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Mol. Cell. Biol., Dec 1997, 6831-6837, Vol 17, No. 12
H Hao and CT Moraes
We introduced mitochondrial DNA (mtDNA) from a patient with a mitochondrial
myopathy into established mtDNA-less human osteosarcoma cells. The
resulting transmitochondrial cybrid lines, containing either exclusively
wild-type or mutated (G5703A transition in the tRNA[Asn] gene) mtDNA, were
characterized and analyzed for oxidative phosphorylation function and
steady-state levels of different RNA species. Functional studies showed
that the G5703A mutation severely impairs oxidative phosphorylation
function and mitochondrial protein synthesis. We detected a marked
reduction in tRNA(Asn) steady-state levels which was not associated with an
accumulation of intermediate transcripts containing tRNA(Asn) sequences or
decreased transcription. Native polyacrylamide gel electrophoresis showed
that the residual tRNA(Asn) fraction in mutant cybrids had an altered
conformation, suggesting that the mutation destabilized the tRNA(Asn)
secondary or tertiary structure. Our results suggest that the G5703
mutation causes a conformational change in the tRNA(Asn) which may impair
aminoacylation. This alteration leads to a severe reduction in the
functional tRNA(Asn) pool by increasing its in vivo degradation by
mitochondrial RNases.
Copyright © 1997, American Society for Microbiology
A disease-associated G5703A mutation in human mitochondrial DNA causes a conformational change and a marked decrease in steady-state levels of mitochondrial tRNA(Asn)
Department of Neurology, University of Miami, Florida, USA.
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