Affinage

EZHIP

EZH inhibitory protein · UniProt Q86X51

Length
503 aa
Mass
51.9 kDa
Annotated
2026-06-09
26 papers in source corpus 14 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

EZHIP (CXorf67/CATACOMB) is a eutherian PRC2 cofactor that physically associates with the core complex (EZH2, SUZ12, EED) and acts as an endogenous inhibitor of PRC2-mediated H3K27 di/trimethylation (PMID:29909548). Inhibition maps to a short conserved C-terminal peptide containing a single essential methionine that mimics the H3 K27M oncohistone, binds the SET domain of EZH2, and blocks its catalytic activity in vitro and in cells, causing global loss of H3K27me2/3 and de-repression of PRC2 target genes (PMID:30923826, PMID:31281901). EZHIP preferentially engages PRC2 that is allosterically activated by H3K27me3 and impedes its spreading in trans, leaving residual peaks at CpG islands—a mechanism conserved when human EZHIP is expressed in Drosophila (PMID:31086175, PMID:33049227). Physiologically, EZHIP is expressed in the germline and from the maternal mRNA pool in early embryos, where it restrains PRC2 to shape H3K27me2/3 landscapes required for gametogenesis, noncanonical imprinting, X-chromosome inactivation, and parental genome asymmetry; its loss produces hyperactive PRC2, fertility defects, and corrupted imprinting (PMID:31451685, PMID:41118764, PMID:41535302). Aberrant EZHIP re-expression drives global H3K27me3 loss and oncogenic reactivation of developmental programs in posterior fossa ependymoma, diffuse midline glioma, and osteosarcoma (PMID:41204377, PMID:40695784). Beyond its PRC2 role, EZHIP interacts with PALB2 and suppresses homologous-recombination DNA repair, sensitizing high-expressing tumor cells to PARP inhibition (PMID:33186520).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2013 Medium

    Before any function was known, the gene was flagged as a recurrent fusion partner, providing the first link between this X-chromosome locus and cancer.

    Evidence RNA sequencing, FISH, and RT-PCR identifying the MBTD1-CXorf67 fusion in low-grade endometrial stromal sarcoma

    PMID:23959973

    Open questions at the time
    • Functional consequence of the fusion for EZHIP not characterized
    • No connection to PRC2 yet established
  2. 2018 High

    Established that EZHIP physically binds the PRC2 core and functionally antagonizes H3K27me3, defining its molecular activity for the first time.

    Evidence IP-MS in Daoy cells plus reciprocal gain- and loss-of-function with H3K27me3 western readout

    PMID:29909548

    Open questions at the time
    • Inhibitory domain not mapped
    • Mechanism of catalytic inhibition unknown
  3. 2019 High

    Resolved the inhibitory mechanism: a conserved C-terminal peptide with an essential methionine mimics H3 K27M, contacts the EZH2 SET domain, and is necessary and sufficient to block catalysis, with allosteric H3K27me3 activation enhancing inhibition potency.

    Evidence In vitro methyltransferase assays, domain mapping, methionine mutagenesis, and ChIP-seq showing CpG-island retention (three independent studies)

    PMID:30923826 PMID:31086175 PMID:31281901

    Open questions at the time
    • Structural model of the EZHIP-EZH2 contact not resolved
    • Regulation of endogenous EZHIP expression only partly defined
  4. 2019 High

    Defined the physiological role of EZHIP as a germline PRC2 restraint required for fertility, distinguishing its normal function from oncogenic re-expression.

    Evidence Ezhip knockout mice with ChIP-seq, PRC2 complex composition analysis, and reproductive phenotyping

    PMID:31451685

    Open questions at the time
    • How EZHIP limits PRC2-accessory subunit interaction mechanistically unclear
    • Does not address embryonic/imprinting roles
  5. 2020 High

    Demonstrated that EZHIP, like K27M, acts in trans on allosterically activated PRC2 and that the mechanism is conserved across species.

    Evidence Biochemical PRC2 binding assays and ChIP-seq of human EZHIP expressed in Drosophila

    PMID:33049227

    Open questions at the time
    • In vivo stoichiometry of EZHIP versus activated PRC2 not measured
  6. 2020 Medium

    Uncovered a PRC2-independent role: EZHIP binds PALB2 and suppresses homologous recombination, linking its expression to a targetable DNA-repair vulnerability.

    Evidence Co-IP of CXorf67-PALB2, HR repair assays, and PARP inhibitor sensitivity comparisons

    PMID:33186520

    Open questions at the time
    • Single lab, no reciprocal validation
    • Structural basis of PALB2 binding and disruption of PALB2-BRCA2 not defined
  7. 2025 High

    Extended the germline role into embryogenesis, showing maternal EZHIP restrains PRC2 to protect noncanonical imprinting and X-inactivation memories.

    Evidence Maternal Ezhip knockout with allele-specific H3K27me3 and PRC2 ChIP-seq and X-inactivation assays (two studies)

    PMID:41118764 PMID:41535302

    Open questions at the time
    • Mechanism linking PRC2 over-activity to long-term imprint loss incomplete
    • Targets selectively protected versus overwritten not fully cataloged
  8. 2025 Medium

    Broadened the oncogenic picture beyond brain tumors and hinted at PRC2-independent transcriptional/metabolic outputs.

    Evidence Gain-/loss-of-function in osteosarcoma models with ChIP-seq and differentiation assays; transcriptomics and metabolomics in neural models; tumor mutational analysis

    PMID:40695784 PMID:41204377

    Open questions at the time
    • Molecular basis of metabolic reprogramming not dissected
    • Co-expression with H3K27M contradicts earlier mutual-exclusivity assumptions, mechanism unclear
  9. 2025 Low

    Began placing EZHIP's oncogenic effect within conserved chromatin pathways and exploring its regulation by post-translational signaling.

    Evidence Drosophila RNAi modifier screen (preprint) identifying Trithorax/PR-DUB/nucleoporin suppressors; fluorescence screening implicating AMPK and PKC in EZHIP protein stability

    PMID:40502002 PMID:42120298

    Open questions at the time
    • Predicted phosphosites not validated by mutagenesis
    • Screen results from single labs, mechanistic basis of stability control unestablished

Open questions

Synthesis pass · forward-looking unresolved questions
  • How EZHIP protein abundance is controlled post-translationally and how its PRC2-independent functions (PALB2/HR, transcriptional and metabolic reprogramming) are mechanistically wired remain open.
  • No structure of the EZHIP-PRC2 or EZHIP-PALB2 complex
  • Direct phosphosite-to-stability causality not demonstrated
  • Mechanism of non-PRC2 transcriptional/metabolic effects undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 5 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0000228 nuclear chromosome 2 GO:0005634 nucleus 2
Pathway
R-HSA-4839726 Chromatin organization 4 R-HSA-1643685 Disease 2 R-HSA-73894 DNA Repair 1
Complex memberships
PRC2

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2018 CXorf67 (EZHIP) physically interacts with EZH2, SUZ12, and EED — core components of PRC2 — as detected by immunoprecipitation/mass spectrometry in the Daoy cell line. Enforced reduction of CXorf67 in Daoy cells restored H3K27me3 levels, while enforced expression in HEK293T and neural stem cells reduced H3K27me3 levels, establishing CXorf67 as a functional inhibitor of PRC2-mediated H3K27 trimethylation. Immunoprecipitation/mass spectrometry; gain- and loss-of-function experiments (knockdown and overexpression) with western blot readout of H3K27me3 Acta neuropathologica High 29909548
2019 A conserved short peptide sequence in the C-terminal region of EZHIP (CXorf67) that mimics the H3 K27M oncohistone sequence is necessary and sufficient to bind the SET domain of EZH2 and inhibit PRC2 catalytic methyltransferase activity in vitro and in vivo, causing global loss of H3K27me2/3 and de-repression of PRC2 target genes including neurodevelopmental genes. Mass spectrometry; peptide modeling; immunocytochemistry; western blot; in vitro methyltransferase assay; domain mapping Neuro-oncology High 30923826
2019 A conserved sequence in EZHIP directly contacts the active site of EZH2 in a mechanism analogous to H3 K27M. Expression of EZHIP or H3 K27M in cells promotes similar chromatin profiles: loss of broad H3K27me3 domains but retention at CpG islands. H3K27me3-mediated allosteric activation of PRC2 substantially increases the inhibition potency of EZHIP, providing a mechanism for the observed loss of H3K27me3 spreading. In vitro PRC2 catalytic inhibition assay; chromatin profiling (ChIP-seq); cell-based overexpression with H3K27me3 readout; mechanistic dissection of allosteric stimulation Nature communications High 31086175
2019 EZHIP (termed CATACOMB) is a subunit of PRC2 whose interaction with the complex decreases PRC2-dependent H3K27me2/3 deposition. The inhibitory function maps to a short conserved region containing a single methionine residue essential for diminishing H3K27me2/3 levels, analogous to H3K27M. EZHIP expression is regulated through DNA methylation/demethylation, suggesting it acts as an inducible endogenous antagonist of PRC2. Additionally, the study identified JAZF1 as a subunit of NuA4 acetyltransferase complex through biochemical characterization of ESS fusion proteins. Biochemical characterization; co-purification; methyltransferase assays; site-directed mutagenesis of the critical methionine; epigenetic regulation analysis Science advances High 31281901
2019 In mice, EZHIP is predominantly expressed in gonads. Deletion of Ezhip leads to a global increase in H3K27me2/3 during spermatogenesis and at late stages of oocyte maturation. EZHIP limits PRC2 enzymatic activity and lessens the interaction between the core PRC2 complex and its accessory subunits, but does not interfere with PRC2 recruitment to chromatin. Loss of EZHIP is associated with reduced follicles in aging females and strongly impaired fertility in Ezhip−/− females. Mouse knockout (Ezhip deletion); ChIP-seq for H3K27me2/3; biochemical analysis of PRC2 complex composition; reproductive phenotyping Nature communications High 31451685
2020 EZHIP and H3 K27M preferentially interact with PRC2 that is allosterically activated by H3K27me3 (at CpG islands) and impede its spreading in trans. Expression of human EZHIP in Drosophila melanogaster reduces H3K27me3 through a conserved mechanism, demonstrating mechanistic conservation. H3 K27M oncohistones reduce H3K27me3 in trans, independently of their incorporation into chromatin. Biochemical PRC2 binding assays; ChIP-seq in Drosophila expressing human EZHIP; in vivo allosteric activation experiments; domain-specific interaction mapping Molecular cell High 33049227
2020 Elevated CXorf67 (EZHIP) expression suppresses homologous recombination (HR)-mediated DNA repair by interacting with PALB2 and inhibiting the PALB2-BRCA2 interaction, thereby blocking HR repair. Tumor cells with high CXorf67 expression show increased sensitivity to PARP inhibitors. Co-immunoprecipitation demonstrating CXorf67-PALB2 interaction; HR repair assays; PARP inhibitor sensitivity assays in cells with high vs. low CXorf67 expression Cancer cell Medium 33186520
2013 CXorf67 (EZHIP) is identified as the gene on chromosome X involved in a novel reciprocal t(X;17)(p11.2;q21.33) translocation generating the MBTD1-CXorf67 fusion transcript in low-grade endometrial stromal sarcoma, validated by RNA sequencing, RT-PCR, Sanger sequencing, and FISH. Whole-transcriptome paired-end RNA sequencing; FISH; banding cytogenetics; RT-PCR and Sanger sequencing International journal of cancer Medium 23959973
2025 In growing oocytes, PRC2 binds both classic Polycomb targets and noncanonical H3K27me3 domains; EZHIP co-binds with PRC2 and restricts its activity. Knockout of maternal Ezhip causes hyperactive PRC2 that promiscuously deposits H3K27me3 genome-wide, overwriting H3K27me3 memories at noncanonical imprinted genes, causing paradoxical derepression of H3K27me3 targets, defective X chromosome inactivation, diluted chromatin PRC2, and attenuated H3K27me3 restoration at Polycomb targets after implantation. Ezhip knockout in mice; ChIP-seq for H3K27me3 and PRC2 binding; allele-specific analysis of imprinting; X-chromosome inactivation assays Cell stem cell High 41118764
2026 Maternal deletion of Ezhip initially increases the asymmetric distribution of H3K27me3 between parental genomes at the zygotic stage, but subsequently impairs H3K27me3-dependent imprinting and mitigates X-chromosome inactivation in pre-implantation embryos. EZHIP protein, translated from the maternal mRNA pool, is present during the first cell divisions post-fertilization and limits PRC2 enzymatic activity; in its absence, the H3K27me3 landscape is both expanded and flattened, abolishing parental genome asymmetry. Maternal-specific Ezhip knockout in mice; allele-specific H3K27me3 ChIP-seq; immunofluorescence of early embryos; assessment of X-chromosome inactivation Nature communications High 41535302
2025 In a Drosophila model with tissue-specific expression of EZHIP and H3 K27M, a targeted RNAi screen identified genetic modifiers whose knockdown suppressed developmental phenotypes caused by PRC2 inhibition. Strong suppressors included Trithorax-group proteins Ash1 and Trx, the PR-DUB complex member Asx, and the nucleoporin Nup153; suppression correlated with reduced expression of genes aberrantly activated following PRC2 inhibition, placing EZHIP's oncogenic mechanism in the context of conserved chromatin-regulatory pathways. Drosophila tissue-specific expression of human EZHIP; targeted RNAi screen; gene expression analysis (RNA-seq); genetic epistasis bioRxivpreprint Medium 40502002
2025 EZHIP expression in human-derived neural models potentiates neuronal-like gene programs associated with synaptic function and represses methionine and polyamine metabolism, indicating functions beyond PRC2 inhibition. Additionally, EZHIP mutations occur in H3K27M-positive DMG, showing that mutant EZHIP can be co-expressed with the H3K27M oncohistone contrary to earlier assumptions. EZHIP expression in human neural models; transcriptomics (RNA-seq); metabolomics; mutational landscape analysis of pediatric brain tumors Acta neuropathologica communications Medium 41204377
2025 Gain- and loss-of-function experiments demonstrate that EZHIP expression drives oncogenic activity in osteosarcoma in vitro and in vivo, reducing H3K27me3 deposition, reactivating developmental pathways, and impeding mesenchymal progenitor differentiation toward smooth muscle lineage at the expense of other fates. Gain- and loss-of-function (EZHIP overexpression and knockdown); in vitro and in vivo tumor models; ChIP-seq for H3K27me3; differentiation assays; transcriptomics Nature communications Medium 40695784
2026 In silico prediction combined with high-throughput fluorescence-based screening identified that AMPK pathway activation (via biguanides) robustly reduces EZHIP protein abundance and restores H3K27me3 levels independently of cytotoxicity, while PKC activation increases EZHIP protein abundance. This establishes AMPK and PKC as opposing regulators of EZHIP protein stability through post-translational signaling. In silico PTM prediction (PhosphoSitePlus, NetPhos 3.1); HEK293T reporter cell line expressing HA-RFP-EZHIP; fluorescence-based high-throughput screening; western blot; LC50 analysis Brain tumor research and treatment Low 42120298

Source papers

Stage 0 corpus · 26 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2018 Molecular heterogeneity and CXorf67 alterations in posterior fossa group A (PFA) ependymomas. Acta neuropathologica 221 29909548
2019 PFA ependymoma-associated protein EZHIP inhibits PRC2 activity through a H3 K27M-like mechanism. Nature communications 173 31086175
2019 EZHIP/CXorf67 mimics K27M mutated oncohistones and functions as an intrinsic inhibitor of PRC2 function in aggressive posterior fossa ependymoma. Neuro-oncology 122 30923826
2020 H3 K27M and EZHIP Impede H3K27-Methylation Spreading by Inhibiting Allosterically Stimulated PRC2. Molecular cell 119 33049227
2013 Identification of a novel, recurrent MBTD1-CXorf67 fusion in low-grade endometrial stromal sarcoma. International journal of cancer 97 23959973
2019 CATACOMB: An endogenous inducible gene that antagonizes H3K27 methylation activity of Polycomb repressive complex 2 via an H3K27M-like mechanism. Science advances 95 31281901
2019 EZHIP constrains Polycomb Repressive Complex 2 activity in germ cells. Nature communications 90 31451685
2020 Elevated CXorf67 Expression in PFA Ependymomas Suppresses DNA Repair and Sensitizes to PARP Inhibitors. Cancer cell 37 33186520
2021 EZHIP: a new piece of the puzzle towards understanding pediatric posterior fossa ependymoma. Acta neuropathologica 34 34762160
2020 EZH2 inhibitory protein (EZHIP/Cxorf67) expression correlates strongly with H3K27me3 loss in posterior fossa ependymomas and is mutually exclusive with H3K27M mutations. Brain tumor pathology 25 33130928
2005 Isoptericola hypogeus sp. nov., isolated from the Roman catacomb of Domitilla. International journal of systematic and evolutionary microbiology 21 16014507
2007 Amycolatopsis nigrescens sp. nov., an actinomycete isolated from a Roman catacomb. International journal of systematic and evolutionary microbiology 20 17329776
2013 Kribbella albertanoniae sp. nov., isolated from a Roman catacomb, and emended description of the genus Kribbella. International journal of systematic and evolutionary microbiology 14 23584288
2024 EZHIP's role in diffuse midline glioma: echoes of oncohistones? Trends in cancer 11 39343635
2014 Description of Kribbella italica sp. nov., isolated from a Roman catacomb. International journal of systematic and evolutionary microbiology 9 25385996
2025 Aberrant EZHIP expression drives tumorigenesis in osteosarcoma. Nature communications 5 40695784
2023 An EWSR1-EZHIP fusion in a cerebral hemisphere astroblastoma. Neuropathology : official journal of the Japanese Society of Neuropathology 4 36624615
2025 EZHIP restricts noncanonical PRC2 binding and regulates H3K27me3 intergenerational inheritance and reprogramming. Cell stem cell 3 41118764
2025 EZHIP boosts neuronal-like synaptic gene programs and depresses polyamine metabolism. Acta neuropathologica communications 2 41204377
2025 Dynamic evolution of EZHIP, an inhibitor of the Polycomb Repressive Complex 2 in mammals. bioRxiv : the preprint server for biology 1 41427323
2022 [The value of CXorf67 and H3K27me3 for diagnosing germ cell tumors in central nervous system]. Zhonghua bing li xue za zhi = Chinese journal of pathology 1 35511635
2026 H3K27me3-dependent imprinting and transcriptional regulation in early mouse embryos requires EZHIP-mediated restriction of PRC2 activity. Nature communications 0 41535302
2026 EZHIP in Pediatric Brain Tumors: From Epigenetic Mimicry to Therapeutic Vulnerabilities. International journal of molecular sciences 0 41596609
2026 In Silico Prediction of EZHIP Post-Translational Modification Sites and Small-Molecule High-Throughput Screening for Quantitative EZHIP Modulation. Brain tumor research and treatment 0 42120298
2025 Investigating oncoprotein-mediated chromatin dysregulation in Drosophila melanogaster uncovers novel modifiers of the developmental impact of H3 K27M and EZHIP. bioRxiv : the preprint server for biology 0 40502002
2025 CXorf67 in malignancies: Deciphering epigenetic landscapes and clinical implications for precision oncology. Genes & diseases 0 42238311

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