Discovery of strange activity of ancient virus DNA in the human body

Unleashed at the most vulnerable times of health, remnants of some ancient viruses unleash unexpected effects.

Scientists from the Children's Medical Center Research Institute (CRI) at the University of Texas at Southwestern have discovered ancient viral DNA in the human genome that behaves in unexpected ways during pregnancy and when there is significant blood loss.

Coming from epidemics our ancestors suffered, the remnants of ancient viruses are often referred to as " junk DNA" because they do not encode proteins that contribute to cellular function.

They use an enzyme called reverse transcriptase , just like the human immunodeficiency virus (HIV), to copy themselves.

However, this work, recently presented in the scientific journal Science, shows that they are not necessarily "garbage".

DNA from ancient viruses brings unexpected value to humans - (Illustration by AI: ANH THU).

They are strongly linked to the way blood-forming stem cells – which normally divide irregularly – are activated during pregnancy and after blood loss.

When they compared the genes active in stem cells from pregnant mice with those from non-pregnant mice, they found that "retrotransposons" - ancient viral DNA - were activated in stem cells from pregnant mice.

Humans have evolved mechanisms to block retrotransposons for most of their lives, because retrotransposons have the ability to damage DNA as they copy and insert themselves back into other parts of the genome.

The body's sudden "unleashing" of these foreign DNAs during pregnancy is completely unexpected, because that is the most important time to protect the integrity of the genome and avoid mutations.

'There are hundreds of these retrotransposon sequences in our DNA. Why not permanently disable them, like some species have done? They must have some adaptive value to us,' the authors argue.

They used reverse transcriptase inhibitors, commonly used to block HIV replication in patients, to inhibit retrotransposon replication in mice.

The results were completely unexpected: These drugs did not alter blood cell production in normal mice, but they blocked the increase in hematopoietic stem cells and red blood cell production during pregnancy, leading to anemia.

These "junk DNAs" also trigger certain immune sensors, increasing the production of interferons, an important group of immune system proteins that help reduce inflammation, fight invading viruses and bacteria, and also indirectly affect blood production.

Testing on several volunteers later confirmed the surprising value of the DNA from the ancient virus.

In addition, scientists discovered that a similar mechanism also occurs in cases of severe blood loss, suggesting that these so-called "garbage" things may have more roles in human health than we think.