Researchers from the University of Michigan Medical School and Tufts University in Medford, Massachusetts have discovered 19 never-before-seen pieces of genetic material in human DNA that were left behind by viruses that once infected our ancestors, according to a new study.
Writing in the latest edition of the journal Proceedings of the National Academy of Sciences, the authors explained analyzing 2,500 human genomes led to the discovery of genetic fragments left behind by members of the human endogenous retrovirus group HERV-K.
Among those DNA remnants was the complete and intact genetic recipe for an entire virus that was detected in nearly 50 of the 2,500 study participants, the researchers said. It is currently not known whether or not the newfound pathogen can reproduce, they added, but previous research involving ancient virus DNA indicates that it can affect the humans carrying it.
Their analysis, which looked at the entire genome from people around the world (including many from Africa, the birthplace of modern human ancestors), also confirmed the presence of 17 other pieces of viral DNA previously discovered in the human genome by other scientists.
Study could shed new light on evolution of retroviruses
The UM/Tufts University group compared specific regions of each individual’s genomes to a “reference” human genome to discovered the viruses, which belong to the same group as the modern human immunodeficiency virus (HIV). These viruses entered human DNA during the ancient past and were copied and passed from one generation to the next.
In fact, as much as eight percent of our genome originally came from viruses, the researchers explained in a statement. In some instances, our bodies have adopted them and used them for some beneficial purpose – for example, one helps the bodies of pregnant women build a layer that protects their unborn children from toxins found in the mother’s blood.
The researchers discovered the whole viral genome or provirus on the X chromosome. Dubbed Xq21, it is only the second intact provirus found in the human genome. Senior author Dr. John Coffin, a virologist at Tufts University, said that it appears to be able to make infectious viruses, a discovery which he said would be “very exciting” if confirmed by additional research.
Dr. Coffin added that the research “provides important information necessary for understanding how retroviruses and humans have evolved together in relatively recent times.” His colleague Dr. Julia Wildschutte, co-first author of the paper, called it “a thrilling discovery” which could “open up many doors to research,” including studies of HERV evolution and diseases.
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Image credit: University of Michigan
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