Mechanisms and Evolution of tRNA 5′-Editing in Mitochondria

The Role of 3′ to 5′ Reverse RNA Polymerization in tRNA Fidelity and Repair

“…DdiTLP3’s role in tRNA 5′-editing also utilizes 3′ to 5′ polymerase function, but to repair mt-tRNA that have been truncated at their 5′-ends due to the removal of one or more incorrectly base-paired nucleotides encoded in the precursor tRNA [49]. This 5′-end repair step is essential for D. discoideum , and likely for many other single-celled eukaryotes that similarly encode mt-tRNA with 5′-mismatches [34,47,49,50,51,52,53,54]. Presumably, the TLPs encoded by these species are capable of participating in 5′-editing, although the identity of specific enzymes that participate in this process has so far only been demonstrated in D. discoideum [32,33,41,42,43,44].…”

“…For this 5′-editing reaction, the ability to act on any tRNA is required, since many different tRNA species contain the genomically encoded 5′-mismatches that must be removed by 5′-editing and then repaired by the TLP prior to participation in translation [34,49,51,52,53]. Indeed, the pattern of tRNA species that have been demonstrated to undergo editing in the many diverse eukaryotes where this process has been investigated so far is quite different from organism to organism, and can involve from only a few species to nearly all of the mt-tRNA, thus suggesting that flexibility in tRNA recognition is important for this function [50]. The idea that some TLPs may act on other non-tRNA substrates also raises new questions for these enzymes and their ability to recognize various RNAs.…”