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MOSCOW, November 18 / TASS /. Russian and American molecular biologists have discovered an enzyme that helps the most common viruses in the microbiota, the so-called crAss-bacteriophages, to copy their genome and form new viral particles, the press service of Skoltech (the Skolkovo Institute of Science and Technology ) reported Wednesday.
“Since crAss bacteriophages dominate in the human gut microbiota, understanding how they infect microbes will help us manage the microbiota content that affects both human health and the nature of the development of various diseases,” said Maria Sokolova, researcher. at Skoltech, he was quoted by the press service as saying.
Single-celled microbes suffer from diseases and infections just like humans and animals do. Scientists think viruses emerged almost at the same time as bacteria and have been fighting for survival among themselves for hundreds of millions of years. The consequences of this war can be found everywhere. For example, every milliliter of fresh or sea water contains hundreds of millions of bacteriophages, viruses that specialize in infecting microbes. According to current estimates, up to 70% of live bacteria can currently be their carriers. Researchers have long studied their genetics and the mechanism of evolution, however, over the past fifty years it has only been possible to study a small number of both mammalian-threatening viruses and potentially useful bacteriophages.
A good example of this, as Skoltech researchers note, are viruses from the crAss bacteriophage family that was only discovered by biologists in 2014. Scientists later found that these viruses dominate the gut microbiota and play an important role in the its operation.
Another interesting property of crAss bacteriophages is the fact that until recently, researchers did not know how precisely this virus copies its genetic material, forming new particles within infected microbes. As a rule, viruses use so-called RNA polymerases for these purposes – special enzymes that read certain DNA molecules and make their copies in the form of RNA strands.
Evolutionary traces of viruses
Early attempts to find the molecules within the viruses themselves were unsuccessful. This, however, does not prevent the virus from spreading and dominating the microbiota. Russian scientists and their US colleagues attempted to understand how they do this by studying the protein structure of one such virus dubbed phi14: 2.
Scientists discovered a short protein fragment structurally similar to metazoan RNA polymerases. Having encountered this molecule called gp66, biologists have studied its properties, transplanting the coding part of the viral genome into a coliform bacterium.
Subsequent experiments showed that this enzyme actually plays a role in RNA polymerase by copying single strands of DNA. Its mechanism is similar to those enzymes that human cells and cells of other metazoans use for flexible management of gene activity, producing so-called siRNAs. Those are short nucleotide chains that adhere to copies of certain genes and prevent cellular protein “factories” from reading them.
“This is a very surprising result, which means that those proteins responsible for the functioning of siRNAs in the cells of higher organisms may have initially appeared in bacteriophages. In other words, in the distant past our ancestors may have” borrowed “these enzymes from ancient viruses, the ancestors of crAss bacteriophages,” added Skoltech professor Konstantin Severinov.
According to him, this event was not something unique to the evolutionary process of human ancestors who often borrowed the enzymes of various viruses and bacteria in their development process. Furthermore, mitochondria, a kind of cellular powerhouse, were formerly independent bacteria that established symbiotic relationships with the ancestors of protozoa and metazoans and ended up being absorbed by them.
Scientists hope that further research into these viruses and the gp66 enzyme will help use them in solving a range of scientific and medical tasks related to managing the properties of the gut microbiota as well as manipulating DNA and RNA.
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