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Published on: October 14, 2025
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Anti-phage defense mechanism involving phage-encoded DNA binding protein and bacterial reverse transcriptase DRT4
Yong Wang1,2, Hao Wu1,2, Jinyue Li1
1State Key Laboratory of Virology and Biosafety, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China.
Nature Communications
|December 2, 2025
Summary
Prokaryotic defense-associated reverse transcriptase (DRT) systems provide antiviral defense. DRT4 synthesizes random DNA, and phage protein ORF55 aids in this defense by preventing DNA degradation and activating related DRT systems.
Area of Science:
- Molecular Biology
- Structural Biology
- Bacteriology
Background:
- Prokaryotic defense-associated reverse transcriptase (DRT) systems are crucial for antiviral defense but their mechanisms are unclear.
- Understanding these systems is vital for developing novel antibacterial strategies.
Purpose of the Study:
- To elucidate the molecular mechanisms of DRT4-mediated antiviral defense.
- To determine the structural basis for DRT4's function and its interaction with phage proteins.
Main Methods:
- High-resolution cryo-electron microscopy (cryo-EM) to determine DRT4 structures.
- Biochemical analyses to investigate DRT4 activity and substrate binding.
- Infection assays to study the role of phage protein ORF55.
Main Results:
- DRT4 synthesizes single-stranded DNA (ssDNA) in a template-independent manner.
- Cryo-EM structures revealed DRT4's oligomeric architecture and catalytic mechanisms.
- A conserved tyrosine residue was identified as the DNA synthesis priming site.
- Phage protein ORF55 protects DRT4-synthesized ssDNA from degradation and activates DRT6.
Conclusions:
- DRT4 represents a novel antiviral reverse transcriptase mechanism in bacterial immunity.
- ORF55 plays a critical role in DRT4-mediated defense and activates related DRT systems.
- These findings establish a new paradigm for prokaryotic antiviral defense strategies.
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