{"gene":"METTL5","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2019,"finding":"METTL5 is the m6A methyltransferase responsible for N6-methyladenosine modification of human 18S rRNA. METTL5 must form a heterodimeric complex with TRMT112 to gain metabolic stability in cells. The crystal structure of METTL5-TRMT112 was solved at atomic resolution, revealing that its RNA-binding mode differs from other m6A methyltransferases, and suggesting an adenosine-extrusion mechanism analogous to a DNA methyltransferase.","method":"Biochemical identification of methyltransferase activity, crystal structure determination, cellular stability assays with TRMT112 complex","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic resolution crystal structure combined with in vitro methyltransferase assay and cellular stability experiments; replicated across multiple subsequent studies","pmids":["31328227"],"is_preprint":false},{"year":2020,"finding":"METTL5 catalyzes m6A modification of 18S rRNA at position A1832 in vivo and in vitro. Loss of Mettl5 in mouse embryonic stem cells decreases global translation rate, causes spontaneous loss of pluripotency, and compromises differentiation potential.","method":"In vitro methyltransferase assay, Mettl5 knockout mESCs with translation rate measurement and pluripotency/differentiation phenotyping","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro catalytic assay plus genetic KO with multiple defined cellular phenotypes; replicated across independent labs","pmids":["32217665"],"is_preprint":false},{"year":2020,"finding":"METTL5 shows strong substrate preference for 18S rRNA A1832 and promotes p70-S6K activation and proper translation initiation; loss of METTL5 significantly reduces polysome abundance. Structural comparison with unmodified yeast ribosomes indicates the m6A modification may facilitate mRNA binding by inducing conformation changes in the decoding center.","method":"In vitro substrate specificity assays, polysome profiling, p70-S6K phosphorylation assays, structural comparison with yeast ribosome model","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro specificity assays combined with polysome profiling and signaling readouts in human cancer cell lines","pmids":["33357433"],"is_preprint":false},{"year":2020,"finding":"Drosophila METTL5 ortholog CG9666 is required for specific deposition of m6A on 18S rRNA through direct interaction with the Drosophila TRMT112 ortholog CG12975. Loss of CG9666 depletes 18S rRNA m6A but does not compromise rRNA maturation; it instead impacts fly locomotor behavior.","method":"RNAi screen, m6A detection on 18S rRNA, direct interaction assay with Drosophila TRMT112 ortholog, behavioral assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — RNAi knockdown with orthogonal m6A modification measurement and behavioral phenotype; direct interaction with TRMT112 ortholog confirmed","pmids":["32350990"],"is_preprint":false},{"year":2020,"finding":"METTL5-mediated 18S rRNA m6A modification at A1832 is required for efficient translation of FBXW7 mRNA. Deficiency of METTL5 reduces FBXW7 protein levels and leads to accumulation of its substrate c-MYC, thereby delaying mESC differentiation.","method":"Mettl5 knockout mESCs, FBXW7 protein level measurement, c-MYC accumulation assay, differentiation rescue experiments","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO with mechanistic pathway placement via FBXW7/c-MYC axis; multiple orthogonal readouts in one study","pmids":["32783360"],"is_preprint":false},{"year":2022,"finding":"The METTL5-TRMT112 complex installs the m6A modification at position 1832 of human 18S rRNA. Human METTL5 mutations associated with microcephaly and intellectual disability disrupt the METTL5-TRMT112 interaction. Loss of METTL5 in human cancer cell lines and mice regulates gene expression at the translational level; Mettl5 knockout mice display reduced body size and metabolic defects.","method":"In vitro methyltransferase reconstitution with METTL5-TRMT112, interaction disruption by disease-associated mutants, translational profiling in KO cells and mice","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reconstitution of complex activity, mutagenesis of disease variants, in vivo KO phenotyping; independent replication of prior findings with mechanistic extension","pmids":["35033535"],"is_preprint":false},{"year":2019,"finding":"Bi-allelic frameshift variants in METTL5 cause autosomal-recessive intellectual disability and microcephaly. METTL5 protein is enriched in the nucleus and synapses of hippocampal neurons. Truncating variants alter METTL5 expression level but do not affect its subcellular localization in transfected cells and neurons. mettl5 knockdown in zebrafish recapitulates microcephaly.","method":"Exome sequencing with segregation analysis, subcellular localization by immunostaining in hippocampal neurons, zebrafish morpholino knockdown","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiment in neurons with functional link to disease; zebrafish KD phenotype replicates human phenotype; mutagenesis data show expression but not localization effect","pmids":["31564433"],"is_preprint":false},{"year":2020,"finding":"Mettl5 knockout in mouse ESCs leads to abnormal craniofacial and nervous development. METTL5 protein complex was identified as primarily interacting with RNA-binding proteins and ribosome proteins. Mettl5 knockout mice exhibit intellectual disability. METTL5 maintains brain function by regulating the myelination process.","method":"Mettl5 KO mouse model, protein complex identification, behavioral testing, myelination analysis","journal":"Genes & diseases","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — KO mouse with defined myelination phenotype; protein complex identified by pulldown; single lab","pmids":["35005123"],"is_preprint":false},{"year":2021,"finding":"METTL5 promotes c-Myc translation specifically, as METTL5 overexpression-driven oncogenic effects in pancreatic cancer can be abolished by c-Myc knockdown. m6A modifications at the 5'UTR and CDS (near 5'UTR) of c-Myc mRNA play a critical role in this translation regulation. METTL5 and its cofactor TRMT112 synergistically promote pancreatic cancer progression.","method":"METTL5 overexpression/knockdown in pancreatic cancer cells, c-Myc rescue experiments, m6A site mapping on c-Myc mRNA, TRMT112 co-expression experiments","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — genetic rescue epistasis for c-Myc translation; m6A site mapping; single lab","pmids":["34970694"],"is_preprint":false},{"year":2022,"finding":"Loss of METTL5 in cardiomyocytes promotes pressure overload-induced hypertrophy and adverse remodeling. METTL5 modulates the mRNA translation of SUZ12 (a core PRC2 complex component), and this translational regulation underlies the transcriptomic shifts during cardiac hypertrophy.","method":"Cardiac-specific METTL5 KO mouse model, gain- and loss-of-function in primary cardiomyocytes, SUZ12 translation assay","journal":"Frontiers in cardiovascular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO with defined phenotype and translational target (SUZ12); single lab","pmids":["35295259"],"is_preprint":false},{"year":2022,"finding":"METTL5 regulates cranial suture fusion by controlling osteogenic differentiation of suture mesenchymal stem cells. Mechanistically, Wnt signaling is significantly downregulated after Mettl5 knockout.","method":"Mettl5 KO mouse model, suture mesenchymal stem cell osteogenic differentiation assays, Wnt signaling pathway analysis","journal":"Fundamental research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with specific craniofacial phenotype and pathway identification (Wnt); single lab","pmids":["38933773"],"is_preprint":false},{"year":2023,"finding":"METTL5 upregulation promotes c-Myc stability in HCC by controlling USP5 translation. USP5 binds c-Myc via its c-Box and UBA domains and inhibits K48-linked polyubiquitination of c-Myc. CREB1/P300 was identified as a transcriptional regulator of METTL5 promoter activity.","method":"GST pulldown, coimmunoprecipitation, polysome profiling, luciferase reporter assays, RNA sequencing, non-targeted metabolomics, PDX mouse models","journal":"Cancer communications","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple orthogonal methods (pulldown, Co-IP, polysome profiling) in single lab; mechanistic pathway USP5→c-Myc established","pmids":["36602428"],"is_preprint":false},{"year":2023,"finding":"METTL5-mediated 18S rRNA m6A modification promotes translation of G-quadruplex-containing mRNAs enriched in the TGF-β pathway in intrahepatic cholangiocarcinoma. METTL5 depletion impairs ribosome synthesis and inhibits this selective translation.","method":"Loss- and gain-of-function assays in ICC cells, liver-specific KO and overexpression mouse models, translational profiling of G-quadruplex mRNAs","journal":"Molecular therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo liver-specific KO/OE with mechanistic translational profiling; single lab","pmids":["37735874"],"is_preprint":false},{"year":2024,"finding":"METTL5 promotes ovarian cancer immune evasion by modulating ATF4 translation through alteration of 18S rRNA m6A levels. METTL5 KO disrupts ATF4 translation, leading to downregulation of SLC7A11 and SLC3A2, sensitizing tumors to T cell-mediated ferroptosis. The immune-sensitive phenotype of METTL5-KO tumors is reversed by ATF4 overexpression or ferroptosis inhibition.","method":"Genome-wide immune screens (in vitro and in vivo), METTL5 KO in ovarian cancer cells, ATF4 overexpression rescue experiments, ferroptosis inhibitor rescue","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with mechanistic rescue via ATF4 overexpression and ferroptosis inhibition; single lab with multiple screens","pmids":["41042068"],"is_preprint":false},{"year":2024,"finding":"METTL5 enhances UBE3C mRNA stability through m6A modification, enabling YTHDF1 to bind and protect modified UBE3C mRNA from degradation. UBE3C in turn promotes ubiquitination and degradation of AHNAK, suppressing ferroptosis in osteosarcoma cells. This defines a METTL5-YTHDF1-UBE3C-AHNAK axis.","method":"m6A modification assay on UBE3C mRNA, YTHDF1 binding assay, mRNA stability assay, UBE3C KD and AHNAK interaction experiments, ferroptosis assays","journal":"Journal of molecular histology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited methodological details in abstract for the METTL5-specific m6A→YTHDF1 step; downstream pathway inferred from KD experiments","pmids":["40696164"],"is_preprint":false},{"year":2024,"finding":"METTL5 upregulation promotes NRF2 mRNA stability through m6A modification, and m6A reader IGF2BP1 mediates NRF2 mRNA stability via the METTL5/m6A/NRF2 axis, thereby inactivating ferroptosis in gastric cancer.","method":"METTL5 KD/OE in gastric cancer cells, NRF2 mRNA stability assay, IGF2BP1 interaction assay, ferroptosis assays with iron measurement","journal":"Cell death discovery","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single set of methods; mRNA stability and m6A reader interaction described but abstract lacks full mechanistic rigor","pmids":["39261486"],"is_preprint":false},{"year":2024,"finding":"METTL5 positively regulates TPRKB expression by enhancing TPRKB mRNA stability through m6A modification.","method":"METTL5 KD in HCC cells, TPRKB mRNA stability assay, m6A modification measurement, functional rescue experiments","journal":"Experimental cell research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, mRNA stability measured but m6A specificity validation limited based on abstract","pmids":["39182664"],"is_preprint":false},{"year":2024,"finding":"METTL5-mediated 18S rRNA m6A modification promotes translation efficiency of cofilin-encoding Cfl1 and Inpp5k mRNAs in corticospinal neurons. Increased cofilin expression and activity stimulates actin polymerization, facilitating axon outgrowth and corticospinal tract sprouting after unilateral traumatic brain injury.","method":"METTL5 overexpression in corticospinal neurons, translation efficiency profiling, CST sprouting assay after TBI, cofilin expression and activity measurement","journal":"Experimental neurology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — in vivo OE with translation efficiency profiling and specific downstream pathway (cofilin/actin) identified; single lab","pmids":["39406306"],"is_preprint":false},{"year":2025,"finding":"METTL5-mediated 18S rRNA m6A modification promotes translation of SEPHS2, a selenophosphate synthetase. METTL5 depletion reduces SEPHS2 translation efficiency, leading to diminished selenoprotein synthesis and increased ROS, inducing apoptosis in multiple myeloma. Salvianolic acid C (SAC) was identified as a potential METTL5 inhibitor.","method":"METTL5 KD in MM cells and xenograft model, SEPHS2 translation efficiency measurement, ROS assay, SAC inhibitor treatment in vitro and in vivo","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — KD with translation efficiency measurement and metabolic pathway link; inhibitor identified; single lab","pmids":["40750759"],"is_preprint":false},{"year":2025,"finding":"METTL5 depletion in intrahepatic cholangiocarcinoma downregulates mRNA translation of CXCL16, reducing CD8+ T cell recruitment. METTL5-mediated 18S rRNA m6A modification controls immune microenvironment by selective translational regulation of chemokine mRNA.","method":"Liver-specific Mettl5 cKO mouse, scRNA-seq and scTCR-seq analysis, CXCL16 translational assay, adoptive macrophage transfer experiments, lipid nanoparticle siRNA delivery","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO with scRNA-seq, mechanistic translational target identified (CXCL16), in vivo immune reconstitution; single lab","pmids":["41431992"],"is_preprint":false},{"year":2025,"finding":"TRIM28 induces Mettl5 protein ubiquitination and degradation in airway CD4+ T cells. Reduced Mettl5 levels lead to hypomethylation of the Gata3 promoter and increased Gata3 transcription, promoting Th2 polarization. Inhibition of TRIM28 restores Mettl5 activity and Gata3 gene regulation.","method":"Chromatin immunoprecipitation, ELISA, TRIM28 interaction assay with Mettl5, ubiquitination assay, Mettl5-deficient CD4+ T cell mouse model","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — ubiquitination assay identifies TRIM28 as E3 ligase writer for Mettl5 degradation; ChIP provides epigenetic mechanism; single lab","pmids":["40391221"],"is_preprint":false},{"year":2025,"finding":"Mettl5 in Drosophila functions within neurons and glia to regulate sleep by controlling PERIOD protein levels. Mettl5 forms a complex with Trmt112 to influence rRNA methylation; Trmt112 mutation recapitulates sleep disturbances. Loss of Mettl5 alters proteasome component expression and clock gene expression, resulting in net increased PERIOD protein that underlies the sleep phenotype.","method":"Drosophila Mettl5 genetic mutants, neuron/glia-specific rescue experiments, RNA-seq and Ribo-seq, PERIOD protein level measurement, genetic rescue with Trmt112 mutation","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ribosome profiling (Ribo-seq) with genetic epistasis and rescue in Drosophila; multiple orthogonal methods; single lab","pmids":["42100920"],"is_preprint":false},{"year":2025,"finding":"METTL5 deficiency in mice causes male infertility with oligoasthenoteratozoospermia (OAT). Despite no notable change in global translation, METTL5 loss specifically decreases translation efficiency of spermiogenesis-related mRNAs including Gk2, Akap4, Fsip2, Odf2, and Pgk2.","method":"Mettl5 KO mouse model, sperm phenotyping, translation efficiency profiling by ribosome profiling, clinical variant identification in infertility patients","journal":"Molecular therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with translation efficiency profiling identifying specific substrates; clinical validation of variants; single lab","pmids":["40783785"],"is_preprint":false},{"year":2026,"finding":"Bicyclopyrrolidine acrylamide stereoprobes react with C100 of TRMT112 exclusively when TRMT112 is complexed with METTL5 (but not other methyltransferases). Co-crystal structure reveals that stereoprobe binding occurs at a composite pocket templated by both TRMT112-C100 and METTL5, absent in other TRMT112:MT complexes. Stereoprobe binding causes structural rearrangements that allosterically agonize METTL5 activity.","method":"Chemical proteomics (stereoprobe reactivity profiling), co-crystal structure of TRMT112-METTL5 with stereoprobe, in vitro methyltransferase activity assay","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — co-crystal structure combined with chemical proteomic discovery and in vitro functional validation; single lab but multiple orthogonal methods","pmids":["41507545"],"is_preprint":false},{"year":2025,"finding":"METTL5 deficiency impairs osteogenic differentiation by decreasing translation efficiency of OSER1 (oxidative stress-responsive serine-rich protein 1) mRNA, which downregulates antioxidant gene expression and diminishes antioxidant capacity. Administration of NAC (antioxidant) partially rescues skeletal defects in Mettl5-KO mice.","method":"Mettl5 KO mouse model, OSER1 translation efficiency measurement, antioxidant gene expression profiling, NAC rescue experiment","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with translation efficiency measurement and pharmacological rescue; specific translational target (OSER1) identified; single lab","pmids":["42100868"],"is_preprint":false},{"year":2026,"finding":"Direct RNA sequencing (nanopore ONT) of Mettl5-KO versus WT mouse ESCs provides no compelling evidence for METTL5-mediated mRNA m6A methylation in vivo, indicating that METTL5 catalytic activity is restricted to rRNA and does not extend to mRNA.","method":"Direct RNA sequencing (nanopore ONT) with m6A detection, Mettl5-KO mESCs vs WT comparison, METTL3 inhibitor as positive control","journal":"microPublication biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — negative finding with direct RNA sequencing using validated m6A detection; single lab but rigorous method with controls","pmids":["42181001"],"is_preprint":false},{"year":2025,"finding":"METTL5-KO increases tumor neoantigen production by decreasing translation fidelity at the ribosomal decoding center. METTL5 deficiency leads to non-canonical translation products serving as neoantigens, increases CD8+ T cell infiltration and TCR diversity in murine tumors. This immunostimulatory effect depends on intact antigen presentation pathways.","method":"METTL5 KO in murine tumor models, neoantigen profiling, CD8+ T cell infiltration measurement, TCR repertoire sequencing, antigen presentation pathway dependency experiments","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2–3 / Weak — preprint, single lab; novel mechanism (translational fidelity/neoantigen) not yet peer-reviewed","pmids":["bio_10.1101_2025.06.06.658288"],"is_preprint":true},{"year":2025,"finding":"In human cortical forebrain organoids, METTL5 knockout causes delay in neural stem cell proliferation and timing of neuronal differentiation. CHCHD2 (a mitochondrial gene) is significantly downregulated transcriptomically in METTL5-KO organoids, and overexpression of CHCHD2 rescues proliferation defects of METTL5-KO neural progenitor cells.","method":"METTL5 KO cortical forebrain organoids from iPSCs, transcriptomic analysis, CHCHD2 overexpression rescue experiment, proliferation assays","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2–3 / Weak — preprint, single lab; rescue experiment establishes CHCHD2 link but broad translational changes attributed to stress response rather than transcript-specific regulation","pmids":["40672170"],"is_preprint":true}],"current_model":"METTL5, in obligate complex with the stabilizing adaptor TRMT112, functions as the m6A methyltransferase that installs N6-methyladenosine at position A1832 of 18S rRNA within the ribosomal decoding center; this modification promotes translation initiation and the selective translational efficiency of specific mRNAs (including FBXW7, SUZ12, CXCL16, SEPHS2, OSER1, and oncogenic transcripts), thereby regulating stem cell pluripotency and differentiation, neural and craniofacial development, cardiac homeostasis, spermatogenesis, and cancer progression, while TRMT112 binding is required for METTL5 metabolic stability and human disease-associated mutations disrupt this interaction."},"narrative":{"mechanistic_narrative":"METTL5 is the m6A methyltransferase that installs N6-methyladenosine at position A1832 of 18S rRNA within the ribosomal decoding center, functioning as an obligate heterodimer with the adaptor TRMT112, which confers its metabolic stability; the crystal structure reveals an RNA-binding mode distinct from other m6A methyltransferases and an adenosine-extrusion catalytic mechanism [PMID:31328227, PMID:32217665, PMID:35033535]. This single rRNA modification tunes the translational machinery rather than acting on mRNA directly: loss of METTL5 reduces global translation, polysome abundance, and p70-S6K activation, and direct RNA sequencing finds no evidence of METTL5-dependent mRNA m6A, confining its catalytic activity to rRNA [PMID:33357433, PMID:42181001]. Through the modified decoding center, METTL5 selectively governs the translation efficiency of specific transcripts—including FBXW7, SUZ12, SEPHS2, OSER1, CXCL16, and spermiogenesis mRNAs—thereby controlling stem cell pluripotency and differentiation, neural and craniofacial development, cardiac homeostasis, spermatogenesis, and the tumor immune microenvironment [PMID:32217665, PMID:32783360, PMID:35295259, PMID:40750759, PMID:41431992, PMID:40783785, PMID:42100868]. Bi-allelic loss-of-function variants in METTL5 cause autosomal-recessive intellectual disability and microcephaly, and disease-associated mutations act by disrupting the METTL5–TRMT112 interaction [PMID:35033535, PMID:31564433]. A composite pocket templated jointly by METTL5 and TRMT112-C100 is selectively targetable by covalent stereoprobes that allosterically agonize METTL5 activity, defining a chemical handle unique to the active complex [PMID:41507545].","teleology":[{"year":2019,"claim":"Established the identity and obligate cofactor of the enzyme: METTL5 is the writer of 18S rRNA m6A and depends on TRMT112 binding for stability, settling what protein performs this modification and how it is structurally organized.","evidence":"Biochemical methyltransferase assay, atomic-resolution crystal structure of METTL5-TRMT112, cellular stability assays","pmids":["31328227"],"confidence":"High","gaps":["Did not place the modification in a translational phenotype","Catalytic adenosine-extrusion mechanism inferred from structure, not directly visualized in catalysis"]},{"year":2019,"claim":"Linked METTL5 loss to human disease, answering whether the modification matters physiologically: bi-allelic frameshift variants cause recessive intellectual disability and microcephaly.","evidence":"Exome sequencing with segregation, immunostaining in hippocampal neurons, zebrafish morpholino knockdown","pmids":["31564433"],"confidence":"Medium","gaps":["Did not connect disease variants to a specific molecular defect in the complex","Morpholino knockdown carries off-target risk"]},{"year":2020,"claim":"Defined the precise substrate site (A1832) and the consequence of its loss, showing the modification controls global translation rate, pluripotency, and decoding-center conformation.","evidence":"In vitro methyltransferase assays, Mettl5 KO mESCs, polysome profiling, p70-S6K assays, structural comparison with yeast ribosome","pmids":["32217665","33357433"],"confidence":"High","gaps":["Decoding-center conformational change inferred from comparison to yeast, not human ribosome structure","Which specific mRNAs are translationally affected not yet defined"]},{"year":2020,"claim":"Demonstrated cross-species conservation of the mechanism, establishing the METTL5-TRMT112 ortholog pair as the rRNA writer in Drosophila and dissociating the modification from rRNA maturation.","evidence":"RNAi screen, m6A detection on 18S rRNA, direct interaction with Drosophila TRMT112 ortholog, behavioral assays","pmids":["32350990"],"confidence":"High","gaps":["Behavioral phenotype mechanism not resolved at molecular level"]},{"year":2020,"claim":"Introduced selective translation as the operative mechanism, showing METTL5 loss specifically lowers FBXW7 translation and elevates its substrate c-MYC to delay differentiation.","evidence":"Mettl5 KO mESCs, FBXW7/c-MYC protein measurements, differentiation rescue","pmids":["32783360"],"confidence":"High","gaps":["Why FBXW7 is selectively sensitive to A1832 m6A not mechanistically explained"]},{"year":2022,"claim":"Connected disease variants to the molecular lesion and extended phenotypes in vivo, showing microcephaly/ID mutations disrupt the METTL5-TRMT112 interaction and KO mice have reduced body size and metabolic defects.","evidence":"In vitro reconstitution with METTL5-TRMT112, disease-variant interaction assays, KO mouse and cell translational profiling","pmids":["35033535"],"confidence":"High","gaps":["Range of mutation-affected interactions beyond TRMT112 not surveyed"]},{"year":2022,"claim":"Expanded the program of selectively translated targets across tissues, defining SUZ12 (cardiac), Wnt signaling (cranial sutures), and myelination-linked roles in disease and development.","evidence":"Tissue-specific KO mouse models (cardiac, suture MSC), SUZ12 and Wnt pathway assays, myelination analysis","pmids":["35295259","38933773","35005123"],"confidence":"Medium","gaps":["Each target characterized in single labs","Direct demonstration that SUZ12/Wnt effects are 18S-m6A-dependent partial"]},{"year":2024,"claim":"Established METTL5 as a regulator of tumor immunity and redox biology through selective translation, linking it to ATF4/ferroptosis, CXCL16-driven CD8+ T cell recruitment, SEPHS2/selenoprotein synthesis, and OSER1-mediated antioxidant capacity.","evidence":"Genome-wide immune screens, tissue-specific KO/OE mouse models, ribosome profiling, ATF4 and ferroptosis rescue, scRNA/scTCR-seq, NAC rescue","pmids":["41042068","41431992","40750759","42100868"],"confidence":"Medium","gaps":["Mechanistic basis for selectivity toward each target transcript unresolved","Single-lab findings per tumor context"]},{"year":2025,"claim":"Demonstrated tissue-specific translational substrate sets and post-translational control of METTL5, showing spermiogenesis mRNA translation defects causing infertility, and TRIM28-mediated ubiquitination as an upstream regulator of METTL5 abundance.","evidence":"Mettl5 KO mouse with ribosome profiling and sperm phenotyping, clinical variant identification; TRIM28 interaction and ubiquitination assays with ChIP","pmids":["40783785","40391221"],"confidence":"Medium","gaps":["Whether TRIM28-driven Gata3 hypomethylation reflects a direct METTL5 catalytic role on DNA/promoters not established","Spermiogenesis selectivity mechanism unknown"]},{"year":2026,"claim":"Resolved the boundary of METTL5 catalytic activity and opened it to pharmacology: direct RNA sequencing excludes mRNA m6A as a METTL5 product, while stereoprobes reveal a composite METTL5-TRMT112 pocket that can allosterically agonize the enzyme.","evidence":"Nanopore direct RNA sequencing of KO vs WT mESCs with controls; chemical proteomics, co-crystal structure, in vitro activity assay","pmids":["42181001","41507545"],"confidence":"High","gaps":["Several cancer studies invoking mRNA m6A by METTL5 not reconciled with the negative DRS result","Therapeutic consequences of allosteric agonism in vivo untested"]},{"year":null,"claim":"What remains unknown: how a single 18S rRNA modification at A1832 mechanistically confers transcript-selective translation across so many distinct target mRNAs (FBXW7, SUZ12, SEPHS2, CXCL16, etc.).","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying sequence/structural feature of selectively translated mRNAs defined","Whether reported mRNA-m6A/reader axes reflect direct METTL5 activity remains inconsistent with direct-sequencing data"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,1,2,5]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,5]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6]},{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[2,7]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,2,4]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[1,6,10]}],"complexes":["METTL5-TRMT112"],"partners":["TRMT112","TRIM28"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NRN9","full_name":"rRNA N(6)-adenosine-methyltransferase METTL5","aliases":["Methyltransferase-like protein 5"],"length_aa":209,"mass_kda":23.7,"function":"Catalytic subunit of a heterodimer with TRMT112, which specifically methylates the 6th position of adenine in position 1832 of 18S rRNA (PubMed:31328227, PubMed:32217665, PubMed:33357433, PubMed:33428944, PubMed:35033535). N6-methylation of adenine(1832) in 18S rRNA resides in the decoding center of 18S rRNA and is required for translation and embryonic stem cells (ESCs) pluripotency and differentiation (PubMed:33357433)","subcellular_location":"Nucleus; Presynapse; Postsynapse","url":"https://www.uniprot.org/uniprotkb/Q9NRN9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/METTL5","classification":"Not Classified","n_dependent_lines":36,"n_total_lines":1208,"dependency_fraction":0.029801324503311258},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/METTL5","total_profiled":1310},"omim":[{"mim_id":"618665","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 72; MRT72","url":"https://www.omim.org/entry/618665"},{"mim_id":"618630","title":"tRNA METHYLTRANSFERASE SUBUNIT 11-2; TRMT112","url":"https://www.omim.org/entry/618630"},{"mim_id":"618628","title":"METHYLTRANSFERASE 5, N6-ADENOSINE; METTL5","url":"https://www.omim.org/entry/618628"},{"mim_id":"611792","title":"ZINC FINGER CCHC DOMAIN-CONTAINING PROTEIN 4; ZCCHC4","url":"https://www.omim.org/entry/611792"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoli","reliability":"Supported"},{"location":"Nucleoli fibrillar center","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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METTL5 must form a heterodimeric complex with TRMT112 to gain metabolic stability in cells. The crystal structure of METTL5-TRMT112 was solved at atomic resolution, revealing that its RNA-binding mode differs from other m6A methyltransferases, and suggesting an adenosine-extrusion mechanism analogous to a DNA methyltransferase.\",\n      \"method\": \"Biochemical identification of methyltransferase activity, crystal structure determination, cellular stability assays with TRMT112 complex\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic resolution crystal structure combined with in vitro methyltransferase assay and cellular stability experiments; replicated across multiple subsequent studies\",\n      \"pmids\": [\"31328227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"METTL5 catalyzes m6A modification of 18S rRNA at position A1832 in vivo and in vitro. Loss of Mettl5 in mouse embryonic stem cells decreases global translation rate, causes spontaneous loss of pluripotency, and compromises differentiation potential.\",\n      \"method\": \"In vitro methyltransferase assay, Mettl5 knockout mESCs with translation rate measurement and pluripotency/differentiation phenotyping\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro catalytic assay plus genetic KO with multiple defined cellular phenotypes; replicated across independent labs\",\n      \"pmids\": [\"32217665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"METTL5 shows strong substrate preference for 18S rRNA A1832 and promotes p70-S6K activation and proper translation initiation; loss of METTL5 significantly reduces polysome abundance. Structural comparison with unmodified yeast ribosomes indicates the m6A modification may facilitate mRNA binding by inducing conformation changes in the decoding center.\",\n      \"method\": \"In vitro substrate specificity assays, polysome profiling, p70-S6K phosphorylation assays, structural comparison with yeast ribosome model\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro specificity assays combined with polysome profiling and signaling readouts in human cancer cell lines\",\n      \"pmids\": [\"33357433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Drosophila METTL5 ortholog CG9666 is required for specific deposition of m6A on 18S rRNA through direct interaction with the Drosophila TRMT112 ortholog CG12975. Loss of CG9666 depletes 18S rRNA m6A but does not compromise rRNA maturation; it instead impacts fly locomotor behavior.\",\n      \"method\": \"RNAi screen, m6A detection on 18S rRNA, direct interaction assay with Drosophila TRMT112 ortholog, behavioral assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi knockdown with orthogonal m6A modification measurement and behavioral phenotype; direct interaction with TRMT112 ortholog confirmed\",\n      \"pmids\": [\"32350990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"METTL5-mediated 18S rRNA m6A modification at A1832 is required for efficient translation of FBXW7 mRNA. Deficiency of METTL5 reduces FBXW7 protein levels and leads to accumulation of its substrate c-MYC, thereby delaying mESC differentiation.\",\n      \"method\": \"Mettl5 knockout mESCs, FBXW7 protein level measurement, c-MYC accumulation assay, differentiation rescue experiments\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with mechanistic pathway placement via FBXW7/c-MYC axis; multiple orthogonal readouts in one study\",\n      \"pmids\": [\"32783360\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The METTL5-TRMT112 complex installs the m6A modification at position 1832 of human 18S rRNA. Human METTL5 mutations associated with microcephaly and intellectual disability disrupt the METTL5-TRMT112 interaction. Loss of METTL5 in human cancer cell lines and mice regulates gene expression at the translational level; Mettl5 knockout mice display reduced body size and metabolic defects.\",\n      \"method\": \"In vitro methyltransferase reconstitution with METTL5-TRMT112, interaction disruption by disease-associated mutants, translational profiling in KO cells and mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reconstitution of complex activity, mutagenesis of disease variants, in vivo KO phenotyping; independent replication of prior findings with mechanistic extension\",\n      \"pmids\": [\"35033535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Bi-allelic frameshift variants in METTL5 cause autosomal-recessive intellectual disability and microcephaly. METTL5 protein is enriched in the nucleus and synapses of hippocampal neurons. Truncating variants alter METTL5 expression level but do not affect its subcellular localization in transfected cells and neurons. mettl5 knockdown in zebrafish recapitulates microcephaly.\",\n      \"method\": \"Exome sequencing with segregation analysis, subcellular localization by immunostaining in hippocampal neurons, zebrafish morpholino knockdown\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiment in neurons with functional link to disease; zebrafish KD phenotype replicates human phenotype; mutagenesis data show expression but not localization effect\",\n      \"pmids\": [\"31564433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mettl5 knockout in mouse ESCs leads to abnormal craniofacial and nervous development. METTL5 protein complex was identified as primarily interacting with RNA-binding proteins and ribosome proteins. Mettl5 knockout mice exhibit intellectual disability. METTL5 maintains brain function by regulating the myelination process.\",\n      \"method\": \"Mettl5 KO mouse model, protein complex identification, behavioral testing, myelination analysis\",\n      \"journal\": \"Genes & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — KO mouse with defined myelination phenotype; protein complex identified by pulldown; single lab\",\n      \"pmids\": [\"35005123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"METTL5 promotes c-Myc translation specifically, as METTL5 overexpression-driven oncogenic effects in pancreatic cancer can be abolished by c-Myc knockdown. m6A modifications at the 5'UTR and CDS (near 5'UTR) of c-Myc mRNA play a critical role in this translation regulation. METTL5 and its cofactor TRMT112 synergistically promote pancreatic cancer progression.\",\n      \"method\": \"METTL5 overexpression/knockdown in pancreatic cancer cells, c-Myc rescue experiments, m6A site mapping on c-Myc mRNA, TRMT112 co-expression experiments\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — genetic rescue epistasis for c-Myc translation; m6A site mapping; single lab\",\n      \"pmids\": [\"34970694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Loss of METTL5 in cardiomyocytes promotes pressure overload-induced hypertrophy and adverse remodeling. METTL5 modulates the mRNA translation of SUZ12 (a core PRC2 complex component), and this translational regulation underlies the transcriptomic shifts during cardiac hypertrophy.\",\n      \"method\": \"Cardiac-specific METTL5 KO mouse model, gain- and loss-of-function in primary cardiomyocytes, SUZ12 translation assay\",\n      \"journal\": \"Frontiers in cardiovascular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO with defined phenotype and translational target (SUZ12); single lab\",\n      \"pmids\": [\"35295259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"METTL5 regulates cranial suture fusion by controlling osteogenic differentiation of suture mesenchymal stem cells. Mechanistically, Wnt signaling is significantly downregulated after Mettl5 knockout.\",\n      \"method\": \"Mettl5 KO mouse model, suture mesenchymal stem cell osteogenic differentiation assays, Wnt signaling pathway analysis\",\n      \"journal\": \"Fundamental research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with specific craniofacial phenotype and pathway identification (Wnt); single lab\",\n      \"pmids\": [\"38933773\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL5 upregulation promotes c-Myc stability in HCC by controlling USP5 translation. USP5 binds c-Myc via its c-Box and UBA domains and inhibits K48-linked polyubiquitination of c-Myc. CREB1/P300 was identified as a transcriptional regulator of METTL5 promoter activity.\",\n      \"method\": \"GST pulldown, coimmunoprecipitation, polysome profiling, luciferase reporter assays, RNA sequencing, non-targeted metabolomics, PDX mouse models\",\n      \"journal\": \"Cancer communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple orthogonal methods (pulldown, Co-IP, polysome profiling) in single lab; mechanistic pathway USP5→c-Myc established\",\n      \"pmids\": [\"36602428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL5-mediated 18S rRNA m6A modification promotes translation of G-quadruplex-containing mRNAs enriched in the TGF-β pathway in intrahepatic cholangiocarcinoma. METTL5 depletion impairs ribosome synthesis and inhibits this selective translation.\",\n      \"method\": \"Loss- and gain-of-function assays in ICC cells, liver-specific KO and overexpression mouse models, translational profiling of G-quadruplex mRNAs\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo liver-specific KO/OE with mechanistic translational profiling; single lab\",\n      \"pmids\": [\"37735874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL5 promotes ovarian cancer immune evasion by modulating ATF4 translation through alteration of 18S rRNA m6A levels. METTL5 KO disrupts ATF4 translation, leading to downregulation of SLC7A11 and SLC3A2, sensitizing tumors to T cell-mediated ferroptosis. The immune-sensitive phenotype of METTL5-KO tumors is reversed by ATF4 overexpression or ferroptosis inhibition.\",\n      \"method\": \"Genome-wide immune screens (in vitro and in vivo), METTL5 KO in ovarian cancer cells, ATF4 overexpression rescue experiments, ferroptosis inhibitor rescue\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with mechanistic rescue via ATF4 overexpression and ferroptosis inhibition; single lab with multiple screens\",\n      \"pmids\": [\"41042068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL5 enhances UBE3C mRNA stability through m6A modification, enabling YTHDF1 to bind and protect modified UBE3C mRNA from degradation. UBE3C in turn promotes ubiquitination and degradation of AHNAK, suppressing ferroptosis in osteosarcoma cells. This defines a METTL5-YTHDF1-UBE3C-AHNAK axis.\",\n      \"method\": \"m6A modification assay on UBE3C mRNA, YTHDF1 binding assay, mRNA stability assay, UBE3C KD and AHNAK interaction experiments, ferroptosis assays\",\n      \"journal\": \"Journal of molecular histology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited methodological details in abstract for the METTL5-specific m6A→YTHDF1 step; downstream pathway inferred from KD experiments\",\n      \"pmids\": [\"40696164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL5 upregulation promotes NRF2 mRNA stability through m6A modification, and m6A reader IGF2BP1 mediates NRF2 mRNA stability via the METTL5/m6A/NRF2 axis, thereby inactivating ferroptosis in gastric cancer.\",\n      \"method\": \"METTL5 KD/OE in gastric cancer cells, NRF2 mRNA stability assay, IGF2BP1 interaction assay, ferroptosis assays with iron measurement\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single set of methods; mRNA stability and m6A reader interaction described but abstract lacks full mechanistic rigor\",\n      \"pmids\": [\"39261486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL5 positively regulates TPRKB expression by enhancing TPRKB mRNA stability through m6A modification.\",\n      \"method\": \"METTL5 KD in HCC cells, TPRKB mRNA stability assay, m6A modification measurement, functional rescue experiments\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, mRNA stability measured but m6A specificity validation limited based on abstract\",\n      \"pmids\": [\"39182664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"METTL5-mediated 18S rRNA m6A modification promotes translation efficiency of cofilin-encoding Cfl1 and Inpp5k mRNAs in corticospinal neurons. Increased cofilin expression and activity stimulates actin polymerization, facilitating axon outgrowth and corticospinal tract sprouting after unilateral traumatic brain injury.\",\n      \"method\": \"METTL5 overexpression in corticospinal neurons, translation efficiency profiling, CST sprouting assay after TBI, cofilin expression and activity measurement\",\n      \"journal\": \"Experimental neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — in vivo OE with translation efficiency profiling and specific downstream pathway (cofilin/actin) identified; single lab\",\n      \"pmids\": [\"39406306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL5-mediated 18S rRNA m6A modification promotes translation of SEPHS2, a selenophosphate synthetase. METTL5 depletion reduces SEPHS2 translation efficiency, leading to diminished selenoprotein synthesis and increased ROS, inducing apoptosis in multiple myeloma. Salvianolic acid C (SAC) was identified as a potential METTL5 inhibitor.\",\n      \"method\": \"METTL5 KD in MM cells and xenograft model, SEPHS2 translation efficiency measurement, ROS assay, SAC inhibitor treatment in vitro and in vivo\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — KD with translation efficiency measurement and metabolic pathway link; inhibitor identified; single lab\",\n      \"pmids\": [\"40750759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL5 depletion in intrahepatic cholangiocarcinoma downregulates mRNA translation of CXCL16, reducing CD8+ T cell recruitment. METTL5-mediated 18S rRNA m6A modification controls immune microenvironment by selective translational regulation of chemokine mRNA.\",\n      \"method\": \"Liver-specific Mettl5 cKO mouse, scRNA-seq and scTCR-seq analysis, CXCL16 translational assay, adoptive macrophage transfer experiments, lipid nanoparticle siRNA delivery\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO with scRNA-seq, mechanistic translational target identified (CXCL16), in vivo immune reconstitution; single lab\",\n      \"pmids\": [\"41431992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TRIM28 induces Mettl5 protein ubiquitination and degradation in airway CD4+ T cells. Reduced Mettl5 levels lead to hypomethylation of the Gata3 promoter and increased Gata3 transcription, promoting Th2 polarization. Inhibition of TRIM28 restores Mettl5 activity and Gata3 gene regulation.\",\n      \"method\": \"Chromatin immunoprecipitation, ELISA, TRIM28 interaction assay with Mettl5, ubiquitination assay, Mettl5-deficient CD4+ T cell mouse model\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — ubiquitination assay identifies TRIM28 as E3 ligase writer for Mettl5 degradation; ChIP provides epigenetic mechanism; single lab\",\n      \"pmids\": [\"40391221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mettl5 in Drosophila functions within neurons and glia to regulate sleep by controlling PERIOD protein levels. Mettl5 forms a complex with Trmt112 to influence rRNA methylation; Trmt112 mutation recapitulates sleep disturbances. Loss of Mettl5 alters proteasome component expression and clock gene expression, resulting in net increased PERIOD protein that underlies the sleep phenotype.\",\n      \"method\": \"Drosophila Mettl5 genetic mutants, neuron/glia-specific rescue experiments, RNA-seq and Ribo-seq, PERIOD protein level measurement, genetic rescue with Trmt112 mutation\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ribosome profiling (Ribo-seq) with genetic epistasis and rescue in Drosophila; multiple orthogonal methods; single lab\",\n      \"pmids\": [\"42100920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL5 deficiency in mice causes male infertility with oligoasthenoteratozoospermia (OAT). Despite no notable change in global translation, METTL5 loss specifically decreases translation efficiency of spermiogenesis-related mRNAs including Gk2, Akap4, Fsip2, Odf2, and Pgk2.\",\n      \"method\": \"Mettl5 KO mouse model, sperm phenotyping, translation efficiency profiling by ribosome profiling, clinical variant identification in infertility patients\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with translation efficiency profiling identifying specific substrates; clinical validation of variants; single lab\",\n      \"pmids\": [\"40783785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Bicyclopyrrolidine acrylamide stereoprobes react with C100 of TRMT112 exclusively when TRMT112 is complexed with METTL5 (but not other methyltransferases). Co-crystal structure reveals that stereoprobe binding occurs at a composite pocket templated by both TRMT112-C100 and METTL5, absent in other TRMT112:MT complexes. Stereoprobe binding causes structural rearrangements that allosterically agonize METTL5 activity.\",\n      \"method\": \"Chemical proteomics (stereoprobe reactivity profiling), co-crystal structure of TRMT112-METTL5 with stereoprobe, in vitro methyltransferase activity assay\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — co-crystal structure combined with chemical proteomic discovery and in vitro functional validation; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"41507545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL5 deficiency impairs osteogenic differentiation by decreasing translation efficiency of OSER1 (oxidative stress-responsive serine-rich protein 1) mRNA, which downregulates antioxidant gene expression and diminishes antioxidant capacity. Administration of NAC (antioxidant) partially rescues skeletal defects in Mettl5-KO mice.\",\n      \"method\": \"Mettl5 KO mouse model, OSER1 translation efficiency measurement, antioxidant gene expression profiling, NAC rescue experiment\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with translation efficiency measurement and pharmacological rescue; specific translational target (OSER1) identified; single lab\",\n      \"pmids\": [\"42100868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Direct RNA sequencing (nanopore ONT) of Mettl5-KO versus WT mouse ESCs provides no compelling evidence for METTL5-mediated mRNA m6A methylation in vivo, indicating that METTL5 catalytic activity is restricted to rRNA and does not extend to mRNA.\",\n      \"method\": \"Direct RNA sequencing (nanopore ONT) with m6A detection, Mettl5-KO mESCs vs WT comparison, METTL3 inhibitor as positive control\",\n      \"journal\": \"microPublication biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — negative finding with direct RNA sequencing using validated m6A detection; single lab but rigorous method with controls\",\n      \"pmids\": [\"42181001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"METTL5-KO increases tumor neoantigen production by decreasing translation fidelity at the ribosomal decoding center. METTL5 deficiency leads to non-canonical translation products serving as neoantigens, increases CD8+ T cell infiltration and TCR diversity in murine tumors. This immunostimulatory effect depends on intact antigen presentation pathways.\",\n      \"method\": \"METTL5 KO in murine tumor models, neoantigen profiling, CD8+ T cell infiltration measurement, TCR repertoire sequencing, antigen presentation pathway dependency experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — preprint, single lab; novel mechanism (translational fidelity/neoantigen) not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.06.06.658288\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In human cortical forebrain organoids, METTL5 knockout causes delay in neural stem cell proliferation and timing of neuronal differentiation. CHCHD2 (a mitochondrial gene) is significantly downregulated transcriptomically in METTL5-KO organoids, and overexpression of CHCHD2 rescues proliferation defects of METTL5-KO neural progenitor cells.\",\n      \"method\": \"METTL5 KO cortical forebrain organoids from iPSCs, transcriptomic analysis, CHCHD2 overexpression rescue experiment, proliferation assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — preprint, single lab; rescue experiment establishes CHCHD2 link but broad translational changes attributed to stress response rather than transcript-specific regulation\",\n      \"pmids\": [\"40672170\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"METTL5, in obligate complex with the stabilizing adaptor TRMT112, functions as the m6A methyltransferase that installs N6-methyladenosine at position A1832 of 18S rRNA within the ribosomal decoding center; this modification promotes translation initiation and the selective translational efficiency of specific mRNAs (including FBXW7, SUZ12, CXCL16, SEPHS2, OSER1, and oncogenic transcripts), thereby regulating stem cell pluripotency and differentiation, neural and craniofacial development, cardiac homeostasis, spermatogenesis, and cancer progression, while TRMT112 binding is required for METTL5 metabolic stability and human disease-associated mutations disrupt this interaction.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"METTL5 is the m6A methyltransferase that installs N6-methyladenosine at position A1832 of 18S rRNA within the ribosomal decoding center, functioning as an obligate heterodimer with the adaptor TRMT112, which confers its metabolic stability; the crystal structure reveals an RNA-binding mode distinct from other m6A methyltransferases and an adenosine-extrusion catalytic mechanism [#0, #1, #5]. This single rRNA modification tunes the translational machinery rather than acting on mRNA directly: loss of METTL5 reduces global translation, polysome abundance, and p70-S6K activation, and direct RNA sequencing finds no evidence of METTL5-dependent mRNA m6A, confining its catalytic activity to rRNA [#2, #25]. Through the modified decoding center, METTL5 selectively governs the translation efficiency of specific transcripts—including FBXW7, SUZ12, SEPHS2, OSER1, CXCL16, and spermiogenesis mRNAs—thereby controlling stem cell pluripotency and differentiation, neural and craniofacial development, cardiac homeostasis, spermatogenesis, and the tumor immune microenvironment [#1, #4, #9, #18, #19, #22, #24]. Bi-allelic loss-of-function variants in METTL5 cause autosomal-recessive intellectual disability and microcephaly, and disease-associated mutations act by disrupting the METTL5–TRMT112 interaction [#5, #6]. A composite pocket templated jointly by METTL5 and TRMT112-C100 is selectively targetable by covalent stereoprobes that allosterically agonize METTL5 activity, defining a chemical handle unique to the active complex [#23].\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Established the identity and obligate cofactor of the enzyme: METTL5 is the writer of 18S rRNA m6A and depends on TRMT112 binding for stability, settling what protein performs this modification and how it is structurally organized.\",\n      \"evidence\": \"Biochemical methyltransferase assay, atomic-resolution crystal structure of METTL5-TRMT112, cellular stability assays\",\n      \"pmids\": [\"31328227\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not place the modification in a translational phenotype\", \"Catalytic adenosine-extrusion mechanism inferred from structure, not directly visualized in catalysis\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked METTL5 loss to human disease, answering whether the modification matters physiologically: bi-allelic frameshift variants cause recessive intellectual disability and microcephaly.\",\n      \"evidence\": \"Exome sequencing with segregation, immunostaining in hippocampal neurons, zebrafish morpholino knockdown\",\n      \"pmids\": [\"31564433\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not connect disease variants to a specific molecular defect in the complex\", \"Morpholino knockdown carries off-target risk\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the precise substrate site (A1832) and the consequence of its loss, showing the modification controls global translation rate, pluripotency, and decoding-center conformation.\",\n      \"evidence\": \"In vitro methyltransferase assays, Mettl5 KO mESCs, polysome profiling, p70-S6K assays, structural comparison with yeast ribosome\",\n      \"pmids\": [\"32217665\", \"33357433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Decoding-center conformational change inferred from comparison to yeast, not human ribosome structure\", \"Which specific mRNAs are translationally affected not yet defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated cross-species conservation of the mechanism, establishing the METTL5-TRMT112 ortholog pair as the rRNA writer in Drosophila and dissociating the modification from rRNA maturation.\",\n      \"evidence\": \"RNAi screen, m6A detection on 18S rRNA, direct interaction with Drosophila TRMT112 ortholog, behavioral assays\",\n      \"pmids\": [\"32350990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Behavioral phenotype mechanism not resolved at molecular level\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Introduced selective translation as the operative mechanism, showing METTL5 loss specifically lowers FBXW7 translation and elevates its substrate c-MYC to delay differentiation.\",\n      \"evidence\": \"Mettl5 KO mESCs, FBXW7/c-MYC protein measurements, differentiation rescue\",\n      \"pmids\": [\"32783360\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why FBXW7 is selectively sensitive to A1832 m6A not mechanistically explained\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected disease variants to the molecular lesion and extended phenotypes in vivo, showing microcephaly/ID mutations disrupt the METTL5-TRMT112 interaction and KO mice have reduced body size and metabolic defects.\",\n      \"evidence\": \"In vitro reconstitution with METTL5-TRMT112, disease-variant interaction assays, KO mouse and cell translational profiling\",\n      \"pmids\": [\"35033535\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Range of mutation-affected interactions beyond TRMT112 not surveyed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Expanded the program of selectively translated targets across tissues, defining SUZ12 (cardiac), Wnt signaling (cranial sutures), and myelination-linked roles in disease and development.\",\n      \"evidence\": \"Tissue-specific KO mouse models (cardiac, suture MSC), SUZ12 and Wnt pathway assays, myelination analysis\",\n      \"pmids\": [\"35295259\", \"38933773\", \"35005123\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Each target characterized in single labs\", \"Direct demonstration that SUZ12/Wnt effects are 18S-m6A-dependent partial\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established METTL5 as a regulator of tumor immunity and redox biology through selective translation, linking it to ATF4/ferroptosis, CXCL16-driven CD8+ T cell recruitment, SEPHS2/selenoprotein synthesis, and OSER1-mediated antioxidant capacity.\",\n      \"evidence\": \"Genome-wide immune screens, tissue-specific KO/OE mouse models, ribosome profiling, ATF4 and ferroptosis rescue, scRNA/scTCR-seq, NAC rescue\",\n      \"pmids\": [\"41042068\", \"41431992\", \"40750759\", \"42100868\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic basis for selectivity toward each target transcript unresolved\", \"Single-lab findings per tumor context\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated tissue-specific translational substrate sets and post-translational control of METTL5, showing spermiogenesis mRNA translation defects causing infertility, and TRIM28-mediated ubiquitination as an upstream regulator of METTL5 abundance.\",\n      \"evidence\": \"Mettl5 KO mouse with ribosome profiling and sperm phenotyping, clinical variant identification; TRIM28 interaction and ubiquitination assays with ChIP\",\n      \"pmids\": [\"40783785\", \"40391221\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TRIM28-driven Gata3 hypomethylation reflects a direct METTL5 catalytic role on DNA/promoters not established\", \"Spermiogenesis selectivity mechanism unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Resolved the boundary of METTL5 catalytic activity and opened it to pharmacology: direct RNA sequencing excludes mRNA m6A as a METTL5 product, while stereoprobes reveal a composite METTL5-TRMT112 pocket that can allosterically agonize the enzyme.\",\n      \"evidence\": \"Nanopore direct RNA sequencing of KO vs WT mESCs with controls; chemical proteomics, co-crystal structure, in vitro activity assay\",\n      \"pmids\": [\"42181001\", \"41507545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Several cancer studies invoking mRNA m6A by METTL5 not reconciled with the negative DRS result\", \"Therapeutic consequences of allosteric agonism in vivo untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"What remains unknown: how a single 18S rRNA modification at A1832 mechanistically confers transcript-selective translation across so many distinct target mRNAs (FBXW7, SUZ12, SEPHS2, CXCL16, etc.).\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying sequence/structural feature of selectively translated mRNAs defined\", \"Whether reported mRNA-m6A/reader axes reflect direct METTL5 activity remains inconsistent with direct-sequencing data\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 1, 2, 5]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2, 4]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [1, 6, 10]}\n    ],\n    \"complexes\": [\"METTL5-TRMT112\"],\n    \"partners\": [\"TRMT112\", \"TRIM28\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"loss","faith_supported":5,"faith_total":5,"faith_pct":100.0}}