Sir2-domain associated short prokaryotic Argonautes provide defence against invading mobile genetic elements through NAD+ depletion

• Published in: bioRxiv
• Main Authors: Zaremba, Mindaugas, Dakineviciene, Donata, Golovinas, Edvardas, Stankunas, Edvinas, Lopatina, Anna, Sorek, Rotem, Manakova, Elena, Ruksenaite, Audra, Silanskas, Arunas, Asmontas, Simonas, Grigaitis, Rokas, Timinskas, Kestutis, Venclovas, Ceslovas, Siksnys, Virginijus
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 14.12.2021
• Subjects: Cell death; Deoxyribonucleic acid; DNA; NAD; Phages; Plasmids; Prokaryotes; Proteins; RNA-mediated interference
• DOI: 10.1101/2021.12.14.472599

Argonaute (Ago) proteins are found in all three domains of life. The so-called long Agos are composed of four major domains (N, PAZ, MID, and PIWI) and contribute to RNA silencing in eukaryotes (eAgos) or defence against invading mobile genetic elements in prokaryotes (pAgos). Intriguingly, the majority (~60%) of prokaryotic Agos (pAgos) identified bioinformatically are shorter (comprised of only MID and PIWI domains) and are typically associated with Sir2, Mrr or TIR domain-containing proteins. The cellular function and mechanism of short pAgos remain enigmatic. Here, we show that short pAgos from Geobacter sulfurreducens, Caballeronia cordobensis and Paraburkholderia graminis, together with the NAD+-bound Sir2-proteins form a stable heterodimeric Sir2/Ago complex that recognizes invading plasmid or phage DNA through the pAgos subunit and activates Sir2 subunit triggering the endogenous NAD+ depletion and cell death thus preventing the propagation of invading DNA. This is the first demonstration that short Sir2-associated pAgos provide defence against phages and plasmids and underscores the diversity of mechanisms of prokaryotic Agos. Competing Interest Statement R.S. Is the scientific founder of BiomX and Ecophage. The remaining authors declare no competing interests.