Affinage

L3MBTL1

Lethal(3)malignant brain tumor-like protein 1 · UniProt Q9Y468

Length
840 aa
Mass
92.3 kDa
Annotated
2026-06-10
24 papers in source corpus 14 papers cited in narrative 16 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

L3MBTL1 is a methyl-lysine-dependent chromatin compaction factor that reads low methylation states on histone and non-histone substrates to enforce transcriptional repression and to gate the DNA damage response (PMID:17540172, PMID:18408754). Through its triple MBT repeats it recognizes mono- and dimethylated lysines in a basic context, requiring a conserved aspartate (D355) and an aromatic cage pocket that is energetically tuned to penalize unmethylated and trimethylated lysine while accommodating me1/me2 states (PMID:18408754, PMID:21428286); in this capacity it binds H4K20me1/me2 and H1bK26 methylation, bridges at least two nucleosomes to compact chromatin, and assembles with core histones, H1b, HP1gamma, and Rb to repress E2F-regulated genes (PMID:17540172). Its chromatin loading depends on the H4K20 monomethyltransferase PR-SET7/SET8, which it binds directly, tracking the cell-cycle accumulation of H4K20me1 (PMID:18408754). The same SET8 enzyme monomethylates p53 at K382, generating a docking mark that recruits L3MBTL1 to p53 target promoters to repress p21 and PUMA; DNA damage erases this mark and dissociates L3MBTL1 (PMID:20870725). At DNA double-strand breaks, L3MBTL1 competes with 53BP1 for H4K20me2, and RNF8-dependent ubiquitylation recruits the VCP/p97-NPL4 ATPase to extract L3MBTL1 from chromatin, unmasking the mark for 53BP1 loading (PMID:22120668, PMID:39231972). L3MBTL1 additionally associates with the replication machinery (Cdc45, MCM2-7, PCNA) to sustain fork progression and prevent replicative stress and genomic instability (PMID:21149733). Beyond genome maintenance, it acts as a cell-type-specific transcriptional regulator: it represses SMAD5 to restrain hematopoietic and erythroid differentiation, occupies the Ctnnb1 locus to enable homeostatic synaptic downscaling in neurons, and controls p53-dependent protein quality control systems that clear misfolded proteins across species (PMID:25754204, PMID:29898393, PMID:31061493).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2007 High

    Established the core molecular function by showing L3MBTL1 is a methylation-dependent chromatin compactor rather than merely a histone binder, defining how it represses transcription.

    Evidence Co-IP of an L3MBTL1-histone-H1b-HP1gamma-Rb complex plus in vitro nucleosomal array compaction and E2F target gene analysis

    PMID:17540172

    Open questions at the time
    • Compaction shown in vitro on arrays; in vivo genomic compaction targets not mapped
    • Functional contribution of each complex member to repression not dissected
  2. 2008 High

    Defined the binding specificity and the enzymatic source of its chromatin mark, showing L3MBTL1 reads me1/me2 lysines via D355 and is loaded onto chromatin downstream of PR-SET7/SET8.

    Evidence Histone peptide binding assays, D355 active-site mutagenesis, PR-SET7 Co-IP and knockdown, cell-cycle chromatin fractionation

    PMID:18408754

    Open questions at the time
    • Peptide-based specificity later shown to differ in nucleosome context
    • Whether PR-SET7 binding directly templates L3MBTL1 recruitment versus simply generating the mark not separated
  3. 2010 High

    Extended reader activity to a non-histone substrate, showing SET8-methylated p53K382me1 recruits L3MBTL1 to repress pro-apoptotic and cell-cycle-arrest targets and that DNA damage reverses this.

    Evidence X-ray crystallography, biochemical binding, Co-IP, ChIP, and siRNA with RT-PCR on p21/PUMA

    PMID:20870725

    Open questions at the time
    • Demethylase reversing p53K382me1 during damage not identified here
    • Relative contribution of histone vs p53 reading to p53-target repression unquantified
  4. 2010 High

    Linked L3MBTL1 directly to replication fork integrity, showing it physically contacts replisome components and its loss causes replicative stress and genomic instability.

    Evidence Co-IP with Cdc45/MCM2-7/PCNA, DNA fiber assays, and gammaH2AX/DDR markers after siRNA depletion

    PMID:21149733

    Open questions at the time
    • Whether replisome association requires MBT methyl-reading is unresolved
    • Mechanism by which L3MBTL1 supports fork progression not defined
  5. 2011 High

    Resolved how L3MBTL1 is removed from chromatin at breaks, showing RNF8-ubiquitylation recruits VCP/p97 to extract it and license 53BP1 binding to H4K20me2.

    Evidence siRNA, laser micro-irradiation, VCP ATPase inhibition, RIDDLE-cell epistasis, and C. elegans genetics

    PMID:22120668

    Open questions at the time
    • Direct ubiquitylation target on/near L3MBTL1 not pinpointed
    • Stoichiometry of L3MBTL1 vs 53BP1 competition in vivo not quantified
  6. 2011 Medium

    Provided a biophysical explanation for dual me1/me2 recognition, showing the methyl-lysine pocket is an energetic compromise enforced by an aromatic cage.

    Evidence Molecular dynamics, free energy perturbation, and ITC with designed probes

    PMID:21428286

    Open questions at the time
    • No mutagenesis or new structure in this study
    • Predictions made on isolated domains, not nucleosome context
  7. 2004 Medium

    Identified L3MBTL1 as an imprinted, paternally expressed polycomb gene subject to monoallelic CpG methylation, establishing a regulatory layer over its own expression.

    Evidence Bisulfite sequencing and allele-specific expression analysis in family trios across hematopoietic cell types

    PMID:15123827

    Open questions at the time
    • Functional consequence of imprinting for phenotype not tested
    • Tissue breadth of imprinting beyond hematopoietic cells unclear
  8. 2015 Medium

    Defined a developmental transcriptional role, showing L3MBTL1 represses SMAD5 and its target program to balance hematopoietic versus neural fate and erythroid differentiation.

    Evidence shRNA knockdown in hPSCs, SMAD5 ChIP, expression analysis, and hematopoietic differentiation assays

    PMID:20585043 PMID:21341991 PMID:25754204

    Open questions at the time
    • Whether SMAD5 repression is direct methyl-reading-dependent not shown
    • Lineage-determination mechanism integrating multiple fate phenotypes not unified
  9. 2018 High

    Established a neuronal function by genetic knockout, showing activity-regulated L3mbtl1 occupies the Ctnnb1 locus and is required for homeostatic synaptic downscaling via beta-catenin.

    Evidence ChIP-seq/CUT&RUN occupancy, L3mbtl1 knockout mice, electrophysiology, and Ctnnb1 re-expression rescue

    PMID:29898393

    Open questions at the time
    • Methylation mark mediating Ctnnb1 occupancy not identified
    • How neuronal activity downregulates L3mbtl1 not mechanistically resolved
  10. 2019 High

    Connected L3MBTL1 to p53-dependent protein quality control, showing its loss is protective against proteotoxic aggregates in a conserved pathway involving SET8 and p53.

    Evidence C. elegans and mammalian neuron loss-of-function, proteotoxicity assays, Co-IP with SET8/p53, PQC marker westerns

    PMID:31061493

    Open questions at the time
    • Direct PQC genes repressed by L3MBTL1-p53 not enumerated
    • Whether chromatin-reading or p53-binding drives the effect not separated
  11. 2024 Medium

    Implicated L3MBTL1 in therapy resistance, showing EGFR inhibition stabilizes it and its 53BP1-competing activity supports the DNA damage response in Osimertinib-resistant lung cancer.

    Evidence siRNA/shRNA, 53BP1/H4K20me2 competition Co-IP, DDR westerns, and xenografts

    PMID:39231972

    Open questions at the time
    • Mechanism by which EGFR signaling controls L3MBTL1 ubiquitination not defined
    • Single lab; clinical relevance not validated in patient samples
  12. 2025 Medium

    Revised the binding model by showing nucleosome context, not peptides, dictates true L3MBTL1 specificity, abrogating much of the peptide-defined methyl-state binding.

    Evidence Biochemical binding to defined nucleosomes vs peptides with CUT&RUN genomic confirmation (preprint)

    PMID:bio_10.1101_2025.04.29.651129

    Open questions at the time
    • Preprint, not peer-reviewed
    • Structural basis for nucleosome-imposed restriction not determined

Open questions

Synthesis pass · forward-looking unresolved questions
  • How L3MBTL1's distinct activities — nucleosome compaction, p53 reading, replisome association, and break-site eviction — are coordinated and partitioned across cell types remains unresolved.
  • No unified model linking chromatin-reading to replication-fork and PQC roles
  • Determinants of cell-type-specific target selection not defined
  • No reconciliation of peptide-era specificity claims with nucleosome-context binding

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140110 transcription regulator activity 4 GO:0042393 histone binding 3 GO:0003677 DNA binding 1
Localization
GO:0000228 nuclear chromosome 3 GO:0005634 nucleus 3
Pathway
R-HSA-74160 Gene expression (Transcription) 3 R-HSA-4839726 Chromatin organization 2 R-HSA-73894 DNA Repair 2 R-HSA-69306 DNA Replication 1
Partners
CBX3CDC45HIST1H1BPCNARB1SETD8TP53VCP

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 L3MBTL1 forms a complex with core histones, histone H1b, HP1gamma, and Rb, and its MBT domains compact nucleosomal arrays dependent on mono- and dimethylation of histone H4K20 and histone H1b K26, with the MBT domains binding at least two nucleosomes simultaneously to repress transcription. Co-immunoprecipitation, nucleosomal array compaction assay, chromatin binding assays Cell High 17540172
2007 L3MBTL1 negatively regulates the expression of a subset of genes regulated by E2F, a transcription factor that interacts with Rb, linking L3MBTL1 to Rb-mediated transcriptional repression. Gene expression analysis following L3MBTL1 modulation; Co-IP with Rb Cell Medium 17540172
2008 L3MBTL1 MBT domains recognize mono- and dimethylated lysines in histones H3, H4 and H1.4 (but not trimethylated or unmodified counterparts) in a basic amino-acid context requiring a conserved aspartic acid (D355) in the second MBT repeat; chromatin association of L3MBTL1 mirrors progressive accumulation of H4K20 monomethylation during the cell cycle. Histone peptide binding assays, active-site mutagenesis (D355), chromatin fractionation across cell cycle Oncogene High 18408754
2008 Transcriptional repression by L3MBTL1 is enhanced by the H4K20 monomethyltransferase PR-SET7, to which it physically binds; knockdown of PR-SET7 decreases H4K20me1 and reduces chromatin association of L3MBTL1. Co-immunoprecipitation, knockdown of PR-SET7, chromatin fractionation, transcriptional reporter assays Oncogene High 18408754
2010 The triple MBT repeats of L3MBTL1 preferentially recognize SET8/PR-Set7-mediated monomethylation of p53 at lysine 382 (p53K382me1); SET8-mediated methylation of p53 promotes L3MBTL1–p53 interaction in cells and chromatin occupancy of L3MBTL1 at p53 target promoters, repressing p21 and PUMA; DNA damage abrogates p53K382me1, disrupts the L3MBTL1–p53 interaction, and dissociates L3MBTL1 from target promoters. Biochemical binding assays, X-ray crystallography, Co-IP in cells, ChIP, siRNA knockdown with RT-PCR The Journal of biological chemistry High 20870725
2010 L3MBTL1 interacts with Cdc45, MCM2-7, and PCNA (components of the DNA replication machinery) and is required for normal replication fork progression; depletion of L3MBTL1 causes replicative stress, DNA breaks, activation of the DNA damage response, and genomic instability. Co-immunoprecipitation, DNA fiber assay (replication fork progression), γH2AX/DNA damage markers upon siRNA knockdown Proceedings of the National Academy of Sciences of the United States of America High 21149733
2011 RNF8-mediated ubiquitylation facilitates recruitment of the AAA-ATPase VCP/p97 and cofactor NPL4 to DNA double-strand break sites; VCP ATPase activity promotes release of L3MBTL1 from chromatin (where it competes with 53BP1 for H4K20me2), thereby unmasking H4K20me2 and enabling 53BP1 recruitment. siRNA knockdown, live-cell imaging, laser micro-irradiation, VCP ATPase inhibition, epistasis in RIDDLE cells, C. elegans genetic analysis Nature structural & molecular biology High 22120668
2011 Biophysical and computational analysis demonstrates that the methyl-lysine binding pocket of L3MBTL1 is a structural 'compromise' that nonoptimally binds both mono- and dimethyl-lysine but penalizes unmethylated and trimethylated lysine, with a conserved aromatic cage mechanism; ITC measurements validated the MD/FEP computational predictions. Molecular dynamics (MD), free energy perturbation (FEP), isothermal titration calorimetry (ITC) with designed biophysical probes Journal of the American Chemical Society Medium 21428286
2010 Knockdown of L3MBTL1 in human cord blood CD34+ hematopoietic progenitors promotes enhanced erythroid differentiation and increases Epo-induced phosphorylation of STAT5, AKT, and MAPK; overexpression of L3MBTL1 restricts erythroid differentiation; L3MBTL1 levels decrease during hemin-induced erythropoiesis. shRNA knockdown and overexpression in primary CD34+ cells, flow cytometry for erythroid markers, western blot for signaling phosphorylation Blood Medium 20585043
2011 L3MBTL1 knockdown in human embryonic stem cells directs spontaneous differentiation exclusively toward trophectoderm/trophoblast fate, with expression of trophoblast markers and secretion of placental hormones, without affecting hESC self-renewal under maintenance conditions. Constitutive shRNA knockdown in hESCs, spontaneous differentiation assay, immunostaining, hormone secretion assay Stem cells and development Medium 21341991
2015 L3MBTL1 represses SMAD5 expression and impairs SMAD5 recruitment to target regulatory regions in human pluripotent stem cells; knockdown of L3MBTL1 promotes hematopoietic development and impairs neural cell fate, while also affecting SMAD5 target gene expression in mature hematopoietic cells to regulate erythroid differentiation. shRNA knockdown in hPSCs, ChIP for SMAD5 occupancy, gene expression analysis, hematopoietic differentiation assays Stem cell reports Medium 25754204
2018 L3mbtl1 is downregulated by neuronal activity; genome-scale mapping shows L3mbtl1 occupies the Ctnnb1 (beta-catenin) gene locus; L3mbtl1 knockout reduces Ctnnb1 expression, impairs excitatory synaptic transmission, and abolishes homeostatic synaptic downscaling; re-expression of Ctnnb1 in knockout neurons restores downscaling. ChIP-seq/CUT&RUN for L3mbtl1 occupancy, L3mbtl1 knockout mice, electrophysiology, Ctnnb1 partial knockdown and re-expression rescue experiment Cell reports High 29898393
2019 L3MBTL1 regulates p53-dependent protein quality control systems that degrade misfolded proteins; loss of L3MBTL1 protects against proteotoxicity of mutant SOD1 or C9orf72 dipeptide repeats; the role is conserved from C. elegans to mammalian neurons; SET8, an L3MBTL1-associated p53-binding protein, also regulates misfolded protein clearance. siRNA knockdown and genetic knockout (C. elegans), proteotoxicity assays, Co-IP of L3MBTL1 with SET8/p53, western blot for protein quality control markers Nature neuroscience High 31061493
2024 In Osimertinib-resistant lung adenocarcinoma cells, L3MBTL1 competes with 53BP1 for H4K20me2 binding and regulates chromatin structure to modulate the DNA damage response; EGFR inhibition reduces L3MBTL1 ubiquitination and stabilizes its expression; L3MBTL1 reduction combined with Osimertinib significantly inhibited DNA damage response and proliferation of resistant cells in vitro and in vivo. siRNA/shRNA knockdown, Co-IP for H4K20me2 competition with 53BP1, xenograft in vivo experiments, western blot for DDR markers Cell death & disease Medium 39231972
2025 In nucleosome context (rather than histone peptides alone), L3MBTL1 MBT domain binding to histone tails with lower methyl states (me1 or me2 at H3K4, H3K9, H3K27, H3K36, or H4K20) is abrogated, demonstrating that nucleosome context restricts L3MBTL1 binding specificity beyond what peptide assays reveal; in vitro nucleosome preferences were confirmed by in vivo CUT&RUN genomic mapping. Biochemical binding assays with defined nucleosome substrates vs. peptides, CUT&RUN genomic mapping bioRxivpreprint Medium bio_10.1101_2025.04.29.651129
2004 L3MBTL1 (L3MBTL) undergoes monoallelic DNA methylation of two CpG islands correlating with transcriptional silencing, and is expressed from the paternally derived allele in multiple hematopoietic cell types, establishing it as an imprinted polycomb gene. Bisulfite sequencing for allele-specific methylation, allele-specific expression analysis in family trios Proceedings of the National Academy of Sciences of the United States of America Medium 15123827

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 L3MBTL1, a histone-methylation-dependent chromatin lock. Cell 281 17540172
2011 The AAA-ATPase VCP/p97 promotes 53BP1 recruitment by removing L3MBTL1 from DNA double-strand breaks. Nature structural & molecular biology 235 22120668
2008 Histone H4 lysine 20 monomethylation promotes transcriptional repression by L3MBTL1. Oncogene 124 18408754
2011 Physical activity and breast cancer survival: an epigenetic link through reduced methylation of a tumor suppressor gene L3MBTL1. Breast cancer research and treatment 71 21837478
2010 The MBT repeats of L3MBTL1 link SET8-mediated p53 methylation at lysine 382 to target gene repression. The Journal of biological chemistry 71 20870725
2010 L3MBTL1 polycomb protein, a candidate tumor suppressor in del(20q12) myeloid disorders, is essential for genome stability. Proceedings of the National Academy of Sciences of the United States of America 69 21149733
2004 Imprinting of the human L3MBTL gene, a polycomb family member located in a region of chromosome 20 deleted in human myeloid malignancies. Proceedings of the National Academy of Sciences of the United States of America 69 15123827
2010 Depletion of L3MBTL1 promotes the erythroid differentiation of human hematopoietic progenitor cells: possible role in 20q- polycythemia vera. Blood 40 20585043
2004 Structural integrity and expression of the L3MBTL gene in normal and malignant hematopoietic cells. Genes, chromosomes & cancer 30 15334543
2004 Characterization of the imprinted polycomb gene L3MBTL, a candidate 20q tumour suppressor gene, in patients with myeloid malignancies. British journal of haematology 30 15566354
2011 Biophysical probes reveal a "compromise" nature of the methyl-lysine binding pocket in L3MBTL1. Journal of the American Chemical Society 28 21428286
2008 Beyond histone methyl-lysine binding: how malignant brain tumor (MBT) protein L3MBTL1 impacts chromatin structure. Cell cycle (Georgetown, Tex.) 26 18256536
2010 Chromatin protein L3MBTL1 is dispensable for development and tumor suppression in mice. The Journal of biological chemistry 23 20592034
2018 Activity-Induced Regulation of Synaptic Strength through the Chromatin Reader L3mbtl1. Cell reports 22 29898393
2005 L3mbtl, the mouse orthologue of the imprinted L3MBTL, displays a complex pattern of alternative splicing and escapes genomic imprinting. Genomics 17 16081246
2019 L3MBTL1 regulates ALS/FTD-associated proteotoxicity and quality control. Nature neuroscience 14 31061493
2016 Parental origin of the deletion del(20q) in Shwachman-Diamond patients and loss of the paternally derived allele of the imprinted L3MBTL1 gene. Genes, chromosomes & cancer 10 27553422
2011 L3MBTL1 deficiency directs the differentiation of human embryonic stem cells toward trophectoderm. Stem cells and development 10 21341991
2022 Influences of fresh and frozen embryo transfer on neonatal birthweight and the expression of imprinted genes PEG10 /L3MBTL1 in placenta. Reproductive biology 7 35714554
2019 Rational Adaptation of L3MBTL1 Inhibitors to Create Small-Molecule Cbx7 Antagonists. ChemMedChem 7 31254321
2024 L3MBTL1, a polycomb protein, promotes Osimertinib acquired resistance through epigenetic regulation of DNA damage response in lung adenocarcinoma. Cell death & disease 6 39231972
2021 Expression and DNA Methylation Status of the Imprinted Genes PEG10 and L3MBTL1 in the Umbilical Cord Blood and Placenta of the Offspring of Assisted Reproductive Technology. Reproductive sciences (Thousand Oaks, Calif.) 6 33515207
2015 The polycomb group protein L3MBTL1 represses a SMAD5-mediated hematopoietic transcriptional program in human pluripotent stem cells. Stem cell reports 5 25754204
2015 Cognition and mood-related behaviors in L3mbtl1 null mutant mice. PloS one 4 25849281

Missed literature

Know a paper Affinage missed for L3MBTL1? Flag it for the maintainers and the community.

No submissions yet.