tRNA processing in the mitochondrion

Stable Identifier
Homo sapiens
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Each strand of the circular mitochondrial genome is transcribed to yield long polycistronic transcripts, the heavy strand transcript and the light strand transcript, which are then cleaved to yield tRNAs, rRNAs, and mRNAs (Mercer et al. 2011, reviewed in Suzuki et al. 2011, Rossmanith 2012, Powell et al. 2015). Mitochondrial RNase P, which is completely distinct from nuclear RNase P in having different protein subunits and no RNA component, cleaves at the 5' ends of tRNAs. RNase Z, an isoform of ELAC2 in mitochondria, cleaves at the 3' ends of tRNAs. (A different isoform of ELAC2 serves as RNase Z in the nucleus.) Unknown nucleases make additional cleavages near the 5' end of MT-CO3, the 5' end of CO1, the 5' end of CYB, and the 3' end of ND6. TRNT1 (CCA-adding enzyme) then post-transcriptionally polymerizes the universal acceptor sequence CCA onto the 3' ends of the cleaved tRNAs. In yeast, plants, and protozoa additional tRNAs encoded in the nucleus are imported into mitochondria from the cytosol (reviewed in Schneider 2011), however human mitochondria encode a complete complement of 22 tRNAs required for translation and tRNA import has not been observed in mammals. Mutations that affect mitochondrial tRNA processing cause human diseases that are generally characterized by abnormalities in energy-requiring tissues such as brain and muscle (reviewed in Suzuki et al. 2011, Sarin and Leidel 2014).

Literature References
PubMed ID Title Journal Year
25806043 Nuclear-encoded factors involved in post-transcriptional processing and modification of mitochondrial tRNAs in human disease

Powell, CA, Minczuk, M, Nicholls, TJ

Front Genet 2015
25734984 tRNA biology in mitochondria

Giegé, P, Giege, R, Salinas-Giegé, T

Int J Mol Sci 2015
22137969 Of P and Z: mitochondrial tRNA processing enzymes

Rossmanith, W

Biochim. Biophys. Acta 2012
26016801 Mitochondrial transcript maturation and its disorders

Powell, CA, Minczuk, M, Van Haute, L, Nicholls, TJ, Pearce, SF, D'Souza, AR

J. Inherit. Metab. Dis. 2015
21854988 The human mitochondrial transcriptome

Mattick, JS, Haugen, E, Crawford, J, Neph, S, Mercer, TR, Filipovska, A, Shearwood, AM, Bracken, CP, Rackham, O, Dinger, ME, Stamatoyannopoulos, JA, Smith, MA

Cell 2011
21910628 Human mitochondrial tRNAs: biogenesis, function, structural aspects, and diseases

Suzuki, T, Suzuki, T, Nagao, A

Annu. Rev. Genet. 2011
25692999 Modify or die?--RNA modification defects in metazoans

Leidel, SA, Sarin, LP

RNA Biol 2014
21417719 Mitochondrial tRNA import and its consequences for mitochondrial translation

Schneider, A

Annu. Rev. Biochem. 2011
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