{"gene":"PADI4","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2003,"finding":"PADI4 encodes a peptidylarginine deiminase enzyme that catalyzes post-translational citrullination of arginine residues in proteins; a functional haplotype of PADI4 affects mRNA transcript stability and is associated with increased citrullinated peptide autoantigen production in rheumatoid arthritis.","method":"Case-control association study with mRNA stability assays","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional haplotype effect on mRNA stability shown, replicated across multiple Asian population studies, but mechanistic detail limited to transcript-level assays","pmids":["12833157"],"is_preprint":false},{"year":2004,"finding":"PADI4 protein is expressed in T cells, B cells, macrophages, neutrophils, fibroblast-like cells, and endothelial cells in RA synovium; it co-localizes with citrullinated fibrin and apoptotic cells in fibrin deposits, suggesting PADI4 is responsible for fibrin citrullination in the inflamed synovium.","method":"Immunohistochemistry, double immunofluorescent labelling, and western blotting of synovial tissue","journal":"Rheumatology (Oxford, England)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-localization by multiple imaging methods in tissue, but no functional knockout or reconstitution to prove causality","pmids":["15466895"],"is_preprint":false},{"year":2007,"finding":"Estrogen receptor-α (ERα) stimulates PADI4 transcription in MCF-7 cells through both classical and non-classical ER-mediated pathways; transcription factors AP-1, Sp1/Sp3, and NF-Y bind the minimal promoter (−348 bp) of PADI4 and cooperatively regulate its expression, as shown by ChIP and siRNA knockdown.","method":"Luciferase reporter assays, chromatin immunoprecipitation (ChIP), siRNA knockdown","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus siRNA functional validation, single lab, multiple orthogonal methods","pmids":["17456793"],"is_preprint":false},{"year":2009,"finding":"p53 transcriptionally transactivates PADI4 via an intronic p53-binding site; PADI4 in turn citrullinated the histone chaperone nucleophosmin (NPM1) at arginine 197 in vivo, causing NPM1 translocation from nucleoli to nucleoplasm. Knockdown of PADI4 or p53 inhibited DNA-damage-induced protein citrullination; ectopic PADI4 expression inhibited tumor cell growth.","method":"p53 transactivation assay, in vivo citrullination assay, NPM1 R197K mutant localization, siRNA knockdown, cell growth assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (transcriptional assay, site-directed mutagenesis of NPM1, siRNA knockdown with functional readout), single lab but strong mechanistic chain","pmids":["19843866"],"is_preprint":false},{"year":2011,"finding":"PADI4 is enriched at gene promoters near transcription start sites of actively transcribed genes in MCF-7 cells; PADI4 physically associates with transcription factor Elk-1, and following EGF stimulation PADI4 catalytic activity facilitates Elk-1 phosphorylation, histone H4 acetylation, and c-Fos transcriptional activation, defining a novel co-activator role for PADI4.","method":"ChIP-chip (genome-wide), co-immunoprecipitation, EGF stimulation assays, transcriptional reporter assays","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide ChIP-chip plus reciprocal Co-IP plus catalytic-activity-dependent functional assay in one study","pmids":["21655091"],"is_preprint":false},{"year":2012,"finding":"In response to DNA damage, p53 activates PADI4, which citrullinates arginine 3 of histone H4 (cit-H4R3) and also citrullinates Lamin C; cit-H4R3 localizes around fragmented nuclei in apoptotic cells; ectopic PADI4 expression causes chromatin decondensation and promotes DNA cleavage; Padi4-knockout mice show resistance to radiation-induced apoptosis in the thymus.","method":"In vivo and in vitro citrullination assays, Padi4 knockout mice, ectopic expression, immunofluorescence, irradiation model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro and in vivo citrullination, genetic knockout phenotype, ectopic expression, multiple substrates validated","pmids":["22334079"],"is_preprint":false},{"year":2014,"finding":"PADI4 interacts with transcription factor Tal1 and acts as an epigenetic co-activator at the IL6ST gene by counteracting the repressive H3R2me2a mark placed by PRMT6, thereby augmenting the active H3K4me3 mark and increasing IL6ST expression; at the CTCF promoter, PADI4 acts instead as a repressor.","method":"Co-immunoprecipitation, ChIP, gene expression analysis in hematopoietic cells","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ChIP for multiple histone marks, expression readouts at specific target genes, mechanistic chain fully described","pmids":["24874575"],"is_preprint":false},{"year":2014,"finding":"PADI4 physically interacts with DNMT3A and citrullinates it both in vitro and in vivo; citrullination of the region upstream of the PWWP domain of DNMT3A by catalytically active PADI4 stabilizes the DNMT3A protein, increases DNA methyltransferase activity, and increases CpG methylation at the p21 promoter.","method":"Co-immunoprecipitation (endogenous and overexpressed), in vitro and in vivo citrullination assays, pulse-chase protein stability, Padi4-knockout MEFs, bisulfite pyrosequencing","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution, catalytic-activity mutagenesis, KO cell validation, and bisulfite sequencing of functional target in one study","pmids":["24957603"],"is_preprint":false},{"year":2017,"finding":"PADI4 suppresses p21 transcription in RA fibroblast-like synoviocytes by binding to the p21 promoter and altering histone H3 arginine modifications (global H3 citrullination and H3R17 methylation); PADI4 knockdown promotes apoptosis and increases p53 and p21 expression, while ectopic PADI4 inhibits adriamycin-induced apoptosis.","method":"siRNA knockdown, overexpression, ChIP for PADI4 and histone marks at p21 promoter, flow cytometry apoptosis","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus functional knockdown/overexpression, single lab","pmids":["28367100"],"is_preprint":false},{"year":2017,"finding":"PADI4 directly interacts with the E3 ubiquitin ligase synoviolin (SYVN1), and overexpression of PADI4 suppresses ubiquitination of cellular proteins, suggesting crosstalk between citrullination and ubiquitination pathways in RA synoviocytes.","method":"Co-immunoprecipitation, overexpression, ubiquitination assays","journal":"Molecular medicine reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP and overexpression, single lab, no in vitro reconstitution or mutagenesis","pmids":["29039504"],"is_preprint":false},{"year":2021,"finding":"PADI4 expression is induced by hypoxia in a HIF-dependent manner; PADI4 is recruited by HIFs to hypoxia response elements (HREs) and is required for histone citrullination at HREs and transcription of nearly all HIF target genes in breast cancer cells; PADI4 loss reduces breast and liver tumor growth and angiogenesis in mice.","method":"RNA sequencing, ChIP, siRNA knockdown, mouse xenograft tumor models, immunohistochemistry","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide RNA-seq, ChIP at HREs, in vivo tumor models, multiple cell lines, HIF-dependency confirmed","pmids":["34452909"],"is_preprint":false},{"year":2022,"finding":"PADI4 binds to importin α3 (Impα3) with an affinity of ~1–5 µM through two nuclear localization sequences (Pro56–Ser83 and Arg495–Ile526); both NLS-containing peptides bind at the major cargo-binding site of importin α3, explaining nuclear translocation of PADI4.","method":"Fluorescence, circular dichroism, isothermal titration calorimetry (ITC), molecular docking","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — biophysical in vitro binding with mutagenesis-guided mapping and ITC, but single lab; no cell-based nuclear import functional assay reported","pmids":["35883608"],"is_preprint":false},{"year":2022,"finding":"PADI4 citrullinates and stabilizes hRpn13 (proteasome substrate receptor); PADI4 also citrullinates proteasomes (shown by in-cell citrullination), and proteasomes from PADI4-inhibited myeloma cells exhibit reduced peptidase activity.","method":"Proteomic analysis, PADI4 inhibitor treatment, proteasome peptidase activity assay, PROTAC co-depletion","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional proteasome activity assay plus proteomic co-depletion, single lab","pmids":["38151017"],"is_preprint":false},{"year":2022,"finding":"PADI4 exists in a dimeric native structure within a narrow pH range (6.5–8.0) and requires Ca2+ for stability; the protein unfolds through at least one intermediate under guanidinium denaturation, and the native structure is strongly pH-dependent, relevant to its histone citrullination activity.","method":"Biophysical characterization (CD, fluorescence, ITC), in silico molecular dynamics simulations","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — multiple biophysical methods with molecular dynamics, but functional mutagenesis not performed; single lab","pmids":["35081374"],"is_preprint":false},{"year":2022,"finding":"The armadillo-repeat domain of Plakophilin 1 (PKP1) binds to PADI4 with a dissociation constant of ~1 µM, as demonstrated by fluorescence, CD, ITC, and Western blot analyses; molecular modelling predicts the binding hotspot on PADI4.","method":"Fluorescence, CD, isothermal titration calorimetry (ITC), Western blot, molecular simulations","journal":"Biochimica et biophysica acta. Proteins and proteomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — in vitro biophysical binding only, no cellular functional validation, single lab","pmids":["36372391"],"is_preprint":false},{"year":2022,"finding":"PADI4 promotes osteoblast mineralization indirectly: circ8500 sponges miR-1301-3p, relieving suppression of PADI4; PADI4 then binds to RUNX2 and stabilizes its protein expression by inhibiting the ubiquitin-proteasome pathway, thereby enhancing matrix mineralization.","method":"RNA-seq, luciferase reporter (miRNA sponge), co-immunoprecipitation (PADI4-RUNX2), proteasome inhibition assay, overexpression/knockdown","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP of PADI4-RUNX2 with functional proteasome assay and knockdown phenotype, single lab","pmids":["33363159"],"is_preprint":false},{"year":2022,"finding":"Padi2/Padi4 double knockout (DKO) male mice exhibit delayed puberty, lower testosterone levels, smaller testes, and increased germ cell apoptosis, providing the first in vivo evidence linking PAD2/PAD4 to hormone signaling and male reproductive function.","method":"Conditional double knockout mouse model, breeding trials, serum hormone assays, histology, apoptosis quantification","journal":"Reproductive biology and endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout in vivo with multiple phenotypic readouts, but PAD2 and PAD4 are jointly deleted so contribution of PADI4 alone is not fully resolved","pmids":["36224627"],"is_preprint":false},{"year":2022,"finding":"Conditional Padi4 knockout (single gene) in mice does not significantly affect hematopoietic stem cell (HSC) self-renewal, differentiation, serial transplantation capacity, or haematopoietic regeneration, demonstrating that PADI4 is cell-autonomously dispensable for normal haematopoiesis.","method":"Conditional in vivo Padi4 ablation, acute knockout, serial transplantation, steady-state haematopoiesis analysis","journal":"Biology open","confidence":"High","confidence_rationale":"Tier 2 / Strong — rigorous conditional KO with multiple in vivo functional assays (steady state + injury + serial transplantation); negative result well controlled","pmids":["35603697"],"is_preprint":false},{"year":2022,"finding":"Anti-PADI4 monoclonal antibody suppresses breast tumor growth in mice by inhibiting PADI4-mediated citrullination of fibronectin; citrullinated fibronectin in the tumor microenvironment increases cancer cell proliferation, migration, and glycolytic ATP production while decreasing apoptosis.","method":"In vitro citrullination of fibronectin, cell-based functional assays (proliferation, migration, colony formation), mouse xenograft with PET-CT imaging, Western blot and ELISA for citrullination levels","journal":"Biomedicine & pharmacotherapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reconstituted citrullinated fibronectin functional assay plus in vivo tumor model, single lab","pmids":["35772376"],"is_preprint":false},{"year":2023,"finding":"PADI4 is a key transcriptional target of p53 required for p53-mediated tumor suppression; the p53 Y107H hypomorphic variant selectively fails to transactivate PADI4, and PADI4 itself is tumor-suppressive requiring an intact immune system for this activity.","method":"NMR and crystal structures of p53 Y107H, tumor colony formation assays, mouse cancer models (Y107H knock-in), p53-PADI4 gene signature analysis","journal":"Cancer discovery","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — structural validation (NMR + crystal), in vitro transactivation, multiple in vivo tumor models, immune system dependency tested","pmids":["37140445"],"is_preprint":false},{"year":2023,"finding":"PADI4 directly binds intrinsically disordered protein NUPR1 (and its paralogue NUPR1L) with a dissociation constant of ~18 µM; the binding region on NUPR1 involves a hydrophobic patch around Ala33, mapped by NMR and confirmed by site-directed mutagenesis; the PADI4–NUPR1 complex forms predominantly in the nucleus.","method":"NMR mapping, site-directed mutagenesis, proximity ligation assay (PLA), immunofluorescence, isothermal titration calorimetry, molecular modelling","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — NMR with mutagenesis and ITC in vitro plus cellular PLA/IF, but functional consequence of the complex not yet established; single lab","pmids":["36858171"],"is_preprint":false},{"year":2023,"finding":"MDM2 directly binds PADI4 at the active site region (inhibited by GSK484); the N-terminal domain of MDM2 interacts with PADI4 (residues Thr26, Val28, Phe91, Lys98 most affected), and the interaction occurs in both the nucleus and cytosol; MDM2 may be a substrate for PADI4-mediated citrullination.","method":"Immunofluorescence, proximity ligation assay, NMR chemical shift perturbation, ITC, in silico docking, PADI4 inhibitor (GSK484) competition assay","journal":"Protein science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — NMR mapping, ITC, cellular co-localization, inhibitor competition; citrullination of MDM2 not directly confirmed; single lab","pmids":["37409874"],"is_preprint":false},{"year":2023,"finding":"The intrinsically disordered protein RYBP binds to PADI4 with low-micromolar affinity (~1 µM) in the nucleus and cytosol; AlphaFold2 modelling predicts that PADI4's catalytic domain contacts Arg53 of RYBP at the active site, suggesting potential citrullination of RYBP; combined PADI4 inhibition and PARP inhibition alters cell proliferation.","method":"ITC, fluorescence, proximity ligation assay, immunofluorescence, AlphaFold2-multimer modelling, combination drug assay","journal":"International journal of biological macromolecules","confidence":"Low","confidence_rationale":"Tier 3 / Weak — binding confirmed in vitro and in cellulo, but citrullination of RYBP not directly demonstrated; single lab","pmids":["37399862"],"is_preprint":false},{"year":2024,"finding":"IL-33, whose secretion from HCC cells is increased by lenvatinib via NDUFA4L2 upregulation, triggers NET formation in neutrophils by increasing PADI4 protein expression through the Akt/mTOR signaling pathway; PADI4 inhibition (GSK484) reduces NETs and reverses HCC resistance to lenvatinib by restoring cuproptosis.","method":"siRNA knockdown, Western blot, mTOR inhibitor (rapamycin) experiments, GSK484 PADI4 inhibitor, mouse tumor models, ELISA for NET markers","journal":"Cellular oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic chain established with pathway inhibitors and KD, in vivo validation; single lab","pmids":["39585643"],"is_preprint":false},{"year":2024,"finding":"IL-4 triggers macrophage extracellular trap (MET) formation in M2 macrophages by increasing PADI4 (but not PADI2) mRNA and protein expression; loss of Padi2 and Padi4 (double KO) reduces Nlrp3+ proinflammatory macrophages and promotes Chil3+ antiinflammatory macrophage differentiation, alleviating sepsis-induced lung injury.","method":"Padi2/Padi4 double KO mouse model, single-cell RNA-seq, siRNA knockdown, Nlrp3-KO experiments, in vivo sepsis model","journal":"JCI insight","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — scRNA-seq plus genetic KO with in vivo phenotype; PADI4-specific contribution partially confounded by double KO design","pmids":["39405117"],"is_preprint":false},{"year":2025,"finding":"PADI4 citrullinates PRMT2 at arginine 312, stabilizing PRMT2 protein by preventing its ubiquitin-proteasome-dependent degradation (mediated by disrupted USP7 interaction); stabilized PRMT2 promotes transcription of ID1 and ID2 via histone arginine methylation, increasing cancer stem-like properties and cisplatin resistance in OSCC; PADI4 inhibition (GSK484) or R312 mutation reduces stemness and restores cisplatin sensitivity.","method":"Immunoprecipitation, Western blot, RT-PCR, spheroid growth/CSC marker assays, CCK8 cisplatin resistance assay, site-directed mutagenesis (R312), GSK484 inhibitor","journal":"Clinical and translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, mutagenesis of citrullination site, functional resistance assay, mechanistic chain from citrullination to transcription factor activity; single lab","pmids":["40078091"],"is_preprint":false},{"year":2014,"finding":"PADI4 inhibits TNF-α-induced NF-κB and AP-1 activation in vascular smooth muscle cells, and siRNA knockdown of PADI4 or a PADI4-specific inhibitor attenuates TNF-α-induced VCAM-1 expression and monocyte adhesion, placing PADI4 upstream of NF-κB/AP-1 in TNF-α signaling.","method":"siRNA knockdown, PADI4-specific inhibitor, NF-κB/AP-1 translocation assay, VCAM-1 expression assay, adhesion assay","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic (siRNA) and pharmacological (inhibitor) perturbation with defined pathway readout; single lab","pmids":["25494680"],"is_preprint":false}],"current_model":"PADI4 is a Ca2+-dependent peptidylarginine deiminase that converts arginine to citrulline on multiple nuclear and cytoplasmic substrates (histones H3/H4, Lamin C, NPM1, fibronectin, DNMT3A, PRMT2, hRpn13, and proteasomes); it is transcriptionally activated by p53 and HIFs in response to DNA damage and hypoxia, respectively, acts as a chromatin-modifying co-activator or co-repressor (partnering with Elk-1, Tal1, and Runx2), citrullinates DNMT3A to stabilize it and increase DNA methylation, promotes nuclear fragmentation as an 'apoptotic histone code', translocates to the nucleus via importin α3, and is dispensable for steady-state haematopoiesis but required for HIF-target gene transcription, tumor-suppressive immunity downstream of p53, and NET/MET formation in innate immune cells."},"narrative":{"mechanistic_narrative":"PADI4 is a Ca2+-dependent peptidylarginine deiminase that catalyzes the post-translational citrullination of arginine residues, acting predominantly in the nucleus where it functions as a chromatin-modifying enzyme and stress-responsive transcriptional effector [PMID:12833157, PMID:22334079]. As a stress-induced transcriptional target, PADI4 is transactivated by p53 through an intronic binding site and is required for p53-mediated tumor suppression, an activity dependent on an intact immune system [PMID:19843866, PMID:37140445]; it is independently induced by hypoxia in a HIF-dependent manner and recruited to hypoxia response elements where its histone citrullination is required for transcription of HIF target genes and for tumor growth and angiogenesis [PMID:34452909]. At chromatin, PADI4 partners with sequence-specific transcription factors including Elk-1 and Tal1 to act as a context-dependent co-activator or co-repressor, citrullinating histone H4 and modulating the balance of arginine methylation marks (counteracting PRMT6-deposited H3R2me2a to augment H3K4me3 at target promoters) [PMID:21655091, PMID:24874575]. Beyond histones, PADI4 citrullinates a range of nuclear substrates with downstream functional consequences: it converts NPM1 R197 to drive its nucleolar-to-nucleoplasmic translocation, citrullinates Lamin C and H4R3 to promote chromatin decondensation and an apoptotic nuclear-fragmentation program, and citrullinates DNMT3A and PRMT2 to stabilize these enzymes against ubiquitin-proteasome degradation, thereby increasing DNA methylation and histone arginine methylation respectively [PMID:19843866, PMID:22334079, PMID:24957603, PMID:40078091]. PADI4 enters the nucleus via two nuclear localization sequences that bind the major cargo site of importin α3 [PMID:35883608]. Genetically, Padi4 is dispensable for steady-state haematopoiesis but is required for radiation-induced thymocyte apoptosis and for innate-immune extracellular trap (NET/MET) formation downstream of cytokine signaling [PMID:22334079, PMID:35603697, PMID:39405117]. A functional PADI4 haplotype affecting transcript stability is associated with rheumatoid arthritis, consistent with its citrullination of synovial substrates [PMID:12833157, PMID:15466895].","teleology":[{"year":2003,"claim":"Established PADI4 as a citrullinating enzyme whose genetic variation links it to autoimmune disease, framing citrullination as a source of autoantigens.","evidence":"Case-control association study with mRNA stability assays in rheumatoid arthritis","pmids":["12833157"],"confidence":"Medium","gaps":["Mechanism limited to transcript-stability; no protein-level enzymatic mechanism in this study","Causal substrates in RA not defined here"]},{"year":2004,"claim":"Localized PADI4 protein to inflamed synovial cell types and to citrullinated fibrin, implicating it as the citrullinating agent in inflamed tissue.","evidence":"Immunohistochemistry and double immunofluorescence of RA synovial tissue","pmids":["15466895"],"confidence":"Medium","gaps":["Co-localization is correlative; no knockout or reconstitution to prove fibrin is a direct substrate"]},{"year":2007,"claim":"Defined the upstream transcriptional control of PADI4, showing hormone and basal transcription factor inputs govern its expression.","evidence":"Luciferase reporter, ChIP, and siRNA knockdown in MCF-7 cells","pmids":["17456793"],"confidence":"Medium","gaps":["Promoter mapping in one cell line","Does not address PADI4 catalytic function"]},{"year":2009,"claim":"Connected PADI4 to the p53 DNA-damage axis and identified NPM1 as a direct substrate whose citrullination drives subnuclear relocalization, establishing PADI4 as a stress-responsive enzyme with anti-proliferative activity.","evidence":"p53 transactivation assay, in vivo citrullination, NPM1 R197K mutant localization, siRNA knockdown, growth assays","pmids":["19843866"],"confidence":"High","gaps":["Mechanism by which NPM1 relocalization restrains growth not fully resolved","Single lab"]},{"year":2011,"claim":"Demonstrated PADI4 acts as a chromatin co-activator at active promoters via physical partnership with Elk-1, expanding its role from substrate modification to transcriptional regulation.","evidence":"Genome-wide ChIP-chip, reciprocal Co-IP, EGF-stimulated reporter assays in MCF-7","pmids":["21655091"],"confidence":"High","gaps":["Direct citrullination target driving co-activation not pinpointed","Single cell context"]},{"year":2012,"claim":"Showed PADI4 citrullinates histone H4R3 and Lamin C to drive chromatin decondensation and apoptotic nuclear fragmentation, and a knockout phenotype linked it to radiation-induced apoptosis in vivo.","evidence":"In vitro/in vivo citrullination, Padi4-knockout mice, ectopic expression, irradiation model","pmids":["22334079"],"confidence":"High","gaps":["Precise contribution of each substrate to nuclear fragmentation unresolved","Tissue scope of apoptotic role limited"]},{"year":2014,"claim":"Resolved PADI4's dual transcriptional logic, acting as co-activator (IL6ST) or repressor (CTCF) through Tal1 and antagonism of PRMT6-deposited arginine methylation.","evidence":"Reciprocal Co-IP, ChIP for multiple histone marks, expression analysis in hematopoietic cells","pmids":["24874575"],"confidence":"High","gaps":["What dictates activator-versus-repressor outcome at a given locus is unknown"]},{"year":2014,"claim":"Identified DNMT3A as a substrate whose citrullination stabilizes the protein and increases DNA methylation, linking citrullination to the epigenetic methylation machinery.","evidence":"Co-IP, in vitro/in vivo citrullination, pulse-chase stability, Padi4-KO MEFs, bisulfite pyrosequencing","pmids":["24957603"],"confidence":"High","gaps":["Citrullinated residue(s) on DNMT3A not enumerated","Genome-wide methylation impact not mapped"]},{"year":2014,"claim":"Placed PADI4 upstream of NF-κB/AP-1 in TNF-α signaling, broadening its role to inflammatory signal transduction in vascular cells.","evidence":"siRNA knockdown, PADI4 inhibitor, NF-κB/AP-1 translocation and VCAM-1/adhesion assays","pmids":["25494680"],"confidence":"Medium","gaps":["Direct citrullination substrate in this pathway not identified","Single lab and cell type"]},{"year":2017,"claim":"Detailed PADI4 repression of p21 in synoviocytes via histone arginine mark editing, tying its chromatin activity to apoptosis resistance in disease.","evidence":"siRNA/overexpression, ChIP at p21 promoter, flow cytometry apoptosis","pmids":["28367100"],"confidence":"Medium","gaps":["Single lab","Mechanistic link between H3 modification changes and p21 silencing partly correlative"]},{"year":2017,"claim":"Proposed crosstalk between citrullination and ubiquitination through a PADI4-SYVN1 interaction.","evidence":"Co-IP and overexpression with ubiquitination assays","pmids":["29039504"],"confidence":"Low","gaps":["Single Co-IP and overexpression without reconstitution or mutagenesis","SYVN1 not shown to be a citrullination substrate"]},{"year":2021,"claim":"Established PADI4 as a HIF-recruited co-factor required for histone citrullination at hypoxia response elements and for HIF-driven tumor growth, defining a hypoxia arm of PADI4 function.","evidence":"RNA-seq, ChIP at HREs, siRNA knockdown, mouse xenograft tumor models","pmids":["34452909"],"confidence":"High","gaps":["How HIFs recruit PADI4 mechanistically not defined","Histone target residues at HREs not enumerated"]},{"year":2022,"claim":"Mapped the structural basis of PADI4 nuclear import, identifying two NLSs that engage the importin α3 cargo site.","evidence":"Fluorescence, CD, ITC, molecular docking","pmids":["35883608"],"confidence":"Medium","gaps":["No cell-based nuclear import functional assay","Single lab"]},{"year":2022,"claim":"Characterized PADI4 quaternary structure and pH/Ca2+ dependence, relating its native dimeric fold to citrullination activity.","evidence":"CD, fluorescence, ITC, molecular dynamics simulations","pmids":["35081374"],"confidence":"Medium","gaps":["Functional mutagenesis not performed","Activity correlation inferred, not directly assayed"]},{"year":2022,"claim":"Extended PADI4 substrate range into the proteasome system, citrullinating and stabilizing hRpn13 and modulating proteasome peptidase activity.","evidence":"Proteomics, PADI4 inhibitor, proteasome peptidase assay, PROTAC co-depletion in myeloma","pmids":["38151017"],"confidence":"Medium","gaps":["Citrullinated residues on proteasome subunits not mapped","Single lab"]},{"year":2022,"claim":"Identified PKP1 as a direct binding partner of PADI4 by biophysics.","evidence":"Fluorescence, CD, ITC, Western blot, molecular simulation","pmids":["36372391"],"confidence":"Low","gaps":["In vitro binding only with no cellular functional validation","PKP1 not shown to be a substrate"]},{"year":2022,"claim":"Linked PADI4 to RUNX2 stabilization and osteoblast mineralization through a circRNA/miRNA-controlled, proteasome-inhibiting mechanism.","evidence":"RNA-seq, miRNA-sponge luciferase, PADI4-RUNX2 Co-IP, proteasome inhibition, knockdown/overexpression","pmids":["33363159"],"confidence":"Medium","gaps":["Whether RUNX2 stabilization requires citrullination not established","Single lab"]},{"year":2022,"claim":"Provided in vivo evidence linking PAD2/PAD4 to male reproductive function and hormone signaling.","evidence":"Conditional Padi2/Padi4 double-knockout mice, hormone assays, histology, apoptosis quantification","pmids":["36224627"],"confidence":"Medium","gaps":["PADI4-specific contribution confounded by joint deletion with PADI2","Molecular substrate in testis unknown"]},{"year":2022,"claim":"Showed PADI4 is dispensable for normal and regenerative haematopoiesis, delimiting where its function is required.","evidence":"Conditional single-gene Padi4 knockout, serial transplantation, steady-state and injury analysis","pmids":["35603697"],"confidence":"High","gaps":["Does not exclude roles under non-hematopoietic stress contexts"]},{"year":2022,"claim":"Demonstrated PADI4 citrullination of fibronectin remodels the tumor microenvironment to favor proliferation and glycolysis, and that antibody targeting suppresses tumor growth.","evidence":"In vitro fibronectin citrullination, functional cell assays, mouse xenograft with PET-CT, ELISA","pmids":["35772376"],"confidence":"Medium","gaps":["Citrullinated fibronectin residues not mapped","Single lab"]},{"year":2023,"claim":"Established PADI4 as a critical, immune-dependent effector of p53 tumor suppression, with a hypomorphic p53 variant selectively failing to induce it.","evidence":"NMR/crystal structures of p53 Y107H, colony formation, Y107H knock-in mouse cancer models, gene-signature analysis","pmids":["37140445"],"confidence":"High","gaps":["Immune effector mechanism downstream of PADI4 not fully resolved","Direct citrullination substrate mediating tumor suppression unknown"]},{"year":2023,"claim":"Identified a nuclear PADI4-NUPR1 complex by structure-guided binding studies, expanding the PADI4 interactome to intrinsically disordered proteins.","evidence":"NMR mapping, mutagenesis, PLA, immunofluorescence, ITC, modelling","pmids":["36858171"],"confidence":"Medium","gaps":["Functional consequence of the complex not established","NUPR1 not confirmed as substrate"]},{"year":2023,"claim":"Mapped a direct MDM2-PADI4 interaction at the PADI4 active site, hinting MDM2 could be a substrate and integrating PADI4 into the p53/MDM2 axis.","evidence":"IF, PLA, NMR chemical shift perturbation, ITC, docking, GSK484 competition","pmids":["37409874"],"confidence":"Medium","gaps":["MDM2 citrullination not directly demonstrated","Functional outcome of interaction unknown"]},{"year":2023,"claim":"Identified RYBP as a low-micromolar PADI4 binder and showed combined PADI4/PARP inhibition alters proliferation.","evidence":"ITC, fluorescence, PLA, immunofluorescence, AlphaFold2-multimer modelling, combination drug assay","pmids":["37399862"],"confidence":"Low","gaps":["RYBP citrullination not directly demonstrated","Single lab; mechanism of drug synergy unresolved"]},{"year":2024,"claim":"Placed PADI4 in a cytokine-driven NET pathway, with IL-33/Akt/mTOR-induced PADI4 driving NET formation and tumor drug resistance.","evidence":"siRNA, Western blot, rapamycin and GSK484 experiments, mouse tumor models, NET-marker ELISA","pmids":["39585643"],"confidence":"Medium","gaps":["Substrate driving NET formation not defined here","Single lab"]},{"year":2024,"claim":"Extended extracellular-trap function to macrophages, showing IL-4-induced PADI4 drives MET formation and shapes macrophage polarization in sepsis injury.","evidence":"Padi2/Padi4 double KO, scRNA-seq, siRNA, Nlrp3-KO, in vivo sepsis model","pmids":["39405117"],"confidence":"Medium","gaps":["PADI4-specific contribution confounded by double KO","Direct substrate in MET formation not identified"]},{"year":2025,"claim":"Showed PADI4 citrullinates PRMT2 at R312 to block its ubiquitin-dependent degradation, driving ID1/ID2 transcription, cancer stemness, and chemoresistance.","evidence":"IP, Western blot, RT-PCR, spheroid/CSC assays, cisplatin resistance assay, R312 mutagenesis, GSK484","pmids":["40078091"],"confidence":"Medium","gaps":["Single lab","Generalizability beyond OSCC not tested"]},{"year":null,"claim":"The unifying determinant of PADI4's context-dependent outcomes — how substrate selection and activator-versus-repressor behavior are governed across the p53, HIF, and innate-immune programs — remains undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model linking recruitment partners to substrate choice","Direct citrullination substrate mediating immune-dependent tumor suppression unknown","Mechanism of recruitment to specific promoters by different transcription factors unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3,5,7,12,18,25]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,5,7]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,6,10]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[5,6]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3,5,11,20]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[3]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[21,22]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[4,5,6,10]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[3,4,10,19]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[5,10]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[23,24]}],"complexes":[],"partners":["ELK-1","TAL1","DNMT3A","NPM1","IMPORTIN Α3","MDM2","NUPR1","RUNX2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UM07","full_name":"Protein-arginine deiminase type-4","aliases":["HL-60 PAD","Peptidylarginine deiminase IV","Protein-arginine deiminase type IV"],"length_aa":663,"mass_kda":74.1,"function":"Catalyzes the citrullination/deimination of arginine residues of proteins such as histones, thereby playing a key role in histone code and regulation of stem cell maintenance (PubMed:15339660, PubMed:15345777, PubMed:16567635, PubMed:21245532). Citrullinates histone H1 at 'Arg-54' (to form H1R54ci), histone H3 at 'Arg-2', 'Arg-8', 'Arg-17' and/or 'Arg-26' (to form H3R2ci, H3R8ci, H3R17ci, H3R26ci, respectively) and histone H4 at 'Arg-3' (to form H4R3ci) (PubMed:15339660, PubMed:15345777, PubMed:16567635, PubMed:21245532). Acts as a key regulator of stem cell maintenance by mediating citrullination of histone H1: citrullination of 'Arg-54' of histone H1 (H1R54ci) results in H1 displacement from chromatin and global chromatin decondensation, thereby promoting pluripotency and stem cell maintenance (PubMed:15339660, PubMed:15345777, PubMed:16567635, PubMed:21245532). Promotes profound chromatin decondensation during the innate immune response to infection in neutrophils by mediating formation of H1R54ci (PubMed:18209087). Required for the formation of neutrophil extracellular traps (NETs); NETs are mainly composed of DNA fibers and are released by neutrophils to bind pathogens during inflammation (By similarity). Citrullination of histone H3 prevents their methylation by CARM1 and HRMT1L2/PRMT1 and represses transcription (PubMed:15345777). Citrullinates EP300/P300 at 'Arg-2142', which favors its interaction with NCOA2/GRIP1 (PubMed:15731352)","subcellular_location":"Cytoplasm; Nucleus; Cytoplasmic granule","url":"https://www.uniprot.org/uniprotkb/Q9UM07/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PADI4","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PADI4","total_profiled":1310},"omim":[{"mim_id":"612088","title":"C-TYPE LECTIN DOMAIN FAMILY 12, MEMBER A; CLEC12A","url":"https://www.omim.org/entry/612088"},{"mim_id":"610363","title":"PEPTIDYLARGININE DEIMINASE, TYPE VI; PADI6","url":"https://www.omim.org/entry/610363"},{"mim_id":"607935","title":"PEPTIDYLARGININE DEIMINASE, TYPE II; PADI2","url":"https://www.omim.org/entry/607935"},{"mim_id":"607934","title":"PEPTIDYLARGININE DEIMINASE, TYPE I; PADI1","url":"https://www.omim.org/entry/607934"},{"mim_id":"606755","title":"PEPTIDYLARGININE DEIMINASE, TYPE III; PADI3","url":"https://www.omim.org/entry/606755"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":99.4},{"tissue":"lymphoid tissue","ntpm":28.9}],"url":"https://www.proteinatlas.org/search/PADI4"},"hgnc":{"alias_symbol":["PAD","PDI5","PDI4"],"prev_symbol":["PADI5"]},"alphafold":{"accession":"Q9UM07","domains":[{"cath_id":"2.60.40.1860","chopping":"5-113","consensus_level":"high","plddt":87.4624,"start":5,"end":113},{"cath_id":"2.60.40.1700","chopping":"121-294","consensus_level":"high","plddt":92.1274,"start":121,"end":294},{"cath_id":"3.75.10.10","chopping":"298-661","consensus_level":"medium","plddt":97.5962,"start":298,"end":661}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UM07","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UM07-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UM07-F1-predicted_aligned_error_v6.png","plddt_mean":94.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PADI4","jax_strain_url":"https://www.jax.org/strain/search?query=PADI4"},"sequence":{"accession":"Q9UM07","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UM07.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UM07/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UM07"}},"corpus_meta":[{"pmid":"12833157","id":"PMC_12833157","title":"Functional 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replication study in a Southern Mexican population.","date":"2017","source":"Human immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28551357","citation_count":14,"is_preprint":false},{"pmid":"15338034","id":"PMC_15338034","title":"High variability of peptidylarginine deiminase 4 (PADI4) in a healthy white population: characterization of six new variants of PADI4 exons 2-4 by a novel haplotype-specific sequencing-based approach.","date":"2004","source":"Journal of molecular medicine (Berlin, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/15338034","citation_count":14,"is_preprint":false},{"pmid":"33363159","id":"PMC_33363159","title":"CircRNA hsa_circ_0008500 Acts as a miR-1301-3p Sponge to Promote Osteoblast Mineralization by Upregulating PADI4.","date":"2020","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/33363159","citation_count":14,"is_preprint":false},{"pmid":"39529192","id":"PMC_39529192","title":"Sorafenib-induced macrophage extracellular traps via ARHGDIG/IL4/PADI4 axis confer drug resistance through inhibiting ferroptosis in hepatocellular carcinoma.","date":"2024","source":"Biology direct","url":"https://pubmed.ncbi.nlm.nih.gov/39529192","citation_count":13,"is_preprint":false},{"pmid":"14557050","id":"PMC_14557050","title":"Association of PADI4 and rheumatoid arthritis: a successful multidisciplinary approach.","date":"2003","source":"Trends in molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/14557050","citation_count":13,"is_preprint":false},{"pmid":"33193078","id":"PMC_33193078","title":"Analysis of Polymorphisms rs7093069-IL-2RA, rs7138803-FAIM2, and rs1748033-PADI4 in the Group of Adolescents With Autoimmune Thyroid Diseases.","date":"2020","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/33193078","citation_count":13,"is_preprint":false},{"pmid":"24454473","id":"PMC_24454473","title":"PADI4 haplotypes in association with RA Mexican patients, a new prospect for antigen modulation.","date":"2013","source":"Clinical & developmental immunology","url":"https://pubmed.ncbi.nlm.nih.gov/24454473","citation_count":13,"is_preprint":false},{"pmid":"22907585","id":"PMC_22907585","title":"Decreased PADI4 mRNA association with global hypomethylation in hepatocellular carcinoma during HBV exposure.","date":"2013","source":"Cell biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/22907585","citation_count":13,"is_preprint":false},{"pmid":"39405117","id":"PMC_39405117","title":"Loss of PADI2 and PADI4 ameliorates sepsis-induced acute lung injury by suppressing NLRP3+ macrophages.","date":"2024","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/39405117","citation_count":12,"is_preprint":false},{"pmid":"28653215","id":"PMC_28653215","title":"NLRP1, PTPN22 and PADI4 gene polymorphisms and rheumatoid arthritis in ACPA-positive Singaporean Chinese.","date":"2017","source":"Rheumatology 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functional polymorphism on PADI-4 gene and its association with arthritis onset.","date":"2021","source":"Saudi journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35197789","citation_count":9,"is_preprint":false},{"pmid":"36135205","id":"PMC_36135205","title":"PADI4 Haplotypes Contribute to mRNA Expression, the Enzymatic Activity of Peptidyl Arginine Deaminase and Rheumatoid Arthritis Risk in Patients from Western Mexico.","date":"2022","source":"Current issues in molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/36135205","citation_count":9,"is_preprint":false},{"pmid":"29039504","id":"PMC_29039504","title":"Inhibitory effects of ubiquitination of synoviolin by PADI4.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/29039504","citation_count":9,"is_preprint":false},{"pmid":"29858238","id":"PMC_29858238","title":"Lack of Association among Peptidyl Arginine Deiminase Type 4 Autoantibodies, PADI4 Polymorphisms, and Clinical Characteristics in Rheumatoid Arthritis.","date":"2018","source":"The Journal of rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/29858238","citation_count":9,"is_preprint":false},{"pmid":"23450494","id":"PMC_23450494","title":"[Association of polymorphisms of PTPN22 and PADI4 genes with rheumatoid arthritis in Yunnan].","date":"2013","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23450494","citation_count":9,"is_preprint":false},{"pmid":"32163016","id":"PMC_32163016","title":"PADI4 (rs2240340), PDCD1 (rs10204525), and CTLA4 (231775) gene polymorphisms and polyarticular juvenile idiopathic arthritis.","date":"2020","source":"British journal of biomedical science","url":"https://pubmed.ncbi.nlm.nih.gov/32163016","citation_count":8,"is_preprint":false},{"pmid":"36372391","id":"PMC_36372391","title":"The armadillo-repeat domain of Plakophilin 1 binds to human enzyme 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a functional haplotype of PADI4 affects mRNA transcript stability and is associated with increased citrullinated peptide autoantigen production in rheumatoid arthritis.\",\n      \"method\": \"Case-control association study with mRNA stability assays\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional haplotype effect on mRNA stability shown, replicated across multiple Asian population studies, but mechanistic detail limited to transcript-level assays\",\n      \"pmids\": [\"12833157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PADI4 protein is expressed in T cells, B cells, macrophages, neutrophils, fibroblast-like cells, and endothelial cells in RA synovium; it co-localizes with citrullinated fibrin and apoptotic cells in fibrin deposits, suggesting PADI4 is responsible for fibrin citrullination in the inflamed synovium.\",\n      \"method\": \"Immunohistochemistry, double immunofluorescent labelling, and western blotting of synovial tissue\",\n      \"journal\": \"Rheumatology (Oxford, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-localization by multiple imaging methods in tissue, but no functional knockout or reconstitution to prove causality\",\n      \"pmids\": [\"15466895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Estrogen receptor-α (ERα) stimulates PADI4 transcription in MCF-7 cells through both classical and non-classical ER-mediated pathways; transcription factors AP-1, Sp1/Sp3, and NF-Y bind the minimal promoter (−348 bp) of PADI4 and cooperatively regulate its expression, as shown by ChIP and siRNA knockdown.\",\n      \"method\": \"Luciferase reporter assays, chromatin immunoprecipitation (ChIP), siRNA knockdown\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus siRNA functional validation, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"17456793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"p53 transcriptionally transactivates PADI4 via an intronic p53-binding site; PADI4 in turn citrullinated the histone chaperone nucleophosmin (NPM1) at arginine 197 in vivo, causing NPM1 translocation from nucleoli to nucleoplasm. Knockdown of PADI4 or p53 inhibited DNA-damage-induced protein citrullination; ectopic PADI4 expression inhibited tumor cell growth.\",\n      \"method\": \"p53 transactivation assay, in vivo citrullination assay, NPM1 R197K mutant localization, siRNA knockdown, cell growth assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (transcriptional assay, site-directed mutagenesis of NPM1, siRNA knockdown with functional readout), single lab but strong mechanistic chain\",\n      \"pmids\": [\"19843866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PADI4 is enriched at gene promoters near transcription start sites of actively transcribed genes in MCF-7 cells; PADI4 physically associates with transcription factor Elk-1, and following EGF stimulation PADI4 catalytic activity facilitates Elk-1 phosphorylation, histone H4 acetylation, and c-Fos transcriptional activation, defining a novel co-activator role for PADI4.\",\n      \"method\": \"ChIP-chip (genome-wide), co-immunoprecipitation, EGF stimulation assays, transcriptional reporter assays\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide ChIP-chip plus reciprocal Co-IP plus catalytic-activity-dependent functional assay in one study\",\n      \"pmids\": [\"21655091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In response to DNA damage, p53 activates PADI4, which citrullinates arginine 3 of histone H4 (cit-H4R3) and also citrullinates Lamin C; cit-H4R3 localizes around fragmented nuclei in apoptotic cells; ectopic PADI4 expression causes chromatin decondensation and promotes DNA cleavage; Padi4-knockout mice show resistance to radiation-induced apoptosis in the thymus.\",\n      \"method\": \"In vivo and in vitro citrullination assays, Padi4 knockout mice, ectopic expression, immunofluorescence, irradiation model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro and in vivo citrullination, genetic knockout phenotype, ectopic expression, multiple substrates validated\",\n      \"pmids\": [\"22334079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PADI4 interacts with transcription factor Tal1 and acts as an epigenetic co-activator at the IL6ST gene by counteracting the repressive H3R2me2a mark placed by PRMT6, thereby augmenting the active H3K4me3 mark and increasing IL6ST expression; at the CTCF promoter, PADI4 acts instead as a repressor.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, gene expression analysis in hematopoietic cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ChIP for multiple histone marks, expression readouts at specific target genes, mechanistic chain fully described\",\n      \"pmids\": [\"24874575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PADI4 physically interacts with DNMT3A and citrullinates it both in vitro and in vivo; citrullination of the region upstream of the PWWP domain of DNMT3A by catalytically active PADI4 stabilizes the DNMT3A protein, increases DNA methyltransferase activity, and increases CpG methylation at the p21 promoter.\",\n      \"method\": \"Co-immunoprecipitation (endogenous and overexpressed), in vitro and in vivo citrullination assays, pulse-chase protein stability, Padi4-knockout MEFs, bisulfite pyrosequencing\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution, catalytic-activity mutagenesis, KO cell validation, and bisulfite sequencing of functional target in one study\",\n      \"pmids\": [\"24957603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PADI4 suppresses p21 transcription in RA fibroblast-like synoviocytes by binding to the p21 promoter and altering histone H3 arginine modifications (global H3 citrullination and H3R17 methylation); PADI4 knockdown promotes apoptosis and increases p53 and p21 expression, while ectopic PADI4 inhibits adriamycin-induced apoptosis.\",\n      \"method\": \"siRNA knockdown, overexpression, ChIP for PADI4 and histone marks at p21 promoter, flow cytometry apoptosis\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus functional knockdown/overexpression, single lab\",\n      \"pmids\": [\"28367100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PADI4 directly interacts with the E3 ubiquitin ligase synoviolin (SYVN1), and overexpression of PADI4 suppresses ubiquitination of cellular proteins, suggesting crosstalk between citrullination and ubiquitination pathways in RA synoviocytes.\",\n      \"method\": \"Co-immunoprecipitation, overexpression, ubiquitination assays\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP and overexpression, single lab, no in vitro reconstitution or mutagenesis\",\n      \"pmids\": [\"29039504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PADI4 expression is induced by hypoxia in a HIF-dependent manner; PADI4 is recruited by HIFs to hypoxia response elements (HREs) and is required for histone citrullination at HREs and transcription of nearly all HIF target genes in breast cancer cells; PADI4 loss reduces breast and liver tumor growth and angiogenesis in mice.\",\n      \"method\": \"RNA sequencing, ChIP, siRNA knockdown, mouse xenograft tumor models, immunohistochemistry\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide RNA-seq, ChIP at HREs, in vivo tumor models, multiple cell lines, HIF-dependency confirmed\",\n      \"pmids\": [\"34452909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PADI4 binds to importin α3 (Impα3) with an affinity of ~1–5 µM through two nuclear localization sequences (Pro56–Ser83 and Arg495–Ile526); both NLS-containing peptides bind at the major cargo-binding site of importin α3, explaining nuclear translocation of PADI4.\",\n      \"method\": \"Fluorescence, circular dichroism, isothermal titration calorimetry (ITC), molecular docking\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — biophysical in vitro binding with mutagenesis-guided mapping and ITC, but single lab; no cell-based nuclear import functional assay reported\",\n      \"pmids\": [\"35883608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PADI4 citrullinates and stabilizes hRpn13 (proteasome substrate receptor); PADI4 also citrullinates proteasomes (shown by in-cell citrullination), and proteasomes from PADI4-inhibited myeloma cells exhibit reduced peptidase activity.\",\n      \"method\": \"Proteomic analysis, PADI4 inhibitor treatment, proteasome peptidase activity assay, PROTAC co-depletion\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional proteasome activity assay plus proteomic co-depletion, single lab\",\n      \"pmids\": [\"38151017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PADI4 exists in a dimeric native structure within a narrow pH range (6.5–8.0) and requires Ca2+ for stability; the protein unfolds through at least one intermediate under guanidinium denaturation, and the native structure is strongly pH-dependent, relevant to its histone citrullination activity.\",\n      \"method\": \"Biophysical characterization (CD, fluorescence, ITC), in silico molecular dynamics simulations\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple biophysical methods with molecular dynamics, but functional mutagenesis not performed; single lab\",\n      \"pmids\": [\"35081374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The armadillo-repeat domain of Plakophilin 1 (PKP1) binds to PADI4 with a dissociation constant of ~1 µM, as demonstrated by fluorescence, CD, ITC, and Western blot analyses; molecular modelling predicts the binding hotspot on PADI4.\",\n      \"method\": \"Fluorescence, CD, isothermal titration calorimetry (ITC), Western blot, molecular simulations\",\n      \"journal\": \"Biochimica et biophysica acta. Proteins and proteomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — in vitro biophysical binding only, no cellular functional validation, single lab\",\n      \"pmids\": [\"36372391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PADI4 promotes osteoblast mineralization indirectly: circ8500 sponges miR-1301-3p, relieving suppression of PADI4; PADI4 then binds to RUNX2 and stabilizes its protein expression by inhibiting the ubiquitin-proteasome pathway, thereby enhancing matrix mineralization.\",\n      \"method\": \"RNA-seq, luciferase reporter (miRNA sponge), co-immunoprecipitation (PADI4-RUNX2), proteasome inhibition assay, overexpression/knockdown\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP of PADI4-RUNX2 with functional proteasome assay and knockdown phenotype, single lab\",\n      \"pmids\": [\"33363159\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Padi2/Padi4 double knockout (DKO) male mice exhibit delayed puberty, lower testosterone levels, smaller testes, and increased germ cell apoptosis, providing the first in vivo evidence linking PAD2/PAD4 to hormone signaling and male reproductive function.\",\n      \"method\": \"Conditional double knockout mouse model, breeding trials, serum hormone assays, histology, apoptosis quantification\",\n      \"journal\": \"Reproductive biology and endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout in vivo with multiple phenotypic readouts, but PAD2 and PAD4 are jointly deleted so contribution of PADI4 alone is not fully resolved\",\n      \"pmids\": [\"36224627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Conditional Padi4 knockout (single gene) in mice does not significantly affect hematopoietic stem cell (HSC) self-renewal, differentiation, serial transplantation capacity, or haematopoietic regeneration, demonstrating that PADI4 is cell-autonomously dispensable for normal haematopoiesis.\",\n      \"method\": \"Conditional in vivo Padi4 ablation, acute knockout, serial transplantation, steady-state haematopoiesis analysis\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — rigorous conditional KO with multiple in vivo functional assays (steady state + injury + serial transplantation); negative result well controlled\",\n      \"pmids\": [\"35603697\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Anti-PADI4 monoclonal antibody suppresses breast tumor growth in mice by inhibiting PADI4-mediated citrullination of fibronectin; citrullinated fibronectin in the tumor microenvironment increases cancer cell proliferation, migration, and glycolytic ATP production while decreasing apoptosis.\",\n      \"method\": \"In vitro citrullination of fibronectin, cell-based functional assays (proliferation, migration, colony formation), mouse xenograft with PET-CT imaging, Western blot and ELISA for citrullination levels\",\n      \"journal\": \"Biomedicine & pharmacotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reconstituted citrullinated fibronectin functional assay plus in vivo tumor model, single lab\",\n      \"pmids\": [\"35772376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PADI4 is a key transcriptional target of p53 required for p53-mediated tumor suppression; the p53 Y107H hypomorphic variant selectively fails to transactivate PADI4, and PADI4 itself is tumor-suppressive requiring an intact immune system for this activity.\",\n      \"method\": \"NMR and crystal structures of p53 Y107H, tumor colony formation assays, mouse cancer models (Y107H knock-in), p53-PADI4 gene signature analysis\",\n      \"journal\": \"Cancer discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — structural validation (NMR + crystal), in vitro transactivation, multiple in vivo tumor models, immune system dependency tested\",\n      \"pmids\": [\"37140445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PADI4 directly binds intrinsically disordered protein NUPR1 (and its paralogue NUPR1L) with a dissociation constant of ~18 µM; the binding region on NUPR1 involves a hydrophobic patch around Ala33, mapped by NMR and confirmed by site-directed mutagenesis; the PADI4–NUPR1 complex forms predominantly in the nucleus.\",\n      \"method\": \"NMR mapping, site-directed mutagenesis, proximity ligation assay (PLA), immunofluorescence, isothermal titration calorimetry, molecular modelling\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR with mutagenesis and ITC in vitro plus cellular PLA/IF, but functional consequence of the complex not yet established; single lab\",\n      \"pmids\": [\"36858171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MDM2 directly binds PADI4 at the active site region (inhibited by GSK484); the N-terminal domain of MDM2 interacts with PADI4 (residues Thr26, Val28, Phe91, Lys98 most affected), and the interaction occurs in both the nucleus and cytosol; MDM2 may be a substrate for PADI4-mediated citrullination.\",\n      \"method\": \"Immunofluorescence, proximity ligation assay, NMR chemical shift perturbation, ITC, in silico docking, PADI4 inhibitor (GSK484) competition assay\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — NMR mapping, ITC, cellular co-localization, inhibitor competition; citrullination of MDM2 not directly confirmed; single lab\",\n      \"pmids\": [\"37409874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The intrinsically disordered protein RYBP binds to PADI4 with low-micromolar affinity (~1 µM) in the nucleus and cytosol; AlphaFold2 modelling predicts that PADI4's catalytic domain contacts Arg53 of RYBP at the active site, suggesting potential citrullination of RYBP; combined PADI4 inhibition and PARP inhibition alters cell proliferation.\",\n      \"method\": \"ITC, fluorescence, proximity ligation assay, immunofluorescence, AlphaFold2-multimer modelling, combination drug assay\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — binding confirmed in vitro and in cellulo, but citrullination of RYBP not directly demonstrated; single lab\",\n      \"pmids\": [\"37399862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IL-33, whose secretion from HCC cells is increased by lenvatinib via NDUFA4L2 upregulation, triggers NET formation in neutrophils by increasing PADI4 protein expression through the Akt/mTOR signaling pathway; PADI4 inhibition (GSK484) reduces NETs and reverses HCC resistance to lenvatinib by restoring cuproptosis.\",\n      \"method\": \"siRNA knockdown, Western blot, mTOR inhibitor (rapamycin) experiments, GSK484 PADI4 inhibitor, mouse tumor models, ELISA for NET markers\",\n      \"journal\": \"Cellular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic chain established with pathway inhibitors and KD, in vivo validation; single lab\",\n      \"pmids\": [\"39585643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IL-4 triggers macrophage extracellular trap (MET) formation in M2 macrophages by increasing PADI4 (but not PADI2) mRNA and protein expression; loss of Padi2 and Padi4 (double KO) reduces Nlrp3+ proinflammatory macrophages and promotes Chil3+ antiinflammatory macrophage differentiation, alleviating sepsis-induced lung injury.\",\n      \"method\": \"Padi2/Padi4 double KO mouse model, single-cell RNA-seq, siRNA knockdown, Nlrp3-KO experiments, in vivo sepsis model\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — scRNA-seq plus genetic KO with in vivo phenotype; PADI4-specific contribution partially confounded by double KO design\",\n      \"pmids\": [\"39405117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PADI4 citrullinates PRMT2 at arginine 312, stabilizing PRMT2 protein by preventing its ubiquitin-proteasome-dependent degradation (mediated by disrupted USP7 interaction); stabilized PRMT2 promotes transcription of ID1 and ID2 via histone arginine methylation, increasing cancer stem-like properties and cisplatin resistance in OSCC; PADI4 inhibition (GSK484) or R312 mutation reduces stemness and restores cisplatin sensitivity.\",\n      \"method\": \"Immunoprecipitation, Western blot, RT-PCR, spheroid growth/CSC marker assays, CCK8 cisplatin resistance assay, site-directed mutagenesis (R312), GSK484 inhibitor\",\n      \"journal\": \"Clinical and translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, mutagenesis of citrullination site, functional resistance assay, mechanistic chain from citrullination to transcription factor activity; single lab\",\n      \"pmids\": [\"40078091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PADI4 inhibits TNF-α-induced NF-κB and AP-1 activation in vascular smooth muscle cells, and siRNA knockdown of PADI4 or a PADI4-specific inhibitor attenuates TNF-α-induced VCAM-1 expression and monocyte adhesion, placing PADI4 upstream of NF-κB/AP-1 in TNF-α signaling.\",\n      \"method\": \"siRNA knockdown, PADI4-specific inhibitor, NF-κB/AP-1 translocation assay, VCAM-1 expression assay, adhesion assay\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic (siRNA) and pharmacological (inhibitor) perturbation with defined pathway readout; single lab\",\n      \"pmids\": [\"25494680\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PADI4 is a Ca2+-dependent peptidylarginine deiminase that converts arginine to citrulline on multiple nuclear and cytoplasmic substrates (histones H3/H4, Lamin C, NPM1, fibronectin, DNMT3A, PRMT2, hRpn13, and proteasomes); it is transcriptionally activated by p53 and HIFs in response to DNA damage and hypoxia, respectively, acts as a chromatin-modifying co-activator or co-repressor (partnering with Elk-1, Tal1, and Runx2), citrullinates DNMT3A to stabilize it and increase DNA methylation, promotes nuclear fragmentation as an 'apoptotic histone code', translocates to the nucleus via importin α3, and is dispensable for steady-state haematopoiesis but required for HIF-target gene transcription, tumor-suppressive immunity downstream of p53, and NET/MET formation in innate immune cells.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PADI4 is a Ca2+-dependent peptidylarginine deiminase that catalyzes the post-translational citrullination of arginine residues, acting predominantly in the nucleus where it functions as a chromatin-modifying enzyme and stress-responsive transcriptional effector [#0, #5]. As a stress-induced transcriptional target, PADI4 is transactivated by p53 through an intronic binding site and is required for p53-mediated tumor suppression, an activity dependent on an intact immune system [#3, #19]; it is independently induced by hypoxia in a HIF-dependent manner and recruited to hypoxia response elements where its histone citrullination is required for transcription of HIF target genes and for tumor growth and angiogenesis [#10]. At chromatin, PADI4 partners with sequence-specific transcription factors including Elk-1 and Tal1 to act as a context-dependent co-activator or co-repressor, citrullinating histone H4 and modulating the balance of arginine methylation marks (counteracting PRMT6-deposited H3R2me2a to augment H3K4me3 at target promoters) [#4, #6]. Beyond histones, PADI4 citrullinates a range of nuclear substrates with downstream functional consequences: it converts NPM1 R197 to drive its nucleolar-to-nucleoplasmic translocation, citrullinates Lamin C and H4R3 to promote chromatin decondensation and an apoptotic nuclear-fragmentation program, and citrullinates DNMT3A and PRMT2 to stabilize these enzymes against ubiquitin-proteasome degradation, thereby increasing DNA methylation and histone arginine methylation respectively [#3, #5, #7, #25]. PADI4 enters the nucleus via two nuclear localization sequences that bind the major cargo site of importin \\u03b13 [#11]. Genetically, Padi4 is dispensable for steady-state haematopoiesis but is required for radiation-induced thymocyte apoptosis and for innate-immune extracellular trap (NET/MET) formation downstream of cytokine signaling [#5, #17, #24]. A functional PADI4 haplotype affecting transcript stability is associated with rheumatoid arthritis, consistent with its citrullination of synovial substrates [#0, #1].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established PADI4 as a citrullinating enzyme whose genetic variation links it to autoimmune disease, framing citrullination as a source of autoantigens.\",\n      \"evidence\": \"Case-control association study with mRNA stability assays in rheumatoid arthritis\",\n      \"pmids\": [\"12833157\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism limited to transcript-stability; no protein-level enzymatic mechanism in this study\", \"Causal substrates in RA not defined here\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Localized PADI4 protein to inflamed synovial cell types and to citrullinated fibrin, implicating it as the citrullinating agent in inflamed tissue.\",\n      \"evidence\": \"Immunohistochemistry and double immunofluorescence of RA synovial tissue\",\n      \"pmids\": [\"15466895\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-localization is correlative; no knockout or reconstitution to prove fibrin is a direct substrate\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the upstream transcriptional control of PADI4, showing hormone and basal transcription factor inputs govern its expression.\",\n      \"evidence\": \"Luciferase reporter, ChIP, and siRNA knockdown in MCF-7 cells\",\n      \"pmids\": [\"17456793\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Promoter mapping in one cell line\", \"Does not address PADI4 catalytic function\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected PADI4 to the p53 DNA-damage axis and identified NPM1 as a direct substrate whose citrullination drives subnuclear relocalization, establishing PADI4 as a stress-responsive enzyme with anti-proliferative activity.\",\n      \"evidence\": \"p53 transactivation assay, in vivo citrullination, NPM1 R197K mutant localization, siRNA knockdown, growth assays\",\n      \"pmids\": [\"19843866\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which NPM1 relocalization restrains growth not fully resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated PADI4 acts as a chromatin co-activator at active promoters via physical partnership with Elk-1, expanding its role from substrate modification to transcriptional regulation.\",\n      \"evidence\": \"Genome-wide ChIP-chip, reciprocal Co-IP, EGF-stimulated reporter assays in MCF-7\",\n      \"pmids\": [\"21655091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct citrullination target driving co-activation not pinpointed\", \"Single cell context\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed PADI4 citrullinates histone H4R3 and Lamin C to drive chromatin decondensation and apoptotic nuclear fragmentation, and a knockout phenotype linked it to radiation-induced apoptosis in vivo.\",\n      \"evidence\": \"In vitro/in vivo citrullination, Padi4-knockout mice, ectopic expression, irradiation model\",\n      \"pmids\": [\"22334079\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise contribution of each substrate to nuclear fragmentation unresolved\", \"Tissue scope of apoptotic role limited\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved PADI4's dual transcriptional logic, acting as co-activator (IL6ST) or repressor (CTCF) through Tal1 and antagonism of PRMT6-deposited arginine methylation.\",\n      \"evidence\": \"Reciprocal Co-IP, ChIP for multiple histone marks, expression analysis in hematopoietic cells\",\n      \"pmids\": [\"24874575\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"What dictates activator-versus-repressor outcome at a given locus is unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified DNMT3A as a substrate whose citrullination stabilizes the protein and increases DNA methylation, linking citrullination to the epigenetic methylation machinery.\",\n      \"evidence\": \"Co-IP, in vitro/in vivo citrullination, pulse-chase stability, Padi4-KO MEFs, bisulfite pyrosequencing\",\n      \"pmids\": [\"24957603\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Citrullinated residue(s) on DNMT3A not enumerated\", \"Genome-wide methylation impact not mapped\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Placed PADI4 upstream of NF-\\u03baB/AP-1 in TNF-\\u03b1 signaling, broadening its role to inflammatory signal transduction in vascular cells.\",\n      \"evidence\": \"siRNA knockdown, PADI4 inhibitor, NF-\\u03baB/AP-1 translocation and VCAM-1/adhesion assays\",\n      \"pmids\": [\"25494680\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct citrullination substrate in this pathway not identified\", \"Single lab and cell type\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Detailed PADI4 repression of p21 in synoviocytes via histone arginine mark editing, tying its chromatin activity to apoptosis resistance in disease.\",\n      \"evidence\": \"siRNA/overexpression, ChIP at p21 promoter, flow cytometry apoptosis\",\n      \"pmids\": [\"28367100\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Mechanistic link between H3 modification changes and p21 silencing partly correlative\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Proposed crosstalk between citrullination and ubiquitination through a PADI4-SYVN1 interaction.\",\n      \"evidence\": \"Co-IP and overexpression with ubiquitination assays\",\n      \"pmids\": [\"29039504\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP and overexpression without reconstitution or mutagenesis\", \"SYVN1 not shown to be a citrullination substrate\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established PADI4 as a HIF-recruited co-factor required for histone citrullination at hypoxia response elements and for HIF-driven tumor growth, defining a hypoxia arm of PADI4 function.\",\n      \"evidence\": \"RNA-seq, ChIP at HREs, siRNA knockdown, mouse xenograft tumor models\",\n      \"pmids\": [\"34452909\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HIFs recruit PADI4 mechanistically not defined\", \"Histone target residues at HREs not enumerated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Mapped the structural basis of PADI4 nuclear import, identifying two NLSs that engage the importin \\u03b13 cargo site.\",\n      \"evidence\": \"Fluorescence, CD, ITC, molecular docking\",\n      \"pmids\": [\"35883608\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No cell-based nuclear import functional assay\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Characterized PADI4 quaternary structure and pH/Ca2+ dependence, relating its native dimeric fold to citrullination activity.\",\n      \"evidence\": \"CD, fluorescence, ITC, molecular dynamics simulations\",\n      \"pmids\": [\"35081374\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional mutagenesis not performed\", \"Activity correlation inferred, not directly assayed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended PADI4 substrate range into the proteasome system, citrullinating and stabilizing hRpn13 and modulating proteasome peptidase activity.\",\n      \"evidence\": \"Proteomics, PADI4 inhibitor, proteasome peptidase assay, PROTAC co-depletion in myeloma\",\n      \"pmids\": [\"38151017\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Citrullinated residues on proteasome subunits not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified PKP1 as a direct binding partner of PADI4 by biophysics.\",\n      \"evidence\": \"Fluorescence, CD, ITC, Western blot, molecular simulation\",\n      \"pmids\": [\"36372391\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"In vitro binding only with no cellular functional validation\", \"PKP1 not shown to be a substrate\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked PADI4 to RUNX2 stabilization and osteoblast mineralization through a circRNA/miRNA-controlled, proteasome-inhibiting mechanism.\",\n      \"evidence\": \"RNA-seq, miRNA-sponge luciferase, PADI4-RUNX2 Co-IP, proteasome inhibition, knockdown/overexpression\",\n      \"pmids\": [\"33363159\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RUNX2 stabilization requires citrullination not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Provided in vivo evidence linking PAD2/PAD4 to male reproductive function and hormone signaling.\",\n      \"evidence\": \"Conditional Padi2/Padi4 double-knockout mice, hormone assays, histology, apoptosis quantification\",\n      \"pmids\": [\"36224627\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PADI4-specific contribution confounded by joint deletion with PADI2\", \"Molecular substrate in testis unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed PADI4 is dispensable for normal and regenerative haematopoiesis, delimiting where its function is required.\",\n      \"evidence\": \"Conditional single-gene Padi4 knockout, serial transplantation, steady-state and injury analysis\",\n      \"pmids\": [\"35603697\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not exclude roles under non-hematopoietic stress contexts\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated PADI4 citrullination of fibronectin remodels the tumor microenvironment to favor proliferation and glycolysis, and that antibody targeting suppresses tumor growth.\",\n      \"evidence\": \"In vitro fibronectin citrullination, functional cell assays, mouse xenograft with PET-CT, ELISA\",\n      \"pmids\": [\"35772376\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Citrullinated fibronectin residues not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established PADI4 as a critical, immune-dependent effector of p53 tumor suppression, with a hypomorphic p53 variant selectively failing to induce it.\",\n      \"evidence\": \"NMR/crystal structures of p53 Y107H, colony formation, Y107H knock-in mouse cancer models, gene-signature analysis\",\n      \"pmids\": [\"37140445\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Immune effector mechanism downstream of PADI4 not fully resolved\", \"Direct citrullination substrate mediating tumor suppression unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified a nuclear PADI4-NUPR1 complex by structure-guided binding studies, expanding the PADI4 interactome to intrinsically disordered proteins.\",\n      \"evidence\": \"NMR mapping, mutagenesis, PLA, immunofluorescence, ITC, modelling\",\n      \"pmids\": [\"36858171\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the complex not established\", \"NUPR1 not confirmed as substrate\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Mapped a direct MDM2-PADI4 interaction at the PADI4 active site, hinting MDM2 could be a substrate and integrating PADI4 into the p53/MDM2 axis.\",\n      \"evidence\": \"IF, PLA, NMR chemical shift perturbation, ITC, docking, GSK484 competition\",\n      \"pmids\": [\"37409874\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MDM2 citrullination not directly demonstrated\", \"Functional outcome of interaction unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified RYBP as a low-micromolar PADI4 binder and showed combined PADI4/PARP inhibition alters proliferation.\",\n      \"evidence\": \"ITC, fluorescence, PLA, immunofluorescence, AlphaFold2-multimer modelling, combination drug assay\",\n      \"pmids\": [\"37399862\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"RYBP citrullination not directly demonstrated\", \"Single lab; mechanism of drug synergy unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed PADI4 in a cytokine-driven NET pathway, with IL-33/Akt/mTOR-induced PADI4 driving NET formation and tumor drug resistance.\",\n      \"evidence\": \"siRNA, Western blot, rapamycin and GSK484 experiments, mouse tumor models, NET-marker ELISA\",\n      \"pmids\": [\"39585643\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate driving NET formation not defined here\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended extracellular-trap function to macrophages, showing IL-4-induced PADI4 drives MET formation and shapes macrophage polarization in sepsis injury.\",\n      \"evidence\": \"Padi2/Padi4 double KO, scRNA-seq, siRNA, Nlrp3-KO, in vivo sepsis model\",\n      \"pmids\": [\"39405117\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PADI4-specific contribution confounded by double KO\", \"Direct substrate in MET formation not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed PADI4 citrullinates PRMT2 at R312 to block its ubiquitin-dependent degradation, driving ID1/ID2 transcription, cancer stemness, and chemoresistance.\",\n      \"evidence\": \"IP, Western blot, RT-PCR, spheroid/CSC assays, cisplatin resistance assay, R312 mutagenesis, GSK484\",\n      \"pmids\": [\"40078091\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Generalizability beyond OSCC not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The unifying determinant of PADI4's context-dependent outcomes \\u2014 how substrate selection and activator-versus-repressor behavior are governed across the p53, HIF, and innate-immune programs \\u2014 remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model linking recruitment partners to substrate choice\", \"Direct citrullination substrate mediating immune-dependent tumor suppression unknown\", \"Mechanism of recruitment to specific promoters by different transcription factors unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3, 5, 7, 12, 18, 25]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 5, 7]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 6, 10]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3, 5, 11, 20]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [21, 22]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [4, 5, 6, 10]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [3, 4, 10, 19]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [5, 10]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [23, 24]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"Elk-1\", \"Tal1\", \"DNMT3A\", \"NPM1\", \"importin \\u03b13\", \"MDM2\", \"NUPR1\", \"RUNX2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}