Losing the stem-loop structure from metazoan mitochondrial tRNAs and co-evolution of interacting factors

Abstract

Conventional tRNAs have highly conserved sequences, four-armed cloverleaf secondary structures, and L-shaped tertiary structures. However, metazoan mitochondrial tRNAs contain several exceptional structures. Almost all tRNAsSer for AGY/N codons lack the D-arm. Furthermore, in some nematodes, no four-armed cloverleaf-type tRNAs are present: two tRNAsSer without the D-arm and 20 tRNAs without the T-arm are found. Previously, we showed that in nematode mitochondria, an extra elongation factor Tu (EF-Tu) has evolved to support interaction with tRNAs lacking the T-arm, which interact with C-terminal domain 3 in conventional EF-Tu. Recent mitochondrial genome analyses have suggested that in metazoan lineages other than nematodes, tRNAs without the T-arm are present. Furthermore, even more simplified tRNAs are predicted in some lineages. In this review, we discuss mitochondrial tRNAs with divergent structures, as well as protein factors, including EF-Tu, that support the function of truncated metazoan mitochondrial tRNAs.

Mitochondrial tRNA-lookalikes in nuclear chromosomes: Could they be functional?

“…18,27 The mitochondrial aaRS have a MLS that allows them to enter the mitochondrion whereas nuclear/ cytoplasmic aaRS cannot aminoacylate mitochondrial tRNAs. Two exceptions are worth noting here: the aaRS for Lys and Gly can process both mitochondrial and cytoplasmic tRNAs.…”

“…This is particularly true of mitochondrial tRNAs that may, for example, lack the T and the D loop. 18,34 Addressing all such considerations will necessitate additional and likely lengthy studies that go beyond the scope of the perspective put forth in this study.…”

Acytota – associated kingdom of neglected life

“…The translation apparatus, probably, gradually evolved from (GCU) n still bearing some semblance to it, rather than appearing at once, complete with some ancestral complexity. Simplified tRNA structures of mitochondria (Watanabe et al, 2014) are, probably, also snapshots of past stages of the gradual process of evolution of the translation apparatus. The evolution of the Acytota, likely, proceeded in parallel with cellular evolution, as it is, obviously happening today.…”

Caenorhabditis elegans as a research tool to study mitochondrial diseases associated with defects in tRNA modification

“…Los tRNAs que carecen del brazo T tienen un bucle de sustitución, denominado bucle TΨV, que sustituye el brazo T y la región variable. No obstante, gracias a una modificación post-transcripcional en la A de la posición 9 (m 1 A), éstos pueden plegarse en una estructura similar a la de los tRNAs canónicos (Wolstenholme et al 1987;Ohtsuki and Watanabe 2007;Watanabe et al 2014). …”

“…Hay que señalar que el ensayo de digestión por angiogenina del tRNA mitocondrial de C. elegans ha resultado menos sensible que la digestión de los tRNAs mitocondriales humanos descrita en el trabajo de nuestro grupo arriba mencionado (Martínez-Zamora et al 2015). Esta menor sensibilidad del ensayo puede ser debida a la conformación atípica de los tRNAs mitocondriales de los nematodos (Wolstenholme et al 1987;Watanabe et al 1994;Watanabe et al 2014). Ya se ha descrito previamente que los ensayos de sensibilidad a endonucleasas pueden variar de manera importante dentro de los tRNAs del mismo organismo y respecto a la misma especie de tRNA entre organismos diferentes (Lu et al 2005;Lu et al 2008).…”