Gabija restricts phage circularization and DNA replication

Area of Science:

• Microbiology
• Molecular Biology
• Bacteriophage Research

Background:

• Bacteriophage defense systems like restriction-modification and CRISPR-Cas identify invaders via DNA specificity.
• The mechanism of Gabija, a nuclease-helicase antiphage system, in limiting phage replication and discriminating self from non-self DNA is unclear.

Purpose of the Study:

• To elucidate how the Gabija system distinguishes between self and non-self DNA.
• To understand the role of phage-encoded proteins in Gabija-mediated antiphage activity.

Main Methods:

• Investigated the interaction between Gabija and phage DNA in Pseudomonas aeruginosa.
• Utilized mutant phages lacking specific DNA end-binding proteins.
• Examined the role of the host RecBCD complex in Gabija's activity.

Main Results:

• Phage-encoded DNA end-binding proteins that antagonize host RecBCD sensitize phages to Gabija.
• Gabija prevents the circularization and replication of lambda-like phage genomes.
• Absence of these phage proteins renders phages resistant to Gabija due to RecBCD activity.
• RecBCD activity on linearized bacterial DNA prevents Gabija from targeting self-DNA.

Conclusions:

• Gabija identifies and antagonizes foreign invaders by targeting linear DNA lacking RecBCD.
• Phage DNA end-binding proteins are crucial for Gabija-mediated phage susceptibility.
• RecBCD plays a dual role in protecting bacterial DNA and sensitizing phages to Gabija.