2 articles were published in the journal Nature Microbiology (IF 30.964) are dedicated to functional and mechanism studies of short prokaryotic Argonaute proteins. They crowned the productive collaboration of the Department of Protein-Nucleic acids interactions group, Institute of Biotechnology (BTI), Vilnius University Life Sciences Centre (VU GMC), led by dr. Mindaugas Zaremba and prof. Virginijus Šikšnys, and the Weizmann Institute of Science (Israel) Department of Molecular Genetics, headed by prof. Rotem Sorek.
‘Argonaute (Ago) proteins are found in both prokaryotes (bacteria, archaea) and eukaryotes (including humans), but only eukaryotic Ago (eAgos), which form the functional core of eukaryotic RNA interference (RNAi) and are responsible for regulation of gene expression, silencing of mobile genome elements and defense against viruses, have been studied in detail in functional and structural aspects’, - emphasized the chief scientist Dr. Mindaugas Zaremba.
eAgos use short RNA guides to recognize a complementary mRNA target and either cleave it themselves or target it for further degradation. Meanwhile, prokaryotic Agos (pAgos) are significantly more genetically and structurally diverse than eAgos and have recently attracted much attention as tools for various in vitro and in vivo applications such as DNA manipulation, nucleic acid detection (including SARS-CoV-2 RNA), and fluorescence microscopy. It is believed that mesophilic pAgos could become an attractive and complementary alternative to CRISPR-Cas technology in genome editing in the near future, as they have certain advantages compared to Cas9 nucleases.
The majority of pAgos, the so-called short pAgos, are catalytically inactive, i.e. cannot cleave their target, but are always associated with other effector domains capable of catalysis. ‘Our research was focused on short pAgos associated with Sir2 effector domains, which are found in all kingdoms of life and are involved in various cellular processes’,- said Dr. M. Zaremba. ‘We demonstrated that Sir2-associated short pAgos function as bacterial defence systems against foreign genetic information, i.e. bacteria-infecting viruses (bacteriophages) and plasmids.
Interestingly, short pAgos only act as a sensor when recognizing an invader, but activate the Sir2 domain, which hydrolyzes the cell's vital co-factor NAD+, thus killing the cell and preventing further infection. Thus, by killing itself, the infected cell ‘sacrifices’ itself for the sake of the entire population. Further research will reveal what other functions (besides protection) pAgos perform and what mechanisms are used to perform this, which will undoubtedly contribute to the wider practical application of pAgos’, - the scientist stated.
The published research was carried out implementing the project ‘Molecular mechanisms of novel bacterial antiviral defence systems’ (No. 09.3.3-LMT-K-712-01-0126) of the Research Council of Lithuanian.