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A phage weaponizes a satellite recombinase to subvert viral restriction
Maria H T Nguyen1, Zoe Netter1, Angus Angermeyer1
1Department of Plant and Microbial Biology, University of California, Berkeley, 271 Koshland Hall, Berkeley, CA 94720, USA.
Nucleic Acids Research
|October 19, 2022
Summary
Bacteria use mobile genetic elements (MGEs) like phage-inducible chromosomal island-like elements (PLEs) to fight phages. We found a new phage mechanism, Adi, that exploits bacterial PLEs to overcome their defenses.
Area of Science:
- Microbiology
- Bacteriology
- Genetics
Background:
- Bacteria utilize mobile genetic elements (MGEs) to defend against viral infections (phages).
- Phage-inducible chromosomal island-like elements (PLEs) in *Vibrio cholerae* are MGEs that restrict phage replication, benefiting the host bacterium.
- PLEs parasitize the lytic phage ICP1, employing multiple defense mechanisms against it.
Purpose of the Study:
- To investigate the CRISPR-independent mechanism by which specific ICP1 phage isolates overcome PLE restriction.
- To identify and characterize the ICP1-encoded factor responsible for subverting PLE-mediated defense.
Main Methods:
- Genetic analysis of ICP1 isolates exhibiting resistance to PLE restriction.
- Biochemical assays to characterize the interaction between ICP1-derived factors and PLE components.
- Functional studies involving PLE's large serine recombinase (LSR) and its attachment site (attP).
Main Results:
- Discovery of ICP1-encoded Adi, a factor that counteracts PLEs via a CRISPR-independent mechanism.
- Adi exploits the PLE's large serine recombinase (LSR) to promote nuclease activity at the LSR's attachment site (attP).
- The PLE LSR, its catalytic activity, and attP are sufficient to sensitize a resistant PLE variant to Adi.
Conclusions:
- ICP1 has evolved a novel mechanism (Adi) to overcome bacterial phage defenses by hijacking the PLE's own mobilization machinery.
- This represents a unique adaptation in inter-genomic conflicts, where a protein's intended function is weaponized.
- Understanding these interactions provides insights into viral evolution and bacterial defense strategies.
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