CBASS phage defense and evolution of antiviral nucleotide signaling

Area of Science:

• Microbiology
• Immunology
• Molecular Biology

Background:

• Cyclic oligonucleotide-based antiphage signaling system (CBASS) is a prevalent defense mechanism in prokaryotes against viral predation.
• CBASS operons encode cGAS/DncV-like Nucleotidyltransferase (CD-NTase) enzymes and Cap effector proteins that mediate antiviral responses.
• Activation involves CD-NTase synthesizing nucleotide second messengers upon detecting viral infection, leading to Cap effector-mediated cell death.

Purpose of the Study:

• To elucidate the precise rules governing the activation and function of CBASS immunity.
• To understand the molecular mechanisms underlying CBASS-mediated antiphage defense.
• To compare CBASS with other prokaryotic and eukaryotic immune systems for evolutionary insights.

Main Methods:

• Comparative genomic and bioinformatic analyses of diverse CBASS systems.
• Biochemical assays to characterize CD-NTase activity and Cap effector binding.
• Functional studies in bacterial model systems to validate defense activation pathways.

Main Results:

• Defined the molecular requirements and signaling cascades for CBASS activation.
• Demonstrated the critical role of nucleotide second messengers in triggering cell death.
• Established a framework for understanding CBASS regulation and effector function.

Conclusions:

• CBASS represents a sophisticated and conserved prokaryotic defense system with tunable activation thresholds.
• The study provides a foundation for understanding the evolution of nucleotide signaling in host-virus interactions.
• Comparative analysis with CRISPR, Pycsar, and cGAS-STING highlights conserved and divergent strategies in innate immunity.