Researchers at the MRC Laboratory of Molecular Biology (LMB) have discovered a tiny RNA molecule that could explain how life on Earth began.
The findings, published in the journal Science, reveal the team has identified a remarkably small RNA molecule, named QT45, that can copy itself and its complementary strand – a key step toward self-replication.
How life emerged from simple chemical building blocks remains one of science’s greatest questions.
One leading theory suggests that RNA molecules spontaneously formed in a ‘primordial soup’ and began replicating and evolving.
Until now, scientists had only found RNA strands capable of copying other RNA, but these were too long and complex to be able to copy themselves.
Because copying RNA is a complicated process involving a cascade of sophisticated molecular interactions, it had also been widely assumed that only large and complex RNA molecules would be capable of such a feat.
The LMB team’s discovery of QT45, a short RNA polymerase ribozyme, changes that. Its small size means not only that it is much easier for QT45 to copy itself, but also that it could plausibly have appeared spontaneously. Together, this discovery supports the hypothesis that life could have started with self-replicating RNA.
The team’s breakthrough was achieved by generating vast pools of random RNA sequences and selecting those with RNA-copying activity. Through repeated rounds of laboratory evolution, QT45 emerged as a highly efficient ribozyme. Researchers confirmed its ability to copy diverse RNA sequences and ultimately to synthesize itself and its complementary strand.
Lead author Edoardo Gianni explained: “This research offers a glimpse into what the earliest steps of life might have looked like and deepens our understanding of the fundamental molecules that underpin all living systems.
“Everyone in this field had been working on the same ribozyme lineage for over 30 years and believed that finding a new one would be very difficult, and that it had to be a long RNA sequence to carry out its function.
“By identifying a small RNA, it makes the whole idea that self-replicating RNA emerged spontaneously much more likely, and thanks to its size, it managed to copy all of itself and its template – unlike previous work where only small parts were copied.”
Now that the team have successfully demonstrated experimentally the two key reactions needed for self-replication, they have now set their sights on combining the two reactions to kickstart a self-replication cycle.
Edoardo added: “Beyond its scientific significance the discovery also has implications with regards to how likely life is to emerge spontaneously and whether similar processes could occur on other planets.”
Paper
A small polymerase ribozyme that can synthesize itself and its complementary strand by Edoardo Gianni et al in Science.
Edoardo Gianni, Samantha L. Y. Kwok, Christopher J. K. Wan, Kevin Goeij, Bryce E. Clifton, Enrico S. Colizzi, James Attwater, Philipp Holliger.
