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Updated: Jun 27, 2026
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Detection of the pH-dependent Activity of Escherichia coli Chaperone HdeB In Vitro and In Vivo
Published on: October 23, 2016
Oligomer disassembly activates an HEPN-containing bacterial defense system
Yiwen Tang1, Ting Liu1, Chao Xiong1
1Department of Biotherapy, Cancer Center and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
Molecular Cell
|June 25, 2026
Summary
Bacteria use a novel defense system, "Dandelion," that activates RNase activity when protein structures disassemble, unlike typical immune systems where assembly triggers signaling. This discovery challenges existing paradigms in bacterial immunity.
Area of Science:
- Microbiology
- Molecular Biology
- Evolutionary Biology
Background:
- Bacteria and phages engage in an evolutionary arms race, driving diverse antiviral defense strategies.
- Nucleic acid degradation is a key bacterial defense mechanism against phage infection.
Purpose of the Study:
- Investigate a novel Higher Eukaryotes and Prokaryotes Nucleotide-binding (HEPN) domain-containing defense system in Escherichia coli.
- Elucidate the unique activation mechanism of this bacterial antiviral system.
Main Methods:
- Characterization of a dodecameric, autoinhibited defense system.
- Identification of phage single-stranded DNA-binding (SSB) protein as a trigger.
- Phylogenetic analysis of SSB proteins to understand phage resistance specificity.
Main Results:
- The defense system, named "Dandelion," is activated by oligomer dissociation, releasing RNase activity.
- Phage SSB protein triggers the Dandelion system's activation.
- Phylogenetic analysis revealed specificity in phage resistance mediated by SSB proteins.
Conclusions:
- The Dandelion system employs a counterintuitive activation mechanism: oligomer disassembly.
- This finding challenges the established model where protein oligomerization typically activates immune signaling.
- The study reveals a new paradigm in bacterial antiviral defense strategies.
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