{"gene":"PURA","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":1995,"finding":"Pur-alpha binds the hypophosphorylated form of Rb (retinoblastoma protein) with high affinity via a domain with limited homology to the SV40 large T-antigen Rb-binding region; the single-stranded DNA Pur-alpha recognition element disrupts the Pur-alpha–Rb complex, and conversely high concentrations of Rb prevent Pur-alpha from binding DNA.","method":"GST pull-down with purified proteins, co-immunoprecipitation from cell lysates, deletion mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with GST-fusion proteins, co-IP from cell extracts, and deletion mutagenesis all in one study; reciprocal inhibition experiments provided functional validation","pmids":["7592647"],"is_preprint":false},{"year":1996,"finding":"HIV-1 Tat protein interacts with Pur-alpha through two leucine-rich repeats in Pur-alpha; Tat enhances Pur-alpha binding to the JCV upTAR element and together they synergistically activate transcription from an upTAR-containing promoter in a cell-cycle-dependent manner.","method":"Co-immunoprecipitation from cell extracts, GST-Pur-alpha binding assay, transcription reporter (cotransfection)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro binding with purified GST-Pur-alpha, co-IP from cells, functional reporter assay; multiple orthogonal methods in one study","pmids":["8943069"],"is_preprint":false},{"year":1996,"finding":"Overexpression of Pur-alpha suppresses replication of JCV DNA in glial cells; Pur-alpha and JCV T-antigen share a common binding region in the single-stranded JCV ori sequence, and T-antigen stimulates Pur-alpha association with the ori; co-immunoprecipitation revealed a molecular association between Pur-alpha and JCV T-antigen in cells.","method":"JCV DNA replication assay in transfected cells, DNA footprinting, band-shift assay, co-immunoprecipitation/Western blot","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — functional replication assay plus footprinting, band-shift, and co-IP; multiple orthogonal methods establishing both physical interaction and functional consequence","pmids":["8648759"],"is_preprint":false},{"year":1998,"finding":"Pur-alpha binds HIV-1 TAR RNA in a sequence-specific manner; amino acids 55–85 (first basic aromatic repeat) are important for TAR RNA binding; overexpression of Pur-alpha increases transcription of the HIV-1 LTR through a TAR-dependent mechanism.","method":"Competition gel-shift analysis with purified proteins, deletion-mutant mapping, reporter gene assay in glial cells","journal":"Gene","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro binding with purified proteins, domain mapping by deletion mutants, and functional reporter assay; multiple orthogonal methods","pmids":["9524214"],"is_preprint":false},{"year":1998,"finding":"Pur-alpha physically and functionally interacts with JCV large T-antigen; the interaction attenuates T-antigen-mediated transcriptional activation; deletion mutants of Pur-alpha unable to bind T-antigen cannot suppress T-antigen transactivation.","method":"Co-immunoprecipitation, GST affinity binding assay, deletion mutagenesis, transient transfection reporter assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro GST pull-down, co-IP in vivo, and functional reporter with deletion mutants; multiple orthogonal methods","pmids":["9830007"],"is_preprint":false},{"year":1998,"finding":"A cellular RNA homologous to 7SL RNA co-purifies with Pur-alpha; this PU-RNA inhibits Pur-alpha binding to the MBP promoter MB1 DNA sequence, suggesting RNA acts as a negative co-regulator of Pur-alpha DNA-binding activity.","method":"Co-immunopurification of RNA with Pur-alpha, band-shift competition assay, Northwestern analysis with deletion mutants","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — RNA co-purification with Pur-alpha, band-shift competition, domain mapping by Northwestern; single lab, multiple methods but no in vivo functional confirmation","pmids":["9712838"],"is_preprint":false},{"year":1999,"finding":"The HIV-1 Tat–Pur-alpha interaction is mediated by RNA; a 10-nt GC-rich consensus RNA associated with Pur-alpha is required for the Pur-alpha:Tat interaction in an in vitro reconstitution assay; expression of this RNA in cells enhances HIV-1 promoter activation by Tat and Pur-alpha.","method":"In vitro reconstitution assay with purified proteins and RNA, reporter gene assay in cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified proteins plus RNA, functional reporter confirmation; two orthogonal methods in one study","pmids":["10500218"],"is_preprint":false},{"year":1999,"finding":"Pur-alpha directly associates with YB-1 protein in the absence of DNA (shown by affinity chromatography and co-immunoprecipitation); residues 85–215 of Pur-alpha and 75–203 of YB-1 mediate the interaction; Pur-alpha and YB-1 together synergistically activate JCV promoter activity via the 23-bp LCE element.","method":"Affinity chromatography, co-immunoprecipitation, band-shift assay, deletion mutagenesis, cotransfection reporter assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — reciprocal affinity chromatography and co-IP establish direct interaction; mutagenesis maps domains; functional reporter validates consequence; multiple orthogonal methods","pmids":["10082537"],"is_preprint":false},{"year":1999,"finding":"Pur-alpha associates with E2F-1 in the absence of DNA (GST pull-down and co-IP from nuclear extracts); this association inhibits E2F-1 binding to its target DNA and suppresses E2F-1-mediated transcriptional activation of the DHFR promoter; co-expression of Pur-alpha with E2F-1 increases E2F-1 protein stability.","method":"GST pull-down, combined immunoprecipitation/Western blot from nuclear extracts, band-shift assay, reporter gene cotransfection","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro GST pull-down, co-IP from cells, gel-shift, and functional reporter; multiple orthogonal methods in single study","pmids":["10597240"],"is_preprint":false},{"year":1999,"finding":"Pur-alpha self-associates in an RNA-dependent manner; the self-association domain maps to acidic leucine-rich repeats (the same region that interacts with HIV-1 Tat); Tat disrupts Pur-alpha self-association; RNA both mediates self-association and inhibits Pur-alpha binding to its target DNA sequence.","method":"GST pull-down with bacterially expressed proteins, synthetic peptides, electrophoretic mobility-shift assay with/without RNase treatment","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstitution with purified GST-fusion proteins and peptides; RNase controls; gel-shift; single lab with multiple orthogonal methods","pmids":["10412036"],"is_preprint":false},{"year":1999,"finding":"Pur-alpha cell-cycle levels decline just before S-phase onset and peak after mitosis; Pur-alpha–Rb complexes dissipate as cells enter S phase; in S/G2, Pur-alpha localizes to nuclear foci containing newly replicated DNA and co-immunoprecipitates with cyclin A from S and G2 phase extracts.","method":"Cell synchronization, co-immunoprecipitation, immunoelectron microscopy with BrdU labeling, confocal microscopy","journal":"Cell growth & differentiation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP, immunoelectron microscopy with dual labeling, and cell-cycle synchronization; multiple orthogonal methods establishing localization and interaction with functional context","pmids":["9716182"],"is_preprint":false},{"year":1999,"finding":"Microinjection of purified Pur-alpha into NIH3T3 cells arrests ~80% of cells from passing through mitosis; cells injected in S or G2 are blocked with 4N DNA content; cells injected in G1 either die or arrest at 2N or 4N.","method":"Microinjection, video time-lapse microscopy, quantitative DNA photometry of individual cells","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct protein microinjection with single-cell tracking and quantitative DNA content measurement; establishes causal role of Pur-alpha in cell-cycle arrest","pmids":["10435638"],"is_preprint":false},{"year":2000,"finding":"Pur-alpha and Pur-beta link BC1 RNA to microtubules by binding the 5'-proximal dendrite-targeting motifs (G/U-rich) of BC1 RNA; this interaction is mutually exclusive with Translin binding to the same motifs.","method":"In vitro RNA-binding assays with purified proteins, microtubule co-sedimentation, competition binding assays","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct in vitro binding assays, microtubule co-sedimentation, and competition assays; single lab, multiple methods","pmids":["11032866"],"is_preprint":false},{"year":2000,"finding":"Pur-alpha interacts with Tat in nuclear chromatin of human glial cells; Pur-alpha and Tat are co-localized in extranucleolar chromatin; the Tat–Pur-alpha interaction is direct (not through an RNA bridge) but is strongly enhanced by RNA; Tat residues 49–72 (TAR RNA-binding domain) are critical for binding Pur-alpha, while Pur-alpha repeat II domains mediate the interaction.","method":"Immunoelectron microscopy, in vitro binding of purified proteins ± RNase, peptide inhibition, domain deletion mapping","journal":"Journal of cellular biochemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — immunoelectron microscopy for localization, in vitro reconstitution with purified proteins, domain mapping; multiple orthogonal methods establishing both subcellular localization and molecular mechanism","pmids":["10679817"],"is_preprint":false},{"year":2001,"finding":"Pur-alpha has ATP-independent helix-destabilizing activity, displacing an oligonucleotide annealed to ssDNA in a dose-, time-, and temperature-dependent manner; the activity maps to the central DNA-binding region (aa 72–274) and correlates with sequence-specific DNA binding.","method":"In vitro helix-unwinding assay (oligonucleotide displacement from M13 DNA), deletion mutagenesis, heat-inactivation controls","journal":"Journal of cellular biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct enzymatic assay with purified protein, deletion mutagenesis maps domain, ATP-independence demonstrated; multiple controls in single study","pmids":["11169743"],"is_preprint":false},{"year":2001,"finding":"HIV-1 Tat, together with Pur-alpha, activates JCV DNA replication initiated at the JCV origin; in an in vitro replication system, Tat with Pur-alpha achieved >6-fold activation over T-antigen alone; Cys22 of Tat exerts a conformational effect critical for both replication activation and Pur-alpha binding.","method":"In vitro DNA replication assay, transfection-based replication assay in glial cells, mutant Tat analysis","journal":"The Journal of general virology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted replication system plus cell-based replication assay; structure-activity relationships with Tat mutants; multiple orthogonal methods","pmids":["11413364"],"is_preprint":false},{"year":2001,"finding":"Pur-alpha inhibits translation in vitro in a dose-dependent manner, likely through its association with 18S rRNA-homologous RNAs; this inhibition is abrogated by HIV-1 Tat protein.","method":"In vitro coupled transcription/translation assay with GST-Pur-alpha, luciferase reporter; RNA immunopurification and sequencing of PARNA species","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro translation assay with purified protein is rigorous but performed only in vitro; mechanism (18S rRNA interaction) inferred from sequence homology; single lab","pmids":["11596104"],"is_preprint":false},{"year":2001,"finding":"Pur-alpha protein levels and nuclear localization are cell-cycle regulated; nuclear vs. cytoplasmic localization is controlled by protein modification and specific sequence domains, including a PEST sequence (aa 215–231) and destruction motifs; in the nucleus Pur-alpha colocalizes with CDK2 and cyclin A, while at mitosis it colocalizes with cyclin B1 in the cytoplasm.","method":"Stable transfection with Pur-alpha constructs, subcellular fractionation, confocal microscopy, deletion mutant analysis","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — confocal colocalization, fractionation, and deletion mutagenesis; single lab but multiple orthogonal approaches","pmids":["11329617"],"is_preprint":false},{"year":2001,"finding":"Pur-alpha interacts with cyclin T1 and Cdk9 through distinct adjacent domains; together with Tat, this complex activates TNF-alpha promoter (a TAR-negative promoter) with Pur-alpha acting as a bridge assembling Tat, cyclin T1, and Cdk9.","method":"Protein-protein binding studies (domain mapping), cotransfection reporter assay in astrocytic cells","journal":"Journal of neuroimmunology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — direct protein binding domain mapping and functional reporter assay; single lab, two methods but domain mapping method details are limited in abstract","pmids":["11730934"],"is_preprint":false},{"year":2002,"finding":"Pur-alpha is found in mRNP complexes together with mStaufen, FMRP, and myosin Va; the co-immunoprecipitation of these proteins by anti-Pur-alpha antibody is abolished by RNase treatment, indicating RNA-dependent mRNP assembly; these mRNPs reside on rough ER equipped with a kinesin motor.","method":"EDTA-dissociation of polyribosomes, co-immunoprecipitation with/without RNase, double-RNA immunoprecipitation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — co-IP with RNase controls and kinesin identification; single lab; RNA-dependency rigorously tested","pmids":["12147688"],"is_preprint":false},{"year":2003,"finding":"Genetic inactivation of PURA in mice causes severe neurological defects (tremor, seizures) and death by 4 weeks; PURA-/- mice show reduced neuronal proliferation in hippocampus/cerebellum, aberrant lamination, reduced myelination, and absence of Cdk5 from Purkinje cell dendrites; Pur-alpha and Cdk5 co-immunoprecipitate from brain lysates of wild-type mice.","method":"Gene knockout (targeted disruption), immunohistochemistry (MCM7, GFAP, neurofilament markers), co-immunoprecipitation from brain lysates","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — constitutive knockout with multiple histological readouts plus co-IP; multiple cell types and brain regions; foundational in vivo loss-of-function study","pmids":["12972605"],"is_preprint":false},{"year":2005,"finding":"Pur-alpha specifically interacts with Cdk2 (and Cdk1) but not Cdk6 in pull-down assays; Pur-alpha stimulates histone H1 phosphorylation by cyclin A/Cdk2 several-fold in vitro; double chromatin immunoprecipitation shows Pur-alpha and Cdk2 co-occupy DNA segments upstream of c-MYC in HeLa cells.","method":"GST pull-down with purified CDKs, in vitro kinase assay with baculovirus-produced cyclin A/Cdk2, double ChIP","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay plus GST pull-down and ChIP; multiple orthogonal methods establishing physical interaction and functional enzymatic consequence","pmids":["15707957"],"is_preprint":false},{"year":2005,"finding":"Pur-alpha unwinds duplex DNA by maintaining contact with the purine-rich strand and displacing the pyrimidine-rich strand; arginine and aromatic residues in the repeat region are essential for both ssDNA and duplex DNA binding; C-terminal sequences of Pur-alpha are required for binding linearized (but not supercoiled) DNA, and Pur-alpha binding generates regularly-spaced bands on agarose gels consistent with localized unwinding quanta.","method":"In vitro strand-displacement assay, mutational analysis, potassium permanganate probing for single-stranded regions, phage T4 gp32 accessibility assay","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple in vitro biochemical assays (strand displacement, chemical probing, gp32 accessibility) with mutagenesis; rigorous mechanistic dissection in single study","pmids":["15777841"],"is_preprint":false},{"year":2006,"finding":"Pur-alpha binds BC200 RNA (human) and BC1 RNA (mouse), both implicated in dendritic targeting; Pur-alpha is specifically localized in dendrites (co-localizing with MAP2) but not axons; microtubule disruptors inhibit Pur-alpha dendritic targeting and cause its mislocalization to axons; double-RNA immunoprecipitation places Pur-alpha together with Staufen or FMRP on BC1 RNA and specific dendritic mRNAs in vivo.","method":"Immunofluorescence in hippocampal neurons in situ, RNA co-immunoprecipitation from mouse brain (double-RNA IP), microtubule disruption experiments","journal":"Journal of neuroscience research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct subcellular localization by immunofluorescence with functional perturbation (microtubule disruptors), in vivo double-RNA IP; multiple orthogonal approaches in single study","pmids":["16511857"],"is_preprint":false},{"year":2007,"finding":"Pur-alpha binds rCGG repeats in a sequence-specific manner conserved between mammals and Drosophila; overexpression of Pur-alpha in Drosophila suppresses rCGG-repeat-mediated neurodegeneration in a dose-dependent manner; Pur-alpha is present in intranuclear inclusions of FXTAS patient brains, indicating it is sequestered by expanded rCGG repeats.","method":"RNA-binding assay (sequence-specific rCGG interaction), Drosophila genetic overexpression with neurodegeneration readout, immunohistochemistry of patient brain inclusions","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNA-binding assay plus in vivo Drosophila genetic rescue (dose-dependent) plus patient tissue validation; multiple orthogonal methods across species","pmids":["17698009"],"is_preprint":false},{"year":2008,"finding":"Pur-alpha and hnRNP-K form a repressor complex that binds a specific sequence in the androgen receptor (AR) gene 5'-UTR; loss of Pur-alpha nuclear localization and AR promoter binding (by ChIP) correlates with AR overexpression in androgen-independent prostate cancer; restoring Pur-alpha expression reduces AR mRNA and protein levels; HDAC and DNA methylation inhibitors restore Pur-alpha nuclear localization and repressor complex binding.","method":"Chromatin immunoprecipitation (ChIP), co-immunoprecipitation, siRNA knockdown, plasmid overexpression, pharmacological inhibitor treatment","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP establishes in vivo occupancy, co-IP identifies complex members, KD and OE both show expected AR changes; multiple orthogonal methods","pmids":["18413735"],"is_preprint":false},{"year":2009,"finding":"X-ray crystal structure of Drosophila Pur-alpha residues 40–185 reveals a 'Whirly-like' fold comprising two nearly identical structural motifs ('PUR repeats') that form a PUR domain; PUR domains are functional nucleic-acid binding domains; PUR repeat III mediates dimerization and the dimer adopts a Z-shaped arrangement as shown by SAXS; structural analysis and mutagenesis suggest nucleic acids are bound through two independent concave beta-sheet surface regions.","method":"X-ray crystallography, small-angle X-ray scattering (SAXS), size-exclusion chromatography, DNA/RNA binding assays, mutational studies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure determination combined with SAXS, biochemical binding assays, and mutagenesis; multiple orthogonal methods providing comprehensive structural-functional characterization","pmids":["19846792"],"is_preprint":false},{"year":2016,"finding":"Crystal structure of the DNA/RNA-binding domain of Pur-alpha in complex with ssDNA reveals base-specific recognition; structure-based in vitro experiments resolved the unwindase mechanism showing a conserved phenylalanine is essential for unwinding activity; Drosophila in vivo analysis confirmed the phenylalanine is required for neuroprotective function; the structure explains how disease-causing point mutations in 5q31.3 syndrome impair function.","method":"X-ray crystallography (co-crystal with ssDNA), NMR, in vitro biochemical unwinding assay, site-directed mutagenesis, Drosophila in vivo functional assay","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with bound substrate, NMR, enzymatic assay with mutagenesis, and in vivo validation in Drosophila; multiple orthogonal methods across organisms","pmids":["26744780"],"is_preprint":false},{"year":2016,"finding":"Pur-alpha is a component of cytoplasmic stress granules (SGs) in ALS patient cells with FUS mutations; Pur-alpha physically interacts with FUS in mammalian neuronal cells; shRNA-mediated knockdown of Pur-alpha significantly reduces SG formation; ectopic Pur-alpha blocks cytoplasmic mislocalization of mutant FUS and suppresses mutant FUS toxicity in primary motor neurons.","method":"Co-immunoprecipitation, immunofluorescence co-localization, shRNA knockdown with SG quantification, overexpression in primary motor neurons with toxicity readout","journal":"Acta neuropathologica","confidence":"High","confidence_rationale":"Tier 2 / Moderate — co-IP establishes physical interaction; KD with quantitative SG readout; OE with functional toxicity rescue; multiple orthogonal methods in one study","pmids":["26728149"],"is_preprint":false},{"year":2021,"finding":"CircCwc27 directly binds Pur-alpha and increases cytoplasmic retention of Pur-alpha, suppressing Pur-alpha recruitment to promoters of AD-related genes (APP, Drd1, Ppp1r1b, Ntrk1, Lhx8); Pur-alpha overexpression phenocopies circCwc27 knockdown in preventing Aβ deposition.","method":"RNA pull-down, RIP (RNA immunoprecipitation), ChIP, knockdown/overexpression in AD mouse models","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — RNA pull-down and RIP establish binding; ChIP shows promoter occupancy changes; functional overexpression phenocopy; single lab with multiple methods","pmids":["34504314"],"is_preprint":false},{"year":2023,"finding":"DUSP8 phosphatase interacts with Pur-alpha and dephosphorylates Pur-alpha upon TGF-β signaling; dephosphorylation causes nuclear export of Pur-alpha, relieving Pur-alpha-mediated repression of the IL-9 promoter and promoting Th9 differentiation and allergic inflammation; Pur-alpha-deficient T cells show elevated Il-9 mRNA, confirming Pur-alpha acts as a transcriptional repressor of IL-9.","method":"T cell-specific conditional knockout mice, mass spectrometry, ChIP-Seq, co-immunoprecipitation, phosphorylation assay, reporter assay, mouse allergic asthma model","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout (conditional KO), mass spectrometry, ChIP-Seq, co-IP, phosphorylation assay, and in vivo disease model with rescue experiment; multiple orthogonal methods with in vivo validation","pmids":["37909329"],"is_preprint":false},{"year":2000,"finding":"Pur-alpha binds to BC1 RNA and is involved in the transcription of the BC1 RNA gene (Pol III); point mutations in the two putative Pur-alpha binding sites in the BC1 RNA gene reduce transcriptional activity in vitro; depletion of Pur-alpha from nuclear extracts inhibits BC1 RNA transcription.","method":"Co-immunoprecipitation of newly synthesized BC1 RNA, in vitro transcription assay, Pur-alpha depletion from nuclear extracts, site-directed mutagenesis of Pur-alpha binding sites","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro transcription with depletion and mutagenesis; co-IP of nascent RNA; single lab with multiple methods but only in vitro functional readout","pmids":["11032728"],"is_preprint":false},{"year":2012,"finding":"Drosophila Pur-alpha accumulates in the oocyte early in oogenesis and is part of transported mRNP complexes; RNA binding (including to r(CGG)4 and r(CAG)4 trinucleotide repeats) and dimerization are both required for efficient nuclear export of Pur-alpha-mRNP complexes and translocation into the oocyte.","method":"GFP-fusion protein localization in Drosophila oogenesis, co-purification mass spectrometry, in vitro RNA-binding assay, mutant analysis (nucleic-acid binding and dimerization mutants)","journal":"RNA biology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — live imaging of localization mutants plus RNA-binding assays; single lab; functional consequence of mutations on localization rigorously tested","pmids":["22614836"],"is_preprint":false},{"year":2020,"finding":"Pur-alpha enhances transcription of Snail2 by binding to its promoter region, thereby inducing EMT in esophageal squamous cell carcinoma; knockdown of Snail2 reverses Pur-alpha-induced EMT and suppresses migration/invasion.","method":"ChIP (chromatin immunoprecipitation), reporter assay, siRNA knockdown, RNA-seq, gain- and loss-of-function cell assays","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — ChIP establishes promoter binding, RNA-seq identifies EMT signature, epistasis (Snail2 KD rescue) places Pur-alpha upstream; single lab","pmids":["33144099"],"is_preprint":false},{"year":2023,"finding":"MEST interacts with PURA; this MEST-PURA interaction activates SRCIN1/RASAL1-ERK-Snail signaling to promote cancer metastasis; blockade of the MEST-PURA interaction with small molecule G699-0288 inhibits cancer metastasis.","method":"CRISPR/Cas9 genome-wide screen, protein interactome (co-IP/MS), surface plasmon resonance, homology modeling, modified ELISA, functional invasion/metastasis assays","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — SPR establishes direct binding, co-IP/MS identifies interaction, functional rescue experiments; single lab with multiple orthogonal methods","pmids":["37149929"],"is_preprint":false}],"current_model":"Pur-alpha (PURA) is a sequence-specific single-stranded DNA/RNA-binding protein whose central core consists of 'PUR repeat' domains with a Whirly-like fold (crystal structure resolved) that mediate sequence-specific nucleic-acid binding and ATP-independent double-strand unwinding; it functions as a transcriptional activator or repressor (depending on context) by binding G/GA-rich ssDNA elements at gene promoters, interacts with multiple cell-cycle regulators (Rb, cyclin A/Cdk2, E2F-1) to restrain S-phase entry and block mitosis, shuttles specific mRNAs to dendritic sites of translation via RNA-dependent mRNP complexes, self-associates and is regulated by associated RNAs (including 7SL-like and 18S rRNA-homologous species), and is dephosphorylated by DUSP8 to trigger nuclear export thereby de-repressing target gene promoters; loss of PURA in mice causes postnatal neurodegeneration and death, while disease-causing mutations in FXTAS and ALS sequester Pur-alpha into pathological repeat-RNA foci or stress granules, impairing its normal dendritic transport and stress-granule regulatory functions."},"narrative":{"mechanistic_narrative":"PURA (Pur-alpha) is a sequence-specific single-stranded DNA/RNA-binding protein that functions both as a context-dependent transcriptional regulator and as a component of cytoplasmic ribonucleoprotein transport machinery, with essential roles in neuronal development [PMID:12972605, PMID:19846792]. Its central nucleic-acid-binding core is built from tandem 'PUR repeats' adopting a Whirly-like fold that dimerizes and engages DNA or RNA through concave beta-sheet surfaces, recognizing target bases in a sequence-specific manner [PMID:19846792, PMID:26744780]. Through this core PURA exhibits ATP-independent helix-destabilizing (unwindase) activity, contacting the purine-rich strand of duplex DNA while displacing the pyrimidine-rich strand, an activity dependent on conserved arginine, aromatic, and a critical phenylalanine residue [PMID:11169743, PMID:15777841, PMID:26744780]. PURA acts as a transcriptional activator or repressor depending on its promoter context and protein partners: it represses E2F-1-driven transcription [PMID:10597240] and the androgen receptor gene via an hnRNP-K repressor complex [PMID:18413735], represses the IL-9 promoter in T cells [PMID:37909329], and activates JCV promoters together with YB-1 [PMID:10082537] and Snail2 to drive EMT [PMID:33144099]. PURA restrains cell-cycle progression—its levels and Rb association are cell-cycle regulated, it co-occupies promoters with and stimulates cyclin A/Cdk2, and microinjected PURA arrests cells at mitosis [PMID:9716182, PMID:10435638, PMID:15707957]. In neurons, PURA assembles into RNA-dependent mRNP complexes with Staufen, FMRP, and myosin Va, and links BC1/BC200 RNA to microtubules to drive dendritic mRNA transport [PMID:12147688, PMID:16511857, PMID:11032866]. Subcellular partitioning of PURA is tightly controlled: dephosphorylation by DUSP8 upon TGF-beta signaling triggers nuclear export and de-repression of target promoters [PMID:37909329], and binding RNAs (including 7SL- and 18S rRNA-homologous species) modulate its self-association, DNA binding, and translational activity [PMID:9712838, PMID:10412036, PMID:11596104]. Loss of PURA in mice causes postnatal neurodegeneration, seizures, and death with defective neuronal proliferation and myelination [PMID:12972605], while disease-causing point mutations underlie a 5q31.3 deletion/mutation syndrome explained structurally [PMID:26744780]; in FXTAS and ALS, PURA is sequestered into pathological rCGG-repeat inclusions and FUS-positive stress granules [PMID:17698009, PMID:26728149].","teleology":[{"year":1995,"claim":"Established that PURA physically engages the cell-cycle master regulator Rb in a manner reciprocally antagonized by its ssDNA recognition element, linking PURA's nucleic-acid-binding function to cell-cycle control.","evidence":"GST pull-down, co-IP, and deletion mutagenesis with purified proteins","pmids":["7592647"],"confidence":"High","gaps":["Did not establish the in vivo consequence of disrupting the PURA-Rb complex","Rb-binding domain mapped only by homology to SV40 large T-antigen"]},{"year":1996,"claim":"Showed PURA is co-opted by viral transcription/replication machinery, binding HIV-1 Tat and JCV T-antigen and modulating viral promoter activity and DNA replication, revealing its role as a sequence-specific regulator at viral origins.","evidence":"Co-IP, GST binding assays, DNA footprinting/band-shift, and replication/reporter assays in glial cells","pmids":["8943069","8648759"],"confidence":"High","gaps":["Did not resolve whether viral interactions reflect a cellular function co-opted by the virus","Mechanism of T-antigen stimulation of PURA ori binding not defined"]},{"year":1998,"claim":"Extended PURA's nucleic-acid binding to RNA (HIV-1 TAR) and revealed that a co-purifying 7SL-homologous RNA negatively regulates its DNA binding, introducing RNA as a co-regulator of PURA activity.","evidence":"Gel-shift with purified proteins, deletion mapping, reporter assays, and RNA co-immunopurification","pmids":["9524214","9712838"],"confidence":"High","gaps":["In vivo significance of the regulatory PU-RNA not established","Identity and biogenesis of the endogenous regulatory RNAs not fully defined"]},{"year":1999,"claim":"Defined PURA as a hub that contacts multiple transcriptional regulators (YB-1, E2F-1, cyclin A) and self-associates in an RNA-dependent manner, positioning it to integrate cell-cycle and transcription signals.","evidence":"GST pull-down, reciprocal affinity chromatography/co-IP, gel-shift, RNase controls, and reporter assays; cell synchronization with immunoEM","pmids":["10082537","10597240","10412036","9716182","10500218"],"confidence":"High","gaps":["How RNA-dependent self-association is regulated in cells not resolved","Whether E2F-1 repression operates at endogenous target genes not tested here"]},{"year":1999,"claim":"Demonstrated a direct causal role for PURA in cell-cycle arrest, showing microinjected PURA blocks mitotic transit, elevating it from a binding partner of cell-cycle regulators to a functional restraint on proliferation.","evidence":"Microinjection of purified protein with time-lapse imaging and single-cell DNA photometry in NIH3T3","pmids":["10435638"],"confidence":"High","gaps":["Molecular pathway connecting PURA to mitotic block not defined","Physiological levels versus injected excess not addressed"]},{"year":2000,"claim":"Identified PURA as a dendritic mRNA-transport factor, linking BC1 RNA to microtubules and participating in Pol III transcription of the BC1 gene, establishing its cytoplasmic RNA-transport function.","evidence":"In vitro RNA-binding, microtubule co-sedimentation, competition assays, and in vitro transcription with PURA depletion","pmids":["11032866","11032728"],"confidence":"Medium","gaps":["In vivo transport dynamics not directly visualized","Cargo mRNA repertoire not defined"]},{"year":2001,"claim":"Resolved the biochemical basis of PURA's ATP-independent helix-destabilizing activity, mapping it to the central DNA-binding region and correlating it with sequence-specific binding, and showed PURA inhibits translation via 18S rRNA-homologous RNAs.","evidence":"In vitro oligonucleotide-displacement and translation assays with purified protein, deletion mutagenesis, RNA immunopurification","pmids":["11169743","11596104","11329617","11730934"],"confidence":"High","gaps":["Physiological substrate of unwinding activity not identified","Translational inhibition demonstrated only in vitro"]},{"year":2002,"claim":"Placed PURA within neuronal mRNP transport granules containing Staufen, FMRP, and myosin Va in an RNA-dependent assembly associated with rough ER and a kinesin motor, defining its molecular context for dendritic transport.","evidence":"Polyribosome dissociation, co-IP with RNase controls, double-RNA IP","pmids":["12147688"],"confidence":"Medium","gaps":["Direct versus RNA-bridged contacts within the mRNP not dissected","Functional consequence for translation at dendrites not measured"]},{"year":2003,"claim":"Established PURA's essential in vivo role in nervous-system development, showing knockout mice die postnatally with neuronal proliferation, lamination, and myelination defects and loss of Cdk5 from Purkinje dendrites.","evidence":"Targeted gene knockout with histological markers and co-IP from brain lysates","pmids":["12972605"],"confidence":"High","gaps":["Which molecular activity (transcription, transport, unwinding) underlies the phenotype not isolated","Cell-autonomy of the defects not resolved"]},{"year":2005,"claim":"Refined PURA's cell-cycle role mechanistically, showing it binds and stimulates cyclin A/Cdk2 kinase activity and co-occupies the c-MYC promoter with Cdk2, connecting its transcriptional and kinase-regulatory functions.","evidence":"GST pull-down with CDKs, in vitro kinase assay, double ChIP in HeLa cells","pmids":["15707957"],"confidence":"High","gaps":["Net effect on c-MYC expression not quantified","Specificity of CDK stimulation in vivo not tested"]},{"year":2005,"claim":"Detailed the strand-specific unwinding mechanism, showing PURA holds the purine-rich strand while displacing the pyrimidine-rich strand and requires arginine/aromatic and C-terminal residues, advancing the structural logic of its DNA action.","evidence":"Strand-displacement, permanganate probing, gp32 accessibility, and mutational analysis","pmids":["15777841"],"confidence":"High","gaps":["Genomic loci unwound in cells not mapped","Coupling of unwinding to transcriptional output not established"]},{"year":2007,"claim":"Linked PURA to repeat-expansion neurodegeneration, showing it binds rCGG repeats, is sequestered in FXTAS patient inclusions, and dose-dependently rescues rCGG toxicity in Drosophila, defining a sequestration-based disease mechanism.","evidence":"RNA-binding assay, Drosophila genetic rescue, and patient brain immunohistochemistry","pmids":["17698009"],"confidence":"High","gaps":["Which normal PURA function is lost upon sequestration not pinpointed","Quantitative depletion of soluble PURA in patients not measured"]},{"year":2008,"claim":"Defined a PURA-hnRNP-K repressor complex at the androgen receptor gene whose loss drives AR overexpression in prostate cancer, exemplifying PURA's transcriptional-repressor role and its epigenetic regulation.","evidence":"ChIP, co-IP, siRNA/overexpression, and pharmacological HDAC/methylation inhibitor treatment","pmids":["18413735"],"confidence":"High","gaps":["Mechanism causing PURA nuclear exclusion in cancer not fully defined","Direct repressive mechanism at chromatin not dissected"]},{"year":2009,"claim":"Provided the first atomic-resolution view of the PUR domain, defining the Whirly-like fold, tandem PUR repeats, repeat-III-mediated dimerization, and dual beta-sheet nucleic-acid-binding surfaces.","evidence":"X-ray crystallography of Drosophila PURA, SAXS, SEC, and DNA/RNA binding with mutagenesis","pmids":["19846792"],"confidence":"High","gaps":["Structure lacked bound nucleic acid","Full-length and human protein architecture not resolved"]},{"year":2012,"claim":"Showed that RNA binding and dimerization are jointly required for nuclear export and cytoplasmic transport of PURA-mRNP complexes, mechanistically coupling the structural features to its transport function.","evidence":"GFP-fusion localization in Drosophila oogenesis, co-purification MS, RNA-binding and mutant analysis","pmids":["22614836"],"confidence":"Medium","gaps":["Mammalian relevance of the oogenesis transport pathway not established","Export receptor not identified"]},{"year":2016,"claim":"Resolved how PURA recognizes ssDNA and unwinds duplex, identifying an essential phenylalanine required for both unwinding and neuroprotection, and explained the structural basis of 5q31.3-syndrome point mutations.","evidence":"Co-crystal structure with ssDNA, NMR, in vitro unwinding assay, mutagenesis, and Drosophila in vivo assay","pmids":["26744780"],"confidence":"High","gaps":["In vivo unwinding substrates in mammalian neurons not identified","Genotype-phenotype map across patient mutations incomplete"]},{"year":2016,"claim":"Connected PURA to ALS pathology, showing it interacts with FUS, is recruited to stress granules, is required for SG formation, and suppresses mutant FUS mislocalization and toxicity, defining a stress-granule regulatory role.","evidence":"Co-IP, immunofluorescence co-localization, shRNA knockdown with SG quantification, and overexpression toxicity rescue in motor neurons","pmids":["26728149"],"confidence":"High","gaps":["Whether PURA acts as a scaffold or signaling component of SGs not resolved","Direct versus indirect FUS contact not mapped at residue level"]},{"year":2023,"claim":"Identified DUSP8-mediated dephosphorylation as a signal-controlled switch driving PURA nuclear export and de-repression of the IL-9 promoter, providing a post-translational mechanism governing PURA's repressor activity in T cells.","evidence":"T cell conditional knockout, mass spectrometry, ChIP-Seq, co-IP, phosphorylation and reporter assays, and an allergic asthma model","pmids":["37909329"],"confidence":"High","gaps":["Kinase counteracting DUSP8 not identified","Generalizability of the phospho-switch to other PURA target genes not tested"]},{"year":2023,"claim":"Expanded PURA's oncogenic interactome by identifying the MEST-PURA interaction driving ERK-Snail metastatic signaling and a small molecule blocking it, while circRNA-mediated cytoplasmic retention regulating promoter recruitment links RNA control to disease.","evidence":"CRISPR screen, co-IP/MS, SPR, invasion/metastasis assays; RNA pull-down/RIP/ChIP in AD models","pmids":["37149929","34504314","33144099"],"confidence":"Medium","gaps":["Whether MEST-PURA signaling depends on PURA nucleic-acid binding not resolved","Direct versus indirect effects on the named target genes not fully separated"]},{"year":null,"claim":"How PURA's distinct molecular activities—sequence-specific transcription, ATP-independent unwinding, and RNA transport—are partitioned and prioritized in vivo, and which activity is decisive for its neurodevelopmental essentiality, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No separation-of-function in vivo dissection linking specific activities to the knockout phenotype","Genome-wide endogenous DNA/RNA target maps incomplete","Physiological unwinding substrates unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,14,22,27,26]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[3,5,12,16,23,24]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[7,8,25,30,33]},{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[14,22,27]},{"term_id":"GO:0045182","term_label":"translation regulator 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RNA","supporting_discovery_ids":[12,19,23]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[24,28,27]}],"complexes":["dendritic transport mRNP (with Staufen/FMRP/myosin Va)","PURA-hnRNP-K repressor complex","cytoplasmic stress granule"],"partners":["RB1","E2F1","CDK2","YB-1","FUS","HNRNPK","DUSP8","MEST"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q00577","full_name":"Transcriptional activator protein Pur-alpha","aliases":["Purine-rich single-stranded DNA-binding protein alpha"],"length_aa":322,"mass_kda":34.9,"function":"This is a probable transcription activator that specifically binds the purine-rich single strand of the PUR element located upstream of the MYC gene (PubMed:1448097, PubMed:20976240). May play a role in the initiation of DNA replication and in recombination","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q00577/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PURA","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/PURA","total_profiled":1310},"omim":[{"mim_id":"620106","title":"SPASTIC PARAPLEGIA 88, AUTOSOMAL DOMINANT; SPG88","url":"https://www.omim.org/entry/620106"},{"mim_id":"618041","title":"PURINE-RICH ELEMENT-BINDING PROTEIN G; PURG","url":"https://www.omim.org/entry/618041"},{"mim_id":"616158","title":"NEURODEVELOPMENTAL DISORDER WITH NEONATAL RESPIRATORY INSUFFICIENCY, HYPOTONIA, AND FEEDING DIFFICULTIES; NEDRIHF","url":"https://www.omim.org/entry/616158"},{"mim_id":"608887","title":"PURINE-RICH ELEMENT-BINDING PROTEIN B; PURB","url":"https://www.omim.org/entry/608887"},{"mim_id":"608188","title":"CARDIOLIPIN SYNTHASE 1; CRLS1","url":"https://www.omim.org/entry/608188"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PURA"},"hgnc":{"alias_symbol":["PURALPHA","PUR1","PUR-ALPHA"],"prev_symbol":[]},"alphafold":{"accession":"Q00577","domains":[{"cath_id":"3.30.2450.30","chopping":"58-126_139-208","consensus_level":"high","plddt":87.6847,"start":58,"end":208},{"cath_id":"3.10.450.700","chopping":"221-295","consensus_level":"high","plddt":91.2944,"start":221,"end":295}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q00577","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q00577-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q00577-F1-predicted_aligned_error_v6.png","plddt_mean":78.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PURA","jax_strain_url":"https://www.jax.org/strain/search?query=PURA"},"sequence":{"accession":"Q00577","fasta_url":"https://rest.uniprot.org/uniprotkb/Q00577.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q00577/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q00577"}},"corpus_meta":[{"pmid":"17698009","id":"PMC_17698009","title":"Pur 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The Occurrence of the Golgi Dictyosome in the Fungus Neobulgaria pura (Fr.) 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Is GLUT1 a new PURA target?","date":"2018","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/29307761","citation_count":19,"is_preprint":false},{"pmid":"16741925","id":"PMC_16741925","title":"Regulation of the Pur-alpha promoter by E2F-1.","date":"2006","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16741925","citation_count":18,"is_preprint":false},{"pmid":"7606931","id":"PMC_7606931","title":"Localization of PURA, the gene encoding the sequence-specific single-stranded-DNA-binding protein Pur alpha, to chromosome band 5q31.","date":"1995","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/7606931","citation_count":18,"is_preprint":false},{"pmid":"26582469","id":"PMC_26582469","title":"Long-term follow-up of a patient with 5q31.3 microdeletion syndrome and the smallest de novo 5q31.2q31.3 deletion involving PURA.","date":"2015","source":"Molecular cytogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/26582469","citation_count":18,"is_preprint":false},{"pmid":"24446247","id":"PMC_24446247","title":"The Purα/Purβ single-strand DNA-binding proteins attenuate smooth-muscle actin gene transactivation in myofibroblasts.","date":"2014","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/24446247","citation_count":17,"is_preprint":false},{"pmid":"15777709","id":"PMC_15777709","title":"Puralpha activates PDGF-A gene transcription via interactions with a G-rich, single-stranded region of the promoter.","date":"2005","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/15777709","citation_count":17,"is_preprint":false},{"pmid":"11256476","id":"PMC_11256476","title":"Pur alpha protein implicated in dendritic RNA transport interacts with ribosomes in neuronal cytoplasm.","date":"2001","source":"Biological & pharmaceutical bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/11256476","citation_count":17,"is_preprint":false},{"pmid":"18344281","id":"PMC_18344281","title":"Serum response factor neutralizes Pur alpha- and Pur beta-mediated repression of the fetal vascular smooth muscle alpha-actin gene in stressed adult cardiomyocytes.","date":"2008","source":"American journal of physiology. 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the single-stranded DNA Pur-alpha recognition element disrupts the Pur-alpha–Rb complex, and conversely high concentrations of Rb prevent Pur-alpha from binding DNA.\",\n      \"method\": \"GST pull-down with purified proteins, co-immunoprecipitation from cell lysates, deletion mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with GST-fusion proteins, co-IP from cell extracts, and deletion mutagenesis all in one study; reciprocal inhibition experiments provided functional validation\",\n      \"pmids\": [\"7592647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"HIV-1 Tat protein interacts with Pur-alpha through two leucine-rich repeats in Pur-alpha; Tat enhances Pur-alpha binding to the JCV upTAR element and together they synergistically activate transcription from an upTAR-containing promoter in a cell-cycle-dependent manner.\",\n      \"method\": \"Co-immunoprecipitation from cell extracts, GST-Pur-alpha binding assay, transcription reporter (cotransfection)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro binding with purified GST-Pur-alpha, co-IP from cells, functional reporter assay; multiple orthogonal methods in one study\",\n      \"pmids\": [\"8943069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Overexpression of Pur-alpha suppresses replication of JCV DNA in glial cells; Pur-alpha and JCV T-antigen share a common binding region in the single-stranded JCV ori sequence, and T-antigen stimulates Pur-alpha association with the ori; co-immunoprecipitation revealed a molecular association between Pur-alpha and JCV T-antigen in cells.\",\n      \"method\": \"JCV DNA replication assay in transfected cells, DNA footprinting, band-shift assay, co-immunoprecipitation/Western blot\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — functional replication assay plus footprinting, band-shift, and co-IP; multiple orthogonal methods establishing both physical interaction and functional consequence\",\n      \"pmids\": [\"8648759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Pur-alpha binds HIV-1 TAR RNA in a sequence-specific manner; amino acids 55–85 (first basic aromatic repeat) are important for TAR RNA binding; overexpression of Pur-alpha increases transcription of the HIV-1 LTR through a TAR-dependent mechanism.\",\n      \"method\": \"Competition gel-shift analysis with purified proteins, deletion-mutant mapping, reporter gene assay in glial cells\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro binding with purified proteins, domain mapping by deletion mutants, and functional reporter assay; multiple orthogonal methods\",\n      \"pmids\": [\"9524214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Pur-alpha physically and functionally interacts with JCV large T-antigen; the interaction attenuates T-antigen-mediated transcriptional activation; deletion mutants of Pur-alpha unable to bind T-antigen cannot suppress T-antigen transactivation.\",\n      \"method\": \"Co-immunoprecipitation, GST affinity binding assay, deletion mutagenesis, transient transfection reporter assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro GST pull-down, co-IP in vivo, and functional reporter with deletion mutants; multiple orthogonal methods\",\n      \"pmids\": [\"9830007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A cellular RNA homologous to 7SL RNA co-purifies with Pur-alpha; this PU-RNA inhibits Pur-alpha binding to the MBP promoter MB1 DNA sequence, suggesting RNA acts as a negative co-regulator of Pur-alpha DNA-binding activity.\",\n      \"method\": \"Co-immunopurification of RNA with Pur-alpha, band-shift competition assay, Northwestern analysis with deletion mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — RNA co-purification with Pur-alpha, band-shift competition, domain mapping by Northwestern; single lab, multiple methods but no in vivo functional confirmation\",\n      \"pmids\": [\"9712838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The HIV-1 Tat–Pur-alpha interaction is mediated by RNA; a 10-nt GC-rich consensus RNA associated with Pur-alpha is required for the Pur-alpha:Tat interaction in an in vitro reconstitution assay; expression of this RNA in cells enhances HIV-1 promoter activation by Tat and Pur-alpha.\",\n      \"method\": \"In vitro reconstitution assay with purified proteins and RNA, reporter gene assay in cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified proteins plus RNA, functional reporter confirmation; two orthogonal methods in one study\",\n      \"pmids\": [\"10500218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Pur-alpha directly associates with YB-1 protein in the absence of DNA (shown by affinity chromatography and co-immunoprecipitation); residues 85–215 of Pur-alpha and 75–203 of YB-1 mediate the interaction; Pur-alpha and YB-1 together synergistically activate JCV promoter activity via the 23-bp LCE element.\",\n      \"method\": \"Affinity chromatography, co-immunoprecipitation, band-shift assay, deletion mutagenesis, cotransfection reporter assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — reciprocal affinity chromatography and co-IP establish direct interaction; mutagenesis maps domains; functional reporter validates consequence; multiple orthogonal methods\",\n      \"pmids\": [\"10082537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Pur-alpha associates with E2F-1 in the absence of DNA (GST pull-down and co-IP from nuclear extracts); this association inhibits E2F-1 binding to its target DNA and suppresses E2F-1-mediated transcriptional activation of the DHFR promoter; co-expression of Pur-alpha with E2F-1 increases E2F-1 protein stability.\",\n      \"method\": \"GST pull-down, combined immunoprecipitation/Western blot from nuclear extracts, band-shift assay, reporter gene cotransfection\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro GST pull-down, co-IP from cells, gel-shift, and functional reporter; multiple orthogonal methods in single study\",\n      \"pmids\": [\"10597240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Pur-alpha self-associates in an RNA-dependent manner; the self-association domain maps to acidic leucine-rich repeats (the same region that interacts with HIV-1 Tat); Tat disrupts Pur-alpha self-association; RNA both mediates self-association and inhibits Pur-alpha binding to its target DNA sequence.\",\n      \"method\": \"GST pull-down with bacterially expressed proteins, synthetic peptides, electrophoretic mobility-shift assay with/without RNase treatment\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstitution with purified GST-fusion proteins and peptides; RNase controls; gel-shift; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"10412036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Pur-alpha cell-cycle levels decline just before S-phase onset and peak after mitosis; Pur-alpha–Rb complexes dissipate as cells enter S phase; in S/G2, Pur-alpha localizes to nuclear foci containing newly replicated DNA and co-immunoprecipitates with cyclin A from S and G2 phase extracts.\",\n      \"method\": \"Cell synchronization, co-immunoprecipitation, immunoelectron microscopy with BrdU labeling, confocal microscopy\",\n      \"journal\": \"Cell growth & differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP, immunoelectron microscopy with dual labeling, and cell-cycle synchronization; multiple orthogonal methods establishing localization and interaction with functional context\",\n      \"pmids\": [\"9716182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Microinjection of purified Pur-alpha into NIH3T3 cells arrests ~80% of cells from passing through mitosis; cells injected in S or G2 are blocked with 4N DNA content; cells injected in G1 either die or arrest at 2N or 4N.\",\n      \"method\": \"Microinjection, video time-lapse microscopy, quantitative DNA photometry of individual cells\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct protein microinjection with single-cell tracking and quantitative DNA content measurement; establishes causal role of Pur-alpha in cell-cycle arrest\",\n      \"pmids\": [\"10435638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Pur-alpha and Pur-beta link BC1 RNA to microtubules by binding the 5'-proximal dendrite-targeting motifs (G/U-rich) of BC1 RNA; this interaction is mutually exclusive with Translin binding to the same motifs.\",\n      \"method\": \"In vitro RNA-binding assays with purified proteins, microtubule co-sedimentation, competition binding assays\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct in vitro binding assays, microtubule co-sedimentation, and competition assays; single lab, multiple methods\",\n      \"pmids\": [\"11032866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Pur-alpha interacts with Tat in nuclear chromatin of human glial cells; Pur-alpha and Tat are co-localized in extranucleolar chromatin; the Tat–Pur-alpha interaction is direct (not through an RNA bridge) but is strongly enhanced by RNA; Tat residues 49–72 (TAR RNA-binding domain) are critical for binding Pur-alpha, while Pur-alpha repeat II domains mediate the interaction.\",\n      \"method\": \"Immunoelectron microscopy, in vitro binding of purified proteins ± RNase, peptide inhibition, domain deletion mapping\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — immunoelectron microscopy for localization, in vitro reconstitution with purified proteins, domain mapping; multiple orthogonal methods establishing both subcellular localization and molecular mechanism\",\n      \"pmids\": [\"10679817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Pur-alpha has ATP-independent helix-destabilizing activity, displacing an oligonucleotide annealed to ssDNA in a dose-, time-, and temperature-dependent manner; the activity maps to the central DNA-binding region (aa 72–274) and correlates with sequence-specific DNA binding.\",\n      \"method\": \"In vitro helix-unwinding assay (oligonucleotide displacement from M13 DNA), deletion mutagenesis, heat-inactivation controls\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct enzymatic assay with purified protein, deletion mutagenesis maps domain, ATP-independence demonstrated; multiple controls in single study\",\n      \"pmids\": [\"11169743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"HIV-1 Tat, together with Pur-alpha, activates JCV DNA replication initiated at the JCV origin; in an in vitro replication system, Tat with Pur-alpha achieved >6-fold activation over T-antigen alone; Cys22 of Tat exerts a conformational effect critical for both replication activation and Pur-alpha binding.\",\n      \"method\": \"In vitro DNA replication assay, transfection-based replication assay in glial cells, mutant Tat analysis\",\n      \"journal\": \"The Journal of general virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted replication system plus cell-based replication assay; structure-activity relationships with Tat mutants; multiple orthogonal methods\",\n      \"pmids\": [\"11413364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Pur-alpha inhibits translation in vitro in a dose-dependent manner, likely through its association with 18S rRNA-homologous RNAs; this inhibition is abrogated by HIV-1 Tat protein.\",\n      \"method\": \"In vitro coupled transcription/translation assay with GST-Pur-alpha, luciferase reporter; RNA immunopurification and sequencing of PARNA species\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro translation assay with purified protein is rigorous but performed only in vitro; mechanism (18S rRNA interaction) inferred from sequence homology; single lab\",\n      \"pmids\": [\"11596104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Pur-alpha protein levels and nuclear localization are cell-cycle regulated; nuclear vs. cytoplasmic localization is controlled by protein modification and specific sequence domains, including a PEST sequence (aa 215–231) and destruction motifs; in the nucleus Pur-alpha colocalizes with CDK2 and cyclin A, while at mitosis it colocalizes with cyclin B1 in the cytoplasm.\",\n      \"method\": \"Stable transfection with Pur-alpha constructs, subcellular fractionation, confocal microscopy, deletion mutant analysis\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — confocal colocalization, fractionation, and deletion mutagenesis; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"11329617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Pur-alpha interacts with cyclin T1 and Cdk9 through distinct adjacent domains; together with Tat, this complex activates TNF-alpha promoter (a TAR-negative promoter) with Pur-alpha acting as a bridge assembling Tat, cyclin T1, and Cdk9.\",\n      \"method\": \"Protein-protein binding studies (domain mapping), cotransfection reporter assay in astrocytic cells\",\n      \"journal\": \"Journal of neuroimmunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — direct protein binding domain mapping and functional reporter assay; single lab, two methods but domain mapping method details are limited in abstract\",\n      \"pmids\": [\"11730934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Pur-alpha is found in mRNP complexes together with mStaufen, FMRP, and myosin Va; the co-immunoprecipitation of these proteins by anti-Pur-alpha antibody is abolished by RNase treatment, indicating RNA-dependent mRNP assembly; these mRNPs reside on rough ER equipped with a kinesin motor.\",\n      \"method\": \"EDTA-dissociation of polyribosomes, co-immunoprecipitation with/without RNase, double-RNA immunoprecipitation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — co-IP with RNase controls and kinesin identification; single lab; RNA-dependency rigorously tested\",\n      \"pmids\": [\"12147688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Genetic inactivation of PURA in mice causes severe neurological defects (tremor, seizures) and death by 4 weeks; PURA-/- mice show reduced neuronal proliferation in hippocampus/cerebellum, aberrant lamination, reduced myelination, and absence of Cdk5 from Purkinje cell dendrites; Pur-alpha and Cdk5 co-immunoprecipitate from brain lysates of wild-type mice.\",\n      \"method\": \"Gene knockout (targeted disruption), immunohistochemistry (MCM7, GFAP, neurofilament markers), co-immunoprecipitation from brain lysates\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — constitutive knockout with multiple histological readouts plus co-IP; multiple cell types and brain regions; foundational in vivo loss-of-function study\",\n      \"pmids\": [\"12972605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Pur-alpha specifically interacts with Cdk2 (and Cdk1) but not Cdk6 in pull-down assays; Pur-alpha stimulates histone H1 phosphorylation by cyclin A/Cdk2 several-fold in vitro; double chromatin immunoprecipitation shows Pur-alpha and Cdk2 co-occupy DNA segments upstream of c-MYC in HeLa cells.\",\n      \"method\": \"GST pull-down with purified CDKs, in vitro kinase assay with baculovirus-produced cyclin A/Cdk2, double ChIP\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay plus GST pull-down and ChIP; multiple orthogonal methods establishing physical interaction and functional enzymatic consequence\",\n      \"pmids\": [\"15707957\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Pur-alpha unwinds duplex DNA by maintaining contact with the purine-rich strand and displacing the pyrimidine-rich strand; arginine and aromatic residues in the repeat region are essential for both ssDNA and duplex DNA binding; C-terminal sequences of Pur-alpha are required for binding linearized (but not supercoiled) DNA, and Pur-alpha binding generates regularly-spaced bands on agarose gels consistent with localized unwinding quanta.\",\n      \"method\": \"In vitro strand-displacement assay, mutational analysis, potassium permanganate probing for single-stranded regions, phage T4 gp32 accessibility assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple in vitro biochemical assays (strand displacement, chemical probing, gp32 accessibility) with mutagenesis; rigorous mechanistic dissection in single study\",\n      \"pmids\": [\"15777841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Pur-alpha binds BC200 RNA (human) and BC1 RNA (mouse), both implicated in dendritic targeting; Pur-alpha is specifically localized in dendrites (co-localizing with MAP2) but not axons; microtubule disruptors inhibit Pur-alpha dendritic targeting and cause its mislocalization to axons; double-RNA immunoprecipitation places Pur-alpha together with Staufen or FMRP on BC1 RNA and specific dendritic mRNAs in vivo.\",\n      \"method\": \"Immunofluorescence in hippocampal neurons in situ, RNA co-immunoprecipitation from mouse brain (double-RNA IP), microtubule disruption experiments\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct subcellular localization by immunofluorescence with functional perturbation (microtubule disruptors), in vivo double-RNA IP; multiple orthogonal approaches in single study\",\n      \"pmids\": [\"16511857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Pur-alpha binds rCGG repeats in a sequence-specific manner conserved between mammals and Drosophila; overexpression of Pur-alpha in Drosophila suppresses rCGG-repeat-mediated neurodegeneration in a dose-dependent manner; Pur-alpha is present in intranuclear inclusions of FXTAS patient brains, indicating it is sequestered by expanded rCGG repeats.\",\n      \"method\": \"RNA-binding assay (sequence-specific rCGG interaction), Drosophila genetic overexpression with neurodegeneration readout, immunohistochemistry of patient brain inclusions\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNA-binding assay plus in vivo Drosophila genetic rescue (dose-dependent) plus patient tissue validation; multiple orthogonal methods across species\",\n      \"pmids\": [\"17698009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Pur-alpha and hnRNP-K form a repressor complex that binds a specific sequence in the androgen receptor (AR) gene 5'-UTR; loss of Pur-alpha nuclear localization and AR promoter binding (by ChIP) correlates with AR overexpression in androgen-independent prostate cancer; restoring Pur-alpha expression reduces AR mRNA and protein levels; HDAC and DNA methylation inhibitors restore Pur-alpha nuclear localization and repressor complex binding.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), co-immunoprecipitation, siRNA knockdown, plasmid overexpression, pharmacological inhibitor treatment\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP establishes in vivo occupancy, co-IP identifies complex members, KD and OE both show expected AR changes; multiple orthogonal methods\",\n      \"pmids\": [\"18413735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"X-ray crystal structure of Drosophila Pur-alpha residues 40–185 reveals a 'Whirly-like' fold comprising two nearly identical structural motifs ('PUR repeats') that form a PUR domain; PUR domains are functional nucleic-acid binding domains; PUR repeat III mediates dimerization and the dimer adopts a Z-shaped arrangement as shown by SAXS; structural analysis and mutagenesis suggest nucleic acids are bound through two independent concave beta-sheet surface regions.\",\n      \"method\": \"X-ray crystallography, small-angle X-ray scattering (SAXS), size-exclusion chromatography, DNA/RNA binding assays, mutational studies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure determination combined with SAXS, biochemical binding assays, and mutagenesis; multiple orthogonal methods providing comprehensive structural-functional characterization\",\n      \"pmids\": [\"19846792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of the DNA/RNA-binding domain of Pur-alpha in complex with ssDNA reveals base-specific recognition; structure-based in vitro experiments resolved the unwindase mechanism showing a conserved phenylalanine is essential for unwinding activity; Drosophila in vivo analysis confirmed the phenylalanine is required for neuroprotective function; the structure explains how disease-causing point mutations in 5q31.3 syndrome impair function.\",\n      \"method\": \"X-ray crystallography (co-crystal with ssDNA), NMR, in vitro biochemical unwinding assay, site-directed mutagenesis, Drosophila in vivo functional assay\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with bound substrate, NMR, enzymatic assay with mutagenesis, and in vivo validation in Drosophila; multiple orthogonal methods across organisms\",\n      \"pmids\": [\"26744780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Pur-alpha is a component of cytoplasmic stress granules (SGs) in ALS patient cells with FUS mutations; Pur-alpha physically interacts with FUS in mammalian neuronal cells; shRNA-mediated knockdown of Pur-alpha significantly reduces SG formation; ectopic Pur-alpha blocks cytoplasmic mislocalization of mutant FUS and suppresses mutant FUS toxicity in primary motor neurons.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, shRNA knockdown with SG quantification, overexpression in primary motor neurons with toxicity readout\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP establishes physical interaction; KD with quantitative SG readout; OE with functional toxicity rescue; multiple orthogonal methods in one study\",\n      \"pmids\": [\"26728149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CircCwc27 directly binds Pur-alpha and increases cytoplasmic retention of Pur-alpha, suppressing Pur-alpha recruitment to promoters of AD-related genes (APP, Drd1, Ppp1r1b, Ntrk1, Lhx8); Pur-alpha overexpression phenocopies circCwc27 knockdown in preventing Aβ deposition.\",\n      \"method\": \"RNA pull-down, RIP (RNA immunoprecipitation), ChIP, knockdown/overexpression in AD mouse models\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — RNA pull-down and RIP establish binding; ChIP shows promoter occupancy changes; functional overexpression phenocopy; single lab with multiple methods\",\n      \"pmids\": [\"34504314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DUSP8 phosphatase interacts with Pur-alpha and dephosphorylates Pur-alpha upon TGF-β signaling; dephosphorylation causes nuclear export of Pur-alpha, relieving Pur-alpha-mediated repression of the IL-9 promoter and promoting Th9 differentiation and allergic inflammation; Pur-alpha-deficient T cells show elevated Il-9 mRNA, confirming Pur-alpha acts as a transcriptional repressor of IL-9.\",\n      \"method\": \"T cell-specific conditional knockout mice, mass spectrometry, ChIP-Seq, co-immunoprecipitation, phosphorylation assay, reporter assay, mouse allergic asthma model\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout (conditional KO), mass spectrometry, ChIP-Seq, co-IP, phosphorylation assay, and in vivo disease model with rescue experiment; multiple orthogonal methods with in vivo validation\",\n      \"pmids\": [\"37909329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Pur-alpha binds to BC1 RNA and is involved in the transcription of the BC1 RNA gene (Pol III); point mutations in the two putative Pur-alpha binding sites in the BC1 RNA gene reduce transcriptional activity in vitro; depletion of Pur-alpha from nuclear extracts inhibits BC1 RNA transcription.\",\n      \"method\": \"Co-immunoprecipitation of newly synthesized BC1 RNA, in vitro transcription assay, Pur-alpha depletion from nuclear extracts, site-directed mutagenesis of Pur-alpha binding sites\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro transcription with depletion and mutagenesis; co-IP of nascent RNA; single lab with multiple methods but only in vitro functional readout\",\n      \"pmids\": [\"11032728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Drosophila Pur-alpha accumulates in the oocyte early in oogenesis and is part of transported mRNP complexes; RNA binding (including to r(CGG)4 and r(CAG)4 trinucleotide repeats) and dimerization are both required for efficient nuclear export of Pur-alpha-mRNP complexes and translocation into the oocyte.\",\n      \"method\": \"GFP-fusion protein localization in Drosophila oogenesis, co-purification mass spectrometry, in vitro RNA-binding assay, mutant analysis (nucleic-acid binding and dimerization mutants)\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — live imaging of localization mutants plus RNA-binding assays; single lab; functional consequence of mutations on localization rigorously tested\",\n      \"pmids\": [\"22614836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Pur-alpha enhances transcription of Snail2 by binding to its promoter region, thereby inducing EMT in esophageal squamous cell carcinoma; knockdown of Snail2 reverses Pur-alpha-induced EMT and suppresses migration/invasion.\",\n      \"method\": \"ChIP (chromatin immunoprecipitation), reporter assay, siRNA knockdown, RNA-seq, gain- and loss-of-function cell assays\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — ChIP establishes promoter binding, RNA-seq identifies EMT signature, epistasis (Snail2 KD rescue) places Pur-alpha upstream; single lab\",\n      \"pmids\": [\"33144099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEST interacts with PURA; this MEST-PURA interaction activates SRCIN1/RASAL1-ERK-Snail signaling to promote cancer metastasis; blockade of the MEST-PURA interaction with small molecule G699-0288 inhibits cancer metastasis.\",\n      \"method\": \"CRISPR/Cas9 genome-wide screen, protein interactome (co-IP/MS), surface plasmon resonance, homology modeling, modified ELISA, functional invasion/metastasis assays\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SPR establishes direct binding, co-IP/MS identifies interaction, functional rescue experiments; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37149929\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Pur-alpha (PURA) is a sequence-specific single-stranded DNA/RNA-binding protein whose central core consists of 'PUR repeat' domains with a Whirly-like fold (crystal structure resolved) that mediate sequence-specific nucleic-acid binding and ATP-independent double-strand unwinding; it functions as a transcriptional activator or repressor (depending on context) by binding G/GA-rich ssDNA elements at gene promoters, interacts with multiple cell-cycle regulators (Rb, cyclin A/Cdk2, E2F-1) to restrain S-phase entry and block mitosis, shuttles specific mRNAs to dendritic sites of translation via RNA-dependent mRNP complexes, self-associates and is regulated by associated RNAs (including 7SL-like and 18S rRNA-homologous species), and is dephosphorylated by DUSP8 to trigger nuclear export thereby de-repressing target gene promoters; loss of PURA in mice causes postnatal neurodegeneration and death, while disease-causing mutations in FXTAS and ALS sequester Pur-alpha into pathological repeat-RNA foci or stress granules, impairing its normal dendritic transport and stress-granule regulatory functions.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PURA (Pur-alpha) is a sequence-specific single-stranded DNA/RNA-binding protein that functions both as a context-dependent transcriptional regulator and as a component of cytoplasmic ribonucleoprotein transport machinery, with essential roles in neuronal development [#20, #26]. Its central nucleic-acid-binding core is built from tandem 'PUR repeats' adopting a Whirly-like fold that dimerizes and engages DNA or RNA through concave beta-sheet surfaces, recognizing target bases in a sequence-specific manner [#26, #27]. Through this core PURA exhibits ATP-independent helix-destabilizing (unwindase) activity, contacting the purine-rich strand of duplex DNA while displacing the pyrimidine-rich strand, an activity dependent on conserved arginine, aromatic, and a critical phenylalanine residue [#14, #22, #27]. PURA acts as a transcriptional activator or repressor depending on its promoter context and protein partners: it represses E2F-1-driven transcription [#8] and the androgen receptor gene via an hnRNP-K repressor complex [#25], represses the IL-9 promoter in T cells [#30], and activates JCV promoters together with YB-1 [#7] and Snail2 to drive EMT [#33]. PURA restrains cell-cycle progression—its levels and Rb association are cell-cycle regulated, it co-occupies promoters with and stimulates cyclin A/Cdk2, and microinjected PURA arrests cells at mitosis [#10, #11, #21]. In neurons, PURA assembles into RNA-dependent mRNP complexes with Staufen, FMRP, and myosin Va, and links BC1/BC200 RNA to microtubules to drive dendritic mRNA transport [#19, #23, #12]. Subcellular partitioning of PURA is tightly controlled: dephosphorylation by DUSP8 upon TGF-beta signaling triggers nuclear export and de-repression of target promoters [#30], and binding RNAs (including 7SL- and 18S rRNA-homologous species) modulate its self-association, DNA binding, and translational activity [#5, #9, #16]. Loss of PURA in mice causes postnatal neurodegeneration, seizures, and death with defective neuronal proliferation and myelination [#20], while disease-causing point mutations underlie a 5q31.3 deletion/mutation syndrome explained structurally [#27]; in FXTAS and ALS, PURA is sequestered into pathological rCGG-repeat inclusions and FUS-positive stress granules [#24, #28].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established that PURA physically engages the cell-cycle master regulator Rb in a manner reciprocally antagonized by its ssDNA recognition element, linking PURA's nucleic-acid-binding function to cell-cycle control.\",\n      \"evidence\": \"GST pull-down, co-IP, and deletion mutagenesis with purified proteins\",\n      \"pmids\": [\"7592647\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish the in vivo consequence of disrupting the PURA-Rb complex\", \"Rb-binding domain mapped only by homology to SV40 large T-antigen\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Showed PURA is co-opted by viral transcription/replication machinery, binding HIV-1 Tat and JCV T-antigen and modulating viral promoter activity and DNA replication, revealing its role as a sequence-specific regulator at viral origins.\",\n      \"evidence\": \"Co-IP, GST binding assays, DNA footprinting/band-shift, and replication/reporter assays in glial cells\",\n      \"pmids\": [\"8943069\", \"8648759\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether viral interactions reflect a cellular function co-opted by the virus\", \"Mechanism of T-antigen stimulation of PURA ori binding not defined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Extended PURA's nucleic-acid binding to RNA (HIV-1 TAR) and revealed that a co-purifying 7SL-homologous RNA negatively regulates its DNA binding, introducing RNA as a co-regulator of PURA activity.\",\n      \"evidence\": \"Gel-shift with purified proteins, deletion mapping, reporter assays, and RNA co-immunopurification\",\n      \"pmids\": [\"9524214\", \"9712838\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo significance of the regulatory PU-RNA not established\", \"Identity and biogenesis of the endogenous regulatory RNAs not fully defined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Defined PURA as a hub that contacts multiple transcriptional regulators (YB-1, E2F-1, cyclin A) and self-associates in an RNA-dependent manner, positioning it to integrate cell-cycle and transcription signals.\",\n      \"evidence\": \"GST pull-down, reciprocal affinity chromatography/co-IP, gel-shift, RNase controls, and reporter assays; cell synchronization with immunoEM\",\n      \"pmids\": [\"10082537\", \"10597240\", \"10412036\", \"9716182\", \"10500218\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RNA-dependent self-association is regulated in cells not resolved\", \"Whether E2F-1 repression operates at endogenous target genes not tested here\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrated a direct causal role for PURA in cell-cycle arrest, showing microinjected PURA blocks mitotic transit, elevating it from a binding partner of cell-cycle regulators to a functional restraint on proliferation.\",\n      \"evidence\": \"Microinjection of purified protein with time-lapse imaging and single-cell DNA photometry in NIH3T3\",\n      \"pmids\": [\"10435638\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular pathway connecting PURA to mitotic block not defined\", \"Physiological levels versus injected excess not addressed\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified PURA as a dendritic mRNA-transport factor, linking BC1 RNA to microtubules and participating in Pol III transcription of the BC1 gene, establishing its cytoplasmic RNA-transport function.\",\n      \"evidence\": \"In vitro RNA-binding, microtubule co-sedimentation, competition assays, and in vitro transcription with PURA depletion\",\n      \"pmids\": [\"11032866\", \"11032728\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo transport dynamics not directly visualized\", \"Cargo mRNA repertoire not defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Resolved the biochemical basis of PURA's ATP-independent helix-destabilizing activity, mapping it to the central DNA-binding region and correlating it with sequence-specific binding, and showed PURA inhibits translation via 18S rRNA-homologous RNAs.\",\n      \"evidence\": \"In vitro oligonucleotide-displacement and translation assays with purified protein, deletion mutagenesis, RNA immunopurification\",\n      \"pmids\": [\"11169743\", \"11596104\", \"11329617\", \"11730934\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrate of unwinding activity not identified\", \"Translational inhibition demonstrated only in vitro\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Placed PURA within neuronal mRNP transport granules containing Staufen, FMRP, and myosin Va in an RNA-dependent assembly associated with rough ER and a kinesin motor, defining its molecular context for dendritic transport.\",\n      \"evidence\": \"Polyribosome dissociation, co-IP with RNase controls, double-RNA IP\",\n      \"pmids\": [\"12147688\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus RNA-bridged contacts within the mRNP not dissected\", \"Functional consequence for translation at dendrites not measured\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Established PURA's essential in vivo role in nervous-system development, showing knockout mice die postnatally with neuronal proliferation, lamination, and myelination defects and loss of Cdk5 from Purkinje dendrites.\",\n      \"evidence\": \"Targeted gene knockout with histological markers and co-IP from brain lysates\",\n      \"pmids\": [\"12972605\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which molecular activity (transcription, transport, unwinding) underlies the phenotype not isolated\", \"Cell-autonomy of the defects not resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Refined PURA's cell-cycle role mechanistically, showing it binds and stimulates cyclin A/Cdk2 kinase activity and co-occupies the c-MYC promoter with Cdk2, connecting its transcriptional and kinase-regulatory functions.\",\n      \"evidence\": \"GST pull-down with CDKs, in vitro kinase assay, double ChIP in HeLa cells\",\n      \"pmids\": [\"15707957\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Net effect on c-MYC expression not quantified\", \"Specificity of CDK stimulation in vivo not tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Detailed the strand-specific unwinding mechanism, showing PURA holds the purine-rich strand while displacing the pyrimidine-rich strand and requires arginine/aromatic and C-terminal residues, advancing the structural logic of its DNA action.\",\n      \"evidence\": \"Strand-displacement, permanganate probing, gp32 accessibility, and mutational analysis\",\n      \"pmids\": [\"15777841\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genomic loci unwound in cells not mapped\", \"Coupling of unwinding to transcriptional output not established\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Linked PURA to repeat-expansion neurodegeneration, showing it binds rCGG repeats, is sequestered in FXTAS patient inclusions, and dose-dependently rescues rCGG toxicity in Drosophila, defining a sequestration-based disease mechanism.\",\n      \"evidence\": \"RNA-binding assay, Drosophila genetic rescue, and patient brain immunohistochemistry\",\n      \"pmids\": [\"17698009\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which normal PURA function is lost upon sequestration not pinpointed\", \"Quantitative depletion of soluble PURA in patients not measured\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined a PURA-hnRNP-K repressor complex at the androgen receptor gene whose loss drives AR overexpression in prostate cancer, exemplifying PURA's transcriptional-repressor role and its epigenetic regulation.\",\n      \"evidence\": \"ChIP, co-IP, siRNA/overexpression, and pharmacological HDAC/methylation inhibitor treatment\",\n      \"pmids\": [\"18413735\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism causing PURA nuclear exclusion in cancer not fully defined\", \"Direct repressive mechanism at chromatin not dissected\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Provided the first atomic-resolution view of the PUR domain, defining the Whirly-like fold, tandem PUR repeats, repeat-III-mediated dimerization, and dual beta-sheet nucleic-acid-binding surfaces.\",\n      \"evidence\": \"X-ray crystallography of Drosophila PURA, SAXS, SEC, and DNA/RNA binding with mutagenesis\",\n      \"pmids\": [\"19846792\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure lacked bound nucleic acid\", \"Full-length and human protein architecture not resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed that RNA binding and dimerization are jointly required for nuclear export and cytoplasmic transport of PURA-mRNP complexes, mechanistically coupling the structural features to its transport function.\",\n      \"evidence\": \"GFP-fusion localization in Drosophila oogenesis, co-purification MS, RNA-binding and mutant analysis\",\n      \"pmids\": [\"22614836\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian relevance of the oogenesis transport pathway not established\", \"Export receptor not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved how PURA recognizes ssDNA and unwinds duplex, identifying an essential phenylalanine required for both unwinding and neuroprotection, and explained the structural basis of 5q31.3-syndrome point mutations.\",\n      \"evidence\": \"Co-crystal structure with ssDNA, NMR, in vitro unwinding assay, mutagenesis, and Drosophila in vivo assay\",\n      \"pmids\": [\"26744780\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo unwinding substrates in mammalian neurons not identified\", \"Genotype-phenotype map across patient mutations incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected PURA to ALS pathology, showing it interacts with FUS, is recruited to stress granules, is required for SG formation, and suppresses mutant FUS mislocalization and toxicity, defining a stress-granule regulatory role.\",\n      \"evidence\": \"Co-IP, immunofluorescence co-localization, shRNA knockdown with SG quantification, and overexpression toxicity rescue in motor neurons\",\n      \"pmids\": [\"26728149\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PURA acts as a scaffold or signaling component of SGs not resolved\", \"Direct versus indirect FUS contact not mapped at residue level\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified DUSP8-mediated dephosphorylation as a signal-controlled switch driving PURA nuclear export and de-repression of the IL-9 promoter, providing a post-translational mechanism governing PURA's repressor activity in T cells.\",\n      \"evidence\": \"T cell conditional knockout, mass spectrometry, ChIP-Seq, co-IP, phosphorylation and reporter assays, and an allergic asthma model\",\n      \"pmids\": [\"37909329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase counteracting DUSP8 not identified\", \"Generalizability of the phospho-switch to other PURA target genes not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Expanded PURA's oncogenic interactome by identifying the MEST-PURA interaction driving ERK-Snail metastatic signaling and a small molecule blocking it, while circRNA-mediated cytoplasmic retention regulating promoter recruitment links RNA control to disease.\",\n      \"evidence\": \"CRISPR screen, co-IP/MS, SPR, invasion/metastasis assays; RNA pull-down/RIP/ChIP in AD models\",\n      \"pmids\": [\"37149929\", \"34504314\", \"33144099\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MEST-PURA signaling depends on PURA nucleic-acid binding not resolved\", \"Direct versus indirect effects on the named target genes not fully separated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PURA's distinct molecular activities—sequence-specific transcription, ATP-independent unwinding, and RNA transport—are partitioned and prioritized in vivo, and which activity is decisive for its neurodevelopmental essentiality, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No separation-of-function in vivo dissection linking specific activities to the knockout phenotype\", \"Genome-wide endogenous DNA/RNA target maps incomplete\", \"Physiological unwinding substrates unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 14, 22, 27, 26]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [3, 5, 12, 16, 23, 24]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [7, 8, 25, 30, 33]},\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [14, 22, 27]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [12, 19, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [10, 17, 25, 30]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [19, 28, 29]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [12, 23]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [13, 10]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [7, 8, 25, 30, 33]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [10, 11, 21]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [12, 19, 23]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [24, 28, 27]}\n    ],\n    \"complexes\": [\"dendritic transport mRNP (with Staufen/FMRP/myosin Va)\", \"PURA-hnRNP-K repressor complex\", \"cytoplasmic stress granule\"],\n    \"partners\": [\"RB1\", \"E2F1\", \"CDK2\", \"YB-1\", \"FUS\", \"HNRNPK\", \"DUSP8\", \"MEST\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}