Argonaute-HNH filaments triggered by invader DNA confer bacterial immunity

Le résumé fourni par la source

Argonaute proteins provide innate immunity in all domains of life through guide-dependent recognition and cleavage of invader nucleic acids. Many short prokaryotic Argonautes (pAgos) lack nuclease activity and are instead co-encoded with tentative nuclease effectors, but their activation mechanisms remain unknown. Here, we characterize SPARHA systems (short prokaryotic argonautes, HNH-associated), containing HNH nuclease effectors. RNA-guided target DNA recognition by pAgo induces formation of SPARHA filaments with a chain of double nuclease sites formed by HNH tetramers, leading to indiscriminate collateral degradation of DNA and protecting bacterial population from invaders. We show that the assembly of filaments proceeds via a universal activation pathway involving a cascade of target-induced conformational changes in SPARHA, conserved in other short pAgo systems containing various types of effectors. pAgos and associated effectors act as modular defense systems that translate recognition of specific DNA into immune response through assembly of supramolecular complexes, deleterious for invaders and potentially useful for biotechnology. Argonaute proteins degrade specific invader nucleic acids in eukaryotic and prokaryotic innate immunity. Here, Kanevskaya et al. describe a bacterial immune system in which RNA-guided recognition of invader DNA by Argonaute triggers formation of HNH nuclease filaments with collateral activity, protecting the bacterial population from invaders.

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