The fission yeast Schizosaccharomyces pombe has two distinct tRNase Z(L)s encoded by two different genes and differentially targeted to the nucleus and mitochondria

Biochem J. 2011 Apr 1;435(1):103-11. doi: 10.1042/BJ20101619.


tRNase Z is the endonuclease that is involved in tRNA 3'-end maturation by removal of the 3'-trailer sequences from tRNA precursors. Most eukaryotes examined to date, including the budding yeast Saccharomyces cerevisiae and humans, have a single long form of tRNase Z (tRNase ZL). In contrast, the fission yeast Schizosaccharomyces pombe contains two candidate tRNase ZLs encoded by the essential genes sptrz1+ and sptrz2+. In the present study, we have expressed recombinant SpTrz1p and SpTrz2p in S. pombe. Both recombinant proteins possess precursor tRNA 3'-endonucleolytic activity in vitro. SpTrz1p localizes to the nucleus and has a simian virus 40 NLS (nuclear localization signal)-like NLS at its N-terminus, which contains four consecutive arginine and lysine residues between residues 208 and 211 that are critical for the NLS function. In contrast, SpTrz2p is a mitochondrial protein with an N-terminal MTS (mitochondrial-targeting signal). High-level overexpression of sptrz1+ has no detectable phenotypes. In contrast, strong overexpression of sptrz2+ is lethal in wild-type cells and results in morphological abnormalities, including swollen and round cells, demonstrating that the correct expression level of sptrz2+ is critical. The present study provides evidence for partitioning of tRNase Z function between two different proteins in S. pombe, although we cannot rule out specialized functions for each protein.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Nucleus / enzymology
  • Cell Nucleus / metabolism
  • Endoribonucleases / biosynthesis
  • Endoribonucleases / genetics*
  • Endoribonucleases / metabolism*
  • Genes, Fungal*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Microbial Viability
  • Mitochondria / enzymology
  • Mitochondria / metabolism
  • Mutant Proteins / biosynthesis
  • Mutant Proteins / metabolism
  • Nuclear Localization Signals / metabolism
  • Protein Sorting Signals
  • Protein Transport
  • RNA Precursors / metabolism*
  • RNA Processing, Post-Transcriptional
  • RNA, Transfer / metabolism*
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / biosynthesis
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Schizosaccharomyces / cytology
  • Schizosaccharomyces / genetics
  • Schizosaccharomyces / metabolism*
  • Schizosaccharomyces pombe Proteins / biosynthesis
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism*


  • Isoenzymes
  • Mutant Proteins
  • Nuclear Localization Signals
  • Protein Sorting Signals
  • RNA Precursors
  • Recombinant Fusion Proteins
  • Recombinant Proteins
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • RNA, Transfer
  • Endoribonucleases
  • tRNase Z, S cerevisiae