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Simultaneous Mapping and Quantitation of Ribonucleotides in Human Mitochondrial DNA
Published on: November 14, 2017
Processing and editing of overlapping tRNAs in human mitochondria
A Reichert1, U Rothbauer, M Mörl
1Max-Planck-Institute for Evolutionary Anthropology, Institute of Zoology, University of Munich, Luisenstrasse 14, 80333 Munich, Germany.
The Journal of Biological Chemistry
|November 21, 1998
Summary
Mitochondrial tRNA processing in humans involves a unique editing step for overlapping genes. This ensures accurate tRNA maturation, but the mechanism appears species-specific, highlighting evolutionary adaptations in gene processing.
Area of Science:
- Mitochondrial genetics
- RNA processing
- Molecular biology
Background:
- Overlapping transfer RNA (tRNA) genes in metazoan mitochondria pose challenges for polycistronic primary transcript processing.
- Accurate maturation of these transcripts is crucial for mitochondrial protein synthesis.
Purpose of the Study:
- To investigate the processing mechanism of the human mitochondrial tRNA Tyr/tRNA Cys precursor, which contains a one-base overlap.
- To determine the factors involved in recognizing and processing overlapping tRNA genes in human mitochondria.
Main Methods:
- Utilized runoff transcripts and an S100 extract from HeLa cell mitochondria.
- Analyzed the processing of the human mitochondrial tRNA Tyr/tRNA Cys precursor.
- Tested the effect of partial deletion or replacement of tRNA Cys on processing.
Main Results:
- tRNA Cys is released intact, while tRNA Tyr is truncated and subsequently repaired by an editing reaction.
- Recognition by a 3'-endonuclease activity targets the upstream tRNA Tyr, independent of tRNA Cys sequence.
- The processing mechanism is species-specific, as human extract failed to process an opossum mitochondrial precursor.
Conclusions:
- A single enzymatic activity is likely responsible for 3'-end processing of mitochondrial tRNAs, including those with overlaps.
- This processing activity coevolved with the specific tRNA Tyr/tRNA Cys overlap in human mitochondria.
- The observed species-specificity suggests distinct evolutionary pathways for tRNA processing in different metazoans.
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