{"gene":"PJA1","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2002,"finding":"PJA1 (Praja1) binds to the C-terminal necdin homology domain of Dlxin-1 (a MAGE/Necdin family protein) via GST pull-down and co-immunoprecipitation, and acts as an E3 ubiquitin ligase to promote ubiquitination and proteasomal degradation of Dlxin-1 through its RING finger domain, thereby down-regulating Dlx5-dependent transcriptional activity. RING finger mutant Praja1 failed to degrade Dlxin-1, confirming RING-dependent E3 activity.","method":"GST pull-down, co-immunoprecipitation, overexpression with proteasome inhibitor, RING finger mutagenesis, in vivo ubiquitination assay, GAL4-dependent transcription assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods including in vivo ubiquitination, mutagenesis, and functional transcription assay in one rigorous study","pmids":["11959851"],"is_preprint":false},{"year":2002,"finding":"PJA1 is a RING-H2 finger E3 ubiquitin ligase that binds the ubiquitin-conjugating enzyme UbcH5B (E2) and exhibits E2-dependent E3 ubiquitin ligase activity in vitro. PJA1 shares 52.3% identity with PJA2 (NEURODAP1) and is abundantly expressed in the brain.","method":"In vitro binding assay, immunoprecipitation, in vitro ubiquitination assay","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitination assay plus direct E2 binding demonstrated in a single study with multiple methods","pmids":["12036302"],"is_preprint":false},{"year":2011,"finding":"PRAJA1 directly ubiquitinates individual PRC2 subunits (EZH2, EED, SUZ12) in a cell-free system, leading to their proteasomal degradation. Expression of PRAJA1, but not an inactive RING finger mutant, enhanced degradation of PRC2 subunits in cells.","method":"Cell-free ubiquitination assay, overexpression with RING finger mutant, proteasome inhibitor rescue","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus RING finger mutagenesis in cells, single lab, multiple orthogonal methods","pmids":["21513699"],"is_preprint":false},{"year":2011,"finding":"Protein microarray profiling identified UbcH5 family E2 enzymes as optimal partners for Praja1 in vitro, and revealed a broad repertoire of putative Praja1 substrates consistent with its roles in bone development and brain function.","method":"Protein microarray ubiquitination assay, E2 panel profiling","journal":"Cell biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — unbiased proteomic profiling with in vitro activity, single lab, no substrate validation beyond array","pmids":["21461837"],"is_preprint":false},{"year":2013,"finding":"Praja1 co-localizes with cytoskeletal components and NRAGE in PC12 cells, and its overexpression promotes proteasome-dependent degradation of NRAGE, thereby suppressing NGF-induced neuronal differentiation and neurite formation.","method":"Overexpression in stably transfected PC12 cells, co-localization imaging, proteasome inhibitor rescue, neurite formation assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — functional phenotype with proteasome rescue and co-localization, single lab","pmids":["23717400"],"is_preprint":false},{"year":2017,"finding":"PJA1 is a MYOD-induced E3 ubiquitin ligase that promotes EZH2 degradation during skeletal myogenesis. p38α kinase phosphorylates EZH2 at threonine 372, which is required for PJA1-mediated ubiquitination and degradation. PJA1 cytoplasmic localization in proliferating myoblasts limits premature EZH2 degradation; nuclear translocation upon differentiation allows EZH2 targeting.","method":"Biochemical ubiquitination assays, genetic epistasis (PJA1 knockdown/overexpression in myoblasts), phosphorylation site mutagenesis (T372), p38α inhibition, subcellular fractionation/localization","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods including mutagenesis, genetic epistasis, localization studies, and biochemical assays, single lab with comprehensive evidence","pmids":["28067271"],"is_preprint":false},{"year":2018,"finding":"PJA1 interacts with the SMC5/6 complex and facilitates its binding to viral and episomal DNAs in the cell nucleus to restrict DNA viruses (HBV, HSV-1) and episomal plasmids, but not RNA viruses or chromosomally integrated genes, in an interferon-independent manner. This restriction requires DNA topoisomerases, as topoisomerase inhibition or knockdown releases PJA1-mediated silencing.","method":"Co-immunoprecipitation, knockdown/overexpression experiments, chromatin binding assay, DNA topoisomerase inhibitor treatment, reporter assays","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic knockdown, epistasis with topoisomerase inhibitors, multiple virus models, single lab with multiple orthogonal approaches","pmids":["30185588"],"is_preprint":false},{"year":2020,"finding":"PJA1 binds to C-terminal fragment (CTF) TDP-43 and the E2-conjugating enzyme UBE2E3 as shown by co-immunoprecipitation. PJA1 suppresses phosphorylation and cytoplasmic aggregate formation of TDP-43 in neuronal cells and in mouse facial motor neurons in vivo, acting downstream of the HSF1 pathway.","method":"Co-immunoprecipitation, adenoviral overexpression in neuronal cells, in vivo mouse motor neuron model, DNA microarray to identify downstream targets","journal":"Neuropathology : official journal of the Japanese Society of Neuropathology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP with E2 and substrate, in vitro and in vivo functional validation, single lab with multiple orthogonal methods","pmids":["32686212"],"is_preprint":false},{"year":2020,"finding":"1-Stearoyl-2-docosahexaenoyl (18:0/22:6)-phosphatidic acid (PA), generated by DGKδ, selectively binds to Praja1 and enhances its E3 ubiquitin ligase activity, which leads to ubiquitination and degradation of the serotonin transporter (SERT) in the brain.","method":"Lipid binding assay, DGKδ knockout mouse brain lipidomics, Praja1 activity assay with PA","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct lipid-protein binding and functional activity assay in KO mouse brain, single lab, two orthogonal approaches","pmids":["32134507"],"is_preprint":false},{"year":2020,"finding":"PJA1 promotes ubiquitination and proteasomal degradation of phosphorylated SMAD3 and impairs the SMAD3/β2SP-dependent tumor-suppressing TGFβ pathway in HCC cells. In SMAD3-haploinsufficient mice, PJA1 overexpression promoted liver stem cell transformation.","method":"Ubiquitination assay in HCC cells, overexpression/knockdown, mouse liver stem cell transformation assay, gene expression analysis","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based ubiquitination assay, in vivo mouse model, single lab, multiple approaches","pmids":["32127355"],"is_preprint":false},{"year":2020,"finding":"HMGA2 interacts with PJA1 by mass spectrometry, and this interaction is enhanced by TGFβ treatment. PJA1 and HMGA2 co-localize in the nucleus of HCC cells upon TGFβ treatment, suggesting PJA1 regulates HMGA2 levels in the context of TGFβ signaling.","method":"Mass spectrometry, co-immunoprecipitation, co-localization imaging","journal":"Genes & cancer","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP and co-localization data, no direct ubiquitination assay for HMGA2 by PJA1, single lab","pmids":["32577156"],"is_preprint":false},{"year":2021,"finding":"PJA1 interacts with polyglutamine (polyQ) proteins ataxin-3 and huntingtin, promotes their ubiquitination and degradation, reduces aggregate formation in neuronal cells, and suppresses polyQ toxicity in yeast and rescues eye degeneration in a transgenic Drosophila SCA3 model.","method":"Co-immunoprecipitation, ubiquitination assay, knockdown in neuronal cells, yeast toxicity assay, Drosophila in vivo rescue experiment","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ubiquitination, yeast, Drosophila in vivo), cross-model replication in one study","pmids":["34161122"],"is_preprint":false},{"year":2021,"finding":"PJA1 promotes K48-linked ubiquitination of PGAM5 at K88, leading to its proteasomal degradation. This suppresses DRP1 phosphorylation at S637, reduces mitochondrial ROS production, and inhibits GSDME-mediated pyroptosis, conferring docetaxel resistance in nasopharyngeal carcinoma cells.","method":"Ubiquitination assay with K88 mutagenesis and K48-linkage specific analysis, knockdown/overexpression, mitochondrial ROS measurement, pyroptosis assay, in vivo xenograft","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — site-specific mutagenesis (K88), linkage-specific ubiquitination, multiple cellular and in vivo readouts, single lab with comprehensive evidence","pmids":["38906860"],"is_preprint":false},{"year":2021,"finding":"PJA1 regulates ubiquitin-mediated degradation of FOXR2 in lung adenocarcinoma cells, and PJA1 overexpression inhibits cell invasion and induces apoptosis through inactivation of the Wnt/β-catenin signaling pathway.","method":"Ubiquitination assay, overexpression, invasion assay, apoptosis assay, Wnt/β-catenin pathway analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — ubiquitination assay for FOXR2 and functional readouts, single lab, limited mechanistic depth","pmids":["33839405"],"is_preprint":false},{"year":2022,"finding":"PJA1 binds to and suppresses aggregation of multiple aggregate-prone neurodegenerative disease proteins (FUS, SOD1, α-synuclein, ataxin-3, huntingtin polyQ) in neuronal cultures, as shown by co-immunoprecipitation. In contrast, other E3 ligases (Parkin, RNF112, RNF220) bind TDP-43 but fail to suppress its aggregation.","method":"Co-immunoprecipitation, adenoviral co-expression in neuronal cells, aggregate formation assay","journal":"Neuropathology : official journal of the Japanese Society of Neuropathology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple substrates tested by Co-IP and functional aggregation suppression, single lab, replication of prior findings","pmids":["35701899"],"is_preprint":false},{"year":2022,"finding":"The deubiquitylase OTUB2 stabilizes PJA1 by removing ubiquitin chains from it (deubiquitylation), as shown by co-immunoprecipitation and cycloheximide chase assay, thereby promoting HCC cell proliferation and migration.","method":"Co-immunoprecipitation, cycloheximide chase assay, overexpression/knockdown rescue experiments","journal":"Cellular and molecular bioengineering","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and CHX chase are standard but indirect, single lab, functional rescue confirms the relationship","pmids":["35611163"],"is_preprint":false},{"year":2022,"finding":"The N-terminal region (aa 1–224) of Praja1 binds 18:0/22:6-phosphatidic acid with Lys141 being critical for this interaction, while the C-terminal catalytic domain (aa 446–615) interacts with DGKδ2. The N-terminal half of the DGKδ2 catalytic domain (aa 309–466) is the primary binding region for Praja1.","method":"Domain deletion mapping, mutagenesis (K141), lipid binding assay, pulldown assay","journal":"Biochimica et biophysica acta. Molecular and cell biology of lipids","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — mutagenesis and domain mapping with in vitro binding assays, single lab, multiple truncation constructs","pmids":["36528254"],"is_preprint":false},{"year":2023,"finding":"Astrocytic GPR30 positively modulates PJA1 expression through the CREB signaling pathway. PJA1 mediates the effects of astrocytic GPR30 on learning and memory by binding to and presumably targeting Serpina3n, a neuroinflammation marker in astrocytes.","method":"Conditional knockout, CREB signaling assay in cultured astrocytes, Co-IP (PJA1-Serpina3n binding), behavioral assays","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — genetic knockout with behavioral phenotype, signaling pathway assay, and binding partner identification, single lab","pmids":["37712419"],"is_preprint":false},{"year":2024,"finding":"Loss of nuclear TDP-43 suppresses PJA1 gene transcription in the monkey brain through species-specific binding of nuclear TDP-43 to the PJA1 promoter, reducing PJA1 levels and accelerating neurotoxicity. Conversely, overexpressing PJA1 diminishes neuronal cell death caused by TDP-43 knockdown in vivo.","method":"TDP-43 knockdown in monkey brain, promoter binding analysis (species-specific), in vivo PJA1 overexpression rescue","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo monkey and mouse models with promoter binding and functional rescue, single lab","pmids":["38194085"],"is_preprint":false},{"year":2025,"finding":"Praja1 ubiquitinates and promotes proteasomal degradation of tau protein in SH-SY5Y neuroblastoma cells in an E3 ligase activity-dependent manner, as shown by in vivo and in vitro ubiquitination assays. Ancestral sequence reconstruction and mutational analysis revealed the Praja1-tau interaction arose after Praja family duplication in placental ancestors. P301L tau mutant is degraded similarly to wild-type tau by Praja1.","method":"In vivo/in vitro ubiquitination assay, RING-finger activity mutant, ancestral sequence reconstruction, mutational analysis, P301L tau disease variant testing","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution plus mutagenesis plus evolutionary analysis, single lab with multiple orthogonal approaches","pmids":["41182881"],"is_preprint":false},{"year":2025,"finding":"PRAJA1 acts as a negative regulator of synaptic plasticity and memory: LTP induction triggers rapid, proteasome-dependent downregulation of PRAJA1 in hippocampal CA1. PRAJA1 knockdown in vivo enhances object recognition and spatial memory. PRAJA1 regulates excitatory/inhibitory balance, and its elevated expression potentiates GABAergic transmission. Spinophilin was identified as a novel substrate of PRAJA1 by co-immunoprecipitation.","method":"In vivo PRAJA1 knockdown, LTP electrophysiology, behavioral memory assays, protein biochemistry, co-immunoprecipitation (spinophilin substrate identification)","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic knockdown with electrophysiology and behavioral readouts plus substrate Co-IP, single lab with multiple orthogonal methods","pmids":["40243483"],"is_preprint":false}],"current_model":"PJA1 (Praja1) is a brain-enriched RING-H2 E3 ubiquitin ligase that partners with E2 enzymes (UbcH5B, UBE2E3) to ubiquitinate and promote proteasomal degradation of a broad range of substrates — including Dlxin-1, PRC2 subunits (EZH2, EED, SUZ12), SMAD3, TDP-43, tau, polyglutamine proteins, PGAM5, FOXR2, NRAGE, SERT, and spinophilin — with substrate recognition modulated by upstream phosphorylation signals (e.g., p38α-mediated T372 phosphorylation of EZH2), lipid activators (18:0/22:6-phosphatidic acid binding to its N-terminal domain), and interacting complexes (SMC5/6 for nuclear DNA virus restriction); its activity is stabilized by the deubiquitylase OTUB2, regulated transcriptionally by TDP-43 and CREB/GPR30 signaling, and its cytoplasmic-to-nuclear localization shift gates substrate access during differentiation."},"narrative":{"mechanistic_narrative":"PJA1 (Praja1) is a brain-enriched RING-H2 finger E3 ubiquitin ligase that catalyzes substrate ubiquitination and proteasomal degradation in partnership with UbcH5/UbcH5B-family and UBE2E3 E2 conjugating enzymes, with RING-finger integrity required for all of its catalytic activity [PMID:12036302, PMID:11959851, PMID:32686212]. Through this activity it controls the abundance of a broad set of substrates governing transcription, differentiation, and protein homeostasis: it degrades the MAGE/Necdin protein Dlxin-1 to restrain Dlx5-dependent transcription [PMID:11959851], targets individual PRC2 subunits EZH2, EED, and SUZ12 [PMID:21513699], and drives EZH2 turnover during skeletal myogenesis in a manner gated by p38α-mediated EZH2 phosphorylation at threonine 372 and by PJA1's own cytoplasmic-to-nuclear translocation upon differentiation [PMID:28067271]. PJA1 functions prominently in the nervous system, where it suppresses aggregation and toxicity of neurodegeneration-associated proteins—including TDP-43, tau, and polyglutamine proteins ataxin-3 and huntingtin—by promoting their ubiquitination and clearance [PMID:32686212, PMID:34161122, PMID:41182881], and acts as a negative regulator of synaptic plasticity and memory by turning over substrates such as spinophilin [PMID:40243483]. In cancer contexts it degrades phospho-SMAD3 to impair tumor-suppressive TGFβ signaling [PMID:32127355] and ubiquitinates PGAM5 at K88 via K48-linked chains to suppress pyroptosis and confer chemoresistance [PMID:38906860]. Its ligase activity is tuned by upstream inputs: 18:0/22:6-phosphatidic acid generated by DGKδ binds the Praja1 N-terminal region (Lys141 critical) to enhance activity and drive serotonin transporter degradation [PMID:32134507, PMID:36528254], while the deubiquitylase OTUB2 stabilizes PJA1 against self-directed turnover [PMID:35611163]. Beyond degradation, PJA1 interacts with the SMC5/6 complex to silence episomal and nuclear DNA-virus genomes in an interferon-independent, topoisomerase-dependent manner [PMID:30185588], and its own expression is transcriptionally controlled by nuclear TDP-43 and by astrocytic GPR30/CREB signaling [PMID:38194085, PMID:37712419].","teleology":[{"year":2002,"claim":"Established PJA1 as a bona fide RING-H2 E3 ubiquitin ligase by demonstrating both E2 binding and RING-dependent substrate degradation, defining its core biochemical identity.","evidence":"In vitro E2 (UbcH5B) binding and ubiquitination assays, plus GST pull-down, in vivo ubiquitination, RING mutagenesis, and transcription assay on the substrate Dlxin-1","pmids":["12036302","11959851"],"confidence":"High","gaps":["Did not define the spectrum of physiological substrates beyond Dlxin-1","Chain linkage type and processivity not characterized"]},{"year":2011,"claim":"Showed PJA1 targets the PRC2 chromatin-repressive machinery and mapped its preferred E2 partners, expanding its role into epigenetic regulation.","evidence":"Cell-free ubiquitination of EZH2/EED/SUZ12 with RING mutant controls; protein microarray E2-panel and substrate profiling identifying UbcH5 family","pmids":["21513699","21461837"],"confidence":"High","gaps":["Microarray substrate hits largely unvalidated","Physiological contexts where PRC2 subunits are degraded not yet defined"]},{"year":2013,"claim":"Linked PJA1 to neuronal differentiation control by showing it degrades NRAGE and suppresses NGF-induced neurite outgrowth.","evidence":"Overexpression in PC12 cells with co-localization imaging, proteasome rescue, and neurite assays","pmids":["23717400"],"confidence":"Medium","gaps":["Endogenous role not tested by loss-of-function","Direct ubiquitination of NRAGE not reconstituted"]},{"year":2017,"claim":"Defined how substrate access is gated, demonstrating that EZH2 degradation during myogenesis requires p38α phosphorylation of EZH2 (T372) and PJA1 nuclear translocation.","evidence":"Ubiquitination assays, T372 phosphosite mutagenesis, p38α inhibition, genetic epistasis in myoblasts, and subcellular fractionation","pmids":["28067271"],"confidence":"High","gaps":["Signal driving PJA1 nuclear translocation not identified","Generality of phospho-gating to other substrates unknown"]},{"year":2018,"claim":"Revealed a non-degradative function in which PJA1 partners with SMC5/6 to restrict episomal DNA-virus genomes, broadening its activity beyond proteasomal turnover.","evidence":"Reciprocal Co-IP, knockdown/overexpression, chromatin binding, and topoisomerase inhibitor epistasis across HBV/HSV-1 models","pmids":["30185588"],"confidence":"High","gaps":["Whether SMC5/6 or other partners are ubiquitinated unclear","Molecular basis of episomal-versus-chromosomal discrimination not resolved"]},{"year":2020,"claim":"Connected PJA1 to neuronal proteostasis and serotonergic and TGFβ signaling, showing it clears CTF TDP-43, degrades phospho-SMAD3, and is lipid-activated to degrade SERT.","evidence":"Co-IP with UBE2E3 and substrates, in vivo motor-neuron and HCC models, lipid binding/activity assays in DGKδ KO brain, and an HMGA2 interaction screen","pmids":["32686212","32127355","32134507","32577156"],"confidence":"Medium","gaps":["HMGA2 not shown to be ubiquitinated by PJA1 (Low-confidence interaction only)","Direct lipid-to-catalysis mechanism not structurally defined"]},{"year":2021,"claim":"Demonstrated broad protective roles against protein aggregation and additional disease substrates, establishing PJA1 as a multi-substrate quality-control ligase.","evidence":"Co-IP, ubiquitination assays, and cross-model rescue (neuronal, yeast, Drosophila) for polyQ proteins; K88/K48-linkage mutagenesis for PGAM5; ubiquitination and pathway readouts for FOXR2","pmids":["34161122","38906860","33839405"],"confidence":"High","gaps":["Whether aggregation suppression requires degradation versus binding not fully separated","FOXR2 mechanism limited in depth"]},{"year":2022,"claim":"Distinguished PJA1's aggregation-suppressing activity from mere substrate binding and identified OTUB2 as a stabilizer that controls PJA1 abundance.","evidence":"Co-IP and aggregate assays comparing PJA1 to other TDP-43-binding E3 ligases; OTUB2 Co-IP and cycloheximide chase with rescue; N/C-terminal domain mapping (K141, DGKδ2)","pmids":["35701899","35611163","36528254"],"confidence":"Medium","gaps":["Mechanism by which PJA1 uniquely suppresses aggregation versus other E3s unresolved","OTUB2-PJA1 deubiquitylation linkage specificity not defined"]},{"year":2023,"claim":"Placed PJA1 downstream of astrocytic GPR30/CREB signaling in learning and memory and identified Serpina3n as a binding partner.","evidence":"Conditional knockout, CREB signaling assays in astrocytes, PJA1-Serpina3n Co-IP, and behavioral testing","pmids":["37712419"],"confidence":"Medium","gaps":["Serpina3n ubiquitination/degradation by PJA1 not demonstrated","Cell-type specificity of PJA1 memory effects not fully dissected"]},{"year":2024,"claim":"Showed PJA1 expression is transcriptionally driven by nuclear TDP-43, creating a feedback loop relevant to TDP-43 proteinopathy neurotoxicity.","evidence":"TDP-43 knockdown with species-specific promoter binding analysis and in vivo PJA1 overexpression rescue in monkey/mouse brain","pmids":["38194085"],"confidence":"Medium","gaps":["Species-specificity of the regulatory loop limits human extrapolation","Direct promoter occupancy mechanism not structurally defined"]},{"year":2025,"claim":"Established PJA1 as a negative regulator of synaptic plasticity and memory and confirmed tau as a degradation substrate with an evolutionarily recent origin.","evidence":"In vivo knockdown, LTP electrophysiology, behavior, and spinophilin Co-IP; tau ubiquitination assays with RING mutant and ancestral sequence reconstruction","pmids":["40243483","41182881"],"confidence":"High","gaps":["Spinophilin ubiquitination not yet reconstituted","How LTP triggers proteasomal PJA1 downregulation unknown"]},{"year":null,"claim":"How PJA1 selects among its very broad substrate set in a given cell and how its localization, lipid activation, and partner complexes are coordinated in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of PJA1 substrate engagement","Endogenous substrate hierarchy and tissue-specific specificity undefined","Integration of degradative versus SMC5/6 non-degradative functions unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,2,12,19]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,12,19]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[8,16]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5,6,10]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,2,12,19]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[9,13,17]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[9,12,13,19]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[6]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[2,5]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[7,11,20]}],"complexes":["SMC5/6 complex"],"partners":["UBCH5B","UBE2E3","EZH2","SMAD3","TDP-43","PGAM5","OTUB2","DGKΔ"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NG27","full_name":"E3 ubiquitin-protein ligase Praja-1","aliases":["RING finger protein 70","RING-type E3 ubiquitin transferase Praja-1"],"length_aa":643,"mass_kda":71.0,"function":"Has E2-dependent E3 ubiquitin-protein ligase activity. Ubiquitinates MAGED1 antigen leading to its subsequent degradation by proteasome (By similarity). May be involved in protein sorting","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8NG27/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PJA1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PJA1","total_profiled":1310},"omim":[{"mim_id":"304110","title":"CRANIOFRONTONASAL SYNDROME; CFNS","url":"https://www.omim.org/entry/304110"},{"mim_id":"300420","title":"PRAJA RING FINGER UBIQUITIN LIGASE 1; PJA1","url":"https://www.omim.org/entry/300420"},{"mim_id":"300035","title":"EPHRIN B1; EFNB1","url":"https://www.omim.org/entry/300035"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nucleoli","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"epididymis","ntpm":151.0}],"url":"https://www.proteinatlas.org/search/PJA1"},"hgnc":{"alias_symbol":["FLJ11830","RNF70","PRAJA1"],"prev_symbol":[]},"alphafold":{"accession":"Q8NG27","domains":[{"cath_id":"3.30.40.10","chopping":"568-643","consensus_level":"medium","plddt":83.8074,"start":568,"end":643},{"cath_id":"1.20.5","chopping":"532-565","consensus_level":"medium","plddt":82.5459,"start":532,"end":565}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NG27","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NG27-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NG27-F1-predicted_aligned_error_v6.png","plddt_mean":50.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PJA1","jax_strain_url":"https://www.jax.org/strain/search?query=PJA1"},"sequence":{"accession":"Q8NG27","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NG27.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NG27/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NG27"}},"corpus_meta":[{"pmid":"11959851","id":"PMC_11959851","title":"A RING finger protein Praja1 regulates Dlx5-dependent transcription through its ubiquitin ligase activity for the Dlx/Msx-interacting MAGE/Necdin family protein, Dlxin-1.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11959851","citation_count":93,"is_preprint":false},{"pmid":"12036302","id":"PMC_12036302","title":"PJA1, encoding a RING-H2 finger ubiquitin ligase, is a novel human X chromosome gene abundantly expressed in brain.","date":"2002","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/12036302","citation_count":51,"is_preprint":false},{"pmid":"28067271","id":"PMC_28067271","title":"Praja1 E3 ubiquitin ligase promotes skeletal myogenesis through degradation of EZH2 upon p38α activation.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28067271","citation_count":46,"is_preprint":false},{"pmid":"21513699","id":"PMC_21513699","title":"PRAJA1 is a ubiquitin ligase for the polycomb repressive complex 2 proteins.","date":"2011","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/21513699","citation_count":45,"is_preprint":false},{"pmid":"9393880","id":"PMC_9393880","title":"Praja1, a novel gene encoding a RING-H2 motif in mouse development.","date":"1997","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/9393880","citation_count":44,"is_preprint":false},{"pmid":"17941886","id":"PMC_17941886","title":"Contiguous gene deletions involving EFNB1, OPHN1, PJA1 and EDA in patients with craniofrontonasal syndrome.","date":"2007","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17941886","citation_count":36,"is_preprint":false},{"pmid":"30185588","id":"PMC_30185588","title":"PJA1 Coordinates with the SMC5/6 Complex To Restrict DNA Viruses and Episomal Genes in an Interferon-Independent Manner.","date":"2018","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/30185588","citation_count":32,"is_preprint":false},{"pmid":"32686212","id":"PMC_32686212","title":"Praja1 RING-finger E3 ubiquitin ligase suppresses neuronal cytoplasmic TDP-43 aggregate formation.","date":"2020","source":"Neuropathology : official journal of the Japanese Society of Neuropathology","url":"https://pubmed.ncbi.nlm.nih.gov/32686212","citation_count":30,"is_preprint":false},{"pmid":"32134507","id":"PMC_32134507","title":"1-Stearoyl-2-docosahexaenoyl-phosphatidic acid interacts with and activates Praja-1, the E3 ubiquitin ligase acting on the serotonin transporter in the brain.","date":"2020","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/32134507","citation_count":26,"is_preprint":false},{"pmid":"32530565","id":"PMC_32530565","title":"A recurrent PJA1 variant in trigonocephaly and neurodevelopmental disorders.","date":"2020","source":"Annals of clinical and translational neurology","url":"https://pubmed.ncbi.nlm.nih.gov/32530565","citation_count":23,"is_preprint":false},{"pmid":"38906860","id":"PMC_38906860","title":"PJA1-mediated suppression of pyroptosis as a driver of docetaxel resistance in nasopharyngeal carcinoma.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38906860","citation_count":22,"is_preprint":false},{"pmid":"32127355","id":"PMC_32127355","title":"Targeting the E3 Ubiquitin Ligase PJA1 Enhances Tumor-Suppressing TGFβ Signaling.","date":"2020","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/32127355","citation_count":22,"is_preprint":false},{"pmid":"34161122","id":"PMC_34161122","title":"Praja1 ubiquitin ligase facilitates degradation of polyglutamine proteins and suppresses polyglutamine-mediated toxicity.","date":"2021","source":"Molecular biology of the 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Neuropathology","url":"https://pubmed.ncbi.nlm.nih.gov/35701899","citation_count":13,"is_preprint":false},{"pmid":"33457451","id":"PMC_33457451","title":"Dysregulated PJA1-TGF-β signaling in cancer stem cell-associated liver cancers.","date":"2020","source":"Oncoscience","url":"https://pubmed.ncbi.nlm.nih.gov/33457451","citation_count":13,"is_preprint":false},{"pmid":"32577156","id":"PMC_32577156","title":"Alterations in TGF-β signaling leads to high HMGA2 levels potentially through modulation of PJA1/SMAD3 in HCC cells.","date":"2020","source":"Genes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/32577156","citation_count":12,"is_preprint":false},{"pmid":"33839405","id":"PMC_33839405","title":"E3 ubiquitin ligase PJA1 regulates lung adenocarcinoma apoptosis and invasion through promoting FOXR2 degradation.","date":"2021","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/33839405","citation_count":11,"is_preprint":false},{"pmid":"21461837","id":"PMC_21461837","title":"Protein microarrays for the identification of praja1 e3 ubiquitin ligase substrates.","date":"2011","source":"Cell biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/21461837","citation_count":10,"is_preprint":false},{"pmid":"35611163","id":"PMC_35611163","title":"OTUB2 Promotes Proliferation and Migration of Hepatocellular Carcinoma Cells by PJA1 Deubiquitylation.","date":"2022","source":"Cellular and molecular bioengineering","url":"https://pubmed.ncbi.nlm.nih.gov/35611163","citation_count":9,"is_preprint":false},{"pmid":"36528254","id":"PMC_36528254","title":"Distinct regions of Praja-1 E3 ubiquitin-protein ligase selectively bind to docosahexaenoic acid-containing phosphatidic acid and diacylglycerol kinase δ.","date":"2022","source":"Biochimica et biophysica acta. Molecular and cell biology of lipids","url":"https://pubmed.ncbi.nlm.nih.gov/36528254","citation_count":5,"is_preprint":false},{"pmid":"40243483","id":"PMC_40243483","title":"The E3 Ubiquitin Ligase PRAJA1: A Key Regulator of Synaptic Dynamics and Memory Processes with Implications for Alzheimer's Disease.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40243483","citation_count":4,"is_preprint":false},{"pmid":"41182881","id":"PMC_41182881","title":"E3 ligase Praja1 mediates ubiquitination and degradation of microtubule-associated protein tau.","date":"2025","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/41182881","citation_count":3,"is_preprint":false},{"pmid":"38194085","id":"PMC_38194085","title":"Loss of TDP-43 mediates severe neurotoxicity by suppressing PJA1 gene transcription in the monkey brain.","date":"2024","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/38194085","citation_count":2,"is_preprint":false},{"pmid":"41466523","id":"PMC_41466523","title":"Praja1 E3 ubiquitin ligase and the role it plays in neurodegeneration.","date":"2025","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/41466523","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15407,"output_tokens":5362,"usd":0.063326,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13782,"output_tokens":4458,"usd":0.09018,"stage2_stop_reason":"end_turn"},"total_usd":0.153506,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"PJA1 (Praja1) binds to the C-terminal necdin homology domain of Dlxin-1 (a MAGE/Necdin family protein) via GST pull-down and co-immunoprecipitation, and acts as an E3 ubiquitin ligase to promote ubiquitination and proteasomal degradation of Dlxin-1 through its RING finger domain, thereby down-regulating Dlx5-dependent transcriptional activity. RING finger mutant Praja1 failed to degrade Dlxin-1, confirming RING-dependent E3 activity.\",\n      \"method\": \"GST pull-down, co-immunoprecipitation, overexpression with proteasome inhibitor, RING finger mutagenesis, in vivo ubiquitination assay, GAL4-dependent transcription assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods including in vivo ubiquitination, mutagenesis, and functional transcription assay in one rigorous study\",\n      \"pmids\": [\"11959851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PJA1 is a RING-H2 finger E3 ubiquitin ligase that binds the ubiquitin-conjugating enzyme UbcH5B (E2) and exhibits E2-dependent E3 ubiquitin ligase activity in vitro. PJA1 shares 52.3% identity with PJA2 (NEURODAP1) and is abundantly expressed in the brain.\",\n      \"method\": \"In vitro binding assay, immunoprecipitation, in vitro ubiquitination assay\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitination assay plus direct E2 binding demonstrated in a single study with multiple methods\",\n      \"pmids\": [\"12036302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PRAJA1 directly ubiquitinates individual PRC2 subunits (EZH2, EED, SUZ12) in a cell-free system, leading to their proteasomal degradation. Expression of PRAJA1, but not an inactive RING finger mutant, enhanced degradation of PRC2 subunits in cells.\",\n      \"method\": \"Cell-free ubiquitination assay, overexpression with RING finger mutant, proteasome inhibitor rescue\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus RING finger mutagenesis in cells, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"21513699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Protein microarray profiling identified UbcH5 family E2 enzymes as optimal partners for Praja1 in vitro, and revealed a broad repertoire of putative Praja1 substrates consistent with its roles in bone development and brain function.\",\n      \"method\": \"Protein microarray ubiquitination assay, E2 panel profiling\",\n      \"journal\": \"Cell biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — unbiased proteomic profiling with in vitro activity, single lab, no substrate validation beyond array\",\n      \"pmids\": [\"21461837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Praja1 co-localizes with cytoskeletal components and NRAGE in PC12 cells, and its overexpression promotes proteasome-dependent degradation of NRAGE, thereby suppressing NGF-induced neuronal differentiation and neurite formation.\",\n      \"method\": \"Overexpression in stably transfected PC12 cells, co-localization imaging, proteasome inhibitor rescue, neurite formation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — functional phenotype with proteasome rescue and co-localization, single lab\",\n      \"pmids\": [\"23717400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PJA1 is a MYOD-induced E3 ubiquitin ligase that promotes EZH2 degradation during skeletal myogenesis. p38α kinase phosphorylates EZH2 at threonine 372, which is required for PJA1-mediated ubiquitination and degradation. PJA1 cytoplasmic localization in proliferating myoblasts limits premature EZH2 degradation; nuclear translocation upon differentiation allows EZH2 targeting.\",\n      \"method\": \"Biochemical ubiquitination assays, genetic epistasis (PJA1 knockdown/overexpression in myoblasts), phosphorylation site mutagenesis (T372), p38α inhibition, subcellular fractionation/localization\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods including mutagenesis, genetic epistasis, localization studies, and biochemical assays, single lab with comprehensive evidence\",\n      \"pmids\": [\"28067271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PJA1 interacts with the SMC5/6 complex and facilitates its binding to viral and episomal DNAs in the cell nucleus to restrict DNA viruses (HBV, HSV-1) and episomal plasmids, but not RNA viruses or chromosomally integrated genes, in an interferon-independent manner. This restriction requires DNA topoisomerases, as topoisomerase inhibition or knockdown releases PJA1-mediated silencing.\",\n      \"method\": \"Co-immunoprecipitation, knockdown/overexpression experiments, chromatin binding assay, DNA topoisomerase inhibitor treatment, reporter assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic knockdown, epistasis with topoisomerase inhibitors, multiple virus models, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"30185588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PJA1 binds to C-terminal fragment (CTF) TDP-43 and the E2-conjugating enzyme UBE2E3 as shown by co-immunoprecipitation. PJA1 suppresses phosphorylation and cytoplasmic aggregate formation of TDP-43 in neuronal cells and in mouse facial motor neurons in vivo, acting downstream of the HSF1 pathway.\",\n      \"method\": \"Co-immunoprecipitation, adenoviral overexpression in neuronal cells, in vivo mouse motor neuron model, DNA microarray to identify downstream targets\",\n      \"journal\": \"Neuropathology : official journal of the Japanese Society of Neuropathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with E2 and substrate, in vitro and in vivo functional validation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"32686212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"1-Stearoyl-2-docosahexaenoyl (18:0/22:6)-phosphatidic acid (PA), generated by DGKδ, selectively binds to Praja1 and enhances its E3 ubiquitin ligase activity, which leads to ubiquitination and degradation of the serotonin transporter (SERT) in the brain.\",\n      \"method\": \"Lipid binding assay, DGKδ knockout mouse brain lipidomics, Praja1 activity assay with PA\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct lipid-protein binding and functional activity assay in KO mouse brain, single lab, two orthogonal approaches\",\n      \"pmids\": [\"32134507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PJA1 promotes ubiquitination and proteasomal degradation of phosphorylated SMAD3 and impairs the SMAD3/β2SP-dependent tumor-suppressing TGFβ pathway in HCC cells. In SMAD3-haploinsufficient mice, PJA1 overexpression promoted liver stem cell transformation.\",\n      \"method\": \"Ubiquitination assay in HCC cells, overexpression/knockdown, mouse liver stem cell transformation assay, gene expression analysis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based ubiquitination assay, in vivo mouse model, single lab, multiple approaches\",\n      \"pmids\": [\"32127355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HMGA2 interacts with PJA1 by mass spectrometry, and this interaction is enhanced by TGFβ treatment. PJA1 and HMGA2 co-localize in the nucleus of HCC cells upon TGFβ treatment, suggesting PJA1 regulates HMGA2 levels in the context of TGFβ signaling.\",\n      \"method\": \"Mass spectrometry, co-immunoprecipitation, co-localization imaging\",\n      \"journal\": \"Genes & cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP and co-localization data, no direct ubiquitination assay for HMGA2 by PJA1, single lab\",\n      \"pmids\": [\"32577156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PJA1 interacts with polyglutamine (polyQ) proteins ataxin-3 and huntingtin, promotes their ubiquitination and degradation, reduces aggregate formation in neuronal cells, and suppresses polyQ toxicity in yeast and rescues eye degeneration in a transgenic Drosophila SCA3 model.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, knockdown in neuronal cells, yeast toxicity assay, Drosophila in vivo rescue experiment\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ubiquitination, yeast, Drosophila in vivo), cross-model replication in one study\",\n      \"pmids\": [\"34161122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PJA1 promotes K48-linked ubiquitination of PGAM5 at K88, leading to its proteasomal degradation. This suppresses DRP1 phosphorylation at S637, reduces mitochondrial ROS production, and inhibits GSDME-mediated pyroptosis, conferring docetaxel resistance in nasopharyngeal carcinoma cells.\",\n      \"method\": \"Ubiquitination assay with K88 mutagenesis and K48-linkage specific analysis, knockdown/overexpression, mitochondrial ROS measurement, pyroptosis assay, in vivo xenograft\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — site-specific mutagenesis (K88), linkage-specific ubiquitination, multiple cellular and in vivo readouts, single lab with comprehensive evidence\",\n      \"pmids\": [\"38906860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PJA1 regulates ubiquitin-mediated degradation of FOXR2 in lung adenocarcinoma cells, and PJA1 overexpression inhibits cell invasion and induces apoptosis through inactivation of the Wnt/β-catenin signaling pathway.\",\n      \"method\": \"Ubiquitination assay, overexpression, invasion assay, apoptosis assay, Wnt/β-catenin pathway analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — ubiquitination assay for FOXR2 and functional readouts, single lab, limited mechanistic depth\",\n      \"pmids\": [\"33839405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PJA1 binds to and suppresses aggregation of multiple aggregate-prone neurodegenerative disease proteins (FUS, SOD1, α-synuclein, ataxin-3, huntingtin polyQ) in neuronal cultures, as shown by co-immunoprecipitation. In contrast, other E3 ligases (Parkin, RNF112, RNF220) bind TDP-43 but fail to suppress its aggregation.\",\n      \"method\": \"Co-immunoprecipitation, adenoviral co-expression in neuronal cells, aggregate formation assay\",\n      \"journal\": \"Neuropathology : official journal of the Japanese Society of Neuropathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple substrates tested by Co-IP and functional aggregation suppression, single lab, replication of prior findings\",\n      \"pmids\": [\"35701899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The deubiquitylase OTUB2 stabilizes PJA1 by removing ubiquitin chains from it (deubiquitylation), as shown by co-immunoprecipitation and cycloheximide chase assay, thereby promoting HCC cell proliferation and migration.\",\n      \"method\": \"Co-immunoprecipitation, cycloheximide chase assay, overexpression/knockdown rescue experiments\",\n      \"journal\": \"Cellular and molecular bioengineering\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and CHX chase are standard but indirect, single lab, functional rescue confirms the relationship\",\n      \"pmids\": [\"35611163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The N-terminal region (aa 1–224) of Praja1 binds 18:0/22:6-phosphatidic acid with Lys141 being critical for this interaction, while the C-terminal catalytic domain (aa 446–615) interacts with DGKδ2. The N-terminal half of the DGKδ2 catalytic domain (aa 309–466) is the primary binding region for Praja1.\",\n      \"method\": \"Domain deletion mapping, mutagenesis (K141), lipid binding assay, pulldown assay\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular and cell biology of lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutagenesis and domain mapping with in vitro binding assays, single lab, multiple truncation constructs\",\n      \"pmids\": [\"36528254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Astrocytic GPR30 positively modulates PJA1 expression through the CREB signaling pathway. PJA1 mediates the effects of astrocytic GPR30 on learning and memory by binding to and presumably targeting Serpina3n, a neuroinflammation marker in astrocytes.\",\n      \"method\": \"Conditional knockout, CREB signaling assay in cultured astrocytes, Co-IP (PJA1-Serpina3n binding), behavioral assays\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — genetic knockout with behavioral phenotype, signaling pathway assay, and binding partner identification, single lab\",\n      \"pmids\": [\"37712419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of nuclear TDP-43 suppresses PJA1 gene transcription in the monkey brain through species-specific binding of nuclear TDP-43 to the PJA1 promoter, reducing PJA1 levels and accelerating neurotoxicity. Conversely, overexpressing PJA1 diminishes neuronal cell death caused by TDP-43 knockdown in vivo.\",\n      \"method\": \"TDP-43 knockdown in monkey brain, promoter binding analysis (species-specific), in vivo PJA1 overexpression rescue\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo monkey and mouse models with promoter binding and functional rescue, single lab\",\n      \"pmids\": [\"38194085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Praja1 ubiquitinates and promotes proteasomal degradation of tau protein in SH-SY5Y neuroblastoma cells in an E3 ligase activity-dependent manner, as shown by in vivo and in vitro ubiquitination assays. Ancestral sequence reconstruction and mutational analysis revealed the Praja1-tau interaction arose after Praja family duplication in placental ancestors. P301L tau mutant is degraded similarly to wild-type tau by Praja1.\",\n      \"method\": \"In vivo/in vitro ubiquitination assay, RING-finger activity mutant, ancestral sequence reconstruction, mutational analysis, P301L tau disease variant testing\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution plus mutagenesis plus evolutionary analysis, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"41182881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRAJA1 acts as a negative regulator of synaptic plasticity and memory: LTP induction triggers rapid, proteasome-dependent downregulation of PRAJA1 in hippocampal CA1. PRAJA1 knockdown in vivo enhances object recognition and spatial memory. PRAJA1 regulates excitatory/inhibitory balance, and its elevated expression potentiates GABAergic transmission. Spinophilin was identified as a novel substrate of PRAJA1 by co-immunoprecipitation.\",\n      \"method\": \"In vivo PRAJA1 knockdown, LTP electrophysiology, behavioral memory assays, protein biochemistry, co-immunoprecipitation (spinophilin substrate identification)\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic knockdown with electrophysiology and behavioral readouts plus substrate Co-IP, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"40243483\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PJA1 (Praja1) is a brain-enriched RING-H2 E3 ubiquitin ligase that partners with E2 enzymes (UbcH5B, UBE2E3) to ubiquitinate and promote proteasomal degradation of a broad range of substrates — including Dlxin-1, PRC2 subunits (EZH2, EED, SUZ12), SMAD3, TDP-43, tau, polyglutamine proteins, PGAM5, FOXR2, NRAGE, SERT, and spinophilin — with substrate recognition modulated by upstream phosphorylation signals (e.g., p38α-mediated T372 phosphorylation of EZH2), lipid activators (18:0/22:6-phosphatidic acid binding to its N-terminal domain), and interacting complexes (SMC5/6 for nuclear DNA virus restriction); its activity is stabilized by the deubiquitylase OTUB2, regulated transcriptionally by TDP-43 and CREB/GPR30 signaling, and its cytoplasmic-to-nuclear localization shift gates substrate access during differentiation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PJA1 (Praja1) is a brain-enriched RING-H2 finger E3 ubiquitin ligase that catalyzes substrate ubiquitination and proteasomal degradation in partnership with UbcH5/UbcH5B-family and UBE2E3 E2 conjugating enzymes, with RING-finger integrity required for all of its catalytic activity [#1, #0, #7]. Through this activity it controls the abundance of a broad set of substrates governing transcription, differentiation, and protein homeostasis: it degrades the MAGE/Necdin protein Dlxin-1 to restrain Dlx5-dependent transcription [#0], targets individual PRC2 subunits EZH2, EED, and SUZ12 [#2], and drives EZH2 turnover during skeletal myogenesis in a manner gated by p38\\u03b1-mediated EZH2 phosphorylation at threonine 372 and by PJA1's own cytoplasmic-to-nuclear translocation upon differentiation [#5]. PJA1 functions prominently in the nervous system, where it suppresses aggregation and toxicity of neurodegeneration-associated proteins\\u2014including TDP-43, tau, and polyglutamine proteins ataxin-3 and huntingtin\\u2014by promoting their ubiquitination and clearance [#7, #11, #19], and acts as a negative regulator of synaptic plasticity and memory by turning over substrates such as spinophilin [#20]. In cancer contexts it degrades phospho-SMAD3 to impair tumor-suppressive TGF\\u03b2 signaling [#9] and ubiquitinates PGAM5 at K88 via K48-linked chains to suppress pyroptosis and confer chemoresistance [#12]. Its ligase activity is tuned by upstream inputs: 18:0/22:6-phosphatidic acid generated by DGK\\u03b4 binds the Praja1 N-terminal region (Lys141 critical) to enhance activity and drive serotonin transporter degradation [#8, #16], while the deubiquitylase OTUB2 stabilizes PJA1 against self-directed turnover [#15]. Beyond degradation, PJA1 interacts with the SMC5/6 complex to silence episomal and nuclear DNA-virus genomes in an interferon-independent, topoisomerase-dependent manner [#6], and its own expression is transcriptionally controlled by nuclear TDP-43 and by astrocytic GPR30/CREB signaling [#18, #17].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established PJA1 as a bona fide RING-H2 E3 ubiquitin ligase by demonstrating both E2 binding and RING-dependent substrate degradation, defining its core biochemical identity.\",\n      \"evidence\": \"In vitro E2 (UbcH5B) binding and ubiquitination assays, plus GST pull-down, in vivo ubiquitination, RING mutagenesis, and transcription assay on the substrate Dlxin-1\",\n      \"pmids\": [\"12036302\", \"11959851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the spectrum of physiological substrates beyond Dlxin-1\", \"Chain linkage type and processivity not characterized\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed PJA1 targets the PRC2 chromatin-repressive machinery and mapped its preferred E2 partners, expanding its role into epigenetic regulation.\",\n      \"evidence\": \"Cell-free ubiquitination of EZH2/EED/SUZ12 with RING mutant controls; protein microarray E2-panel and substrate profiling identifying UbcH5 family\",\n      \"pmids\": [\"21513699\", \"21461837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Microarray substrate hits largely unvalidated\", \"Physiological contexts where PRC2 subunits are degraded not yet defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked PJA1 to neuronal differentiation control by showing it degrades NRAGE and suppresses NGF-induced neurite outgrowth.\",\n      \"evidence\": \"Overexpression in PC12 cells with co-localization imaging, proteasome rescue, and neurite assays\",\n      \"pmids\": [\"23717400\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous role not tested by loss-of-function\", \"Direct ubiquitination of NRAGE not reconstituted\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined how substrate access is gated, demonstrating that EZH2 degradation during myogenesis requires p38\\u03b1 phosphorylation of EZH2 (T372) and PJA1 nuclear translocation.\",\n      \"evidence\": \"Ubiquitination assays, T372 phosphosite mutagenesis, p38\\u03b1 inhibition, genetic epistasis in myoblasts, and subcellular fractionation\",\n      \"pmids\": [\"28067271\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signal driving PJA1 nuclear translocation not identified\", \"Generality of phospho-gating to other substrates unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed a non-degradative function in which PJA1 partners with SMC5/6 to restrict episomal DNA-virus genomes, broadening its activity beyond proteasomal turnover.\",\n      \"evidence\": \"Reciprocal Co-IP, knockdown/overexpression, chromatin binding, and topoisomerase inhibitor epistasis across HBV/HSV-1 models\",\n      \"pmids\": [\"30185588\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SMC5/6 or other partners are ubiquitinated unclear\", \"Molecular basis of episomal-versus-chromosomal discrimination not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Connected PJA1 to neuronal proteostasis and serotonergic and TGF\\u03b2 signaling, showing it clears CTF TDP-43, degrades phospho-SMAD3, and is lipid-activated to degrade SERT.\",\n      \"evidence\": \"Co-IP with UBE2E3 and substrates, in vivo motor-neuron and HCC models, lipid binding/activity assays in DGK\\u03b4 KO brain, and an HMGA2 interaction screen\",\n      \"pmids\": [\"32686212\", \"32127355\", \"32134507\", \"32577156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"HMGA2 not shown to be ubiquitinated by PJA1 (Low-confidence interaction only)\", \"Direct lipid-to-catalysis mechanism not structurally defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated broad protective roles against protein aggregation and additional disease substrates, establishing PJA1 as a multi-substrate quality-control ligase.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, and cross-model rescue (neuronal, yeast, Drosophila) for polyQ proteins; K88/K48-linkage mutagenesis for PGAM5; ubiquitination and pathway readouts for FOXR2\",\n      \"pmids\": [\"34161122\", \"38906860\", \"33839405\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether aggregation suppression requires degradation versus binding not fully separated\", \"FOXR2 mechanism limited in depth\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Distinguished PJA1's aggregation-suppressing activity from mere substrate binding and identified OTUB2 as a stabilizer that controls PJA1 abundance.\",\n      \"evidence\": \"Co-IP and aggregate assays comparing PJA1 to other TDP-43-binding E3 ligases; OTUB2 Co-IP and cycloheximide chase with rescue; N/C-terminal domain mapping (K141, DGK\\u03b42)\",\n      \"pmids\": [\"35701899\", \"35611163\", \"36528254\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which PJA1 uniquely suppresses aggregation versus other E3s unresolved\", \"OTUB2-PJA1 deubiquitylation linkage specificity not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed PJA1 downstream of astrocytic GPR30/CREB signaling in learning and memory and identified Serpina3n as a binding partner.\",\n      \"evidence\": \"Conditional knockout, CREB signaling assays in astrocytes, PJA1-Serpina3n Co-IP, and behavioral testing\",\n      \"pmids\": [\"37712419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Serpina3n ubiquitination/degradation by PJA1 not demonstrated\", \"Cell-type specificity of PJA1 memory effects not fully dissected\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed PJA1 expression is transcriptionally driven by nuclear TDP-43, creating a feedback loop relevant to TDP-43 proteinopathy neurotoxicity.\",\n      \"evidence\": \"TDP-43 knockdown with species-specific promoter binding analysis and in vivo PJA1 overexpression rescue in monkey/mouse brain\",\n      \"pmids\": [\"38194085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Species-specificity of the regulatory loop limits human extrapolation\", \"Direct promoter occupancy mechanism not structurally defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established PJA1 as a negative regulator of synaptic plasticity and memory and confirmed tau as a degradation substrate with an evolutionarily recent origin.\",\n      \"evidence\": \"In vivo knockdown, LTP electrophysiology, behavior, and spinophilin Co-IP; tau ubiquitination assays with RING mutant and ancestral sequence reconstruction\",\n      \"pmids\": [\"40243483\", \"41182881\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spinophilin ubiquitination not yet reconstituted\", \"How LTP triggers proteasomal PJA1 downregulation unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PJA1 selects among its very broad substrate set in a given cell and how its localization, lipid activation, and partner complexes are coordinated in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of PJA1 substrate engagement\", \"Endogenous substrate hierarchy and tissue-specific specificity undefined\", \"Integration of degradative versus SMC5/6 non-degradative functions unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0061630\", \"supporting_discovery_ids\": [0, 1, 2, 5, 12, 19]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2, 12, 19]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 12, 19]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [8, 16]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 6, 10]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 2, 12, 19]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 13, 17]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [9, 12, 13, 19]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [7, 11, 20]}\n    ],\n    \"complexes\": [\"SMC5/6 complex\"],\n    \"partners\": [\"UbcH5B\", \"UBE2E3\", \"EZH2\", \"SMAD3\", \"TDP-43\", \"PGAM5\", \"OTUB2\", \"DGK\\u03b4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}