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Potential role of a CRISPR-Cas-activated toxin-antitoxin system in bacterial immunity

Jiyun Chen1, Linglong Huang2, Hong Chen2

  • 1State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, China. chenjiyun@xmu.edu.cn.

Nature Communications
|June 26, 2026
PubMed

Insights

This study reveals functional synergy between CRISPR-Cas13a and HicAB toxin-antitoxin systems in E. coli, enhancing antiviral defense. Cas13a activates HicB, inhibiting phage growth, while CRISPR RNA neutralizes HicA toxin.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Prokaryotic antiviral defense involves CRISPR-Cas and toxin-antitoxin systems.
  • Toxin-antitoxin systems typically limit phage propagation via toxin-induced growth arrest or reduced fitness.
  • Antitoxins neutralize toxin activity in standard toxin-antitoxin systems.

Purpose of the Study:

  • Investigate the functional synergy between CRISPR-Cas13a and a Leptotrichia bacterium's HicAB type II toxin-antitoxin system.
  • Examine this synergy when heterologously expressed in E. coli.
  • Conduct biochemical and structural analyses to elucidate the mechanism.

Main Methods:

  • Heterologous expression of CRISPR-Cas13a and HicAB in E. coli.
  • Biochemical assays to assess protein interactions and activities.
  • Structural analyses (e.g., cryo-EM) to determine complex formations.

Main Results:

  • The antitoxin HicB demonstrated toxic properties.
  • Cas13a directly activated HicB, leading to growth inhibition and phage protection.
  • Cas13a binding promoted HicB tetramer proximity, facilitating activation.
  • HicA toxin competitively inhibited Cas13a-mediated HicB activation.
  • Both CRISPR RNA and HicB suppressed HicA toxicity.
  • CRISPR RNA formed a complex with HicAB, neutralizing HicA's toxic function.

Conclusions:

  • Functional synergy exists between CRISPR-Cas13a and HicAB systems for enhanced bacterial antiviral defense.
  • Cas13a acts as an activator for the HicAB system, integrating distinct defense mechanisms.
  • CRISPR RNA plays a dual role in neutralizing toxin activity and potentially modulating the complex.

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