{"gene":"PTTG1IP","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2013,"finding":"PBF/PTTG1IP is a tyrosine phosphoprotein that specifically binds the proto-oncogene tyrosine kinase Src (identified by mass spectrometry, GST pulldown, and co-immunoprecipitation). Src-mediated phosphorylation occurs at PBF residue Y174; abrogation of Y174 results in plasma membrane retention of PBF and markedly reduced ability to bind and internalize NIS (sodium iodide symporter), thereby increasing radioiodide uptake. The Src inhibitor PP1 inhibits PBF phosphorylation and restores iodide uptake in thyroid cells.","method":"Mass spectrometry, GST pulldown, co-immunoprecipitation, site-directed mutagenesis (Y174 substitution), radioiodide uptake assays in TPC1 cells and human primary thyroid cells, Src inhibitor (PP1) treatment","journal":"The Journal of clinical endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — three orthogonal biochemical methods (MS, GST pulldown, Co-IP) plus mutagenesis of the phosphorylation site with functional validation in multiple cell models","pmids":["23678037"],"is_preprint":false},{"year":2014,"finding":"PBF/PTTG1IP binds specifically to p53 in thyroid cells (shown by co-immunoprecipitation and proximity-ligation assay) and represses p53 transactivation of responsive promoters. PBF decreases p53 protein stability by enhancing its ubiquitination, an effect dependent on the E3 ligase activity of Mdm2. In transgenic PBF-overexpressing mouse thyroids, impaired p53 function was associated with significantly increased genomic instability and repression of ~40% of DNA repair genes.","method":"Co-immunoprecipitation, proximity-ligation assay, p53 transactivation reporter assays, ubiquitination assays, transgenic mouse model with thyroid-specific PBF overexpression, fluorescent ISSR-PCR for genomic instability, gene expression analysis of DNA repair genes","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus proximity-ligation assay plus functional ubiquitination and transactivation assays with in vivo transgenic validation","pmids":["24506068"],"is_preprint":false},{"year":2011,"finding":"Transgenic thyroid-specific overexpression of PBF/PTTG1IP in mice causes thyroid gland enlargement with hyperplastic and macrofollicular lesions, upregulation of Akt, TSH receptor, and cyclin D1, and potent repression of sodium iodide symporter (NIS) expression and iodide uptake. PBF depletion in primary thyroid cultures rescued iodide uptake, establishing PBF as a direct repressor of NIS-mediated radioiodide uptake.","method":"Transgenic mouse model (thyroid-specific PBF overexpression), primary thyroid culture iodide uptake assays, PBF siRNA depletion, western blotting/IHC for Akt, TSHR, cyclin D1, NIS","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo transgenic model combined with rescue experiment (PBF depletion restores iodide uptake) and mechanistic pathway markers","pmids":["21844185"],"is_preprint":false},{"year":2017,"finding":"Missense mutations C51R and R140W in PBF/PTTG1IP reduce protein stability (assessed by anisomycin half-life studies), restrict subcellular localization to the ER (C51R) or Golgi (R140W) rather than the plasma membrane, abolish the capacity to induce cellular migration and invasion, and eliminate colony formation and anchorage-independent growth. However, both mutants retain the ability to repress radioiodide uptake. Wild-type PBF transforms NIH 3T3 fibroblasts and induces tumours in nude mice.","method":"Anisomycin half-life/stability assays, subcellular localization imaging, migration and invasion assays, colony formation and soft agar assays, radioiodide uptake assays","journal":"Endocrine-related cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays on defined mutants in a single lab, but no structural validation or independent replication","pmids":["28676500"],"is_preprint":false},{"year":2024,"finding":"PTTG1IP is a small, N-glycosylated single-spanning transmembrane protein that is naturally sorted into extracellular vesicles (EVs). Its EV loading is dependent on N-glycosylation at two arginine residues. When used as a scaffold for chimeric fusion proteins (PTTG1IP fused to cargo via self-cleaving sequences), it enables highly efficient functional delivery of Cre recombinase and Cas9-sgRNA complexes to recipient cells and mouse xenograft tumors.","method":"Bioinformatics analysis of N-glycosylation as EV-sorting feature, mutagenesis of N-glycosylation sites, EV loading assays, functional delivery assays (Cre reporter, Cas9-sgRNA reporter) in cell culture and mouse xenograft","journal":"Extracellular vesicle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis of glycosylation sites with functional delivery readout in vitro and in vivo, single lab","pmids":["39712388"],"is_preprint":false},{"year":2022,"finding":"The transcription factor Sp4 binds to Sp4 response elements in the PTTG1IP promoter region (−212 to +7 bp) and drives PTTG1IP gene transcription and expression; overexpression of Sp4 increased PTTG1IP mRNA and protein levels in HeLa cells.","method":"Luciferase reporter assay (5' flanking region deletion constructs), electrophoretic mobility shift assay (EMSA), Sp4 overexpression in HeLa cells","journal":"DNA and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — EMSA plus reporter assay establish direct binding and functional transcriptional activation, but single lab, single study","pmids":["36383136"],"is_preprint":false},{"year":2025,"finding":"PTTG1IP forms an endogenous complex with cortactin (CTTN) in thyroid cancer cells, as shown by co-immunoprecipitation and co-localization by immunofluorescence. Additionally, ChIP-qPCR demonstrated that PTTG1IP occupies the promoters of DDR genes BRCA1, BRCA2, RAD51, RAD51AP1, and ATM. Depletion of PTTG1IP increased radiation-induced DNA damage and cell death, establishing a role in DNA damage response.","method":"Co-immunoprecipitation, immunofluorescence co-localization, ChIP-qPCR, shRNA knockdown, γH2AX immunofluorescence, cell viability and apoptosis assays after irradiation","journal":"Frontiers in bioscience (Landmark edition)","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP plus ChIP-qPCR plus functional irradiation assays, but single lab, single study with no independent replication","pmids":["41074439"],"is_preprint":false},{"year":2012,"finding":"A VNTR polymorphism in the PTTG1IP promoter is functional: increasing the number of tandem repeats enhances the binding affinity of estrogen receptor α (ERα) to the promoter, as shown by functional analysis, linking ERα-mediated transcriptional regulation of PTTG1IP to breast cancer risk.","method":"Genotyping of VNTR polymorphism, functional ERα binding affinity analysis (reporter/binding assay)","journal":"Cancer science","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional binding assay reported but method details are limited in abstract; single lab, single study","pmids":["22404099"],"is_preprint":false}],"current_model":"PTTG1IP/PBF is a multifunctional N-glycosylated transmembrane glycoprotein that acts as a proto-oncogene: it is phosphorylated at Y174 by Src kinase, which controls its trafficking to the plasma membrane and its ability to internalize and repress the sodium iodide symporter (NIS); it directly binds and destabilizes p53 via Mdm2-dependent ubiquitination; it forms a complex with cortactin and occupies DDR gene promoters (BRCA1, BRCA2, RAD51, ATM) to support DNA damage response; it promotes thyrocyte proliferation partly through upregulation of Akt, TSHR, and cyclin D1; its expression is transcriptionally activated by Sp4 binding to its proximal promoter and is also regulated by ERα via a VNTR in the promoter; and it is naturally sorted into extracellular vesicles in an N-glycosylation-dependent manner."},"narrative":{"mechanistic_narrative":"PTTG1IP (PBF) is an N-glycosylated single-pass transmembrane glycoprotein that functions as a proto-oncogene in thyroid and other tissues, transforming NIH 3T3 fibroblasts and inducing tumours in vivo while driving cellular migration, invasion, and anchorage-independent growth [PMID:28676500]. A central function is the direct repression of radioiodide uptake: PBF binds and internalizes the sodium iodide symporter (NIS), and thyroid-specific overexpression in mice represses NIS while enlarging the gland and upregulating Akt, the TSH receptor, and cyclin D1 [PMID:21844185]. This NIS-repressing activity is gated by Src-mediated phosphorylation at Y174, which controls PBF trafficking away from the plasma membrane; abrogating Y174 retains PBF at the membrane and restores iodide uptake, an effect mimicked by the Src inhibitor PP1 [PMID:23678037]. PBF also undermines genome integrity by binding p53 and promoting its Mdm2-dependent ubiquitination and destabilization, which in transgenic thyroids increases genomic instability and represses DNA repair genes [PMID:24506068]; conversely, PBF forms a complex with cortactin and occupies the promoters of the DDR genes BRCA1, BRCA2, RAD51, RAD51AP1, and ATM, and its depletion sensitizes cells to radiation-induced DNA damage and death [PMID:41074439]. PTTG1IP transcription is activated by Sp4 binding to its proximal promoter [PMID:36383136]. Its tumorigenic and trafficking functions depend on correct subcellular localization, as the destabilizing missense mutants C51R and R140W are retained in the ER and Golgi and lose transforming activity while retaining NIS repression [PMID:28676500]. PTTG1IP is natively sorted into extracellular vesicles in an N-glycosylation-dependent manner [PMID:39712388].","teleology":[{"year":2011,"claim":"Established PBF as a direct repressor of NIS-mediated radioiodide uptake and a thyroid proto-oncogene, addressing how PBF overexpression compromises thyroid function and growth.","evidence":"Thyroid-specific transgenic mouse overexpression with primary-culture iodide uptake rescue by PBF siRNA, plus pathway markers (Akt, TSHR, cyclin D1, NIS)","pmids":["21844185"],"confidence":"High","gaps":["Mechanism by which PBF physically engages and traffics NIS not resolved here","Whether Akt/TSHR/cyclin D1 changes are direct or downstream consequences unclear"]},{"year":2012,"claim":"Showed PTTG1IP transcription is modulated by a promoter VNTR that tunes ERα binding affinity, linking estrogen signaling to PTTG1IP expression and breast cancer risk.","evidence":"VNTR genotyping and functional ERα binding affinity analysis","pmids":["22404099"],"confidence":"Low","gaps":["Method detail limited and single study; not independently replicated","Causal link to PTTG1IP protein levels and to disease not directly demonstrated"]},{"year":2013,"claim":"Identified Src as a PBF kinase and pinpointed Y174 phosphorylation as the switch controlling PBF trafficking and its capacity to internalize NIS, explaining how iodide uptake can be pharmacologically restored.","evidence":"Mass spectrometry, GST pulldown, Co-IP, Y174 site-directed mutagenesis, and radioiodide uptake assays with PP1 in TPC1 and primary thyroid cells","pmids":["23678037"],"confidence":"High","gaps":["Structural basis of Src–PBF interaction not defined","Whether other phosphosites contribute to trafficking unknown"]},{"year":2014,"claim":"Defined a mechanism for PBF-driven genomic instability by showing it binds p53 and destabilizes it via Mdm2-dependent ubiquitination, connecting PBF overexpression to loss of DNA repair gene expression.","evidence":"Co-IP, proximity-ligation assay, transactivation reporter and ubiquitination assays, and transgenic thyroid mouse with genomic-instability and DNA-repair gene readouts","pmids":["24506068"],"confidence":"High","gaps":["Whether PBF directly recruits Mdm2 or acts indirectly not resolved","Relationship between p53 destabilization and direct promoter occupancy of DDR genes not integrated"]},{"year":2017,"claim":"Separated PBF's transforming function from its NIS-repressing function using stability/localization mutants, showing correct trafficking to the plasma membrane is required for oncogenic transformation but not for iodide-uptake repression.","evidence":"Anisomycin half-life assays, localization imaging, migration/invasion, colony and soft-agar assays, radioiodide uptake on C51R and R140W mutants; NIH 3T3 transformation and nude-mouse tumours for wild type","pmids":["28676500"],"confidence":"Medium","gaps":["No structural validation of mutant effects","Single lab, no independent replication","Molecular basis distinguishing the two functional outputs unclear"]},{"year":2022,"claim":"Identified an upstream transcriptional driver of PTTG1IP, establishing Sp4 as a direct activator binding the proximal promoter.","evidence":"Luciferase reporter deletion constructs, EMSA, and Sp4 overexpression in HeLa cells","pmids":["36383136"],"confidence":"Medium","gaps":["Single study; physiological contexts where Sp4 regulates PTTG1IP unknown","Relationship to ERα/VNTR regulation not integrated"]},{"year":2024,"claim":"Established that PTTG1IP is natively trafficked into extracellular vesicles via N-glycosylation, repurposing it as an EV-loading scaffold for functional cargo delivery.","evidence":"Bioinformatic prediction, N-glycosylation site mutagenesis, EV loading assays, and Cre/Cas9-sgRNA functional delivery in cells and mouse xenografts","pmids":["39712388"],"confidence":"Medium","gaps":["Endogenous biological role of EV sorting not defined","Single lab; mechanism of glycosylation-dependent EV partitioning unresolved"]},{"year":2025,"claim":"Linked PTTG1IP to the DNA damage response through a cortactin complex and direct occupancy of DDR gene promoters, showing its depletion sensitizes cells to radiation.","evidence":"Co-IP, immunofluorescence co-localization, ChIP-qPCR at BRCA1/BRCA2/RAD51/RAD51AP1/ATM, shRNA knockdown, γH2AX, and post-irradiation viability/apoptosis assays","pmids":["41074439"],"confidence":"Medium","gaps":["How a transmembrane protein occupies nuclear promoters mechanistically unexplained","Role of cortactin in promoter occupancy undefined","Single study without independent replication"]},{"year":null,"claim":"How PBF integrates its membrane-trafficking, NIS-internalizing, p53-destabilizing, and DDR-promoter functions into a unified molecular mechanism remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of PBF or its complexes","Mechanism reconciling cytoplasmic/membrane localization with nuclear promoter occupancy unknown","Whether p53 destabilization and direct DDR-promoter binding are sequential or parallel pathways unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,2,0]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[3]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[3]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[1,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,3]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,2]}],"complexes":[],"partners":["SRC","TP53","MDM2","CTTN","SLC5A5","SP4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P53801","full_name":"Pituitary tumor-transforming gene 1 protein-interacting protein","aliases":["Pituitary tumor-transforming gene protein-binding factor","PBF","PTTG-binding factor"],"length_aa":180,"mass_kda":20.3,"function":"May facilitate PTTG1 nuclear translocation","subcellular_location":"Membrane; Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/P53801/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PTTG1IP","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"VAMP8","stoichiometry":4.0},{"gene":"CANX","stoichiometry":0.2},{"gene":"LAMP1","stoichiometry":0.2},{"gene":"NAPA","stoichiometry":0.2},{"gene":"RAB11A","stoichiometry":0.2},{"gene":"RAB7A","stoichiometry":0.2},{"gene":"STX12","stoichiometry":0.2},{"gene":"STX6","stoichiometry":0.2},{"gene":"STX7","stoichiometry":0.2},{"gene":"STX8","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PTTG1IP","total_profiled":1310},"omim":[{"mim_id":"603784","title":"PPTG1-INTERACTING PROTEIN; PTTG1IP","url":"https://www.omim.org/entry/603784"},{"mim_id":"190685","title":"DOWN SYNDROME","url":"https://www.omim.org/entry/190685"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PTTG1IP"},"hgnc":{"alias_symbol":["PBF","PTTG1IP1"],"prev_symbol":["C21orf3","C21orf1"]},"alphafold":{"accession":"P53801","domains":[{"cath_id":"3.30.1680","chopping":"39-94","consensus_level":"medium","plddt":86.8827,"start":39,"end":94}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P53801","model_url":"https://alphafold.ebi.ac.uk/files/AF-P53801-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P53801-F1-predicted_aligned_error_v6.png","plddt_mean":77.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PTTG1IP","jax_strain_url":"https://www.jax.org/strain/search?query=PTTG1IP"},"sequence":{"accession":"P53801","fasta_url":"https://rest.uniprot.org/uniprotkb/P53801.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P53801/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P53801"}},"corpus_meta":[{"pmid":"21844185","id":"PMC_21844185","title":"Proto-oncogene PBF/PTTG1IP regulates thyroid cell growth and represses radioiodide treatment.","date":"2011","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/21844185","citation_count":40,"is_preprint":false},{"pmid":"25674221","id":"PMC_25674221","title":"MicroRNA-584 functions as a tumor suppressor and targets PTTG1IP in glioma.","date":"2014","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/25674221","citation_count":39,"is_preprint":false},{"pmid":"23678037","id":"PMC_23678037","title":"Manipulation of PBF/PTTG1IP phosphorylation status; a potential new therapeutic strategy for improving radioiodine uptake in thyroid and other tumors.","date":"2013","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/23678037","citation_count":39,"is_preprint":false},{"pmid":"24506068","id":"PMC_24506068","title":"The PTTG1-binding factor (PBF/PTTG1IP) regulates p53 activity in thyroid cells.","date":"2014","source":"Endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/24506068","citation_count":30,"is_preprint":false},{"pmid":"29078751","id":"PMC_29078751","title":"PTTG1-interacting protein (PTTG1IP/PBF) predicts breast cancer survival.","date":"2017","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/29078751","citation_count":26,"is_preprint":false},{"pmid":"34100377","id":"PMC_34100377","title":"circ-PTTG1IP/miR-671-5p/TLR4 axis regulates proliferation, migration, invasion and inflammatory response of fibroblast-like synoviocytes in rheumatoid arthritis.","date":"2021","source":"General physiology and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/34100377","citation_count":22,"is_preprint":false},{"pmid":"22404099","id":"PMC_22404099","title":"Functional variable number of tandem repeats variation in the promoter of proto-oncogene PTTG1IP is associated with risk of estrogen receptor-positive breast cancer.","date":"2012","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/22404099","citation_count":15,"is_preprint":false},{"pmid":"27709636","id":"PMC_27709636","title":"PTTG1IP and MAML3, novel genomewide association study genes for severity of hyperresponsiveness in adult asthma.","date":"2016","source":"Allergy","url":"https://pubmed.ncbi.nlm.nih.gov/27709636","citation_count":13,"is_preprint":false},{"pmid":"31423188","id":"PMC_31423188","title":"Hypermethylation of the PTTG1IP promoter leads to low expression in early-stage non-small cell lung cancer.","date":"2019","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/31423188","citation_count":9,"is_preprint":false},{"pmid":"28676500","id":"PMC_28676500","title":"Functional consequences of the first reported mutations of the proto-oncogene PTTG1IP/PBF.","date":"2017","source":"Endocrine-related cancer","url":"https://pubmed.ncbi.nlm.nih.gov/28676500","citation_count":8,"is_preprint":false},{"pmid":"39712388","id":"PMC_39712388","title":"An extracellular vesicle delivery platform based on the PTTG1IP protein.","date":"2024","source":"Extracellular vesicle","url":"https://pubmed.ncbi.nlm.nih.gov/39712388","citation_count":7,"is_preprint":false},{"pmid":"41074439","id":"PMC_41074439","title":"PTTG1IP Orchestrates Epithelial-Mesenchymal Transition and DNA Damage Response in Thyroid Cancer Progression.","date":"2025","source":"Frontiers in bioscience (Landmark edition)","url":"https://pubmed.ncbi.nlm.nih.gov/41074439","citation_count":0,"is_preprint":false},{"pmid":"36383136","id":"PMC_36383136","title":"Sp4 Regulates PTTG1IP Gene Transcription and Expression.","date":"2022","source":"DNA and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/36383136","citation_count":0,"is_preprint":false},{"pmid":"39978508","id":"PMC_39978508","title":"Molecular mechanisms of recombinant proteins PTTG1IP, ADAM12, PAPSS1, and MYO1B and their effects on wound repair induced by tendon exposure: Analysis of key genes.","date":"2025","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/39978508","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9495,"output_tokens":2558,"usd":0.033427,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9710,"output_tokens":3332,"usd":0.065925,"stage2_stop_reason":"end_turn"},"total_usd":0.099352,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"PBF/PTTG1IP is a tyrosine phosphoprotein that specifically binds the proto-oncogene tyrosine kinase Src (identified by mass spectrometry, GST pulldown, and co-immunoprecipitation). Src-mediated phosphorylation occurs at PBF residue Y174; abrogation of Y174 results in plasma membrane retention of PBF and markedly reduced ability to bind and internalize NIS (sodium iodide symporter), thereby increasing radioiodide uptake. The Src inhibitor PP1 inhibits PBF phosphorylation and restores iodide uptake in thyroid cells.\",\n      \"method\": \"Mass spectrometry, GST pulldown, co-immunoprecipitation, site-directed mutagenesis (Y174 substitution), radioiodide uptake assays in TPC1 cells and human primary thyroid cells, Src inhibitor (PP1) treatment\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — three orthogonal biochemical methods (MS, GST pulldown, Co-IP) plus mutagenesis of the phosphorylation site with functional validation in multiple cell models\",\n      \"pmids\": [\"23678037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PBF/PTTG1IP binds specifically to p53 in thyroid cells (shown by co-immunoprecipitation and proximity-ligation assay) and represses p53 transactivation of responsive promoters. PBF decreases p53 protein stability by enhancing its ubiquitination, an effect dependent on the E3 ligase activity of Mdm2. In transgenic PBF-overexpressing mouse thyroids, impaired p53 function was associated with significantly increased genomic instability and repression of ~40% of DNA repair genes.\",\n      \"method\": \"Co-immunoprecipitation, proximity-ligation assay, p53 transactivation reporter assays, ubiquitination assays, transgenic mouse model with thyroid-specific PBF overexpression, fluorescent ISSR-PCR for genomic instability, gene expression analysis of DNA repair genes\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus proximity-ligation assay plus functional ubiquitination and transactivation assays with in vivo transgenic validation\",\n      \"pmids\": [\"24506068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Transgenic thyroid-specific overexpression of PBF/PTTG1IP in mice causes thyroid gland enlargement with hyperplastic and macrofollicular lesions, upregulation of Akt, TSH receptor, and cyclin D1, and potent repression of sodium iodide symporter (NIS) expression and iodide uptake. PBF depletion in primary thyroid cultures rescued iodide uptake, establishing PBF as a direct repressor of NIS-mediated radioiodide uptake.\",\n      \"method\": \"Transgenic mouse model (thyroid-specific PBF overexpression), primary thyroid culture iodide uptake assays, PBF siRNA depletion, western blotting/IHC for Akt, TSHR, cyclin D1, NIS\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo transgenic model combined with rescue experiment (PBF depletion restores iodide uptake) and mechanistic pathway markers\",\n      \"pmids\": [\"21844185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Missense mutations C51R and R140W in PBF/PTTG1IP reduce protein stability (assessed by anisomycin half-life studies), restrict subcellular localization to the ER (C51R) or Golgi (R140W) rather than the plasma membrane, abolish the capacity to induce cellular migration and invasion, and eliminate colony formation and anchorage-independent growth. However, both mutants retain the ability to repress radioiodide uptake. Wild-type PBF transforms NIH 3T3 fibroblasts and induces tumours in nude mice.\",\n      \"method\": \"Anisomycin half-life/stability assays, subcellular localization imaging, migration and invasion assays, colony formation and soft agar assays, radioiodide uptake assays\",\n      \"journal\": \"Endocrine-related cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays on defined mutants in a single lab, but no structural validation or independent replication\",\n      \"pmids\": [\"28676500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PTTG1IP is a small, N-glycosylated single-spanning transmembrane protein that is naturally sorted into extracellular vesicles (EVs). Its EV loading is dependent on N-glycosylation at two arginine residues. When used as a scaffold for chimeric fusion proteins (PTTG1IP fused to cargo via self-cleaving sequences), it enables highly efficient functional delivery of Cre recombinase and Cas9-sgRNA complexes to recipient cells and mouse xenograft tumors.\",\n      \"method\": \"Bioinformatics analysis of N-glycosylation as EV-sorting feature, mutagenesis of N-glycosylation sites, EV loading assays, functional delivery assays (Cre reporter, Cas9-sgRNA reporter) in cell culture and mouse xenograft\",\n      \"journal\": \"Extracellular vesicle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis of glycosylation sites with functional delivery readout in vitro and in vivo, single lab\",\n      \"pmids\": [\"39712388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The transcription factor Sp4 binds to Sp4 response elements in the PTTG1IP promoter region (−212 to +7 bp) and drives PTTG1IP gene transcription and expression; overexpression of Sp4 increased PTTG1IP mRNA and protein levels in HeLa cells.\",\n      \"method\": \"Luciferase reporter assay (5' flanking region deletion constructs), electrophoretic mobility shift assay (EMSA), Sp4 overexpression in HeLa cells\",\n      \"journal\": \"DNA and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — EMSA plus reporter assay establish direct binding and functional transcriptional activation, but single lab, single study\",\n      \"pmids\": [\"36383136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PTTG1IP forms an endogenous complex with cortactin (CTTN) in thyroid cancer cells, as shown by co-immunoprecipitation and co-localization by immunofluorescence. Additionally, ChIP-qPCR demonstrated that PTTG1IP occupies the promoters of DDR genes BRCA1, BRCA2, RAD51, RAD51AP1, and ATM. Depletion of PTTG1IP increased radiation-induced DNA damage and cell death, establishing a role in DNA damage response.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, ChIP-qPCR, shRNA knockdown, γH2AX immunofluorescence, cell viability and apoptosis assays after irradiation\",\n      \"journal\": \"Frontiers in bioscience (Landmark edition)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP plus ChIP-qPCR plus functional irradiation assays, but single lab, single study with no independent replication\",\n      \"pmids\": [\"41074439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A VNTR polymorphism in the PTTG1IP promoter is functional: increasing the number of tandem repeats enhances the binding affinity of estrogen receptor α (ERα) to the promoter, as shown by functional analysis, linking ERα-mediated transcriptional regulation of PTTG1IP to breast cancer risk.\",\n      \"method\": \"Genotyping of VNTR polymorphism, functional ERα binding affinity analysis (reporter/binding assay)\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional binding assay reported but method details are limited in abstract; single lab, single study\",\n      \"pmids\": [\"22404099\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTTG1IP/PBF is a multifunctional N-glycosylated transmembrane glycoprotein that acts as a proto-oncogene: it is phosphorylated at Y174 by Src kinase, which controls its trafficking to the plasma membrane and its ability to internalize and repress the sodium iodide symporter (NIS); it directly binds and destabilizes p53 via Mdm2-dependent ubiquitination; it forms a complex with cortactin and occupies DDR gene promoters (BRCA1, BRCA2, RAD51, ATM) to support DNA damage response; it promotes thyrocyte proliferation partly through upregulation of Akt, TSHR, and cyclin D1; its expression is transcriptionally activated by Sp4 binding to its proximal promoter and is also regulated by ERα via a VNTR in the promoter; and it is naturally sorted into extracellular vesicles in an N-glycosylation-dependent manner.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTTG1IP (PBF) is an N-glycosylated single-pass transmembrane glycoprotein that functions as a proto-oncogene in thyroid and other tissues, transforming NIH 3T3 fibroblasts and inducing tumours in vivo while driving cellular migration, invasion, and anchorage-independent growth [#3]. A central function is the direct repression of radioiodide uptake: PBF binds and internalizes the sodium iodide symporter (NIS), and thyroid-specific overexpression in mice represses NIS while enlarging the gland and upregulating Akt, the TSH receptor, and cyclin D1 [#2]. This NIS-repressing activity is gated by Src-mediated phosphorylation at Y174, which controls PBF trafficking away from the plasma membrane; abrogating Y174 retains PBF at the membrane and restores iodide uptake, an effect mimicked by the Src inhibitor PP1 [#0]. PBF also undermines genome integrity by binding p53 and promoting its Mdm2-dependent ubiquitination and destabilization, which in transgenic thyroids increases genomic instability and represses DNA repair genes [#1]; conversely, PBF forms a complex with cortactin and occupies the promoters of the DDR genes BRCA1, BRCA2, RAD51, RAD51AP1, and ATM, and its depletion sensitizes cells to radiation-induced DNA damage and death [#6]. PTTG1IP transcription is activated by Sp4 binding to its proximal promoter [#5]. Its tumorigenic and trafficking functions depend on correct subcellular localization, as the destabilizing missense mutants C51R and R140W are retained in the ER and Golgi and lose transforming activity while retaining NIS repression [#3]. PTTG1IP is natively sorted into extracellular vesicles in an N-glycosylation-dependent manner [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Established PBF as a direct repressor of NIS-mediated radioiodide uptake and a thyroid proto-oncogene, addressing how PBF overexpression compromises thyroid function and growth.\",\n      \"evidence\": \"Thyroid-specific transgenic mouse overexpression with primary-culture iodide uptake rescue by PBF siRNA, plus pathway markers (Akt, TSHR, cyclin D1, NIS)\",\n      \"pmids\": [\"21844185\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PBF physically engages and traffics NIS not resolved here\", \"Whether Akt/TSHR/cyclin D1 changes are direct or downstream consequences unclear\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed PTTG1IP transcription is modulated by a promoter VNTR that tunes ERα binding affinity, linking estrogen signaling to PTTG1IP expression and breast cancer risk.\",\n      \"evidence\": \"VNTR genotyping and functional ERα binding affinity analysis\",\n      \"pmids\": [\"22404099\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Method detail limited and single study; not independently replicated\", \"Causal link to PTTG1IP protein levels and to disease not directly demonstrated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified Src as a PBF kinase and pinpointed Y174 phosphorylation as the switch controlling PBF trafficking and its capacity to internalize NIS, explaining how iodide uptake can be pharmacologically restored.\",\n      \"evidence\": \"Mass spectrometry, GST pulldown, Co-IP, Y174 site-directed mutagenesis, and radioiodide uptake assays with PP1 in TPC1 and primary thyroid cells\",\n      \"pmids\": [\"23678037\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Src–PBF interaction not defined\", \"Whether other phosphosites contribute to trafficking unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined a mechanism for PBF-driven genomic instability by showing it binds p53 and destabilizes it via Mdm2-dependent ubiquitination, connecting PBF overexpression to loss of DNA repair gene expression.\",\n      \"evidence\": \"Co-IP, proximity-ligation assay, transactivation reporter and ubiquitination assays, and transgenic thyroid mouse with genomic-instability and DNA-repair gene readouts\",\n      \"pmids\": [\"24506068\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PBF directly recruits Mdm2 or acts indirectly not resolved\", \"Relationship between p53 destabilization and direct promoter occupancy of DDR genes not integrated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Separated PBF's transforming function from its NIS-repressing function using stability/localization mutants, showing correct trafficking to the plasma membrane is required for oncogenic transformation but not for iodide-uptake repression.\",\n      \"evidence\": \"Anisomycin half-life assays, localization imaging, migration/invasion, colony and soft-agar assays, radioiodide uptake on C51R and R140W mutants; NIH 3T3 transformation and nude-mouse tumours for wild type\",\n      \"pmids\": [\"28676500\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural validation of mutant effects\", \"Single lab, no independent replication\", \"Molecular basis distinguishing the two functional outputs unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified an upstream transcriptional driver of PTTG1IP, establishing Sp4 as a direct activator binding the proximal promoter.\",\n      \"evidence\": \"Luciferase reporter deletion constructs, EMSA, and Sp4 overexpression in HeLa cells\",\n      \"pmids\": [\"36383136\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single study; physiological contexts where Sp4 regulates PTTG1IP unknown\", \"Relationship to ERα/VNTR regulation not integrated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established that PTTG1IP is natively trafficked into extracellular vesicles via N-glycosylation, repurposing it as an EV-loading scaffold for functional cargo delivery.\",\n      \"evidence\": \"Bioinformatic prediction, N-glycosylation site mutagenesis, EV loading assays, and Cre/Cas9-sgRNA functional delivery in cells and mouse xenografts\",\n      \"pmids\": [\"39712388\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous biological role of EV sorting not defined\", \"Single lab; mechanism of glycosylation-dependent EV partitioning unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked PTTG1IP to the DNA damage response through a cortactin complex and direct occupancy of DDR gene promoters, showing its depletion sensitizes cells to radiation.\",\n      \"evidence\": \"Co-IP, immunofluorescence co-localization, ChIP-qPCR at BRCA1/BRCA2/RAD51/RAD51AP1/ATM, shRNA knockdown, γH2AX, and post-irradiation viability/apoptosis assays\",\n      \"pmids\": [\"41074439\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a transmembrane protein occupies nuclear promoters mechanistically unexplained\", \"Role of cortactin in promoter occupancy undefined\", \"Single study without independent replication\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PBF integrates its membrane-trafficking, NIS-internalizing, p53-destabilizing, and DDR-promoter functions into a unified molecular mechanism remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of PBF or its complexes\", \"Mechanism reconciling cytoplasmic/membrane localization with nuclear promoter occupancy unknown\", \"Whether p53 destabilization and direct DDR-promoter binding are sequential or parallel pathways unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 2, 0]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SRC\", \"TP53\", \"MDM2\", \"CTTN\", \"SLC5A5\", \"SP4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}