The RNA world hypothesis suggests that life originated when RNA molecules developed the ability to replicate themselves. Recent research has uncovered a promising RNA molecule that can perform key replication steps, bringing us closer to understanding the origins of life.
Philipp Holliger, from the MRC Laboratory of Molecular Biology in Cambridge, UK, describes the discovery as a significant milestone in demonstrating RNA’s potential for self-replication. In living cells, DNA stores genetic information for making proteins, while RNA can fold into enzyme-like structures that catalyze chemical reactions. This unique property led scientists to hypothesize that early life forms may have relied on self-replicating RNA molecules.
The search for such molecules has been challenging, as researchers initially believed they would be large and complex. However, the team led by Holliger took a different approach by creating a trillion random RNA sequences of varying lengths. They identified a 45-nucleotide molecule, named QT45, capable of performing key replication reactions in specific conditions.
In alkaline water just above freezing, QT45 can use single-stranded RNA as a template to generate complementary strands by joining short nucleotide sequences. While the process is slow and inefficient, it represents a crucial step towards self-replication. The team aims to further evolve QT45 and explore different conditions, like freeze-thaw cycles, to optimize the replication process.
The ability of QT45 to generate variations through error-prone replication could lead to self-optimization, where more efficient variants emerge over time. Experts like Sabine MĂĽller from the University of Greifswald and Zachary Adam from the University of Wisconsin-Madison praise the findings as a significant advancement towards fully self-replicating RNA molecules.
On early Earth, molecules similar to QT45 could have thrived in environments resembling modern-day Iceland, with ice, hydrothermal activity, and pH gradients. Compartmentalization mechanisms, such as cell-like vesicles or ice pockets, would have been crucial for isolating key components for replication.
The discovery of QT45 showcases the potential of small RNA molecules in the origins of life, highlighting the vast possibilities within the realm of RNA chemistry. As scientists continue to unravel the mysteries of RNA replication, we inch closer to understanding the fundamental processes that kickstarted life on Earth.
