Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 119, Issue 17, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2116429119
Keywords
chemical nucleotide activation; RNA copying; origin of life; RNA world hypothesis; prebiotic chemistry
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Funding
- Simons Foundation [290363]
- NSF [CHE-1607034]
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Nonenzymatic template-directed RNA copying using chemically activated nucleotides may have played a crucial role in the emergence of genetic information on early Earth. Recent experiments have shown that multiple freeze-thaw cycles in a reaction mixture can facilitate nucleotide activation, synthesis of imidazolium-bridged dinucleotides, and template-directed RNA copying. These findings suggest that environmental fluctuations, such as freeze-thaw cycles, could have been important in prebiotic nucleotide activation and nonenzymatic RNA copying.
Nonenzymatic template-directed RNA copying using chemically activated nucleotides is thought to have played a key role in the emergence of genetic information on the early Earth. A longstanding question concerns the number and nature of different environments that might have been necessary to enable all of the steps from nucleotide synthesis to RNA copying. Here we explore three sequential steps from this overall pathway: nucleotide activation, synthesis of imidazolium-bridged dinucleotides, and template-directed RNA copying. We find that all three steps can take place in one reaction mixture undergoing multiple freeze-thaw cycles. Recent experiments have demonstrated a potentially prebiotic methyl isocyanide-based nucleotide activation chemistry. However, the original version of this approach is incompatible with nonenzymatic RNA copying because the high required concentration of the imidazole activating group prevents the accumulation of the essential imidazolium-bridged dinucleotide. Here we report that ice eutectic phase conditions facilitate not only the methyl isocyanide-based activation of ribonucleotide 5'-monophosphates with stoichiometric 2-aminoimidazole, but also the subsequent conversion of these activated mononucleotides into imidazolium-bridged dinucleotides. Furthermore, this one-pot approach is compatible with template-directed RNA copying in the same reaction mixture. Our results suggest that the simple and common environmental fluctuation of freeze-thaw cycles could have played an important role in prebiotic nucleotide activation and nonenzymatic RNA copying.
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