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Scientists from the University of Helsinki have made significant progress in understanding the evolution of microRNA genes, providing insights into how new genes can arise from seemingly nonfunctional DNA sequences. This research, recently published in PNAS, delves into the origins of small regulatory genes, particularly focusing on the creation of DNA palindromes and their evolution into functional microRNA genes.
Deciphering the Origin of Genes
The human genome, with approximately 20,000 protein-coding genes, is regulated by numerous smaller genes, including those that encode microRNAs, which are only 22 base pairs in length. While the overall gene count remains fairly stable, the emergence of new genes is a phenomenon that has long intrigued scientists. The team at the University of Helsinki's Institute of Biotechnology has now illuminated a pathway for the creation of these new genes.
Palindromes in DNA: The Key to New Gene Formation
A central aspect of this research is the understanding of palindromic sequences in DNA. These sequences, which read the same forward and backward, are crucial for the functional structure of RNA molecules. However, the natural formation of these palindromes, particularly in microRNA genes, has been a mystery due to the low probability of random mutations leading to such structures.
Innovative Research Techniques and Insights
The Helsinki team, funded by the Academy of Finland, employed a novel approach by studying errors in DNA replication. According to Ari Löytynoja, the project leader, these errors can be likened to typos in text, sometimes resulting in larger errors akin to copying and pasting text backward, forming a palindrome. This concept was further explored in collaboration with Mikko Frilander, an expert in RNA biology, who recognized the significance of palindrome structures in RNA molecule functionality.
The research team employed custom computer algorithms to model the gene history, enabling an unprecedentedly detailed inspection of gene origins. Heli Mönttinen, a postdoctoral researcher, emphasized the significance of this approach. “The whole genome of tens of primates and mammals is known,” stated Mönttinen. “A comparison of their genomes reveals which species have the microRNA palindrome pair, and which lack it. With a detailed modeling of the history, we could see that whole palindromes are created by single mutation events.”
Concentrating on humans and various primates, the Helsinki research team showed that the recently discovered process could account for about a quarter of the new microRNA genes. This mechanism's presence in different evolutionary branches suggests it is a universal phenomenon.
The emergence of microRNA genes is seemingly straightforward, indicating that these new genes might have implications for human health. Mönttinen views the importance of this research in a wider context, such as its role in comprehending the fundamental principles of life.
“The emergence of new genes from nothing has fascinated researchers. We now have an elegant model for the evolution of RNA genes,” she emphasized.
Moreover, the researchers believe that this discovery opens up possibilities for understanding complex RNA structures and functions, influenced by natural selection using the raw materials provided by this mechanism.