The 3′-termini of tRNA are the point of amino acid linkage and thus crucial for their function in delivering amino acids to the ribosome and other enzymes. Therefore, to provide tRNA functionality, cells have to ensure the integrity of the 3′-terminal CCA-tail, which is generated during maturation by the 3′-trailer processing machinery and maintained by the CCA-adding enzyme.
University of Hamburg researchers developed a new tRNA sequencing method which is specifically tailored to assess the 3′-termini of E. coli tRNA. Intriguingly, they found a significant fraction of tRNAs with damaged CCA-tails under exponential growth conditions and, surprisingly, this fraction decreased upon transition into stationary phase. Interestingly, tRNAs bearing guanine as discriminator base are generally unaffected by CCA-tail damage. In addition, we showed tRNA species-specific 3′-trailer processing patterns and reproduced in vitro findings on preferences of the maturation enzyme RNase T in vivo.
Model for different maturation pathways for tRNA precursors processed by RNase T or RNase PH. Processing by RNase T can lead to CCA-tail damage which needs to be repaired before entering the pool of functional tRNAs for translation.