Template-Free Assembly of Functional RNAs by Loop-Closing Ligation

Area of Science:

• Origin of Life Studies
• Molecular Evolution
• RNA Biochemistry

Background:

• Early RNA replication likely involved nonenzymatic template copying.
• Functional RNAs possess complex folded structures, posing challenges for replication.
• Inhibition of ribozyme function by complementary strands is a key evolutionary hurdle.

Purpose of the Study:

• To reconcile the need for complex RNA structures with early replication mechanisms.
• To investigate pathways for assembling functional ribozymes without external templates.
• To address the challenge of template-mediated inhibition in early RNA systems.

Main Methods:

• Nonenzymatic cross-strand ligation of short RNA duplexes with overhangs.
• Conversion of duplexes into RNA stem-loop structures.
• Loop-closing ligation reactions for assembling full-length ribozymes.

Main Results:

• Demonstrated nonenzymatic conversion of RNA duplexes into stem-loop structures.
• Showcased assembly of functional ribozymes via loop-closing ligation.
• Established a template-free pathway for complex functional RNA formation.

Conclusions:

• Proposes a plausible pathway for the emergence of complex functional RNAs in early evolution.
• Suggests that early protocell genomes could have comprised collections of short replicating oligonucleotides.
• Provides a mechanism for overcoming replication challenges and template inhibition in early RNA-based life.