{"gene":"METTL1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2023,"finding":"Crystal and cryo-EM structures of METTL1-WDR4 with tRNA substrates (with SAM or SAH) show that the composite protein surface recognizes the tRNA elbow through shape complementarity; the METTL1 N terminus couples cofactor binding with conformational changes in the tRNA, catalytic loop, and WDR4 C terminus, acting as an allosteric switch to activate m7G methylation; structural models explain how post-translational modifications of the N terminus regulate methylation.","method":"Crystal structure of METTL1-WDR4 complex; cryo-EM structures of METTL1-WDR4-tRNA with SAM/SAH; multiple active-site conformational states resolved","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal and cryo-EM structures with functional validation, multiple orthogonal methods in one rigorous study","pmids":["36599982"],"is_preprint":false},{"year":2023,"finding":"Structural, biochemical and cellular studies show WDR4 serves as a scaffold for METTL1 and the tRNA T-arm; upon tRNA binding the αC region of METTL1 forms a helix to secure the tRNA variable loop; the predicted-disordered N-terminal region is part of the catalytic pocket and essential for methyltransferase activity; S27 phosphorylation in the METTL1 N-terminal region inhibits methyltransferase activity by disrupting the catalytic centre.","method":"Cryo-EM and X-ray crystallography; biochemical methyltransferase assays; cellular phosphorylation studies; mutagenesis of catalytic residues and S27","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — independent structural study replicating and extending findings from companion paper with reconstitution and mutagenesis","pmids":["36599985"],"is_preprint":false},{"year":2005,"finding":"PKB (AKT) and RSK phosphorylate METTL1 at Ser27 in vitro and in cells; IGF-1 stimulation triggers Ser27 phosphorylation via PI3K/PKB; phosphorylation inactivates METTL1 methyltransferase activity in vitro; phosphomimetic S27D/S27E mutants do not rescue growth of yeast lacking trm8, whereas wild-type or S27A partially rescue, establishing PKB/RSK-mediated inactivation as physiologically relevant.","method":"In vitro kinase assay; phospho-specific detection in HEK293 cells with IGF-1 stimulation; PDK1-deficient ES cell genetics; yeast complementation with WT and mutant alleles","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro enzymatic assay plus mutagenesis plus genetic rescue, replicated across cell systems and yeast","pmids":["15861136"],"is_preprint":false},{"year":2018,"finding":"METTL1 in complex with WDR4 catalyzes m7G modification at a 'RAGGU' motif in the variable loop of a subset of 22 tRNAs in mouse ESCs; Mettl1 knockout causes increased ribosome occupancy (pausing) at m7G-tRNA-decoded codons, impaired global mRNA translation, and defective ESC self-renewal and neural differentiation.","method":"m7G tRNA MeRIP-seq; TRAC-seq; ribosome profiling; Mettl1/Wdr4 knockout mESCs; differentiation assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal sequencing methods, genetic knockout with defined cellular phenotype, ribosome profiling","pmids":["29983320"],"is_preprint":false},{"year":2019,"finding":"METTL1 mediates m7G methylation within a subset of miRNAs including let-7e-5p; METTL1-mediated m7G modification augments let-7 miRNA processing by disrupting an inhibitory secondary structure within the primary miRNA transcript (pri-miRNA); this pathway regulates cell migration and depends on METTL1 catalytic activity.","method":"BoRed-seq (borohydride reduction sequencing); RNA immunoprecipitation; refined mass spectrometry m7G mapping; catalytic mutant rescue of cell migration assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — novel chemical sequencing method, mass spectrometry site mapping, catalytic mutant functional rescue across multiple orthogonal approaches","pmids":["31031083"],"is_preprint":false},{"year":2021,"finding":"METTL1 overexpression increases abundance of m7G-modified tRNAs, in particular Arg-TCT-4-1, and enhances translation of mRNAs enriched in the corresponding AGA codon including cell cycle regulators, inducing oncogenic cell transformation; METTL1 depletion reduces m7G-tRNA abundance and inhibits oncogenicity.","method":"m7G tRNA MeRIP-seq; ribosome/polysome profiling; gain- and loss-of-function in cancer cells; zebrafish and mouse oncogenic transformation models","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal sequencing and functional methods, mechanistic link from tRNA modification to codon-specific translation to transformation established","pmids":["34352207"],"is_preprint":false},{"year":2007,"finding":"The yeast Trm8 (METTL1 ortholog)-Trm82 (WDR4 ortholog) heterodimer requires both D-stem and T-stem structures of tRNA for efficient m7G46 methyl-transfer; tertiary base pairs support but are not essential for catalysis (induced-fit of G46 into catalytic pocket); active heterodimer can only be produced by co-translation of both subunits, not by mixing separately translated subunits.","method":"In vitro methyltransferase activity assays with truncated/mutant tRNA transcripts; wheat germ cell-free co-translation; 2D-TLC and aniline cleavage confirmation of m7G product","journal":"FEBS letters / Journal of biotechnology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted in vitro enzymatic assay with mutagenesis of substrate, co-translation requirement established biochemically","pmids":["17382321","18164779"],"is_preprint":false},{"year":2021,"finding":"METTL1/WDR4-mediated m7G tRNA modification promotes lung cancer growth and invasion; highly translated mRNAs in lung cancer have higher frequencies of m7G tRNA-decoded codons; METTL1 knockdown reduces translation efficiency of mRNAs enriched in m7G tRNA-decoded codons; wild-type but not catalytically dead METTL1 promotes cancer phenotypes.","method":"TRAC-seq; polysome profiling; mRNA translation profiling; gain-of-function mutagenesis; xenograft models","journal":"Molecular therapy","confidence":"High","confidence_rationale":"Tier 2 / Strong — tRNA methylation profiling, polysome sequencing, catalytic mutant validation; independent replication of mechanistic link","pmids":["34371184"],"is_preprint":false},{"year":2021,"finding":"METTL1-mediated tRNA m7G modification promotes translation of target mRNAs containing higher frequencies of m7G-related codons in hepatocellular carcinoma; forced expression of wild-type METTL1 but not its catalytic dead mutant promotes HCC progression; knockin and conditional knockout mouse models confirm the function in hepatocarcinogenesis.","method":"TRAC-seq; polysome profiling and polyribosome-associated mRNA sequencing; catalytic dead mutant; Mettl1 knockin and conditional knockout mice; hydrodynamic transfection HCC model","journal":"Clinical and translational medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods including in vivo genetic models and catalytic dead mutant validation","pmids":["34898034"],"is_preprint":false},{"year":2023,"finding":"METTL1 depletion in prostate cancer causes loss of m7G tRNA methylation and promotes biogenesis of 5' tRNA-derived small RNAs (5'tRFs); these 5'tRFs redirect translation to favor synthesis of tumor growth suppressors, interferon pathway components, and immune effectors; Mettl1 knockdown increases intratumoural pro-inflammatory immune cell infiltration and enhances immunotherapy responses.","method":"m7G tRNA profiling; small RNA sequencing; polysome profiling; preclinical KD mouse models; immunotherapy response assays","journal":"Molecular cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple sequencing approaches and in vivo validation, single lab","pmids":["37516825"],"is_preprint":false},{"year":2022,"finding":"METTL1 ablation in HNSCC reduces m7G levels of 16 tRNAs and inhibits translation of oncogenic transcripts enriched in PI3K/AKT/mTOR pathway genes; chemical modulators of PI3K/AKT/mTOR signaling reverse the effects of Mettl1 loss; Mettl1 knockout also alters immune landscape in tumor microenvironment.","method":"tRNA modification profiling; mRNA translation profiling; transgenic mouse HNSCC models (conditional knockout/knockin); PI3K/AKT/mTOR pathway rescue experiments; scRNA-seq","journal":"Cancer communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic models with pathway-level rescue and multiple sequencing approaches","pmids":["35179319"],"is_preprint":false},{"year":2023,"finding":"Heat-mediated METTL1 upregulation after insufficient radiofrequency ablation enhances TGF-β2 translation via m7G tRNA modification, creating an immunosuppressive microenvironment by inducing PMN-MDSC accumulation and decreasing CD8+ T cell infiltration; knockdown of Tgfb2 or METTL1 or TGF-β signaling blockade reverses this effect.","method":"Liver-specific Mettl1 overexpression/knockdown; multiplex immunofluorescence; in vivo tumor models; anti-Ly6G treatment; siRNA knockdown of Tgfb2","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined mechanistic axis (METTL1→TGF-β2 translation→PMN-MDSC) tested with multiple genetic interventions, single lab","pmids":["35598182"],"is_preprint":false},{"year":2021,"finding":"METTL1 promotes post-ischemic angiogenesis by promoting VEGFA mRNA translation in an m7G methylation-dependent manner; in vivo METTL1 gene transfer improves blood flow recovery and angiogenesis with enhanced mRNA m7G.","method":"In vivo gene transfer; METTL1 plasmid transfection in HUVECs; m7G methylation quantification; proliferation, migration, tube formation assays; polysome profiling","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro functional assays with mechanistic link to m7G-dependent VEGFA translation, single lab","pmids":["34136476"],"is_preprint":false},{"year":2020,"finding":"METTL1 silencing in human iPSCs alters the global m7G tRNA/mRNA profile and reduces translational efficiency of stem cell marker genes, leading to reduced pluripotency; METTL1 knockdown accelerates differentiation toward mesoderm and promotes angiogenesis in vivo.","method":"METTL1 KD hiPSCs; RNA sequencing; anti-m7G northwestern assay; polysome profiling; embryoid body and teratoma formation assays","journal":"Stem cell research & therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (translation profiling, m7G detection, differentiation assays), single lab","pmids":["32698871"],"is_preprint":false},{"year":2023,"finding":"TMEM11 directly interacts with METTL1 and enhances m7G methylation of Atf5 mRNA, increasing ATF5 expression; elevated ATF5 promotes transcription of Inca1 (CDK inhibitor interacting with cyclin A1), suppressing cardiomyocyte proliferation; TMEM11 deletion enhances cardiomyocyte proliferation and cardiac repair.","method":"Co-immunoprecipitation; m7G methylation assays; ATF5 luciferase reporter; loss-of-function in cardiomyocytes; mouse cardiac injury model","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP binding, m7G target identification, genetic loss-of-function with defined phenotypic pathway, single lab","pmids":["37286744"],"is_preprint":false},{"year":2024,"finding":"Mettl1 increases SRSF9 expression by inducing m7G modification of SRSF9 mRNA; elevated SRSF9 facilitates alternative splicing and stabilization of NFATc4, thereby promoting cardiac hypertrophy; Mettl1 knockout alleviates cardiac hypertrophy and SRSF9 knockdown protects against TAC- or Mettl1-induced hypertrophic phenotypes; YY1 acts as a transcription factor for Mettl1 during cardiac hypertrophy.","method":"m7G MeRIP-seq; alternative splicing analysis; cardiac-specific Mettl1 KO and overexpression mouse models; SRSF9 KD in vivo and in vitro; ChIP for YY1","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m7G target identification, genetic models in vivo, splicing mechanistic follow-up, single lab","pmids":["38810124"],"is_preprint":false},{"year":2024,"finding":"METTL1 knockdown leads to decreased m7G modification on tRNAs, destabilization of tRNAs, and facilitation of tsRNA (tRNA-derived small RNA) biogenesis in AML cells; loss of m7G tRNAs decreases global translation efficiency; transfection of tRNAs isolated from METTL1-KD cells is sufficient to decrease global translation.","method":"Northern blotting; LC-MS/MS m7G quantification; tRNA stability analysis; small ncRNA sequencing; quantitative proteomics; nascent protein synthesis measurement","journal":"Experimental hematology & oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (LC-MS/MS, tRNA stability, proteomics), single lab","pmids":["38268051"],"is_preprint":false},{"year":2024,"finding":"METTL1 loss causes tRNA m7G reduction, ribosome stalling at specific codons decoded by m7G-tRNAs, reduced translation efficiency of spermatogenesis genes, and abolishes elongated spermatid and mature sperm production in Drosophila; catalytic-dead Mettl1 transgene cannot rescue, demonstrating the requirement for m7G catalytic activity; m7G modification-dependent tRNA abundance differs between gonadal and non-gonadal tissues.","method":"Mettl1 knockout Drosophila; ribosome profiling; tRNA m7G modification profiling; germ cell-specific transgenic rescue; catalytic-dead allele comparison","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — genetic knockout with catalytic dead rescue in vivo, ribosome profiling, multiple orthogonal approaches","pmids":["39317727"],"is_preprint":false},{"year":2024,"finding":"Perturbation of METTL1-WDR4-mediated m7G46 tRNA methylation decreases tRNA abundance via the rapid tRNA decay (RTD) pathway, causes ribosome stalling at m7G-tRNA-decoded codons, impedes translation of Wnt signaling and ribosome biogenesis mRNAs, and triggers the ribotoxic and integrative stress responses inducing senescence-associated secretory phenotype; restoring eEF1A protein mitigates senescence from METTL1 deficiency by reducing RTD.","method":"METTL1 KD in senescence models; ribosome profiling; tRNA stability assays; RTD pathway analysis; eEF1A rescue experiments; Mettl1/Wdr4 aging measurements","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — ribosome profiling, genetic rescue experiments, multiple mechanistic pathways validated, replicated in multiple models","pmids":["38977661"],"is_preprint":false},{"year":2024,"finding":"METTL1 promotes tRNA aminoacylation and polysome formation independent of its methyltransferase activity by binding the multi-tRNA synthetase complex; phosphomimetic (S27D) and catalytically dead METTL1 alleles phenocopy wild-type METTL1 oncogenic activity in a zebrafish liposarcoma model; METTL1-amplified liposarcomas are hypersensitive to actinomycin D.","method":"Zebrafish liposarcoma model; overexpression of phosphomimetic and catalytic-dead alleles; co-IP with multi-tRNA synthetase complex; polysome profiling; aminoacylation assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — binding partner identified by Co-IP, functional allele comparison, polysome/aminoacylation assays, in vivo genetic model","pmids":["39892392"],"is_preprint":false},{"year":2024,"finding":"Mettl1 regulates postnatal cardiac metabolic reprogramming primarily through translational control of the rate-limiting ketogenesis enzyme Hmgcs2; loss of Mettl1 causes aberrant metabolic reprogramming and cardiomyocyte immaturity leading to heart failure; β-hydroxybutyrate supplementation partially rescues clinical features.","method":"Mettl1 cardiac-specific knockout mice; multi-omics (proteomics + translatomics); polysome profiling; β-hydroxybutyrate rescue; β-hydroxybutyrylation (histone modification) analysis","journal":"Nature cardiovascular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model with multi-omics mechanistic follow-up and metabolite rescue, single lab","pmids":["39587264"],"is_preprint":false},{"year":2024,"finding":"METTL1 catalyzes m7G modification of CYLD deubiquitinase mRNA, increasing CYLD expression; elevated CYLD enhances stability of P53 by preventing its ubiquitination and degradation; P53 in turn transcriptionally activates METTL1 forming a positive feedback loop promoting cardiomyocyte apoptosis during ischemia/reperfusion; CYLD knockdown mitigates Mettl1-overexpression-induced apoptosis.","method":"RNA sequencing + m7G-methylated RNA sequencing in Mettl1-overexpressing hearts; m7G MeRIP; CYLD KD rescue; P53 ChIP; ubiquitination assays","journal":"Acta pharmacologica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m7G target sequencing, genetic epistasis (CYLD KD rescue), P53 ChIP, single lab","pmids":["39414959"],"is_preprint":false},{"year":2023,"finding":"P300 forms a complex with SP1 and binds the METTL1 promoter via SP1, mediating METTL1 transcriptional upregulation in castration-resistant prostate cancer; METTL1 then adds internal m7G modifications to CDK14 mRNA, enhancing its stability and expression to promote CRPC progression.","method":"ChIP-qPCR; Co-IP; luciferase reporter assay; m7G AlkAniline-Seq; mRNA degradation assays; transcriptome sequencing","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (ChIP, Co-IP, m7G sequencing, mRNA stability), single lab","pmids":["37599359"],"is_preprint":false},{"year":2023,"finding":"METTL1 enhances TXNDC12 mRNA stability via m7G-dependent mechanism; TXNDC12 in turn stabilizes c-Myc protein by promoting its interaction with USP5, preventing proteasomal degradation of c-Myc in HNSCC.","method":"m7G-MeRIP; mRNA stability assays; co-IP (TXNDC12-USP5 interaction); RNA transcriptomic analysis","journal":"Experimental & molecular medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited methodological detail in abstract for the METTL1 step specifically","pmids":["40750708"],"is_preprint":false},{"year":2024,"finding":"METTL1 modulates LSM14A expression via mRNA m7G methylation; LSM14A stabilizes DDX5 in the cytoplasm during G1/S phase, regulating CDK4 and P21 levels in glioblastoma.","method":"MeRIP; co-immunoprecipitation; protein half-life assay; mass spectrometry","journal":"iScience","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, m7G methylation of LSM14A shown but downstream DDX5 stabilization mechanistic link is limited","pmids":["39040050"],"is_preprint":false},{"year":2025,"finding":"METTL1-mediated m7G modification of Sarm1 mRNA enhances its stability and expression in macrophages; elevated SARM1 induces NAD+ decline and metabolic reprogramming, promoting macrophage proinflammatory responses; METTL1 deficiency in myeloid cells mitigates multiorgan inflammation.","method":"m7G-MeRIP-seq; mRNA stability assay; SARM1 rescue experiments; myeloid-specific Mettl1 KO mice; cecal ligation and puncture / ischemia-reperfusion models","journal":"Science immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m7G sequencing, genetic rescue, in vivo myeloid-specific KO, single lab","pmids":["40911698"],"is_preprint":false},{"year":2024,"finding":"METTL1 mediates m7G methylation of PKM mRNA, enhancing PKM2 expression and glycolysis; increased PKM2 dimer nuclear translocation activates CD155 expression causing CRC immune evasion; elevated glycolysis promotes H3K9 lactylation (H3K9la) which activates METTL1 transcription, forming a positive feedback loop.","method":"MeRIP assay; RIP; RNA stability analysis; extracellular acidification rate measurement; Cut&Run for H3K9la; METTL1 KO mice with CD155 blockers","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — m7G target validation, multiple mechanistic assays, in vivo KO with functional rescue, single lab","pmids":["39741310"],"is_preprint":false},{"year":2023,"finding":"METTL3-mediated m6A modification of METTL1 mRNA elevates METTL1 expression in HNSCC; METTL1 physically binds the CDK4 transcript and regulates its m7G modification level to stabilize CDK4, promoting cell cycle progression.","method":"Database mining (GEPIA); RIP to confirm METTL1-CDK4 mRNA interaction; m7G modification level measurement; CDK4 rescue experiments","journal":"Biological chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, RIP without rigorous controls, limited mechanistic detail in abstract","pmids":["37694982"],"is_preprint":false},{"year":2020,"finding":"METTL1 knockdown in hiPSC-derived EPCs activates the MAPK/ERK signaling pathway during EPC differentiation, significantly increasing EPC marker expression and functional properties; METTL1-KD EPCs accelerate vascular smooth muscle cell proliferation via co-culture.","method":"METTL1 KD hiPSCs; immunofluorescence; FACS; co-culture system; MAPK/ERK pathway analysis","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, pathway activation observed but causal link to m7G not directly established","pmids":["32430183"],"is_preprint":false},{"year":2023,"finding":"HIF-1α binds to a hypoxia response element (HRE) in the METTL1 promoter and directly represses METTL1 transcription under hypoxic conditions in CRC cells, leading to decreased m7G tRNA modification.","method":"METTL1 promoter activity luciferase assay; HIF-1α siRNA; ChIP assay; LC-MS/MS quantification of RNA modifications","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP, promoter reporter assay, siRNA, and mass spec quantification; single lab","pmids":["38118310"],"is_preprint":false},{"year":2020,"finding":"Thyroid hormone receptor (TR) directly activates Mettl1 gene transcription via a T3 response element (TRE) in the promoter; TR binding correlates with increased H3K79 methylation and RNA polymerase II recruitment during Xenopus intestinal metamorphosis.","method":"T3-induced Xenopus metamorphosis model; ChIP for TR binding, H3K79me, and Pol II at Mettl1 TRE; promoter activation assay","journal":"Cell & bioscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct ChIP evidence of TR binding at TRE with histone mark correlation, in vivo developmental model, single lab","pmids":["32391142"],"is_preprint":false},{"year":2024,"finding":"METTL1-mediated m7G modification of TEAD2 mRNA enhances its stability via the binding protein Quaking; elevated TEAD2 transcriptionally represses ACADM, impairing mitochondrial function and amplifying proinflammatory responses in kidney tubular epithelial cells during AKI.","method":"m7G-methylated RNA immunoprecipitation sequencing; RNA sequencing; TEC-specific Mettl1 conditional KO mice (multiple AKI models); Quaking binding assays","journal":"Kidney international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO in multiple disease models, m7G sequencing, Quaking reader interaction identified, single lab","pmids":["41407011"],"is_preprint":false},{"year":2024,"finding":"METTL1 promotes METTL1-mediated m7G modification of SRSF9 mRNA and drives METTL1-mediated hepatic regeneration after partial hepatectomy by selectively augmenting translation of Hippo pathway effectors YAP/TAZ via m7G tRNA modification.","method":"Multi-omics (proteomics + translatomics); Mettl1 KO mice; ectopic Mettl1 expression; 70% PHx murine model; polysome profiling","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model, multi-omics mechanistic link to YAP/TAZ translation, single lab","pmids":["41360736"],"is_preprint":false},{"year":2024,"finding":"METTL1 loss reduces m7G modification on tRNAPheGAA specifically, decreasing its steady-state levels and causing translation suppression/degradation of mRNAs enriched in corresponding codons including HCK tyrosine kinase; decreased HCK disrupts CXCR4 signaling, impairing leukemia stem cell self-renewal and bone marrow homing; pharmacological METTL1 inhibition (NSC137443) recapitulates these effects.","method":"tRNA m7G profiling; translation/proteomics profiling; CXCR4 signaling assays; AML mouse models; high-throughput screening for small-molecule inhibitor","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific tRNA target identified, mechanistic cascade validated, pharmacological inhibitor confirmation, single lab","pmids":["42247311"],"is_preprint":false},{"year":2025,"finding":"METTL1 interacts with XPO5 (exportin-5) as identified by APEX2 proximity labeling; METTL1 deletion causes XPO5 redistribution to the cytosol, accelerating pre-miRNA export and enhancing miRNA maturation independent of METTL1 m7G methyltransferase activity; mechanistically METTL1 facilitates ERK-mediated phosphorylation of XPO5 to promote its nuclear retention.","method":"APEX2 proximity labeling + LC-MS/MS; co-immunoprecipitation; western blot; METTL1 knockout; ERK pathway manipulation; constitutively active ERK rescue","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity labeling interactome, Co-IP validation, genetic KO phenotype with ERK rescue, single lab","pmids":["41591839"],"is_preprint":false},{"year":2024,"finding":"METTL1 mediates m7G modification of B-cell tRNAs to preferentially translate BCR signaling-related proteins and maintain mitochondrial electron transport chain activity; conditional Mettl1 knockout in B cells blocks germinal center entry and GC formation; conditional knock-in promotes GC responses; METTL1-mediated tRNA m7G controls B-cell autoreactivity in SLE.","method":"B cell-specific Mettl1 conditional KO and knock-in mice; m7G tRNA profiling; translation profiling; mitochondrial function assays; lupus-prone mouse model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO and knock-in genetic models, tRNA and translation profiling, mitochondrial functional assays, disease model validation","pmids":["39638793"],"is_preprint":false},{"year":2025,"finding":"In oesophageal cancer cells resistant to METTL1 loss, tRNA balance is preserved upon m7G46 deficiency by compensatory elevation of dihydrouridylation at position 47 (D47) by DUS3L; depletion of DUS-L enzymes sensitises resistant cells to METTL1 loss; concomitant loss of both modifications destabilizes canonical tRNA L-shape and disrupts coaxial helix stacking and anticodon-loop presentation.","method":"METTL1 depletion in resistant vs sensitive cell lines; DUS3L/DUS-L depletion; tRNA structural analysis; fitness/proliferation assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis, tRNA structural analysis, functional assays; preprint not yet peer reviewed","pmids":["41279591"],"is_preprint":true},{"year":2025,"finding":"METTL1 depletion in Mettl1-specific mesenchymal stem cells disrupts m7G modification of Fgfr2 mRNA, reducing its stability; Fgfr2 downregulation impairs PI3K-AKT and MAPK signaling pathways, decreases Sp1 phosphorylation and promotes its ubiquitin-mediated degradation, ultimately reducing Col1a1 and Col2a1 transcription and blocking osteoblast/chondrocyte differentiation; pharmacological Fgfr2 reactivation rescues the bone defects.","method":"Mettl1 conditional KO in mesenchymal lineage; m7G-MeRIP sequencing; single-cell RNA sequencing; Fgfr2 mRNA stability assay; Sp1 ubiquitination assay; pharmacological rescue","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with m7G-MeRIP and scRNA-seq mechanistic follow-up, pharmacological rescue, single lab","pmids":["41079929"],"is_preprint":false},{"year":2023,"finding":"NSUN5 (m5C methyltransferase) directly binds the METTL1 transcript and facilitates its m5C modification, positively regulating METTL1 expression; overexpression of METTL1 counteracts tumor-suppressive effects of NSUN5 ablation in esophageal cancer.","method":"RNA co-immunoprecipitation; RNA pull-down; NSUN5 KD with METTL1 rescue experiments; xenograft models","journal":"Molecular carcinogenesis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, RIP/pull-down interaction, limited mechanistic detail about m5C modification functional consequence","pmids":["39601515"],"is_preprint":false}],"current_model":"METTL1 functions as the catalytic subunit of the METTL1-WDR4 heterodimeric complex (structurally characterized by cryo-EM/crystallography) that deposits N7-methylguanosine (m7G) at position 46 in the variable loop of a subset of tRNAs carrying a 'RAGGU' motif, stabilizing tRNA structure and preventing rapid tRNA decay; this modification sustains translational efficiency at the corresponding codons, selectively enhancing synthesis of proteins encoded by mRNAs enriched in those codons (e.g., cell cycle regulators, oncogenes, signaling pathway components); METTL1 activity is regulated by AKT/PKB and RSK phosphorylation at Ser27 in its disordered N-terminal region, which inhibits catalysis; METTL1 additionally methylates internal positions in select mRNAs and miRNA precursors (augmenting let-7 biogenesis by disrupting inhibitory RNA structure), binds the multi-tRNA synthetase complex to promote tRNA aminoacylation independent of its methyltransferase activity, and interacts with XPO5 to regulate pre-miRNA nuclear export via ERK-mediated XPO5 phosphorylation, placing METTL1 at the intersection of tRNA biology, translational control, and RNA processing with broad consequences for cell growth, differentiation, immune function, and disease."},"narrative":{"mechanistic_narrative":"METTL1 is the catalytic subunit of a heterodimeric tRNA methyltransferase that, with its scaffold partner WDR4, deposits N7-methylguanosine (m7G46) in the variable loop of a defined subset of tRNAs bearing a 'RAGGU' motif, thereby coupling tRNA modification to codon-specific translational control of cell growth, differentiation, and immune function [PMID:29983320, PMID:34352207]. Structural work shows the composite METTL1-WDR4 surface recognizes the tRNA elbow through shape complementarity, with the predicted-disordered METTL1 N terminus forming part of the catalytic pocket and acting as an allosteric switch that couples cofactor binding to substrate-induced conformational changes; the active heterodimer must be co-assembled with WDR4 to be catalytically competent [PMID:36599982, PMID:36599985, PMID:17382321, PMID:18164779]. This activity is regulated by growth-factor signaling: PKB/AKT and RSK phosphorylate METTL1 at Ser27 in the N-terminal region, disrupting the catalytic center and inactivating the enzyme [PMID:36599985, PMID:15861136]. m7G modification stabilizes target tRNAs against the rapid tRNA decay pathway and sustains translation; its loss reduces tRNA abundance, drives ribosome stalling at m7G-decoded codons, promotes biogenesis of tRNA-derived small RNAs, and reprograms the translatome, with consequences spanning self-renewal, oncogenic transformation, immune-cell programs, and tissue homeostasis [PMID:29983320, PMID:34352207, PMID:38268051, PMID:38977661]. Across many tissues METTL1 selectively enhances translation of mRNAs enriched in m7G-tRNA-decoded codons—including cell cycle regulators, PI3K/AKT/mTOR components, and other oncogenic transcripts—and catalytically dead alleles fail to recapitulate these phenotypes, establishing methyltransferase activity as the operative mechanism [PMID:34352207, PMID:34371184, PMID:34898034, PMID:35179319, PMID:39317727]. Beyond tRNA, METTL1 catalyzes internal m7G on select mRNAs and on miRNA precursors, augmenting let-7 biogenesis by disrupting an inhibitory secondary structure [PMID:31031083]. It also exerts methyltransferase-independent functions: it binds the multi-tRNA synthetase complex to promote tRNA aminoacylation and polysome formation, and it interacts with XPO5 to restrain pre-miRNA nuclear export via ERK-mediated XPO5 phosphorylation [PMID:39892392, PMID:41591839].","teleology":[{"year":2005,"claim":"Established that METTL1 is a growth-factor-regulated enzyme, answering whether its tRNA methyltransferase activity is subject to signaling control.","evidence":"In vitro kinase assays, phospho-specific detection with IGF-1 stimulation, and yeast trm8 complementation with phosphomutant alleles","pmids":["15861136"],"confidence":"High","gaps":["Did not resolve the structural basis for how Ser27 phosphorylation inactivates catalysis","Physiological signals beyond IGF-1/PI3K driving Ser27 phosphorylation not mapped"]},{"year":2007,"claim":"Defined the substrate requirements and obligate heterodimeric nature of the methyltransferase using the yeast Trm8-Trm82 ortholog, answering how the enzyme recognizes tRNA and assembles.","evidence":"Reconstituted in vitro methyltransferase assays with truncated/mutant tRNAs and wheat-germ co-translation","pmids":["17382321","18164779"],"confidence":"High","gaps":["Yeast ortholog; human substrate spectrum not yet defined here","Atomic basis of co-translational assembly requirement not resolved"]},{"year":2018,"claim":"Connected m7G tRNA modification to codon-specific translation and cell fate, answering what the modification does functionally in mammalian cells.","evidence":"m7G tRNA MeRIP-seq, TRAC-seq, ribosome profiling in Mettl1/Wdr4 knockout mouse ESCs with differentiation assays","pmids":["29983320"],"confidence":"High","gaps":["Did not establish disease relevance","Mechanism linking tRNA loss to decay not yet defined"]},{"year":2019,"claim":"Extended substrate scope beyond tRNA by showing METTL1 m7G-modifies miRNA precursors, answering whether the enzyme acts on other RNA classes.","evidence":"BoRed-seq, RNA-IP, mass-spectrometry site mapping, and catalytic-mutant rescue of migration","pmids":["31031083"],"confidence":"High","gaps":["Breadth of miRNA targets beyond let-7 not fully enumerated","Interplay between tRNA and miRNA functions not dissected"]},{"year":2021,"claim":"Established METTL1 as an oncogenic driver acting through codon-biased translation, answering how the enzyme contributes to cancer across tissues.","evidence":"m7G tRNA MeRIP-seq, polysome/ribosome profiling, catalytic-dead alleles, and xenograft/in vivo models in liver, lung, and transformation systems","pmids":["34352207","34371184","34898034"],"confidence":"High","gaps":["Specific tRNA isoacceptors driving each cancer not uniformly defined","Did not address methyltransferase-independent contributions"]},{"year":2022,"claim":"Linked METTL1-dependent translation to specific oncogenic signaling output and the tumor immune microenvironment, answering which downstream pathways are selectively translated.","evidence":"Conditional knockout/knockin mouse HNSCC models with PI3K/AKT/mTOR pathway rescue and scRNA-seq","pmids":["35179319"],"confidence":"High","gaps":["Mechanism of immune-landscape remodeling not fully resolved at this step"]},{"year":2023,"claim":"Resolved the structural and allosteric basis of m7G catalysis and its regulation, answering how the complex recognizes substrate and how Ser27 phosphorylation inhibits it.","evidence":"Crystal and cryo-EM structures of METTL1-WDR4-tRNA with SAM/SAH, biochemical assays, and mutagenesis of catalytic residues and S27","pmids":["36599982","36599985"],"confidence":"High","gaps":["Dynamics of the disordered N terminus in cells not directly observed","Structural basis for non-tRNA substrate recognition not addressed"]},{"year":2023,"claim":"Showed METTL1 loss reroutes translation through tRNA-derived small RNAs to favor tumor-suppressive and immune programs, answering how depletion can be exploited therapeutically.","evidence":"m7G tRNA and small-RNA profiling, polysome profiling, and preclinical knockdown plus immunotherapy-response models in prostate cancer","pmids":["37516825"],"confidence":"Medium","gaps":["Single lab; 5'tRF targets not exhaustively mapped","Generalizability across tumor types not established"]},{"year":2024,"claim":"Identified the rapid tRNA decay pathway as the mechanistic link between m7G loss and reduced tRNA abundance, answering why modification loss destabilizes tRNAs and triggers stress responses.","evidence":"Ribosome profiling, tRNA stability and RTD assays, and eEF1A rescue in senescence and AML models","pmids":["38977661","38268051"],"confidence":"High","gaps":["Quantitative contribution of RTD versus tRF biogenesis not fully partitioned","Tissue-specific decay thresholds undefined"]},{"year":2024,"claim":"Demonstrated in vivo requirement for METTL1 catalytic activity in differentiation and tissue-specific physiology, answering whether m7G activity is essential across developmental and immune contexts.","evidence":"Catalytic-dead rescue in Drosophila spermatogenesis, and B-cell conditional KO/knock-in mice with tRNA, translation, and mitochondrial assays","pmids":["39317727","39638793"],"confidence":"High","gaps":["Tissue-specific tRNA dependency mechanisms not fully generalized"]},{"year":2024,"claim":"Uncovered methyltransferase-independent functions of METTL1, answering whether all of its activity depends on m7G catalysis.","evidence":"Zebrafish liposarcoma model with phosphomimetic/catalytic-dead alleles, co-IP with the multi-tRNA synthetase complex, and aminoacylation/polysome assays","pmids":["39892392"],"confidence":"High","gaps":["Structural basis of multi-tRNA synthetase complex binding unknown","Relative weight of catalytic vs non-catalytic roles in human tumors unresolved"]},{"year":2024,"claim":"Catalogued METTL1 transcriptional and post-transcriptional regulation, answering how its expression is controlled across disease and developmental states.","evidence":"ChIP, promoter reporters, and modification mapping implicating HIF-1α repression, thyroid hormone receptor activation, SP1/P300, YY1, METTL3-m6A, and NSUN5-m5C","pmids":["38118310","32391142","37599359","38810124","37694982","39601515"],"confidence":"Medium","gaps":["Several regulatory links rest on single-lab or low-confidence data","Integration of competing upstream regulators not modeled"]},{"year":2025,"claim":"Identified a non-catalytic METTL1-XPO5 axis controlling pre-miRNA export, answering an additional methyltransferase-independent function in RNA processing.","evidence":"APEX2 proximity labeling with LC-MS/MS, co-IP, METTL1 knockout, and ERK-pathway manipulation/rescue","pmids":["41591839"],"confidence":"Medium","gaps":["Single lab; reciprocal validation and structural basis of the interaction not established","Physiological consequences of altered miRNA export in vivo unclear"]},{"year":null,"claim":"How METTL1's catalytic and non-catalytic activities are coordinated, and which mRNA versus tRNA substrates dominate in any given physiological or disease context, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model partitioning tRNA-, mRNA-, miRNA-, synthetase-, and XPO5-related functions","Direct mRNA m7G targets often inferred from single-lab studies without orthogonal site mapping","In vivo relevance of Ser27 phosphorylation regulation across tissues not systematically tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,1,3,4,5,6,17]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,3,6]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[4,19,22,34]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[34]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[19,34]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[3,4,5,18]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,5,7,17,19]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[5,7,8,10]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[25,35]}],"complexes":["METTL1-WDR4 m7G methyltransferase complex","multi-tRNA synthetase complex (associated)"],"partners":["WDR4","XPO5","TMEM11","QKI"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UBP6","full_name":"tRNA (guanine-N(7)-)-methyltransferase","aliases":["Methyltransferase-like protein 1","mRNA (guanine-N(7)-)-methyltransferase","miRNA (guanine-N(7)-)-methyltransferase","tRNA (guanine(46)-N(7))-methyltransferase","tRNA(m7G46)-methyltransferase"],"length_aa":276,"mass_kda":31.5,"function":"Catalytic component of METTL1-WDR4 methyltransferase complex that mediates the formation of N(7)-methylguanine in a subset of RNA species, such as tRNAs, mRNAs and microRNAs (miRNAs) (PubMed:12403464, PubMed:31031083, PubMed:31031084, PubMed:36599982, PubMed:36599985, PubMed:37369656, PubMed:37379838). Catalyzes the formation of N(7)-methylguanine at position 46 (m7G46) in a large subset of tRNAs that contain the 5'-RAGGU-3' motif within the variable loop (PubMed:12403464, PubMed:34352206, PubMed:34352207, PubMed:36599982, PubMed:36599985, PubMed:37369656). M7G46 interacts with C13-G22 in the D-loop to stabilize tRNA tertiary structure and protect tRNAs from decay (PubMed:36599982, PubMed:36599985). Also acts as a methyltransferase for a subset of internal N(7)-methylguanine in mRNAs (PubMed:31031084, PubMed:37379838). Internal N(7)-methylguanine methylation of mRNAs in response to stress promotes their relocalization to stress granules, thereby suppressing their translation (PubMed:31031084, PubMed:37379838). Also methylates a specific subset of miRNAs, such as let-7 (PubMed:31031083). N(7)-methylguanine methylation of let-7 miRNA promotes let-7 miRNA processing by disrupting an inhibitory secondary structure within the primary miRNA transcript (pri-miRNA) (PubMed:31031083). Acts as a regulator of embryonic stem cell self-renewal and differentiation (By similarity)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9UBP6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/METTL1","classification":"Not Classified","n_dependent_lines":684,"n_total_lines":1208,"dependency_fraction":0.5662251655629139},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SSB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/METTL1","total_profiled":1310},"omim":[{"mim_id":"618347","title":"GALLOWAY-MOWAT SYNDROME 6; GAMOS6","url":"https://www.omim.org/entry/618347"},{"mim_id":"609506","title":"CYTOCHROME P450, SUBFAMILY XXVIIB, POLYPEPTIDE 1; CYP27B1","url":"https://www.omim.org/entry/609506"},{"mim_id":"605924","title":"WD REPEAT-CONTAINING PROTEIN 4; WDR4","url":"https://www.omim.org/entry/605924"},{"mim_id":"604466","title":"METHYLTRANSFERASE 1, tRNA METHYLGUANOSINE; METTL1","url":"https://www.omim.org/entry/604466"},{"mim_id":"126200","title":"MULTIPLE SCLEROSIS, SUSCEPTIBILITY TO; MS","url":"https://www.omim.org/entry/126200"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/METTL1"},"hgnc":{"alias_symbol":["TRM8","TRMT8"],"prev_symbol":["C12orf1"]},"alphafold":{"accession":"Q9UBP6","domains":[{"cath_id":"3.40.50.150","chopping":"74-272","consensus_level":"high","plddt":95.1328,"start":74,"end":272}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBP6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBP6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UBP6-F1-predicted_aligned_error_v6.png","plddt_mean":88.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=METTL1","jax_strain_url":"https://www.jax.org/strain/search?query=METTL1"},"sequence":{"accession":"Q9UBP6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UBP6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UBP6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UBP6"}},"corpus_meta":[{"pmid":"31031083","id":"PMC_31031083","title":"METTL1 Promotes 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switch to activate m7G methylation; structural models explain how post-translational modifications of the N terminus regulate methylation.\",\n      \"method\": \"Crystal structure of METTL1-WDR4 complex; cryo-EM structures of METTL1-WDR4-tRNA with SAM/SAH; multiple active-site conformational states resolved\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal and cryo-EM structures with functional validation, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"36599982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Structural, biochemical and cellular studies show WDR4 serves as a scaffold for METTL1 and the tRNA T-arm; upon tRNA binding the αC region of METTL1 forms a helix to secure the tRNA variable loop; the predicted-disordered N-terminal region is part of the catalytic pocket and essential for methyltransferase activity; S27 phosphorylation in the METTL1 N-terminal region inhibits methyltransferase activity by disrupting the catalytic centre.\",\n      \"method\": \"Cryo-EM and X-ray crystallography; biochemical methyltransferase assays; cellular phosphorylation studies; mutagenesis of catalytic residues and S27\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — independent structural study replicating and extending findings from companion paper with reconstitution and mutagenesis\",\n      \"pmids\": [\"36599985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PKB (AKT) and RSK phosphorylate METTL1 at Ser27 in vitro and in cells; IGF-1 stimulation triggers Ser27 phosphorylation via PI3K/PKB; phosphorylation inactivates METTL1 methyltransferase activity in vitro; phosphomimetic S27D/S27E mutants do not rescue growth of yeast lacking trm8, whereas wild-type or S27A partially rescue, establishing PKB/RSK-mediated inactivation as physiologically relevant.\",\n      \"method\": \"In vitro kinase assay; phospho-specific detection in HEK293 cells with IGF-1 stimulation; PDK1-deficient ES cell genetics; yeast complementation with WT and mutant alleles\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro enzymatic assay plus mutagenesis plus genetic rescue, replicated across cell systems and yeast\",\n      \"pmids\": [\"15861136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"METTL1 in complex with WDR4 catalyzes m7G modification at a 'RAGGU' motif in the variable loop of a subset of 22 tRNAs in mouse ESCs; Mettl1 knockout causes increased ribosome occupancy (pausing) at m7G-tRNA-decoded codons, impaired global mRNA translation, and defective ESC self-renewal and neural differentiation.\",\n      \"method\": \"m7G tRNA MeRIP-seq; TRAC-seq; ribosome profiling; Mettl1/Wdr4 knockout mESCs; differentiation assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal sequencing methods, genetic knockout with defined cellular phenotype, ribosome profiling\",\n      \"pmids\": [\"29983320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"METTL1 mediates m7G methylation within a subset of miRNAs including let-7e-5p; METTL1-mediated m7G modification augments let-7 miRNA processing by disrupting an inhibitory secondary structure within the primary miRNA transcript (pri-miRNA); this pathway regulates cell migration and depends on METTL1 catalytic activity.\",\n      \"method\": \"BoRed-seq (borohydride reduction sequencing); RNA immunoprecipitation; refined mass spectrometry m7G mapping; catalytic mutant rescue of cell migration assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — novel chemical sequencing method, mass spectrometry site mapping, catalytic mutant functional rescue across multiple orthogonal approaches\",\n      \"pmids\": [\"31031083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"METTL1 overexpression increases abundance of m7G-modified tRNAs, in particular Arg-TCT-4-1, and enhances translation of mRNAs enriched in the corresponding AGA codon including cell cycle regulators, inducing oncogenic cell transformation; METTL1 depletion reduces m7G-tRNA abundance and inhibits oncogenicity.\",\n      \"method\": \"m7G tRNA MeRIP-seq; ribosome/polysome profiling; gain- and loss-of-function in cancer cells; zebrafish and mouse oncogenic transformation models\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal sequencing and functional methods, mechanistic link from tRNA modification to codon-specific translation to transformation established\",\n      \"pmids\": [\"34352207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The yeast Trm8 (METTL1 ortholog)-Trm82 (WDR4 ortholog) heterodimer requires both D-stem and T-stem structures of tRNA for efficient m7G46 methyl-transfer; tertiary base pairs support but are not essential for catalysis (induced-fit of G46 into catalytic pocket); active heterodimer can only be produced by co-translation of both subunits, not by mixing separately translated subunits.\",\n      \"method\": \"In vitro methyltransferase activity assays with truncated/mutant tRNA transcripts; wheat germ cell-free co-translation; 2D-TLC and aniline cleavage confirmation of m7G product\",\n      \"journal\": \"FEBS letters / Journal of biotechnology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted in vitro enzymatic assay with mutagenesis of substrate, co-translation requirement established biochemically\",\n      \"pmids\": [\"17382321\", \"18164779\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"METTL1/WDR4-mediated m7G tRNA modification promotes lung cancer growth and invasion; highly translated mRNAs in lung cancer have higher frequencies of m7G tRNA-decoded codons; METTL1 knockdown reduces translation efficiency of mRNAs enriched in m7G tRNA-decoded codons; wild-type but not catalytically dead METTL1 promotes cancer phenotypes.\",\n      \"method\": \"TRAC-seq; polysome profiling; mRNA translation profiling; gain-of-function mutagenesis; xenograft models\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — tRNA methylation profiling, polysome sequencing, catalytic mutant validation; independent replication of mechanistic link\",\n      \"pmids\": [\"34371184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"METTL1-mediated tRNA m7G modification promotes translation of target mRNAs containing higher frequencies of m7G-related codons in hepatocellular carcinoma; forced expression of wild-type METTL1 but not its catalytic dead mutant promotes HCC progression; knockin and conditional knockout mouse models confirm the function in hepatocarcinogenesis.\",\n      \"method\": \"TRAC-seq; polysome profiling and polyribosome-associated mRNA sequencing; catalytic dead mutant; Mettl1 knockin and conditional knockout mice; hydrodynamic transfection HCC model\",\n      \"journal\": \"Clinical and translational medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods including in vivo genetic models and catalytic dead mutant validation\",\n      \"pmids\": [\"34898034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL1 depletion in prostate cancer causes loss of m7G tRNA methylation and promotes biogenesis of 5' tRNA-derived small RNAs (5'tRFs); these 5'tRFs redirect translation to favor synthesis of tumor growth suppressors, interferon pathway components, and immune effectors; Mettl1 knockdown increases intratumoural pro-inflammatory immune cell infiltration and enhances immunotherapy responses.\",\n      \"method\": \"m7G tRNA profiling; small RNA sequencing; polysome profiling; preclinical KD mouse models; immunotherapy response assays\",\n      \"journal\": \"Molecular cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple sequencing approaches and in vivo validation, single lab\",\n      \"pmids\": [\"37516825\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"METTL1 ablation in HNSCC reduces m7G levels of 16 tRNAs and inhibits translation of oncogenic transcripts enriched in PI3K/AKT/mTOR pathway genes; chemical modulators of PI3K/AKT/mTOR signaling reverse the effects of Mettl1 loss; Mettl1 knockout also alters immune landscape in tumor microenvironment.\",\n      \"method\": \"tRNA modification profiling; mRNA translation profiling; transgenic mouse HNSCC models (conditional knockout/knockin); PI3K/AKT/mTOR pathway rescue experiments; scRNA-seq\",\n      \"journal\": \"Cancer communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic models with pathway-level rescue and multiple sequencing approaches\",\n      \"pmids\": [\"35179319\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Heat-mediated METTL1 upregulation after insufficient radiofrequency ablation enhances TGF-β2 translation via m7G tRNA modification, creating an immunosuppressive microenvironment by inducing PMN-MDSC accumulation and decreasing CD8+ T cell infiltration; knockdown of Tgfb2 or METTL1 or TGF-β signaling blockade reverses this effect.\",\n      \"method\": \"Liver-specific Mettl1 overexpression/knockdown; multiplex immunofluorescence; in vivo tumor models; anti-Ly6G treatment; siRNA knockdown of Tgfb2\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined mechanistic axis (METTL1→TGF-β2 translation→PMN-MDSC) tested with multiple genetic interventions, single lab\",\n      \"pmids\": [\"35598182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"METTL1 promotes post-ischemic angiogenesis by promoting VEGFA mRNA translation in an m7G methylation-dependent manner; in vivo METTL1 gene transfer improves blood flow recovery and angiogenesis with enhanced mRNA m7G.\",\n      \"method\": \"In vivo gene transfer; METTL1 plasmid transfection in HUVECs; m7G methylation quantification; proliferation, migration, tube formation assays; polysome profiling\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro functional assays with mechanistic link to m7G-dependent VEGFA translation, single lab\",\n      \"pmids\": [\"34136476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"METTL1 silencing in human iPSCs alters the global m7G tRNA/mRNA profile and reduces translational efficiency of stem cell marker genes, leading to reduced pluripotency; METTL1 knockdown accelerates differentiation toward mesoderm and promotes angiogenesis in vivo.\",\n      \"method\": \"METTL1 KD hiPSCs; RNA sequencing; anti-m7G northwestern assay; polysome profiling; embryoid body and teratoma formation assays\",\n      \"journal\": \"Stem cell research & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (translation profiling, m7G detection, differentiation assays), single lab\",\n      \"pmids\": [\"32698871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TMEM11 directly interacts with METTL1 and enhances m7G methylation of Atf5 mRNA, increasing ATF5 expression; elevated ATF5 promotes transcription of Inca1 (CDK inhibitor interacting with cyclin A1), suppressing cardiomyocyte proliferation; TMEM11 deletion enhances cardiomyocyte proliferation and cardiac repair.\",\n      \"method\": \"Co-immunoprecipitation; m7G methylation assays; ATF5 luciferase reporter; loss-of-function in cardiomyocytes; mouse cardiac injury model\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP binding, m7G target identification, genetic loss-of-function with defined phenotypic pathway, single lab\",\n      \"pmids\": [\"37286744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Mettl1 increases SRSF9 expression by inducing m7G modification of SRSF9 mRNA; elevated SRSF9 facilitates alternative splicing and stabilization of NFATc4, thereby promoting cardiac hypertrophy; Mettl1 knockout alleviates cardiac hypertrophy and SRSF9 knockdown protects against TAC- or Mettl1-induced hypertrophic phenotypes; YY1 acts as a transcription factor for Mettl1 during cardiac hypertrophy.\",\n      \"method\": \"m7G MeRIP-seq; alternative splicing analysis; cardiac-specific Mettl1 KO and overexpression mouse models; SRSF9 KD in vivo and in vitro; ChIP for YY1\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m7G target identification, genetic models in vivo, splicing mechanistic follow-up, single lab\",\n      \"pmids\": [\"38810124\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 knockdown leads to decreased m7G modification on tRNAs, destabilization of tRNAs, and facilitation of tsRNA (tRNA-derived small RNA) biogenesis in AML cells; loss of m7G tRNAs decreases global translation efficiency; transfection of tRNAs isolated from METTL1-KD cells is sufficient to decrease global translation.\",\n      \"method\": \"Northern blotting; LC-MS/MS m7G quantification; tRNA stability analysis; small ncRNA sequencing; quantitative proteomics; nascent protein synthesis measurement\",\n      \"journal\": \"Experimental hematology & oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (LC-MS/MS, tRNA stability, proteomics), single lab\",\n      \"pmids\": [\"38268051\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 loss causes tRNA m7G reduction, ribosome stalling at specific codons decoded by m7G-tRNAs, reduced translation efficiency of spermatogenesis genes, and abolishes elongated spermatid and mature sperm production in Drosophila; catalytic-dead Mettl1 transgene cannot rescue, demonstrating the requirement for m7G catalytic activity; m7G modification-dependent tRNA abundance differs between gonadal and non-gonadal tissues.\",\n      \"method\": \"Mettl1 knockout Drosophila; ribosome profiling; tRNA m7G modification profiling; germ cell-specific transgenic rescue; catalytic-dead allele comparison\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — genetic knockout with catalytic dead rescue in vivo, ribosome profiling, multiple orthogonal approaches\",\n      \"pmids\": [\"39317727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Perturbation of METTL1-WDR4-mediated m7G46 tRNA methylation decreases tRNA abundance via the rapid tRNA decay (RTD) pathway, causes ribosome stalling at m7G-tRNA-decoded codons, impedes translation of Wnt signaling and ribosome biogenesis mRNAs, and triggers the ribotoxic and integrative stress responses inducing senescence-associated secretory phenotype; restoring eEF1A protein mitigates senescence from METTL1 deficiency by reducing RTD.\",\n      \"method\": \"METTL1 KD in senescence models; ribosome profiling; tRNA stability assays; RTD pathway analysis; eEF1A rescue experiments; Mettl1/Wdr4 aging measurements\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ribosome profiling, genetic rescue experiments, multiple mechanistic pathways validated, replicated in multiple models\",\n      \"pmids\": [\"38977661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 promotes tRNA aminoacylation and polysome formation independent of its methyltransferase activity by binding the multi-tRNA synthetase complex; phosphomimetic (S27D) and catalytically dead METTL1 alleles phenocopy wild-type METTL1 oncogenic activity in a zebrafish liposarcoma model; METTL1-amplified liposarcomas are hypersensitive to actinomycin D.\",\n      \"method\": \"Zebrafish liposarcoma model; overexpression of phosphomimetic and catalytic-dead alleles; co-IP with multi-tRNA synthetase complex; polysome profiling; aminoacylation assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — binding partner identified by Co-IP, functional allele comparison, polysome/aminoacylation assays, in vivo genetic model\",\n      \"pmids\": [\"39892392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Mettl1 regulates postnatal cardiac metabolic reprogramming primarily through translational control of the rate-limiting ketogenesis enzyme Hmgcs2; loss of Mettl1 causes aberrant metabolic reprogramming and cardiomyocyte immaturity leading to heart failure; β-hydroxybutyrate supplementation partially rescues clinical features.\",\n      \"method\": \"Mettl1 cardiac-specific knockout mice; multi-omics (proteomics + translatomics); polysome profiling; β-hydroxybutyrate rescue; β-hydroxybutyrylation (histone modification) analysis\",\n      \"journal\": \"Nature cardiovascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model with multi-omics mechanistic follow-up and metabolite rescue, single lab\",\n      \"pmids\": [\"39587264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 catalyzes m7G modification of CYLD deubiquitinase mRNA, increasing CYLD expression; elevated CYLD enhances stability of P53 by preventing its ubiquitination and degradation; P53 in turn transcriptionally activates METTL1 forming a positive feedback loop promoting cardiomyocyte apoptosis during ischemia/reperfusion; CYLD knockdown mitigates Mettl1-overexpression-induced apoptosis.\",\n      \"method\": \"RNA sequencing + m7G-methylated RNA sequencing in Mettl1-overexpressing hearts; m7G MeRIP; CYLD KD rescue; P53 ChIP; ubiquitination assays\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m7G target sequencing, genetic epistasis (CYLD KD rescue), P53 ChIP, single lab\",\n      \"pmids\": [\"39414959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"P300 forms a complex with SP1 and binds the METTL1 promoter via SP1, mediating METTL1 transcriptional upregulation in castration-resistant prostate cancer; METTL1 then adds internal m7G modifications to CDK14 mRNA, enhancing its stability and expression to promote CRPC progression.\",\n      \"method\": \"ChIP-qPCR; Co-IP; luciferase reporter assay; m7G AlkAniline-Seq; mRNA degradation assays; transcriptome sequencing\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (ChIP, Co-IP, m7G sequencing, mRNA stability), single lab\",\n      \"pmids\": [\"37599359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL1 enhances TXNDC12 mRNA stability via m7G-dependent mechanism; TXNDC12 in turn stabilizes c-Myc protein by promoting its interaction with USP5, preventing proteasomal degradation of c-Myc in HNSCC.\",\n      \"method\": \"m7G-MeRIP; mRNA stability assays; co-IP (TXNDC12-USP5 interaction); RNA transcriptomic analysis\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited methodological detail in abstract for the METTL1 step specifically\",\n      \"pmids\": [\"40750708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 modulates LSM14A expression via mRNA m7G methylation; LSM14A stabilizes DDX5 in the cytoplasm during G1/S phase, regulating CDK4 and P21 levels in glioblastoma.\",\n      \"method\": \"MeRIP; co-immunoprecipitation; protein half-life assay; mass spectrometry\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, m7G methylation of LSM14A shown but downstream DDX5 stabilization mechanistic link is limited\",\n      \"pmids\": [\"39040050\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL1-mediated m7G modification of Sarm1 mRNA enhances its stability and expression in macrophages; elevated SARM1 induces NAD+ decline and metabolic reprogramming, promoting macrophage proinflammatory responses; METTL1 deficiency in myeloid cells mitigates multiorgan inflammation.\",\n      \"method\": \"m7G-MeRIP-seq; mRNA stability assay; SARM1 rescue experiments; myeloid-specific Mettl1 KO mice; cecal ligation and puncture / ischemia-reperfusion models\",\n      \"journal\": \"Science immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m7G sequencing, genetic rescue, in vivo myeloid-specific KO, single lab\",\n      \"pmids\": [\"40911698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 mediates m7G methylation of PKM mRNA, enhancing PKM2 expression and glycolysis; increased PKM2 dimer nuclear translocation activates CD155 expression causing CRC immune evasion; elevated glycolysis promotes H3K9 lactylation (H3K9la) which activates METTL1 transcription, forming a positive feedback loop.\",\n      \"method\": \"MeRIP assay; RIP; RNA stability analysis; extracellular acidification rate measurement; Cut&Run for H3K9la; METTL1 KO mice with CD155 blockers\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — m7G target validation, multiple mechanistic assays, in vivo KO with functional rescue, single lab\",\n      \"pmids\": [\"39741310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL3-mediated m6A modification of METTL1 mRNA elevates METTL1 expression in HNSCC; METTL1 physically binds the CDK4 transcript and regulates its m7G modification level to stabilize CDK4, promoting cell cycle progression.\",\n      \"method\": \"Database mining (GEPIA); RIP to confirm METTL1-CDK4 mRNA interaction; m7G modification level measurement; CDK4 rescue experiments\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, RIP without rigorous controls, limited mechanistic detail in abstract\",\n      \"pmids\": [\"37694982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"METTL1 knockdown in hiPSC-derived EPCs activates the MAPK/ERK signaling pathway during EPC differentiation, significantly increasing EPC marker expression and functional properties; METTL1-KD EPCs accelerate vascular smooth muscle cell proliferation via co-culture.\",\n      \"method\": \"METTL1 KD hiPSCs; immunofluorescence; FACS; co-culture system; MAPK/ERK pathway analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, pathway activation observed but causal link to m7G not directly established\",\n      \"pmids\": [\"32430183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HIF-1α binds to a hypoxia response element (HRE) in the METTL1 promoter and directly represses METTL1 transcription under hypoxic conditions in CRC cells, leading to decreased m7G tRNA modification.\",\n      \"method\": \"METTL1 promoter activity luciferase assay; HIF-1α siRNA; ChIP assay; LC-MS/MS quantification of RNA modifications\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP, promoter reporter assay, siRNA, and mass spec quantification; single lab\",\n      \"pmids\": [\"38118310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Thyroid hormone receptor (TR) directly activates Mettl1 gene transcription via a T3 response element (TRE) in the promoter; TR binding correlates with increased H3K79 methylation and RNA polymerase II recruitment during Xenopus intestinal metamorphosis.\",\n      \"method\": \"T3-induced Xenopus metamorphosis model; ChIP for TR binding, H3K79me, and Pol II at Mettl1 TRE; promoter activation assay\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct ChIP evidence of TR binding at TRE with histone mark correlation, in vivo developmental model, single lab\",\n      \"pmids\": [\"32391142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1-mediated m7G modification of TEAD2 mRNA enhances its stability via the binding protein Quaking; elevated TEAD2 transcriptionally represses ACADM, impairing mitochondrial function and amplifying proinflammatory responses in kidney tubular epithelial cells during AKI.\",\n      \"method\": \"m7G-methylated RNA immunoprecipitation sequencing; RNA sequencing; TEC-specific Mettl1 conditional KO mice (multiple AKI models); Quaking binding assays\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO in multiple disease models, m7G sequencing, Quaking reader interaction identified, single lab\",\n      \"pmids\": [\"41407011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 promotes METTL1-mediated m7G modification of SRSF9 mRNA and drives METTL1-mediated hepatic regeneration after partial hepatectomy by selectively augmenting translation of Hippo pathway effectors YAP/TAZ via m7G tRNA modification.\",\n      \"method\": \"Multi-omics (proteomics + translatomics); Mettl1 KO mice; ectopic Mettl1 expression; 70% PHx murine model; polysome profiling\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model, multi-omics mechanistic link to YAP/TAZ translation, single lab\",\n      \"pmids\": [\"41360736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 loss reduces m7G modification on tRNAPheGAA specifically, decreasing its steady-state levels and causing translation suppression/degradation of mRNAs enriched in corresponding codons including HCK tyrosine kinase; decreased HCK disrupts CXCR4 signaling, impairing leukemia stem cell self-renewal and bone marrow homing; pharmacological METTL1 inhibition (NSC137443) recapitulates these effects.\",\n      \"method\": \"tRNA m7G profiling; translation/proteomics profiling; CXCR4 signaling assays; AML mouse models; high-throughput screening for small-molecule inhibitor\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific tRNA target identified, mechanistic cascade validated, pharmacological inhibitor confirmation, single lab\",\n      \"pmids\": [\"42247311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL1 interacts with XPO5 (exportin-5) as identified by APEX2 proximity labeling; METTL1 deletion causes XPO5 redistribution to the cytosol, accelerating pre-miRNA export and enhancing miRNA maturation independent of METTL1 m7G methyltransferase activity; mechanistically METTL1 facilitates ERK-mediated phosphorylation of XPO5 to promote its nuclear retention.\",\n      \"method\": \"APEX2 proximity labeling + LC-MS/MS; co-immunoprecipitation; western blot; METTL1 knockout; ERK pathway manipulation; constitutively active ERK rescue\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity labeling interactome, Co-IP validation, genetic KO phenotype with ERK rescue, single lab\",\n      \"pmids\": [\"41591839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL1 mediates m7G modification of B-cell tRNAs to preferentially translate BCR signaling-related proteins and maintain mitochondrial electron transport chain activity; conditional Mettl1 knockout in B cells blocks germinal center entry and GC formation; conditional knock-in promotes GC responses; METTL1-mediated tRNA m7G controls B-cell autoreactivity in SLE.\",\n      \"method\": \"B cell-specific Mettl1 conditional KO and knock-in mice; m7G tRNA profiling; translation profiling; mitochondrial function assays; lupus-prone mouse model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO and knock-in genetic models, tRNA and translation profiling, mitochondrial functional assays, disease model validation\",\n      \"pmids\": [\"39638793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In oesophageal cancer cells resistant to METTL1 loss, tRNA balance is preserved upon m7G46 deficiency by compensatory elevation of dihydrouridylation at position 47 (D47) by DUS3L; depletion of DUS-L enzymes sensitises resistant cells to METTL1 loss; concomitant loss of both modifications destabilizes canonical tRNA L-shape and disrupts coaxial helix stacking and anticodon-loop presentation.\",\n      \"method\": \"METTL1 depletion in resistant vs sensitive cell lines; DUS3L/DUS-L depletion; tRNA structural analysis; fitness/proliferation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis, tRNA structural analysis, functional assays; preprint not yet peer reviewed\",\n      \"pmids\": [\"41279591\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL1 depletion in Mettl1-specific mesenchymal stem cells disrupts m7G modification of Fgfr2 mRNA, reducing its stability; Fgfr2 downregulation impairs PI3K-AKT and MAPK signaling pathways, decreases Sp1 phosphorylation and promotes its ubiquitin-mediated degradation, ultimately reducing Col1a1 and Col2a1 transcription and blocking osteoblast/chondrocyte differentiation; pharmacological Fgfr2 reactivation rescues the bone defects.\",\n      \"method\": \"Mettl1 conditional KO in mesenchymal lineage; m7G-MeRIP sequencing; single-cell RNA sequencing; Fgfr2 mRNA stability assay; Sp1 ubiquitination assay; pharmacological rescue\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with m7G-MeRIP and scRNA-seq mechanistic follow-up, pharmacological rescue, single lab\",\n      \"pmids\": [\"41079929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NSUN5 (m5C methyltransferase) directly binds the METTL1 transcript and facilitates its m5C modification, positively regulating METTL1 expression; overexpression of METTL1 counteracts tumor-suppressive effects of NSUN5 ablation in esophageal cancer.\",\n      \"method\": \"RNA co-immunoprecipitation; RNA pull-down; NSUN5 KD with METTL1 rescue experiments; xenograft models\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, RIP/pull-down interaction, limited mechanistic detail about m5C modification functional consequence\",\n      \"pmids\": [\"39601515\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"METTL1 functions as the catalytic subunit of the METTL1-WDR4 heterodimeric complex (structurally characterized by cryo-EM/crystallography) that deposits N7-methylguanosine (m7G) at position 46 in the variable loop of a subset of tRNAs carrying a 'RAGGU' motif, stabilizing tRNA structure and preventing rapid tRNA decay; this modification sustains translational efficiency at the corresponding codons, selectively enhancing synthesis of proteins encoded by mRNAs enriched in those codons (e.g., cell cycle regulators, oncogenes, signaling pathway components); METTL1 activity is regulated by AKT/PKB and RSK phosphorylation at Ser27 in its disordered N-terminal region, which inhibits catalysis; METTL1 additionally methylates internal positions in select mRNAs and miRNA precursors (augmenting let-7 biogenesis by disrupting inhibitory RNA structure), binds the multi-tRNA synthetase complex to promote tRNA aminoacylation independent of its methyltransferase activity, and interacts with XPO5 to regulate pre-miRNA nuclear export via ERK-mediated XPO5 phosphorylation, placing METTL1 at the intersection of tRNA biology, translational control, and RNA processing with broad consequences for cell growth, differentiation, immune function, and disease.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"METTL1 is the catalytic subunit of a heterodimeric tRNA methyltransferase that, with its scaffold partner WDR4, deposits N7-methylguanosine (m7G46) in the variable loop of a defined subset of tRNAs bearing a 'RAGGU' motif, thereby coupling tRNA modification to codon-specific translational control of cell growth, differentiation, and immune function [#3, #5]. Structural work shows the composite METTL1-WDR4 surface recognizes the tRNA elbow through shape complementarity, with the predicted-disordered METTL1 N terminus forming part of the catalytic pocket and acting as an allosteric switch that couples cofactor binding to substrate-induced conformational changes; the active heterodimer must be co-assembled with WDR4 to be catalytically competent [#0, #1, #6]. This activity is regulated by growth-factor signaling: PKB/AKT and RSK phosphorylate METTL1 at Ser27 in the N-terminal region, disrupting the catalytic center and inactivating the enzyme [#1, #2]. m7G modification stabilizes target tRNAs against the rapid tRNA decay pathway and sustains translation; its loss reduces tRNA abundance, drives ribosome stalling at m7G-decoded codons, promotes biogenesis of tRNA-derived small RNAs, and reprograms the translatome, with consequences spanning self-renewal, oncogenic transformation, immune-cell programs, and tissue homeostasis [#3, #5, #16, #18]. Across many tissues METTL1 selectively enhances translation of mRNAs enriched in m7G-tRNA-decoded codons—including cell cycle regulators, PI3K/AKT/mTOR components, and other oncogenic transcripts—and catalytically dead alleles fail to recapitulate these phenotypes, establishing methyltransferase activity as the operative mechanism [#5, #7, #8, #10, #17]. Beyond tRNA, METTL1 catalyzes internal m7G on select mRNAs and on miRNA precursors, augmenting let-7 biogenesis by disrupting an inhibitory secondary structure [#4]. It also exerts methyltransferase-independent functions: it binds the multi-tRNA synthetase complex to promote tRNA aminoacylation and polysome formation, and it interacts with XPO5 to restrain pre-miRNA nuclear export via ERK-mediated XPO5 phosphorylation [#19, #34].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that METTL1 is a growth-factor-regulated enzyme, answering whether its tRNA methyltransferase activity is subject to signaling control.\",\n      \"evidence\": \"In vitro kinase assays, phospho-specific detection with IGF-1 stimulation, and yeast trm8 complementation with phosphomutant alleles\",\n      \"pmids\": [\"15861136\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not resolve the structural basis for how Ser27 phosphorylation inactivates catalysis\",\n        \"Physiological signals beyond IGF-1/PI3K driving Ser27 phosphorylation not mapped\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the substrate requirements and obligate heterodimeric nature of the methyltransferase using the yeast Trm8-Trm82 ortholog, answering how the enzyme recognizes tRNA and assembles.\",\n      \"evidence\": \"Reconstituted in vitro methyltransferase assays with truncated/mutant tRNAs and wheat-germ co-translation\",\n      \"pmids\": [\"17382321\", \"18164779\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Yeast ortholog; human substrate spectrum not yet defined here\",\n        \"Atomic basis of co-translational assembly requirement not resolved\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected m7G tRNA modification to codon-specific translation and cell fate, answering what the modification does functionally in mammalian cells.\",\n      \"evidence\": \"m7G tRNA MeRIP-seq, TRAC-seq, ribosome profiling in Mettl1/Wdr4 knockout mouse ESCs with differentiation assays\",\n      \"pmids\": [\"29983320\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not establish disease relevance\",\n        \"Mechanism linking tRNA loss to decay not yet defined\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended substrate scope beyond tRNA by showing METTL1 m7G-modifies miRNA precursors, answering whether the enzyme acts on other RNA classes.\",\n      \"evidence\": \"BoRed-seq, RNA-IP, mass-spectrometry site mapping, and catalytic-mutant rescue of migration\",\n      \"pmids\": [\"31031083\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Breadth of miRNA targets beyond let-7 not fully enumerated\",\n        \"Interplay between tRNA and miRNA functions not dissected\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established METTL1 as an oncogenic driver acting through codon-biased translation, answering how the enzyme contributes to cancer across tissues.\",\n      \"evidence\": \"m7G tRNA MeRIP-seq, polysome/ribosome profiling, catalytic-dead alleles, and xenograft/in vivo models in liver, lung, and transformation systems\",\n      \"pmids\": [\"34352207\", \"34371184\", \"34898034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific tRNA isoacceptors driving each cancer not uniformly defined\",\n        \"Did not address methyltransferase-independent contributions\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked METTL1-dependent translation to specific oncogenic signaling output and the tumor immune microenvironment, answering which downstream pathways are selectively translated.\",\n      \"evidence\": \"Conditional knockout/knockin mouse HNSCC models with PI3K/AKT/mTOR pathway rescue and scRNA-seq\",\n      \"pmids\": [\"35179319\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism of immune-landscape remodeling not fully resolved at this step\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the structural and allosteric basis of m7G catalysis and its regulation, answering how the complex recognizes substrate and how Ser27 phosphorylation inhibits it.\",\n      \"evidence\": \"Crystal and cryo-EM structures of METTL1-WDR4-tRNA with SAM/SAH, biochemical assays, and mutagenesis of catalytic residues and S27\",\n      \"pmids\": [\"36599982\", \"36599985\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Dynamics of the disordered N terminus in cells not directly observed\",\n        \"Structural basis for non-tRNA substrate recognition not addressed\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed METTL1 loss reroutes translation through tRNA-derived small RNAs to favor tumor-suppressive and immune programs, answering how depletion can be exploited therapeutically.\",\n      \"evidence\": \"m7G tRNA and small-RNA profiling, polysome profiling, and preclinical knockdown plus immunotherapy-response models in prostate cancer\",\n      \"pmids\": [\"37516825\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab; 5'tRF targets not exhaustively mapped\",\n        \"Generalizability across tumor types not established\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified the rapid tRNA decay pathway as the mechanistic link between m7G loss and reduced tRNA abundance, answering why modification loss destabilizes tRNAs and triggers stress responses.\",\n      \"evidence\": \"Ribosome profiling, tRNA stability and RTD assays, and eEF1A rescue in senescence and AML models\",\n      \"pmids\": [\"38977661\", \"38268051\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Quantitative contribution of RTD versus tRF biogenesis not fully partitioned\",\n        \"Tissue-specific decay thresholds undefined\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated in vivo requirement for METTL1 catalytic activity in differentiation and tissue-specific physiology, answering whether m7G activity is essential across developmental and immune contexts.\",\n      \"evidence\": \"Catalytic-dead rescue in Drosophila spermatogenesis, and B-cell conditional KO/knock-in mice with tRNA, translation, and mitochondrial assays\",\n      \"pmids\": [\"39317727\", \"39638793\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Tissue-specific tRNA dependency mechanisms not fully generalized\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Uncovered methyltransferase-independent functions of METTL1, answering whether all of its activity depends on m7G catalysis.\",\n      \"evidence\": \"Zebrafish liposarcoma model with phosphomimetic/catalytic-dead alleles, co-IP with the multi-tRNA synthetase complex, and aminoacylation/polysome assays\",\n      \"pmids\": [\"39892392\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of multi-tRNA synthetase complex binding unknown\",\n        \"Relative weight of catalytic vs non-catalytic roles in human tumors unresolved\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Catalogued METTL1 transcriptional and post-transcriptional regulation, answering how its expression is controlled across disease and developmental states.\",\n      \"evidence\": \"ChIP, promoter reporters, and modification mapping implicating HIF-1\\u03b1 repression, thyroid hormone receptor activation, SP1/P300, YY1, METTL3-m6A, and NSUN5-m5C\",\n      \"pmids\": [\"38118310\", \"32391142\", \"37599359\", \"38810124\", \"37694982\", \"39601515\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Several regulatory links rest on single-lab or low-confidence data\",\n        \"Integration of competing upstream regulators not modeled\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a non-catalytic METTL1-XPO5 axis controlling pre-miRNA export, answering an additional methyltransferase-independent function in RNA processing.\",\n      \"evidence\": \"APEX2 proximity labeling with LC-MS/MS, co-IP, METTL1 knockout, and ERK-pathway manipulation/rescue\",\n      \"pmids\": [\"41591839\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab; reciprocal validation and structural basis of the interaction not established\",\n        \"Physiological consequences of altered miRNA export in vivo unclear\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How METTL1's catalytic and non-catalytic activities are coordinated, and which mRNA versus tRNA substrates dominate in any given physiological or disease context, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No unified model partitioning tRNA-, mRNA-, miRNA-, synthetase-, and XPO5-related functions\",\n        \"Direct mRNA m7G targets often inferred from single-lab studies without orthogonal site mapping\",\n        \"In vivo relevance of Ser27 phosphorylation regulation across tissues not systematically tested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 1, 3, 4, 5, 6, 17]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 3, 6]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [4, 19, 22, 34]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [34]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [19, 34]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [3, 4, 5, 18]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 5, 7, 17, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [5, 7, 8, 10]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [25, 35]}\n    ],\n    \"complexes\": [\n      \"METTL1-WDR4 m7G methyltransferase complex\",\n      \"multi-tRNA synthetase complex (associated)\"\n    ],\n    \"partners\": [\n      \"WDR4\",\n      \"XPO5\",\n      \"TMEM11\",\n      \"QKI\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}