Are the viruses’ friends or enemies or a bit of both ‘frenemies’ shaping our evolution?

By Prof Kuldip Sidhu, PhD, GdipBA

Viruses as switches of our genome (Jumping genes)

Every single gene in our body is regulated by an on and off switch just like light switch and this mechanism is orchestrated very precisely depending on the need with the environment around that gene. For example, sugar in our blood acts as an environment for insulin gene to be turned on thus producing insulin that causes sugar to move from blood to the tissues. Any disturbance in this on/off switch leads to diabetes. Surprisingly some of these switches has been acquired from retroviruses during our evolution.

As indicated above many of the retroviruses that have been acquired into the human genome during our molecular evolution are staying there as ‘transposons’. It has been found out that there is no guaranteed that these transposons will stay put in our genome, occasional mutations in them also allow them to move from one place to other in the genome (jumping genes – fig below) and then influence the turning off or on of switches of nearby genes.  

The first indication of jumping gene was back in the 1950s, by the long-overlooked American geneticist Barbara McClintock, a Noble Laureate,  who revealed that ‘jumping genes’ could affect the genome of maize plants (fig below). Similarly, the endogenous retroviruses that lurk in our own human genome have been on the move over millions of years, jumping around at random and altering the activity of genes in their immediate vicinity.

Retroviral DNA as Jumping gene & first seen its impact in changing maize kernel (image from Google)

In 2016, scientists at the University of Utah found that an endogenous retrovirus in the human genome – which originally came from a virus that infected our ancestors roughly 45 million to 60 million years ago – switches on a gene called AIM2 when it detects a molecule called interferon, which is the ‘danger signal’ that warns the body that it’s suffering a viral infection. AIM2 then forces the infected cells to self-destruct, to prevent the infection from spreading any further.

These ancient viruses have become ‘double agents’, helping our cells to tackle other viruses that are trying to attack us.

It’s becoming clear that the viruses acquired and trapped in our genome have brought us enormous benefits on an evolutionary timescale. But they aren’t all so helpful. Around one in 20 human babies is born with a new viral ‘jump’ somewhere in its genome, which could deactivate an important gene and cause disease. There’s increasing evidence that jumping transposons contribute to the genetic chaos inside cancer cells. And intriguing research suggests that brain cells are particularly good locations for reactivating jumping genes, possibly increasing the diversity of nerve cells and enhancing our brainpower but also potentially causing ageing-related memory problems and conditions such as schizophrenia.

Therefore, evolution is an adaptation to changing environment and the way that organisms respond to changes in the environment, and in that form, they are definitely our friends because they have shaped how our genome works.

And to the question whether HIV, CORONA going to have an impact on our evolution in the future? Of course! The answer is why not. But it will be many generations until we can look back and say this evolution has happened. There is a continuous battle between viruses and organism driving their molecular evolution. 

The COVID Pandemic and Survival of the Fittest – A Perspective

The COVID pandemic has given us a clear view of evolution in action where both the host (humans) and the pathogen (CORONA virus) are in a tug of war to over through each other aiming towards survival of the fittest.  In biological terms, it is now becoming apparent that evolution seems built in our DNA and the environment simply triggers it.  But how it is brought about is a complex process with evolutionary time scale.

When cell or virus replicate, a small percentage of errors (random mutation) occur in duplicating their genetic materials (DNA/RNA), and most of these errors are either neutral or damaging but occasionally other mutations may offer an advantage to the cell and virus. In the current situation such small random mutation in virus offered an advantage to Delta variant of CORONA virus that is spreading fast. Moreover, as it is relatively more successful than the non-mutated variant, the survival of the fittest mechanism may eventually cause the mutated variant to replace the non-mutated form. This process continues in evolution like now we have omicron variant of delta that is less virulent but spreading faster than Delta.

In the same token changes in genome or otherwise may also occur in the host (humans in this case) to protect against CORONA attack. In the short term, those who survived CORONA attack will develop immunity and thus will be protected subsequently against this viral variant (natural immunity). Other those who have been vaccinated will have induced immunity for the same reason. However, if the viral DNA/RNA also get incorporated in our DNA during the pandemic and it may have a long term affects by evolving these inserts as  transposons to protect against these viruses (molecular evolution) and or even perform some other useful function – making us super humans.      

Last but not the least, although modern  medicine has prolonged the life span of humans but that has not necessarily provided a healthy life span (read my previous article where I mentioned that its not CORONA virus per se but human health that is to be blamed for this pandemic)  – an extensive accumulation of bad variations as a genetic burden to human race (counter evolution – working against the theory of survival of the fittest) and that may be  doom and gloom for human race in the long run.