{"gene":"SUV39H2","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2000,"finding":"Suv39h2 encodes a histone H3 lysine 9-selective methyltransferase (HMTase) that shares 59% identity with Suv39h1 but differs by the presence of a highly basic N terminus. Immunolocalization during spermatogenesis showed enriched distribution at heterochromatin from leptotene to round spermatid stage, and specific accumulation with sex chromosome chromatin (XY body) undergoing meiotic silencing.","method":"In vitro HMTase activity assay, immunolocalization/immunofluorescence during spermatogenesis, FISH chromosomal mapping","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — enzymatic activity established in vitro, localization confirmed by immunofluorescence in primary spermatogenic cells, replicated in subsequent studies","pmids":["11094092"],"is_preprint":false},{"year":2003,"finding":"Suv39h1 and Suv39h2 govern H3K9 di- and trimethylation at telomeric heterochromatin. Loss of both enzymes (SUV39DN cells) results in reduced di/trimethylated H3K9 and increased monomethylated H3K9 at telomeres, concomitant with reduced binding of HP1 homologs (Cbx1, Cbx3, Cbx5) at telomeres and abnormal telomere elongation.","method":"Chromatin immunoprecipitation (ChIP) in SUV39DN double-knockout primary cells, telomere length analysis","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal ChIP in defined genetic knockout, multiple HP1 proteins examined, phenotype replicated with telomere measurements; independently relevant to Suv39h2 function at heterochromatin","pmids":["14702045"],"is_preprint":false},{"year":2014,"finding":"SUV39H2 recognizes a long substrate motif on histone H3 comprising residues T6–K14, with highly specific readout of R8, S10, T11, and G12. Modification of R8 or phosphorylation of S10/T11 reduces/abolishes activity. The enzyme prefers unmethylated H3K9me0 as substrate over H3K9me1/me2 and introduces the first two methyl groups processively; the trimethylation step is much slower. The N324K missense mutation in the SET domain (causing inherited nasal skin disease in Labrador Retrievers) renders SUV39H2 catalytically inactive and causes slight structural changes detected by circular dichroism.","method":"Peptide SPOT array methylation, in vitro methylation assays with SET domain, circular dichroism spectroscopy, active-site mutagenesis","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple in vitro biochemical assays (SPOT array, kinetic analysis, mutagenesis, CD spectroscopy) in single rigorous study","pmids":["25459750"],"is_preprint":false},{"year":2013,"finding":"A missense variant (c.972T>G, p.N324K) in the catalytically active SET domain of SUV39H2 causes hereditary nasal parakeratosis (HNPK) in Labrador Retrievers with autosomal recessive inheritance. The phenotype reflects delayed terminal differentiation of keratinocytes rather than hyperproliferation, implicating SUV39H2-mediated H3K9 methylation in epigenetic regulation of keratinocyte differentiation.","method":"GWAS, whole genome sequencing, cohort genotyping (>500 dogs), histopathological analysis of epidermis","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic association validated in large cohort with segregation analysis; functional inference from histopathology; catalytic inactivation confirmed biochemically in separate study (PMID:25459750)","pmids":["24098150"],"is_preprint":false},{"year":2015,"finding":"SUV39H2 trimethylates LSD1 on lysine 322 (a non-histone substrate). This methylation suppresses LSD1 polyubiquitination and proteasomal degradation, thereby stabilizing LSD1 protein. SUV39H2 knockdown decreases LSD1 protein levels without affecting LSD1 mRNA, and SUV39H2 overexpression indirectly affects LSD1 target gene expression.","method":"In vitro methylation assay, co-immunoprecipitation, mass spectrometry, siRNA knockdown with protein and mRNA quantification","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro methylation plus knockdown with orthogonal protein/mRNA measurements; single lab","pmids":["26183527"],"is_preprint":false},{"year":2015,"finding":"Alternative splicing of SUV39H2 exon 3 is a determinant of protein stability, sub-nuclear localization, and HMTase activity. Inclusion of exon 3 changes SUV39H2 function, and genome-wide expression analysis showed that the two splice isoforms differentially regulate target gene expression.","method":"RT-PCR isoform analysis across tissues/cell lines, functional assays (stability, nuclear localization by imaging, HMTase activity assay), genome-wide expression profiling","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (splicing, localization, activity, transcriptomics) in single lab study","pmids":["25605796"],"is_preprint":false},{"year":2016,"finding":"SUV39H2 undergoes automethylation at lysine 392 both in vitro and in cells. Automethylation impairs SUV39H2 binding affinity to substrate proteins (histone H3 and LSD1), and hyper-automethylated SUV39H2 shows reduced methyltransferase activity toward these substrates.","method":"In vitro methylation assay, co-immunoprecipitation binding assays, in-cell automethylation detection","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution plus cellular confirmation; single lab, two orthogonal methods","pmids":["26988914"],"is_preprint":false},{"year":2016,"finding":"NEGATIVE FINDING: SUV39H2 (and its homolog SUV39H1) failed to methylate H2AX at K134 or any other lysine in vitro using H2AX protein and peptides under conditions where positive controls were functional. This challenges the prior report that SUV39H2 methylates H2AX-K134 to stimulate γ-H2AX during DNA damage response.","method":"In vitro methylation reactions with H2AX protein and peptides, positive control validation","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — rigorous in vitro biochemical assay with controls; single lab, directly contradicts prior claim","pmids":["27177470"],"is_preprint":false},{"year":2017,"finding":"Suv39h2 binds to the Sirt1 gene promoter in hepatocytes and represses Sirt1 transcription by catalyzing H3K9 trimethylation at that locus. Suv39h2 deficiency normalizes Sirt1 expression, allowing NF-κB/p65 to become hypoacetylated, dampening NF-κB-dependent proinflammatory transcription. In macrophages, Suv39h2-mediated repression of PPARγ transcription favors a proinflammatory M1 phenotype.","method":"ChIP assay at Sirt1 promoter, Suv39h2 knockout mouse model (NASH), gene expression analysis, cell culture knockdown/overexpression","journal":"Hepatology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP at specific promoter plus in vivo KO model; single lab","pmids":["28244120"],"is_preprint":false},{"year":2017,"finding":"Suv39h2 represses SIRT1 expression in hepatocytes by stimulating H3K9 trimethylation at the SIRT1 promoter, contributing to steatosis pathogenesis. This was confirmed in a methionine-and-choline deficient diet mouse model where Suv39h2 KO mice showed improved steatosis and upregulated SIRT1.","method":"ChIP at SIRT1 promoter, Suv39h2 knockout mouse (MCD diet model), qPCR, histological staining","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP at specific locus plus in vivo KO; single lab, corroborates PMID:28244120","pmids":["28232186"],"is_preprint":false},{"year":2018,"finding":"SUV39H2 directly binds to the SLIT1 promoter and suppresses SLIT1 transcription by catalyzing H3K9 trimethylation at that locus in colorectal cancer cells. Rescue assays confirmed SLIT1 can antagonize SUV39H2-driven proliferation and metastasis.","method":"ChIP assay at SLIT1 promoter, siRNA knockdown, overexpression, in vitro and in vivo proliferation/metastasis assays, rescue experiments","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP at specific promoter plus functional rescue assays; single lab","pmids":["29458143"],"is_preprint":false},{"year":2018,"finding":"A series of imidazo[1,2-a]pyridine compounds inhibit SUV39H2 methyltransferase activity in vitro. The compound OTS193320 decreases global H3K9 trimethylation in breast cancer cells and triggers apoptosis. A further optimized compound OTS186935 inhibits tumor growth in xenograft models (MDA-MB-231 and A549) and reduces γ-H2AX levels when combined with doxorubicin.","method":"In vitro methyltransferase inhibition assay, cell viability assay, global H3K9me3 quantification, in vivo xenograft mouse model","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro enzymatic inhibition confirmed plus in vivo efficacy; single lab, multiple cell lines","pmids":["30159125"],"is_preprint":false},{"year":2021,"finding":"A rare loss-of-function variant A211S in SUV39H2 found in ASD individuals shows strongly reduced H3K9 methyltransferase activity in vitro. Suv39h2 KO mice display hyperactivity and reduced behavioral flexibility. Suv39h2 deficiency causes elevated expression of protocadherin β (Pcdhb) cluster genes in embryonic brain due to loss of H3K9me3 at Pcdhb gene promoters, which persists into adulthood in the cerebellum.","method":"In vitro HMTase activity assay of variant protein, Suv39h2 KO mouse behavioral assays, ChIP-seq/ChIP for H3K9me3 at Pcdhb promoters, RNA-seq","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro enzymatic characterization of variant, in vivo KO mouse with behavioral phenotype, ChIP validation of H3K9me3 at specific gene promoters; multiple orthogonal methods in single study","pmids":["34262135"],"is_preprint":false},{"year":2021,"finding":"SUV39H2 maintains epidermal stem and progenitor cells by placing H3K9me3 repressive marks on promoters of genes encoding components of the Wnt/p63/adhesion axis. Loss of SUV39H2 function relieves this repression, causing enhanced Wnt activity that drives premature progenitor cell cycle exit, exhaustion of stem cell growth potential, and compromised epidermal differentiation and genome stability.","method":"Spontaneous loss-of-function dog model (monogenic inheritance), pharmacological Wnt activation in primary keratinocytes (canine, human, mouse), H3K9me3 ChIP at specific promoters, cell cycle and differentiation assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function in vivo model plus ChIP at specific promoters plus pharmacological rescue across three species; multiple orthogonal methods","pmids":["33604655"],"is_preprint":false},{"year":2021,"finding":"SUV39H2 transcript and protein are highly expressed in rat trophoblast stem (TS) cells in the stem state and decline upon differentiation. SUV39H2 knockdown arrests TS cell proliferation and activates trophoblast differentiation. SUV39H2 regulates H3K9 methylation status at loci with differentiation-dependent gene expression. SUV39H2 is a downstream target of caudal type homeobox 2 (CDX2), a master regulator of trophoblast lineage development.","method":"Loss-of-function (siRNA) in rat TS cells and ex vivo blastocysts, H3K9 methylation ChIP at specific loci, ChIP for CDX2 at SUV39H2 locus, differentiation marker assays","journal":"Biochimica et biophysica acta. General subjects","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP at specific loci, defined loss-of-function phenotype, upstream regulator identified; single lab","pmids":["33556426"],"is_preprint":false},{"year":2021,"finding":"In the adult hippocampus, Suv39h1 and Suv39h2 are highly expressed at early neurogenic stages and decline upon differentiation. Pharmacological inhibition (chaetocin) reduces H3K9me3 and decreases neuronal differentiation while increasing proliferation of adult hippocampal progenitors. Retrovirus-mediated knockdown of Suv39h1/2 in newborn cells of adult mouse dentate gyrus impairs neuronal differentiation of progenitor cells.","method":"Pharmacological inhibition (chaetocin), retrovirus-mediated RNAi in adult mouse dentate gyrus, immunohistochemistry for H3K9me3 and differentiation markers","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo retroviral KD plus pharmacological inhibition with defined cellular phenotype; cannot separate Suv39h1 from Suv39h2 contributions completely","pmids":["35096813"],"is_preprint":false},{"year":2021,"finding":"SUV39H2 positively regulates LSD1 expression, and LSD1 in turn negatively regulates CDH1 (E-cadherin) expression in osteosarcoma. SUV39H2 overexpression or LSD1 overexpression promotes EMT (reduced E-cadherin, upregulated Vimentin and N-cadherin) and migration, effects reversed by CDH1 restoration.","method":"Loss- and gain-of-function assays, immunofluorescence for EMT markers, in vivo osteosarcoma mouse model, rescue experiments","journal":"Cancer cell international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional rescue assays show pathway ordering (SUV39H2→LSD1→CDH1) but no direct ChIP or biochemical mechanism for LSD1 regulation shown in this paper; single lab","pmids":["33397384"],"is_preprint":false},{"year":2023,"finding":"SUV39H2 methylates PPP1CA (protein phosphatase 1 catalytic subunit alpha) at K141 (mono-methylation). This methylation disrupts PPP1CA interaction with TFEB, blocking TFEB dephosphorylation and nuclear translocation, leading to autophagy deficiency and NPC senescence. PPP1R9B (a PP1 regulatory subunit) binds PPP1CA and facilitates TFEB targeting, and this interaction is also disrupted by K141 methylation. Proteomic analysis identified SUV39H2 as the writer of this mark.","method":"Proteomic analysis, in vitro methylation assay, co-immunoprecipitation, nuclear translocation assays, autophagy flux assays, cellular senescence assays, in vivo IVD model","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro methylation of non-histone substrate confirmed, co-IP showing disrupted interaction, functional consequence (autophagy/TFEB) established; single lab","pmids":["37605006"],"is_preprint":false},{"year":2023,"finding":"METTL3-mediated m6A modification of SUV39H2 mRNA promotes its stability in an IGF2BP2-dependent manner in gastric cancer cells. SUV39H2 represses DUSP6 transcription via H3K9 trimethylation at the DUSP6 locus, increasing ATM phosphorylation and promoting homologous recombination repair, thereby inhibiting cisplatin sensitivity.","method":"m6A-seq/MeRIP, RNA stability assay, ChIP at DUSP6 locus, ATM phosphorylation assays, HR repair assay, siRNA knockdown, in vivo tumor model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP at specific promoter, m6A mRNA modification mechanism established with IGF2BP2 reader; multiple orthogonal methods; single lab","pmids":["36806557"],"is_preprint":false},{"year":2024,"finding":"Suv39h2 represses Vanin-1 (Vnn1) transcription in hepatocytes exposed to free fatty acids. Hepatocyte-specific Suv39h2 deletion (Suv39h2f/f × Alb-Cre) de-represses Vanin-1, and Vanin-1 knockdown normalizes lipid accumulation in Suv39h2-null hepatocytes, placing the Suv39h2-Vanin-1 axis in hepatic lipid metabolism.","method":"Conditional hepatocyte-specific Suv39h2 KO mouse, RNA-seq, Vanin-1 knockdown rescue assay, lipid accumulation assays","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with organ-specific deletion plus rescue experiment identifying specific downstream target; single lab","pmids":["38401627"],"is_preprint":false},{"year":2025,"finding":"SUV39H2 catalyzes H3K9me3 at viral promoter regions (of ICP0, ICP4, ICP8) of oncolytic HSV-1, repressing viral gene transcription. oHSV-1 infection induces proteasomal degradation of SUV39H2 through viral protein ICP0, relieving this repression and allowing viral replication.","method":"CRISPR/Cas9 genome-wide library screen, ChIP at viral promoters, siRNA knockdown and overexpression functional assays, SUV39H2 inhibitor (OTS186935) in vitro/in vivo, proteasomal pathway inhibition","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide CRISPR screen for initial identification plus ChIP at viral promoters plus ICP0-mediated degradation mechanism; single lab","pmids":["40849299"],"is_preprint":false},{"year":2024,"finding":"In Suv39h2 KO mouse embryonic stem cells, rapid depletion of remaining H3K9me3 KMTs reveals that both passive dilution and active removal contribute to H3K9me3 decay within 12–24 hours. HP1 rapidly dissociates from heterochromatin upon KMT depletion, and a threshold level of HP1 limits pioneer factor binding, chromatin opening, and exit from pluripotency.","method":"Engineered Suv39h2 KO ESCs with auxin-inducible degron for remaining KMTs, ChIP-seq for H3K9me3, ATAC-seq, live imaging of HP1 dynamics, time-course experiments","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — sophisticated engineered system with multiple genomics readouts; preprint, not yet peer-reviewed","pmids":[],"is_preprint":true},{"year":2025,"finding":"At human centromeres, SUV39H1/2 complete H3K9 trimethylation (while SETDB1 is required for H3K9 dimethylation at core centromeres). Depleting all three enzymes results in aberrantly high H3K9me3 driven by G9a/GLP methyltransferases that promiscuously deposit H3K9me3 within the centromere core, causing CENP-A expansion into pericentromeres.","method":"siRNA/CRISPRi depletion of SUV39H1, SUV39H2, and SETDB1; H3K9me ChIP-seq; CENP-A localization assays","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint; SUV39H2 role partially inferred from combined SUV39H1/2 depletion rather than isolated SUV39H2 depletion","pmids":[],"is_preprint":true}],"current_model":"SUV39H2 (KMT1B) is a SET domain-containing histone methyltransferase that di- and tri-methylates H3K9 using a processive mechanism with strict substrate specificity (T6–K14 motif, critical readout of R8/S10/T11/G12), targeting both histone (H3K9) and non-histone substrates (LSD1-K322, PPP1CA-K141); it localizes to heterochromatin and the meiotic XY body, maintains telomeric H3K9me3 and HP1 binding, represses specific gene loci (SLIT1, SIRT1, PPARγ, Pcdhb cluster, Vnn1, DUSP6) via promoter H3K9 trimethylation, undergoes autoregulatory automethylation at K392 that impairs substrate binding, is regulated by alternative splicing of exon 3 (affecting stability, localization, and activity), and has defined roles in heterochromatin maintenance, meiosis, epidermal keratinocyte differentiation (Wnt/p63/adhesion axis), trophoblast stem cell fate, adult hippocampal neurogenesis, and early neurodevelopmental gene regulation relevant to autism-spectrum disorder."},"narrative":{"mechanistic_narrative":"SUV39H2 (KMT1B) is a SET domain histone methyltransferase that establishes and maintains H3K9 di- and trimethylation at heterochromatin, where these marks recruit HP1 proteins and govern chromatin compaction and genome stability [PMID:11094092, PMID:14702045]. The enzyme reads a long H3 substrate motif spanning residues T6–K14, with strict dependence on R8, S10, T11 and G12; it prefers unmodified H3K9 and adds the first two methyl groups processively while trimethylation proceeds slowly, and catalytic competence requires an intact SET-domain active site [PMID:25459750]. At telomeric heterochromatin SUV39H1/H2 loss collapses H3K9me2/me3 into H3K9me1, abolishes HP1 (Cbx1/3/5) binding, and deregulates telomere length [PMID:14702045]; in embryonic stem cells the H3K9me3 it deposits sustains HP1 occupancy that gates pioneer-factor access and exit from pluripotency. SUV39H2 acts as a transcriptional repressor by trimethylating H3K9 at defined promoters, silencing SLIT1 in colorectal cancer [PMID:29458143], SIRT1 and PPARγ in liver and macrophages [PMID:28244120, PMID:28232186], Vnn1 in hepatocytes [PMID:38401627], DUSP6 in gastric cancer [PMID:36806557], and the protocadherin-β (Pcdhb) cluster in developing brain [PMID:34262135]. Beyond histones it methylates non-histone substrates: trimethylation of LSD1-K322 blocks LSD1 polyubiquitination and stabilizes the protein [PMID:26183527], and mono-methylation of PPP1CA-K141 disrupts its interaction with TFEB to impair autophagy [PMID:37605006]. SUV39H2 activity is constrained by autoregulatory automethylation at K392, which weakens substrate binding [PMID:26988914], and is tuned by alternative splicing of exon 3, which alters stability, localization, and activity [PMID:25605796]. Through promoter H3K9 trimethylation SUV39H2 controls cell-fate programs in epidermal stem/progenitor maintenance via the Wnt/p63/adhesion axis [PMID:33604655], trophoblast stem-cell self-renewal downstream of CDX2 [PMID:33556426], and adult hippocampal neuronal differentiation [PMID:35096813]. A catalytically inactivating SET-domain mutation (N324K) causes hereditary nasal parakeratosis in dogs [PMID:24098150], and a loss-of-function variant (A211S) with reduced methyltransferase activity is associated with autism-spectrum disorder, modeled by behavioral and Pcdhb-derepression phenotypes in Suv39h2 knockout mice [PMID:34262135].","teleology":[{"year":2000,"claim":"Established that Suv39h2 is a distinct H3K9-selective methyltransferase enriched at heterochromatin and the meiotic XY body, defining its catalytic identity and chromatin compartment.","evidence":"In vitro HMTase assay and immunolocalization during spermatogenesis, FISH mapping","pmids":["11094092"],"confidence":"High","gaps":["Functional consequence of XY-body localization for meiotic silencing not tested","Distinction of Suv39h2-specific from Suv39h1-redundant roles unresolved"]},{"year":2003,"claim":"Showed that Suv39h1/h2 generate H3K9me2/me3 at telomeres to recruit HP1 and constrain telomere length, linking the enzyme to heterochromatin integrity.","evidence":"Reciprocal ChIP in SUV39DN double-knockout primary cells plus telomere length analysis","pmids":["14702045"],"confidence":"High","gaps":["Cannot separate Suv39h2 from Suv39h1 contribution","Mechanism linking H3K9me loss to telomere elongation not defined"]},{"year":2014,"claim":"Defined the substrate readout and kinetic mechanism of methyl transfer, explaining how SUV39H2 achieves specificity and how a disease mutation abolishes activity.","evidence":"Peptide SPOT arrays, kinetic in vitro methylation, active-site mutagenesis, circular dichroism","pmids":["25459750"],"confidence":"High","gaps":["Structural basis of T6–K14 motif recognition not solved","Crosstalk with S10/T11 phosphorylation in vivo not addressed"]},{"year":2013,"claim":"Linked SUV39H2 catalytic loss to a Mendelian skin-differentiation disease, implicating H3K9 methylation in keratinocyte terminal differentiation.","evidence":"GWAS, whole-genome sequencing, large cohort genotyping, epidermal histopathology in Labrador Retrievers","pmids":["24098150"],"confidence":"Medium","gaps":["Target loci controlling differentiation not identified in this study","Mechanism inferred from histopathology rather than chromatin assays"]},{"year":2015,"claim":"Extended SUV39H2 function to non-histone methylation, showing that LSD1-K322 trimethylation stabilizes LSD1 against proteasomal degradation.","evidence":"In vitro methylation, co-IP, mass spectrometry, siRNA with protein/mRNA quantification","pmids":["26183527"],"confidence":"Medium","gaps":["Reciprocal validation and structural detail of K322 methylation absent","Downstream LSD1 target effects shown only indirectly"]},{"year":2015,"claim":"Demonstrated that exon 3 alternative splicing is a regulatory switch controlling SUV39H2 stability, localization, and activity, diversifying its transcriptional output.","evidence":"Isoform RT-PCR, stability/localization/activity assays, genome-wide expression profiling","pmids":["25605796"],"confidence":"Medium","gaps":["Physiological signals controlling isoform choice unknown","Isoform-specific target loci not mapped"]},{"year":2016,"claim":"Identified an autoregulatory automethylation at K392 that dampens substrate binding, revealing intrinsic negative feedback on the enzyme.","evidence":"In vitro and in-cell automethylation detection, co-IP binding assays","pmids":["26988914"],"confidence":"Medium","gaps":["Stoichiometry and dynamics of K392 automethylation in vivo unknown","Demethylase that reverses the mark not identified"]},{"year":2016,"claim":"Refuted a proposed H2AX-K134 methylation activity, narrowing the confirmed substrate repertoire of SUV39H2.","evidence":"In vitro methylation with H2AX protein/peptides and functional positive controls","pmids":["27177470"],"confidence":"Medium","gaps":["Does not exclude context-dependent or cofactor-requiring methylation in cells","Single-lab negative result"]},{"year":2017,"claim":"Showed SUV39H2 directly represses SIRT1 and PPARγ via promoter H3K9me3, linking it to NF-κB-driven inflammation and hepatic steatosis.","evidence":"Promoter ChIP, Suv39h2 knockout mouse NASH/MCD models, expression analysis","pmids":["28244120","28232186"],"confidence":"Medium","gaps":["Recruitment mechanism to specific promoters unknown","Direct vs secondary effects on NF-κB acetylation not fully separated"]},{"year":2018,"claim":"Established SUV39H2 as a pro-tumorigenic repressor in cancer through promoter H3K9me3 silencing of SLIT1, validated by functional rescue, and identified small-molecule inhibitors.","evidence":"Promoter ChIP, knockdown/overexpression, in vivo proliferation/metastasis and xenograft assays, in vitro inhibitor characterization","pmids":["29458143","30159125"],"confidence":"Medium","gaps":["Inhibitor selectivity over SUV39H1 and other KMTs not fully defined","Recruitment to oncogenic target promoters unexplained"]},{"year":2021,"claim":"Connected SUV39H2 loss-of-function to ASD through behavioral deficits and Pcdhb-cluster derepression, defining a neurodevelopmental gene-regulatory role.","evidence":"Variant HMTase assay, Suv39h2 KO mouse behavior, H3K9me3 ChIP at Pcdhb promoters, RNA-seq","pmids":["34262135"],"confidence":"High","gaps":["Causal link between Pcdhb derepression and behavior not established","Human variant penetrance not assessed"]},{"year":2021,"claim":"Defined SUV39H2 as a maintainer of stem/progenitor fate across epidermis, trophoblast, and adult neurogenesis by repressing differentiation- and Wnt-axis loci through H3K9me3.","evidence":"Loss-of-function dog model, cross-species keratinocyte assays, siRNA in trophoblast stem cells, retroviral RNAi and chaetocin in dentate gyrus, locus-specific ChIP","pmids":["33604655","33556426","35096813"],"confidence":"High","gaps":["Neurogenesis study cannot fully separate Suv39h1 from Suv39h2","Upstream signals deploying SUV39H2 to fate genes incompletely mapped"]},{"year":2023,"claim":"Showed SUV39H2 mono-methylates PPP1CA-K141 to block TFEB dephosphorylation, coupling the enzyme to autophagy and cellular senescence control.","evidence":"Proteomics, in vitro methylation, co-IP, nuclear translocation and autophagy flux assays, in vivo IVD model","pmids":["37605006"],"confidence":"Medium","gaps":["Structural basis and stoichiometry of K141 methylation not resolved","In vivo relevance beyond IVD model untested"]},{"year":2023,"claim":"Placed SUV39H2 within an m6A-regulated axis where it silences DUSP6 to enhance ATM-dependent homologous recombination and chemoresistance.","evidence":"MeRIP-seq, RNA stability, DUSP6 promoter ChIP, ATM phosphorylation and HR repair assays, in vivo tumor model","pmids":["36806557"],"confidence":"Medium","gaps":["Direct mechanism linking DUSP6 repression to ATM activation not detailed","Generality beyond gastric cancer unknown"]},{"year":2025,"claim":"Revealed SUV39H2 as a host antiviral restriction factor that H3K9me3-silences oncolytic HSV-1 promoters, antagonized by ICP0-driven proteasomal degradation.","evidence":"Genome-wide CRISPR screen, viral-promoter ChIP, knockdown/overexpression, inhibitor in vitro/in vivo, proteasome inhibition","pmids":["40849299"],"confidence":"Medium","gaps":["Whether SUV39H2 restricts other viruses untested","Recruitment to viral promoters not mechanistically defined"]},{"year":2025,"claim":"Probed SUV39H2 contribution to centromeric H3K9me3 completion and constraint of CENP-A spreading, refining the heterochromatin-enzyme division of labor.","evidence":"siRNA/CRISPRi depletion of SUV39H1/2 and SETDB1, H3K9me ChIP-seq, CENP-A localization (preprint)","pmids":[],"confidence":"Low","gaps":["SUV39H2-specific role inferred from combined SUV39H1/2 depletion","Preprint, not peer-reviewed"]},{"year":null,"claim":"How SUV39H2 is selectively recruited to its diverse genomic and non-histone targets, and what distinguishes its functions from the highly homologous SUV39H1, remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No defined targeting/recruitment mechanism for specific promoters","No structure of full-length enzyme with substrate","Functional non-redundancy with SUV39H1 not systematically delineated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,2,4,17]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[4,17]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[2]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[8,10,12,18]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,5]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,1,21]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[1,13,21]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[8,10,12,18]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[13,14,15]}],"complexes":[],"partners":["LSD1","PPP1CA","TFEB","PPP1R9B","CBX5","CBX1","CBX3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H5I1","full_name":"Histone-lysine N-methyltransferase SUV39H2","aliases":["Histone H3-K9 methyltransferase 2","H3-K9-HMTase 2","Lysine N-methyltransferase 1B","Suppressor of variegation 3-9 homolog 2","Su(var)3-9 homolog 2"],"length_aa":410,"mass_kda":46.7,"function":"Histone methyltransferase that specifically mediates trimethylation of 'Lys-9' of histone H3 (H3K9me3) using monomethylated H3 'Lys-9' (H3K9me1) as substrate (PubMed:10949293). H3 'Lys-9' trimethylation represents a specific tag for epigenetic transcriptional repression by recruiting HP1 (CBX1, CBX3 and/or CBX5) proteins to methylated histones (PubMed:10949293). Mainly functions in heterochromatin regions, thereby playing a central role in the establishment of constitutive heterochromatin at pericentric and telomere regions (PubMed:10949293). H3 'Lys-9' trimethylation is also required to direct DNA methylation at pericentric repeats (PubMed:10949293). SUV39H2 is targeted to histone H3 via its interaction with RB1 and is involved in many processes, such as cell cycle regulation, transcriptional repression and regulation of telomere length (PubMed:14765126). May participate in regulation of higher-order chromatin organization during spermatogenesis (By similarity). Recruited by the large PER complex to the E-box elements of the circadian target genes such as PER2 itself or PER1, contributes to the conversion of local chromatin to a heterochromatin-like repressive state through H3 'Lys-9' trimethylation (By similarity)","subcellular_location":"Nucleus; Chromosome, centromere","url":"https://www.uniprot.org/uniprotkb/Q9H5I1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SUV39H2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CBX1","stoichiometry":0.2},{"gene":"NUMA1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SUV39H2","total_profiled":1310},"omim":[{"mim_id":"620921","title":"ZINC FINGER PROTEIN 512; ZNF512","url":"https://www.omim.org/entry/620921"},{"mim_id":"617886","title":"ZINC FINGER PROTEIN 512B; ZNF512B","url":"https://www.omim.org/entry/617886"},{"mim_id":"606503","title":"SUV39H2 HISTONE LYSINE METHYLTRANSFERASE; SUV39H2","url":"https://www.omim.org/entry/606503"},{"mim_id":"300254","title":"SUV39H1 HISTONE LYSINE METHYLTRANSFERASE; SUV39H1","url":"https://www.omim.org/entry/300254"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Mitochondria","reliability":"Uncertain"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"testis","ntpm":36.6}],"url":"https://www.proteinatlas.org/search/SUV39H2"},"hgnc":{"alias_symbol":["FLJ23414","KMT1B"],"prev_symbol":[]},"alphafold":{"accession":"Q9H5I1","domains":[{"cath_id":"2.40.50.40","chopping":"34-104_118-138","consensus_level":"high","plddt":94.4467,"start":34,"end":138},{"cath_id":"2.170.270.10","chopping":"152-371","consensus_level":"high","plddt":94.968,"start":152,"end":371}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H5I1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H5I1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H5I1-F1-predicted_aligned_error_v6.png","plddt_mean":89.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SUV39H2","jax_strain_url":"https://www.jax.org/strain/search?query=SUV39H2"},"sequence":{"accession":"Q9H5I1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H5I1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H5I1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H5I1"}},"corpus_meta":[{"pmid":"14702045","id":"PMC_14702045","title":"Epigenetic 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Immunolocalization during spermatogenesis showed enriched distribution at heterochromatin from leptotene to round spermatid stage, and specific accumulation with sex chromosome chromatin (XY body) undergoing meiotic silencing.\",\n      \"method\": \"In vitro HMTase activity assay, immunolocalization/immunofluorescence during spermatogenesis, FISH chromosomal mapping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — enzymatic activity established in vitro, localization confirmed by immunofluorescence in primary spermatogenic cells, replicated in subsequent studies\",\n      \"pmids\": [\"11094092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Suv39h1 and Suv39h2 govern H3K9 di- and trimethylation at telomeric heterochromatin. Loss of both enzymes (SUV39DN cells) results in reduced di/trimethylated H3K9 and increased monomethylated H3K9 at telomeres, concomitant with reduced binding of HP1 homologs (Cbx1, Cbx3, Cbx5) at telomeres and abnormal telomere elongation.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP) in SUV39DN double-knockout primary cells, telomere length analysis\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal ChIP in defined genetic knockout, multiple HP1 proteins examined, phenotype replicated with telomere measurements; independently relevant to Suv39h2 function at heterochromatin\",\n      \"pmids\": [\"14702045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SUV39H2 recognizes a long substrate motif on histone H3 comprising residues T6–K14, with highly specific readout of R8, S10, T11, and G12. Modification of R8 or phosphorylation of S10/T11 reduces/abolishes activity. The enzyme prefers unmethylated H3K9me0 as substrate over H3K9me1/me2 and introduces the first two methyl groups processively; the trimethylation step is much slower. The N324K missense mutation in the SET domain (causing inherited nasal skin disease in Labrador Retrievers) renders SUV39H2 catalytically inactive and causes slight structural changes detected by circular dichroism.\",\n      \"method\": \"Peptide SPOT array methylation, in vitro methylation assays with SET domain, circular dichroism spectroscopy, active-site mutagenesis\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple in vitro biochemical assays (SPOT array, kinetic analysis, mutagenesis, CD spectroscopy) in single rigorous study\",\n      \"pmids\": [\"25459750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A missense variant (c.972T>G, p.N324K) in the catalytically active SET domain of SUV39H2 causes hereditary nasal parakeratosis (HNPK) in Labrador Retrievers with autosomal recessive inheritance. The phenotype reflects delayed terminal differentiation of keratinocytes rather than hyperproliferation, implicating SUV39H2-mediated H3K9 methylation in epigenetic regulation of keratinocyte differentiation.\",\n      \"method\": \"GWAS, whole genome sequencing, cohort genotyping (>500 dogs), histopathological analysis of epidermis\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic association validated in large cohort with segregation analysis; functional inference from histopathology; catalytic inactivation confirmed biochemically in separate study (PMID:25459750)\",\n      \"pmids\": [\"24098150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SUV39H2 trimethylates LSD1 on lysine 322 (a non-histone substrate). This methylation suppresses LSD1 polyubiquitination and proteasomal degradation, thereby stabilizing LSD1 protein. SUV39H2 knockdown decreases LSD1 protein levels without affecting LSD1 mRNA, and SUV39H2 overexpression indirectly affects LSD1 target gene expression.\",\n      \"method\": \"In vitro methylation assay, co-immunoprecipitation, mass spectrometry, siRNA knockdown with protein and mRNA quantification\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro methylation plus knockdown with orthogonal protein/mRNA measurements; single lab\",\n      \"pmids\": [\"26183527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Alternative splicing of SUV39H2 exon 3 is a determinant of protein stability, sub-nuclear localization, and HMTase activity. Inclusion of exon 3 changes SUV39H2 function, and genome-wide expression analysis showed that the two splice isoforms differentially regulate target gene expression.\",\n      \"method\": \"RT-PCR isoform analysis across tissues/cell lines, functional assays (stability, nuclear localization by imaging, HMTase activity assay), genome-wide expression profiling\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (splicing, localization, activity, transcriptomics) in single lab study\",\n      \"pmids\": [\"25605796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SUV39H2 undergoes automethylation at lysine 392 both in vitro and in cells. Automethylation impairs SUV39H2 binding affinity to substrate proteins (histone H3 and LSD1), and hyper-automethylated SUV39H2 shows reduced methyltransferase activity toward these substrates.\",\n      \"method\": \"In vitro methylation assay, co-immunoprecipitation binding assays, in-cell automethylation detection\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution plus cellular confirmation; single lab, two orthogonal methods\",\n      \"pmids\": [\"26988914\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"NEGATIVE FINDING: SUV39H2 (and its homolog SUV39H1) failed to methylate H2AX at K134 or any other lysine in vitro using H2AX protein and peptides under conditions where positive controls were functional. This challenges the prior report that SUV39H2 methylates H2AX-K134 to stimulate γ-H2AX during DNA damage response.\",\n      \"method\": \"In vitro methylation reactions with H2AX protein and peptides, positive control validation\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — rigorous in vitro biochemical assay with controls; single lab, directly contradicts prior claim\",\n      \"pmids\": [\"27177470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Suv39h2 binds to the Sirt1 gene promoter in hepatocytes and represses Sirt1 transcription by catalyzing H3K9 trimethylation at that locus. Suv39h2 deficiency normalizes Sirt1 expression, allowing NF-κB/p65 to become hypoacetylated, dampening NF-κB-dependent proinflammatory transcription. In macrophages, Suv39h2-mediated repression of PPARγ transcription favors a proinflammatory M1 phenotype.\",\n      \"method\": \"ChIP assay at Sirt1 promoter, Suv39h2 knockout mouse model (NASH), gene expression analysis, cell culture knockdown/overexpression\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP at specific promoter plus in vivo KO model; single lab\",\n      \"pmids\": [\"28244120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Suv39h2 represses SIRT1 expression in hepatocytes by stimulating H3K9 trimethylation at the SIRT1 promoter, contributing to steatosis pathogenesis. This was confirmed in a methionine-and-choline deficient diet mouse model where Suv39h2 KO mice showed improved steatosis and upregulated SIRT1.\",\n      \"method\": \"ChIP at SIRT1 promoter, Suv39h2 knockout mouse (MCD diet model), qPCR, histological staining\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP at specific locus plus in vivo KO; single lab, corroborates PMID:28244120\",\n      \"pmids\": [\"28232186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SUV39H2 directly binds to the SLIT1 promoter and suppresses SLIT1 transcription by catalyzing H3K9 trimethylation at that locus in colorectal cancer cells. Rescue assays confirmed SLIT1 can antagonize SUV39H2-driven proliferation and metastasis.\",\n      \"method\": \"ChIP assay at SLIT1 promoter, siRNA knockdown, overexpression, in vitro and in vivo proliferation/metastasis assays, rescue experiments\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP at specific promoter plus functional rescue assays; single lab\",\n      \"pmids\": [\"29458143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A series of imidazo[1,2-a]pyridine compounds inhibit SUV39H2 methyltransferase activity in vitro. The compound OTS193320 decreases global H3K9 trimethylation in breast cancer cells and triggers apoptosis. A further optimized compound OTS186935 inhibits tumor growth in xenograft models (MDA-MB-231 and A549) and reduces γ-H2AX levels when combined with doxorubicin.\",\n      \"method\": \"In vitro methyltransferase inhibition assay, cell viability assay, global H3K9me3 quantification, in vivo xenograft mouse model\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro enzymatic inhibition confirmed plus in vivo efficacy; single lab, multiple cell lines\",\n      \"pmids\": [\"30159125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A rare loss-of-function variant A211S in SUV39H2 found in ASD individuals shows strongly reduced H3K9 methyltransferase activity in vitro. Suv39h2 KO mice display hyperactivity and reduced behavioral flexibility. Suv39h2 deficiency causes elevated expression of protocadherin β (Pcdhb) cluster genes in embryonic brain due to loss of H3K9me3 at Pcdhb gene promoters, which persists into adulthood in the cerebellum.\",\n      \"method\": \"In vitro HMTase activity assay of variant protein, Suv39h2 KO mouse behavioral assays, ChIP-seq/ChIP for H3K9me3 at Pcdhb promoters, RNA-seq\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro enzymatic characterization of variant, in vivo KO mouse with behavioral phenotype, ChIP validation of H3K9me3 at specific gene promoters; multiple orthogonal methods in single study\",\n      \"pmids\": [\"34262135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SUV39H2 maintains epidermal stem and progenitor cells by placing H3K9me3 repressive marks on promoters of genes encoding components of the Wnt/p63/adhesion axis. Loss of SUV39H2 function relieves this repression, causing enhanced Wnt activity that drives premature progenitor cell cycle exit, exhaustion of stem cell growth potential, and compromised epidermal differentiation and genome stability.\",\n      \"method\": \"Spontaneous loss-of-function dog model (monogenic inheritance), pharmacological Wnt activation in primary keratinocytes (canine, human, mouse), H3K9me3 ChIP at specific promoters, cell cycle and differentiation assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function in vivo model plus ChIP at specific promoters plus pharmacological rescue across three species; multiple orthogonal methods\",\n      \"pmids\": [\"33604655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SUV39H2 transcript and protein are highly expressed in rat trophoblast stem (TS) cells in the stem state and decline upon differentiation. SUV39H2 knockdown arrests TS cell proliferation and activates trophoblast differentiation. SUV39H2 regulates H3K9 methylation status at loci with differentiation-dependent gene expression. SUV39H2 is a downstream target of caudal type homeobox 2 (CDX2), a master regulator of trophoblast lineage development.\",\n      \"method\": \"Loss-of-function (siRNA) in rat TS cells and ex vivo blastocysts, H3K9 methylation ChIP at specific loci, ChIP for CDX2 at SUV39H2 locus, differentiation marker assays\",\n      \"journal\": \"Biochimica et biophysica acta. General subjects\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP at specific loci, defined loss-of-function phenotype, upstream regulator identified; single lab\",\n      \"pmids\": [\"33556426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In the adult hippocampus, Suv39h1 and Suv39h2 are highly expressed at early neurogenic stages and decline upon differentiation. Pharmacological inhibition (chaetocin) reduces H3K9me3 and decreases neuronal differentiation while increasing proliferation of adult hippocampal progenitors. Retrovirus-mediated knockdown of Suv39h1/2 in newborn cells of adult mouse dentate gyrus impairs neuronal differentiation of progenitor cells.\",\n      \"method\": \"Pharmacological inhibition (chaetocin), retrovirus-mediated RNAi in adult mouse dentate gyrus, immunohistochemistry for H3K9me3 and differentiation markers\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo retroviral KD plus pharmacological inhibition with defined cellular phenotype; cannot separate Suv39h1 from Suv39h2 contributions completely\",\n      \"pmids\": [\"35096813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SUV39H2 positively regulates LSD1 expression, and LSD1 in turn negatively regulates CDH1 (E-cadherin) expression in osteosarcoma. SUV39H2 overexpression or LSD1 overexpression promotes EMT (reduced E-cadherin, upregulated Vimentin and N-cadherin) and migration, effects reversed by CDH1 restoration.\",\n      \"method\": \"Loss- and gain-of-function assays, immunofluorescence for EMT markers, in vivo osteosarcoma mouse model, rescue experiments\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional rescue assays show pathway ordering (SUV39H2→LSD1→CDH1) but no direct ChIP or biochemical mechanism for LSD1 regulation shown in this paper; single lab\",\n      \"pmids\": [\"33397384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SUV39H2 methylates PPP1CA (protein phosphatase 1 catalytic subunit alpha) at K141 (mono-methylation). This methylation disrupts PPP1CA interaction with TFEB, blocking TFEB dephosphorylation and nuclear translocation, leading to autophagy deficiency and NPC senescence. PPP1R9B (a PP1 regulatory subunit) binds PPP1CA and facilitates TFEB targeting, and this interaction is also disrupted by K141 methylation. Proteomic analysis identified SUV39H2 as the writer of this mark.\",\n      \"method\": \"Proteomic analysis, in vitro methylation assay, co-immunoprecipitation, nuclear translocation assays, autophagy flux assays, cellular senescence assays, in vivo IVD model\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro methylation of non-histone substrate confirmed, co-IP showing disrupted interaction, functional consequence (autophagy/TFEB) established; single lab\",\n      \"pmids\": [\"37605006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"METTL3-mediated m6A modification of SUV39H2 mRNA promotes its stability in an IGF2BP2-dependent manner in gastric cancer cells. SUV39H2 represses DUSP6 transcription via H3K9 trimethylation at the DUSP6 locus, increasing ATM phosphorylation and promoting homologous recombination repair, thereby inhibiting cisplatin sensitivity.\",\n      \"method\": \"m6A-seq/MeRIP, RNA stability assay, ChIP at DUSP6 locus, ATM phosphorylation assays, HR repair assay, siRNA knockdown, in vivo tumor model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP at specific promoter, m6A mRNA modification mechanism established with IGF2BP2 reader; multiple orthogonal methods; single lab\",\n      \"pmids\": [\"36806557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Suv39h2 represses Vanin-1 (Vnn1) transcription in hepatocytes exposed to free fatty acids. Hepatocyte-specific Suv39h2 deletion (Suv39h2f/f × Alb-Cre) de-represses Vanin-1, and Vanin-1 knockdown normalizes lipid accumulation in Suv39h2-null hepatocytes, placing the Suv39h2-Vanin-1 axis in hepatic lipid metabolism.\",\n      \"method\": \"Conditional hepatocyte-specific Suv39h2 KO mouse, RNA-seq, Vanin-1 knockdown rescue assay, lipid accumulation assays\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with organ-specific deletion plus rescue experiment identifying specific downstream target; single lab\",\n      \"pmids\": [\"38401627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SUV39H2 catalyzes H3K9me3 at viral promoter regions (of ICP0, ICP4, ICP8) of oncolytic HSV-1, repressing viral gene transcription. oHSV-1 infection induces proteasomal degradation of SUV39H2 through viral protein ICP0, relieving this repression and allowing viral replication.\",\n      \"method\": \"CRISPR/Cas9 genome-wide library screen, ChIP at viral promoters, siRNA knockdown and overexpression functional assays, SUV39H2 inhibitor (OTS186935) in vitro/in vivo, proteasomal pathway inhibition\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide CRISPR screen for initial identification plus ChIP at viral promoters plus ICP0-mediated degradation mechanism; single lab\",\n      \"pmids\": [\"40849299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In Suv39h2 KO mouse embryonic stem cells, rapid depletion of remaining H3K9me3 KMTs reveals that both passive dilution and active removal contribute to H3K9me3 decay within 12–24 hours. HP1 rapidly dissociates from heterochromatin upon KMT depletion, and a threshold level of HP1 limits pioneer factor binding, chromatin opening, and exit from pluripotency.\",\n      \"method\": \"Engineered Suv39h2 KO ESCs with auxin-inducible degron for remaining KMTs, ChIP-seq for H3K9me3, ATAC-seq, live imaging of HP1 dynamics, time-course experiments\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — sophisticated engineered system with multiple genomics readouts; preprint, not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"At human centromeres, SUV39H1/2 complete H3K9 trimethylation (while SETDB1 is required for H3K9 dimethylation at core centromeres). Depleting all three enzymes results in aberrantly high H3K9me3 driven by G9a/GLP methyltransferases that promiscuously deposit H3K9me3 within the centromere core, causing CENP-A expansion into pericentromeres.\",\n      \"method\": \"siRNA/CRISPRi depletion of SUV39H1, SUV39H2, and SETDB1; H3K9me ChIP-seq; CENP-A localization assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint; SUV39H2 role partially inferred from combined SUV39H1/2 depletion rather than isolated SUV39H2 depletion\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"SUV39H2 (KMT1B) is a SET domain-containing histone methyltransferase that di- and tri-methylates H3K9 using a processive mechanism with strict substrate specificity (T6–K14 motif, critical readout of R8/S10/T11/G12), targeting both histone (H3K9) and non-histone substrates (LSD1-K322, PPP1CA-K141); it localizes to heterochromatin and the meiotic XY body, maintains telomeric H3K9me3 and HP1 binding, represses specific gene loci (SLIT1, SIRT1, PPARγ, Pcdhb cluster, Vnn1, DUSP6) via promoter H3K9 trimethylation, undergoes autoregulatory automethylation at K392 that impairs substrate binding, is regulated by alternative splicing of exon 3 (affecting stability, localization, and activity), and has defined roles in heterochromatin maintenance, meiosis, epidermal keratinocyte differentiation (Wnt/p63/adhesion axis), trophoblast stem cell fate, adult hippocampal neurogenesis, and early neurodevelopmental gene regulation relevant to autism-spectrum disorder.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SUV39H2 (KMT1B) is a SET domain histone methyltransferase that establishes and maintains H3K9 di- and trimethylation at heterochromatin, where these marks recruit HP1 proteins and govern chromatin compaction and genome stability [#0, #1]. The enzyme reads a long H3 substrate motif spanning residues T6\\u2013K14, with strict dependence on R8, S10, T11 and G12; it prefers unmodified H3K9 and adds the first two methyl groups processively while trimethylation proceeds slowly, and catalytic competence requires an intact SET-domain active site [#2]. At telomeric heterochromatin SUV39H1/H2 loss collapses H3K9me2/me3 into H3K9me1, abolishes HP1 (Cbx1/3/5) binding, and deregulates telomere length [#1]; in embryonic stem cells the H3K9me3 it deposits sustains HP1 occupancy that gates pioneer-factor access and exit from pluripotency [#21]. SUV39H2 acts as a transcriptional repressor by trimethylating H3K9 at defined promoters, silencing SLIT1 in colorectal cancer [#10], SIRT1 and PPAR\\u03b3 in liver and macrophages [#8, #9], Vnn1 in hepatocytes [#19], DUSP6 in gastric cancer [#18], and the protocadherin-\\u03b2 (Pcdhb) cluster in developing brain [#12]. Beyond histones it methylates non-histone substrates: trimethylation of LSD1-K322 blocks LSD1 polyubiquitination and stabilizes the protein [#4], and mono-methylation of PPP1CA-K141 disrupts its interaction with TFEB to impair autophagy [#17]. SUV39H2 activity is constrained by autoregulatory automethylation at K392, which weakens substrate binding [#6], and is tuned by alternative splicing of exon 3, which alters stability, localization, and activity [#5]. Through promoter H3K9 trimethylation SUV39H2 controls cell-fate programs in epidermal stem/progenitor maintenance via the Wnt/p63/adhesion axis [#13], trophoblast stem-cell self-renewal downstream of CDX2 [#14], and adult hippocampal neuronal differentiation [#15]. A catalytically inactivating SET-domain mutation (N324K) causes hereditary nasal parakeratosis in dogs [#3], and a loss-of-function variant (A211S) with reduced methyltransferase activity is associated with autism-spectrum disorder, modeled by behavioral and Pcdhb-derepression phenotypes in Suv39h2 knockout mice [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that Suv39h2 is a distinct H3K9-selective methyltransferase enriched at heterochromatin and the meiotic XY body, defining its catalytic identity and chromatin compartment.\",\n      \"evidence\": \"In vitro HMTase assay and immunolocalization during spermatogenesis, FISH mapping\",\n      \"pmids\": [\"11094092\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of XY-body localization for meiotic silencing not tested\", \"Distinction of Suv39h2-specific from Suv39h1-redundant roles unresolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed that Suv39h1/h2 generate H3K9me2/me3 at telomeres to recruit HP1 and constrain telomere length, linking the enzyme to heterochromatin integrity.\",\n      \"evidence\": \"Reciprocal ChIP in SUV39DN double-knockout primary cells plus telomere length analysis\",\n      \"pmids\": [\"14702045\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cannot separate Suv39h2 from Suv39h1 contribution\", \"Mechanism linking H3K9me loss to telomere elongation not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the substrate readout and kinetic mechanism of methyl transfer, explaining how SUV39H2 achieves specificity and how a disease mutation abolishes activity.\",\n      \"evidence\": \"Peptide SPOT arrays, kinetic in vitro methylation, active-site mutagenesis, circular dichroism\",\n      \"pmids\": [\"25459750\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of T6\\u2013K14 motif recognition not solved\", \"Crosstalk with S10/T11 phosphorylation in vivo not addressed\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked SUV39H2 catalytic loss to a Mendelian skin-differentiation disease, implicating H3K9 methylation in keratinocyte terminal differentiation.\",\n      \"evidence\": \"GWAS, whole-genome sequencing, large cohort genotyping, epidermal histopathology in Labrador Retrievers\",\n      \"pmids\": [\"24098150\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Target loci controlling differentiation not identified in this study\", \"Mechanism inferred from histopathology rather than chromatin assays\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended SUV39H2 function to non-histone methylation, showing that LSD1-K322 trimethylation stabilizes LSD1 against proteasomal degradation.\",\n      \"evidence\": \"In vitro methylation, co-IP, mass spectrometry, siRNA with protein/mRNA quantification\",\n      \"pmids\": [\"26183527\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reciprocal validation and structural detail of K322 methylation absent\", \"Downstream LSD1 target effects shown only indirectly\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated that exon 3 alternative splicing is a regulatory switch controlling SUV39H2 stability, localization, and activity, diversifying its transcriptional output.\",\n      \"evidence\": \"Isoform RT-PCR, stability/localization/activity assays, genome-wide expression profiling\",\n      \"pmids\": [\"25605796\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological signals controlling isoform choice unknown\", \"Isoform-specific target loci not mapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified an autoregulatory automethylation at K392 that dampens substrate binding, revealing intrinsic negative feedback on the enzyme.\",\n      \"evidence\": \"In vitro and in-cell automethylation detection, co-IP binding assays\",\n      \"pmids\": [\"26988914\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and dynamics of K392 automethylation in vivo unknown\", \"Demethylase that reverses the mark not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Refuted a proposed H2AX-K134 methylation activity, narrowing the confirmed substrate repertoire of SUV39H2.\",\n      \"evidence\": \"In vitro methylation with H2AX protein/peptides and functional positive controls\",\n      \"pmids\": [\"27177470\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not exclude context-dependent or cofactor-requiring methylation in cells\", \"Single-lab negative result\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Showed SUV39H2 directly represses SIRT1 and PPAR\\u03b3 via promoter H3K9me3, linking it to NF-\\u03baB-driven inflammation and hepatic steatosis.\",\n      \"evidence\": \"Promoter ChIP, Suv39h2 knockout mouse NASH/MCD models, expression analysis\",\n      \"pmids\": [\"28244120\", \"28232186\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Recruitment mechanism to specific promoters unknown\", \"Direct vs secondary effects on NF-\\u03baB acetylation not fully separated\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established SUV39H2 as a pro-tumorigenic repressor in cancer through promoter H3K9me3 silencing of SLIT1, validated by functional rescue, and identified small-molecule inhibitors.\",\n      \"evidence\": \"Promoter ChIP, knockdown/overexpression, in vivo proliferation/metastasis and xenograft assays, in vitro inhibitor characterization\",\n      \"pmids\": [\"29458143\", \"30159125\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Inhibitor selectivity over SUV39H1 and other KMTs not fully defined\", \"Recruitment to oncogenic target promoters unexplained\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Connected SUV39H2 loss-of-function to ASD through behavioral deficits and Pcdhb-cluster derepression, defining a neurodevelopmental gene-regulatory role.\",\n      \"evidence\": \"Variant HMTase assay, Suv39h2 KO mouse behavior, H3K9me3 ChIP at Pcdhb promoters, RNA-seq\",\n      \"pmids\": [\"34262135\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal link between Pcdhb derepression and behavior not established\", \"Human variant penetrance not assessed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined SUV39H2 as a maintainer of stem/progenitor fate across epidermis, trophoblast, and adult neurogenesis by repressing differentiation- and Wnt-axis loci through H3K9me3.\",\n      \"evidence\": \"Loss-of-function dog model, cross-species keratinocyte assays, siRNA in trophoblast stem cells, retroviral RNAi and chaetocin in dentate gyrus, locus-specific ChIP\",\n      \"pmids\": [\"33604655\", \"33556426\", \"35096813\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Neurogenesis study cannot fully separate Suv39h1 from Suv39h2\", \"Upstream signals deploying SUV39H2 to fate genes incompletely mapped\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed SUV39H2 mono-methylates PPP1CA-K141 to block TFEB dephosphorylation, coupling the enzyme to autophagy and cellular senescence control.\",\n      \"evidence\": \"Proteomics, in vitro methylation, co-IP, nuclear translocation and autophagy flux assays, in vivo IVD model\",\n      \"pmids\": [\"37605006\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis and stoichiometry of K141 methylation not resolved\", \"In vivo relevance beyond IVD model untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed SUV39H2 within an m6A-regulated axis where it silences DUSP6 to enhance ATM-dependent homologous recombination and chemoresistance.\",\n      \"evidence\": \"MeRIP-seq, RNA stability, DUSP6 promoter ChIP, ATM phosphorylation and HR repair assays, in vivo tumor model\",\n      \"pmids\": [\"36806557\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism linking DUSP6 repression to ATM activation not detailed\", \"Generality beyond gastric cancer unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed SUV39H2 as a host antiviral restriction factor that H3K9me3-silences oncolytic HSV-1 promoters, antagonized by ICP0-driven proteasomal degradation.\",\n      \"evidence\": \"Genome-wide CRISPR screen, viral-promoter ChIP, knockdown/overexpression, inhibitor in vitro/in vivo, proteasome inhibition\",\n      \"pmids\": [\"40849299\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether SUV39H2 restricts other viruses untested\", \"Recruitment to viral promoters not mechanistically defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Probed SUV39H2 contribution to centromeric H3K9me3 completion and constraint of CENP-A spreading, refining the heterochromatin-enzyme division of labor.\",\n      \"evidence\": \"siRNA/CRISPRi depletion of SUV39H1/2 and SETDB1, H3K9me ChIP-seq, CENP-A localization (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"SUV39H2-specific role inferred from combined SUV39H1/2 depletion\", \"Preprint, not peer-reviewed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SUV39H2 is selectively recruited to its diverse genomic and non-histone targets, and what distinguishes its functions from the highly homologous SUV39H1, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No defined targeting/recruitment mechanism for specific promoters\", \"No structure of full-length enzyme with substrate\", \"Functional non-redundancy with SUV39H1 not systematically delineated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 2, 4, 17]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [4, 17]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [8, 10, 12, 18]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 1, 21]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [1, 13, 21]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [8, 10, 12, 18]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [13, 14, 15]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"LSD1\", \"PPP1CA\", \"TFEB\", \"PPP1R9B\", \"CBX5\", \"CBX1\", \"CBX3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}