Yet as foreign as viruses may seem, the boundary between them and us is turning out to be remarkably blurry. We use DNA from viruses to do things that are essential to our own survival, scientists are finding. Somehow, we have managed to domesticate some of these invaders.
Endogenous retroviruses first invaded the cells of our primate ancestors more than 50 million years ago. Scientists have identified over 100,000 of these fragments in the human genome, accounting for 8 percent of our
To fight invading viruses, a cell needs to turn on many genes at once. The genetic switches that make this possible are stretches of DNA next to each gene, which are themselves activated by proteins.
The scientists edited the DNA of human cells they grew in a dish, chopping out some of the viral switches near interferon-responsive genes. Then they exposed those cells to interferon. The immunity genes, they found, barely woke up.