The Labex Dynamo
2019 Barraud et al.
STo be or not to be modified: miscellaneous aspects influencing nucleotide modifications in tRNAs, IUBMB life.
Barraud et al., 2019
Transfer RNAs (tRNAs) are essential components of the cellular protein synthesis machineries, but are also implicated in many roles outside trans- lation. To become functional, tRNAs, initially transcribed as longer precur- sor tRNAs, undergo a tightly controlled biogenesis process comprising the maturation of their extremities, removal of intronic sequences if pre- sent, addition of the 30 -CCA amino-acid accepting sequence, and aminoacylation. In addition, the most impressive feature of tRNA biogene- sis consists in the incorporation of a large number of posttranscriptional chemical modifications along its sequence. The chemical nature of these modifications is highly diverse, with more than hundred different modifi- cations identified in tRNAs to date. All functions of tRNAs in cells are controlled and modulated by modifications, making the understanding of the mechanisms that determine and influence nucleotide modifications in tRNAs an essential point in tRNA biology. This review describes the differ- ent aspects that determine whether a certain position in a tRNA molecule is modified or not. We describe how sequence and structural determi- nants, as well as the presence of prior modifications control modification processes. We also describe how environmental factors and cellular stresses influence the level and/or the nature of certain modifications introduced in tRNAs, and report situations where these dynamic modula- tions of tRNA modification levels are regulated by active demodification processes.
Publish on : 08/04/2019