American and Canadian biologists have discovered an unusual group of proteins that viruses use to protect against the so-called cellular "antivirus". These proteins can be used to protect not only cells, but entire organisms from changes in their DNA.
According to Alan Davidson of the University of Toronto, scientists have not attempted to find protection against CRISPR. Instead, they tried to understand how phage viruses fit into bacterial genomes. As a result of research, biologists have discovered something that may be of great importance in the future, in the development of biotechnology. Such a CRISPR "blocker" will give scientists control over when, where, and how to edit DNA.
As a reminder, the CRISPR / Cas9 genome editor was named the main scientific breakthrough of 2015. It was created several years ago by the American scientist Feng Zhang and a group of molecular biologists. Since its inception, this editor has been modernized several times, so that it can be used with 100% accuracy for genome editing.
Objectively speaking, the CRISPR / Cas9 editor, like many other things, was not invented by man, but by nature. A similar system hundreds of millions of years ago developed inside bacteria and was used to protect against retroviruses, and it was only in 2012 that scientist Zhang and his colleagues tried to adapt it to editing the genome of multicellular organisms. This genomic editor consists of several components - the Cas9 enzyme, which has certain sequences in the body's DNA and can remove them if necessary, and directly samples of the genetic code of CRISPR viruses.
Alan Davidson and his colleagues were able to discover that viruses created a kind of response to the CRISPR / Cas9 editor. This is a set that consists of three proteins that cling to different parts of the Cas9 enzyme and neutralize it until the moment when it cuts the virus DNA from the microbe's genome.
These proteins were discovered by chance, Davidson said. Scientists have observed how different versions of bacteriophage viruses penetrate into meningococcal cells (the causative agents of meningitis that are actively used to protect against CRISPR / Cas9 viruses).
As it turned out, some bacteriophages contain three proteins that were not previously known to scientists - acrIIC1, acrIIC2 and acrIIC3. After further research, it was found that these proteins are able to bind to the Cas9 protein molecules, thereby neutralizing them and preventing the recognition of viral RNA or DNA and destroying them.
After scientists identified the genes responsible for the production of these proteins and placed them in the cells of the human body, the DNA of these cells was protected - further attempts to change the genetic code using CRISPR / Cas9 were blocked by the proteins of bacteriophages.
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This discovery is of great interest to scientists, as it allows scientists to control the process of genome editing using the CRISPR / Cas9 editor. In turn, this will make it possible to create new, safe methods of gene therapy for the treatment of congenital diseases, to produce pure genetically modified organisms from the point of view of genetics, as well as to implement many other things that previously simply could not be done due to scientists' ignorance of how to control the work of this genomic editor.
In addition, from the evolutionary point of view, the discovery of the DNA "anti-editor" allows us to explain another mystery - why, in the case of such a high efficiency of the CRISPR / Cas9 system, viruses did not become extinct? It was found that viruses created their biological "antivirus" in the form of molecules that suppress its work.