Physics Colloquium

The decoding machinery of present-day organisms converts genetic information into functional proteins through a process of amino acids polymerization called translation. The rules of the genetic code indicate which amino acids are added onto a nascent protein during the translation of the codons of RNA templates (mRNAs). This process presents an apparent paradox: the genetic code is established by proteins (the aminoacyl-tRNA synthetases, aaRSs) that are themselves built according to the rules of this same code. These proteins bind amino acids onto the 3' end of their corresponding tRNAs, which subsequently participate in the translation process on the ribosome.
In order understand why coding rules are associated with this particular polymerization process, it is appropriate to reduce the complexity of the system and try to establish a simpler form of translation that would still retain the essence of the phenomenon, but make its physical and chemical basis more clear. This could lead to the identification of a primitive form of the genetic system that might have emerged at the origin of Life.
In this talk, I will show that the organization of the genetic code provides important clues for the characterization of the initial translation system. I will also present the result of experiments showing that particular RNAs are capable of self-catalyzing the attachment of amino acids onto their 3' ends. These experiments suggest that small RNAs might be able to establish an initial translation system without proteins.