Once Believed to Be Junk, Viral Ancient DNA Has Been Ghost Writing Our Genetic Code

We all have one: a junk drawer that we stuff full of all our random — and often useless — items that we can’t throw away. However, once in a while, there’s something in that drawer that ends up being more useful than we initially thought. According to a new study, this is also true for the human body.

Scientists have discovered that ancient “junk” DNA, believed to have freeloaded in our bodies since before we stood on two legs, has actually been working overtime. The new research, published in Science Advances, claims that this previously dismissed genetic junk plays a crucial role in regulating gene expression. 

“Our genome was sequenced long ago, but the function of many of its parts remain unknown,” said Fumitaka Inoue, associate professor at Kyoto University, in a press release. “Transposable elements are thought to play important roles in genome evolution, and their significance is expected to become clearer as research continues.”

In this study, researchers were interested in a particular family of DNA sequences called MER11. This family of sequences is made up of what’s known as transposable elements (TEs), repetitive DNA sequences that originated from ancient viruses. After millions of years of primate evolution, TEs now make up almost half of the human genome thanks to their copy-and-paste-like mechanism.

Although they are prominent throughout the body, TEs haven’t been a major focus of any genetic research for two main reasons. Firstly, the high rate of replication and similarity between copies makes these sequences difficult to study. Secondly, TEs have always been looked at as useless, with no important scientific function even worth investigating. 

Thanks to this new study, TEs are now being recognized for all of the hidden genetic work they’ve been doing. Most notably, the MER11 family of DNA sequences greatly impacts gene expression during early human development.

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Gene expression is a process that turns information into action. One popular way to think about the process of gene expression is like a switch that controls when, where, and how much a molecule or protein gets expressed. These on/off switches control a wide range of genetic functions, from what color your hair is to whether or not your body can properly produce insulin. 

MER11 has now been identified as one of these crucial genetic switches, rewriting the belief that TEs play no important role in our bodies.

Scientists were able to make this surprising discovery using a technique that tests thousands of DNA sequences at a time and measures their influence on gene activity. The research team analyzed over 7,000 MER11 sequences, and these analyses showed that a particular subfamily of MER11 had a significant effect on gene expression, especially related to developmental signals and environmental cues.

Interestingly, MER11 sequences across primates evolved in different ways, with the sequences from humans, chimpanzees, and macaques each being distinct from one another. In future research, the team hopes to continue exploring these evolutionary differences in MER11 between primates to learn more about ancient viral DNA’s complex biological role.

This study is a great reminder that one primate’s junk can be another primate’s (genetic) treasure!

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Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

• Science Advances. A phylogenetic approach uncovers cryptic endogenous retrovirus subfamilies in the primate lineage

As the marketing coordinator at Discover Magazine, Stephanie Edwards interacts with readers across Discover's social media channels and writes digital content. Offline, she is a contract lecturer in English & Cultural Studies at Lakehead University, teaching courses on everything from professional communication to Taylor Swift, and received her graduate degrees in the same department from McMaster University. You can find more of her science writing in Lab Manager and her short fiction in anthologies and literary magazine across the horror genre.