Ancient "junk DNA" may be used to prevent future virus infections

Ancient virus fossils are preserved in the genomes of all animals, including humans, and have long been regarded as junk DNA

Researchers at the University of New South Wales in Sydney have tested the DNA and RNA of 13 species of Australian marsupials, and they believe that the virus fossils may help protect animals from infection

“These viral fragments are retained for a reason

"Our research shows how viruses hidden in animal DNA are used to make what we call non-coding RNA, which performs tasks in animal cells, such as protecting animals from external infections

"Animal DNA basically captures the virus sequence, and the virus sequence was once harmful to animals, but ultimately used it for their own benefit

If Ms.

"This may be a mechanism similar to vaccination, but it will be passed on from generation to generation

"If we can prove that it happened to marsupials, then it could also happen to other animals, including humans

Ms.

Evolution rewind

In order to understand how Ms.

Scientists believe that the first marsupials originated in South America and later migrated to Australia through Antarctica

Ms.

"My research looks at the EVEs of Australian marsupials, first to determine which types of viruses have integrated, and secondly to investigate whether they play an active role in marsupial cells

"The virus I discovered comes from the Bornaviridae family (Bornaviridae).

Previously, the Bornaviridae virus was thought to have evolved 100 million years ago

"By understanding how viruses evolve, we can predict their possible changes in the future and plan strategies to prevent epidemics

work

The researchers examined multiple transcriptomes of Tasmanian devil, Tamar wallaby, proboscis, fat-tailed dunnarts, bare-nosed wombat, koala, and sugar mouse—all the RNA collected in one cell
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They also studied the individual transcriptomes of false-backed bandicoots, southern brown bandicoots, striped possums, western dwarf possums, brushtail possums, and yellow-footed rock kangaroos
.

They used the genetic sequences of modern viruses such as Ebola virus and Zika virus to search for matching fragments of ancient marsupial viruses in the transcriptome
.
The advantage of searching through the transcriptome instead of the genome is that it can find segments of the virus that are still "open" and transcribed in the cells of marsupials—generating RNA instead of stagnant fossils
.

Ms.
Harding said: "Transcription is evidence that EVEs are active in cells and may be doing some functional things
.
"

Among the more than 130 known families of viruses, three viruses recur in marsupials
.

Bornaviridae, Filoviridae, and Parvoviridae are commonly found in true mammals (or placental) mammals, including humans
.
Ms.
Harding said that she has found a unique trend in marsupials.
Over time, different parts of the viral genome will remain in the form of fossils
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"Interestingly, the DNA blueprints of the two viral proteins are very common in marsupials
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These two proteins are the nucleocapsid of the virus and an enzyme necessary for replication
.

"Our hypothesis is that these two proteins are good targets for antiviral defense, so their copies are always kept in the genome
.
These copies can block the area of ​​the virus genome that enters, so that the virus cannot make these proteins normally
.
Without these proteins, it cannot replicate and the immune system can clear the infection
.
"

Protected species

The researchers also found evidence of the existence of small RNA molecules that can target and decompose foreign viral RNA chains, which adds more weight to the antiviral hypothesis
.

Ms.
Harding said: "I found that some EVEs spliced ​​out of the genome to produce siRNA and piRNA-two molecules used in the immune system of plants and animals (including humans)
.
"

These RNA molecules are enriched in the testes of male marsupials and may help protect offspring from viral infections
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The development of marsupials is very different from other mammals.
They do not have a fully functional immune system when they are born, so these small molecules may help them protect themselves as they grow
.
"

The study is based on the RNA sequence data of 35 samples of 13 marsupial species
.
Ms.
Harding hopes that future laboratory studies will prove their role in virus immunity, which may lead to the development of new RNA antiviral drugs against multiple viruses
.

The research was recently published in the journal Virus Evolution, and a review was published in the journal Microbiology Australia
.

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