Argonaute-HNH filaments triggered by invader DNA confer bacterial immunity

Area of Science:

• Molecular Biology
• Immunology
• Biotechnology

Background:

• Argonaute proteins are key to innate immunity, recognizing and cleaving nucleic acids.
• Short prokaryotic Argonautes (pAgos) often lack nuclease activity and require effector proteins for function.
• The activation mechanisms of these pAgo systems remain largely unknown.

Purpose of the Study:

• To characterize SPARHA systems, which comprise short prokaryotic Argonautes (pAgos) associated with HNH nuclease effectors.
• To elucidate the activation pathway and mechanism of SPARHA-mediated bacterial defense.
• To explore the potential biotechnological applications of these modular defense systems.

Main Methods:

• Biochemical characterization of SPARHA systems.
• Analysis of RNA-guided DNA recognition by pAgo.
• Investigation of filament formation and nuclease activity.
• Structural and mechanistic studies of HNH tetramer assembly.

Main Results:

• RNA-guided DNA recognition by pAgo triggers SPARHA filament assembly.
• Filament formation creates chains of double nuclease sites via HNH tetramers.
• This leads to indiscriminate collateral DNA degradation, providing bacterial population defense.
• A conserved, target-induced conformational change cascade activates SPARHA systems.

Conclusions:

• SPARHA systems represent modular defense mechanisms translating specific DNA recognition into a potent immune response.
• The assembly of supramolecular complexes is key to their function against invaders.
• These systems hold potential for biotechnological applications due to their programmable nature.