Scientists have discovered how our DNA can use a genetic fast-forward button to create new genes to quickly adapt to an ever-changing environment.
While investigating DNA replication errors, researchers at the University of Helsinki in Finland discovered that certain single mutations produce palindromes, which read the same thing before and after. Under the right circumstances, these can develop into: microRNA (miRNA) gene.
These small, simple genes play important roles in the regulation of other genes. Although many miRNA genes have existed for a long time in evolutionary history, scientists believe that in some animal groups, such as primates, A brand new miRNA gene suddenly appears.
“Researchers have been fascinated by how new genes can emerge out of thin air.” To tell Bioinformatician Heli Montinen, lead author of the new study.
“We now have a sophisticated model for the evolution of RNA genes.”
The errors that enable this incredibly efficient method of gene creation are called template switching mutations (TSMs). The miRNA creation process associated with TSM is much faster than the way new functional proteins evolve.
“DNA is copied one base at a time, and a mutation is usually a single incorrect base, like a typo on a laptop keyboard.” To tell project leader and bioinformatician Ari Löytynoja;
“We studied mechanisms that cause larger errors, such as copying and pasting text from another context. We were particularly interested in the case of copying text backwards, creating palindromes. .”
All RNA molecules require a repeating set of bases that lock the molecule into its functional shape. The research team decided to focus on about 22 very short microRNA genes. base pair.
However, even in simple microRNA genes, it is highly unlikely that random base mutations would slowly form this kind of palindrome.
Scientists are puzzled as to where these palindromic sequences came from. It turns out that TSM can rapidly generate complete DNA palindromes and create new microRNA genes from previously non-coding DNA sequences.
“In RNA molecules, adjacent palindromic bases can pair together to form hairpin-like structures. Such structures are critical to the function of RNA molecules.” To tell biotechnologist Mikko Frilander;
The complete genomes of many primates and mammals have already been mapped. By comparing these genomes using a custom computer algorithm, the researchers were able to determine which species have microRNA palindrome pairs.
“When we modeled the history in detail, we found that the entire palindrome was created by a single mutational event,” Montinen said. explain.
The diagram below clearly illustrates the process. DNA replication begins executing each base pair in the recipe list, but stops when it encounters a mutation or defective base pair.
Replication then jumps to adjacent templates and begins replicating those instructions in the opposite direction.
When the replication returns to the original template, it creates a tiny little palindrome that pairs with itself in a hairpin structure.
Template switching during DNA replication allows a single mutational event to create a complete structure of a new miRNA gene within the DNA. This is much more efficient than slow, gradual changes. individual components.
More than 6,000 of these structures have been found in the primate family tree, and they may have given rise to at least 18 entirely new miRNA genes in humans. This represents 26 percent of all miRNAs that are thought to have emerged since primates first appeared.
Such findings across evolutionary lineages point to a universal miRNA gene production mechanism, and the research team believes their results can be applied to other RNA genes and molecules as well.
It appears to be relatively easy for new microRNA genes to emerge that have the potential to impact human health. Several TSM-associated miRNAs have already shown functional importance. hsa-mil-576 This affects the antiviral response of primates.
“Many of the TSM variants that can become miRNA genes are isolated among human populations,” the authors state. write“We show that the TSM process is active and is currently shaping our genome.”
This study Proceedings of the National Academy of Sciences.