A Proposal of the Ur-RNAome

Area of Science:

• Biochemistry
• Molecular Biology
• Origin of Life Studies

Background:

• The earliest RNA molecules are hypothesized to have folded into hairpin or mini-helix structures.
• The RNY triplet hypothesis by Eigen proposes a primeval genetic code based on RNA.

Purpose of the Study:

• To depict the 2D and 3D conformations of early RNA molecules composed solely of RNY triplets.
• To investigate the structural stability and evolutionary precursors of RNA in early life forms.

Main Methods:

• Analysis of 2D and 3D conformations of RNA molecules containing only RNY triplets.
• Comparative free energy analysis of RNY hairpins versus shuffled controls in 26 species (13 bacteria, 13 archaea).
• Bioinformatic identification of RNA structures and sequences.

Main Results:

• RNY hairpins exhibited consistently lower free energy than their shuffled counterparts, indicating structural stability.
• Traces of ribosomal RNAs (16S, 23S, 5S), tRNAs, 6S RNA, RNase P, and signal recognition particle RNA were detected.
• Absence of the peptidyl transferase centre and anti-Shine-Dalgarno sequences indicated no genetic code or protein synthesis.
• Anticodons for glycine (GCC) and threonine (GGU) were identified within proto-tRNA hairpins.

Conclusions:

• Early RNA molecules likely existed as stable hairpins based on RNY triplets.
• These structures represent precursors to modern RNAs, predating the emergence of a functional genetic code and protein synthesis.
• The findings provide insights into the structural and functional evolution of RNA in the very early stages of life.