Mitochondrial translation requires folate-dependent tRNA methylation. Author Raphael Morscher, Gregory Ducker, Sophia Li, Johannes Mayer, Zemer Gitai, Wolfgang Sperl, Joshua Rabinowitz Publication Year 2018 Type Journal Article Abstract 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. Keywords Protein Biosynthesis, RNA-Binding Proteins, Humans, Leucine, Carrier Proteins, HEK293 Cells, Methylation, Biocatalysis, Ribosomes, Mitochondria, Folic Acid, Lysine, Guanosine, Codon, Electron Transport, HCT116 Cells, Oxidative Phosphorylation, Glycine Hydroxymethyltransferase, Methylenetetrahydrofolate Dehydrogenase (NADP), RNA, Transfer, Folic Acid Antagonists, Tetrahydrofolates, Aminohydrolases, GTP-Binding Proteins, Multifunctional Enzymes, Sarcosine, Thymine Nucleotides Journal Nature Volume 554 Issue 7690 Pages 128-132 Date Published 2018 Feb 01 ISSN Number 1476-4687 DOI 10.1038/nature25460 Alternate Journal Nature PMCID PMC6020024 PMID 29364879 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML