More ancient viruses lurk in our DNA than we thought

http://www.eurekalert.org/pub_releases/2016-03/uomh-mav032216.php

Public Release: 22-Mar-2016
More ancient viruses lurk in our DNA than we thought
One whole endogenous retrovirus genome -- and bits of 17 others -- were spotted in a study of 2,500 human genomes
University of Michigan Health System

Think your DNA is all human? Think again. And a new discovery suggests it's even less human than scientists previously thought.

Nineteen new pieces of non-human DNA -- left by viruses that first infected our ancestors hundreds of thousands of years ago -- have just been found, lurking between our own genes.

And one stretch of newfound DNA, found in about 50 of the 2,500 people studied, contains an intact, full genetic recipe for an entire virus, say the scientists who published their findings in the Proceedings of the National Academy of Sciences.

Whether or not it can replicate, or reproduce, it isn't yet known. But other studies of ancient virus DNA have shown it can affect the humans who carry it.

In addition to finding these new stretches, the scientists also confirmed 17 other pieces of virus DNA found in human genomes by other scientists in recent years.

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In fact, about 8 percent of what we think of as our "human" DNA actually came from viruses. In some cases, HERV sequences have been adopted by the human body to serve a useful purpose, such as one that helps pregnant women's bodies build a cell layer around a developing fetus to protect it from toxins in the mother's blood.

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