Why Is AUG the Start Codon?: Theoretical Minimal RNA Rings: Maximizing Coded Information Biases 1st Codon for the...

Area of Science:

• Molecular Biology
• Origin of Life Research
• Bioinformatics

Background:

• The universal start codon AUG is fundamental to protein synthesis, but its origin remains unexplained.
• Theoretical minimal RNA rings are proposed as candidate ancestral genes that may hold clues to early genetic codes.

Purpose of the Study:

• To investigate whether a rational design of theoretical minimal RNA rings can predetermine AUG as the universal start codon.
• To explore if this design maximizes coded amino acid diversity and confers essential gene and tRNA-like properties.

Main Methods:

• In silico design and analysis of theoretical minimal RNA rings.
• Evaluation of RNA ring sequences for coding capacity, start codon usage, and structural stability (stem-loop hairpin formation).
• Assessment of properties mimicking primordial RNA constraints.

Main Results:

• Twenty-five theoretical minimal RNA rings met the design constraints, coding for 21 amino acids and a stop codon.
• Ten of these RNA rings initiated with the universal start codon AUG, with no bias among the remaining rings.
• The RNA ring design inherently predisposed AUG as the initiation codon and conferred degradation-delaying properties.

Conclusions:

• The rational design of minimal RNA rings provides a potential explanation for AUG's universal role as the start codon.
• This design approach successfully maximizes amino acid diversity and identifies candidate ancestral genes with primordial RNA-like characteristics.