Anti-virus system found in giant mimi viruses

Giant mimiviruses are protected from foreign organisms using a system similar to CRISPR , as in bacteria and other microorganisms, discovered by French researchers from the University of Ex-Marcel. They say that the presence of an active immune system in mimiviruses makes it possible to isolate them into a separate over-kingdom of organisms, along with eukaryotes, bacteria and archaea.

Mimiviruses are so large that they are visible in a conventional optical microscope. About 0.5 micrometers in size, they first "lit up" in front of scientists in 1992, when they infected amoebas in a water tower. At the same time, the size of the mimivirus genome is larger than that of those very bacteria.

Unlike viruses, mimiviruses possess genes for the production of amino acids and complex proteins of proteins - they are made from protein threads, similar to flagella. A detailed study of the most complex mimivirus genome is still ongoing.
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Mimiviruses occupy an intermediate position between viruses and microbes, mimicking the latter (hence the name).

Like prokaryotes (microbes), mimirus is susceptible to virus attacks - virophages. This is a French biologists found in 2008. In 2014, the same group of scientists determined that the virophage - it was called Zamilon - affects only certain types of mimiviruses, but not others. After a defeat, the mimic loses the ability to make copies of itself.

Scientists have suggested that such infections can lead to the formation of a protective system of the CRISPR type.

CRISPR in prokaryotes is a database of short DNA fragments that correspond to phages and other harmful organisms. When the alien DNA, the sample of which is present in the signature database, attacks the cell, specialized 'Cas' enzymes are sent to the violator and break its DNA into pieces. By the way, now the CRISPR technique is used by geneticists as a way of editing the genome . In humans, it will be tested in 2017 .

To test their theory, French genetics analyzed the genomes of 60 copies of the mimivirus. They searched for sequences that correspond to the Zamilon virusof genome, that is, anti-virus system signatures. It turned out that such signatures are in the genome of mimi viruses that are resistant to infection. Then we found the genes that encode the corresponding enzymes. In the end, for the final check, scientists blocked these genes, after which the mimirus was infected with a virophage. This is clear evidence of the existence of the immune system in mimiviruses. She was called MIMIVIRE.


MIMIVIRE protection system

The scientific work was published February 29, 2016 in the journal Nature ( doi: 10.1038 / nature17146 ), a mirror .