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Plant pre-tRNA splicing enzymes are targeted to multiple cellular compartments
Markus Englert1, Andreas Latz, Dirk Becker
1Institute of Biochemistry, Biocenter, University of Würzburg, Am Hubland, D-97074, Würzburg, Germany.
Biochimie
|August 19, 2007
Summary
Plant pre-tRNA splicing enzymes are primarily nuclear, but tRNA ligase and 2'-phosphotransferase also localize to chloroplasts and mitochondria. Differential targeting suggests diverse roles beyond canonical splicing.
Area of Science:
- Molecular Biology
- Plant Biochemistry
- Organelle Biology
Background:
- Pre-tRNA splicing is crucial for tRNA maturation, involving endonuclease, RNA ligase, and 2 -phosphotransferase.
- Subcellular localization of these enzymes varies across eukaryotes (nucleus in vertebrates, cytoplasm in yeast).
Purpose of the Study:
- To determine the subcellular localization of plant pre-tRNA splicing enzymes.
- To investigate the functional implications of observed enzyme localization in plants.
Main Methods:
- Transient expression of plant splicing enzymes fused to Green Fluorescent Protein (GFP) in Allium epidermal and Vicia guard cells.
- Confocal microscopy and colocalization studies using MitoTracker Red.
- Analysis of mutated constructs to assess targeting mechanisms.
Main Results:
- All three classes of splicing enzymes (endonuclease, tRNA ligase, 2 -phosphotransferase) from Arabidopsis and Oryza localize to the nucleus.
- tRNA ligase and 2 -phosphotransferase possess N-terminal chloroplast transit signals, directing them to chloroplasts and proplastids.
- 2 -phosphotransferase also associates with mitochondria, confirmed by colocalization.
Conclusions:
- Plant pre-tRNA splicing predominantly occurs in the nucleus.
- tRNA ligase and 2 -phosphotransferase have dual roles, potentially involved in chloroplast/mitochondrial tRNA repair or atypical intron splicing.
- Alternative translation initiation is a mechanism for differential targeting of these enzymes.
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