Altered 2-thiouridylation impairs mitochondrial translation in reversible infantile respiratory chain deficiency

Hum Mol Genet. 2013 Nov 15;22(22):4602-15. doi: 10.1093/hmg/ddt309. Epub 2013 Jun 28.


Childhood-onset mitochondrial encephalomyopathies are severe, relentlessly progressive conditions. However, reversible infantile respiratory chain deficiency (RIRCD), due to a homoplasmic mt-tRNA(Glu) mutation, and reversible infantile hepatopathy, due to tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase (TRMU) deficiency, stand out by showing spontaneous recovery, and provide the key to treatments of potential broader relevance. Modification of mt-tRNA(Glu) is a possible functional link between these two conditions, since TRMU is responsible for 2-thiouridylation of mt-tRNA(Glu), mt-tRNA(Lys) and mt-tRNA(Gln). Here we show that down-regulation of TRMU in RIRCD impairs 2-thiouridylation and exacerbates the effect of the mt-tRNA(Glu) mutation by triggering a mitochondrial translation defect in vitro. Skeletal muscle of RIRCD patients in the symptomatic phase showed significantly reduced 2-thiouridylation. Supplementation with l-cysteine, which is required for optimal TRMU function, rescued respiratory chain enzyme activities in human cell lines of patients with RIRCD as well as deficient TRMU. Our results show that l-cysteine supplementation is a potential treatment for RIRCD and for TRMU deficiency, and is likely to have broader application for the growing group of intra-mitochondrial translation disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cysteine / metabolism
  • Gene Expression Regulation
  • Humans
  • Mitochondria / genetics*
  • Mitochondrial Diseases / genetics*
  • Mitochondrial Diseases / metabolism
  • Mitochondrial Diseases / pathology
  • Mitochondrial Encephalomyopathies / genetics*
  • Mitochondrial Encephalomyopathies / metabolism
  • Mitochondrial Encephalomyopathies / pathology
  • Mitochondrial Proteins / genetics*
  • Mitochondrial Proteins / metabolism
  • Muscle, Skeletal / metabolism
  • Mutation
  • Myoblasts / metabolism
  • Oxidative Phosphorylation
  • Protein Biosynthesis / genetics*
  • Protein Biosynthesis / physiology
  • RNA, Transfer / genetics
  • RNA, Transfer / metabolism*
  • Thiouridine / analogs & derivatives
  • Thiouridine / metabolism
  • tRNA Methyltransferases / genetics*
  • tRNA Methyltransferases / metabolism


  • 2-thiouridine
  • Mitochondrial Proteins
  • Thiouridine
  • RNA, Transfer
  • tRNA Methyltransferases
  • TRMU protein, human
  • Cysteine