Amazing stuff!
"... prokaryotic defense systems after he and his colleagues identified archaea-infecting viruses. He reasoned that archaea, like bacteria, would also possess antiviral mechanisms, and these could have been preserved in modern eukaryotes. He started digging into the literature in search of information on archaeal defense systems and the origins of eukaryotic immunity, and came across a perspective paper that piqued his interest: It attributed eukaryotic immune components predominantly to bacteria and only briefly mentioned the existence of archaeal defense proteins. ...
He and his colleagues explored the archaeal defense systems of Asgard archaea, the closest modern prokaryotic relative to eukaryotes, and compared their homology to those of eukaryotes. In a paper published in Nature Communications, the team demonstrated that two classes of defense system proteins found in these archaea are related to those of eukaryotes. The findings offer deeper insight into the origins of early immune systems and how they functioned.
team used a database of prokaryotic defense systems to study the distribution of complete systems in the genomes of archaea, including Asgard archaea, and bacteria. The researchers identified two groups of proteins that were more common in Asgard archaea than in other archaea and bacteria: argonautes, proteins from the RNA-induced silencing complex, and viperins (short for virus-inhibitory protein, endoplasmic reticulum-associated, interferon inducible). ..."
From the abstract:
"Dozens of new antiviral systems have been recently characterized in bacteria. Some of these systems are present in eukaryotes and appear to have originated in prokaryotes, but little is known about these defense mechanisms in archaea. Here, we explore the diversity and distribution of defense systems in archaea and identify 2610 complete systems in Asgardarchaeota, a group of archaea related to eukaryotes. The Asgard defense systems comprise 89 unique systems, including argonaute, NLR, Mokosh, viperin, Lassamu, and CBASS. Asgard viperin and argonaute proteins have structural homology to eukaryotic proteins, and phylogenetic analyses suggest that eukaryotic viperin proteins were derived from Asgard viperins. We show that Asgard viperins display anti-phage activity when heterologously expressed in bacteria. Eukaryotic and bacterial argonaute proteins appear to have originated in Asgardarchaeota, and Asgard argonaute proteins have argonaute-PIWI domains, key components of eukaryotic RNA interference systems. Our results support that Asgardarchaeota played important roles in the origin of antiviral defense systems in eukaryotes."
Fig. 2: Evolutionary history and anti-phage activity of Asgard viperins.
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