{"gene":"MBTD1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2009,"finding":"Crystal structure of MBTD1 (residues 130–566, covering 4 MBT repeats) was solved at 2.5 Å resolution by X-ray crystallography, revealing an asymmetric rhomboid architecture similar to L3MBTL2. Fluorescence polarization experiments confirmed that MBTD1 preferentially binds mono- and di-methylated lysine histone peptides through a semi-aromatic cage in one of its four MBT repeats, using a 'cavity insertion recognition mode'.","method":"X-ray crystallography + fluorescence polarization + mutagenesis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure at 2.5 Å combined with fluorescence polarization binding assays and mutagenesis in a single rigorous study","pmids":["19841675"],"is_preprint":false},{"year":2013,"finding":"MBTD1 associates with the histone methyltransferase Pr-Set7 (SET8/KMT5A) in mouse oocytes, as demonstrated by co-immunoprecipitation. Depletion of MBTD1 reduced Pr-Set7 levels and H4K20me1, caused GV-stage arrest, increased γH2AX foci, downregulated 53BP1, activated Chk1, and downregulated cyclin B1 and Cdc2, phenocopying Pr-Set7 depletion. This places MBTD1 upstream of Pr-Set7/H4K20me1 maintenance during meiotic maturation.","method":"Co-immunoprecipitation, siRNA knockdown, immunofluorescence, Western blot in mouse oocytes","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal phenotypic rescue and Co-IP from a single lab with multiple orthogonal readouts","pmids":["23475131"],"is_preprint":false},{"year":2020,"finding":"Crystal structure of the MBTD1–EPC1 complex revealed that a hydrophobic C-terminal fragment of EPC1 engages the MBT repeats of MBTD1 at a site distinct from the H4K20me-binding site, providing the structural basis for recruitment of MBTD1 into the NuA4/TIP60 acetyltransferase complex. Cellular assays validated the physiological significance of key interface residues.","method":"X-ray crystallography of MBTD1–EPC1 complex + cellular validation assays (mutagenesis of interface residues)","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of binary complex combined with mutagenesis and cellular validation in one rigorous study","pmids":["32209463"],"is_preprint":false},{"year":2020,"finding":"NuA4/TIP60 complex, through MBTD1 reading H4K20me and acetylation of H2AK15, inhibits 53BP1 binding to chromatin at DNA breaks by blocking the ubiquitination mark required for 53BP1 localization, thereby influencing DNA repair pathway choice.","method":"Biochemical and cellular assays reported in the context of the structural study","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic model supported by cellular assays in a single rigorous structural paper, but described concisely in the abstract","pmids":["32209463"],"is_preprint":false},{"year":2021,"finding":"The oncogenic ZMYND11-MBTD1 (ZM) fusion protein recruits the NuA4/TIP60 histone acetyltransferase complex to cis-regulatory elements of pro-leukemic genes (Hoxa, Meis1, Myb, Myc, Sox4), sustaining active chromatin enriched in histone acetylation. Systematic mutagenesis demonstrated that Tip60 interaction (mediated through the MBTD1 portion) and an H3K36me3-binding PWWP domain (from ZMYND11) are both essential for oncogenesis. ZM confers indefinite self-renewal on murine hematopoietic stem/progenitor cells ex vivo and causes AML in vivo.","method":"Genomics profiling (ChIP-seq, ATAC-seq), systematic mutagenesis, ex vivo and in vivo murine AML models, inhibitor studies","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genomic and functional methods, in vivo model, mutagenesis dissecting domains, single lab but comprehensive","pmids":["33594072"],"is_preprint":false},{"year":2022,"finding":"ZMYND11-MBTD1 is stably incorporated into the endogenous NuA4/TIP60 complex (biochemically confirmed), and this fusion mislocalizes the complex to the bodies of genes normally bound by ZMYND11, correlating with increased chromatin acetylation, altered transcription of specific genes including MYC, and alternative splicing. Expression of ZMYND11-MBTD1 favors Myc-driven pluripotency during ES cell differentiation and promotes hematopoietic stem/progenitor self-renewal.","method":"Biochemical co-purification/MS, ChIP-seq, RNA-seq, ES cell differentiation assays, hematopoietic progenitor self-renewal assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical incorporation into endogenous complex confirmed by MS, multiple genomic and functional assays, replicates and extends prior findings","pmids":["35705031"],"is_preprint":false},{"year":2023,"finding":"MBTD1 directly binds to the promoter region of FoxO3a (a forkhead protein essential for HSC quiescence) and interacts with components of the TIP60 chromatin remodeling complex. Conditional knockout of Mbtd1 in adult mice caused increased HSC and progenitor numbers, hyperactive cell cycle, and defective stress response; restoration of FOXO3a activity rescued these abnormalities, placing MBTD1 upstream of FOXO3a in HSC quiescence maintenance.","method":"Conditional knockout mice, ChIP (MBTD1 binding to FoxO3a promoter), Co-IP (interaction with TIP60 components), genetic rescue (FOXO3a restoration in vivo)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO in vivo, direct promoter binding by ChIP, Co-IP with complex components, and genetic rescue with multiple readouts","pmids":["37523546"],"is_preprint":false},{"year":2022,"finding":"The transcription factor NFYB binds to the MBTD1 promoter to activate MBTD1 transcription (validated by luciferase reporter and ChIP-qPCR). The lncRNA H19 recruits NFYB to the MBTD1 promoter, increasing MBTD1 expression without altering NFYB protein levels, thereby promoting doxorubicin resistance in lymphoma cells.","method":"Luciferase reporter assay, ChIP-qPCR, siRNA knockdown, in vitro and in vivo lymphoma models","journal":"Molecular biotechnology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — ChIP-qPCR and luciferase reporter support NFYB-mediated MBTD1 transcriptional activation; single lab, focused on upstream regulation of MBTD1 expression","pmids":["36434485"],"is_preprint":false}],"current_model":"MBTD1 is a Polycomb-group nuclear protein containing four MBT repeats that form an asymmetric rhomboid structure capable of binding mono- and di-methylated lysine histone peptides (particularly H4K20me1/2) through a semi-aromatic cage; it is recruited into the NuA4/TIP60 histone acetyltransferase complex via a direct interaction between its MBT repeats and the C-terminal hydrophobic fragment of EPC1, where it acts as an H4K20me reader to direct TIP60-mediated H2AK15 acetylation that blocks 53BP1 chromatin binding and influences DNA repair pathway choice; in hematopoietic stem cells MBTD1 binds the FoxO3a promoter and interacts with TIP60 complex components to maintain HSC quiescence, and the oncogenic ZMYND11-MBTD1 fusion aberrantly mislocalizes the NuA4/TIP60 complex to gene bodies via the ZMYND11 H3K36me3-reading PWWP domain, driving histone acetylation and transcriptional activation of pro-leukemic genes including MYC and HOXA clusters to cause AML."},"narrative":{"mechanistic_narrative":"MBTD1 is a Polycomb-group nuclear protein that functions as a methyl-lysine histone reader and serves as a recruitment module for the NuA4/TIP60 histone acetyltransferase complex, governing DNA repair pathway choice and hematopoietic stem cell quiescence [PMID:19841675, PMID:32209463, PMID:37523546]. Its four MBT repeats form an asymmetric rhomboid architecture in which a semi-aromatic cage in one repeat preferentially engages mono- and di-methylated lysine histone peptides via a cavity-insertion recognition mode [PMID:19841675]. A hydrophobic C-terminal fragment of EPC1 binds the MBT repeats at a site distinct from the methyl-lysine pocket, structurally explaining how MBTD1 is incorporated into the NuA4/TIP60 complex [PMID:32209463]; within this complex MBTD1 reads H4K20me to direct TIP60-mediated H2AK15 acetylation, which blocks 53BP1 chromatin loading and thereby influences DNA double-strand break repair [PMID:32209463]. In hematopoietic stem cells MBTD1 binds the FoxO3a promoter and associates with TIP60 complex components, acting upstream of FOXO3a to enforce quiescence, since its loss expands stem/progenitor pools and hyperactivates the cell cycle while FOXO3a restoration rescues the defect [PMID:37523546]. The oncogenic ZMYND11-MBTD1 fusion mislocalizes the NuA4/TIP60 complex—via MBTD1-mediated TIP60 binding and the ZMYND11 H3K36me3-reading PWWP domain—to the bodies and regulatory elements of pro-leukemic genes including MYC and HOXA clusters, sustaining aberrant histone acetylation and transcriptional activation that drives acute myeloid leukemia [PMID:33594072, PMID:35705031].","teleology":[{"year":2009,"claim":"Established the structural and biochemical basis for MBTD1 as a methyl-lysine reader, defining how it recognizes histone marks.","evidence":"X-ray crystallography of the four MBT repeats with fluorescence polarization binding and mutagenesis","pmids":["19841675"],"confidence":"High","gaps":["Did not identify the in vivo histone substrate or genomic targets","No functional role demonstrated at this stage"]},{"year":2013,"claim":"Linked MBTD1 to maintenance of the H4K20me1 mark by placing it upstream of the methyltransferase Pr-Set7/SET8 during meiotic maturation.","evidence":"Co-IP, siRNA knockdown, and phenocopy analysis in mouse oocytes","pmids":["23475131"],"confidence":"Medium","gaps":["Mechanism by which MBTD1 stabilizes Pr-Set7 unresolved","Single-lab study in a specialized cell type","Direct enzymatic relationship not reconstituted"]},{"year":2020,"claim":"Defined the molecular interface that recruits MBTD1 into the NuA4/TIP60 complex and connected this to DNA repair pathway choice via H2AK15 acetylation and 53BP1 exclusion.","evidence":"Crystal structure of the MBTD1–EPC1 complex with cellular validation and break-repair assays","pmids":["32209463"],"confidence":"High","gaps":["53BP1 exclusion model described concisely and rests on cellular assays in one paper","Quantitative contribution of MBTD1 to repair outcomes not fully mapped"]},{"year":2021,"claim":"Demonstrated that the ZMYND11-MBTD1 fusion is oncogenic, requiring both TIP60 interaction through MBTD1 and the ZMYND11 PWWP domain to redirect the complex to pro-leukemic genes.","evidence":"ChIP-seq, ATAC-seq, systematic domain mutagenesis, and ex vivo/in vivo murine AML models","pmids":["33594072"],"confidence":"High","gaps":["Single-lab study despite comprehensive methods","Therapeutic targetability of the fusion not established"]},{"year":2022,"claim":"Confirmed biochemical incorporation of the fusion into the endogenous NuA4/TIP60 complex and showed it mislocalizes the complex to gene bodies, altering transcription and splicing to favor Myc-driven self-renewal.","evidence":"Co-purification/MS, ChIP-seq, RNA-seq, and ES cell and hematopoietic self-renewal assays","pmids":["35705031"],"confidence":"High","gaps":["Mechanistic link between mislocalization and alternative splicing not detailed","Relative roles of MYC versus other targets in leukemogenesis unresolved"]},{"year":2022,"claim":"Identified upstream transcriptional regulation of MBTD1, with NFYB activating its promoter and lncRNA H19 enhancing this to promote chemoresistance.","evidence":"Luciferase reporter, ChIP-qPCR, siRNA knockdown, and lymphoma models","pmids":["36434485"],"confidence":"Medium","gaps":["Single-lab study focused on expression regulation rather than MBTD1 mechanism","Whether chemoresistance depends on MBTD1 reader/complex functions untested"]},{"year":2023,"claim":"Established a physiological role for MBTD1 in HSC quiescence by placing it upstream of FOXO3a through direct promoter binding and TIP60 complex association.","evidence":"Conditional knockout mice, ChIP at the FoxO3a promoter, Co-IP, and genetic rescue with FOXO3a restoration","pmids":["37523546"],"confidence":"High","gaps":["How MBTD1 activates FoxO3a transcription mechanistically not defined","Connection between HSC quiescence role and the DNA-repair reader function not integrated"]},{"year":null,"claim":"How MBTD1's methyl-lysine reading, repair-pathway control, and transcriptional/HSC functions are mechanistically unified, and whether the ZMYND11-MBTD1 fusion is therapeutically targetable, remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No integrated model linking H4K20me reading to FoxO3a regulation","No structural data on MBTD1 within the assembled NuA4/TIP60 complex","Druggability of the fusion or MBTD1–EPC1 interface untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[0,3]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[6]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,5,6]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,3]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,6]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[3]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[3,4,5]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,5,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,5]}],"complexes":["NuA4/TIP60 histone acetyltransferase complex"],"partners":["EPC1","TIP60","ZMYND11","PR-SET7/SET8/KMT5A","NFYB"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q05BQ5","full_name":"MBT domain-containing protein 1","aliases":[],"length_aa":628,"mass_kda":70.5,"function":"Chromatin reader component of the NuA4 histone acetyltransferase complex, a multiprotein complex involved in transcriptional activation of select genes principally by acetylation of nucleosomal histones H4 and H2A (PubMed:27153538, PubMed:32209463). The NuA4 complex plays a direct role in repair of DNA double-strand breaks (DSBs) by promoting homologous recombination (HR) (PubMed:27153538). MBTD1 specifically recognizes and binds monomethylated and dimethylated 'Lys-20' on histone H4 (H4K20me1 and H4K20me2, respectively) (PubMed:19841675, PubMed:27153538, PubMed:32209463). In the NuA4 complex, MBTD1 promotes recruitment of the complex to H4K20me marks by competing with TP53BP1 for binding to H4K20me (PubMed:27153538). Following recruitment to H4K20me at DNA breaks, the NuA4 complex catalyzes acetylation of 'Lys-15' on histone H2A (H2AK15), blocking the ubiquitination mark required for TP53BP1 localization at DNA breaks, thereby promoting homologous recombination (HR) (PubMed:27153538)","subcellular_location":"Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q05BQ5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MBTD1","classification":"Not Classified","n_dependent_lines":296,"n_total_lines":1208,"dependency_fraction":0.24503311258278146},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MBTD1","total_profiled":1310},"omim":[{"mim_id":"618705","title":"MBT DOMAIN-CONTAINING PROTEIN 1; MBTD1","url":"https://www.omim.org/entry/618705"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MBTD1"},"hgnc":{"alias_symbol":["SA49P01","FLJ20055"],"prev_symbol":[]},"alphafold":{"accession":"Q05BQ5","domains":[{"cath_id":"2.30.30.140","chopping":"172-269","consensus_level":"medium","plddt":95.0747,"start":172,"end":269},{"cath_id":"2.30.30.140","chopping":"283-369","consensus_level":"medium","plddt":90.9862,"start":283,"end":369},{"cath_id":"2.30.30.140","chopping":"387-481","consensus_level":"high","plddt":95.4114,"start":387,"end":481},{"cath_id":"2.30.30.140","chopping":"495-557","consensus_level":"medium","plddt":97.083,"start":495,"end":557}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05BQ5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q05BQ5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q05BQ5-F1-predicted_aligned_error_v6.png","plddt_mean":79.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MBTD1","jax_strain_url":"https://www.jax.org/strain/search?query=MBTD1"},"sequence":{"accession":"Q05BQ5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q05BQ5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q05BQ5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05BQ5"}},"corpus_meta":[{"pmid":"31600142","id":"PMC_31600142","title":"LncRNA TTN-AS1 regulates osteosarcoma cell apoptosis and drug resistance via the miR-134-5p/MBTD1 axis.","date":"2019","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/31600142","citation_count":112,"is_preprint":false},{"pmid":"23959973","id":"PMC_23959973","title":"Identification of a novel, recurrent MBTD1-CXorf67 fusion in low-grade endometrial stromal sarcoma.","date":"2013","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/23959973","citation_count":97,"is_preprint":false},{"pmid":"19841675","id":"PMC_19841675","title":"Structural studies of a four-MBT repeat protein MBTD1.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19841675","citation_count":46,"is_preprint":false},{"pmid":"33594072","id":"PMC_33594072","title":"ZMYND11-MBTD1 induces leukemogenesis through hijacking NuA4/TIP60 acetyltransferase complex and a PWWP-mediated chromatin association mechanism.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/33594072","citation_count":36,"is_preprint":false},{"pmid":"23475131","id":"PMC_23475131","title":"MBTD1 is associated with Pr-Set7 to stabilize H4K20me1 in mouse oocyte meiotic maturation.","date":"2013","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/23475131","citation_count":27,"is_preprint":false},{"pmid":"32237188","id":"PMC_32237188","title":"A novel MBTD1-PHF1 gene fusion in endometrial stromal sarcoma: A case report and literature review.","date":"2020","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/32237188","citation_count":25,"is_preprint":false},{"pmid":"32209463","id":"PMC_32209463","title":"Structural Basis for EPC1-Mediated Recruitment of MBTD1 into the NuA4/TIP60 Acetyltransferase Complex.","date":"2020","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/32209463","citation_count":20,"is_preprint":false},{"pmid":"26608508","id":"PMC_26608508","title":"Recurrent translocation t(10;17)(p15;q21) in minimally differentiated acute myeloid leukemia results in ZMYND11/MBTD1 fusion.","date":"2015","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26608508","citation_count":19,"is_preprint":false},{"pmid":"35705031","id":"PMC_35705031","title":"Oncogenic ZMYND11-MBTD1 fusion protein anchors the NuA4/TIP60 histone acetyltransferase complex to the coding region of active genes.","date":"2022","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/35705031","citation_count":10,"is_preprint":false},{"pmid":"37523546","id":"PMC_37523546","title":"MBTD1 preserves adult hematopoietic stem cell pool size and function.","date":"2023","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/37523546","citation_count":6,"is_preprint":false},{"pmid":"36434485","id":"PMC_36434485","title":"Long Non-coding RNA H19 Recruits NFYB to Activate MBTD1 and Regulate Doxorubicin Resistance in Lymphoma Cells.","date":"2022","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/36434485","citation_count":4,"is_preprint":false},{"pmid":"39258225","id":"PMC_39258225","title":"Acute myeloid leukemia with a ZMYND11::MBTD1 fusion gene following chemotherapy and radiotherapy for breast cancer: A case report.","date":"2024","source":"Leukemia research reports","url":"https://pubmed.ncbi.nlm.nih.gov/39258225","citation_count":2,"is_preprint":false},{"pmid":"41454826","id":"PMC_41454826","title":"ZMYND11::MBTD1 Fusion in Myeloid/NK Cell Precursor Leukemia: A Case Report With Literature Review and Diagnostic Implications.","date":"2025","source":"Pediatric blood & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/41454826","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8398,"output_tokens":2499,"usd":0.031339,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9594,"output_tokens":2998,"usd":0.06146,"stage2_stop_reason":"end_turn"},"total_usd":0.092799,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of MBTD1 (residues 130–566, covering 4 MBT repeats) was solved at 2.5 Å resolution by X-ray crystallography, revealing an asymmetric rhomboid architecture similar to L3MBTL2. Fluorescence polarization experiments confirmed that MBTD1 preferentially binds mono- and di-methylated lysine histone peptides through a semi-aromatic cage in one of its four MBT repeats, using a 'cavity insertion recognition mode'.\",\n      \"method\": \"X-ray crystallography + fluorescence polarization + mutagenesis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure at 2.5 Å combined with fluorescence polarization binding assays and mutagenesis in a single rigorous study\",\n      \"pmids\": [\"19841675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MBTD1 associates with the histone methyltransferase Pr-Set7 (SET8/KMT5A) in mouse oocytes, as demonstrated by co-immunoprecipitation. Depletion of MBTD1 reduced Pr-Set7 levels and H4K20me1, caused GV-stage arrest, increased γH2AX foci, downregulated 53BP1, activated Chk1, and downregulated cyclin B1 and Cdc2, phenocopying Pr-Set7 depletion. This places MBTD1 upstream of Pr-Set7/H4K20me1 maintenance during meiotic maturation.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, immunofluorescence, Western blot in mouse oocytes\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal phenotypic rescue and Co-IP from a single lab with multiple orthogonal readouts\",\n      \"pmids\": [\"23475131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structure of the MBTD1–EPC1 complex revealed that a hydrophobic C-terminal fragment of EPC1 engages the MBT repeats of MBTD1 at a site distinct from the H4K20me-binding site, providing the structural basis for recruitment of MBTD1 into the NuA4/TIP60 acetyltransferase complex. Cellular assays validated the physiological significance of key interface residues.\",\n      \"method\": \"X-ray crystallography of MBTD1–EPC1 complex + cellular validation assays (mutagenesis of interface residues)\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of binary complex combined with mutagenesis and cellular validation in one rigorous study\",\n      \"pmids\": [\"32209463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"NuA4/TIP60 complex, through MBTD1 reading H4K20me and acetylation of H2AK15, inhibits 53BP1 binding to chromatin at DNA breaks by blocking the ubiquitination mark required for 53BP1 localization, thereby influencing DNA repair pathway choice.\",\n      \"method\": \"Biochemical and cellular assays reported in the context of the structural study\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic model supported by cellular assays in a single rigorous structural paper, but described concisely in the abstract\",\n      \"pmids\": [\"32209463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The oncogenic ZMYND11-MBTD1 (ZM) fusion protein recruits the NuA4/TIP60 histone acetyltransferase complex to cis-regulatory elements of pro-leukemic genes (Hoxa, Meis1, Myb, Myc, Sox4), sustaining active chromatin enriched in histone acetylation. Systematic mutagenesis demonstrated that Tip60 interaction (mediated through the MBTD1 portion) and an H3K36me3-binding PWWP domain (from ZMYND11) are both essential for oncogenesis. ZM confers indefinite self-renewal on murine hematopoietic stem/progenitor cells ex vivo and causes AML in vivo.\",\n      \"method\": \"Genomics profiling (ChIP-seq, ATAC-seq), systematic mutagenesis, ex vivo and in vivo murine AML models, inhibitor studies\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genomic and functional methods, in vivo model, mutagenesis dissecting domains, single lab but comprehensive\",\n      \"pmids\": [\"33594072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ZMYND11-MBTD1 is stably incorporated into the endogenous NuA4/TIP60 complex (biochemically confirmed), and this fusion mislocalizes the complex to the bodies of genes normally bound by ZMYND11, correlating with increased chromatin acetylation, altered transcription of specific genes including MYC, and alternative splicing. Expression of ZMYND11-MBTD1 favors Myc-driven pluripotency during ES cell differentiation and promotes hematopoietic stem/progenitor self-renewal.\",\n      \"method\": \"Biochemical co-purification/MS, ChIP-seq, RNA-seq, ES cell differentiation assays, hematopoietic progenitor self-renewal assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical incorporation into endogenous complex confirmed by MS, multiple genomic and functional assays, replicates and extends prior findings\",\n      \"pmids\": [\"35705031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MBTD1 directly binds to the promoter region of FoxO3a (a forkhead protein essential for HSC quiescence) and interacts with components of the TIP60 chromatin remodeling complex. Conditional knockout of Mbtd1 in adult mice caused increased HSC and progenitor numbers, hyperactive cell cycle, and defective stress response; restoration of FOXO3a activity rescued these abnormalities, placing MBTD1 upstream of FOXO3a in HSC quiescence maintenance.\",\n      \"method\": \"Conditional knockout mice, ChIP (MBTD1 binding to FoxO3a promoter), Co-IP (interaction with TIP60 components), genetic rescue (FOXO3a restoration in vivo)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO in vivo, direct promoter binding by ChIP, Co-IP with complex components, and genetic rescue with multiple readouts\",\n      \"pmids\": [\"37523546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The transcription factor NFYB binds to the MBTD1 promoter to activate MBTD1 transcription (validated by luciferase reporter and ChIP-qPCR). The lncRNA H19 recruits NFYB to the MBTD1 promoter, increasing MBTD1 expression without altering NFYB protein levels, thereby promoting doxorubicin resistance in lymphoma cells.\",\n      \"method\": \"Luciferase reporter assay, ChIP-qPCR, siRNA knockdown, in vitro and in vivo lymphoma models\",\n      \"journal\": \"Molecular biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — ChIP-qPCR and luciferase reporter support NFYB-mediated MBTD1 transcriptional activation; single lab, focused on upstream regulation of MBTD1 expression\",\n      \"pmids\": [\"36434485\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MBTD1 is a Polycomb-group nuclear protein containing four MBT repeats that form an asymmetric rhomboid structure capable of binding mono- and di-methylated lysine histone peptides (particularly H4K20me1/2) through a semi-aromatic cage; it is recruited into the NuA4/TIP60 histone acetyltransferase complex via a direct interaction between its MBT repeats and the C-terminal hydrophobic fragment of EPC1, where it acts as an H4K20me reader to direct TIP60-mediated H2AK15 acetylation that blocks 53BP1 chromatin binding and influences DNA repair pathway choice; in hematopoietic stem cells MBTD1 binds the FoxO3a promoter and interacts with TIP60 complex components to maintain HSC quiescence, and the oncogenic ZMYND11-MBTD1 fusion aberrantly mislocalizes the NuA4/TIP60 complex to gene bodies via the ZMYND11 H3K36me3-reading PWWP domain, driving histone acetylation and transcriptional activation of pro-leukemic genes including MYC and HOXA clusters to cause AML.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MBTD1 is a Polycomb-group nuclear protein that functions as a methyl-lysine histone reader and serves as a recruitment module for the NuA4/TIP60 histone acetyltransferase complex, governing DNA repair pathway choice and hematopoietic stem cell quiescence [#0, #3, #6]. Its four MBT repeats form an asymmetric rhomboid architecture in which a semi-aromatic cage in one repeat preferentially engages mono- and di-methylated lysine histone peptides via a cavity-insertion recognition mode [#0]. A hydrophobic C-terminal fragment of EPC1 binds the MBT repeats at a site distinct from the methyl-lysine pocket, structurally explaining how MBTD1 is incorporated into the NuA4/TIP60 complex [#2]; within this complex MBTD1 reads H4K20me to direct TIP60-mediated H2AK15 acetylation, which blocks 53BP1 chromatin loading and thereby influences DNA double-strand break repair [#3]. In hematopoietic stem cells MBTD1 binds the FoxO3a promoter and associates with TIP60 complex components, acting upstream of FOXO3a to enforce quiescence, since its loss expands stem/progenitor pools and hyperactivates the cell cycle while FOXO3a restoration rescues the defect [#6]. The oncogenic ZMYND11-MBTD1 fusion mislocalizes the NuA4/TIP60 complex—via MBTD1-mediated TIP60 binding and the ZMYND11 H3K36me3-reading PWWP domain—to the bodies and regulatory elements of pro-leukemic genes including MYC and HOXA clusters, sustaining aberrant histone acetylation and transcriptional activation that drives acute myeloid leukemia [#4, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established the structural and biochemical basis for MBTD1 as a methyl-lysine reader, defining how it recognizes histone marks.\",\n      \"evidence\": \"X-ray crystallography of the four MBT repeats with fluorescence polarization binding and mutagenesis\",\n      \"pmids\": [\"19841675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not identify the in vivo histone substrate or genomic targets\",\n        \"No functional role demonstrated at this stage\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked MBTD1 to maintenance of the H4K20me1 mark by placing it upstream of the methyltransferase Pr-Set7/SET8 during meiotic maturation.\",\n      \"evidence\": \"Co-IP, siRNA knockdown, and phenocopy analysis in mouse oocytes\",\n      \"pmids\": [\"23475131\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which MBTD1 stabilizes Pr-Set7 unresolved\",\n        \"Single-lab study in a specialized cell type\",\n        \"Direct enzymatic relationship not reconstituted\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the molecular interface that recruits MBTD1 into the NuA4/TIP60 complex and connected this to DNA repair pathway choice via H2AK15 acetylation and 53BP1 exclusion.\",\n      \"evidence\": \"Crystal structure of the MBTD1–EPC1 complex with cellular validation and break-repair assays\",\n      \"pmids\": [\"32209463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"53BP1 exclusion model described concisely and rests on cellular assays in one paper\",\n        \"Quantitative contribution of MBTD1 to repair outcomes not fully mapped\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated that the ZMYND11-MBTD1 fusion is oncogenic, requiring both TIP60 interaction through MBTD1 and the ZMYND11 PWWP domain to redirect the complex to pro-leukemic genes.\",\n      \"evidence\": \"ChIP-seq, ATAC-seq, systematic domain mutagenesis, and ex vivo/in vivo murine AML models\",\n      \"pmids\": [\"33594072\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Single-lab study despite comprehensive methods\",\n        \"Therapeutic targetability of the fusion not established\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed biochemical incorporation of the fusion into the endogenous NuA4/TIP60 complex and showed it mislocalizes the complex to gene bodies, altering transcription and splicing to favor Myc-driven self-renewal.\",\n      \"evidence\": \"Co-purification/MS, ChIP-seq, RNA-seq, and ES cell and hematopoietic self-renewal assays\",\n      \"pmids\": [\"35705031\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanistic link between mislocalization and alternative splicing not detailed\",\n        \"Relative roles of MYC versus other targets in leukemogenesis unresolved\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified upstream transcriptional regulation of MBTD1, with NFYB activating its promoter and lncRNA H19 enhancing this to promote chemoresistance.\",\n      \"evidence\": \"Luciferase reporter, ChIP-qPCR, siRNA knockdown, and lymphoma models\",\n      \"pmids\": [\"36434485\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study focused on expression regulation rather than MBTD1 mechanism\",\n        \"Whether chemoresistance depends on MBTD1 reader/complex functions untested\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established a physiological role for MBTD1 in HSC quiescence by placing it upstream of FOXO3a through direct promoter binding and TIP60 complex association.\",\n      \"evidence\": \"Conditional knockout mice, ChIP at the FoxO3a promoter, Co-IP, and genetic rescue with FOXO3a restoration\",\n      \"pmids\": [\"37523546\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How MBTD1 activates FoxO3a transcription mechanistically not defined\",\n        \"Connection between HSC quiescence role and the DNA-repair reader function not integrated\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MBTD1's methyl-lysine reading, repair-pathway control, and transcriptional/HSC functions are mechanistically unified, and whether the ZMYND11-MBTD1 fusion is therapeutically targetable, remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No integrated model linking H4K20me reading to FoxO3a regulation\",\n        \"No structural data on MBTD1 within the assembled NuA4/TIP60 complex\",\n        \"Druggability of the fusion or MBTD1–EPC1 interface untested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 5, 6]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [3, 4, 5]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 5, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"complexes\": [\"NuA4/TIP60 histone acetyltransferase complex\"],\n    \"partners\": [\"EPC1\", \"TIP60\", \"ZMYND11\", \"Pr-Set7/SET8/KMT5A\", \"NFYB\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}