ-(DinJ)2-YafQ or a DinJ dimer at a single inverted repeat of its recognition sequence that overlaps with the −10 promoter region. Surprisingly, multiple YafQ-(DinJ)2-YafQ complexes binding to the operator region do not appear to amplify the extent of repression. Our results suggest an alternative model for transcriptional autorepression that may be novel to DinJ-YafQ. Background: Toxin-antitoxin complexes autoregulate transcription depending upon growth conditions. Results: DinJ-YafQ structure was determined, and minimal requirements for transcriptional autorepression were identified. Conclusion: The dinJyafQ operon is regulated in a novel manner by either DinJ-YafQ- or LexA-mediated repression. Significance: Our results reveal new mechanistic insights into the action of DinJ-YafQ as a transcriptional repressor.