Scientists have long tried to determine what the function of the viral DNA “fossils” (which are embedded in the genes of humans) truly is. Now, a recent study published in the journal Science shows that the viral DNA actually act as enhancers for genes in human cells, specifically in the expression of Interferon-induced genes that are crucial for the regulation of the immune system.
Around 8 percent of the human genome is actually derived from viral DNA, technically termed as “Endogenous retroviruses” or EVRs. It is assumed that several million years ago, a type of virus, known as a retrovirus, infected cells of humans (or its predecessor) and incorporated its own foreign genetic information into the chromosome of the cell. The retrovirus also infected sperm cells and egg cells, which meant that the viral DNA that was incorporated into the genome was passed down from generation to generation; thus, making retrovirus and the genetic information that was inserted into the genome “endogenous.”
In the study, the researchers scanned different human cell lines for EVRs that are associated to interferon-induced genes important to the innate immunity of an organism. They were able to find thousands of EVRs, suggesting a link between these viral genetic sequences to the immune system. This notion was confirmed when the EVRs were snipped out of the genome of cells using the gene-editing tool CRISPR. After doing so, there was a significant dysfunctionality that was observed in the transcription factors that enhance the expression of certain genes important in the immune response.
As quoted in Science, lead author Edward Chuong, a computational biologist at the University of Utah in Salt Lake City, said that the research distinctly shows that “an ancient viral element is assisting us against an infection,” adding that the next challenge is to see if the same results could be obtained in a living mouse model.