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To whom correspondence may be addressed: College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China. Tel.: 571-8820-6659; Fax: 571-8820-8569; E-mail: zhaoxiaoli@zju.edu.cn.

To whom correspondence may be addressed: Institute of Genetics, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310058, China. Tel.: 571-8820-6485; Fax: 571-8820-8569; E-mail: gminxin88@zju.edu.cn.

F. M. performed the experiments and contributed to data analysis in Figs. 2, 3, and 6⇑⇑–9.

X. C. and Z. Z. carried out the MD simulations.

Y. P. performed the aminoacylation experiment.

R. L. did the thiolation analysis.

F. L. and Q. F. contributed to the Western blotting analysis.

A. S. G. performed the statistical analysis.

N. F.-G. provided the cell lines.

M.-X. G. designed the experiments, and M.-X. G. and X. Z. monitored the project progression, data analysis, and interpretation.

F. M. prepared the initial draft of the manuscript.

M.-X. G. made the final version of the manuscript.

The MD simulations were carried out at National Supercomputer Center in Tianjin, China.

The authors declare that they have no conflicts of interest with the contents of this article.


Research Funding:

This work was supported by National Natural Science Foundation of China Grant 81330024, National Basic Research Priorities Program of China Grant 2014CB541704, NIDCD National Institutes of Health Grants RO1DC05230 and RO1DC07696 (to M.-X. G.), National Natural Science Foundation of China Grant 31400709 (to X. C.), and National Basic Research Priorities Program of China Grant 2012CB967902 (to X. Z.).

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.


  • Science & Technology
  • Life Sciences & Biomedicine
  • Biochemistry & Molecular Biology

Biochemical Evidence for a Nuclear Modifier Allele (A10S) in TRMU (Methylaminomethyl-2-thiouridylate-methyltransferase) Related to Mitochondrial tRNA Modification in the Phenotypic Manifestation of Deafness-associated 12S rRNA Mutation

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Journal Title:

Journal of Biological Chemistry


Volume 292, Number 7


, Pages 2881-2892

Type of Work:

Article | Final Publisher PDF


Nuclear modifier gene(s) was proposed to modulate the phenotypic expression of mitochondrial DNA mutation(s). Our previous investigations revealed that a nuclear modifier allele (A10S) in TRMU (methylaminomethyl-2-thiouridylate-methyltransferase) related to tRNA modification interacts with 12S rRNA 1555A3G mutation to cause deafness. The A10S mutation resided at a highly conserved residue of the N-terminal sequence. It was hypothesized that the A10S mutation altered the structure and function of TRMU, thereby causing mitochondrial dysfunction. Using molecular dynamics simulations, we showed that the A10S mutation introduced the Ser10 dynamic electrostatic interaction with the Lys106 residue of helix 4 within the catalytic domain of TRMU. The Western blotting analysis displayed the reduced levels of TRMU in mutant cells carrying the A10S mutation. The thermal shift assay revealed the Tm value of mutant TRMU protein, lower than that of the wild-type counterpart. The A10S mutation caused marked decreases in 2-thiouridine modification of U34 of tRNALys , tRNAGlu and tRNAGln . However, the A10S mutation mildly increased the aminoacylated efficiency of tRNAs. The altered 2-thiouridine modification worsened the impairment of mitochondrial translation associated with the m.1555A3 G mutation. The defective translation resulted in the reduced activities of mitochondrial respiration chains. The respiratory deficiency caused the reduction of mitochondrial ATP production and elevated the production of reactive oxidative species. As a result, mutated TRMU worsened mitochondrial dysfunctions associated with m.1555A3 G mutation, exceeding the threshold for expressing a deafness phenotype. Our findings provided new insights into the pathophysiology of maternally inherited deafness that was manifested by interaction between mtDNA mutation and nuclear modifier gene.

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