Cyclic nucleotide signaling in phage defense and counter-defense

Januka S. Athukoralage, Malcolm F. White*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Advances in our understanding of prokaryotic antiphage defense mechanisms in the past few years have revealed a multitude of new cyclic nucleotide signaling molecules that play a crucial role in switching infected cells into an antiviral state. Defense pathways including type III CRISPR (clustered regularly interspaced palindromic repeats), CBASS (cyclic nucleotide-based antiphage signaling system), PYCSAR (pyrimidine cyclase system for antiphage resistance), and Thoeris all use cyclic nucleotides as second messengers to activate a diverse range of effector proteins. These effectors typically degrade or disrupt key cellular components such as nucleic acids, membranes, or metabolites, slowing down viral replication kinetics at great cost to the infected cell. Mechanisms to manipulate the levels of cyclic nucleotides are employed by cells to regulate defense pathways and by viruses to subvert them. Here we review the discovery and mechanism of the key pathways, signaling molecules and effectors, parallels and differences between the systems, open questions, and prospects for future research in this area.
Original languageEnglish
Pages (from-to)451-468
Number of pages18
JournalAnnual Review of Virology
Early online date13 May 2022
Publication statusPublished - Sept 2022


  • Antiviral defense
  • Cyclic nucleotide
  • Abortive infection


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