Maturation of tRNAs and their dynamics between the nucleus and the cytoplasm

Abstract

tRNAs, a class of small RNAs essential for translation, were thought to be stable molecules partly because of their indispensable roles in gene expression. However, when looking at the early part of their life, one may notice that tRNAs receive various and extensive processing for their maturation despite of their rather short bodies with around 80 nucleotides. In this century, researchers have been piling up facts that the processing steps of tRNAs are carried out both in the nucleus and in the cytoplasm, and that even the steps carried out in the nucleus, which include transcription as the first step, are finely arranged in sub-nuclear compartments. In parallel, it has been demonstrated that tRNAs are actually mobile molecules in the cell during and even after their maturation. Recent reports also describe that the amount and repertoire of tRNAs are regulated to cope with changes of both intracellular and extracellular physiological conditions. These findings now change the image of tRNAs from house-keeping molecules to dynamic molecules in various aspects. In this review, I will mainly overview two dynamics of tRNAs among several dynamics attracting interest of researchers in these years; the dynamics of molecular shape during tRNA maturation and the intracellular dynamics of tRNAs, especially focusing on their dyamics in the nucleus, which is an important place for tRNA maturation. I will also provide fundamental knowledge to prospect for future development of tRNA research.