Processing of eukaryotic tRNA precursors: secondary structure of the precursor specific sequences affects the rate but not the accuracy of processing reactions.

The primary transcriptional product of eukaryotic tRNA genes is a precursor molecule with extranucleotides at the 5' and at the 3' end. We show that the 5' and 3' sequences, uniquely present in the RNA precursor molecule do not play any role in the efficiency and accuracy of processing reactions. If, however, as a consequence of in vitro manipulation, these extranucleotides form a base-paired extension of the aminoacid acceptor stem, the rate of processing is slowed down. The rate of processing is brought back to normal in a single base-pair deletion mutant probably as a consequence of a destabilization of the base-paired extension of the aminoacid acceptor stem.