Pathogenic Mechanism of a Human Mitochondrial tRNA^Phe Mutation Associated with MERRF syndrome

Authors

Jiaqing Ling, The Ohio State University
Hervé Roy, The Ohio State University
Daoming Qin, The Ohio State University
Mary Anne T. Rubio, The Ohio State University
Juan D. Alfonzo, The Ohio State University
Kurt Fredrick, The Ohio State University
Michael Ibba, Chapman UniversityFollow

Document Type

Article

Publication Date

9-25-2007

Abstract

Human mitochondrial tRNA (hmt-tRNA) mutations are associated with a variety of diseases including mitochondrial myopathies, diabetes, encephalopathies, and deafness. Because the current understanding of the precise molecular mechanisms of these mutations is limited, there is no efficient method to treat their associated mitochondrial diseases. Here, we use a variety of known mutations in hmt-tRNA^Phe to investigate the mechanisms that lead to malfunctions. We tested the impact of hmt-tRNA^Phe mutations on aminoacylation, structure, and translation elongation-factor binding. The majority of the mutants were pleiotropic, exhibiting defects in aminoacylation, global structure, and elongation-factor binding. One notable exception was the G34A anticodon mutation of hmt-tRNA^Phe (mitochondrial DNA mutation G611A), which is associated with MERRF (myoclonic epilepsy with ragged red fibers). In vitro, the G34A mutation decreases aminoacylation activity by 100-fold, but does not affect global folding or recognition by elongation factor. Furthermore, G34A hmt-tRNA^Phe does not undergo adenosine-to-inosine (A-to-I) editing, ruling out miscoding as a possible mechanism for mitochondrial malfunction. To improve the aminoacylation state of the mutant tRNA, we modified the tRNA binding domain of the nucleus-encoded human mitochondrial phenylalanyl-tRNA synthetase, which aminoacylates hmt-tRNA^Phe with cognate phenylalanine. This variant enzyme displayed significantly improved aminoacylation efficiency for the G34A mutant, suggesting a general strategy to treat certain classes of mitochondrial diseases by modification of the corresponding nuclear gene.

Comments

This article was originally published in Proceedings of the National Academy of Sciences of the United States of America, volume 104, in 2007. https://doi.org/10.1073/pnas.0704441104

Recommended Citation

Ling, J., Roy, H., Qin, D., Rubio, M.A., Alfonzo, J.D., Fredrick, K. and Ibba, M. (2007) Pathogenic mechanism of a human mitochondrial tRNA^Phe mutation associated with MERRF syndrome. Proc. Natl. Acad. Sci. USA 104, 15299-15304. https://doi.org/10.1073/pnas.0704441104

Copyright

The National Academy of Sciences of the USA