Partitioning of the Nuclear and Mitochondrial tRNA 3′-End Processing Activities between Two different Proteins in Schizosaccharomyces pombe

Abstract

Background: Most eukaryotes contain only one tRNase Z gene involved in both nuclear and organellar tRNA 3Ј-end maturation. Results: Schizosaccharomyces pombe has two tRNase Z genes required for nuclear and mitochondrial tRNA 3Ј-end processing, respectively. Conclusion: The evolution of two tRNase Z genes and their differential expression in fission yeast may avoid toxic off-target effects. Significance: The results advance our understanding of tRNA 3Ј-end maturation.

The S. pombe mitochondrial transcriptome

“…We also investigated the role of S. pombe Trz2 in mt-RNA processing using RNA-seq, which allows comprehensive analysis of the 5 ′ -and 3 ′ -ends of all mt-tRNAs. The data derived from RNA-seq have been verified by comparing them with our previous data obtained with Northern blotting (Zhang et al 2013). We found that while trz2 deletion blocks the 3 ′end processing of all mt-tRNAs, it has varying effects on mt-tRNAs.…”

“…The role of tRNase Z L in mt-RNA processing has been studied in S. cerevisiae (Skowronek et al 2014), S. pombe (Zhao et al 2009(Zhao et al , 2010Fan et al 2011;Wang et al 2012;Zhang et al 2013;Zhou et al 2014), Drosophila (Xie and Dubrovsky 2015) and human (In humans, tRNase Z L is named ELAC2) (Brzezniak et al 2011;Sanchez et al 2011). These studies firmly establish that tRNase Z L is responsible for mt-tRNA 3 ′ -end processing.…”

“…We have previously shown by Northern blot analysis that inactivation of trz2 affects 3 ′ -end processing of mt-tRNA Lys(UUU) , mt-tRNA Arg(ACG) , and mt-tRNA His(GUG) (Zhang et al 2013). To determine whether inactivation of trz2 affected genome-wide mt-tRNA 3 ′ -end processing, we constructed and sequenced cDNA libraries from mt-tRNA of the wild-type strain and trz2-1 mutant, which harbors a temperature-sensitive allele of trz2 (Zhang et al 2013). The 5 ′ -and 3 ′ -extended precursor mt-tRNAs were defined by the presence of at least 5-nt 5 ′ -flank and at least 5-nt 3 ′ -flank of mature mt-tRNAs, respectively.…”

“…We have previously shown that unlike S. cerevisiae, Drosophila and human, which contain a single tRNase Z L localized to both the nucleus and mitochondria, S. pombe has two tRNase Z L s encoded by two different essential genes which are responsible for nuclear and mitochondrial tRNA 3 ′ -end processing, respectively (Zhao et al 2009;Gan et al 2011;Zhang et al 2013). However, a comprehensive landscape of S. pombe mitochondrial transcriptome is still lacking.…”

Factors That Shape Eukaryotic tRNAomes: Processing, Modification and Anticodon–Codon Use

“…First, some species have two genes encoding proteins that modify or process cytosolic or mitochondrial tRNAs differentially, and others use specific isoforms of a single gene product to do so, although there may be no readily apparent evolutionary consistency of the patterns. For example, in most eukaryotes including S. cerevisiae, Drosophila and humans, one tRNase Z (L–refers to long form) gene encodes both nuclear and mitochondrial forms of tRNase Z (L), the enzyme that cleaves the trailer sequences from the 3′ ends of tRNA precursors, whereas (all four) Schizosaccharomyces species contain two essential tRNase Z (L) genes whose products are targeted either to the nucleus or mitochondria [161]. Thus, gene duplications may account for some expansions of tRNA associated enzymes in isolated lineages or species, but with no apparent consistency predictive of outcome without functional studies.…”