Mitochondrial translation requires folate-dependent tRNA methylation

Nature. 2018 Feb 1;554(7690):128-132. doi: 10.1038/nature25460. Epub 2018 Jan 24.


Folates enable the activation and transfer of one-carbon units for the biosynthesis of purines, thymidine and methionine. Antifolates are important immunosuppressive and anticancer agents. In proliferating lymphocytes and human cancers, mitochondrial folate enzymes are particularly strongly upregulated. This in part reflects the need for mitochondria to generate one-carbon units and export them to the cytosol for anabolic metabolism. The full range of uses of folate-bound one-carbon units in the mitochondrial compartment itself, however, has not been thoroughly explored. Here we show that loss of the catalytic activity of the mitochondrial folate enzyme serine hydroxymethyltransferase 2 (SHMT2), but not of other folate enzymes, leads to defective oxidative phosphorylation in human cells due to impaired mitochondrial translation. We find that SHMT2, presumably by generating mitochondrial 5,10-methylenetetrahydrofolate, provides methyl donors to produce the taurinomethyluridine base at the wobble position of select mitochondrial tRNAs. Mitochondrial ribosome profiling in SHMT2-knockout human cells reveals that the lack of this modified base causes defective translation, with preferential mitochondrial ribosome stalling at certain lysine (AAG) and leucine (UUG) codons. This results in the impaired expression of respiratory chain enzymes. Stalling at these specific codons also occurs in certain inborn errors of mitochondrial metabolism. Disruption of whole-cell folate metabolism, by either folate deficiency or antifolate treatment, also impairs the respiratory chain. In summary, mammalian mitochondria use folate-bound one-carbon units to methylate tRNA, and this modification is required for mitochondrial translation and thus oxidative phosphorylation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminohydrolases / metabolism
  • Biocatalysis
  • Carrier Proteins / metabolism
  • Codon / genetics
  • Electron Transport
  • Folic Acid / metabolism*
  • Folic Acid Antagonists / pharmacology
  • GTP-Binding Proteins / metabolism
  • Glycine Hydroxymethyltransferase / deficiency
  • Glycine Hydroxymethyltransferase / metabolism
  • Guanosine / metabolism
  • HCT116 Cells
  • HEK293 Cells
  • Humans
  • Leucine / genetics
  • Lysine / genetics
  • Methylation / drug effects
  • Methylenetetrahydrofolate Dehydrogenase (NADP) / metabolism
  • Mitochondria / drug effects
  • Mitochondria / enzymology
  • Mitochondria / metabolism*
  • Multifunctional Enzymes / metabolism
  • Oxidative Phosphorylation / drug effects
  • Protein Biosynthesis*
  • RNA, Transfer / chemistry*
  • RNA, Transfer / genetics
  • RNA, Transfer / metabolism*
  • RNA-Binding Proteins
  • Ribosomes / metabolism
  • Sarcosine / metabolism
  • Tetrahydrofolates / metabolism
  • Thymine Nucleotides / biosynthesis


  • Carrier Proteins
  • Codon
  • Folic Acid Antagonists
  • MTHFD2 protein, human
  • MTO1 protein, human
  • Multifunctional Enzymes
  • RNA-Binding Proteins
  • Tetrahydrofolates
  • Thymine Nucleotides
  • Guanosine
  • 5,6,7,8-tetrahydrofolic acid
  • RNA, Transfer
  • Folic Acid
  • Methylenetetrahydrofolate Dehydrogenase (NADP)
  • Glycine Hydroxymethyltransferase
  • SHMT protein, human
  • Aminohydrolases
  • GTP-Binding Proteins
  • GTPBP3 protein, human
  • Leucine
  • Lysine
  • thymidine 5'-triphosphate
  • Sarcosine