A bacteriophage nucleus-like compartment shields DNA from CRISPR nucleases

Area of Science:

• Microbiology
• Virology
• Molecular Biology

Background:

• Viruses, including bacteriophages (phages), must overcome host immune defenses to replicate.
• Bacterial immune systems like CRISPR-Cas and restriction-modification target foreign nucleic acids.
• Jumbo phages possess large genomes and complex replication strategies, necessitating robust evasion mechanisms.

Purpose of the Study:

• To investigate the immune evasion strategies employed by the jumbo phage ΦKZ against bacterial defense systems.
• To determine how ΦKZ protects its DNA from host-encoded nucleases during infection.
• To explore the potential for engineering phage susceptibility through compartment manipulation.

Main Methods:

• Infection assays using Pseudomonas aeruginosa and jumbo phage ΦKZ.
• Characterization of the phage-induced proteinaceous compartment.
• Testing the resistance of ΦKZ to various CRISPR-Cas enzymes (Cas3, Cas9, Cas12a, Cas13a) and restriction enzymes (HsdRMS, EcoRI).
• Genetic engineering to relocalize restriction enzymes within the host cell.

Main Results:

• Jumbo phage ΦKZ constructs a nucleus-like protein compartment, sequestering its DNA from host immunity nucleases.
• ΦKZ DNA remained inaccessible to multiple DNA-targeting CRISPR-Cas and restriction enzymes.
• Relocalization of EcoRI into the compartment rendered ΦKZ susceptible to DNA targeting.
• ΦKZ was sensitive to the RNA-targeting CRISPR-Cas enzyme Cas13a, suggesting cytoplasmic localization of phage mRNA.

Conclusions:

• Pseudomonas jumbo phages utilize a proteinaceous compartment to shield their genomes from a wide array of DNA-targeting bacterial immune systems.
• This compartmentalization is a key strategy for efficient phage replication in immune hosts.
• The phage's sensitivity to RNA-targeting systems highlights the importance of mRNA localization in viral infection dynamics.