Science reports:

About 30 million years ago, a virus infected our primate ancestors and one of its genes got trapped in their genomes. Over time, this viral gene became “domesticated”—and territorial. It helped primates fight off other viruses by preventing them from entering cells. The invader—known as Suppressyn (SUPYN)—is still around today, and it’s still helping us out: A new study reveals that this viral turncoat might help the placenta protect embryos from viral infection.

“It’s a beautiful story supported by very strong experiments,” says Giulia Pasquesi, an evolutionary biologist at the University of Colorado, Boulder, who was not involved with the work. Finding more such viral genes, she says, might help us harness or boost our inherent antiviral properties without the need to develop new drugs or vaccines. “There are all of these elements we already have in our genome.”

Viruses that embed their genetic material in our genome are known as retroviruses. HIV is probably the most famous example; once integrated into our genes, it hijacks our body’s cellular machinery to produce more viruses. If they infect sperm cells or oocytes, the precursors of eggs, their genes become part of our DNA and can be passed on to our offspring.

Once a snippet of viral DNA becomes embedded in our genome, it’s known as an endogenous retrovirus (ERV). About 8% of the human genome consists of ERV sequences that have been trapped in our DNA ever since they infected a human ancestor millions of years ago. These genes have lost their original viral function over time, but that doesn’t mean they’re useless. [Continue reading…]