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CRISPR-repressed toxin-antitoxin provides herd immunity against anti-CRISPR elements
Xian Shu1, Rui Wang2, Zhihua Li1,3
1Department of Microbial Physiological & Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Nature Chemical Biology
|July 29, 2024
Summary
Bacteria possess a defense mechanism against phage anti-CRISPR factors. A toxin halts cell division when CRISPR-Cas is inhibited, protecting the bacterial population from invaders.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Prokaryotic clustered regularly interspaced short palindromic repeat (CRISPR)-Cas systems are crucial for bacterial immunity.
- These systems are vulnerable to phage-encoded anti-CRISPR (Acr) factors, which neutralize their defense.
- The mechanisms by which CRISPR-Cas systems counteract Acr factors are not fully understood.
Purpose of the Study:
- To uncover a broad-spectrum anti-anti-CRISPR strategy employed by bacteria.
- To investigate the role of phage-derived toxic proteins in this defense mechanism.
- To develop a novel screening method for identifying Acr candidates.
Main Methods:
- Investigated a phage-derived toxic protein whose transcription is regulated by the CRISPR-Cas effector.
- Analyzed the activation of toxin transcription upon inhibition of the CRISPR-Cas effector by Acr proteins or RNAs.
- Developed and applied a screening method to identify specific Acr proteins.
Main Results:
- Discovered a broad-spectrum anti-anti-CRISPR strategy involving a CRISPR-repressed toxin.
- Demonstrated that toxin activation leads to an abortive infection-like effect, expelling Acr elements.
- Identified two novel Acr proteins that enhance CRISPR effector binding to non-target DNA.
Conclusions:
- CRISPR-repressed toxins provide broad-spectrum defense against various Acr factors.
- This regulatory mechanism confers herd immunity to bacterial populations against genetic invaders.
- The discovered mechanism offers a new tool for screening and understanding CRISPR-Cas-Acr interactions.
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