{"gene":"ING2","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2006,"finding":"The PHD domain of ING2 binds specifically and with high affinity to trimethylated and dimethylated histone H3 lysine 4 (H3K4me3/me2), functioning as an effector module for this histone mark. In response to DNA damage, this interaction stabilizes the mSin3a-HDAC1 repressive complex at promoters of proliferation genes, constituting a mechanism by which H3K4me3 drives active gene repression. Mutations disrupting H3K4me3 binding abolish ING2-mediated cellular responses to genotoxic insults.","method":"Biochemical binding assays, ChIP, loss-of-function mutagenesis, co-immunoprecipitation, cellular DNA damage response assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (binding assays, ChIP, mutagenesis, cellular phenotype), replicated by structural study in the same issue","pmids":["16728974"],"is_preprint":false},{"year":2006,"finding":"Crystal structure (2.0 Å) of the mouse ING2 PHD finger in complex with H3K4me3 peptide revealed that the trimethylammonium group of Lys4 is recognized by aromatic residues Y215 and W238 in a deep binding groove, with additional hydrogen-bonding contacts to Ala1, Arg2, Thr3, and Thr6 of the histone tail. Substitution of binding-site residues disrupts H3K4me3 interaction in vitro and impairs ING2-induced apoptosis in vivo.","method":"X-ray crystallography (2.0 Å resolution), in vitro binding assays, site-directed mutagenesis, apoptosis assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution structure with functional mutagenesis validation, independently corroborated by companion paper","pmids":["16728977"],"is_preprint":false},{"year":2003,"finding":"The PHD finger of ING2 binds phosphoinositides in vitro, including phosphatidylinositol 5-phosphate (PtdIns(5)P). The ING2 PHD finger interacts with PtdIns(5)P in vivo in the nucleus, and this interaction regulates the ability of ING2 to activate p53 and p53-dependent apoptotic pathways in response to DNA damage.","method":"In vitro lipid-binding assays, in vivo interaction studies, p53 transcriptional assays, apoptosis assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro biochemical assays plus in vivo functional validation with multiple readouts in a single rigorous study","pmids":["12859901"],"is_preprint":false},{"year":2001,"finding":"ING2 (p33ING2) negatively regulates cell growth in a p53-dependent manner and enhances p53 transcriptional activity. ING2 expression increases acetylation of p53 at Lys-382, indicating ING2 promotes p53 acetylation as part of its tumor suppressive function. ING2 is induced by DNA-damaging agents etoposide and neocarzinostatin.","method":"Cell proliferation assays, p53 transactivation reporter assays, Western blot for p53 acetylation, siRNA knockdown, overexpression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple cellular assays in one study, single lab, acetylation shown by Western blot","pmids":["11481424"],"is_preprint":false},{"year":2005,"finding":"ING2 forms a complex with p53 and the histone acetyltransferase p300, enhances the interaction between p53 and p300, and acts as a cofactor for p300-mediated p53 acetylation. ING2-mediated p300-dependent p53 acetylation triggers replicative senescence; overexpression induces senescence in young fibroblasts in a p53-dependent manner, and siRNA knockdown of ING2 delays senescence onset.","method":"Co-immunoprecipitation, siRNA knockdown, overexpression, senescence assays, colocalization studies","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP showing ternary complex, functional rescue/knockdown with defined phenotype, single lab","pmids":["16024799"],"is_preprint":false},{"year":2010,"finding":"Treatment with the HDAC inhibitor SAHA causes dissociation of the ING2 subunit (via its PHD finger) from the Sin3 deacetylase complex. Loss of ING2 from the complex disrupts in vivo binding of the Sin3 complex to the p21 promoter, revealing a molecular mechanism by which HDAC inhibitors disrupt deacetylase function at target gene promoters.","method":"Mass spectrometry-based proteomics, Co-IP, ChIP at p21 promoter, pharmacological treatment with SAHA","journal":"Chemistry & biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based complex analysis plus ChIP, single lab, two orthogonal methods","pmids":["20142042"],"is_preprint":false},{"year":2006,"finding":"ING2 enhances nucleotide excision repair of UV-induced DNA damage in a p53-dependent manner. ING2 is required for UV-induced histone H4 acetylation, chromatin relaxation, and recruitment of the damage-recognition protein XPA to photolesions. Knockdown of ING2 completely abolishes NER, demonstrating that physiological ING2 levels are required for this process.","method":"Host-cell reactivation assay, siRNA knockdown, histone acetylation assays, chromatin accessibility assays, XPA recruitment by immunofluorescence","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional NER assay with knockdown and overexpression, chromatin readout, single lab","pmids":["16488987"],"is_preprint":false},{"year":2006,"finding":"The leucine zipper-like (LZL) motif in the N-terminus of ING2 is critical for DNA repair, apoptosis, and chromatin remodeling after UV irradiation. Deletion of the LZL domain abrogates the association between ING2 and p53, but not between ING2 and p300, indicating ING2 functions as a scaffold mediating p53-p300 interaction.","method":"Domain deletion mutagenesis, Co-immunoprecipitation, apoptosis assays, NER assays","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — structure-function by deletion mapping plus co-IP and cellular phenotype assays, single lab","pmids":["16782091"],"is_preprint":false},{"year":2010,"finding":"The HECT-type ubiquitin ligase Smurf1 interacts with ING2 and targets it for polyubiquitination and proteasomal degradation. The catalytic HECT domain of Smurf1 mediates ING2 binding, and the C-terminal PHD domain of ING2 is required for Smurf1-mediated degradation.","method":"Co-immunoprecipitation, ubiquitination assays, proteasome inhibitor experiments, domain mapping","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP plus ubiquitination assay with domain mapping, single lab","pmids":["20621832"],"is_preprint":false},{"year":2013,"finding":"Nuclear phosphatidylinositol-5-phosphate (PtdIns(5)P) directly associates with ING2 and is required for ING2 occupancy at a subset of genomic target promoters in response to DNA damage. PtdIns(5)P acts as a sub-nuclear trafficking factor stabilizing ING2 at discrete chromatin sites; depletion of PtdIns(5)P attenuates ING2-mediated gene repression at these targets.","method":"ChIP, PtdIns(5)P depletion, gene expression analysis, lipid-binding assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP with lipid manipulation and gene expression readouts, single lab, two orthogonal approaches","pmids":["23823870"],"is_preprint":false},{"year":2008,"finding":"ING2 promotes TGF-β-induced transcription and cell cycle arrest. ING2 interacts with the transcriptional modulator SnoN, and together they form a complex with Smad2. Knockdown of SnoN blocks ING2-dependent TGF-β transcription, while SnoN expression augments it, placing ING2 in the TGF-β-Smad signaling pathway as a co-activator.","method":"Co-immunoprecipitation, RNA interference, overexpression, transcriptional reporter assays, cell cycle analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP showing ternary complex, RNAi epistasis, reporter assays, single lab","pmids":["18334480"],"is_preprint":false},{"year":2009,"finding":"ING2 interacts with PCNA (proliferating cell nuclear antigen) and regulates the amount of PCNA associated with chromatin, thereby controlling DNA replication fork progression. siRNA-mediated knockdown of ING2 markedly reduces global replication rate (DNA fiber spreading), causes endoreduplication, and increases sister chromatid exchange frequency, demonstrating a role for ING2 in maintaining genome stability.","method":"Co-immunoprecipitation, DNA fiber spreading assay, siRNA knockdown, chromatin fractionation, sister chromatid exchange assay","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus DNA fiber assay with multiple genome stability readouts, single lab","pmids":["19730436"],"is_preprint":false},{"year":2010,"finding":"ING2 controls the G1/S transition by regulating p21 expression independently of p53. Knockdown of ING2 accelerates G1-to-S phase progression and decreases p21 levels. This function is specific to ING2 and not shared by its closest homolog ING1.","method":"siRNA knockdown, cell cycle analysis (FACS), RT-PCR/Western blot for p21, comparative ING1 vs ING2 experiments","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — knockdown with defined cell cycle phenotype and molecular readout, specificity confirmed by ING1 comparison, single lab","pmids":["20890119"],"is_preprint":false},{"year":2010,"finding":"ING2 is sumoylated by SUMO1 on lysine 195 both in vitro and in vivo. Sumoylation of ING2 enhances its association with Sin3A and is required for ING2 binding to the promoters of specific target genes (e.g., TMEM71) and for recruitment of the Sin3A/HDAC complex to those promoters to regulate transcription.","method":"In vitro sumoylation assay, in vivo SUMO modification assay, Co-IP, ChIP, site-directed mutagenesis (K195R)","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro sumoylation plus in vivo validation with site mutagenesis and ChIP, single lab","pmids":["20676127"],"is_preprint":false},{"year":2008,"finding":"ING2 associates with histone methyltransferase (HMT) activity in vitro and in vivo, methylating histone H3 with a specificity distinct from the MeCP2-recruited HMT. The ING2-associated HMT shows increased activity when H3K9 is already methylated, but reduced activity when H3K4 is mutated or methylated. The C-terminus of ING2 recruits this HMT activity and correlates with its gene silencing function, which is HDAC-independent (resistant to trichostatin A).","method":"In vitro HMT assay, co-immunoprecipitation, reporter-based silencing assays, domain deletion/mutation analysis, TSA resistance assay","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro enzyme assay plus Co-IP with domain mapping and functional silencing readout, single lab","pmids":["18513492"],"is_preprint":false},{"year":2010,"finding":"Targeted germline disruption of Ing2 in mice causes male infertility due to defective spermatogenesis with meiotic arrest before pachytene stage, incomplete meiotic recombination, and enhanced apoptosis. Arrested spermatocytes lacked specific HDAC1 accumulation and showed deregulated chromatin acetylation, implicating an ING2/HDAC1/H3K4me3-regulated chromatin modification pathway in spermatogenesis. Ing2-null mice also develop soft-tissue sarcomas, confirming tumor suppressor function in vivo.","method":"Targeted gene knockout in mice, histology, sperm count/motility assays, immunostaining for HDAC1 and histone acetylation marks, tumor incidence analysis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout with multiple orthogonal phenotypic and molecular readouts, definitive tumor suppressor confirmation","pmids":["21124965"],"is_preprint":false},{"year":2009,"finding":"ING2 protein levels increase upon MNNG treatment in an MMR (MLH1)- and c-Abl-dependent manner. MNNG-induced ING2 localizes to the nucleus and associates with p73α. Suppression of ING2 by shRNA decreases MNNG sensitivity and abrogates MNNG-induced stabilization and acetylation of p73α, placing ING2 downstream of MMR/c-Abl and upstream of p73α in the alkylation-induced cell death pathway.","method":"shRNA knockdown, immunoprecipitation, immunofluorescence, Western blot, kinase inhibitor (STI571) treatment, cell viability assays","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — epistasis via shRNA and inhibitor treatment with Co-IP showing ING2-p73α association, single lab","pmids":["19766113"],"is_preprint":false},{"year":2007,"finding":"ING2 interacts in vivo with the corepressor Alien (also known as TRIP15/CSN2). The interaction was confirmed in vitro by GST pulldown, indicating direct binding. The binding domain was mapped to a central region of Alien. Co-expression of ING2 enhances Alien-mediated transcriptional silencing.","method":"SELDI-MS proteomics, co-immunoprecipitation, GST pulldown, transcriptional silencing assays","journal":"Journal of proteome research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP and GST pulldown with functional reporter assay, single lab","pmids":["17929852"],"is_preprint":false},{"year":2016,"finding":"ING2 acts as a corepressor for the androgen receptor (AR): ING2 interacts with AR, hampers AR transcriptional activation, causes growth arrest, and induces cellular senescence in prostate cancer cells. ING2 protein levels are upregulated as a compensatory mechanism when ING1b is knocked down, suggesting a crosstalk between ING1 and ING2 to co-regulate AR signaling.","method":"Co-immunoprecipitation, siRNA/shRNA knockdown, luciferase reporter assays, cell growth assays, senescence assays, Ing1 knockout mouse tissues","journal":"Journal of molecular medicine (Berlin, Germany)","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP, functional assays, in vivo KO validation, single lab","pmids":["27305909"],"is_preprint":false},{"year":2021,"finding":"ING2 is imported into the inner mitochondrial compartment in a redox-sensitive manner, and this translocation is modulated by 14-3-3η protein expression. Mitochondrial ING2 interacts with mtDNA, and this interaction is mediated by TFAM. Loss of mitochondrial ING2 decreases mitochondrial ROS production and impairs OXPHOS activity, establishing ING2 as a regulator of mitochondrial respiration and metabolic homeostasis.","method":"Subcellular fractionation, immunofluorescence/confocal microscopy, Co-immunoprecipitation (ING2-TFAM), oxygen consumption rate (OCR) assay, ROS measurement, siRNA knockdown","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation plus Co-IP and functional OCR/ROS assays, multiple methods, single lab","pmids":["34017078"],"is_preprint":false},{"year":2021,"finding":"ING2 positively regulates mitochondrial respiration in tubular epithelial cells by controlling the ubiquitination and stability of MRPL12, a mitochondrial transcription factor, thereby modulating mtDNA transcription and expression of mtDNA-encoded respiratory chain components. ING2 overexpression in vivo ameliorates acute ischemic kidney injury.","method":"Co-immunoprecipitation, ubiquitination assay, oxygen consumption rate assay, PCR/Western blot, immunofluorescence, in vivo kidney-specific overexpression mouse model","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus ubiquitination assay and functional OCR readout with in vivo validation, single lab","pmids":["34434929"],"is_preprint":false},{"year":2021,"finding":"ING1 and ING2 are recruited to the negative androgen response element (nARE) in the hTERT core promoter in an androgen-dependent manner, and knockdown of ING1 and ING2 blocks AR-mediated repression of hTERT, establishing both as AR co-repressors required for supraphysiological androgen-induced hTERT repression.","method":"ChIP, siRNA knockdown, luciferase reporter assays, RT-PCR, cancer spheroid models","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP showing chromatin recruitment plus functional knockdown with gene expression readout, single lab","pmids":["34439179"],"is_preprint":false},{"year":2012,"finding":"ING2 is required for myogenic differentiation of C2C12 cells; RNAi knockdown blocks differentiation into myotubes. Structure-function analysis shows the leucine zipper motif is required for ING2-driven differentiation, while the PHD domain inhibits this function. The Sin3A-HDAC1 complex, which interacts with ING2, is also required for ING2-dependent muscle differentiation.","method":"RNAi knockdown, overexpression, domain deletion/mutation analysis, myogenic differentiation assay, Co-immunoprecipitation","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — knockdown with defined differentiation phenotype and domain mapping, single lab","pmids":["22808232"],"is_preprint":false},{"year":2009,"finding":"ING2 upregulates matrix metalloproteinase 13 (MMP13) expression, and this regulation requires the ING2-HDAC1-mSin3A complex. Co-expression of ING2 with HDAC1 or mSin3A further induces MMP13. ING2 overexpression increases invasive potential of colon cancer cells, establishing a functional link between ING2 chromatin complex activity and MMP13-dependent invasion.","method":"Microarray, overexpression, siRNA knockdown, EMSA, luciferase assays (NF-κB on ING2 promoter), in vitro invasion assay, RT-PCR/Western blot","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — multiple confirmatory methods for MMP13 regulation with functional invasion readout, single lab","pmids":["19437536"],"is_preprint":false}],"current_model":"ING2 is a chromatin-regulatory tumor suppressor that, through its PHD domain, reads the H3K4me3 histone mark and recruits the mSin3A-HDAC1 co-repressor complex to gene promoters to silence proliferation genes, particularly in response to DNA damage; it additionally binds nuclear PtdIns(5)P to modulate chromatin targeting, activates p53 by acting as a scaffold that enhances p300-mediated p53 acetylation, controls DNA replication fork progression via PCNA interaction, is regulated post-translationally by Smurf1-dependent ubiquitination and SUMO1 modification at K195, and translocates to mitochondria where it regulates OXPHOS through MRPL12 ubiquitination."},"narrative":{"mechanistic_narrative":"ING2 is a chromatin-regulatory tumor suppressor that couples histone-mark reading to transcriptional repression and the DNA-damage response, with in vivo knockout confirming its tumor-suppressor and developmental roles [PMID:16728974, PMID:21124965]. Its PHD finger binds H3K4me3/me2 with high affinity through aromatic residues that cage the trimethylammonium group of Lys4, and this reading function stabilizes the mSin3A–HDAC1 co-repressor complex at promoters of proliferation genes in response to genotoxic stress, with binding-disrupting mutations abolishing the downstream cellular response [PMID:16728974, PMID:16728977]. The same PHD finger binds nuclear PtdIns(5)P, which acts as a sub-nuclear trafficking factor that stabilizes ING2 occupancy at a subset of damage-induced target promoters and is required for ING2-dependent p53 activation [PMID:12859901, PMID:23823870]. ING2 promotes p53 function by acting as a scaffold—mediated through its N-terminal leucine-zipper-like motif—that bridges p53 to the acetyltransferase p300, enhancing p53 Lys-382 acetylation and driving p53-dependent growth arrest and replicative senescence [PMID:11481424, PMID:16024799, PMID:16782091]. Beyond canonical p53 signaling, ING2 enhances nucleotide excision repair by promoting histone H4 acetylation, chromatin relaxation and XPA recruitment to photolesions [PMID:16488987], regulates the G1/S transition and p21 expression independently of p53 [PMID:20890119], and controls DNA replication fork progression and genome stability through interaction with PCNA [PMID:19730436]. ING2 activity is gated post-translationally: it is targeted for proteasomal degradation by the HECT ligase Smurf1 [PMID:20621832] and is sumoylated at Lys-195 by SUMO1, a modification that strengthens its Sin3A association and promoter binding [PMID:20676127]. ING2 also serves as a transcriptional cofactor in additional programs, functioning in TGF-β/Smad signaling via SnoN [PMID:18334480], as an androgen-receptor co-repressor [PMID:27305909, PMID:34439179], and in myogenic differentiation through its Sin3A–HDAC1 complex [PMID:22808232]. A distinct mitochondrial pool of ING2 is imported into the inner mitochondrial compartment in a redox- and 14-3-3η-dependent manner, binds mtDNA via TFAM, and regulates oxidative phosphorylation, in part by controlling ubiquitination and stability of the mitochondrial factor MRPL12 [PMID:34017078, PMID:34434929].","teleology":[{"year":2001,"claim":"Established ING2 as a p53-dependent growth suppressor, answering whether the protein had tumor-suppressor activity and how it engaged the p53 pathway.","evidence":"Proliferation and p53 transactivation reporter assays, p53 acetylation Western blot, knockdown/overexpression in cells, DNA-damage induction","pmids":["11481424"],"confidence":"Medium","gaps":["Did not define the molecular basis for enhanced p53 acetylation","No direct partner for the acetylation step identified at this stage"]},{"year":2003,"claim":"Identified the PHD finger as a phosphoinositide receptor, linking a lipid second messenger to ING2's nuclear function and p53 activation.","evidence":"In vitro lipid-binding assays, in vivo nuclear interaction studies, p53 transcription and apoptosis assays","pmids":["12859901"],"confidence":"High","gaps":["Did not define genomic targets affected by PtdIns(5)P binding","Relationship between lipid binding and histone-mark reading unresolved"]},{"year":2005,"claim":"Defined the mechanism of p53 activation by showing ING2 scaffolds a p53–p300 ternary complex to drive acetylation and senescence.","evidence":"Reciprocal Co-IP, siRNA knockdown, overexpression, senescence assays in fibroblasts","pmids":["16024799"],"confidence":"Medium","gaps":["Single-lab Co-IP for the ternary complex","Did not map the ING2 region required for bridging (later addressed in #7)"]},{"year":2006,"claim":"Resolved the central reader function: the PHD finger binds H3K4me3/me2 and converts this active mark into repression by stabilizing mSin3A–HDAC1 at proliferation-gene promoters during DNA damage.","evidence":"Biochemical binding assays, ChIP, loss-of-function mutagenesis, Co-IP, DNA-damage assays; 2.0 Å crystal structure of the PHD–H3K4me3 complex with mutagenesis","pmids":["16728974","16728977"],"confidence":"High","gaps":["Did not establish how the reader function integrates with PtdIns(5)P binding on the same domain","Genome-wide target set not defined"]},{"year":2006,"claim":"Connected ING2 to chromatin-based DNA repair and mapped the scaffolding domain, showing ING2 enables NER and bridges p53 to p300 via its leucine-zipper-like motif.","evidence":"Host-cell reactivation/NER assays, histone acetylation and chromatin accessibility assays, XPA immunofluorescence, domain-deletion Co-IP","pmids":["16488987","16782091"],"confidence":"Medium","gaps":["Mechanism linking H4 acetylation to XPA recruitment not detailed","Single-lab deletion mapping for the p53-bridging function"]},{"year":2008,"claim":"Broadened ING2's repertoire to TGF-β signaling and to an associated histone methyltransferase activity, indicating roles beyond HDAC-dependent silencing.","evidence":"Co-IP of ING2–SnoN–Smad2 complex with RNAi epistasis and reporter assays; in vitro HMT assays with domain mapping and TSA-resistance silencing assays","pmids":["18334480","18513492"],"confidence":"Medium","gaps":["Identity of the ING2-associated HMT enzyme not established","HDAC-independent silencing mechanism not fully reconciled with the Sin3A model"]},{"year":2009,"claim":"Extended ING2 into replication and genome maintenance and into a parallel DNA-alkylation death pathway, defining PCNA and p73α as effectors.","evidence":"Co-IP with PCNA, DNA fiber spreading, chromatin fractionation, SCE assays; shRNA/inhibitor epistasis placing ING2 between MMR/c-Abl and p73α; MMP13/invasion microarray and assays","pmids":["19730436","19766113","19437536"],"confidence":"Medium","gaps":["Direct effect of ING2 on PCNA loading mechanistically unresolved","ING2-p73α interaction shown by single-lab Co-IP"]},{"year":2010,"claim":"Defined post-translational control of ING2 (Smurf1 degradation, SUMO1 modification) and clarified how chromatin targeting and p53-independent cell-cycle control operate.","evidence":"Co-IP and ubiquitination assays with domain mapping (Smurf1); in vitro/in vivo sumoylation with K195R mutagenesis and ChIP; SAHA-induced Sin3 dissociation with ChIP at p21; comparative ING1/ING2 cell-cycle knockdown","pmids":["20621832","20676127","20142042","20890119"],"confidence":"Medium","gaps":["Cross-talk between SUMO1 modification and Smurf1-mediated degradation not addressed","Each finding from a single lab"]},{"year":2010,"claim":"Provided the definitive in vivo confirmation of tumor-suppressor function and a developmental role, linking the ING2/HDAC1/H3K4me3 chromatin axis to spermatogenesis.","evidence":"Targeted Ing2 knockout mice with histology, sperm assays, HDAC1/histone-acetylation immunostaining, and tumor incidence analysis","pmids":["21124965"],"confidence":"High","gaps":["Did not dissect which molecular ING2 functions drive sarcoma formation","Mechanism of meiotic arrest not resolved to specific target genes"]},{"year":2016,"claim":"Identified ING2 as an androgen-receptor co-repressor with ING1 cross-regulation, expanding its transcriptional control to nuclear-receptor signaling in cancer.","evidence":"Co-IP, siRNA/shRNA knockdown, luciferase reporters, growth/senescence assays, Ing1 knockout tissues","pmids":["27305909"],"confidence":"Medium","gaps":["Direct vs indirect AR binding not fully resolved","Single-lab characterization"]},{"year":2021,"claim":"Uncovered a non-nuclear function: a mitochondrial ING2 pool regulating OXPHOS through mtDNA/TFAM association and MRPL12 ubiquitination.","evidence":"Subcellular fractionation, confocal microscopy, Co-IP (TFAM, MRPL12), ubiquitination assays, OCR/ROS measurements, in vivo kidney and AR/hTERT models","pmids":["34017078","34434929","34439179"],"confidence":"Medium","gaps":["Mechanism of redox-sensitive mitochondrial import incompletely defined","How nuclear and mitochondrial ING2 pools are partitioned is unknown","MRPL12 ubiquitination shown in a single lab"]},{"year":null,"claim":"How ING2's competing PHD-domain ligands (H3K4me3 versus PtdIns(5)P) and its multiple post-translational modifications are integrated to dictate which target promoters, repair sites, or subcellular pools it engages remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model coordinating histone-mark reading, lipid binding, SUMO/ubiquitin signals","Genome-wide direct target map absent","Determinants partitioning nuclear vs mitochondrial ING2 unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[0,1]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,7]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,10,18]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[19]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,9,16]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[19,20]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,13]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[6,11]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[12,11]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[3,10,18]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10]}],"complexes":["mSin3A-HDAC1 co-repressor complex"],"partners":["TP53","EP300","PCNA","SNON","SMAD2","SMURF1","AR","TFAM"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H160","full_name":"Inhibitor of growth protein 2","aliases":["Inhibitor of growth 1-like protein","ING1Lp","p32","p33ING2"],"length_aa":280,"mass_kda":32.8,"function":"Seems to be involved in p53/TP53 activation and p53/TP53-dependent apoptotic pathways, probably by enhancing acetylation of p53/TP53. Component of a mSin3A-like corepressor complex, which is probably involved in deacetylation of nucleosomal histones. ING2 activity seems to be modulated by binding to phosphoinositides (PtdInsPs)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9H160/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ING2","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HDAC1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ING2","total_profiled":1310},"omim":[{"mim_id":"620287","title":"TRANSMEMBRANE PROTEIN 71; TMEM71","url":"https://www.omim.org/entry/620287"},{"mim_id":"608525","title":"INHIBITOR OF GROWTH 5; ING5","url":"https://www.omim.org/entry/608525"},{"mim_id":"608524","title":"INHIBITOR OF GROWTH 4; ING4","url":"https://www.omim.org/entry/608524"},{"mim_id":"604215","title":"INHIBITOR OF GROWTH 2; ING2","url":"https://www.omim.org/entry/604215"},{"mim_id":"602810","title":"HISTONE GENE CLUSTER 1, H3 HISTONE FAMILY, MEMBER A; HIST1H3A","url":"https://www.omim.org/entry/602810"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ING2"},"hgnc":{"alias_symbol":["p33ING2"],"prev_symbol":["ING1L"]},"alphafold":{"accession":"Q9H160","domains":[{"cath_id":"1.10.287","chopping":"11-126","consensus_level":"medium","plddt":91.932,"start":11,"end":126},{"cath_id":"3.30.40.10","chopping":"209-263","consensus_level":"medium","plddt":86.7787,"start":209,"end":263}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H160","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H160-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H160-F1-predicted_aligned_error_v6.png","plddt_mean":75.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ING2","jax_strain_url":"https://www.jax.org/strain/search?query=ING2"},"sequence":{"accession":"Q9H160","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H160.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H160/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H160"}},"corpus_meta":[{"pmid":"16728974","id":"PMC_16728974","title":"ING2 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ING2-D1G, a novel acidogenic bacterium isolated from a mesophilic biogas reactor.","date":"2017","source":"Journal of biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/28595834","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":23274,"output_tokens":6160,"usd":0.081111,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":14844,"output_tokens":4363,"usd":0.091648,"stage2_stop_reason":"end_turn"},"total_usd":0.172759,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"The PHD domain of ING2 binds specifically and with high affinity to trimethylated and dimethylated histone H3 lysine 4 (H3K4me3/me2), functioning as an effector module for this histone mark. In response to DNA damage, this interaction stabilizes the mSin3a-HDAC1 repressive complex at promoters of proliferation genes, constituting a mechanism by which H3K4me3 drives active gene repression. Mutations disrupting H3K4me3 binding abolish ING2-mediated cellular responses to genotoxic insults.\",\n      \"method\": \"Biochemical binding assays, ChIP, loss-of-function mutagenesis, co-immunoprecipitation, cellular DNA damage response assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (binding assays, ChIP, mutagenesis, cellular phenotype), replicated by structural study in the same issue\",\n      \"pmids\": [\"16728974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structure (2.0 Å) of the mouse ING2 PHD finger in complex with H3K4me3 peptide revealed that the trimethylammonium group of Lys4 is recognized by aromatic residues Y215 and W238 in a deep binding groove, with additional hydrogen-bonding contacts to Ala1, Arg2, Thr3, and Thr6 of the histone tail. Substitution of binding-site residues disrupts H3K4me3 interaction in vitro and impairs ING2-induced apoptosis in vivo.\",\n      \"method\": \"X-ray crystallography (2.0 Å resolution), in vitro binding assays, site-directed mutagenesis, apoptosis assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution structure with functional mutagenesis validation, independently corroborated by companion paper\",\n      \"pmids\": [\"16728977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The PHD finger of ING2 binds phosphoinositides in vitro, including phosphatidylinositol 5-phosphate (PtdIns(5)P). The ING2 PHD finger interacts with PtdIns(5)P in vivo in the nucleus, and this interaction regulates the ability of ING2 to activate p53 and p53-dependent apoptotic pathways in response to DNA damage.\",\n      \"method\": \"In vitro lipid-binding assays, in vivo interaction studies, p53 transcriptional assays, apoptosis assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro biochemical assays plus in vivo functional validation with multiple readouts in a single rigorous study\",\n      \"pmids\": [\"12859901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ING2 (p33ING2) negatively regulates cell growth in a p53-dependent manner and enhances p53 transcriptional activity. ING2 expression increases acetylation of p53 at Lys-382, indicating ING2 promotes p53 acetylation as part of its tumor suppressive function. ING2 is induced by DNA-damaging agents etoposide and neocarzinostatin.\",\n      \"method\": \"Cell proliferation assays, p53 transactivation reporter assays, Western blot for p53 acetylation, siRNA knockdown, overexpression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple cellular assays in one study, single lab, acetylation shown by Western blot\",\n      \"pmids\": [\"11481424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"ING2 forms a complex with p53 and the histone acetyltransferase p300, enhances the interaction between p53 and p300, and acts as a cofactor for p300-mediated p53 acetylation. ING2-mediated p300-dependent p53 acetylation triggers replicative senescence; overexpression induces senescence in young fibroblasts in a p53-dependent manner, and siRNA knockdown of ING2 delays senescence onset.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, overexpression, senescence assays, colocalization studies\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP showing ternary complex, functional rescue/knockdown with defined phenotype, single lab\",\n      \"pmids\": [\"16024799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Treatment with the HDAC inhibitor SAHA causes dissociation of the ING2 subunit (via its PHD finger) from the Sin3 deacetylase complex. Loss of ING2 from the complex disrupts in vivo binding of the Sin3 complex to the p21 promoter, revealing a molecular mechanism by which HDAC inhibitors disrupt deacetylase function at target gene promoters.\",\n      \"method\": \"Mass spectrometry-based proteomics, Co-IP, ChIP at p21 promoter, pharmacological treatment with SAHA\",\n      \"journal\": \"Chemistry & biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based complex analysis plus ChIP, single lab, two orthogonal methods\",\n      \"pmids\": [\"20142042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ING2 enhances nucleotide excision repair of UV-induced DNA damage in a p53-dependent manner. ING2 is required for UV-induced histone H4 acetylation, chromatin relaxation, and recruitment of the damage-recognition protein XPA to photolesions. Knockdown of ING2 completely abolishes NER, demonstrating that physiological ING2 levels are required for this process.\",\n      \"method\": \"Host-cell reactivation assay, siRNA knockdown, histone acetylation assays, chromatin accessibility assays, XPA recruitment by immunofluorescence\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional NER assay with knockdown and overexpression, chromatin readout, single lab\",\n      \"pmids\": [\"16488987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The leucine zipper-like (LZL) motif in the N-terminus of ING2 is critical for DNA repair, apoptosis, and chromatin remodeling after UV irradiation. Deletion of the LZL domain abrogates the association between ING2 and p53, but not between ING2 and p300, indicating ING2 functions as a scaffold mediating p53-p300 interaction.\",\n      \"method\": \"Domain deletion mutagenesis, Co-immunoprecipitation, apoptosis assays, NER assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — structure-function by deletion mapping plus co-IP and cellular phenotype assays, single lab\",\n      \"pmids\": [\"16782091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The HECT-type ubiquitin ligase Smurf1 interacts with ING2 and targets it for polyubiquitination and proteasomal degradation. The catalytic HECT domain of Smurf1 mediates ING2 binding, and the C-terminal PHD domain of ING2 is required for Smurf1-mediated degradation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, proteasome inhibitor experiments, domain mapping\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP plus ubiquitination assay with domain mapping, single lab\",\n      \"pmids\": [\"20621832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Nuclear phosphatidylinositol-5-phosphate (PtdIns(5)P) directly associates with ING2 and is required for ING2 occupancy at a subset of genomic target promoters in response to DNA damage. PtdIns(5)P acts as a sub-nuclear trafficking factor stabilizing ING2 at discrete chromatin sites; depletion of PtdIns(5)P attenuates ING2-mediated gene repression at these targets.\",\n      \"method\": \"ChIP, PtdIns(5)P depletion, gene expression analysis, lipid-binding assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP with lipid manipulation and gene expression readouts, single lab, two orthogonal approaches\",\n      \"pmids\": [\"23823870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ING2 promotes TGF-β-induced transcription and cell cycle arrest. ING2 interacts with the transcriptional modulator SnoN, and together they form a complex with Smad2. Knockdown of SnoN blocks ING2-dependent TGF-β transcription, while SnoN expression augments it, placing ING2 in the TGF-β-Smad signaling pathway as a co-activator.\",\n      \"method\": \"Co-immunoprecipitation, RNA interference, overexpression, transcriptional reporter assays, cell cycle analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP showing ternary complex, RNAi epistasis, reporter assays, single lab\",\n      \"pmids\": [\"18334480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"ING2 interacts with PCNA (proliferating cell nuclear antigen) and regulates the amount of PCNA associated with chromatin, thereby controlling DNA replication fork progression. siRNA-mediated knockdown of ING2 markedly reduces global replication rate (DNA fiber spreading), causes endoreduplication, and increases sister chromatid exchange frequency, demonstrating a role for ING2 in maintaining genome stability.\",\n      \"method\": \"Co-immunoprecipitation, DNA fiber spreading assay, siRNA knockdown, chromatin fractionation, sister chromatid exchange assay\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus DNA fiber assay with multiple genome stability readouts, single lab\",\n      \"pmids\": [\"19730436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ING2 controls the G1/S transition by regulating p21 expression independently of p53. Knockdown of ING2 accelerates G1-to-S phase progression and decreases p21 levels. This function is specific to ING2 and not shared by its closest homolog ING1.\",\n      \"method\": \"siRNA knockdown, cell cycle analysis (FACS), RT-PCR/Western blot for p21, comparative ING1 vs ING2 experiments\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — knockdown with defined cell cycle phenotype and molecular readout, specificity confirmed by ING1 comparison, single lab\",\n      \"pmids\": [\"20890119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"ING2 is sumoylated by SUMO1 on lysine 195 both in vitro and in vivo. Sumoylation of ING2 enhances its association with Sin3A and is required for ING2 binding to the promoters of specific target genes (e.g., TMEM71) and for recruitment of the Sin3A/HDAC complex to those promoters to regulate transcription.\",\n      \"method\": \"In vitro sumoylation assay, in vivo SUMO modification assay, Co-IP, ChIP, site-directed mutagenesis (K195R)\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro sumoylation plus in vivo validation with site mutagenesis and ChIP, single lab\",\n      \"pmids\": [\"20676127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"ING2 associates with histone methyltransferase (HMT) activity in vitro and in vivo, methylating histone H3 with a specificity distinct from the MeCP2-recruited HMT. The ING2-associated HMT shows increased activity when H3K9 is already methylated, but reduced activity when H3K4 is mutated or methylated. The C-terminus of ING2 recruits this HMT activity and correlates with its gene silencing function, which is HDAC-independent (resistant to trichostatin A).\",\n      \"method\": \"In vitro HMT assay, co-immunoprecipitation, reporter-based silencing assays, domain deletion/mutation analysis, TSA resistance assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro enzyme assay plus Co-IP with domain mapping and functional silencing readout, single lab\",\n      \"pmids\": [\"18513492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Targeted germline disruption of Ing2 in mice causes male infertility due to defective spermatogenesis with meiotic arrest before pachytene stage, incomplete meiotic recombination, and enhanced apoptosis. Arrested spermatocytes lacked specific HDAC1 accumulation and showed deregulated chromatin acetylation, implicating an ING2/HDAC1/H3K4me3-regulated chromatin modification pathway in spermatogenesis. Ing2-null mice also develop soft-tissue sarcomas, confirming tumor suppressor function in vivo.\",\n      \"method\": \"Targeted gene knockout in mice, histology, sperm count/motility assays, immunostaining for HDAC1 and histone acetylation marks, tumor incidence analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout with multiple orthogonal phenotypic and molecular readouts, definitive tumor suppressor confirmation\",\n      \"pmids\": [\"21124965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"ING2 protein levels increase upon MNNG treatment in an MMR (MLH1)- and c-Abl-dependent manner. MNNG-induced ING2 localizes to the nucleus and associates with p73α. Suppression of ING2 by shRNA decreases MNNG sensitivity and abrogates MNNG-induced stabilization and acetylation of p73α, placing ING2 downstream of MMR/c-Abl and upstream of p73α in the alkylation-induced cell death pathway.\",\n      \"method\": \"shRNA knockdown, immunoprecipitation, immunofluorescence, Western blot, kinase inhibitor (STI571) treatment, cell viability assays\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — epistasis via shRNA and inhibitor treatment with Co-IP showing ING2-p73α association, single lab\",\n      \"pmids\": [\"19766113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ING2 interacts in vivo with the corepressor Alien (also known as TRIP15/CSN2). The interaction was confirmed in vitro by GST pulldown, indicating direct binding. The binding domain was mapped to a central region of Alien. Co-expression of ING2 enhances Alien-mediated transcriptional silencing.\",\n      \"method\": \"SELDI-MS proteomics, co-immunoprecipitation, GST pulldown, transcriptional silencing assays\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP and GST pulldown with functional reporter assay, single lab\",\n      \"pmids\": [\"17929852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ING2 acts as a corepressor for the androgen receptor (AR): ING2 interacts with AR, hampers AR transcriptional activation, causes growth arrest, and induces cellular senescence in prostate cancer cells. ING2 protein levels are upregulated as a compensatory mechanism when ING1b is knocked down, suggesting a crosstalk between ING1 and ING2 to co-regulate AR signaling.\",\n      \"method\": \"Co-immunoprecipitation, siRNA/shRNA knockdown, luciferase reporter assays, cell growth assays, senescence assays, Ing1 knockout mouse tissues\",\n      \"journal\": \"Journal of molecular medicine (Berlin, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP, functional assays, in vivo KO validation, single lab\",\n      \"pmids\": [\"27305909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ING2 is imported into the inner mitochondrial compartment in a redox-sensitive manner, and this translocation is modulated by 14-3-3η protein expression. Mitochondrial ING2 interacts with mtDNA, and this interaction is mediated by TFAM. Loss of mitochondrial ING2 decreases mitochondrial ROS production and impairs OXPHOS activity, establishing ING2 as a regulator of mitochondrial respiration and metabolic homeostasis.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence/confocal microscopy, Co-immunoprecipitation (ING2-TFAM), oxygen consumption rate (OCR) assay, ROS measurement, siRNA knockdown\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation plus Co-IP and functional OCR/ROS assays, multiple methods, single lab\",\n      \"pmids\": [\"34017078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ING2 positively regulates mitochondrial respiration in tubular epithelial cells by controlling the ubiquitination and stability of MRPL12, a mitochondrial transcription factor, thereby modulating mtDNA transcription and expression of mtDNA-encoded respiratory chain components. ING2 overexpression in vivo ameliorates acute ischemic kidney injury.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, oxygen consumption rate assay, PCR/Western blot, immunofluorescence, in vivo kidney-specific overexpression mouse model\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus ubiquitination assay and functional OCR readout with in vivo validation, single lab\",\n      \"pmids\": [\"34434929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ING1 and ING2 are recruited to the negative androgen response element (nARE) in the hTERT core promoter in an androgen-dependent manner, and knockdown of ING1 and ING2 blocks AR-mediated repression of hTERT, establishing both as AR co-repressors required for supraphysiological androgen-induced hTERT repression.\",\n      \"method\": \"ChIP, siRNA knockdown, luciferase reporter assays, RT-PCR, cancer spheroid models\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP showing chromatin recruitment plus functional knockdown with gene expression readout, single lab\",\n      \"pmids\": [\"34439179\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"ING2 is required for myogenic differentiation of C2C12 cells; RNAi knockdown blocks differentiation into myotubes. Structure-function analysis shows the leucine zipper motif is required for ING2-driven differentiation, while the PHD domain inhibits this function. The Sin3A-HDAC1 complex, which interacts with ING2, is also required for ING2-dependent muscle differentiation.\",\n      \"method\": \"RNAi knockdown, overexpression, domain deletion/mutation analysis, myogenic differentiation assay, Co-immunoprecipitation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — knockdown with defined differentiation phenotype and domain mapping, single lab\",\n      \"pmids\": [\"22808232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"ING2 upregulates matrix metalloproteinase 13 (MMP13) expression, and this regulation requires the ING2-HDAC1-mSin3A complex. Co-expression of ING2 with HDAC1 or mSin3A further induces MMP13. ING2 overexpression increases invasive potential of colon cancer cells, establishing a functional link between ING2 chromatin complex activity and MMP13-dependent invasion.\",\n      \"method\": \"Microarray, overexpression, siRNA knockdown, EMSA, luciferase assays (NF-κB on ING2 promoter), in vitro invasion assay, RT-PCR/Western blot\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — multiple confirmatory methods for MMP13 regulation with functional invasion readout, single lab\",\n      \"pmids\": [\"19437536\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ING2 is a chromatin-regulatory tumor suppressor that, through its PHD domain, reads the H3K4me3 histone mark and recruits the mSin3A-HDAC1 co-repressor complex to gene promoters to silence proliferation genes, particularly in response to DNA damage; it additionally binds nuclear PtdIns(5)P to modulate chromatin targeting, activates p53 by acting as a scaffold that enhances p300-mediated p53 acetylation, controls DNA replication fork progression via PCNA interaction, is regulated post-translationally by Smurf1-dependent ubiquitination and SUMO1 modification at K195, and translocates to mitochondria where it regulates OXPHOS through MRPL12 ubiquitination.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ING2 is a chromatin-regulatory tumor suppressor that couples histone-mark reading to transcriptional repression and the DNA-damage response, with in vivo knockout confirming its tumor-suppressor and developmental roles [#0, #15]. Its PHD finger binds H3K4me3/me2 with high affinity through aromatic residues that cage the trimethylammonium group of Lys4, and this reading function stabilizes the mSin3A–HDAC1 co-repressor complex at promoters of proliferation genes in response to genotoxic stress, with binding-disrupting mutations abolishing the downstream cellular response [#0, #1]. The same PHD finger binds nuclear PtdIns(5)P, which acts as a sub-nuclear trafficking factor that stabilizes ING2 occupancy at a subset of damage-induced target promoters and is required for ING2-dependent p53 activation [#2, #9]. ING2 promotes p53 function by acting as a scaffold—mediated through its N-terminal leucine-zipper-like motif—that bridges p53 to the acetyltransferase p300, enhancing p53 Lys-382 acetylation and driving p53-dependent growth arrest and replicative senescence [#3, #4, #7]. Beyond canonical p53 signaling, ING2 enhances nucleotide excision repair by promoting histone H4 acetylation, chromatin relaxation and XPA recruitment to photolesions [#6], regulates the G1/S transition and p21 expression independently of p53 [#12], and controls DNA replication fork progression and genome stability through interaction with PCNA [#11]. ING2 activity is gated post-translationally: it is targeted for proteasomal degradation by the HECT ligase Smurf1 [#8] and is sumoylated at Lys-195 by SUMO1, a modification that strengthens its Sin3A association and promoter binding [#13]. ING2 also serves as a transcriptional cofactor in additional programs, functioning in TGF-β/Smad signaling via SnoN [#10], as an androgen-receptor co-repressor [#18, #21], and in myogenic differentiation through its Sin3A–HDAC1 complex [#22]. A distinct mitochondrial pool of ING2 is imported into the inner mitochondrial compartment in a redox- and 14-3-3η-dependent manner, binds mtDNA via TFAM, and regulates oxidative phosphorylation, in part by controlling ubiquitination and stability of the mitochondrial factor MRPL12 [#19, #20].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established ING2 as a p53-dependent growth suppressor, answering whether the protein had tumor-suppressor activity and how it engaged the p53 pathway.\",\n      \"evidence\": \"Proliferation and p53 transactivation reporter assays, p53 acetylation Western blot, knockdown/overexpression in cells, DNA-damage induction\",\n      \"pmids\": [\"11481424\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define the molecular basis for enhanced p53 acetylation\", \"No direct partner for the acetylation step identified at this stage\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified the PHD finger as a phosphoinositide receptor, linking a lipid second messenger to ING2's nuclear function and p53 activation.\",\n      \"evidence\": \"In vitro lipid-binding assays, in vivo nuclear interaction studies, p53 transcription and apoptosis assays\",\n      \"pmids\": [\"12859901\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define genomic targets affected by PtdIns(5)P binding\", \"Relationship between lipid binding and histone-mark reading unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined the mechanism of p53 activation by showing ING2 scaffolds a p53–p300 ternary complex to drive acetylation and senescence.\",\n      \"evidence\": \"Reciprocal Co-IP, siRNA knockdown, overexpression, senescence assays in fibroblasts\",\n      \"pmids\": [\"16024799\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab Co-IP for the ternary complex\", \"Did not map the ING2 region required for bridging (later addressed in #7)\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Resolved the central reader function: the PHD finger binds H3K4me3/me2 and converts this active mark into repression by stabilizing mSin3A–HDAC1 at proliferation-gene promoters during DNA damage.\",\n      \"evidence\": \"Biochemical binding assays, ChIP, loss-of-function mutagenesis, Co-IP, DNA-damage assays; 2.0 Å crystal structure of the PHD–H3K4me3 complex with mutagenesis\",\n      \"pmids\": [\"16728974\", \"16728977\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish how the reader function integrates with PtdIns(5)P binding on the same domain\", \"Genome-wide target set not defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Connected ING2 to chromatin-based DNA repair and mapped the scaffolding domain, showing ING2 enables NER and bridges p53 to p300 via its leucine-zipper-like motif.\",\n      \"evidence\": \"Host-cell reactivation/NER assays, histone acetylation and chromatin accessibility assays, XPA immunofluorescence, domain-deletion Co-IP\",\n      \"pmids\": [\"16488987\", \"16782091\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking H4 acetylation to XPA recruitment not detailed\", \"Single-lab deletion mapping for the p53-bridging function\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Broadened ING2's repertoire to TGF-β signaling and to an associated histone methyltransferase activity, indicating roles beyond HDAC-dependent silencing.\",\n      \"evidence\": \"Co-IP of ING2–SnoN–Smad2 complex with RNAi epistasis and reporter assays; in vitro HMT assays with domain mapping and TSA-resistance silencing assays\",\n      \"pmids\": [\"18334480\", \"18513492\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the ING2-associated HMT enzyme not established\", \"HDAC-independent silencing mechanism not fully reconciled with the Sin3A model\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended ING2 into replication and genome maintenance and into a parallel DNA-alkylation death pathway, defining PCNA and p73α as effectors.\",\n      \"evidence\": \"Co-IP with PCNA, DNA fiber spreading, chromatin fractionation, SCE assays; shRNA/inhibitor epistasis placing ING2 between MMR/c-Abl and p73α; MMP13/invasion microarray and assays\",\n      \"pmids\": [\"19730436\", \"19766113\", \"19437536\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct effect of ING2 on PCNA loading mechanistically unresolved\", \"ING2-p73α interaction shown by single-lab Co-IP\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined post-translational control of ING2 (Smurf1 degradation, SUMO1 modification) and clarified how chromatin targeting and p53-independent cell-cycle control operate.\",\n      \"evidence\": \"Co-IP and ubiquitination assays with domain mapping (Smurf1); in vitro/in vivo sumoylation with K195R mutagenesis and ChIP; SAHA-induced Sin3 dissociation with ChIP at p21; comparative ING1/ING2 cell-cycle knockdown\",\n      \"pmids\": [\"20621832\", \"20676127\", \"20142042\", \"20890119\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cross-talk between SUMO1 modification and Smurf1-mediated degradation not addressed\", \"Each finding from a single lab\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Provided the definitive in vivo confirmation of tumor-suppressor function and a developmental role, linking the ING2/HDAC1/H3K4me3 chromatin axis to spermatogenesis.\",\n      \"evidence\": \"Targeted Ing2 knockout mice with histology, sperm assays, HDAC1/histone-acetylation immunostaining, and tumor incidence analysis\",\n      \"pmids\": [\"21124965\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not dissect which molecular ING2 functions drive sarcoma formation\", \"Mechanism of meiotic arrest not resolved to specific target genes\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified ING2 as an androgen-receptor co-repressor with ING1 cross-regulation, expanding its transcriptional control to nuclear-receptor signaling in cancer.\",\n      \"evidence\": \"Co-IP, siRNA/shRNA knockdown, luciferase reporters, growth/senescence assays, Ing1 knockout tissues\",\n      \"pmids\": [\"27305909\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect AR binding not fully resolved\", \"Single-lab characterization\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Uncovered a non-nuclear function: a mitochondrial ING2 pool regulating OXPHOS through mtDNA/TFAM association and MRPL12 ubiquitination.\",\n      \"evidence\": \"Subcellular fractionation, confocal microscopy, Co-IP (TFAM, MRPL12), ubiquitination assays, OCR/ROS measurements, in vivo kidney and AR/hTERT models\",\n      \"pmids\": [\"34017078\", \"34434929\", \"34439179\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of redox-sensitive mitochondrial import incompletely defined\", \"How nuclear and mitochondrial ING2 pools are partitioned is unknown\", \"MRPL12 ubiquitination shown in a single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ING2's competing PHD-domain ligands (H3K4me3 versus PtdIns(5)P) and its multiple post-translational modifications are integrated to dictate which target promoters, repair sites, or subcellular pools it engages remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model coordinating histone-mark reading, lipid binding, SUMO/ubiquitin signals\", \"Genome-wide direct target map absent\", \"Determinants partitioning nuclear vs mitochondrial ING2 unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 7]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 10, 18]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 9, 16]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [19, 20]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 13]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [6, 11]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [12, 11]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [3, 10, 18]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"complexes\": [\"mSin3A-HDAC1 co-repressor complex\"],\n    \"partners\": [\"TP53\", \"EP300\", \"PCNA\", \"SnoN\", \"SMAD2\", \"SMURF1\", \"AR\", \"TFAM\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}