Scientists have discovered nineteen new pieces of DNA left by viruses that infected human ancestors hundreds of thousands of years ago.

Human DNA Deemed Less Human Than Thought

New DNA found in roughly 50 of 2,500 studied

The scientists recently published their work in the Proceedings of the National Academy of Sciences. It their paper the scientists described how they studied the entire genome from 2,500 people located all over the world including a large number of in Africa owing to the migration of humans from Africa to other areas around the world. In addition to the 19 new pieces of DNA found by the team, they confirmed 17 other pieces of virus DNA found by other scientists recently.

The work was funded by the National Institutes of Health and the sophisticated testing of the genome was done at both the University of Michigan Medical School as well as at Tufts University in Boston, Massachusetts.

The genes that were found came from human endogenous viruses that infected our ancestors and placed a DNA-based copy of their RNA into humans. The human immunodeficiency virus is a HERV and is responsible for causing AIDS. The scientists, in their paper, pointed out that they didn’t not now if the virus DNA they found was capable of replicating itself as, well, viruses do.

Not all HERV viruses are necessarily bad, and about 8% of what we mistakenly think of has human genes are actually from viruses. A pregnant woman’s body builds a cell wall around a fetus to protect it from dangerous toxins in her blood, this is one example of a HERV doing more good than harm.

This new finding was found on the X chromosome with the team calling Xq21. With the find it is now the second whole provirus to be found in the human genome and is from a familty of HERV-K viruses.

Scientists speak about their find

“This one looks like it is capable of making infectious virus, which would be very exciting if true, as it would allow us to study a viral epidemic that took place long ago,” says senior author and virologist John Coffin, Ph.D. of the Tufts University School of Medicine. “This research provides important information necessary for understanding how retroviruses and humans have evolved together in relatively recent times.”

“Many studies have tried to link these endogenous viral elements to cancer and other diseases, but a major difficulty has been that we haven’t actually found all of them yet,” says co-first author Zachary H. Williams a Ph.D. student also of Tufts University.  “A lot of the most interesting elements are only found in a small percentage of people, which means you have to screen a large number of people to find them.”

“This is a thrilling discovery said Julia Wildschutte another of the study’s co-authors. “It will open up many doors to research. What’s more, we have confirmed in this paper that we can use genomic data from multiple individuals compared to the reference human genome to detect new HERVs. But this has also shown us that some people carry insertions that we can’t map back to the reference.”

From Tufts to the University of Michigan

The team at the University of Michigan used techniques for studying  the DNA that were developed at Tufts. Much of the study used genomes from the 1000 Genomes Project that was launched internationally in the last decade with more DNA came from the Human Genome Diversity Project which features only genomes from Africans.

Because humans migrated from Africa, their were more HERVs in the African genomes sampled.

It’s likely that additional virus DNA will be found in the future as this team and others continue to look and the hunt becomes cheaper and new technologies are brought to bear on the genomes.