Endogenous Retroviruses

Maliha Tanjum Chowdhury
Junior
School of Life Sciences
Independent University, Bangladesh

“I am terrified by this dark thing
That sleeps in me;
All day I feel its soft, feathery turnings, its malignity.”

Like the poetess Sylvia Plath who wrote these lines, men of wisdom have always recited one thing time and time again: that there are monsters living inside us. I, for one, am sure that I am haunted. Every cell in me, in fact, is haunted… But before I go any further, I must ask – how many of you here believe in things such as monsters, ghosts or demons? Can you please raise your hand? Hmm, not many I see. But that’s alright, because in the span of the next three minutes, I am sure I will have made believers out of all of you. And so begins my story.

Let me take you back to a time around 500 million years ago. Down below in earth’s seven seas, life is flourishing without bounds. Several types of complex, multicellular animals have already evolved. But, while the realm of the living thrives, an enemy lurks in every corner of this vast kingdom. A creature that stands as an exclusion to life itself, as it does not eat, digest, or excrete like any of the living creatures. It is a tiny vessel of protein holding in its genetic material with just one purpose – to invade and multiply. These tiny yet monstrous entities are called viruses. 

Endogenous retroviruses in sharks, the oldest surviving jawed vertebrates, and other existing organisms helped determine the time of origin of retroviruses

Now, around the time of our story, a special new kind of virus came into being. In their war against animal cells, viruses typically employ an explosive battle strategy where they invade and pillage the cells, and then leave it to die. But these new viruses, called retroviruses, refrained from taking such a crude approach. Retroviruses, which still persist, incorporate their genetic material right into the host DNA, hiding in plain sight. The cell is now "possessed" by this monster, which slowly but often surely consumes its host instead of killing it right away. The most-well known retrovirus, HIV, does this to our immune cells, rendering them non-functional, and giving people AIDS.

Things look bleak for the poor besieged cell, but it is about to get much worse. Retroviruses which get woven into the DNA of germline cells, which include sperm and egg cells, gain the ability to be transferred into the animal’s babies as well – and thus, family curses are born. Animals do not sit idle, and have evolved to harbor defenses to deactivate these retroviruses, but remnants of the viral genetic material linger on in the host. Millions of years down the line, these invading genes are just specters. But specters need not remain silent. The descendants of the ancient infected hosts have unwittingly crafted quite the revenge. In a human cell, the pieces of DNA that were once invaders now assist the cell in obliterating other viruses that try to infect us.

The story of the ancient battle between the living realm and the unliving viruses will never truly reach an end  But these ghosts from the past have helped us get where we stand today. Embrace your inner monster, because in the end, it has only made you stronger.

Sources to explore more:



Maliha is a weirdo who somehow believes she's from a different planet. But she likes Earth just fine, and is fascinated by the science and beauty of life and has made it her purpose to explore it. Besides this, her most burning desires include becoming a synthetic biologist/ genetic engineer and running away with a heavy metal band.

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