{"gene":"MTO1","run_date":"2026-06-10T05:19:51","timeline":{"discoveries":[{"year":1998,"finding":"Yeast Mto1p and Mss1p form a heterodimer complex in mitochondria; in a paromomycin-resistant background, the Mto1p·Mss1p complex is required for processing the COX1 mitochondrial transcript and for synthesis of cytochrome oxidase subunit 1. The complex is proposed to optimize mitochondrial protein synthesis, possibly by a proofreading mechanism.","method":"In vivo pulse-labeling, respiratory phenotype analysis, visible absorption spectroscopy, respiratory enzyme activity assays, genetic interaction with paromomycin-resistance allele","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic and biochemical evidence (heterodimer co-evidence, pulse-labeling, enzyme assays) replicated across multiple mutant backgrounds in a focused mechanistic study","pmids":["9774408"],"is_preprint":false},{"year":2002,"finding":"Human MTO1 encodes a mitochondrially targeted protein that is a structural and functional homolog of yeast Mto1; human MTO1 cDNA complements the respiratory-deficient phenotype of yeast mto1 cells carrying the paromomycin-resistance (PR) 15S rRNA mutation, establishing functional conservation in mitochondrial tRNA modification.","method":"Yeast complementation assay, cDNA cloning, subcellular localization inference from sequence analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional complementation in yeast plus sequence conservation, single lab","pmids":["12011058"],"is_preprint":false},{"year":2003,"finding":"Mouse Mto1 localizes to mitochondria and functionally complements yeast mto1 respiratory-deficient cells carrying the PR rRNA mutation, confirming its conserved role in mitochondrial tRNA modification.","method":"Subcellular fractionation/localization, yeast complementation assay","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment plus functional complementation, single lab","pmids":["14522080"],"is_preprint":false},{"year":2009,"finding":"Deletion of yeast MTO1 decreases steady-state levels of multiple mitochondrial tRNAs (tRNALys, tRNAGlu, tRNAGln, tRNALeu, tRNAGly, tRNAArg, tRNAPhe), reduces aminoacylation of tRNALys, tRNALeu, and tRNAArg, and decreases steady-state levels of mitochondrial mRNAs (COX1, COX2, COX3, ATP6, ATP9), demonstrating that MTO1-dependent tRNA modification is required for mitochondrial tRNA and mRNA stability and tRNA charging.","method":"Northern blot (steady-state tRNA and mRNA levels), aminoacylation assay, genetic interaction analysis with 15S rRNA C1409G mutation","journal":"Mitochondrion","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical assays (Northern blot, aminoacylation) in a focused loss-of-function study with rigorous genetic controls","pmids":["19460296"],"is_preprint":false},{"year":2012,"finding":"Human MTO1 catalyzes 5-carboxymethylaminomethylation (cmnm5) of the wobble uridine base in three mitochondrial tRNAs; pathogenic MTO1 mutations in patients cause variably combined reduction in mtDNA-dependent respiratory chain activities in muscle and fibroblasts, and wild-type MTO1 cDNA corrects the respiratory defect in mutant cells. Equivalent yeast mutations phenocopy the patient respiratory deficiency and impair in vivo mtDNA translation.","method":"Patient cell respiratory chain enzyme assays, wild-type MTO1 rescue (lentiviral cDNA expression), yeast mto1 mutant complementation, in vivo mtDNA translation (pulse-labeling), exome sequencing to identify mutations","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — enzymatic activity established by rescue and yeast modeling, multiple orthogonal methods (enzyme assays, rescue, pulse-labeling), replicated across patient cohorts and yeast models","pmids":["22608499"],"is_preprint":false},{"year":2013,"finding":"Novel missense MTO1 mutations cause combined mitochondrial respiratory chain (MRC) deficiency with impaired mitochondrial protein synthesis; pathogenic role validated in recombinant yeast by oxidative growth, respiratory activity, mitochondrial protein synthesis, and complex IV activity assays. Wild-type MTO1 expression rescues the respiratory defect in patient fibroblasts.","method":"Yeast recombinant model (oxidative growth, respiratory activity, complex IV assay, mitochondrial protein synthesis), patient fibroblast rescue with wt MTO1, exome sequencing","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal functional assays in both yeast and human cells, multiple independent patient families","pmids":["23929671"],"is_preprint":false},{"year":2008,"finding":"In fission yeast S. pombe, Mto1 contains a conserved CM1 region (short N-terminal motif) required for cytoplasmic microtubule nucleation and interaction with the γ-tubulin complex (γ-TuC); CM1 mutations abolish γ-TuC binding and microtubule nucleation without affecting Mto1 localization or Mto2 binding. A separate non-CM1 region is required for Mto2 binding and also contributes to γ-TuC association. Mto1 and Mto2 form a complex (Mto1/2) independent of γ-TuC, and each can weakly associate with γ-TuC in the absence of the other.","method":"In vivo mutagenesis, co-immunoprecipitation, live-cell imaging/localization, microtubule nucleation assays (fission yeast genetics)","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal domain mutagenesis with multiple orthogonal readouts (Co-IP, localization, nucleation phenotype) in a rigorous single study","pmids":["19001497"],"is_preprint":false},{"year":2010,"finding":"Fission yeast Mto1 contains a conserved C-terminal MASC sequence required for targeting to multiple distinct MTOCs; different MASC subregions target Mto1 to different MTOCs. Mto1 targeting to the cell equator during division requires direct interaction with unconventional type II myosin Myp2. Targeting to the spindle pole body during mitosis depends on SIN components Sid4 and Cdc11.","method":"In vivo mutagenesis, live-cell imaging, co-immunoprecipitation (Mto1-Myp2 interaction), genetic dependency analysis (SIN pathway)","journal":"Current biology : CB","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, live imaging, Co-IP, genetics) establishing direct protein-protein interaction and MTOC targeting mechanisms","pmids":["20970338"],"is_preprint":false},{"year":2014,"finding":"MTO1-deficient mice (generated by gene trap mutagenesis) develop hypertrophic cardiomyopathy and complex I deficiency with mitochondrial dysfunction in cardiac tissue, mirroring the human disease phenotype.","method":"Gene trap mouse model, cardiac morphology, respiratory chain enzyme activity assays (complex I), mitochondrial functional analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cardiac and biochemical phenotype, single lab","pmids":["25506927"],"is_preprint":false},{"year":2018,"finding":"MTO1 deficiency in human fibroblasts activates HIF-1, downregulates PPARγ and UCP2, and inactivates AMPK, uncoupling glycolysis from oxidative phosphorylation and causing lipid droplet accumulation; this metabolic reprogramming through the HIF-PPARγ-UCP2-AMPK axis is distinct from that triggered by GTPBP3 deficiency (which activates AMPK and increases UCP2/PPARγ).","method":"Patient fibroblast analysis, siRNA-mediated MTO1 silencing, Western blot and activity assays for HIF-1, AMPK, PPARγ, UCP2, fatty acid oxidation assays, lipid droplet staining","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — patient cells plus siRNA knockdown with multiple pathway readouts, single lab","pmids":["29348686"],"is_preprint":false},{"year":2021,"finding":"Mto1 deficiency in zebrafish (CRISPR/Cas9 knockout) causes: (1) perturbed tRNA structure and reduced stability of tRNAGln, tRNALys, tRNATrp, tRNALeu(UUR); (2) global decrease in aminoacylation of mitochondrial tRNAs with taurine modification; (3) altered polyadenylation of cox1, cox3, and nd1 mRNAs via decreased expression of MTPAP; (4) MTO1 physically interacts with MTPAP (poly(A) polymerase) as shown by immunoprecipitation; (5) impaired mitochondrial translation and reduced OXPHOS complex activities; and (6) heart development defects and hypertrophic cardiomyopathy.","method":"CRISPR/Cas9 knockout zebrafish, tRNA structural analysis (S1 nuclease digestion), aminoacylation assays, mRNA polyadenylation analysis, co-immunoprecipitation (MTO1-MTPAP), OXPHOS complex activity assays, cardiac histology","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical methods in a clean KO model, novel interaction (MTO1-MTPAP) confirmed by Co-IP, multiple cellular phenotypes consistently supporting the mechanism","pmids":["33836087"],"is_preprint":false},{"year":2015,"finding":"Deletion of MTO1 in yeast carrying the mitochondrial 15S rRNA C1477G mutation (equivalent to human A1555G) suppresses aminoglycoside sensitivity and partially compensates for the energy deficit by upregulating key glycolytic genes (HXK2, PFK1, PYK1), indicating MTO1 acts as a modifier of the neomycin-sensitive phenotype through regulation of mitochondrial tRNA modification and compensatory glycolysis.","method":"Yeast genetics (null mutation analysis), growth assays under aminoglycoside treatment, RT-PCR for glycolytic gene expression, mitochondrial function assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with phenotypic and gene expression readouts, single lab","pmids":["25898254"],"is_preprint":false},{"year":2017,"finding":"Expression of MTO1 (along with TRMU and GTPBP3) is regulated by specific miRNAs induced by mitochondria-to-nucleus retrograde signals (ROS and Ca2+) in cybrid models of mtDNA diseases; transfection of mutant cybrids with miRNA antagonists improves cell energetic state, demonstrating that miRNA-mediated modulation of MTO1 expression affects mitochondrial tRNA modification status and OXPHOS function.","method":"Cybrid cell models, miRNA overexpression/antagonist transfection, OXPHOS activity assays, ROS/Ca2+ pathway analysis","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional intervention (miRNA antagonists) with OXPHOS readout in multiple cybrid models, single lab","pmids":["28740091"],"is_preprint":false},{"year":2019,"finding":"In fission yeast, Mto1 and Alp7 interdependently localize to the nuclear envelope (NE) in cells without microtubules; Alp14 localizes to the NE in an Alp7- and Mto1-dependent manner. Artificial tethering of Mto1 to the NE in alp7-deleted cells partially restores microtubule generation from the NE, demonstrating that Mto1 recruitment to the NE is a limiting step for NE-based microtubule nucleation.","method":"Live-cell fluorescence microscopy, microtubule repolymerization assay, artificial NE-tethering experiment, genetic deletion analysis","journal":"Journal of molecular cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional tethering rescue, single lab","pmids":["31087092"],"is_preprint":false},{"year":2019,"finding":"In fission yeast, loss of Mto1 leads to defects in DNA repair, reduced homologous recombination efficiency, abnormal DNA repair factory dynamics, impaired sister chromatid pairing, and reduced Rad21 cohesin binding along chromosomal arms; this links cytoplasmic microtubule nucleation by Mto1 to chromosomal organization, cohesion, and DNA repair during interphase.","method":"Genetic deletion (mto1Δ), DNA repair assays, live-cell imaging of repair foci, ChIP for Rad21 cohesin","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean deletion with multiple cellular phenotype readouts (repair assays, imaging, ChIP), single lab","pmids":["31483748"],"is_preprint":false},{"year":2020,"finding":"In fission yeast, Mto1 (together with Mto2 and γ-tubulin) regulates astral microtubule nucleation at the spindle pole body; deletion of Mto1 reduces astral microtubule number, elevates Rho1-GTP at the division site, and, in combination with a bgs1 mutation, causes defective cytokinetic furrow ingression.","method":"Genetic deletion analysis, live-cell imaging of microtubules and division site, Rho1-GTP assay, double-mutant epistasis","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean deletion with imaging and biochemical readouts, epistasis with bgs1 mutation, single lab","pmids":["32520628"],"is_preprint":false},{"year":2026,"finding":"The ER transmembrane protein Erg28 physically interacts with both the Mto1-Mto2 complex and the γ-tubulin small complex (γ-TuSC), significantly attenuating γ-TuSC binding to the Mto1-Mto2 complex; Erg28 inhibits Mto1-Mto2/γ-TuSC-mediated microtubule assembly in vitro; the cytosolic N-terminal region of Erg28 is required for this inhibitory activity; erg28 deletion causes excessive microtubule assembly and nuclear shape deformation.","method":"Co-immunoprecipitation (Erg28-Mto1/Mto2, Erg28-γ-TuSC), in vitro microtubule assembly assay, domain deletion mutagenesis, live-cell microscopy","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — biochemical reconstitution (in vitro assembly assay) plus Co-IP and mutagenesis, multiple orthogonal methods, single lab","pmids":["41989917"],"is_preprint":false}],"current_model":"Human MTO1 encodes a mitochondrially localized enzyme that catalyzes 5-carboxymethylaminomethylation (cmnm5/τm5) of the wobble uridine in at least five mitochondrial tRNAs (tRNAGlu, tRNAGln, tRNALys, tRNATrp, tRNALeu(UUR)), acting in a complex with MSS1/GTPBP3; this modification is required for tRNA structural stability, aminoacylation, and mitochondrial mRNA stability (including polyadenylation via interaction with MTPAP), collectively ensuring efficient and accurate mitochondrial translation, and deficiency causes combined OXPHOS deficiency, hypertrophic cardiomyopathy, and lactic acidosis; separately, the S. pombe ortholog Mto1 (CDK5RAP2-related) functions as a cytoplasmic microtubule nucleation factor that recruits the γ-tubulin complex to noncentrosomal MTOCs via its CM1 and MASC domains within the Mto1-Mto2 complex, and is in turn negatively regulated by the ER protein Erg28."},"narrative":{"mechanistic_narrative":"MTO1 encodes a mitochondrially targeted enzyme that catalyzes 5-carboxymethylaminomethylation (cmnm5/τm5) of the wobble uridine in mitochondrial tRNAs, a modification required for accurate and efficient mitochondrial translation [PMID:22608499]. The human protein is a structural and functional homolog of yeast Mto1, complementing the respiratory-deficient phenotype of yeast mto1 mutants and confirming evolutionary conservation of its tRNA-modifying role [PMID:12011058, PMID:14522080]. Mechanistically, this wobble-uridine modification is required for the structural integrity, steady-state stability, and aminoacylation of multiple mitochondrial tRNAs (tRNAGlu, tRNAGln, tRNALys, tRNATrp, tRNALeu(UUR)), and its loss destabilizes mitochondrial mRNAs and impairs synthesis of OXPHOS subunits [PMID:19460296, PMID:33836087]. MTO1 acts within a heterodimeric complex with MSS1/GTPBP3 to optimize mitochondrial protein synthesis [PMID:9774408], and physically interacts with the mitochondrial poly(A) polymerase MTPAP, coupling tRNA modification to mRNA polyadenylation [PMID:33836087]. Loss of function causes combined respiratory-chain deficiency, impaired mitochondrial translation, and hypertrophic cardiomyopathy with complex I deficiency in patients and animal models [PMID:22608499, PMID:23929671, PMID:25506927, PMID:33836087]. Separately, the S. pombe ortholog Mto1 functions as a cytoplasmic microtubule nucleation factor that recruits the γ-tubulin complex to noncentrosomal MTOCs through its CM1 and MASC domains within an Mto1-Mto2 complex, and is negatively regulated by the ER protein Erg28 [PMID:19001497, PMID:20970338, PMID:41989917].","teleology":[{"year":1998,"claim":"Established that Mto1 acts in concert with Mss1 in mitochondria to optimize mitochondrial protein synthesis, defining the founding biochemical partnership before its enzymatic role was known.","evidence":"Yeast pulse-labeling, respiratory enzyme assays, and genetic interaction with a paromomycin-resistance allele showing the Mto1·Mss1 heterodimer is required for COX1 processing and cytochrome oxidase synthesis","pmids":["9774408"],"confidence":"High","gaps":["Did not identify the chemical modification catalyzed","Did not define which tRNAs are substrates"]},{"year":2002,"claim":"Showed human MTO1 is a functional ortholog by complementing yeast mto1 respiratory defects, extending the conserved mitochondrial role to humans.","evidence":"Yeast complementation with human MTO1 cDNA and sequence-based mitochondrial targeting inference","pmids":["12011058"],"confidence":"Medium","gaps":["Mitochondrial localization inferred from sequence rather than directly demonstrated","Enzymatic activity not assayed directly"]},{"year":2003,"claim":"Confirmed conserved mitochondrial localization and function of the mammalian ortholog in mouse, reinforcing the cross-species tRNA-modification model.","evidence":"Subcellular fractionation of mouse Mto1 plus yeast complementation","pmids":["14522080"],"confidence":"Medium","gaps":["Single-lab localization","No direct biochemical demonstration of modification activity"]},{"year":2009,"claim":"Defined the downstream consequences of MTO1 loss by showing tRNA modification is required for tRNA stability, aminoacylation, and mitochondrial mRNA stability, connecting modification to translational competence.","evidence":"Yeast MTO1 deletion analyzed by Northern blot of tRNA/mRNA levels and aminoacylation assays with genetic controls","pmids":["19460296"],"confidence":"High","gaps":["Did not identify the precise chemical modification in human tRNAs","Mechanism linking modification loss to mRNA destabilization not resolved"]},{"year":2012,"claim":"Identified the specific catalytic activity (cmnm5 wobble-uridine modification) and established MTO1 as a human disease gene through patient mutations and rescue, the central mechanistic and clinical advance.","evidence":"Patient respiratory chain assays, lentiviral wild-type MTO1 rescue, yeast modeling, in vivo mtDNA pulse-labeling, and exome sequencing","pmids":["22608499"],"confidence":"High","gaps":["Initially defined modification on three tRNAs","Structural basis of catalysis not resolved"]},{"year":2013,"claim":"Extended the disease-gene model with additional pathogenic missense mutations validated functionally, solidifying genotype-to-phenotype causality for combined respiratory deficiency.","evidence":"Recombinant yeast functional assays (growth, respiration, complex IV, mitochondrial protein synthesis) and patient fibroblast rescue with wild-type MTO1","pmids":["23929671"],"confidence":"High","gaps":["Tissue-specificity of phenotype unexplained","Genotype-phenotype correlation across mutations incomplete"]},{"year":2014,"claim":"Demonstrated in vivo that MTO1 loss produces hypertrophic cardiomyopathy and complex I deficiency in mammals, establishing a faithful disease model.","evidence":"Gene-trap MTO1 mouse with cardiac morphology and respiratory chain enzyme assays","pmids":["25506927"],"confidence":"Medium","gaps":["Single-lab model","Molecular reason for cardiac selectivity not addressed"]},{"year":2017,"claim":"Revealed that MTO1 expression is itself regulated by retrograde-signal-induced miRNAs, placing tRNA modification under mitochondria-to-nucleus feedback control.","evidence":"Cybrid models with miRNA overexpression/antagonist transfection and OXPHOS activity readouts","pmids":["28740091"],"confidence":"Medium","gaps":["Direct miRNA-MTO1 transcript targeting not fully mapped","Single-lab cybrid system"]},{"year":2018,"claim":"Mapped the metabolic reprogramming downstream of MTO1 deficiency, distinguishing its HIF-PPARγ-UCP2-AMPK signature from that of GTPBP3 deficiency.","evidence":"Patient fibroblasts and siRNA knockdown with Western/activity assays for HIF-1, AMPK, PPARγ, UCP2 plus lipid droplet staining","pmids":["29348686"],"confidence":"Medium","gaps":["Causal ordering within the signaling axis not established","Single-lab observation"]},{"year":2021,"claim":"Integrated the full mitochondrial mechanism in vivo by linking MTO1 to tRNA structure/aminoacylation, OXPHOS, cardiomyopathy, and a novel physical interaction with the poly(A) polymerase MTPAP coupling modification to mRNA polyadenylation.","evidence":"CRISPR/Cas9 zebrafish knockout with tRNA structural analysis, aminoacylation, polyadenylation assays, MTO1-MTPAP Co-IP, OXPHOS assays, and cardiac histology","pmids":["33836087"],"confidence":"High","gaps":["MTO1-MTPAP interaction shown by Co-IP without reciprocal/structural validation","Mechanism by which MTO1 controls MTPAP expression unresolved"]},{"year":2010,"claim":"For the S. pombe ortholog, defined CM1 as the γ-tubulin-complex-binding/nucleation motif and MASC as the MTOC-targeting region, separating the nucleation and localization functions of cytoplasmic Mto1.","evidence":"In vivo domain mutagenesis, Co-IP, live imaging, microtubule nucleation assays, and genetic dependency analysis (Myp2, SIN components)","pmids":["19001497","20970338"],"confidence":"High","gaps":["Relationship between fission-yeast cytoplasmic role and the conserved mitochondrial enzyme function unresolved","Structural basis of CM1-γ-TuC binding not determined"]},{"year":2020,"claim":"Broadened the cytoplasmic Mto1 roles to NE-based and astral microtubule nucleation and to interphase chromosome organization, cohesion, and DNA repair, showing nucleation activity has downstream chromosomal consequences.","evidence":"Fission yeast deletions with live-cell imaging, microtubule repolymerization, NE-tethering rescue, Rho1-GTP assays, DNA repair assays, and Rad21 ChIP","pmids":["31087092","31483748","32520628"],"confidence":"Medium","gaps":["Single-lab observations","Direct mechanistic link between microtubule nucleation and cohesin loading not established"]},{"year":2026,"claim":"Identified Erg28 as a negative regulator that competes with γ-TuSC for the Mto1-Mto2 complex, defining a brake on noncentrosomal microtubule assembly.","evidence":"Co-IP (Erg28-Mto1/Mto2 and Erg28-γ-TuSC), in vitro microtubule assembly reconstitution, domain deletion mutagenesis, and live-cell microscopy","pmids":["41989917"],"confidence":"High","gaps":["Whether an analogous regulator exists for mammalian MTO1 unknown","Structural basis of competitive binding not resolved"]},{"year":null,"claim":"It remains unresolved how the same gene symbol reconciles a conserved mitochondrial tRNA-modifying enzyme with the fission-yeast cytoplasmic microtubule nucleator, and whether these reflect orthologous functions or distinct proteins.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experiment in the corpus bridges the mitochondrial enzymatic and cytoplasmic nucleation activities","Structural model of human MTO1 catalysis absent","Mechanism of cardiac-selective pathology unexplained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[4,3,10]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[4]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[3,10]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[6,7]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,2,4]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[6,7,15]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[13]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[3,4,10]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,4,5]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,5,8]}],"complexes":["MTO1-MSS1/GTPBP3 complex","Mto1-Mto2 complex"],"partners":["GTPBP3","MTPAP","MTO2","MYP2","ERG28"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y2Z2","full_name":"5-taurinomethyluridine-[tRNA] synthase subunit MTO1, mitochondrial","aliases":["Mitochondrial tRNA translation optimization 1","Protein MTO1 homolog, mitochondrial"],"length_aa":717,"mass_kda":80.0,"function":"Component of the GTPBP3-MTO1 complex that catalyzes the 5-taurinomethyluridine (taum(5)U) modification at the 34th wobble position (U34) of mitochondrial tRNAs (mt-tRNAs), which plays a role in mt-tRNA decoding and mitochondrial translation (PubMed:29390138, PubMed:33619562). Taum(5)U formation on mammalian mt-tRNA requires the presence of both GTPBP3-mediated GTPase activity and MTO1 catalytic activity (PubMed:29390138)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q9Y2Z2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MTO1","classification":"Not Classified","n_dependent_lines":94,"n_total_lines":1208,"dependency_fraction":0.07781456953642384},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"FKBP5","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MTO1","total_profiled":1310},"omim":[{"mim_id":"614702","title":"COMBINED OXIDATIVE PHOSPHORYLATION DEFICIENCY 10; COXPD10","url":"https://www.omim.org/entry/614702"},{"mim_id":"614667","title":"MITOCHONDRIAL tRNA TRANSLATION OPTIMIZATION 1; MTO1","url":"https://www.omim.org/entry/614667"},{"mim_id":"609060","title":"COMBINED OXIDATIVE PHOSPHORYLATION DEFICIENCY 1; COXPD1","url":"https://www.omim.org/entry/609060"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MTO1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9Y2Z2","domains":[{"cath_id":"3.50.50.60","chopping":"37-239_405-519","consensus_level":"medium","plddt":94.1942,"start":37,"end":519},{"cath_id":"2.40.30.260","chopping":"243-375","consensus_level":"medium","plddt":89.2565,"start":243,"end":375},{"cath_id":"1.10.10.1800","chopping":"524-620","consensus_level":"high","plddt":93.0308,"start":524,"end":620},{"cath_id":"1.10.150.570","chopping":"652-715","consensus_level":"high","plddt":77.5823,"start":652,"end":715}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2Z2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2Z2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2Z2-F1-predicted_aligned_error_v6.png","plddt_mean":86.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MTO1","jax_strain_url":"https://www.jax.org/strain/search?query=MTO1"},"sequence":{"accession":"Q9Y2Z2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y2Z2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y2Z2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2Z2"}},"corpus_meta":[{"pmid":"22608499","id":"PMC_22608499","title":"Mutations of the mitochondrial-tRNA modifier MTO1 cause hypertrophic cardiomyopathy and lactic acidosis.","date":"2012","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22608499","citation_count":153,"is_preprint":false},{"pmid":"12011058","id":"PMC_12011058","title":"Isolation and characterization of the putative nuclear modifier gene MTO1 involved in the pathogenesis of deafness-associated mitochondrial 12 S rRNA A1555G mutation.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12011058","citation_count":131,"is_preprint":false},{"pmid":"30015883","id":"PMC_30015883","title":"Circular RNA‑MTO1 suppresses breast cancer cell viability and reverses monastrol resistance through regulating the TRAF4/Eg5 axis.","date":"2018","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/30015883","citation_count":113,"is_preprint":false},{"pmid":"9774408","id":"PMC_9774408","title":"MTO1 codes for a mitochondrial protein required for respiration in paromomycin-resistant mutants of Saccharomyces cerevisiae.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9774408","citation_count":80,"is_preprint":false},{"pmid":"23929671","id":"PMC_23929671","title":"MTO1 mutations are associated with hypertrophic cardiomyopathy and lactic acidosis and cause respiratory chain deficiency in humans and yeast.","date":"2013","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/23929671","citation_count":69,"is_preprint":false},{"pmid":"15542390","id":"PMC_15542390","title":"Phenotype of non-syndromic deafness associated with the mitochondrial A1555G mutation is modulated by mitochondrial RNA modifying enzymes MTO1 and GTPBP3.","date":"2004","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/15542390","citation_count":58,"is_preprint":false},{"pmid":"19001497","id":"PMC_19001497","title":"Two distinct regions of Mto1 are required for normal microtubule nucleation and efficient association with the gamma-tubulin complex in vivo.","date":"2008","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/19001497","citation_count":49,"is_preprint":false},{"pmid":"20970338","id":"PMC_20970338","title":"Fission yeast Mto1 regulates diversity of cytoplasmic microtubule organizing centers.","date":"2010","source":"Current biology : CB","url":"https://pubmed.ncbi.nlm.nih.gov/20970338","citation_count":48,"is_preprint":false},{"pmid":"30975029","id":"PMC_30975029","title":"A regulatory circuit of circ-MTO1/miR-17/QKI-5 inhibits the proliferation of lung adenocarcinoma.","date":"2019","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/30975029","citation_count":46,"is_preprint":false},{"pmid":"29331171","id":"PMC_29331171","title":"The genotypic and phenotypic spectrum of MTO1 deficiency.","date":"2017","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/29331171","citation_count":28,"is_preprint":false},{"pmid":"32194149","id":"PMC_32194149","title":"Circular RNA MTO1 suppresses tumorigenesis of gastric carcinoma by sponging miR-3200-5p and targeting PEBP1.","date":"2020","source":"Molecular and cellular probes","url":"https://pubmed.ncbi.nlm.nih.gov/32194149","citation_count":27,"is_preprint":false},{"pmid":"33836087","id":"PMC_33836087","title":"Ablation of Mto1 in zebrafish exhibited hypertrophic cardiomyopathy manifested by mitochondrion RNA maturation deficiency.","date":"2021","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/33836087","citation_count":26,"is_preprint":false},{"pmid":"29348686","id":"PMC_29348686","title":"Defects in the mitochondrial-tRNA modification enzymes MTO1 and GTPBP3 promote different metabolic reprogramming through a HIF-PPARγ-UCP2-AMPK axis.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/29348686","citation_count":26,"is_preprint":false},{"pmid":"25506927","id":"PMC_25506927","title":"MTO1-deficient mouse model mirrors the human phenotype showing complex I defect and cardiomyopathy.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25506927","citation_count":25,"is_preprint":false},{"pmid":"32731816","id":"PMC_32731816","title":"Circular RNA MTO1 Inhibits the Proliferation and Invasion of Ovarian Cancer Cells Through the miR-182-5p/KLF15 Axis.","date":"2020","source":"Cell transplantation","url":"https://pubmed.ncbi.nlm.nih.gov/32731816","citation_count":25,"is_preprint":false},{"pmid":"33089757","id":"PMC_33089757","title":"Circular RNA MTO1 inhibits gastric cancer progression by elevating PAWR via sponging miR-199a-3p.","date":"2020","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/33089757","citation_count":23,"is_preprint":false},{"pmid":"26061759","id":"PMC_26061759","title":"Optic neuropathy, cardiomyopathy, cognitive disability in patients with a homozygous mutation in the nuclear MTO1 and a mitochondrial MT-TF variant.","date":"2015","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/26061759","citation_count":23,"is_preprint":false},{"pmid":"19460296","id":"PMC_19460296","title":"Mutation in MTO1 involved in tRNA modification impairs mitochondrial RNA metabolism in the yeast Saccharomyces cerevisiae.","date":"2009","source":"Mitochondrion","url":"https://pubmed.ncbi.nlm.nih.gov/19460296","citation_count":18,"is_preprint":false},{"pmid":"14522080","id":"PMC_14522080","title":"Identification and characterization of mouse MTO1 gene related to mitochondrial tRNA modification.","date":"2003","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/14522080","citation_count":17,"is_preprint":false},{"pmid":"24160266","id":"PMC_24160266","title":"Nuclear-encoded mitochondrial MTO1 and MRPL41 are regulated in an opposite epigenetic mode based on estrogen receptor status in breast cancer.","date":"2013","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/24160266","citation_count":15,"is_preprint":false},{"pmid":"28740091","id":"PMC_28740091","title":"microRNA-mediated differential expression of TRMU, GTPBP3 and MTO1 in cell models of mitochondrial-DNA diseases.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28740091","citation_count":9,"is_preprint":false},{"pmid":"27256614","id":"PMC_27256614","title":"The homozygous R504C mutation in MTO1 gene is responsible for ONCE syndrome.","date":"2016","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27256614","citation_count":9,"is_preprint":false},{"pmid":"31087092","id":"PMC_31087092","title":"Alp7-Mto1 and Alp14 synergize to promote interphase microtubule regrowth from the nuclear envelope.","date":"2019","source":"Journal of molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/31087092","citation_count":8,"is_preprint":false},{"pmid":"32520628","id":"PMC_32520628","title":"Microtubule nucleation promoters Mto1 and Mto2 regulate cytokinesis in fission yeast.","date":"2020","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/32520628","citation_count":7,"is_preprint":false},{"pmid":"34990597","id":"PMC_34990597","title":"Clinical and genetic analysis of combined oxidative phosphorylation defificiency-10 caused by MTO1 mutation.","date":"2022","source":"Clinica chimica acta; international journal of clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34990597","citation_count":6,"is_preprint":false},{"pmid":"31483748","id":"PMC_31483748","title":"Effects of the microtubule nucleator Mto1 on chromosomal movement, DNA repair, and sister chromatid cohesion in fission yeast.","date":"2019","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/31483748","citation_count":5,"is_preprint":false},{"pmid":"25898254","id":"PMC_25898254","title":"MTO1 worked as a modifier in the aminoglycosides sensitivity of yeast carrying a mitochondrial 15S rRNA C1477G mutation.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25898254","citation_count":4,"is_preprint":false},{"pmid":"34547275","id":"PMC_34547275","title":"A novel compound heterozygous mutation of the MTO1 gene associated with complex oxidative phosphorylation deficiency type 10.","date":"2021","source":"Clinica chimica acta; international journal of clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34547275","citation_count":1,"is_preprint":false},{"pmid":"40694227","id":"PMC_40694227","title":"Circular RNAs MTO1 and ZNF292 as potential diagnostic biomarkers in HIV patients treated with antiretroviral therapy.","date":"2025","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/40694227","citation_count":0,"is_preprint":false},{"pmid":"41989917","id":"PMC_41989917","title":"The endoplasmic reticulum protein Erg28 restrains Mto1-Mto2-γ-TuSC-mediated microtubule assembly.","date":"2026","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/41989917","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16554,"output_tokens":4813,"usd":0.060928,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13047,"output_tokens":4447,"usd":0.088205,"stage2_stop_reason":"end_turn"},"total_usd":0.149133,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"Yeast Mto1p and Mss1p form a heterodimer complex in mitochondria; in a paromomycin-resistant background, the Mto1p·Mss1p complex is required for processing the COX1 mitochondrial transcript and for synthesis of cytochrome oxidase subunit 1. The complex is proposed to optimize mitochondrial protein synthesis, possibly by a proofreading mechanism.\",\n      \"method\": \"In vivo pulse-labeling, respiratory phenotype analysis, visible absorption spectroscopy, respiratory enzyme activity assays, genetic interaction with paromomycin-resistance allele\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic and biochemical evidence (heterodimer co-evidence, pulse-labeling, enzyme assays) replicated across multiple mutant backgrounds in a focused mechanistic study\",\n      \"pmids\": [\"9774408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Human MTO1 encodes a mitochondrially targeted protein that is a structural and functional homolog of yeast Mto1; human MTO1 cDNA complements the respiratory-deficient phenotype of yeast mto1 cells carrying the paromomycin-resistance (PR) 15S rRNA mutation, establishing functional conservation in mitochondrial tRNA modification.\",\n      \"method\": \"Yeast complementation assay, cDNA cloning, subcellular localization inference from sequence analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional complementation in yeast plus sequence conservation, single lab\",\n      \"pmids\": [\"12011058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mouse Mto1 localizes to mitochondria and functionally complements yeast mto1 respiratory-deficient cells carrying the PR rRNA mutation, confirming its conserved role in mitochondrial tRNA modification.\",\n      \"method\": \"Subcellular fractionation/localization, yeast complementation assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment plus functional complementation, single lab\",\n      \"pmids\": [\"14522080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Deletion of yeast MTO1 decreases steady-state levels of multiple mitochondrial tRNAs (tRNALys, tRNAGlu, tRNAGln, tRNALeu, tRNAGly, tRNAArg, tRNAPhe), reduces aminoacylation of tRNALys, tRNALeu, and tRNAArg, and decreases steady-state levels of mitochondrial mRNAs (COX1, COX2, COX3, ATP6, ATP9), demonstrating that MTO1-dependent tRNA modification is required for mitochondrial tRNA and mRNA stability and tRNA charging.\",\n      \"method\": \"Northern blot (steady-state tRNA and mRNA levels), aminoacylation assay, genetic interaction analysis with 15S rRNA C1409G mutation\",\n      \"journal\": \"Mitochondrion\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical assays (Northern blot, aminoacylation) in a focused loss-of-function study with rigorous genetic controls\",\n      \"pmids\": [\"19460296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Human MTO1 catalyzes 5-carboxymethylaminomethylation (cmnm5) of the wobble uridine base in three mitochondrial tRNAs; pathogenic MTO1 mutations in patients cause variably combined reduction in mtDNA-dependent respiratory chain activities in muscle and fibroblasts, and wild-type MTO1 cDNA corrects the respiratory defect in mutant cells. Equivalent yeast mutations phenocopy the patient respiratory deficiency and impair in vivo mtDNA translation.\",\n      \"method\": \"Patient cell respiratory chain enzyme assays, wild-type MTO1 rescue (lentiviral cDNA expression), yeast mto1 mutant complementation, in vivo mtDNA translation (pulse-labeling), exome sequencing to identify mutations\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — enzymatic activity established by rescue and yeast modeling, multiple orthogonal methods (enzyme assays, rescue, pulse-labeling), replicated across patient cohorts and yeast models\",\n      \"pmids\": [\"22608499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Novel missense MTO1 mutations cause combined mitochondrial respiratory chain (MRC) deficiency with impaired mitochondrial protein synthesis; pathogenic role validated in recombinant yeast by oxidative growth, respiratory activity, mitochondrial protein synthesis, and complex IV activity assays. Wild-type MTO1 expression rescues the respiratory defect in patient fibroblasts.\",\n      \"method\": \"Yeast recombinant model (oxidative growth, respiratory activity, complex IV assay, mitochondrial protein synthesis), patient fibroblast rescue with wt MTO1, exome sequencing\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal functional assays in both yeast and human cells, multiple independent patient families\",\n      \"pmids\": [\"23929671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In fission yeast S. pombe, Mto1 contains a conserved CM1 region (short N-terminal motif) required for cytoplasmic microtubule nucleation and interaction with the γ-tubulin complex (γ-TuC); CM1 mutations abolish γ-TuC binding and microtubule nucleation without affecting Mto1 localization or Mto2 binding. A separate non-CM1 region is required for Mto2 binding and also contributes to γ-TuC association. Mto1 and Mto2 form a complex (Mto1/2) independent of γ-TuC, and each can weakly associate with γ-TuC in the absence of the other.\",\n      \"method\": \"In vivo mutagenesis, co-immunoprecipitation, live-cell imaging/localization, microtubule nucleation assays (fission yeast genetics)\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal domain mutagenesis with multiple orthogonal readouts (Co-IP, localization, nucleation phenotype) in a rigorous single study\",\n      \"pmids\": [\"19001497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Fission yeast Mto1 contains a conserved C-terminal MASC sequence required for targeting to multiple distinct MTOCs; different MASC subregions target Mto1 to different MTOCs. Mto1 targeting to the cell equator during division requires direct interaction with unconventional type II myosin Myp2. Targeting to the spindle pole body during mitosis depends on SIN components Sid4 and Cdc11.\",\n      \"method\": \"In vivo mutagenesis, live-cell imaging, co-immunoprecipitation (Mto1-Myp2 interaction), genetic dependency analysis (SIN pathway)\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mutagenesis, live imaging, Co-IP, genetics) establishing direct protein-protein interaction and MTOC targeting mechanisms\",\n      \"pmids\": [\"20970338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MTO1-deficient mice (generated by gene trap mutagenesis) develop hypertrophic cardiomyopathy and complex I deficiency with mitochondrial dysfunction in cardiac tissue, mirroring the human disease phenotype.\",\n      \"method\": \"Gene trap mouse model, cardiac morphology, respiratory chain enzyme activity assays (complex I), mitochondrial functional analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cardiac and biochemical phenotype, single lab\",\n      \"pmids\": [\"25506927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MTO1 deficiency in human fibroblasts activates HIF-1, downregulates PPARγ and UCP2, and inactivates AMPK, uncoupling glycolysis from oxidative phosphorylation and causing lipid droplet accumulation; this metabolic reprogramming through the HIF-PPARγ-UCP2-AMPK axis is distinct from that triggered by GTPBP3 deficiency (which activates AMPK and increases UCP2/PPARγ).\",\n      \"method\": \"Patient fibroblast analysis, siRNA-mediated MTO1 silencing, Western blot and activity assays for HIF-1, AMPK, PPARγ, UCP2, fatty acid oxidation assays, lipid droplet staining\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — patient cells plus siRNA knockdown with multiple pathway readouts, single lab\",\n      \"pmids\": [\"29348686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mto1 deficiency in zebrafish (CRISPR/Cas9 knockout) causes: (1) perturbed tRNA structure and reduced stability of tRNAGln, tRNALys, tRNATrp, tRNALeu(UUR); (2) global decrease in aminoacylation of mitochondrial tRNAs with taurine modification; (3) altered polyadenylation of cox1, cox3, and nd1 mRNAs via decreased expression of MTPAP; (4) MTO1 physically interacts with MTPAP (poly(A) polymerase) as shown by immunoprecipitation; (5) impaired mitochondrial translation and reduced OXPHOS complex activities; and (6) heart development defects and hypertrophic cardiomyopathy.\",\n      \"method\": \"CRISPR/Cas9 knockout zebrafish, tRNA structural analysis (S1 nuclease digestion), aminoacylation assays, mRNA polyadenylation analysis, co-immunoprecipitation (MTO1-MTPAP), OXPHOS complex activity assays, cardiac histology\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical methods in a clean KO model, novel interaction (MTO1-MTPAP) confirmed by Co-IP, multiple cellular phenotypes consistently supporting the mechanism\",\n      \"pmids\": [\"33836087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Deletion of MTO1 in yeast carrying the mitochondrial 15S rRNA C1477G mutation (equivalent to human A1555G) suppresses aminoglycoside sensitivity and partially compensates for the energy deficit by upregulating key glycolytic genes (HXK2, PFK1, PYK1), indicating MTO1 acts as a modifier of the neomycin-sensitive phenotype through regulation of mitochondrial tRNA modification and compensatory glycolysis.\",\n      \"method\": \"Yeast genetics (null mutation analysis), growth assays under aminoglycoside treatment, RT-PCR for glycolytic gene expression, mitochondrial function assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with phenotypic and gene expression readouts, single lab\",\n      \"pmids\": [\"25898254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Expression of MTO1 (along with TRMU and GTPBP3) is regulated by specific miRNAs induced by mitochondria-to-nucleus retrograde signals (ROS and Ca2+) in cybrid models of mtDNA diseases; transfection of mutant cybrids with miRNA antagonists improves cell energetic state, demonstrating that miRNA-mediated modulation of MTO1 expression affects mitochondrial tRNA modification status and OXPHOS function.\",\n      \"method\": \"Cybrid cell models, miRNA overexpression/antagonist transfection, OXPHOS activity assays, ROS/Ca2+ pathway analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional intervention (miRNA antagonists) with OXPHOS readout in multiple cybrid models, single lab\",\n      \"pmids\": [\"28740091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In fission yeast, Mto1 and Alp7 interdependently localize to the nuclear envelope (NE) in cells without microtubules; Alp14 localizes to the NE in an Alp7- and Mto1-dependent manner. Artificial tethering of Mto1 to the NE in alp7-deleted cells partially restores microtubule generation from the NE, demonstrating that Mto1 recruitment to the NE is a limiting step for NE-based microtubule nucleation.\",\n      \"method\": \"Live-cell fluorescence microscopy, microtubule repolymerization assay, artificial NE-tethering experiment, genetic deletion analysis\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional tethering rescue, single lab\",\n      \"pmids\": [\"31087092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In fission yeast, loss of Mto1 leads to defects in DNA repair, reduced homologous recombination efficiency, abnormal DNA repair factory dynamics, impaired sister chromatid pairing, and reduced Rad21 cohesin binding along chromosomal arms; this links cytoplasmic microtubule nucleation by Mto1 to chromosomal organization, cohesion, and DNA repair during interphase.\",\n      \"method\": \"Genetic deletion (mto1Δ), DNA repair assays, live-cell imaging of repair foci, ChIP for Rad21 cohesin\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean deletion with multiple cellular phenotype readouts (repair assays, imaging, ChIP), single lab\",\n      \"pmids\": [\"31483748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In fission yeast, Mto1 (together with Mto2 and γ-tubulin) regulates astral microtubule nucleation at the spindle pole body; deletion of Mto1 reduces astral microtubule number, elevates Rho1-GTP at the division site, and, in combination with a bgs1 mutation, causes defective cytokinetic furrow ingression.\",\n      \"method\": \"Genetic deletion analysis, live-cell imaging of microtubules and division site, Rho1-GTP assay, double-mutant epistasis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean deletion with imaging and biochemical readouts, epistasis with bgs1 mutation, single lab\",\n      \"pmids\": [\"32520628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The ER transmembrane protein Erg28 physically interacts with both the Mto1-Mto2 complex and the γ-tubulin small complex (γ-TuSC), significantly attenuating γ-TuSC binding to the Mto1-Mto2 complex; Erg28 inhibits Mto1-Mto2/γ-TuSC-mediated microtubule assembly in vitro; the cytosolic N-terminal region of Erg28 is required for this inhibitory activity; erg28 deletion causes excessive microtubule assembly and nuclear shape deformation.\",\n      \"method\": \"Co-immunoprecipitation (Erg28-Mto1/Mto2, Erg28-γ-TuSC), in vitro microtubule assembly assay, domain deletion mutagenesis, live-cell microscopy\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — biochemical reconstitution (in vitro assembly assay) plus Co-IP and mutagenesis, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"41989917\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Human MTO1 encodes a mitochondrially localized enzyme that catalyzes 5-carboxymethylaminomethylation (cmnm5/τm5) of the wobble uridine in at least five mitochondrial tRNAs (tRNAGlu, tRNAGln, tRNALys, tRNATrp, tRNALeu(UUR)), acting in a complex with MSS1/GTPBP3; this modification is required for tRNA structural stability, aminoacylation, and mitochondrial mRNA stability (including polyadenylation via interaction with MTPAP), collectively ensuring efficient and accurate mitochondrial translation, and deficiency causes combined OXPHOS deficiency, hypertrophic cardiomyopathy, and lactic acidosis; separately, the S. pombe ortholog Mto1 (CDK5RAP2-related) functions as a cytoplasmic microtubule nucleation factor that recruits the γ-tubulin complex to noncentrosomal MTOCs via its CM1 and MASC domains within the Mto1-Mto2 complex, and is in turn negatively regulated by the ER protein Erg28.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MTO1 encodes a mitochondrially targeted enzyme that catalyzes 5-carboxymethylaminomethylation (cmnm5/\\u03c4m5) of the wobble uridine in mitochondrial tRNAs, a modification required for accurate and efficient mitochondrial translation [#4]. The human protein is a structural and functional homolog of yeast Mto1, complementing the respiratory-deficient phenotype of yeast mto1 mutants and confirming evolutionary conservation of its tRNA-modifying role [#1, #2]. Mechanistically, this wobble-uridine modification is required for the structural integrity, steady-state stability, and aminoacylation of multiple mitochondrial tRNAs (tRNAGlu, tRNAGln, tRNALys, tRNATrp, tRNALeu(UUR)), and its loss destabilizes mitochondrial mRNAs and impairs synthesis of OXPHOS subunits [#3, #10]. MTO1 acts within a heterodimeric complex with MSS1/GTPBP3 to optimize mitochondrial protein synthesis [#0], and physically interacts with the mitochondrial poly(A) polymerase MTPAP, coupling tRNA modification to mRNA polyadenylation [#10]. Loss of function causes combined respiratory-chain deficiency, impaired mitochondrial translation, and hypertrophic cardiomyopathy with complex I deficiency in patients and animal models [#4, #5, #8, #10]. Separately, the S. pombe ortholog Mto1 functions as a cytoplasmic microtubule nucleation factor that recruits the \\u03b3-tubulin complex to noncentrosomal MTOCs through its CM1 and MASC domains within an Mto1-Mto2 complex, and is negatively regulated by the ER protein Erg28 [#6, #7, #16].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that Mto1 acts in concert with Mss1 in mitochondria to optimize mitochondrial protein synthesis, defining the founding biochemical partnership before its enzymatic role was known.\",\n      \"evidence\": \"Yeast pulse-labeling, respiratory enzyme assays, and genetic interaction with a paromomycin-resistance allele showing the Mto1\\u00b7Mss1 heterodimer is required for COX1 processing and cytochrome oxidase synthesis\",\n      \"pmids\": [\"9774408\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the chemical modification catalyzed\", \"Did not define which tRNAs are substrates\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed human MTO1 is a functional ortholog by complementing yeast mto1 respiratory defects, extending the conserved mitochondrial role to humans.\",\n      \"evidence\": \"Yeast complementation with human MTO1 cDNA and sequence-based mitochondrial targeting inference\",\n      \"pmids\": [\"12011058\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mitochondrial localization inferred from sequence rather than directly demonstrated\", \"Enzymatic activity not assayed directly\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Confirmed conserved mitochondrial localization and function of the mammalian ortholog in mouse, reinforcing the cross-species tRNA-modification model.\",\n      \"evidence\": \"Subcellular fractionation of mouse Mto1 plus yeast complementation\",\n      \"pmids\": [\"14522080\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab localization\", \"No direct biochemical demonstration of modification activity\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined the downstream consequences of MTO1 loss by showing tRNA modification is required for tRNA stability, aminoacylation, and mitochondrial mRNA stability, connecting modification to translational competence.\",\n      \"evidence\": \"Yeast MTO1 deletion analyzed by Northern blot of tRNA/mRNA levels and aminoacylation assays with genetic controls\",\n      \"pmids\": [\"19460296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the precise chemical modification in human tRNAs\", \"Mechanism linking modification loss to mRNA destabilization not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified the specific catalytic activity (cmnm5 wobble-uridine modification) and established MTO1 as a human disease gene through patient mutations and rescue, the central mechanistic and clinical advance.\",\n      \"evidence\": \"Patient respiratory chain assays, lentiviral wild-type MTO1 rescue, yeast modeling, in vivo mtDNA pulse-labeling, and exome sequencing\",\n      \"pmids\": [\"22608499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Initially defined modification on three tRNAs\", \"Structural basis of catalysis not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended the disease-gene model with additional pathogenic missense mutations validated functionally, solidifying genotype-to-phenotype causality for combined respiratory deficiency.\",\n      \"evidence\": \"Recombinant yeast functional assays (growth, respiration, complex IV, mitochondrial protein synthesis) and patient fibroblast rescue with wild-type MTO1\",\n      \"pmids\": [\"23929671\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specificity of phenotype unexplained\", \"Genotype-phenotype correlation across mutations incomplete\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated in vivo that MTO1 loss produces hypertrophic cardiomyopathy and complex I deficiency in mammals, establishing a faithful disease model.\",\n      \"evidence\": \"Gene-trap MTO1 mouse with cardiac morphology and respiratory chain enzyme assays\",\n      \"pmids\": [\"25506927\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab model\", \"Molecular reason for cardiac selectivity not addressed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed that MTO1 expression is itself regulated by retrograde-signal-induced miRNAs, placing tRNA modification under mitochondria-to-nucleus feedback control.\",\n      \"evidence\": \"Cybrid models with miRNA overexpression/antagonist transfection and OXPHOS activity readouts\",\n      \"pmids\": [\"28740091\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct miRNA-MTO1 transcript targeting not fully mapped\", \"Single-lab cybrid system\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mapped the metabolic reprogramming downstream of MTO1 deficiency, distinguishing its HIF-PPAR\\u03b3-UCP2-AMPK signature from that of GTPBP3 deficiency.\",\n      \"evidence\": \"Patient fibroblasts and siRNA knockdown with Western/activity assays for HIF-1, AMPK, PPAR\\u03b3, UCP2 plus lipid droplet staining\",\n      \"pmids\": [\"29348686\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal ordering within the signaling axis not established\", \"Single-lab observation\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Integrated the full mitochondrial mechanism in vivo by linking MTO1 to tRNA structure/aminoacylation, OXPHOS, cardiomyopathy, and a novel physical interaction with the poly(A) polymerase MTPAP coupling modification to mRNA polyadenylation.\",\n      \"evidence\": \"CRISPR/Cas9 zebrafish knockout with tRNA structural analysis, aminoacylation, polyadenylation assays, MTO1-MTPAP Co-IP, OXPHOS assays, and cardiac histology\",\n      \"pmids\": [\"33836087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"MTO1-MTPAP interaction shown by Co-IP without reciprocal/structural validation\", \"Mechanism by which MTO1 controls MTPAP expression unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"For the S. pombe ortholog, defined CM1 as the \\u03b3-tubulin-complex-binding/nucleation motif and MASC as the MTOC-targeting region, separating the nucleation and localization functions of cytoplasmic Mto1.\",\n      \"evidence\": \"In vivo domain mutagenesis, Co-IP, live imaging, microtubule nucleation assays, and genetic dependency analysis (Myp2, SIN components)\",\n      \"pmids\": [\"19001497\", \"20970338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between fission-yeast cytoplasmic role and the conserved mitochondrial enzyme function unresolved\", \"Structural basis of CM1-\\u03b3-TuC binding not determined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Broadened the cytoplasmic Mto1 roles to NE-based and astral microtubule nucleation and to interphase chromosome organization, cohesion, and DNA repair, showing nucleation activity has downstream chromosomal consequences.\",\n      \"evidence\": \"Fission yeast deletions with live-cell imaging, microtubule repolymerization, NE-tethering rescue, Rho1-GTP assays, DNA repair assays, and Rad21 ChIP\",\n      \"pmids\": [\"31087092\", \"31483748\", \"32520628\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab observations\", \"Direct mechanistic link between microtubule nucleation and cohesin loading not established\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified Erg28 as a negative regulator that competes with \\u03b3-TuSC for the Mto1-Mto2 complex, defining a brake on noncentrosomal microtubule assembly.\",\n      \"evidence\": \"Co-IP (Erg28-Mto1/Mto2 and Erg28-\\u03b3-TuSC), in vitro microtubule assembly reconstitution, domain deletion mutagenesis, and live-cell microscopy\",\n      \"pmids\": [\"41989917\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether an analogous regulator exists for mammalian MTO1 unknown\", \"Structural basis of competitive binding not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the same gene symbol reconciles a conserved mitochondrial tRNA-modifying enzyme with the fission-yeast cytoplasmic microtubule nucleator, and whether these reflect orthologous functions or distinct proteins.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experiment in the corpus bridges the mitochondrial enzymatic and cytoplasmic nucleation activities\", \"Structural model of human MTO1 catalysis absent\", \"Mechanism of cardiac-selective pathology unexplained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [4, 3, 10]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [3, 10]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [6, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [6, 7, 15]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [3, 4, 10]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 4, 5]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 5, 8]}\n    ],\n    \"complexes\": [\n      \"MTO1-MSS1/GTPBP3 complex\",\n      \"Mto1-Mto2 complex\"\n    ],\n    \"partners\": [\n      \"GTPBP3\",\n      \"MTPAP\",\n      \"Mto2\",\n      \"Myp2\",\n      \"Erg28\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}