The work, published in the journal PNAS, analyzes over 70,000 sequences and strengthens the hypothesis that present-day transfer RNAs evolved from simpler molecules. The genetic code, which determines the correspondence between genetic instructions and the amino acids that form proteins, is one of the major open questions in evolutionary biology.
The study, led by Dr. Lluís Ribas de Pouplana (ICREA at IRB Barcelona) and Dr. Paul Schimmel, has identified conserved signals in tRNAs that could help reconstruct the early stages of this system. tRNAs act as a bridge between genetic instructions and amino acids during protein synthesis. In one region, they contain the anticodon, which recognizes a genetic instruction, and at another end, the corresponding amino acid attaches. The physical distance between these two points in the present-day molecule raises questions about how the evolutionary connection was established.
The researchers analyzed over 70,000 tRNA gene sequences from nearly 5,000 genomes. They compared real sequences with simulated versions to verify if the observed triplets were more frequent than simulations predicted, suggesting they might be remnants of an ancestral system. "The key was to verify that the signal persisted when taking into account the structural constraints of the molecule," explains Dr. Ribas de Pouplana.
The study also compares the intensity of these signals with the proposed chronology for the incorporation of amino acids into the genetic code. The patterns are stronger in tRNAs associated with amino acids incorporated earlier (such as glycine or alanine) and weaker in those incorporated later (such as tyrosine or tryptophan), supporting a progressive development of the genetic code.
The research received funding from the Ministry of Science, Innovation and Universities, the State Research Agency, and European Union ERDF.
