Affinage

MIB2

E3 ubiquitin-protein ligase MIB2 · UniProt Q96AX9

Length
955 aa
Mass
103.7 kDa
Annotated
2026-04-28
26 papers in source corpus 22 papers cited in narrative 22 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MIB2 is a RING finger-dependent E3 ubiquitin ligase that regulates diverse cellular processes—including Notch signaling, NF-κB activation, YAP/TAZ turnover, immune checkpoint trafficking, and receptor sorting—by catalyzing both K63- and K48-linked ubiquitination of distinct substrate classes. MIB2 ubiquitinates Notch ligands (Jagged-2, Delta family members) to promote their endocytosis and activate Notch signaling, a function conserved from zebrafish to mammals and required for neural tube closure and cardiac trabeculation (PMID:15920166, PMID:17196985, PMID:17987667, PMID:28013292). Through K48-linked ubiquitination, MIB2 targets CYLD, YAP/TAZ, SUZ12, Runx2, and CARD6 for proteasomal degradation, thereby modulating NF-κB-driven inflammation, Hippo pathway output, PRC2-dependent chromatin silencing, and metabolic gene expression (PMID:31366726, PMID:37031213, PMID:40478202, PMID:40159625). MIB2 also catalyzes nonproteolytic K63-linked ubiquitination to direct PD-L1 from the trans-Golgi network to the plasma membrane via RAB8-mediated exocytosis and to sort GABAB receptors to lysosomes following CaMKIIβ-dependent phosphorylation (PMID:36719382, PMID:29881949).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2003 Medium

    Identification of MIB2 (skeletrophin) as a zinc-finger and ankyrin-repeat protein that binds actin monomer established its initial molecular identity and suggested cytoskeletal association.

    Evidence Yeast two-hybrid screen and co-immunoprecipitation in mammalian cells

    PMID:14507647

    Open questions at the time
    • Actin binding not confirmed by reciprocal pull-down with purified components
    • Functional significance of actin interaction never followed up
    • No catalytic activity demonstrated at this stage
  2. 2005 High

    Demonstrating that MIB2 is a RING-dependent E3 ubiquitin ligase that ubiquitinates Jagged-2 and activates Notch signaling resolved the catalytic function and first substrate specificity of MIB2.

    Evidence In vitro autoubiquitination assay with recombinant MIB2 and RING mutant; cell-based Hes-1 reporter

    PMID:15920166

    Open questions at the time
    • Whether MIB2 ubiquitinates other Notch ligands in mammals remained open
    • Ubiquitin chain linkage type not determined
    • In vivo relevance not yet tested
  3. 2006 High

    Zebrafish studies established that MIB2 and MIB are reciprocal E3 ligases sharing Delta substrates but differing in specificity, revealing functional redundancy and divergence within the MIB family for Notch ligand regulation.

    Evidence In vitro ubiquitination and Delta internalization assays with RING mutants in zebrafish; genetic epistasis in embryos

    PMID:17196985 PMID:17331493

    Open questions at the time
    • Relative contributions of MIB vs MIB2 in mammalian tissues unresolved
    • Structural basis for substrate selectivity differences unknown
  4. 2007 Medium

    Mouse Mib2 knockout causing exencephaly established an in vivo requirement for MIB2 in neural tube closure, extending its role beyond cell-autonomous Notch activation.

    Evidence Targeted gene knockout in mice with morphological phenotyping

    PMID:17987667

    Open questions at the time
    • Molecular substrates responsible for neural tube phenotype not identified
    • Variable penetrance suggests modifier effects not characterized
    • Notch-dependence of the phenotype not formally tested
  5. 2011 High

    Identification of MIB2 in the BCL10 signaling complex, where it ubiquitinates NEMO and recruits TAK1, revealed a Notch-independent role for MIB2 in NF-κB pathway activation.

    Evidence Proteomic identification of MIB2 in BCL10 complex; in vitro pulldown; siRNA knockdown with NF-κB reporter

    PMID:21896478

    Open questions at the time
    • Ubiquitin chain type on NEMO not specified
    • Physiological contexts requiring MIB2-dependent NF-κB activation not defined
    • Relationship between NF-κB and Notch functions of MIB2 unclear
  6. 2017 Medium

    Domain dissection in Drosophila showed ankyrin repeats and MIB-specific domains are essential for muscle integrity while the RING finger is specifically required for flight muscle development, establishing domain-specific functional requirements.

    Evidence Systematic domain deletion and missense mutagenesis in Drosophila with in vivo muscle phenotyping

    PMID:28282454

    Open questions at the time
    • Substrates mediating muscle phenotypes not identified
    • Whether domain requirements are conserved in mammalian muscle unknown
  7. 2018 High

    Showing that CaMKIIβ phosphorylation of GABAB1 at Ser-867 primes MIB2-mediated K63-linked ubiquitination for lysosomal sorting established a phosphorylation-dependent substrate recognition mechanism and a neuronal function for MIB2.

    Evidence Phosphomimetic/phospho-null mutagenesis; K63-ubiquitination assay; surface receptor quantification in cortical neurons

    PMID:29881949

    Open questions at the time
    • Whether MIB2 directly recognizes the phospho-degron or requires an adaptor unclear
    • In vivo neuronal phenotype of MIB2 loss not examined
  8. 2019 High

    Demonstrating that MIB2 K48-ubiquitinates CYLD at defined lysines for proteasomal degradation, and that Mib2 KO mice are protected from arthritis, established a direct MIB2–CYLD antagonism controlling NF-κB-driven inflammation in vivo.

    Evidence In vitro binding (AlphaScreen); site-specific K→R mutagenesis; Mib2 KO mice in arthritis model

    PMID:31366726

    Open questions at the time
    • How MIB2 itself is regulated in inflammatory contexts not defined
    • Relative contribution of CYLD degradation vs. direct NEMO ubiquitination to NF-κB activation unclear
  9. 2023 High

    Discovery that MIB2 K63-ubiquitinates PD-L1 for RAB8-mediated TGN-to-plasma membrane trafficking, and that MIB2 deficiency enhances antitumor immunity, established MIB2 as a druggable node in immune checkpoint regulation.

    Evidence MIB2 KO; K63-ubiquitination assay; RAB8 epistasis; surface PD-L1 flow cytometry; mouse tumor models

    PMID:36719382

    Open questions at the time
    • Specific PD-L1 lysine residues ubiquitinated not mapped
    • Whether MIB2 affects other immune checkpoint molecules unknown
  10. 2023 High

    Showing that FAT1 recruits MIB2 to ubiquitinate YAP/TAZ for proteasomal degradation in endothelial and tumor cells linked MIB2 to Hippo pathway regulation and angiogenesis control.

    Evidence Co-IP/interactome analysis; MIB2 KD in vitro and in vivo; YAP/TAZ ubiquitination assay; angiogenesis and xenograft models

    PMID:37031213 PMID:40478800

    Open questions at the time
    • Ubiquitin chain type on YAP/TAZ not determined
    • Whether FAT1-MIB2 interaction is direct or scaffold-mediated not resolved
  11. 2025 Medium

    Recent work expanded MIB2 substrates to include SUZ12 (controlling H3K27me3 and PRC2 target gene silencing), Runx2 (controlling fatty acid metabolism in cardiomyocytes), and GPX4 (regulating ferroptosis), broadening MIB2's role into chromatin regulation, cardiac metabolism, and cell death.

    Evidence Co-IP/mass spectrometry; ubiquitination assays; siRNA knockdown with RNA-seq; AAV9-mediated cardiac overexpression in mice; xenograft models

    PMID:40159625 PMID:40478202 PMID:40592077

    Open questions at the time
    • SUZ12 and Runx2 ubiquitination sites not mapped
    • Chain linkage type for GPX4 ubiquitination not determined
    • Each substrate identified by single lab without independent replication
  12. 2025 Medium

    Ebola virus VP35 binds MIB2 via an NNLNS motif to suppress MIB2-mediated interferon induction, revealing viral exploitation of MIB2 in innate immune evasion.

    Evidence Mutagenesis of VP35 NNLNS motif; minigenome and interferon induction assays

    PMID:40982696

    Open questions at the time
    • MIB2 substrates mediating interferon induction not identified
    • Whether other viral proteins similarly target MIB2 unknown
    • Single lab finding

Open questions

Synthesis pass · forward-looking unresolved questions
  • How MIB2 achieves substrate selectivity across its numerous targets (K48 vs K63 linkage, degradative vs trafficking outcomes), and what upstream signals regulate MIB2 activity and expression in different tissues, remain major unresolved questions.
  • No structural model of MIB2 with any substrate
  • Post-translational regulation of MIB2 catalytic activity largely unexplored
  • Tissue-specific substrate hierarchies not systematically defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 12 GO:0016874 ligase activity 3
Localization
GO:0005886 plasma membrane 2 GO:0005794 Golgi apparatus 1 GO:0005829 cytosol 1
Pathway
R-HSA-392499 Metabolism of proteins 8 R-HSA-162582 Signal Transduction 6 R-HSA-168256 Immune System 4 R-HSA-1266738 Developmental Biology 2 R-HSA-4839726 Chromatin organization 1 R-HSA-5357801 Programmed Cell Death 1
Partners
BCL10CYLDFAT1GPX4JAG2RUNX2SUZ12YAP1

Evidence

Reading pass · 22 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2003 MIB2 (skeletrophin) binds to actin monomer, as demonstrated by yeast two-hybrid screening and co-immunoprecipitation experiments; it contains a cysteine-rich zinc-finger motif and five ankyrin repeats. Yeast two-hybrid screen + co-immunoprecipitation The American journal of pathology Medium 14507647
2005 MIB2 (skeletrophin) is a RING finger-dependent E3 ubiquitin ligase that binds the intracellular region of Notch ligand Jagged-2 (but not Delta-1, -3, -4, or Jagged-1) and catalyzes its ubiquitination; RING-mutated MIB2 loses this activity. Exogenous MIB2, but not its RING mutant, induced Hes-1 expression in stromal cells through Notch signaling. In vitro autoubiquitination assay with recombinant proteins; RING mutant analysis; cell-based Hes-1 reporter The American journal of pathology High 15920166
2006 MIB2 (skeletrophin) reduces melanoma cell invasion in vitro and in vivo and suppresses colony formation in soft agar in a RING motif-dependent manner; it also downregulates transcription of the Met oncogene and increases Hes1 transcription. Loss-of-function/gain-of-function with RING mutant; invasion assay; soft agar colony formation; gene expression analysis Oncogene Medium 16715130
2006 Zebrafish Mib2, like Mib, has C-terminal-most RING finger-dependent E3 ubiquitin ligase activity; Mib and Mib2 are reciprocal E3 ubiquitin ligases and substrates of each other. They share DeltaC as a common substrate for ubiquitylation and endocytosis, but differ in DeltaD internalization. Mib and Mib2 bind differently to extracellular and intracellular parts of DeltaA and DeltaC. In vitro ubiquitination assay; RING mutant analysis; Delta internalization assay; binding assays in transfected cells Journal of molecular biology High 17196985
2007 Zebrafish Mib2 is colocalized with Mib in transfected cells and functions redundantly with Mib in regulating Notch signaling in embryos. Dominant-negative Mib alleles suppress Mib2 function in a dosage-dependent manner, indicating competitive interaction. Notch signaling negatively regulates mib expression in a Su(H)-dependent negative feedback loop. Colocalization in transfected cells; genetic epistasis in zebrafish embryos; dominant-negative analysis; Su(H) reporter assay Developmental biology High 17331493
2007 Targeted disruption of Mib2 in mice causes exencephaly (failure to close cranial neural tube) with variable penetrance dependent on genetic background, establishing a role for Mib2 in neural tube closure in vivo. Targeted gene knockout in mice; morphological phenotypic analysis Genesis (New York, N.Y. : 2000) Medium 17987667
2011 MIB2 is a component of the activated BCL10 signaling complex; it directly interacts with BCL10 (shown by in vitro translation/pulldown), promotes autoubiquitination and ubiquitination of IKKγ/NEMO, recruits and activates TAK1, and thereby controls BCL10-dependent NF-κB activation. MIB2 knockdown inhibits BCL10-dependent NF-κB activation. Proteomic identification; in vitro pulldown; overexpression; siRNA knockdown; NF-κB reporter assay The Journal of biological chemistry High 21896478
2014 CYLD (deubiquitinating enzyme) interacts with MIB2 (E3 ubiquitin ligase); coexpression of CYLD and MIB2 results in stabilization of MIB2 protein levels and reduced levels of JAG2, linking MIB2 to regulation of Notch signaling through CYLD. Proteomics-based interaction screen; co-expression experiments; siRNA knockdown of CYLD; Notch target gene expression analysis Oncotarget Medium 25565632
2017 In Drosophila, the ankyrin repeats (in their entirety) and the MIB-specific domains of Mib2 are essential for its function in maintaining integrity of larval skeletal and visceral muscles. The RING finger domain is required for adult flight muscle development. Missense mutations in the MIB domain and RING finger cause flightless hypomorphic phenotypes, establishing domain-specific functional requirements. Domain deletion/mutagenesis in vivo; forward genetic screen; in vivo imaging of flight muscles PloS one Medium 28282454
2017 MIB2 missense variant p.V742G shows reduced ubiquitination activity in vitro and is associated with reduced NOTCH signaling (decreased HES1 and NOTCH3 expression) in white blood cells; MIB2 variants affect NOTCH signaling, proliferation, and apoptosis in primary rat cardiomyocytes, establishing MIB2 as a regulator of NOTCH signaling relevant to cardiac trabeculation. In vitro ubiquitination assay with purified variant protein; whole exome sequencing; gene expression analysis; primary cardiomyocyte functional assays Human molecular genetics High 28013292
2018 MIB2 mediates Lys-63-linked ubiquitination of GABAB1 subunit of GABAB receptors, sorting them to lysosomes for degradation. CaMKIIβ (but not CaMKIIα) promotes MIB2-mediated K63-linked ubiquitination of GABAB1 at multiple sites by phosphorylating GABAB1 at Ser-867; phosphomimetic S867D mutation increases K63-ubiquitination while S867A mutation reduces it and increases surface expression. Overexpression of CaMKII isoforms; phosphomimetic/phospho-null mutagenesis; K63-ubiquitination assay; surface GABAB receptor quantification in cortical neurons Molecular neurobiology High 29881949
2019 MIB2 promotes proteasomal degradation of the deubiquitinating enzyme CYLD by catalyzing Lys-48-linked polyubiquitination of CYLD at Lys-338 and Lys-530. The ankyrin repeat of MIB2 interacts with the third CAP domain of CYLD. MIB2-dependent CYLD degradation activates NF-κB signaling via TNFα and LUBAC. Mib2-knockout mice showed suppressed arthritic inflammation and reduced serum IL-6. Cell-free AlphaScreen and pulldown assays; immunofluorescence; Mib2 KO cells and mice; site-specific ubiquitination mapping; arthritis model The Journal of biological chemistry High 31366726
2021 Gm364 (a multi-pass transmembrane protein) directly binds and anchors MIB2 on the membrane; membrane-localized MIB2 ubiquitinates and activates DLL3, which activates Notch2, leading to production of NICD2 that activates AKT to regulate oocyte meiosis and quality. Knockout mouse model; co-IP; oocyte phenotypic analysis (ROS, mitochondrial membrane potential, aneuploidy); epistasis experiments Cell death and differentiation Medium 34635817
2023 MIB2 is required for translocation of PD-L1 from the trans-Golgi network (TGN) to the plasma membrane. Mechanistically, MIB2 catalyzes nonproteolytic K63-linked ubiquitination of PD-L1, facilitating its trafficking via RAB8-mediated exocytosis from TGN to plasma membrane. MIB2 deficiency reduces PD-L1 surface expression and promotes antitumor T-cell immunity in mice. MIB2 knockdown/knockout; K63-ubiquitination assay; RAB8 epistasis; surface PD-L1 flow cytometry; in vivo mouse tumor models The Journal of clinical investigation High 36719382
2023 FAT1 acts as an upstream regulator of MIB2 in endothelial cells: FAT1 interacts with MIB2 (identified by interactome analysis), and together they promote ubiquitination and proteasomal degradation of YAP/TAZ. Loss of MIB2 in endothelial cells recapitulates FAT1 depletion, causing decreased YAP/TAZ degradation, increased YAP/TAZ signaling, and increased endothelial cell proliferation and angiogenesis. Co-IP/interactome analysis; MIB2 KD in vitro and in vivo; YAP/TAZ ubiquitination assay; angiogenesis models Nature communications High 37031213
2023 MIB2 interacts with CARD6 and promotes K48-linked CARD6 polyubiquitination and proteasomal degradation in hepatocytes under high fructose conditions; MIB2 knockdown reverses CARD6 downregulation and lipid accumulation, establishing MIB2 as an upstream regulator of CARD6 in hepatic lipid metabolism. Immunoprecipitation; immunofluorescence; siRNA knockdown; immunoblotting Food & function Medium 37186242
2024 MIB2 expression is increased in SN (surrounded nucleolus)-stage oocytes; depletion of MIB2 in SN oocytes disrupts meiotic apparatus and increases aneuploidy, while overexpression of MIB2 in NSN oocytes facilitates chromatin configuration transition from NSN to SN and mitigates spindle/chromosome disorganization. Quantitative proteomics; MIB2 depletion and overexpression in oocytes; meiotic phenotype analysis (spindle assembly, aneuploidy) Molecular & cellular proteomics Medium 39019259
2025 MIB2 directly interacts with and ubiquitinates SUZ12 (a PRC2 complex component), controlling SUZ12 stability and H3K27me3 levels; the MIB/HERC and ZZ-type domains of MIB2 mediate interaction with SUZ12. MIB2 knockdown reduces SUZ12 protein and H3K27me3, upregulates PRC2 target genes, and decreases cell proliferation. Immunoprecipitation + mass spectrometry; siRNA knockdown; ubiquitination assay; RNA-seq; flow cytometry; colony formation assay Journal of cellular and molecular medicine Medium 40478202
2025 MIB2 directly interacts with Runx2 and ubiquitinates it for degradation, thereby inhibiting Hmgcs2 transcription and impairing fatty acid metabolic processes in cardiomyocytes. Cardiac-specific overexpression of Mib2 in ob/ob mice worsens cardiac dysfunction and lipid accumulation. Immunoprecipitation; dual luciferase reporter assay; proteomic analysis; AAV9-mediated cardiac overexpression in mice Journal of cellular and molecular medicine Medium 40159625
2025 FAT1 loss in tumor cells (including HNSCC) decreases YAP/TAZ ubiquitination and degradation mediated by MIB2; suppression of MIB2 alone phenocopies FAT1 loss, reducing YAP/TAZ ubiquitination and increasing tumor cell proliferation in vitro and tumor growth in vivo. FAT1/MIB2 KD in tumor cells; YAP/TAZ ubiquitination assay; tumor xenograft in vivo; interactome analysis of FAT1 cytoplasmic domain PloS one High 40478800
2025 Ebola virus VP35 contains an NNLNS motif (residues 201–205) that serves as a direct binding site for MIB2; VP35 binding to MIB2 via this motif inhibits MIB2-mediated interferon induction and also suppresses EBOV minigenome RNA synthesis activity. Mutagenesis of NNLNS motif; minigenome assay; interferon induction assay; interaction mapping Proceedings of the National Academy of Sciences of the United States of America Medium 40982696
2025 MIB2 promotes ubiquitin-mediated degradation of GPX4 by interacting with GPX4, an interaction regulated by Nrf2; taraxerol treatment reduces MIB2-mediated GPX4 ubiquitination by targeting Nrf2/MIB2 interaction, triggering ferroptosis in breast cancer cells. Co-IP; dual-luciferase reporter assay; ubiquitination assay; xenograft in vivo model Phytomedicine Medium 40592077

Source papers

Stage 0 corpus · 26 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2022 MIB2: metal ion-binding site prediction and modeling server. Bioinformatics (Oxford, England) 88 35904542
2023 PD-L1 translocation to the plasma membrane enables tumor immune evasion through MIB2 ubiquitination. The Journal of clinical investigation 50 36719382
2005 Skeletrophin, a novel ubiquitin ligase to the intracellular region of Jagged-2, is aberrantly expressed in multiple myeloma. The American journal of pathology 49 15920166
2007 The characterization of zebrafish antimorphic mib alleles reveals that Mib and Mind bomb-2 (Mib2) function redundantly. Developmental biology 45 17331493
2011 The E3 ubiquitin ligase mind bomb-2 (MIB2) protein controls B-cell CLL/lymphoma 10 (BCL10)-dependent NF-κB activation. The Journal of biological chemistry 41 21896478
2006 A ubiquitin ligase, skeletrophin, is a negative regulator of melanoma invasion. Oncogene 34 16715130
2006 Zebrafish Mib and Mib2 are mutual E3 ubiquitin ligases with common and specific delta substrates. Journal of molecular biology 34 17196985
2023 Endothelial FAT1 inhibits angiogenesis by controlling YAP/TAZ protein degradation via E3 ligase MIB2. Nature communications 33 37031213
2019 The E3 ubiquitin ligase MIB2 enhances inflammation by degrading the deubiquitinating enzyme CYLD. The Journal of biological chemistry 29 31366726
2014 The cylindromatosis gene product, CYLD, interacts with MIB2 to regulate notch signalling. Oncotarget 26 25565632
2003 Down-regulation of a novel actin-binding molecule, skeletrophin, in malignant melanoma. The American journal of pathology 24 14507647
2018 Ca2+/Calmodulin-Dependent Protein Kinase II (CaMKII) β-Dependent Phosphorylation of GABAB1 Triggers Lysosomal Degradation of GABAB Receptors via Mind Bomb-2 (MIB2)-Mediated Lys-63-Linked Ubiquitination. Molecular neurobiology 22 29881949
2021 Gm364 coordinates MIB2/DLL3/Notch2 to regulate female fertility through AKT activation. Cell death and differentiation 14 34635817
2007 Targeted disruption of Mib2 causes exencephaly with a variable penetrance. Genesis (New York, N.Y. : 2000) 13 17987667
2017 MIB2 variants altering NOTCH signalling result in left ventricle hypertrabeculation/non-compaction and are associated with Ménétrier-like gastropathy. Human molecular genetics 8 28013292
2023 Nuciferine blocks MIB2-mediated CARD6 polyubiquitination and degradation in the amelioration of high fructose-induced liver lipid accumulation. Food & function 7 37186242
2017 Identification of the essential protein domains for Mib2 function during the development of the Drosophila larval musculature and adult flight muscles. PloS one 7 28282454
2005 Skeletrophin, a novel RING molecule controlled by the chromatin remodeling complex, is downregulated in malignant melanoma. DNA and cell biology 7 15869411
2025 Taraxerol induces ferroptosis in breast cancer by targeting Nrf2 transcriptional activity to promote MIB2-mediated GPX4 ubiquitination. Phytomedicine : international journal of phytotherapy and phytopharmacology 5 40592077
2025 Mib2 Regulates Lipid Metabolism in Heart Failure With Preserved Ejection Fraction via the Runx2-Hmgcs2 Axis. Journal of cellular and molecular medicine 3 40159625
2025 The tumor suppressor FAT1 controls YAP/TAZ protein degradation and tumor cell proliferation through E3 ligase MIB2. PloS one 2 40478800
2025 Ebola virus VP35 NNLNS motif modulates viral RNA synthesis and MIB2-mediated signaling. bioRxiv : the preprint server for biology 1 40777377
2025 Ebola virus VP35 NNLNS motif modulates viral RNA synthesis and MIB2-mediated signaling. Proceedings of the National Academy of Sciences of the United States of America 1 40982696
2023 MIB2 promotes the progression of non-small cell lung cancer by regulating cell cycle control pathways. Genes & genomics 1 37436668
2025 MIB2-Mediated SUZ12 Ubiquitination Regulates Clonal Proliferation in Patients With Paroxysmal Nocturnal Haemoglobinuria. Journal of cellular and molecular medicine 0 40478202
2024 MIB2 Functions in Oocyte Meiosis by Modulating Chromatin Configuration. Molecular & cellular proteomics : MCP 0 39019259