{"gene":"HAPSTR1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2022,"finding":"HAPSTR1 (C16orf72) oligomerizes via perfectly conserved residues in a shared domain and binds the ubiquitin ligase HUWE1; HUWE1 is a required cofactor for HAPSTR1 to control stress signaling, and in turn HUWE1 ubiquitinates and destabilizes HAPSTR1, forming a regulatory feedback loop.","method":"Domain mutagenesis, co-immunoprecipitation, genetic epistasis (co-dependency analysis), transcriptomic perturbation data integration","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal genetic and biochemical evidence (Co-IP, mutagenesis of conserved residues, epistasis via CRISPR fitness screens) in a single rigorous study","pmids":["35776542"],"is_preprint":false},{"year":2021,"finding":"HAPSTR1/TAPR1 buffers against telomere attrition by constraining p53 levels; cells lacking TAPR1 display elevated p53 and transcriptional signatures of p53 upregulation, and this elevated p53 response is rescued by loss of p53, placing TAPR1 upstream of p53 in the telomere-erosion response.","method":"Genome-wide CRISPR screens (synthetic-sick interaction with TERT loss), nutlin-3a treatment, p53 rescue experiments","journal":"Aging cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal genome-wide CRISPR screens plus epistasis rescue experiments with p53 loss-of-function, multiple orthogonal approaches in one study","pmids":["33660365"],"is_preprint":false},{"year":2023,"finding":"HAPSTR1 is required for nuclear localization of HUWE1; loss of HAPSTR1 mislocalizes HUWE1 away from the nucleus, impairing nuclear substrate ubiquitination, cell proliferation, and modulation of p53 and NF-κB stress signaling pathways.","method":"Quantitative proteomics (unbiased), subcellular fractionation/localization imaging, HAPSTR1 knockdown/knockout with functional readouts (proliferation, p53/NF-κB signaling)","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — unbiased quantitative proteomics plus direct localization experiments with functional consequences, multiple cell lines tested","pmids":["37167062"],"is_preprint":false},{"year":2023,"finding":"HAPSTR1 interacts with BRCA1 and the RNA/DNA helicase Senataxin to facilitate their recruitment to RNA:DNA hybrids at stalled replication forks, suppressing replication-associated R-loop accumulation and maintaining genome stability; this pathway functions in parallel to PARP1/2 to suppress R-loops.","method":"Genome-wide CRISPR synthetic-lethality screen with PARP1/2 disruption, co-immunoprecipitation (HAPSTR1 with BRCA1 and Senataxin), R-loop detection, replication fork restart assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genome-wide CRISPR screen plus Co-IP plus functional R-loop and replication assays, multiple orthogonal methods in one study","pmids":["37591890"],"is_preprint":false},{"year":2024,"finding":"HAPSTR1 stability is regulated upstream by ubiquitin ligase TRIP12 (which destabilizes HAPSTR1) and deubiquitinase USP7 (which stabilizes HAPSTR1); HAPSTR1 enables nuclear localization of HUWE1 with implications for nuclear protein quality control, and Hapstr1 knockout in mice causes perinatal lethality independent of p53 status.","method":"Multiplexed proteomics, conditional knockout mice (genetic epistasis with p53 null), primary cell culture, HUWE1 localization assays","journal":"Life science alliance","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiplexed proteomics plus conditional knockout mouse model plus p53 epistasis, multiple orthogonal methods and replication of HUWE1 localization finding from prior study","pmids":["38453366"],"is_preprint":false},{"year":2024,"finding":"HAPSTR1 binds LRPPRC and PSMD14; HAPSTR1 suppresses LRPPRC ubiquitination and recruits PSMD14 to interact with LRPPRC, and LRPPRC knockdown reverses HAPSTR1-mediated effects on cellular proliferation, invasion, and migration in ovarian cancer cells.","method":"Co-immunoprecipitation, HAPSTR1 overexpression and knockdown, LRPPRC knockdown rescue experiments","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single Co-IP study from a single lab identifying novel binding partners, with partial functional rescue but limited mechanistic depth","pmids":["38643468"],"is_preprint":false}],"current_model":"HAPSTR1 is an evolutionarily conserved stress-response regulator that oligomerizes and binds the ubiquitin ligase HUWE1, directing HUWE1 to the nucleus where it ubiquitinates substrates to modulate p53, NF-κB, and protein quality control pathways; HAPSTR1 stability is itself controlled by TRIP12 (ubiquitin ligase, destabilizing) and USP7 (deubiquitinase, stabilizing), creating a tight regulatory circuit; additionally, HAPSTR1 interacts with BRCA1 and Senataxin to suppress replication-associated R-loops at stalled forks, and associates with LRPPRC and PSMD14 to regulate ubiquitination-mediated protein stability, collectively positioning HAPSTR1 as a central rheostat coordinating multiple specialized stress response programs essential for mammalian life."},"narrative":{"mechanistic_narrative":"HAPSTR1 (C16orf72/TAPR1) is an evolutionarily conserved regulator of cellular stress responses that operates principally by controlling the ubiquitin ligase HUWE1 [PMID:35776542, PMID:37167062]. HAPSTR1 oligomerizes through perfectly conserved residues and binds HUWE1, which serves as a required cofactor for HAPSTR1-dependent stress signaling; reciprocally, HUWE1 ubiquitinates and destabilizes HAPSTR1, establishing a feedback loop [PMID:35776542]. Functionally, HAPSTR1 is required for nuclear localization of HUWE1, and its loss mislocalizes HUWE1 away from the nucleus, impairing nuclear substrate ubiquitination, cell proliferation, and modulation of the p53 and NF-κB stress pathways [PMID:37167062, PMID:38453366]. Consistent with a role upstream of p53, HAPSTR1 constrains p53 levels in the telomere-erosion response [PMID:33660365], and its loss in mice causes perinatal lethality independent of p53 status [PMID:38453366]. HAPSTR1 abundance is set by an opposing pair of enzymes — the ubiquitin ligase TRIP12 destabilizes it while the deubiquitinase USP7 stabilizes it [PMID:38453366]. Beyond the HUWE1 axis, HAPSTR1 interacts with BRCA1 and the helicase Senataxin to recruit them to RNA:DNA hybrids at stalled replication forks, suppressing replication-associated R-loops in parallel to PARP1/2 [PMID:37591890], and it binds LRPPRC and PSMD14 to suppress LRPPRC ubiquitination [PMID:38643468].","teleology":[{"year":2021,"claim":"Established HAPSTR1/TAPR1 as a buffer against telomere attrition acting upstream of p53, addressing how cells restrain the p53 stress response during telomere erosion.","evidence":"Genome-wide CRISPR synthetic-sick screens with TERT loss, nutlin-3a treatment, and p53 loss-of-function rescue","pmids":["33660365"],"confidence":"High","gaps":["Did not identify the molecular mechanism by which HAPSTR1 constrains p53","No physical partner of HAPSTR1 identified in this study"]},{"year":2022,"claim":"Identified HUWE1 as the key HAPSTR1 partner and defined a reciprocal regulatory feedback loop, answering how HAPSTR1 executes stress signaling and how its own levels are controlled.","evidence":"Domain mutagenesis of conserved oligomerization residues, co-immunoprecipitation, and CRISPR co-dependency/epistasis analysis","pmids":["35776542"],"confidence":"High","gaps":["Did not define which HUWE1 substrates mediate the downstream effects","Subcellular site of the HAPSTR1–HUWE1 interaction not resolved"]},{"year":2023,"claim":"Showed HAPSTR1 is required for nuclear localization of HUWE1, providing the spatial mechanism linking HAPSTR1 to nuclear substrate ubiquitination and p53/NF-κB control.","evidence":"Unbiased quantitative proteomics, subcellular fractionation and imaging, and knockdown/knockout functional readouts across multiple cell lines","pmids":["37167062"],"confidence":"High","gaps":["Mechanism of HUWE1 nuclear import via HAPSTR1 not structurally defined","Specific nuclear substrates not enumerated"]},{"year":2023,"claim":"Revealed a HUWE1-independent genome-maintenance role, addressing how HAPSTR1 contributes to replication-fork stability.","evidence":"Genome-wide CRISPR synthetic-lethality screen with PARP1/2 disruption, Co-IP with BRCA1 and Senataxin, R-loop detection, and fork restart assays","pmids":["37591890"],"confidence":"High","gaps":["Direct versus indirect nature of the BRCA1/Senataxin interactions not fully resolved","Whether this function depends on HUWE1 not tested"]},{"year":2024,"claim":"Placed HAPSTR1 in a defined stability circuit (TRIP12/USP7) and established organismal essentiality independent of p53, clarifying the upstream control and physiological importance of HAPSTR1.","evidence":"Multiplexed proteomics, conditional Hapstr1 knockout mice with p53-null epistasis, and HUWE1 localization assays","pmids":["38453366"],"confidence":"High","gaps":["The p53-independent essential function causing perinatal lethality not identified","Conditions regulating the TRIP12/USP7 balance unknown"]},{"year":2024,"claim":"Extended the HAPSTR1 interactome to LRPPRC and PSMD14, addressing how HAPSTR1 may regulate substrate ubiquitination and tumor-cell phenotypes.","evidence":"Co-immunoprecipitation, overexpression/knockdown, and LRPPRC knockdown rescue in ovarian cancer cells","pmids":["38643468"],"confidence":"Medium","gaps":["Single Co-IP study from one lab without reciprocal validation","Direct versus indirect binding not established","Relationship to the HUWE1 axis unclear"]},{"year":null,"claim":"The molecular basis of HAPSTR1's p53-independent essential function and the full set of HUWE1 substrates it directs remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of HAPSTR1–HUWE1 or how it drives HUWE1 nuclear import","The essential developmental substrate/pathway underlying perinatal lethality not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[1,2]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,5]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,4]}],"pathway":[{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,4]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[3]}],"complexes":[],"partners":["HUWE1","TRIP12","USP7","BRCA1","SETX","LRPPRC","PSMD14"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14CZ0","full_name":"HUWE1-associated protein modifying stress responses 1","aliases":["Telomere attrition and p53 response 1 protein"],"length_aa":275,"mass_kda":30.9,"function":"Acts as a central player within a network of stress response pathways promoting cellular adaptability. The E3 ligase HUWE1 assists HAPSTR1 in controlling stress signaling and in turn, HUWE1 feeds back to promote the degradation of HAPSTR1. HAPSTR1 represents a central coordination mechanism for stress response programs (PubMed:35776542). Functions as a negative regulator of TP53/P53 in the cellular response to telomere erosion and probably also DNA damage (PubMed:33660365). May attenuate p53/TP53 activation through the E3 ubiquitin ligase HUWE1 (PubMed:33660365)","subcellular_location":"Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q14CZ0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HAPSTR1","classification":"Not Classified","n_dependent_lines":536,"n_total_lines":1208,"dependency_fraction":0.44370860927152317},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HAPSTR1","total_profiled":1310},"omim":[{"mim_id":"301145","title":"HUWE1-ASSOCIATED PROTEIN MODIFYING STRESS RESPONSES 2; HAPSTR2","url":"https://www.omim.org/entry/301145"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"bone marrow","ntpm":100.0}],"url":"https://www.proteinatlas.org/search/HAPSTR1"},"hgnc":{"alias_symbol":["FLJ41272","PRO0149","TAPR1"],"prev_symbol":["C16orf72"]},"alphafold":{"accession":"Q14CZ0","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14CZ0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14CZ0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14CZ0-F1-predicted_aligned_error_v6.png","plddt_mean":69.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HAPSTR1","jax_strain_url":"https://www.jax.org/strain/search?query=HAPSTR1"},"sequence":{"accession":"Q14CZ0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14CZ0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14CZ0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14CZ0"}},"corpus_meta":[{"pmid":"32658889","id":"PMC_32658889","title":"TaTLP1 interacts with TaPR1 to contribute to wheat defense responses to leaf rust fungus.","date":"2020","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32658889","citation_count":36,"is_preprint":false},{"pmid":"36849488","id":"PMC_36849488","title":"Characterization and functional analyses of wheat TaPR1 genes in response to stripe rust fungal infection.","date":"2023","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/36849488","citation_count":22,"is_preprint":false},{"pmid":"35776542","id":"PMC_35776542","title":"C16orf72/HAPSTR1 is a molecular rheostat in an integrated network of stress response pathways.","date":"2022","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/35776542","citation_count":20,"is_preprint":false},{"pmid":"33660365","id":"PMC_33660365","title":"A novel p53 regulator, C16ORF72/TAPR1, buffers against telomerase inhibition.","date":"2021","source":"Aging cell","url":"https://pubmed.ncbi.nlm.nih.gov/33660365","citation_count":19,"is_preprint":false},{"pmid":"37167062","id":"PMC_37167062","title":"HAPSTR1 localizes HUWE1 to the nucleus to limit stress signaling pathways.","date":"2023","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/37167062","citation_count":18,"is_preprint":false},{"pmid":"35720612","id":"PMC_35720612","title":"TaPR1 Interacts With TaTLP1 via the αIV Helix to Be Involved in Wheat Defense to Puccinia triticina Through the CAPE1 Motif.","date":"2022","source":"Frontiers in plant science","url":"https://pubmed.ncbi.nlm.nih.gov/35720612","citation_count":10,"is_preprint":false},{"pmid":"37591890","id":"PMC_37591890","title":"C16orf72/HAPSTR1/TAPR1 functions with BRCA1/Senataxin to modulate replication-associated R-loops and confer resistance to PARP disruption.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/37591890","citation_count":8,"is_preprint":false},{"pmid":"38643468","id":"PMC_38643468","title":"An LRPPRC-HAPSTR1-PSMD14 interaction regulates tumor progression in ovarian cancer.","date":"2024","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/38643468","citation_count":7,"is_preprint":false},{"pmid":"38453366","id":"PMC_38453366","title":"Tight regulation of a nuclear HAPSTR1-HUWE1 pathway essential for mammalian life.","date":"2024","source":"Life science alliance","url":"https://pubmed.ncbi.nlm.nih.gov/38453366","citation_count":2,"is_preprint":false},{"pmid":"39859355","id":"PMC_39859355","title":"Re-Examination Characterization and Screening of Stripe Rust Resistance Gene of Wheat TaPR1 Gene Family Based on the Transcriptome in Xinchun 32.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/39859355","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.11.25331310","title":"A cross-disorder analysis of CNVs finds novel loci and dose-dependent relationships of genes to psychiatric traits","date":"2025-07-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.11.25331310","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7009,"output_tokens":1688,"usd":0.023173,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8548,"output_tokens":2565,"usd":0.053433,"stage2_stop_reason":"end_turn"},"total_usd":0.076606,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2022,\n      \"finding\": \"HAPSTR1 (C16orf72) oligomerizes via perfectly conserved residues in a shared domain and binds the ubiquitin ligase HUWE1; HUWE1 is a required cofactor for HAPSTR1 to control stress signaling, and in turn HUWE1 ubiquitinates and destabilizes HAPSTR1, forming a regulatory feedback loop.\",\n      \"method\": \"Domain mutagenesis, co-immunoprecipitation, genetic epistasis (co-dependency analysis), transcriptomic perturbation data integration\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal genetic and biochemical evidence (Co-IP, mutagenesis of conserved residues, epistasis via CRISPR fitness screens) in a single rigorous study\",\n      \"pmids\": [\"35776542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HAPSTR1/TAPR1 buffers against telomere attrition by constraining p53 levels; cells lacking TAPR1 display elevated p53 and transcriptional signatures of p53 upregulation, and this elevated p53 response is rescued by loss of p53, placing TAPR1 upstream of p53 in the telomere-erosion response.\",\n      \"method\": \"Genome-wide CRISPR screens (synthetic-sick interaction with TERT loss), nutlin-3a treatment, p53 rescue experiments\",\n      \"journal\": \"Aging cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal genome-wide CRISPR screens plus epistasis rescue experiments with p53 loss-of-function, multiple orthogonal approaches in one study\",\n      \"pmids\": [\"33660365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HAPSTR1 is required for nuclear localization of HUWE1; loss of HAPSTR1 mislocalizes HUWE1 away from the nucleus, impairing nuclear substrate ubiquitination, cell proliferation, and modulation of p53 and NF-κB stress signaling pathways.\",\n      \"method\": \"Quantitative proteomics (unbiased), subcellular fractionation/localization imaging, HAPSTR1 knockdown/knockout with functional readouts (proliferation, p53/NF-κB signaling)\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — unbiased quantitative proteomics plus direct localization experiments with functional consequences, multiple cell lines tested\",\n      \"pmids\": [\"37167062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HAPSTR1 interacts with BRCA1 and the RNA/DNA helicase Senataxin to facilitate their recruitment to RNA:DNA hybrids at stalled replication forks, suppressing replication-associated R-loop accumulation and maintaining genome stability; this pathway functions in parallel to PARP1/2 to suppress R-loops.\",\n      \"method\": \"Genome-wide CRISPR synthetic-lethality screen with PARP1/2 disruption, co-immunoprecipitation (HAPSTR1 with BRCA1 and Senataxin), R-loop detection, replication fork restart assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide CRISPR screen plus Co-IP plus functional R-loop and replication assays, multiple orthogonal methods in one study\",\n      \"pmids\": [\"37591890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HAPSTR1 stability is regulated upstream by ubiquitin ligase TRIP12 (which destabilizes HAPSTR1) and deubiquitinase USP7 (which stabilizes HAPSTR1); HAPSTR1 enables nuclear localization of HUWE1 with implications for nuclear protein quality control, and Hapstr1 knockout in mice causes perinatal lethality independent of p53 status.\",\n      \"method\": \"Multiplexed proteomics, conditional knockout mice (genetic epistasis with p53 null), primary cell culture, HUWE1 localization assays\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiplexed proteomics plus conditional knockout mouse model plus p53 epistasis, multiple orthogonal methods and replication of HUWE1 localization finding from prior study\",\n      \"pmids\": [\"38453366\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HAPSTR1 binds LRPPRC and PSMD14; HAPSTR1 suppresses LRPPRC ubiquitination and recruits PSMD14 to interact with LRPPRC, and LRPPRC knockdown reverses HAPSTR1-mediated effects on cellular proliferation, invasion, and migration in ovarian cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, HAPSTR1 overexpression and knockdown, LRPPRC knockdown rescue experiments\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP study from a single lab identifying novel binding partners, with partial functional rescue but limited mechanistic depth\",\n      \"pmids\": [\"38643468\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HAPSTR1 is an evolutionarily conserved stress-response regulator that oligomerizes and binds the ubiquitin ligase HUWE1, directing HUWE1 to the nucleus where it ubiquitinates substrates to modulate p53, NF-κB, and protein quality control pathways; HAPSTR1 stability is itself controlled by TRIP12 (ubiquitin ligase, destabilizing) and USP7 (deubiquitinase, stabilizing), creating a tight regulatory circuit; additionally, HAPSTR1 interacts with BRCA1 and Senataxin to suppress replication-associated R-loops at stalled forks, and associates with LRPPRC and PSMD14 to regulate ubiquitination-mediated protein stability, collectively positioning HAPSTR1 as a central rheostat coordinating multiple specialized stress response programs essential for mammalian life.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HAPSTR1 (C16orf72/TAPR1) is an evolutionarily conserved regulator of cellular stress responses that operates principally by controlling the ubiquitin ligase HUWE1 [#0, #2]. HAPSTR1 oligomerizes through perfectly conserved residues and binds HUWE1, which serves as a required cofactor for HAPSTR1-dependent stress signaling; reciprocally, HUWE1 ubiquitinates and destabilizes HAPSTR1, establishing a feedback loop [#0]. Functionally, HAPSTR1 is required for nuclear localization of HUWE1, and its loss mislocalizes HUWE1 away from the nucleus, impairing nuclear substrate ubiquitination, cell proliferation, and modulation of the p53 and NF-\\u03baB stress pathways [#2, #4]. Consistent with a role upstream of p53, HAPSTR1 constrains p53 levels in the telomere-erosion response [#1], and its loss in mice causes perinatal lethality independent of p53 status [#4]. HAPSTR1 abundance is set by an opposing pair of enzymes \\u2014 the ubiquitin ligase TRIP12 destabilizes it while the deubiquitinase USP7 stabilizes it [#4]. Beyond the HUWE1 axis, HAPSTR1 interacts with BRCA1 and the helicase Senataxin to recruit them to RNA:DNA hybrids at stalled replication forks, suppressing replication-associated R-loops in parallel to PARP1/2 [#3], and it binds LRPPRC and PSMD14 to suppress LRPPRC ubiquitination [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2021,\n      \"claim\": \"Established HAPSTR1/TAPR1 as a buffer against telomere attrition acting upstream of p53, addressing how cells restrain the p53 stress response during telomere erosion.\",\n      \"evidence\": \"Genome-wide CRISPR synthetic-sick screens with TERT loss, nutlin-3a treatment, and p53 loss-of-function rescue\",\n      \"pmids\": [\"33660365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the molecular mechanism by which HAPSTR1 constrains p53\", \"No physical partner of HAPSTR1 identified in this study\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified HUWE1 as the key HAPSTR1 partner and defined a reciprocal regulatory feedback loop, answering how HAPSTR1 executes stress signaling and how its own levels are controlled.\",\n      \"evidence\": \"Domain mutagenesis of conserved oligomerization residues, co-immunoprecipitation, and CRISPR co-dependency/epistasis analysis\",\n      \"pmids\": [\"35776542\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which HUWE1 substrates mediate the downstream effects\", \"Subcellular site of the HAPSTR1\\u2013HUWE1 interaction not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed HAPSTR1 is required for nuclear localization of HUWE1, providing the spatial mechanism linking HAPSTR1 to nuclear substrate ubiquitination and p53/NF-\\u03baB control.\",\n      \"evidence\": \"Unbiased quantitative proteomics, subcellular fractionation and imaging, and knockdown/knockout functional readouts across multiple cell lines\",\n      \"pmids\": [\"37167062\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of HUWE1 nuclear import via HAPSTR1 not structurally defined\", \"Specific nuclear substrates not enumerated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a HUWE1-independent genome-maintenance role, addressing how HAPSTR1 contributes to replication-fork stability.\",\n      \"evidence\": \"Genome-wide CRISPR synthetic-lethality screen with PARP1/2 disruption, Co-IP with BRCA1 and Senataxin, R-loop detection, and fork restart assays\",\n      \"pmids\": [\"37591890\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct versus indirect nature of the BRCA1/Senataxin interactions not fully resolved\", \"Whether this function depends on HUWE1 not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed HAPSTR1 in a defined stability circuit (TRIP12/USP7) and established organismal essentiality independent of p53, clarifying the upstream control and physiological importance of HAPSTR1.\",\n      \"evidence\": \"Multiplexed proteomics, conditional Hapstr1 knockout mice with p53-null epistasis, and HUWE1 localization assays\",\n      \"pmids\": [\"38453366\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The p53-independent essential function causing perinatal lethality not identified\", \"Conditions regulating the TRIP12/USP7 balance unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the HAPSTR1 interactome to LRPPRC and PSMD14, addressing how HAPSTR1 may regulate substrate ubiquitination and tumor-cell phenotypes.\",\n      \"evidence\": \"Co-immunoprecipitation, overexpression/knockdown, and LRPPRC knockdown rescue in ovarian cancer cells\",\n      \"pmids\": [\"38643468\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single Co-IP study from one lab without reciprocal validation\", \"Direct versus indirect binding not established\", \"Relationship to the HUWE1 axis unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular basis of HAPSTR1's p53-independent essential function and the full set of HUWE1 substrates it directs remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of HAPSTR1\\u2013HUWE1 or how it drives HUWE1 nuclear import\", \"The essential developmental substrate/pathway underlying perinatal lethality not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"HUWE1\", \"TRIP12\", \"USP7\", \"BRCA1\", \"SETX\", \"LRPPRC\", \"PSMD14\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}