Circular code motifs in the ribosome: a missing link in the evolution of translation?
Fiche publication
Date publication
septembre 2019
Journal
RNA (New York, N.Y.)
Auteurs
Membres identifiés du Cancéropôle Est :
Dr POCH Olivier, Dr THOMPSON Julie
Tous les auteurs :
Dila G, Ripp R, Mayer C, Poch O, Michel CJ, Thompson JD
Lien Pubmed
Résumé
The origin of the genetic code remains enigmatic five decades after it was elucidated, although there is growing evidence that the code co-evolved progressively with the ribosome. A number of primordial codes were proposed as ancestors of the modern genetic code, including comma-free codes such as the RRY, RNY or GNC codes (R = G or A, Y = C or T, N = any nucleotide), and the X circular code, an error-correcting code that also allows identification and maintenance of the reading frame. It was demonstrated previously that motifs of the X circular code are significantly enriched in the protein-coding genes of most organisms, from bacteria to eukaryotes. Here, we show that imprints of this code also exist in the ribosomal RNA (rRNA). In a large-scale study involving 133 organisms representative of the three domains of life, we identified 32 universal X motifs that are conserved in the rRNA of >90% of the organisms. Intriguingly, most of the universal X motifs are located in rRNA regions involved in important ribosome functions, notably in the peptidyl transferase center and the decoding center that form the original 'proto-ribosome'. Building on the existing accretion models for ribosome evolution, we propose that error-correcting circular codes represented an important step in the emergence of the modern genetic code. Thus, circular codes would have allowed the simultaneous coding of amino acids and synchronization of the reading frame in primitive translation systems, prior to the emergence of more sophisticated start codon recognition and translation initiation mechanisms.
Mots clés
circular code, genetic code, origin of life, ribosome evolution, translation
Référence
RNA. 2019 Sep 10;: