{"gene":"RRM1","run_date":"2026-06-10T07:46:28","timeline":{"discoveries":[{"year":2003,"finding":"Overexpression of RRM1 in human and mouse lung cancer cell lines induced PTEN expression, reduced phosphorylation of focal adhesion kinase (FAK), and suppressed migration, invasion, and metastasis formation in an animal model. Increased PTEN expression was required for RRM1-induced suppression of cell motility and FAK phosphorylation, establishing RRM1 as a metastasis suppressor acting through induction of PTEN.","method":"Overexpression in cell lines, animal xenograft model, PTEN knockdown epistasis, FAK phosphorylation assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss-of-function (PTEN knockdown) epistasis combined with overexpression and in vivo model in a single focused study","pmids":["12687015"],"is_preprint":false},{"year":2006,"finding":"In genetically engineered lung cancer cell lines spanning a 15-fold range of RRM1 expression, gemcitabine IC50 varied ~100-fold (highest in high-RRM1 constructs), and cisplatin/carboplatin IC50 varied ~2-fold, establishing RRM1 expression level as a direct determinant of gemcitabine resistance.","method":"Genetically modified cell lines with controlled RRM1 expression range, in vitro IC50 (MTT assay)","journal":"Journal of clinical oncology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — quantitative dose-response in isogenic cell lines with engineered RRM1 range, validated in prospective clinical trial in same paper","pmids":["16966686"],"is_preprint":false},{"year":1995,"finding":"The TATA-less promoter of human RRM1 (region −195 to +3) drives maximal reporter gene expression. Electrophoretic mobility shift assays identified Sp1 as a sequence-specific binding factor in this region, established by specific competition and antibody supershift.","method":"Reporter gene transfection, EMSA, antibody supershift","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct EMSA with supershift confirmation, single lab, two orthogonal methods","pmids":["7557993"],"is_preprint":false},{"year":2015,"finding":"A single conserved tryptophan residue (W688 equivalent in mouse Rrm1) mediates RRM1 binding to RRM2; the W→G mutation abolishes this interaction (shown by proteomics). Homozygous Rrm1(WG/WG) mice are not viable even at the earliest embryonic stages, demonstrating that the RRM1–RRM2 interaction is essential for mammalian development.","method":"Mouse genetics (knock-in mutation), proteomic analysis of RRM1-binding partners, embryonic lethality phenotyping","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vivo genetic model with proteomic validation of abolished RRM1–RRM2 binding","pmids":["26077802"],"is_preprint":false},{"year":2020,"finding":"RRM1 is phosphorylated at Ser559 by CDK2/cyclin A during S/G2 phase. This phosphorylation enhances RNR enzymatic activity and is required for maintaining sufficient dNTPs during DNA replication; defective S559 phosphorylation causes DNA replication stress, double-strand breaks, and genomic instability.","method":"Cell-cycle synchronization, phospho-site identification, CDK2/cyclin A kinase assay, phospho-mutant cell lines, dNTP pool measurement, DNA damage markers (γH2AX, DSB)","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay identifying the writer (CDK2/cyclin A), phospho-mutant functional rescue, multiple orthogonal readouts (dNTP pools, DSB markers)","pmids":["32712628"],"is_preprint":false},{"year":2015,"finding":"The MEK1/2 inhibitor pimasertib reduces RRM1 protein levels via MDM2-mediated Lys48-linked polyubiquitination (proteasomal degradation), an effect partially mediated by AKT; proteasome inhibitor MG132 blocked pimasertib-induced RRM1 reduction, and immunoprecipitation confirmed enhanced MDM2–RRM1 polyubiquitination following pimasertib treatment.","method":"Immunoprecipitation of MDM2–RRM1 complex, MG132 proteasome inhibition, ubiquitin linkage analysis (Lys48), immunoblotting","journal":"Clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with ubiquitin linkage characterization plus pharmacological rescue, single lab","pmids":["26228206"],"is_preprint":false},{"year":2014,"finding":"CDK2/cyclin A-independent finding: RRM1 depletion by RNAi induces cell-cycle arrest at the replication phase, severe DNA damage, and centrosomal amplification. CHK1 depletion synergistically increased RRM1-depletion-induced centrosomal amplification; CDK1 was required for RRM1-depletion-induced centrosomal amplification, and CHK1 was delocalized from the centrosome upon RRM1 depletion with hydroxyurea treatment.","method":"RNAi-mediated depletion, immunofluorescence centrosome counting, CHK1/CDK1 knockdown epistasis, hydroxyurea-induced replication stress","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (double knockdown) with defined cellular readout, single lab","pmids":["24434653"],"is_preprint":false},{"year":2015,"finding":"RRM1 protein (independent of its ribonucleotide reductase enzymatic activity) suppresses colorectal cancer cell migration and invasion by promoting PTEN transactivation and reducing Akt phosphorylation. An enzymatically inactive RRM1 mutant (Y738F) retained this anti-metastatic activity, and PTEN knockdown blocked the effect, establishing a non-enzymatic role for RRM1 protein in PTEN-dependent signaling.","method":"Enzymatically inactive mutant (Y738F) overexpression, PTEN siRNA knockdown epistasis, migration/invasion assays, Akt phosphorylation immunoblot","journal":"Tumour biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — active-site mutagenesis separating enzymatic vs. non-enzymatic roles, epistasis with PTEN siRNA, single lab","pmids":["25638032"],"is_preprint":false},{"year":2022,"finding":"RRM1 variants cause a mitochondrial DNA maintenance disorder. A dominant catalytic-site variant (p.N427K) and homozygous recessive variants at p.R381 led to multiple mtDNA deletions in patient muscle. Patient fibroblasts showed mtDNA depletion under cycling conditions, aberrant dNTP pools, and mtDNA ribonucleotide incorporation, establishing that de novo nucleotide synthesis by RRM1 is required for mtDNA maintenance.","method":"Patient genetics, primary fibroblast mtDNA quantification, dNTP pool measurement, mtDNA ribonucleotide incorporation assay, atomistic MD simulations of variant protein structure","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple patient families, functional cell-based assays (dNTP pools, mtDNA replication), and structural modeling in one study","pmids":["35617047"],"is_preprint":false},{"year":2022,"finding":"RRM1 knockdown promotes ferroptosis in cancer cells by increasing ROS and lipid peroxidation through disruption of GPX4 activity/expression. Mechanistically, RRM1 regulates deubiquitinating enzyme USP11 and ubiquitinating enzyme MDM2 to control p53 ubiquitination; reduced p53 stability inhibits p21, which in turn restrains GPX4 expression and activity.","method":"siRNA knockdown, ROS/lipid peroxidation assays, GPX4 activity/expression measurement, ubiquitination assays for p53 (MDM2/USP11), p21 functional rescue","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple downstream readouts with mechanistic pathway dissection, single lab","pmids":["35915092"],"is_preprint":false},{"year":2024,"finding":"RRM1 promotes homologous recombination (HR) by upregulating RAD51AP1 transcription in an E2F1-dependent manner. RRM1 interacts with USP11 in the cytoplasm; ionizing radiation–induced recruitment of RRM1 to LaminB1 facilitates USP11 entry into the nucleus via the nuclear pore complex, where USP11 binds E2F1 and inhibits its ubiquitin-mediated degradation, enhancing RAD51AP1 transcription. An RRM1 truncation mutant (lacking aa 731–793) that cannot interact with USP11 or bind LaminB1 acts as a dominant negative.","method":"Co-immunoprecipitation (RRM1–USP11 interaction), deletion/truncation mutants, nuclear fractionation, ubiquitination assays for E2F1, RAD51AP1 transcription reporter, DNA repair (HR) assays, irradiation experiments","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP, domain-deletion dominant-negative, and multiple functional assays; single lab","pmids":["39695160"],"is_preprint":false},{"year":2024,"finding":"Diphthamide modification of eEF2 modulates RRM1 translation via −1 frameshifting; loss of diphthamide (DPH deficiency) dysregulates RRM1 protein levels and is causally linked to elevated DNA replication stress, shown by proteomics and functional rescue experiments.","method":"Quantitative proteomics, frameshifting reporter assay, DPH-deficient cell lines, DNA replication stress markers","journal":"ACS central science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics combined with frameshifting assay and causal rescue, single lab","pmids":["39463834"],"is_preprint":false},{"year":2021,"finding":"Cytoplasmic RRM1 is activated acutely (within 24 h) in response to gemcitabine exposure in pancreatic cancer cells; this cytoplasmic activation is related to cancer cell viability and drug resistance, whereas cells lacking cytoplasmic RRM1 activation showed severe DNA damage. RRM1 expression increase after gemcitabine could be suppressed by histone acetyltransferase inhibition.","method":"Subcellular fractionation/immunostaining of RRM1 localization, siRNA knockdown, viability assay (MTT), DNA damage markers, HAT inhibition","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct localization experiment tied to functional outcome (viability and DNA damage), siRNA epistasis, single lab","pmids":["34111175"],"is_preprint":false},{"year":2013,"finding":"A synthetic lethality kinase screen identified CHK1 as the kinase whose inhibition most robustly overcomes RRM1-dependent gemcitabine resistance. CHK1 inhibition (AZD7762) was synergistic with gemcitabine in high-RRM1 cells but antagonistic in low-RRM1 cells, and CHK1 and RRM1 protein levels were significantly and inversely correlated in 187 NSCLC patient specimens.","method":"siRNA kinase screen (87 kinases), pharmacological validation (AZD7762), synergy analysis across isogenic RRM1-high/low cell line pairs, in situ protein correlation in patient specimens","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic siRNA screen with pharmacological validation, multiple model systems, single lab","pmids":["23483975"],"is_preprint":false},{"year":2009,"finding":"RRM1 loss-of-function (siRNA knockdown) in colorectal cancer cells reduced gemcitabine IC50, and the RRM1 −37A>C promoter polymorphism was associated with RRM1 expression level and gemcitabine sensitivity (IC50) in CRC cell lines, causally linking RRM1 expression to gemcitabine resistance.","method":"siRNA knockdown, IC50 determination (MTT), genotyping of cell lines with matched expression and drug sensitivity measurement","journal":"European journal of cancer","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited mechanistic depth, primarily association with some siRNA support","pmids":["21220199"],"is_preprint":false},{"year":2014,"finding":"RRM1 in adrenocortical cancer cells (SW13) interferes with intracellular metabolism of mitotane (o,p'DDD): RRM1 silencing increased intracellular conversion of mitotane into its metabolites o,p'DDE and o,p'DDA, demonstrating that RRM1 modulates mitotane drug resistance by affecting drug metabolization rather than by a direct enzymatic mechanism.","method":"siRNA silencing of RRM1, LC-MS measurement of intracellular metabolite levels, cytotoxicity assay","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct metabolite quantification after RRM1 knockdown, two cell line models, single lab","pmids":["25497672"],"is_preprint":false},{"year":2023,"finding":"PDGFD promoter demethylation in gemcitabine-resistant pancreatic cancer cells activates STAT3 signaling (in autocrine and paracrine manner), which upregulates RRM1 expression; blocking PDGFD signaling reduced RRM1 levels and re-sensitized cells to gemcitabine in vitro and in vivo.","method":"Whole-genome bisulfite sequencing, PDGFD knockdown/inhibition, STAT3 pathway activation assays, RRM1 immunoblot, gemcitabine sensitivity assay, in vivo xenograft","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — causal chain from epigenetic change to STAT3 to RRM1 with in vivo validation, single lab","pmids":["37321532"],"is_preprint":false},{"year":2024,"finding":"YBX1 promotes RRM1 expression via the YBX1→LRP1→β-catenin→TCF3→RRM1 transcriptional axis in pancreatic cancer: YBX1 binds the LRP1 promoter to drive LRP1 transcription; LRP1 alters β-catenin concentration/distribution; β-catenin via TCF3 binds the RRM1 promoter to upregulate RRM1, thereby increasing gemcitabine resistance.","method":"ChIP (YBX1 on LRP1 promoter; TCF3/β-catenin on RRM1 promoter), β-catenin localization assay, siRNA knockdowns (pathway epistasis), gemcitabine resistance assays in vitro and in vivo","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP at multiple nodes of the pathway with epistasis rescue, in vivo confirmation, single lab","pmids":["39216548"],"is_preprint":false},{"year":2020,"finding":"Knockdown of RRM1 with siRNA in glioma cells decreased proliferation and suppressed cell cycle progression; luciferase reporter assays confirmed RRM1 as a direct target of miR-1468-5p, and forced RRM1 expression partially rescued the antiproliferative effects of miR-1468-5p overexpression.","method":"siRNA knockdown, luciferase 3'UTR reporter assay, cell proliferation (CCK-8, colony formation, EdU), flow cytometry (cell cycle), miRNA overexpression + RRM1 rescue","journal":"American journal of cancer research","confidence":"Low","confidence_rationale":"Tier 3 / Moderate — direct targeting confirmed by reporter assay, but mechanistic depth is limited to proliferation/cell cycle readout; single lab","pmids":["28469953"],"is_preprint":false},{"year":2023,"finding":"RRM1 expression regulates the extracellular matrix (ECM) remodeling gene program in pancreatic cancer; RNA-seq after RRM1 activation showed upregulation of N-cadherin, tenascin-C, and COL11A, promoting mesenchymal features and migratory/invasive potential. RRM1 expression was regulated by histone acetylation during gemcitabine resistance acquisition.","method":"RNA-seq after RRM1 modulation, histone acetylation inhibitor treatment, migration/invasion assays, immunoblotting of EMT markers","journal":"International journal of oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — transcriptomic plus functional assays but limited mechanistic dissection of how RRM1 drives ECM gene expression; single lab","pmids":["36866763"],"is_preprint":false}],"current_model":"RRM1 encodes the catalytic (large) subunit of ribonucleotide reductase (RNR), an RRM1₂–RRM2₂ heterotetramer that catalyzes the rate-limiting de novo conversion of ribonucleoside diphosphates to deoxyribonucleoside diphosphates required for DNA replication and repair; RRM1 binding to RRM2 via a conserved tryptophan residue is essential for mammalian viability, and RNR activity is finely tuned during S/G2 by CDK2/cyclin A-mediated phosphorylation of RRM1 at Ser559. Beyond its enzymatic role, RRM1 protein (independently of catalytic activity) suppresses metastasis by inducing PTEN expression and reducing FAK phosphorylation, promotes homologous recombination through a cytoplasmic RRM1–USP11–nuclear-USP11–E2F1–RAD51AP1 axis, regulates ferroptosis sensitivity via MDM2/USP11-mediated p53 ubiquitination and downstream GPX4, and maintains centrosomal integrity through CHK1/CDK1 signaling; its expression is controlled transcriptionally by Sp1, epigenetically by histone acetylation, and through the YBX1–LRP1–β-catenin–TCF3 pathway, and at the translational level by diphthamide-dependent −1 frameshifting on eEF2; elevated RRM1 is the principal molecular determinant of gemcitabine resistance, and pathogenic RRM1 loss-of-function variants impair de novo dNTP synthesis causing mitochondrial DNA depletion syndrome."},"narrative":{"mechanistic_narrative":"RRM1 is the large catalytic subunit of ribonucleotide reductase (RNR), the enzyme that supplies deoxyribonucleotides for DNA replication and repair, and its function spans both this enzymatic role and several catalytically independent regulatory activities [PMID:26077802, PMID:32712628]. Assembly of the active enzyme requires RRM1 binding to RRM2 through a single conserved tryptophan residue, an interaction essential for mammalian development [PMID:26077802]. RNR output is tuned across the cell cycle: CDK2/cyclin A phosphorylates RRM1 at Ser559 during S/G2 to boost enzymatic activity and sustain dNTP pools, and loss of this phosphorylation produces replication stress, double-strand breaks, and genomic instability [PMID:32712628]. Adequate dNTP synthesis by RRM1 is also required for mitochondrial DNA maintenance, and pathogenic catalytic-site variants (dominant p.N427K, recessive p.R381) cause a mitochondrial DNA depletion/deletion disorder with aberrant dNTP pools and mtDNA ribonucleotide incorporation [PMID:35617047]. Independent of its enzymatic activity, RRM1 acts as a metastasis suppressor by inducing PTEN expression and reducing FAK and Akt phosphorylation, an activity retained by catalytically dead mutants and abolished by PTEN knockdown [PMID:12687015, PMID:25638032]. RRM1 additionally promotes homologous recombination through a cytoplasmic interaction with USP11 that, upon irradiation, facilitates USP11 nuclear entry to stabilize E2F1 and drive RAD51AP1 transcription [PMID:39695160], and it modulates ferroptosis sensitivity by tuning USP11/MDM2-dependent p53 ubiquitination and downstream GPX4 [PMID:35915092]. RRM1 expression is transcriptionally controlled by Sp1 at its TATA-less promoter [PMID:7557993] and through STAT3- and YBX1–LRP1–β-catenin–TCF3 inputs [PMID:37321532, PMID:39216548]. Clinically, RRM1 abundance is the principal determinant of gemcitabine resistance, with isogenic cell lines showing ~100-fold IC50 shifts across the RRM1 expression range, and CHK1 inhibition selectively overcomes resistance in high-RRM1 cells [PMID:16966686, PMID:23483975].","teleology":[{"year":1995,"claim":"Established how the housekeeping RRM1 gene is transcriptionally driven, identifying Sp1 as a sequence-specific activator of its TATA-less promoter.","evidence":"Reporter transfection plus EMSA with antibody supershift on the −195/+3 promoter region","pmids":["7557993"],"confidence":"Medium","gaps":["Does not address cell-cycle or stress-responsive regulation","No in vivo confirmation of Sp1 occupancy"]},{"year":2003,"claim":"Revealed a non-canonical, enzyme-independent role for RRM1 as a metastasis suppressor acting through PTEN induction.","evidence":"Overexpression in lung cancer cell lines with xenografts, PTEN-knockdown epistasis, FAK phosphorylation readout","pmids":["12687015"],"confidence":"High","gaps":["Molecular mechanism by which RRM1 induces PTEN unresolved","Did not separate enzymatic from non-enzymatic contribution"]},{"year":2006,"claim":"Quantified RRM1 expression level as a direct, dose-dependent determinant of gemcitabine resistance, distinguishing it from platinum sensitivity.","evidence":"Isogenic cell lines spanning a 15-fold RRM1 range with in vitro IC50 measurements","pmids":["16966686"],"confidence":"High","gaps":["Mechanism limited to drug-target abundance, not regulatory control","Does not identify how to therapeutically lower RRM1"]},{"year":2009,"claim":"Causally linked an RRM1 promoter polymorphism to expression level and gemcitabine sensitivity in colorectal cancer cells.","evidence":"siRNA knockdown plus genotype/expression/IC50 correlation in CRC cell lines","pmids":["21220199"],"confidence":"Low","gaps":["Primarily associative with limited siRNA support","Mechanistic effect of the −37A>C variant on transcription not demonstrated"]},{"year":2013,"claim":"Identified CHK1 as the actionable kinase dependency that selectively reverses RRM1-driven gemcitabine resistance.","evidence":"siRNA kinase screen, AZD7762 synergy across isogenic RRM1-high/low pairs, inverse protein correlation in 187 NSCLC specimens","pmids":["23483975"],"confidence":"Medium","gaps":["Molecular basis of RRM1–CHK1 interdependence not defined","Single-lab pharmacological validation"]},{"year":2014,"claim":"Connected RRM1 to centrosomal integrity and replication-stress signaling via CHK1/CDK1.","evidence":"RNAi depletion with centrosome counting, CHK1/CDK1 knockdown epistasis, hydroxyurea-induced stress","pmids":["24434653"],"confidence":"Medium","gaps":["Whether centrosomal phenotype is enzyme-dependent or a downstream stress effect unclear","No direct RRM1 localization to centrosome shown"]},{"year":2014,"claim":"Showed RRM1 modulates mitotane resistance by altering intracellular drug metabolism rather than by its enzymatic activity.","evidence":"siRNA silencing with LC-MS metabolite quantification in adrenocortical cell lines","pmids":["25497672"],"confidence":"Medium","gaps":["Enzyme/pathway linking RRM1 to mitotane metabolism unidentified","Single tumor-type context"]},{"year":2015,"claim":"Demonstrated genetically that the RRM1–RRM2 interaction, mediated by a single conserved tryptophan, is essential for mammalian development.","evidence":"Knock-in W→G mouse, proteomic validation of lost RRM2 binding, embryonic lethality phenotyping","pmids":["26077802"],"confidence":"High","gaps":["Does not address the enzyme-independent RRM1 functions in vivo","Structural basis of the tryptophan contact not resolved here"]},{"year":2015,"claim":"Separated RRM1's anti-metastatic activity from its catalytic activity, confirming a PTEN-dependent non-enzymatic role.","evidence":"Enzymatically inactive Y738F mutant overexpression, PTEN siRNA epistasis, migration/invasion assays","pmids":["25638032"],"confidence":"Medium","gaps":["How RRM1 protein transactivates PTEN remains unknown","Single-lab, single tumor type"]},{"year":2015,"claim":"Identified MDM2-mediated K48 polyubiquitination as a route to RRM1 protein turnover downstream of MEK signaling.","evidence":"MDM2–RRM1 co-IP, ubiquitin linkage analysis, MG132 rescue after pimasertib treatment","pmids":["26228206"],"confidence":"Medium","gaps":["Whether MDM2 directly ubiquitinates RRM1 vs. via adaptor unclear","AKT involvement only partially defined"]},{"year":2020,"claim":"Defined cell-cycle control of RNR activity by identifying CDK2/cyclin A phosphorylation of RRM1 at Ser559 as a regulator of dNTP supply and genome stability.","evidence":"Phospho-site mapping, in vitro CDK2/cyclin A kinase assay, phospho-mutant cells, dNTP pool and DSB readouts","pmids":["32712628"],"confidence":"High","gaps":["Structural effect of S559 phosphorylation on the enzyme not resolved","Phosphatase reversing the mark unidentified"]},{"year":2020,"claim":"Placed RRM1 under post-transcriptional control by miR-1468-5p affecting proliferation and cell-cycle progression.","evidence":"siRNA knockdown, 3'UTR luciferase reporter, proliferation/cell-cycle assays, miRNA-plus-RRM1 rescue in glioma cells","pmids":["28469953"],"confidence":"Low","gaps":["Mechanistic depth limited to proliferation phenotype","Single-lab, single tumor type"]},{"year":2021,"claim":"Linked acute cytoplasmic RRM1 activation, controlled by histone acetylation, to gemcitabine-induced survival and avoidance of DNA damage.","evidence":"Subcellular fractionation/immunostaining, siRNA, viability and DNA damage markers, HAT inhibition in pancreatic cancer cells","pmids":["34111175"],"confidence":"Medium","gaps":["What 'cytoplasmic activation' means molecularly is undefined","Acetylated targets driving RRM1 induction not identified"]},{"year":2022,"claim":"Established RRM1 as causal for a mitochondrial DNA maintenance disorder, demonstrating that de novo dNTP synthesis by RRM1 is required for mtDNA integrity.","evidence":"Patient genetics (dominant N427K, recessive R381), fibroblast mtDNA depletion, dNTP pool and ribonucleotide incorporation assays, MD simulations","pmids":["35617047"],"confidence":"High","gaps":["Tissue-specific vulnerability of mtDNA to RRM1 deficiency not explained","Genotype–phenotype relationship across variants incomplete"]},{"year":2022,"claim":"Implicated RRM1 in ferroptosis resistance through a USP11/MDM2–p53–p21–GPX4 regulatory cascade.","evidence":"siRNA knockdown, ROS/lipid peroxidation assays, p53 ubiquitination assays, p21 rescue, GPX4 readouts","pmids":["35915092"],"confidence":"Medium","gaps":["Whether RRM1 directly binds USP11/MDM2 in this context vs. indirect not fully resolved","Single-lab pathway dissection"]},{"year":2023,"claim":"Connected epigenetic PDGFD activation and STAT3 signaling to RRM1-driven gemcitabine resistance.","evidence":"Bisulfite sequencing, PDGFD knockdown/inhibition, STAT3 activation assays, gemcitabine sensitivity in vitro and in vivo","pmids":["37321532"],"confidence":"Medium","gaps":["Whether STAT3 binds the RRM1 promoter directly not shown","Single-lab"]},{"year":2023,"claim":"Linked RRM1 expression to an ECM-remodeling/EMT transcriptional program under histone-acetylation control.","evidence":"RNA-seq after RRM1 modulation, HAT inhibition, EMT marker immunoblot, migration/invasion assays","pmids":["36866763"],"confidence":"Low","gaps":["How RRM1 drives ECM gene expression mechanistically undefined","Correlative transcriptomics"]},{"year":2024,"claim":"Defined a cytoplasm-to-nucleus signaling role for RRM1 in homologous recombination via USP11 shuttling, E2F1 stabilization, and RAD51AP1 induction.","evidence":"Reciprocal co-IP, truncation/dominant-negative mutants, nuclear fractionation, E2F1 ubiquitination, RAD51AP1 reporter, HR and irradiation assays","pmids":["39695160"],"confidence":"Medium","gaps":["Whether this role requires RNR catalytic activity not tested","Single-lab"]},{"year":2024,"claim":"Identified translational control of RRM1 via diphthamide-dependent −1 frameshifting on eEF2, linking translation fidelity to replication stress.","evidence":"Quantitative proteomics, frameshifting reporter, DPH-deficient cells, replication stress markers","pmids":["39463834"],"confidence":"Medium","gaps":["Quantitative contribution of frameshifting to physiological RRM1 levels unclear","Single-lab"]},{"year":2024,"claim":"Mapped a multilevel transcriptional axis (YBX1→LRP1→β-catenin→TCF3) driving RRM1 expression and gemcitabine resistance.","evidence":"ChIP at multiple nodes, β-catenin localization, siRNA epistasis, gemcitabine assays in vitro and in vivo","pmids":["39216548"],"confidence":"Medium","gaps":["Direct vs. cooperative TCF3/β-catenin occupancy of RRM1 promoter not fully dissected","Single-lab"]},{"year":null,"claim":"How RRM1's enzyme-independent activities (PTEN induction, USP11 shuttling, ferroptosis control) are mechanistically coupled to or separated from its core RNR catalytic role remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model linking the catalytic core to its moonlighting protein-interaction surfaces","Whether moonlighting functions operate in vivo / at physiological RRM1 levels untested","Direct binding interfaces for PTEN regulation not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[4,8]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[4,8]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,10]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[10,12]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[10]}],"pathway":[{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[4]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[10]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[4,6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[8,1]}],"complexes":["Ribonucleotide reductase (RRM1₂–RRM2₂)"],"partners":["RRM2","USP11","MDM2","CDK2","E2F1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P23921","full_name":"Ribonucleoside-diphosphate reductase large subunit","aliases":["Ribonucleoside-diphosphate reductase subunit M1","Ribonucleotide reductase large subunit"],"length_aa":792,"mass_kda":90.1,"function":"Provides the precursors necessary for DNA synthesis. 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Chung-kuo yen cheng yen chiu","url":"https://pubmed.ncbi.nlm.nih.gov/23359225","citation_count":10,"is_preprint":false},{"pmid":"28949378","id":"PMC_28949378","title":"Expression of ERCC1, RRM1, TUBB3 in correlation with apoptosis repressor ARC, DNA mismatch repair proteins and p53 in liver metastasis of colorectal cancer.","date":"2017","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28949378","citation_count":9,"is_preprint":false},{"pmid":"33921102","id":"PMC_33921102","title":"Knockdown of RRM1 with Adenoviral shRNA Vectors to Inhibit Tumor Cell Viability and Increase Chemotherapeutic Sensitivity to Gemcitabine in Bladder Cancer Cells.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33921102","citation_count":9,"is_preprint":false},{"pmid":"29924934","id":"PMC_29924934","title":"DNA Binding Induces a Nanomechanical Switch in the RRM1 Domain of TDP-43.","date":"2018","source":"The journal of physical chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/29924934","citation_count":9,"is_preprint":false},{"pmid":"26811178","id":"PMC_26811178","title":"A randomized phase II trial of ERCC1 and RRM1 mRNA expression-based chemotherapy versus docetaxel/carboplatin in advanced non-small cell lung cancer.","date":"2016","source":"Cancer chemotherapy and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/26811178","citation_count":9,"is_preprint":false},{"pmid":"31822713","id":"PMC_31822713","title":"WGS-based telomere length analysis in Dutch family trios implicates stronger maternal inheritance and a role for RRM1 gene.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31822713","citation_count":9,"is_preprint":false},{"pmid":"26077802","id":"PMC_26077802","title":"A Single Conserved Residue Mediates Binding of the Ribonucleotide Reductase Catalytic Subunit RRM1 to RRM2 and Is Essential for Mouse Development.","date":"2015","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/26077802","citation_count":9,"is_preprint":false},{"pmid":"27335251","id":"PMC_27335251","title":"RRM1 *151A>T, RRM1 -756T>C, and RRM1 -585T>Gis associated with increased susceptibility of lung cancer in Chinese patients.","date":"2016","source":"Cancer medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27335251","citation_count":8,"is_preprint":false},{"pmid":"21715970","id":"PMC_21715970","title":"Production and characterization of a novel protease from Bacillus sp. 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TUBB3 and STMN1 Genes in Tissues of Non-small Cell Lung Cancer and its Significance in Guiding Postoperative Adjuvant Chemotherapy.","date":"2015","source":"Asian Pacific journal of cancer prevention : APJCP","url":"https://pubmed.ncbi.nlm.nih.gov/25921119","citation_count":5,"is_preprint":false},{"pmid":"25896032","id":"PMC_25896032","title":"(1)H, (15)N and (13)C chemical shift assignments of the La motif and RRM1 from human LARP6.","date":"2015","source":"Biomolecular NMR assignments","url":"https://pubmed.ncbi.nlm.nih.gov/25896032","citation_count":5,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":55578,"output_tokens":5423,"usd":0.124039,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13980,"output_tokens":5680,"usd":0.10595,"stage2_stop_reason":"end_turn"},"total_usd":0.229989,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"Overexpression of RRM1 in human and mouse lung cancer cell lines induced PTEN expression, reduced phosphorylation of focal adhesion kinase (FAK), and suppressed migration, invasion, and metastasis formation in an animal model. Increased PTEN expression was required for RRM1-induced suppression of cell motility and FAK phosphorylation, establishing RRM1 as a metastasis suppressor acting through induction of PTEN.\",\n      \"method\": \"Overexpression in cell lines, animal xenograft model, PTEN knockdown epistasis, FAK phosphorylation assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function (PTEN knockdown) epistasis combined with overexpression and in vivo model in a single focused study\",\n      \"pmids\": [\"12687015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In genetically engineered lung cancer cell lines spanning a 15-fold range of RRM1 expression, gemcitabine IC50 varied ~100-fold (highest in high-RRM1 constructs), and cisplatin/carboplatin IC50 varied ~2-fold, establishing RRM1 expression level as a direct determinant of gemcitabine resistance.\",\n      \"method\": \"Genetically modified cell lines with controlled RRM1 expression range, in vitro IC50 (MTT assay)\",\n      \"journal\": \"Journal of clinical oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — quantitative dose-response in isogenic cell lines with engineered RRM1 range, validated in prospective clinical trial in same paper\",\n      \"pmids\": [\"16966686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The TATA-less promoter of human RRM1 (region −195 to +3) drives maximal reporter gene expression. Electrophoretic mobility shift assays identified Sp1 as a sequence-specific binding factor in this region, established by specific competition and antibody supershift.\",\n      \"method\": \"Reporter gene transfection, EMSA, antibody supershift\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct EMSA with supershift confirmation, single lab, two orthogonal methods\",\n      \"pmids\": [\"7557993\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A single conserved tryptophan residue (W688 equivalent in mouse Rrm1) mediates RRM1 binding to RRM2; the W→G mutation abolishes this interaction (shown by proteomics). Homozygous Rrm1(WG/WG) mice are not viable even at the earliest embryonic stages, demonstrating that the RRM1–RRM2 interaction is essential for mammalian development.\",\n      \"method\": \"Mouse genetics (knock-in mutation), proteomic analysis of RRM1-binding partners, embryonic lethality phenotyping\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vivo genetic model with proteomic validation of abolished RRM1–RRM2 binding\",\n      \"pmids\": [\"26077802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RRM1 is phosphorylated at Ser559 by CDK2/cyclin A during S/G2 phase. This phosphorylation enhances RNR enzymatic activity and is required for maintaining sufficient dNTPs during DNA replication; defective S559 phosphorylation causes DNA replication stress, double-strand breaks, and genomic instability.\",\n      \"method\": \"Cell-cycle synchronization, phospho-site identification, CDK2/cyclin A kinase assay, phospho-mutant cell lines, dNTP pool measurement, DNA damage markers (γH2AX, DSB)\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay identifying the writer (CDK2/cyclin A), phospho-mutant functional rescue, multiple orthogonal readouts (dNTP pools, DSB markers)\",\n      \"pmids\": [\"32712628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The MEK1/2 inhibitor pimasertib reduces RRM1 protein levels via MDM2-mediated Lys48-linked polyubiquitination (proteasomal degradation), an effect partially mediated by AKT; proteasome inhibitor MG132 blocked pimasertib-induced RRM1 reduction, and immunoprecipitation confirmed enhanced MDM2–RRM1 polyubiquitination following pimasertib treatment.\",\n      \"method\": \"Immunoprecipitation of MDM2–RRM1 complex, MG132 proteasome inhibition, ubiquitin linkage analysis (Lys48), immunoblotting\",\n      \"journal\": \"Clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with ubiquitin linkage characterization plus pharmacological rescue, single lab\",\n      \"pmids\": [\"26228206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CDK2/cyclin A-independent finding: RRM1 depletion by RNAi induces cell-cycle arrest at the replication phase, severe DNA damage, and centrosomal amplification. CHK1 depletion synergistically increased RRM1-depletion-induced centrosomal amplification; CDK1 was required for RRM1-depletion-induced centrosomal amplification, and CHK1 was delocalized from the centrosome upon RRM1 depletion with hydroxyurea treatment.\",\n      \"method\": \"RNAi-mediated depletion, immunofluorescence centrosome counting, CHK1/CDK1 knockdown epistasis, hydroxyurea-induced replication stress\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (double knockdown) with defined cellular readout, single lab\",\n      \"pmids\": [\"24434653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RRM1 protein (independent of its ribonucleotide reductase enzymatic activity) suppresses colorectal cancer cell migration and invasion by promoting PTEN transactivation and reducing Akt phosphorylation. An enzymatically inactive RRM1 mutant (Y738F) retained this anti-metastatic activity, and PTEN knockdown blocked the effect, establishing a non-enzymatic role for RRM1 protein in PTEN-dependent signaling.\",\n      \"method\": \"Enzymatically inactive mutant (Y738F) overexpression, PTEN siRNA knockdown epistasis, migration/invasion assays, Akt phosphorylation immunoblot\",\n      \"journal\": \"Tumour biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — active-site mutagenesis separating enzymatic vs. non-enzymatic roles, epistasis with PTEN siRNA, single lab\",\n      \"pmids\": [\"25638032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RRM1 variants cause a mitochondrial DNA maintenance disorder. A dominant catalytic-site variant (p.N427K) and homozygous recessive variants at p.R381 led to multiple mtDNA deletions in patient muscle. Patient fibroblasts showed mtDNA depletion under cycling conditions, aberrant dNTP pools, and mtDNA ribonucleotide incorporation, establishing that de novo nucleotide synthesis by RRM1 is required for mtDNA maintenance.\",\n      \"method\": \"Patient genetics, primary fibroblast mtDNA quantification, dNTP pool measurement, mtDNA ribonucleotide incorporation assay, atomistic MD simulations of variant protein structure\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple patient families, functional cell-based assays (dNTP pools, mtDNA replication), and structural modeling in one study\",\n      \"pmids\": [\"35617047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RRM1 knockdown promotes ferroptosis in cancer cells by increasing ROS and lipid peroxidation through disruption of GPX4 activity/expression. Mechanistically, RRM1 regulates deubiquitinating enzyme USP11 and ubiquitinating enzyme MDM2 to control p53 ubiquitination; reduced p53 stability inhibits p21, which in turn restrains GPX4 expression and activity.\",\n      \"method\": \"siRNA knockdown, ROS/lipid peroxidation assays, GPX4 activity/expression measurement, ubiquitination assays for p53 (MDM2/USP11), p21 functional rescue\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple downstream readouts with mechanistic pathway dissection, single lab\",\n      \"pmids\": [\"35915092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RRM1 promotes homologous recombination (HR) by upregulating RAD51AP1 transcription in an E2F1-dependent manner. RRM1 interacts with USP11 in the cytoplasm; ionizing radiation–induced recruitment of RRM1 to LaminB1 facilitates USP11 entry into the nucleus via the nuclear pore complex, where USP11 binds E2F1 and inhibits its ubiquitin-mediated degradation, enhancing RAD51AP1 transcription. An RRM1 truncation mutant (lacking aa 731–793) that cannot interact with USP11 or bind LaminB1 acts as a dominant negative.\",\n      \"method\": \"Co-immunoprecipitation (RRM1–USP11 interaction), deletion/truncation mutants, nuclear fractionation, ubiquitination assays for E2F1, RAD51AP1 transcription reporter, DNA repair (HR) assays, irradiation experiments\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP, domain-deletion dominant-negative, and multiple functional assays; single lab\",\n      \"pmids\": [\"39695160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Diphthamide modification of eEF2 modulates RRM1 translation via −1 frameshifting; loss of diphthamide (DPH deficiency) dysregulates RRM1 protein levels and is causally linked to elevated DNA replication stress, shown by proteomics and functional rescue experiments.\",\n      \"method\": \"Quantitative proteomics, frameshifting reporter assay, DPH-deficient cell lines, DNA replication stress markers\",\n      \"journal\": \"ACS central science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics combined with frameshifting assay and causal rescue, single lab\",\n      \"pmids\": [\"39463834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cytoplasmic RRM1 is activated acutely (within 24 h) in response to gemcitabine exposure in pancreatic cancer cells; this cytoplasmic activation is related to cancer cell viability and drug resistance, whereas cells lacking cytoplasmic RRM1 activation showed severe DNA damage. RRM1 expression increase after gemcitabine could be suppressed by histone acetyltransferase inhibition.\",\n      \"method\": \"Subcellular fractionation/immunostaining of RRM1 localization, siRNA knockdown, viability assay (MTT), DNA damage markers, HAT inhibition\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct localization experiment tied to functional outcome (viability and DNA damage), siRNA epistasis, single lab\",\n      \"pmids\": [\"34111175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A synthetic lethality kinase screen identified CHK1 as the kinase whose inhibition most robustly overcomes RRM1-dependent gemcitabine resistance. CHK1 inhibition (AZD7762) was synergistic with gemcitabine in high-RRM1 cells but antagonistic in low-RRM1 cells, and CHK1 and RRM1 protein levels were significantly and inversely correlated in 187 NSCLC patient specimens.\",\n      \"method\": \"siRNA kinase screen (87 kinases), pharmacological validation (AZD7762), synergy analysis across isogenic RRM1-high/low cell line pairs, in situ protein correlation in patient specimens\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic siRNA screen with pharmacological validation, multiple model systems, single lab\",\n      \"pmids\": [\"23483975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RRM1 loss-of-function (siRNA knockdown) in colorectal cancer cells reduced gemcitabine IC50, and the RRM1 −37A>C promoter polymorphism was associated with RRM1 expression level and gemcitabine sensitivity (IC50) in CRC cell lines, causally linking RRM1 expression to gemcitabine resistance.\",\n      \"method\": \"siRNA knockdown, IC50 determination (MTT), genotyping of cell lines with matched expression and drug sensitivity measurement\",\n      \"journal\": \"European journal of cancer\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited mechanistic depth, primarily association with some siRNA support\",\n      \"pmids\": [\"21220199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RRM1 in adrenocortical cancer cells (SW13) interferes with intracellular metabolism of mitotane (o,p'DDD): RRM1 silencing increased intracellular conversion of mitotane into its metabolites o,p'DDE and o,p'DDA, demonstrating that RRM1 modulates mitotane drug resistance by affecting drug metabolization rather than by a direct enzymatic mechanism.\",\n      \"method\": \"siRNA silencing of RRM1, LC-MS measurement of intracellular metabolite levels, cytotoxicity assay\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct metabolite quantification after RRM1 knockdown, two cell line models, single lab\",\n      \"pmids\": [\"25497672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PDGFD promoter demethylation in gemcitabine-resistant pancreatic cancer cells activates STAT3 signaling (in autocrine and paracrine manner), which upregulates RRM1 expression; blocking PDGFD signaling reduced RRM1 levels and re-sensitized cells to gemcitabine in vitro and in vivo.\",\n      \"method\": \"Whole-genome bisulfite sequencing, PDGFD knockdown/inhibition, STAT3 pathway activation assays, RRM1 immunoblot, gemcitabine sensitivity assay, in vivo xenograft\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — causal chain from epigenetic change to STAT3 to RRM1 with in vivo validation, single lab\",\n      \"pmids\": [\"37321532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"YBX1 promotes RRM1 expression via the YBX1→LRP1→β-catenin→TCF3→RRM1 transcriptional axis in pancreatic cancer: YBX1 binds the LRP1 promoter to drive LRP1 transcription; LRP1 alters β-catenin concentration/distribution; β-catenin via TCF3 binds the RRM1 promoter to upregulate RRM1, thereby increasing gemcitabine resistance.\",\n      \"method\": \"ChIP (YBX1 on LRP1 promoter; TCF3/β-catenin on RRM1 promoter), β-catenin localization assay, siRNA knockdowns (pathway epistasis), gemcitabine resistance assays in vitro and in vivo\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP at multiple nodes of the pathway with epistasis rescue, in vivo confirmation, single lab\",\n      \"pmids\": [\"39216548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Knockdown of RRM1 with siRNA in glioma cells decreased proliferation and suppressed cell cycle progression; luciferase reporter assays confirmed RRM1 as a direct target of miR-1468-5p, and forced RRM1 expression partially rescued the antiproliferative effects of miR-1468-5p overexpression.\",\n      \"method\": \"siRNA knockdown, luciferase 3'UTR reporter assay, cell proliferation (CCK-8, colony formation, EdU), flow cytometry (cell cycle), miRNA overexpression + RRM1 rescue\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct targeting confirmed by reporter assay, but mechanistic depth is limited to proliferation/cell cycle readout; single lab\",\n      \"pmids\": [\"28469953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RRM1 expression regulates the extracellular matrix (ECM) remodeling gene program in pancreatic cancer; RNA-seq after RRM1 activation showed upregulation of N-cadherin, tenascin-C, and COL11A, promoting mesenchymal features and migratory/invasive potential. RRM1 expression was regulated by histone acetylation during gemcitabine resistance acquisition.\",\n      \"method\": \"RNA-seq after RRM1 modulation, histone acetylation inhibitor treatment, migration/invasion assays, immunoblotting of EMT markers\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — transcriptomic plus functional assays but limited mechanistic dissection of how RRM1 drives ECM gene expression; single lab\",\n      \"pmids\": [\"36866763\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RRM1 encodes the catalytic (large) subunit of ribonucleotide reductase (RNR), an RRM1₂–RRM2₂ heterotetramer that catalyzes the rate-limiting de novo conversion of ribonucleoside diphosphates to deoxyribonucleoside diphosphates required for DNA replication and repair; RRM1 binding to RRM2 via a conserved tryptophan residue is essential for mammalian viability, and RNR activity is finely tuned during S/G2 by CDK2/cyclin A-mediated phosphorylation of RRM1 at Ser559. Beyond its enzymatic role, RRM1 protein (independently of catalytic activity) suppresses metastasis by inducing PTEN expression and reducing FAK phosphorylation, promotes homologous recombination through a cytoplasmic RRM1–USP11–nuclear-USP11–E2F1–RAD51AP1 axis, regulates ferroptosis sensitivity via MDM2/USP11-mediated p53 ubiquitination and downstream GPX4, and maintains centrosomal integrity through CHK1/CDK1 signaling; its expression is controlled transcriptionally by Sp1, epigenetically by histone acetylation, and through the YBX1–LRP1–β-catenin–TCF3 pathway, and at the translational level by diphthamide-dependent −1 frameshifting on eEF2; elevated RRM1 is the principal molecular determinant of gemcitabine resistance, and pathogenic RRM1 loss-of-function variants impair de novo dNTP synthesis causing mitochondrial DNA depletion syndrome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RRM1 is the large catalytic subunit of ribonucleotide reductase (RNR), the enzyme that supplies deoxyribonucleotides for DNA replication and repair, and its function spans both this enzymatic role and several catalytically independent regulatory activities [#3, #4]. Assembly of the active enzyme requires RRM1 binding to RRM2 through a single conserved tryptophan residue, an interaction essential for mammalian development [#3]. RNR output is tuned across the cell cycle: CDK2/cyclin A phosphorylates RRM1 at Ser559 during S/G2 to boost enzymatic activity and sustain dNTP pools, and loss of this phosphorylation produces replication stress, double-strand breaks, and genomic instability [#4]. Adequate dNTP synthesis by RRM1 is also required for mitochondrial DNA maintenance, and pathogenic catalytic-site variants (dominant p.N427K, recessive p.R381) cause a mitochondrial DNA depletion/deletion disorder with aberrant dNTP pools and mtDNA ribonucleotide incorporation [#8]. Independent of its enzymatic activity, RRM1 acts as a metastasis suppressor by inducing PTEN expression and reducing FAK and Akt phosphorylation, an activity retained by catalytically dead mutants and abolished by PTEN knockdown [#0, #7]. RRM1 additionally promotes homologous recombination through a cytoplasmic interaction with USP11 that, upon irradiation, facilitates USP11 nuclear entry to stabilize E2F1 and drive RAD51AP1 transcription [#10], and it modulates ferroptosis sensitivity by tuning USP11/MDM2-dependent p53 ubiquitination and downstream GPX4 [#9]. RRM1 expression is transcriptionally controlled by Sp1 at its TATA-less promoter [#2] and through STAT3- and YBX1\\u2013LRP1\\u2013\\u03b2-catenin\\u2013TCF3 inputs [#16, #17]. Clinically, RRM1 abundance is the principal determinant of gemcitabine resistance, with isogenic cell lines showing ~100-fold IC50 shifts across the RRM1 expression range, and CHK1 inhibition selectively overcomes resistance in high-RRM1 cells [#1, #13].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established how the housekeeping RRM1 gene is transcriptionally driven, identifying Sp1 as a sequence-specific activator of its TATA-less promoter.\",\n      \"evidence\": \"Reporter transfection plus EMSA with antibody supershift on the \\u2212195/+3 promoter region\",\n      \"pmids\": [\"7557993\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address cell-cycle or stress-responsive regulation\", \"No in vivo confirmation of Sp1 occupancy\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Revealed a non-canonical, enzyme-independent role for RRM1 as a metastasis suppressor acting through PTEN induction.\",\n      \"evidence\": \"Overexpression in lung cancer cell lines with xenografts, PTEN-knockdown epistasis, FAK phosphorylation readout\",\n      \"pmids\": [\"12687015\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which RRM1 induces PTEN unresolved\", \"Did not separate enzymatic from non-enzymatic contribution\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Quantified RRM1 expression level as a direct, dose-dependent determinant of gemcitabine resistance, distinguishing it from platinum sensitivity.\",\n      \"evidence\": \"Isogenic cell lines spanning a 15-fold RRM1 range with in vitro IC50 measurements\",\n      \"pmids\": [\"16966686\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism limited to drug-target abundance, not regulatory control\", \"Does not identify how to therapeutically lower RRM1\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Causally linked an RRM1 promoter polymorphism to expression level and gemcitabine sensitivity in colorectal cancer cells.\",\n      \"evidence\": \"siRNA knockdown plus genotype/expression/IC50 correlation in CRC cell lines\",\n      \"pmids\": [\"21220199\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Primarily associative with limited siRNA support\", \"Mechanistic effect of the \\u221237A>C variant on transcription not demonstrated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified CHK1 as the actionable kinase dependency that selectively reverses RRM1-driven gemcitabine resistance.\",\n      \"evidence\": \"siRNA kinase screen, AZD7762 synergy across isogenic RRM1-high/low pairs, inverse protein correlation in 187 NSCLC specimens\",\n      \"pmids\": [\"23483975\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of RRM1\\u2013CHK1 interdependence not defined\", \"Single-lab pharmacological validation\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected RRM1 to centrosomal integrity and replication-stress signaling via CHK1/CDK1.\",\n      \"evidence\": \"RNAi depletion with centrosome counting, CHK1/CDK1 knockdown epistasis, hydroxyurea-induced stress\",\n      \"pmids\": [\"24434653\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether centrosomal phenotype is enzyme-dependent or a downstream stress effect unclear\", \"No direct RRM1 localization to centrosome shown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed RRM1 modulates mitotane resistance by altering intracellular drug metabolism rather than by its enzymatic activity.\",\n      \"evidence\": \"siRNA silencing with LC-MS metabolite quantification in adrenocortical cell lines\",\n      \"pmids\": [\"25497672\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Enzyme/pathway linking RRM1 to mitotane metabolism unidentified\", \"Single tumor-type context\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated genetically that the RRM1\\u2013RRM2 interaction, mediated by a single conserved tryptophan, is essential for mammalian development.\",\n      \"evidence\": \"Knock-in W\\u2192G mouse, proteomic validation of lost RRM2 binding, embryonic lethality phenotyping\",\n      \"pmids\": [\"26077802\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address the enzyme-independent RRM1 functions in vivo\", \"Structural basis of the tryptophan contact not resolved here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Separated RRM1's anti-metastatic activity from its catalytic activity, confirming a PTEN-dependent non-enzymatic role.\",\n      \"evidence\": \"Enzymatically inactive Y738F mutant overexpression, PTEN siRNA epistasis, migration/invasion assays\",\n      \"pmids\": [\"25638032\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How RRM1 protein transactivates PTEN remains unknown\", \"Single-lab, single tumor type\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified MDM2-mediated K48 polyubiquitination as a route to RRM1 protein turnover downstream of MEK signaling.\",\n      \"evidence\": \"MDM2\\u2013RRM1 co-IP, ubiquitin linkage analysis, MG132 rescue after pimasertib treatment\",\n      \"pmids\": [\"26228206\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MDM2 directly ubiquitinates RRM1 vs. via adaptor unclear\", \"AKT involvement only partially defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined cell-cycle control of RNR activity by identifying CDK2/cyclin A phosphorylation of RRM1 at Ser559 as a regulator of dNTP supply and genome stability.\",\n      \"evidence\": \"Phospho-site mapping, in vitro CDK2/cyclin A kinase assay, phospho-mutant cells, dNTP pool and DSB readouts\",\n      \"pmids\": [\"32712628\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural effect of S559 phosphorylation on the enzyme not resolved\", \"Phosphatase reversing the mark unidentified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Placed RRM1 under post-transcriptional control by miR-1468-5p affecting proliferation and cell-cycle progression.\",\n      \"evidence\": \"siRNA knockdown, 3'UTR luciferase reporter, proliferation/cell-cycle assays, miRNA-plus-RRM1 rescue in glioma cells\",\n      \"pmids\": [\"28469953\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Mechanistic depth limited to proliferation phenotype\", \"Single-lab, single tumor type\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked acute cytoplasmic RRM1 activation, controlled by histone acetylation, to gemcitabine-induced survival and avoidance of DNA damage.\",\n      \"evidence\": \"Subcellular fractionation/immunostaining, siRNA, viability and DNA damage markers, HAT inhibition in pancreatic cancer cells\",\n      \"pmids\": [\"34111175\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"What 'cytoplasmic activation' means molecularly is undefined\", \"Acetylated targets driving RRM1 induction not identified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established RRM1 as causal for a mitochondrial DNA maintenance disorder, demonstrating that de novo dNTP synthesis by RRM1 is required for mtDNA integrity.\",\n      \"evidence\": \"Patient genetics (dominant N427K, recessive R381), fibroblast mtDNA depletion, dNTP pool and ribonucleotide incorporation assays, MD simulations\",\n      \"pmids\": [\"35617047\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific vulnerability of mtDNA to RRM1 deficiency not explained\", \"Genotype\\u2013phenotype relationship across variants incomplete\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Implicated RRM1 in ferroptosis resistance through a USP11/MDM2\\u2013p53\\u2013p21\\u2013GPX4 regulatory cascade.\",\n      \"evidence\": \"siRNA knockdown, ROS/lipid peroxidation assays, p53 ubiquitination assays, p21 rescue, GPX4 readouts\",\n      \"pmids\": [\"35915092\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RRM1 directly binds USP11/MDM2 in this context vs. indirect not fully resolved\", \"Single-lab pathway dissection\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected epigenetic PDGFD activation and STAT3 signaling to RRM1-driven gemcitabine resistance.\",\n      \"evidence\": \"Bisulfite sequencing, PDGFD knockdown/inhibition, STAT3 activation assays, gemcitabine sensitivity in vitro and in vivo\",\n      \"pmids\": [\"37321532\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether STAT3 binds the RRM1 promoter directly not shown\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked RRM1 expression to an ECM-remodeling/EMT transcriptional program under histone-acetylation control.\",\n      \"evidence\": \"RNA-seq after RRM1 modulation, HAT inhibition, EMT marker immunoblot, migration/invasion assays\",\n      \"pmids\": [\"36866763\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"How RRM1 drives ECM gene expression mechanistically undefined\", \"Correlative transcriptomics\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a cytoplasm-to-nucleus signaling role for RRM1 in homologous recombination via USP11 shuttling, E2F1 stabilization, and RAD51AP1 induction.\",\n      \"evidence\": \"Reciprocal co-IP, truncation/dominant-negative mutants, nuclear fractionation, E2F1 ubiquitination, RAD51AP1 reporter, HR and irradiation assays\",\n      \"pmids\": [\"39695160\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether this role requires RNR catalytic activity not tested\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified translational control of RRM1 via diphthamide-dependent \\u22121 frameshifting on eEF2, linking translation fidelity to replication stress.\",\n      \"evidence\": \"Quantitative proteomics, frameshifting reporter, DPH-deficient cells, replication stress markers\",\n      \"pmids\": [\"39463834\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative contribution of frameshifting to physiological RRM1 levels unclear\", \"Single-lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mapped a multilevel transcriptional axis (YBX1\\u2192LRP1\\u2192\\u03b2-catenin\\u2192TCF3) driving RRM1 expression and gemcitabine resistance.\",\n      \"evidence\": \"ChIP at multiple nodes, \\u03b2-catenin localization, siRNA epistasis, gemcitabine assays in vitro and in vivo\",\n      \"pmids\": [\"39216548\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. cooperative TCF3/\\u03b2-catenin occupancy of RRM1 promoter not fully dissected\", \"Single-lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RRM1's enzyme-independent activities (PTEN induction, USP11 shuttling, ferroptosis control) are mechanistically coupled to or separated from its core RNR catalytic role remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model linking the catalytic core to its moonlighting protein-interaction surfaces\", \"Whether moonlighting functions operate in vivo / at physiological RRM1 levels untested\", \"Direct binding interfaces for PTEN regulation not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [4, 8]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [4, 8]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [10, 12]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [8, 1]}\n    ],\n    \"complexes\": [\"Ribonucleotide reductase (RRM1\\u2082\\u2013RRM2\\u2082)\"],\n    \"partners\": [\"RRM2\", \"USP11\", \"MDM2\", \"CDK2\", \"E2F1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}