For decades, much of the human DNA was classified as “genetic garbage”: repetitive or apparently unusable sequences, vestiges of past evolutionary processes. However, a new study published in Science Advances demonstrates that many of these fragments have essential regulatory functions and come from ancient viruses that were integrated into our genome millions of years ago.
These fragments, known as endogenous retroviral elements, not only remain active in our DNA, but have evolved to influence how key genes are expressed, especially during the early stages of embryonic development. The finding implies that these genetic waste is, in reality, molecular switches that could have shaped our species and that of other primates.
Four subfamilies to understand our evolutionary history
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The work focused on a concrete family of viral sequences integrated into the human genome: the MER11 elements. Using a detailed phylogenetic approach, scientists redefined these sequences, dividing them into four new subfamilies (mer11_g1 to mer11_g4) according to their age and functional characteristics.
Instead of using automatic annotation tools such as Repeatmasker, the team directly compared thousands of sequences between humans, chimpanzees and macaque, identifying evolutionary conservation patterns that until now had gone unnoticed. This analysis revealed that at least 30 % of these sequences were poorly classified in existing genomic databases.
The youngest subfamily, MER11_G4, showed a remarkable activity in human stem cells, indicating that it could play a key role in gene regulation during early development.
Genetic expression is not a random process. It is controlled by proteins called transcription factors that bind to specific DNA sequences, known as regulatory motifs. The study found that MER11_G4 contains unique reasons – specially of the sox and pou :: Sox2 – type that act as anchor points for these factors, allowing or blocking the activation of certain genes.
The most surprising thing is that some of these regulatory functions seem to have arisen through minimum changes. In one of the cases analyzed, a single nucleotide deletion was sufficient to generate a new functional motive, increasing the ability of that sequence to influence genetic activity.
These differences are particularly notorious in humans and chimpanzees, but not in macaques, which suggests that these viral changes could have had an impact on the differential evolution of each species.
Active and evolving sequences
Beyond their ability to activate genes, researchers also discovered that these sequences interact with the epigenetic environment of cells. That is, they present modification profiles in histones and other chemical brands that regulate access to DNA.
The most recent subfamilies, such as MER11_G3 and G4, showed the most active epigenetic profiles, which suggests that they are not only operational, but continue to adapt and develop new functions. In other words, elements that originally belonged to extinct viruses have been “recruited” by the human genome for vital regulatory tasks.
This type of functional evolution demonstrates that the human genome is not static: it is a dynamic structure that incorporates and modifies external elements for its own benefit, a process that could have had significant repercussions on our differentiation as a species.
A redefinition of “garbage DNA”
This finding drastically changes the perception of the so -called “garbage DNA.” It can no longer be considered a simple evolutionary residue, but a functional file that contains sequences with real impact on our biological development and functioning.
The researchers conclude that the human genome still keeps many secrets. Although it was sequenced more than two decades ago, much of its content is still completely understood. Studies such as this show that many repetitive sequences have functions that we are barely beginning to discover.
By re -examining these elements with new analytical and comparative tools, more connections between our genetic past and the mechanisms that make life as we know it are emerged. The alleged genetic “garbage” is, in reality, to be an active file that keeps the footprints – and the keys – of our evolution.
[Fuente: Muy Interesante]
