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Showing MPHOSPH8 — MPP8 is a alias.

MPHOSPH8

M-phase phosphoprotein 8 · UniProt Q99549

Length
860 aa
Mass
97.2 kDa
Annotated
2026-06-10
19 papers in source corpus 15 papers cited in narrative 18 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

MPHOSPH8 (MPP8) is a chromodomain-containing epigenetic reader that couples recognition of methylated histone and non-histone marks to transcriptional silencing of target genes and repeated genomic elements (PMID:20871592, PMID:34031396). Its N-terminal chromodomain encloses trimethyl-lysine within a conserved aromatic cage (Phe59, Trp80, Tyr83 plus Asp87) that discriminates H3K9me3 from H3K27 and binds H3K9me2/me3 with sub-micromolar affinity, and the domain forms a domain-swapped homodimer (PMID:22022377, PMID:21419134). Beyond histones, the chromodomain reads methylated marks on silencing-machinery components—Dnmt3a-K44me2, self-methylated GLP, and G9a/GLP-trimethylated ATF7IP—and binds methyltransferase sequences (SETDB1, ATF7IP, G9a, GLP) with affinity comparable to or exceeding H3K9me3, allowing MPP8 to bridge DNMT3A with G9a/GLP and to recruit H3K9 methyltransferases (PMID:22086334, PMID:30286792, PMID:39638237). MPP8 represses the E-cadherin promoter, where it directs DNMT3A-dependent CpG methylation and recruits SIRT1 for H4K16 deacetylation, thereby promoting EMT; SIRT1 reciprocally stabilizes MPP8 by reversing PCAF-catalyzed K439 acetylation that otherwise targets MPP8 for proteasomal degradation (PMID:20871592, PMID:25870236). As a core subunit of the HUSH complex, MPP8 silences LINE-1 elements and proviruses through its unannotated C-terminus—a five-ankyrin-repeat plus PINIT-like fold that engages TASOR—independently of its chromodomain and of detectable chromatin binding (PMID:34031396, PMID:39638237). MPP8 is essential for ground-state pluripotency in mouse ES cells, where its loss causes cell cycle arrest, spontaneous differentiation, and impaired LIF/STAT3 signaling (PMID:34031396, PMID:37626833). Its chromatin association is cell-cycle-regulated: cyclin B1–Cdk1 phosphorylates MPP8 during mitosis to drive its dissociation from chromatin at the metaphase-to-anaphase transition (PMID:23416073).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2010 High

    Established MPP8 as an H3K9 methyl-mark reader that physically links a chromatin signal to DNA methylation, defining its core role as a silencing scaffold.

    Evidence Chromodomain binding assays, ChIP, Co-IP, and knockdown with methylation readout at the E-cadherin promoter

    PMID:20871592

    Open questions at the time
    • Did not resolve the structural basis of methyl-lysine recognition
    • Did not establish whether MPP8 acts within a defined multiprotein complex
  2. 2011 High

    Defined the atomic basis of methyl-lysine discrimination and showed the chromodomain reads methylated non-histone substrates, extending MPP8 reading beyond H3K9.

    Evidence Crystal structures of MPP8 chromodomain with H3K9me3, fluorescence polarization binding, in vitro methylation, and Co-IP for Dnmt3a-K44me2 and self-methylated GLP

    PMID:21419134 PMID:22022377 PMID:22086334

    Open questions at the time
    • Functional importance of chromodomain homodimerization in cells not established
    • Predicted Tyr83 phosphorylation modulating binding not experimentally verified
  3. 2013 High

    Showed MPP8 chromatin association is cell-cycle-controlled by mitotic phosphorylation, revealing dynamic regulation of the silencing reader.

    Evidence In vitro cyclin B1–Cdk1 kinase assay, STA phospho-site mutant, and chromatin fractionation through mitosis

    PMID:23416073

    Open questions at the time
    • The phosphatase reversing this modification is unidentified
    • Functional consequence for silencing of specific target loci not measured
  4. 2013 Medium

    Identified a physical interaction between MPP8 and the mitochondrial peptide Humanin, mapping the reciprocal binding regions.

    Evidence Co-IP, peptide mapping, and deletion analysis localizing the HN-binding site to MPP8 residues 431–560

    PMID:23532874

    Open questions at the time
    • No functional consequence of the interaction established
    • Single lab, no reciprocal or structural validation
  5. 2015 High

    Connected MPP8 to an acetylation-controlled stability switch and to histone deacetylation at target loci, integrating it into EMT regulation.

    Evidence Co-IP, K439 acetylation mutant, ubiquitin-proteasome assay, ChIP, and knockdown with EMT readout for SIRT1/PCAF; Co-IP and knockdown for PRC1 components

    PMID:25660450 PMID:25870236

    Open questions at the time
    • Mechanism by which acetylation triggers degradation not resolved
    • PRC1 interaction lacks structural or reciprocal validation
  6. 2018 High

    Demonstrated that methylation of ATF7IP, not only histones, is read by MPP8 and is required for SETDB1/MPP8 provirus silencing, broadening the methyl-mark reading model.

    Evidence MS substrate screen, in vitro methylation, chromodomain binding, and unmethylatable ATF7IP mutant in a reporter-provirus silencing assay

    PMID:30286792

    Open questions at the time
    • Did not quantify contribution of ATF7IP methylation versus H3K9me at endogenous loci
  7. 2019 Medium

    Showed genome-wide co-occupancy and functional co-regulation of MPP8 with SETDB1, especially at satellite repeats, establishing repeat-element silencing as a shared genomic program.

    Evidence Co-IP, RNA-seq, and ChIP-seq/CUT&RUN co-occupancy analysis in ES cells

    PMID:31557926

    Open questions at the time
    • Directionality of recruitment between MPP8 and SETDB1 not resolved here
    • Single lab
  8. 2021 High

    Revealed that MPP8 represses LINE-1 via the HUSH complex through its C-terminus independently of the chromodomain and detectable chromatin binding, and that MPP8 is essential for pluripotency.

    Evidence Auxin-inducible degron depletion, domain-deletion rescue, ChIP-seq, and RNA-seq in mESCs; chemoproteomics with the chromodomain ligand UNC5246 identifying HRP2

    PMID:34031396 PMID:34415726

    Open questions at the time
    • Structural basis of the C-terminal HUSH interaction not defined here
    • Functional role of HRP2 interaction not characterized
  9. 2023 Medium

    Linked MPP8 to LIF/STAT3 signaling and Nanog expression, connecting its silencing activity to pluripotency-maintaining signaling.

    Evidence miniIAA7 degron depletion with STAT3 reporter, colony formation, and differentiation assays in mESCs

    PMID:37626833

    Open questions at the time
    • Mechanistic link between MPP8 chromatin function and STAT3 activity unresolved
    • Direct versus indirect effect on Nanog not distinguished
  10. 2024 High

    Provided the structural basis for MPP8's chromodomain-independent function, defining the C-terminal ankyrin-PINIT fold that engages TASOR and showing the chromodomain directly binds methyltransferase sequences.

    Evidence Crystal structure of MPP8 CTD, AlphaFold3 modeling of the TASOR interface, interface mutagenesis validated in a HUSH reporter assay, and binding affinity measurements

    PMID:39638237

    Open questions at the time
    • Direct experimental structure of the MPP8 CTD–TASOR complex not solved
    • Stoichiometry of MPP8 within assembled HUSH not defined
  11. 2024 Medium

    Connected HUSH/MPP8 to PRC1.6 occupancy at a subset of silenced genes, indicating cross-talk between repressive complexes.

    Evidence Proximity labeling (C-BERST), forward genetic screen, and ChIP-seq with MPP8 loss-of-function (preprint)

    Open questions at the time
    • Preprint, single lab
    • Whether MPP8 directly recruits PRC1.6 or acts upstream not resolved
  12. 2025 Low

    Extended MPP8/HUSH targets to interferon-stimulated genes and positioned MPP8 as a virally counteracted host restriction factor, implicating it in innate immune gene control.

    Evidence MPP8 depletion with RNA-seq and CUT&Tag in iPSCs for ISG repression; protein degradation and Co-IP with adenoviral E1B-55K/E4orf6 (preprints)

    Open questions at the time
    • Both findings are preprints, single lab
    • Direct ubiquitylation of MPP8 by the viral E3 complex not biochemically defined
    • Mechanism distinguishing direct ISG repression from indirect effects not fully established
  13. 2026 Medium

    Identified a covalent labeling site (C99) adjacent to the methyl-lysine pocket, opening a route to chemical antagonists of the chromodomain.

    Evidence MALDI-TOF covalent fragment screening and glutathione reactivity selectivity assay

    PMID:41621721

    Open questions at the time
    • Effect of C99 labeling on methyl-lysine binding not demonstrated
    • Cellular activity of the fragments not shown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How MPP8's chromodomain-dependent methyl-mark reading and its chromodomain-independent HUSH/TASOR-scaffolding activities are partitioned across different target classes (E-cadherin, satellite repeats, LINE-1, ISGs) remains unresolved.
  • No unified model reconciling chromatin-binding-dependent and -independent silencing
  • Direct MPP8–TASOR complex structure not determined
  • Rules governing locus-specific recruitment unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0042393 histone binding 3 GO:0060090 molecular adaptor activity 3 GO:0140110 transcription regulator activity 3
Localization
GO:0005634 nucleus 3 GO:0005694 chromosome 3
Pathway
R-HSA-4839726 Chromatin organization 3 R-HSA-74160 Gene expression (Transcription) 3 R-HSA-1640170 Cell Cycle 1
Partners
ATF7IPDNMT3AG9AGLPHRP2SETDB1SIRT1TASOR
Complex memberships
HUSH complex

Evidence

Reading pass · 18 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2010 MPP8 chromodomain directly binds methylated H3K9 (H3K9me2/me3) in vivo and in vitro, and MPP8 targets the E-cadherin gene promoter to repress it; knockdown reduces DNMT3A localization at the E-cadherin CpG island, decreasing DNA methylation there. MPP8 also physically interacts with H3K9 methyltransferases GLP and ESET, as well as DNMT3A. Chromodomain binding assays (in vitro and in vivo), ChIP, Co-immunoprecipitation, knockdown with reporter/methylation readout The EMBO journal High 20871592
2011 G9a and GLP dimethylate Dnmt3a at K44 (mouse; equivalent to K47 human DNMT3A); the MPP8 chromodomain specifically recognizes this dimethylated Dnmt3a-K44me2. MPP8 also interacts with self-methylated GLP in a methylation-dependent manner. The MPP8 chromodomain forms a homodimer in solution and in crystals, suggesting a dimeric MPP8 bridges methylated Dnmt3a and GLP to form a Dnmt3a–MPP8–GLP/G9a silencing complex. In vitro methylation assay, crystal structure of MPP8 chromodomain dimer, Co-IP, peptide binding assays Nature communications High 22086334
2011 Crystal structure of human MPP8 chromodomain in complex with H3K9me3 peptide (residues 1–15) reveals a conserved aromatic cage (Phe59, Trp80, Tyr83) plus Asp87 that encloses the trimethyl-lysine, enabling discrimination of H3K9 from H3K27. The chromodomain forms a homodimer via domain-swapping of two β-strands. Modeled phosphorylation of cage residue Tyr83 is predicted to modulate methyl-lysine binding. X-ray crystallography, solution studies (dimerization), peptide binding affinity measurement PloS one High 22022377
2011 Crystal structure of MPP8 chromodomain–H3K9me3 peptide complex defines contacts with at least six H3 residues (Q5–S10); three aromatic residues (Phe59, Trp80, Tyr83) form a partial hydrophobic cage. MPP8 harbors an N-terminal chromodomain and C-terminal ankyrin repeat domain. Binding affinities for H3K9me3 and H3K9me2 are sub-micromolar. X-ray crystallography, fluorescence polarization binding assay Journal of molecular biology High 21419134
2013 MPP8 is phosphorylated by cyclin B1–Cdk1 in vitro and in cells during mitosis; this phosphorylation causes MPP8 to dissociate from chromatin during metaphase-to-anaphase. An MPP8 STA mutant (all Cdk consensus sites substituted to Ala) fails to dissociate from chromatin during early mitosis, demonstrating that Cdk-dependent phosphorylation regulates MPP8 chromatin association. In vitro kinase assay (cyclin B1-Cdk1 + MPP8), site-directed mutagenesis (STA mutant), mitotic kinase inhibitor experiments, chromatin fractionation Biochemical and biophysical research communications High 23416073
2013 The mitochondrial peptide Humanin (HN) physically interacts with MPP8; co-immunoprecipitation confirmed the interaction. The MPP8-binding site on HN maps to residues 5–12, and the HN-binding domain on MPP8 maps to residues 431–560. Co-immunoprecipitation, peptide mapping, deletion analysis Journal of peptide science Medium 23532874
2015 MPP8 physically interacts with SIRT1 deacetylase. SIRT1 antagonizes PCAF-catalyzed acetylation of MPP8 at K439, protecting MPP8 from ubiquitin-proteasome degradation. Conversely, MPP8 recruits SIRT1 to target promoters for H4K16 deacetylation after MPP8 binds methyl-H3K9. Disrupting either MPP8 methyl-H3K9 binding or the SIRT1 interaction de-represses E-cadherin and reduces EMT phenotypes. Co-IP, site-directed mutagenesis (K439 acetylation site), ubiquitin-proteasome assay, ChIP, knockdown with EMT phenotype readout EMBO reports High 25870236
2015 MPP8 physically interacts with PRC1 complex components in co-immunoprecipitation experiments. MPP8 knockdown in HeLa cells de-represses testis-specific genes, and depletion in murine ES cells induces mesoderm differentiation genes (Cdx2, Brachyury). Co-immunoprecipitation, shRNA knockdown with gene expression readout Biochemical and biophysical research communications Medium 25660450
2018 G9a/GLP tri-methylates ATF7IP at an H3K9-like mimic motif in mouse embryonic stem cells; MPP8 recognizes this methylated ATF7IP via its chromodomain. SETDB1/MPP8-mediated reporter-provirus silencing is delayed in mESCs expressing an unmethylatable ATF7IP mutant, implicating ATF7IP methylation in SETDB1/MPP8-mediated transgene silencing. Comprehensive substrate screen (MS-based), in vitro methylation assay, chromodomain binding assay, unmethylatable mutant cell line, reporter-provirus silencing assay Epigenetics & chromatin High 30286792
2019 MPP8 physically interacts with SETDB1 in embryonic stem cells and co-regulates a significant number of common genomic targets, especially satellite DNA repeats, as shown by combined biochemical, transcriptomic, and genomic (ChIP/CUT&RUN) analyses. Co-immunoprecipitation, RNA-seq, ChIP-seq/genomic profiling Genes Medium 31557926
2021 MPP8 is essential for ground-state pluripotency in mESCs; its depletion causes cell cycle arrest and spontaneous differentiation. SETDB1 recruits MPP8 to its genomic target loci. Unexpectedly, MPP8 lacking the chromodomain still efficiently represses LINE-1 elements, while the unannotated C-terminus is essential for function. MPP8 represses LINE1 elements through its association with the HUSH core complex, independently of detectable chromatin binding and maintenance of H3K9me3 levels. Auxin-inducible degron depletion, domain deletion mutants, ChIP-seq, RNA-seq, rescue experiments Nature communications High 34031396
2021 A peptidomimetic ligand (UNC5246) targeting the MPP8 chromodomain was developed; biotinylated UNC5246 in chemoproteomics studies revealed HRP2 (hepatoma-derived growth factor-related protein 2) as a novel MPP8-associated protein. HRP2 was shown to colocalize with MPP8 at the E-cadherin gene locus. One-bead one-compound (OBOC) combinatorial screening, chemoproteomics pulldown, ChIP colocalization ACS chemical biology Medium 34415726
2023 MPP8 regulates the LIF/STAT3 signaling pathway activity and Nanog expression in mESCs. Induced degradation of MPP8 protein impairs mESC proliferation, colony formation, LIF/STAT3 pathway activity, and differentiation capacity. miniIAA7-tagged degron cell lines, auxin-induced degradation, reporter assays for STAT3 activity, colony formation assay Cells Medium 37626833
2024 Crystal structure of the MPP8 C-terminal domain (CTD) reveals five ankyrin repeats followed by a PINIT-domain-like fold. AlphaFold3 modeling predicts the MPP8 CTD interacts with SPOC and novel-fold domains in TASOR; point mutations at these predicted interfaces abolish HUSH-dependent transcriptional repression in a cell-based reporter assay. The MPP8 chromodomain binds sequences in SETDB1, ATF7IP, G9a, and GLP with similar or higher affinity than H3K9me3, suggesting MPP8 recruits H3K9 methyltransferases via its chromodomain. X-ray crystallography (MPP8 CTD), AlphaFold3 structural modeling, site-directed mutagenesis at predicted interfaces, cell-based HUSH reporter assay, binding affinity measurements Journal of molecular biology High 39638237
2026 Covalent fragment screening identified two acrylamide-containing fragments that covalently label MPP8 at cysteine 99 (C99), which is adjacent to the methyl-lysine binding pocket of the chromodomain, providing a site for potential covalent antagonist development. MALDI-TOF mass spectrometry covalent fragment screening, glutathione reactivity assay for selectivity SLAS discovery Medium 41621721
2024 PRC1.6 complex colocalizes with the HUSH complex at active promoters genome-wide; PRC1.6 binding at a subset of HUSH-silenced genes is dependent on the core HUSH component MPP8, as shown by genome-wide chromatin profiling and loss-of-function experiments. Proximity labeling (C-BERST), forward genetic screen, ChIP-seq/genome-wide profiling, MPP8 loss-of-function bioRxivpreprint Medium
2025 In human iPSCs, MPP8 depletion (as a core HUSH component) induces expression of young LINE-1 elements and interferon-stimulated genes (ISGs) directly, without IFN signaling, suggesting MPP8 directly represses ISGs as transcriptional targets at the chromatin level. CUT&Tag confirmed MPP8 enrichment at HUSH-regulated ISGs. MPP8 depletion in iPSCs, RNA-seq, CUT&Tag chromatin profiling bioRxivpreprint Medium
2025 MPP8 is targeted for proteasomal degradation by the adenoviral E3 ubiquitin ligase complex (E1B-55K and E4orf6) during HAdV infection, identifying MPP8 as a host restriction factor for adenovirus that the virus actively counteracts. Protein degradation assays, co-immunoprecipitation with viral proteins, proteasome inhibitor rescue bioRxivpreprint Low

Source papers

Stage 0 corpus · 19 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 MPP8 mediates the interactions between DNA methyltransferase Dnmt3a and H3K9 methyltransferase GLP/G9a. Nature communications 118 22086334
2010 Methyl-H3K9-binding protein MPP8 mediates E-cadherin gene silencing and promotes tumour cell motility and invasion. The EMBO journal 102 20871592
2015 MPP8 and SIRT1 crosstalk in E-cadherin gene silencing and epithelial-mesenchymal transition. EMBO reports 55 25870236
2021 MPP8 is essential for sustaining self-renewal of ground-state pluripotent stem cells. Nature communications 52 34031396
2018 Tri-methylation of ATF7IP by G9a/GLP recruits the chromodomain protein MPP8. Epigenetics & chromatin 50 30286792
2011 Structural basis for specific binding of human MPP8 chromodomain to histone H3 methylated at lysine 9. PloS one 43 22022377
2011 Structural insights for MPP8 chromodomain interaction with histone H3 lysine 9: potential effect of phosphorylation on methyl-lysine binding. Journal of molecular biology 41 21419134
2021 A Peptidomimetic Ligand Targeting the Chromodomain of MPP8 Reveals HRP2's Association with the HUSH Complex. ACS chemical biology 17 34415726
2019 The H3K9 Methylation Writer SETDB1 and its Reader MPP8 Cooperate to Silence Satellite DNA Repeats in Mouse Embryonic Stem Cells. Genes 17 31557926
2018 Knockdown of MPP8 suppresses cell proliferation via regulation of HOXA5 in non-small cell lung cancer cells. Cellular and molecular biology (Noisy-le-Grand, France) 10 29412790
2013 Mitotic phosphorylation of MPP8 by cyclin-dependent kinases regulates chromatin dissociation. Biochemical and biophysical research communications 7 23416073
2015 Physical interaction between MPP8 and PRC1 complex and its implication for regulation of spermatogenesis. Biochemical and biophysical research communications 6 25660450
2013 Humanin binds MPP8: mapping interaction sites of the peptide and protein. Journal of peptide science : an official publication of the European Peptide Society 6 23532874
2021 MPP8 Promotes Proliferation and Restrains Apoptosis in Osteosarcoma by Regulating p38αMAPK Pathway. Technology in cancer research & treatment 3 33596786
2016 Lentivirus-mediated silencing of MPHOSPH8 inhibits MTC proliferation and enhances apoptosis. Oncology letters 3 27313751
2024 Structure and Methyl-lysine Binding Selectivity of the HUSH Complex Subunit MPP8. Journal of molecular biology 2 39638237
2023 MPP8 Governs the Activity of the LIF/STAT3 Pathway and Plays a Crucial Role in the Differentiation of Mouse Embryonic Stem Cells. Cells 2 37626833
2026 Application of a MALDI mass spectrometry assay to identify covalent fragments targeting the methyl-lysine reader protein MPP8. SLAS discovery : advancing life sciences R & D 0 41621721
2021 MPP8 Silences LINE-1 Retrotransposons to Promote Acute Myeloid Leukemia. Cancer discovery 0 33893154

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