{"gene":"POLE2","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2002,"finding":"The second largest subunit of mouse DNA polymerase epsilon (DPE2/POLE2) interacts with SAP18, a polypeptide associated with the Sin3 co-repressor protein. The interaction was identified by yeast two-hybrid screening and the N-terminal region of DPE2 (amino acids 85-250) was found to be responsible for binding SAP18. This interaction recruited Sin3/HDAC to repress transcription in reporter assays, an effect inhibited by trichostatin A, indicating that DPE2 can recruit histone deacetylase to modify chromatin structure at the replication fork.","method":"Yeast two-hybrid screening, reporter plasmid assay, trichostatin A inhibition","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus functional reporter assay with domain mapping, single lab","pmids":["11872158"],"is_preprint":false},{"year":2001,"finding":"The POLE2 promoter contains a 75 bp core region within exon 1 with a critical Sp1 element and two overlapping E2F elements required for full promoter activity and serum response. E2F1 and NF-1 binding sites reside downstream from the core promoter, and POLE2 is regulated by two E2F-pocket protein complexes (one associated with Sp1, one with NF-1), establishing E2F-mediated transcriptional induction of POLE2 in response to mitogenic signals.","method":"Luciferase reporter assay, EMSA (electrophoretic mobility shift assay), DNase I footprinting","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (luciferase reporter, EMSA, DNase I footprinting) in a single focused study","pmids":["11433027"],"is_preprint":false},{"year":2022,"finding":"POLE2 knockdown in glioblastoma cells promoted ubiquitination and reduced the stability of FOXM1 transcription factor through Aurora kinase A (AURKA). Knockdown of FOXM1 reversed the pro-malignant effects of POLE2, placing POLE2 upstream of AURKA-mediated FOXM1 stabilization in GBM.","method":"Loss-of-function (shRNA knockdown), ubiquitination assay, Western blot, rescue experiment with FOXM1 knockdown","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by knockdown + rescue, ubiquitination assay, single lab","pmids":["35039475"],"is_preprint":false},{"year":2021,"finding":"POLE2 knockdown in renal cell carcinoma identified stanniocalcin 1 (STC1) as a downstream gene of POLE2, with co-immunoprecipitation and microarray analysis showing POLE2 regulates STC1 to promote RCC progression; POLE2 knockdown also inhibited p-Akt, CCND1, MAPK9, and PIK3CA protein expression.","method":"Co-immunoprecipitation, microarray, Western blot, rescue experiment, xenograft model","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus rescue experiment and microarray, single lab","pmids":["33644060"],"is_preprint":false},{"year":2023,"finding":"HDAC10 deacetylates SP1; HDAC10 knockdown elevated SP1 acetylation and reduced SP1 binding to the POLE2 promoter, leading to reduced POLE2 expression. Overexpression of SP1 or POLE2 partially reversed the effects of HDAC10 deletion on NSCLC proliferation and ferroptosis, placing HDAC10 upstream of SP1-driven POLE2 transcription.","method":"ChIP (SP1 promoter binding), Western blot (acetylation), rescue overexpression, knockdown","journal":"Pulmonary pharmacology & therapeutics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway established by chromatin binding assay, acetylation Western blot, and rescue, single lab","pmids":["37657752"],"is_preprint":false},{"year":2022,"finding":"FOXM1 transcription factor binds the POLE2 promoter and drives POLE2 expression in lung adenocarcinoma; berberine downregulated FOXM1, which in turn reduced POLE2 expression, and this mechanism was confirmed by plasmid transfection rescue experiments.","method":"Plasmid transfection (FOXM1 overexpression/knockdown), quantitative RT-PCR, Western blotting, xenograft","journal":"Frontiers in pharmacology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — transcriptional regulation supported by rescue transfection, single lab, no direct ChIP","pmids":["35173608"],"is_preprint":false},{"year":2023,"finding":"POLE2 overexpression in gastric cancer cells elevated NRF2 expression and activity, which subsequently activated GPX4 to prevent lipid peroxidation and ferroptosis; silencing NRF2 or GPX4 prevented POLE2-mediated induction of proliferation and inhibition of ferroptosis, placing POLE2 upstream of the NRF2/GPX4 anti-ferroptosis axis.","method":"Lentiviral overexpression/knockdown, ferroptosis assay, Western blot, rescue experiment (NRF2/GPX4 silencing)","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistatic rescue with NRF2/GPX4 silencing, single lab, multiple readouts","pmids":["38070189"],"is_preprint":false},{"year":2024,"finding":"POLE2 promotes CD44 protein stability in osteosarcoma cells by reducing MDM2-mediated ubiquitination and degradation of CD44; POLE2 knockdown increased CD44 ubiquitination, and CD44 knockdown inhibited the tumor-promoting effects of POLE2 overexpression, with downstream activation of Rac signaling.","method":"Ubiquitination assay, Western blot, knockdown/overexpression rescue, xenograft","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay plus epistatic rescue, single lab","pmids":["38627379"],"is_preprint":false},{"year":2024,"finding":"POLE2 silencing in colorectal carcinoma cells inactivated the Wnt/β-catenin signaling pathway; activation of Wnt/β-catenin reversed the effects of POLE2 knockdown on CRC cell proliferation, migration and invasion, placing POLE2 upstream of Wnt/β-catenin signaling.","method":"Western blot (pathway proteins), rescue activation of Wnt pathway, knockdown, xenograft","journal":"Cancer biology & therapy","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pathway placement by Western blot with Wnt pathway rescue, single lab, no direct binding evidence","pmids":["39155507"],"is_preprint":false},{"year":2025,"finding":"POLE2 functions as a general NPF-motif receptor through a shallow binding pocket near its C-terminus, with residues Y513, E520, and S522 critical for motif coordination. POLE2 binds diverse NPF-containing nuclear proteins (including WDHD1, DONSON, TTF2) with micromolar affinities; motif mutations abolished binding in cell extracts. This identifies POLE2 as a hub linking DNA replication with other processes via broad NPF-motif recognition beyond its primary role of tethering catalytic POLE to replication forks.","method":"Native holdup assay (quantitative binding), mutational analysis, AlphaFold structural prediction, proteome-scale affinity screens, cell extract binding assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — quantitative binding assay with mutagenesis and structural prediction, preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.03.17.643635"],"is_preprint":true},{"year":2024,"finding":"TTF2 binds directly to POLE2 via a specific TTF2 amino-terminal motif that recognizes POLE2, coupling the TRAIP ubiquitin ligase to DNA Polymerase ε at mitotic replication forks. This complex enables TRAIP to ubiquitylate the CDC45-MCM-GINS (CMG) helicase, triggering replisome disassembly and Mitotic DNA Synthesis (MiDAS); TTF2 also contains tandem zinc fingers that recognize phosphorylated TRAIP.","method":"Biochemical reconstitution, co-immunoprecipitation, mutational analysis (TTF2 motif), in vitro ubiquitylation assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — biochemical reconstitution with mutagenesis, preprint not yet peer-reviewed, single lab","pmids":["bio_10.1101_2024.12.01.626218"],"is_preprint":true},{"year":2025,"finding":"GINS4 physically binds to POLE2 (predicted by STRING and HDOCK databases, assessed by immunofluorescence), and GINS4 silencing inhibited POLE2 expression; POLE2 overexpression reversed GINS4 knockdown effects on proliferation, cell cycle, and ferroptosis by restoring PI3K/AKT signaling activation.","method":"Protein-protein interaction prediction (STRING/HDOCK), immunofluorescence, Western blot, rescue overexpression, xenograft","journal":"Cellular signalling","confidence":"Low","confidence_rationale":"Tier 3 / Weak — interaction primarily from computational prediction with limited direct biochemical validation, single lab","pmids":["40081544"],"is_preprint":false}],"current_model":"POLE2 (DPE2) is the non-catalytic B-subunit of human DNA polymerase epsilon that tethers the catalytic POLE subunit to replication forks, recruits the Sin3/HDAC co-repressor complex to chromatin via SAP18 interaction, serves as a general NPF-motif receptor that binds diverse nuclear proteins (WDHD1, DONSON, TTF2) through a C-terminal pocket (key residues Y513, E520, S522), and participates in mitotic replisome disassembly by enabling TTF2 to couple the TRAIP ubiquitin ligase to Polε for CMG ubiquitylation; its transcription is driven by E2F/Sp1-mediated promoter activity in response to mitogenic signals, and in cancer contexts POLE2 modulates downstream signaling through AURKA/FOXM1 stabilization, NRF2/GPX4-mediated ferroptosis resistance, and Wnt/β-catenin pathway activation."},"narrative":{"mechanistic_narrative":"POLE2 (DPE2) is the non-catalytic B-subunit of human DNA polymerase epsilon, where it tethers the catalytic POLE subunit to replication forks and functions as a general NPF-motif receptor through a shallow C-terminal pocket whose residues Y513, E520, and S522 coordinate diverse NPF-containing nuclear partners including WDHD1, DONSON, and TTF2 [PMID:bio_10.1101_2025.03.17.643635]. Through this motif-recognition activity, POLE2 acts as a hub coupling DNA replication to other replisome-associated processes: by binding the TTF2 N-terminal motif it recruits the TRAIP ubiquitin ligase to Polε at mitotic replication forks, enabling ubiquitylation of the CDC45-MCM-GINS (CMG) helicase that drives mitotic replisome disassembly and mitotic DNA synthesis [PMID:bio_10.1101_2024.12.01.626218]. Beyond replication, POLE2 recruits the Sin3/HDAC co-repressor to chromatin via an N-terminal interaction with SAP18, mediating trichostatin A-sensitive transcriptional repression at the fork [PMID:11872158]. Its own expression is induced by mitogenic signals through E2F- and Sp1-dependent promoter elements [PMID:11433027]. In cancer contexts POLE2 sits upstream of multiple proliferative and survival programs, stabilizing FOXM1 via AURKA [PMID:35039475] and supporting NRF2/GPX4-mediated ferroptosis resistance [PMID:38070189].","teleology":[{"year":2001,"claim":"Established how POLE2 expression is controlled, showing it is a mitogen-responsive gene rather than constitutively expressed, linking its production to proliferative signals.","evidence":"Luciferase reporter, EMSA, and DNase I footprinting of the POLE2 promoter identifying Sp1 and overlapping E2F elements","pmids":["11433027"],"confidence":"High","gaps":["Does not address the protein's biochemical function","In vivo relevance of individual E2F/Sp1 sites to physiological replication timing not tested"]},{"year":2002,"claim":"Identified an unexpected chromatin-modifying role for POLE2 beyond replication, showing it can couple the replication fork to transcriptional repression.","evidence":"Yeast two-hybrid screen with domain mapping (aa 85-250) plus reporter assays with trichostatin A inhibition in mouse","pmids":["11872158"],"confidence":"Medium","gaps":["No demonstration at endogenous chromatin loci","Physiological consequence of HDAC recruitment during replication unresolved","Mouse system; human validation absent"]},{"year":2024,"claim":"Defined a direct biochemical mechanism by which POLE2 couples DNA Polε to replisome disassembly, answering how the TRAIP ligase is delivered to the CMG helicase at mitosis.","evidence":"Biochemical reconstitution, co-IP, TTF2 motif mutagenesis, and in vitro ubiquitylation (preprint)","pmids":["bio_10.1101_2024.12.01.626218"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Cellular requirement for the POLE2-TTF2 interaction in MiDAS not fully established","Structural basis of the POLE2 pocket-TTF2 interface not resolved at the time"]},{"year":2025,"claim":"Generalized POLE2's partner-binding role, showing the C-terminal pocket is a broad NPF-motif receptor rather than a dedicated single-partner interface, recasting POLE2 as a replication hub.","evidence":"Native holdup quantitative binding, residue mutagenesis (Y513/E520/S522), AlphaFold prediction, and proteome-scale affinity screens (preprint)","pmids":["bio_10.1101_2025.03.17.643635"],"confidence":"Medium","gaps":["Preprint, not peer-reviewed","Functional consequences of WDHD1 and DONSON recruitment via this pocket not dissected","No experimental crystal/cryo-EM structure of the bound pocket"]},{"year":2023,"claim":"Connected POLE2 levels to a cancer survival program, placing it upstream of an anti-ferroptosis axis that sustains tumor cell proliferation.","evidence":"Lentiviral overexpression/knockdown with NRF2/GPX4 silencing rescue and ferroptosis assays in gastric cancer cells","pmids":["38070189"],"confidence":"Medium","gaps":["Molecular mechanism linking the replication subunit to NRF2 induction unknown","Correlative epistasis rather than direct biochemical coupling"]},{"year":2022,"claim":"Linked POLE2 to transcription-factor stabilization in tumors, placing it upstream of AURKA-dependent FOXM1 control of proliferation.","evidence":"shRNA knockdown, ubiquitination assay, and FOXM1-knockdown rescue in glioblastoma","pmids":["35039475"],"confidence":"Medium","gaps":["Direct physical link between POLE2 and AURKA/FOXM1 not shown","Whether effect reflects replication-stress signaling versus a moonlighting role unclear"]},{"year":null,"claim":"It remains unknown how POLE2's defined replisome/NPF-receptor biochemistry mechanistically produces the diverse oncogenic signaling outputs (FOXM1/AURKA, NRF2/GPX4, CD44/MDM2, Wnt/β-catenin, PI3K/AKT) reported in cancer models.","evidence":"","pmids":[],"confidence":"Low","gaps":["No direct biochemical bridge between the replication B-subunit function and the cytoplasmic/transcriptional signaling axes","Most cancer findings are single-lab knockdown/rescue without structural or interaction-level mechanism","Several pathway placements rest on Western blot epistasis or computational prediction only"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[9,10]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[10]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[9,10]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,1]}],"complexes":["DNA polymerase epsilon","Sin3/HDAC co-repressor complex"],"partners":["POLE","SAP18","TTF2","WDHD1","DONSON","TRAIP","GINS4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P56282","full_name":"DNA polymerase epsilon subunit 2","aliases":["DNA polymerase II subunit 2","DNA polymerase epsilon subunit B"],"length_aa":527,"mass_kda":59.5,"function":"Accessory component of the DNA polymerase epsilon complex (PubMed:10801849). Participates in DNA repair and in chromosomal DNA replication (By similarity)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P56282/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/POLE2","classification":"Common Essential","n_dependent_lines":1204,"n_total_lines":1208,"dependency_fraction":0.9966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/POLE2","total_profiled":1310},"omim":[{"mim_id":"608684","title":"NINEIN; NIN","url":"https://www.omim.org/entry/608684"},{"mim_id":"607269","title":"POLYMERASE, DNA, EPSILON-4; POLE4","url":"https://www.omim.org/entry/607269"},{"mim_id":"607267","title":"POLYMERASE, DNA, EPSILON-3; POLE3","url":"https://www.omim.org/entry/607267"},{"mim_id":"602670","title":"POLYMERASE, DNA, EPSILON-2; POLE2","url":"https://www.omim.org/entry/602670"},{"mim_id":"174762","title":"POLYMERASE, DNA, EPSILON; POLE","url":"https://www.omim.org/entry/174762"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"bone marrow","ntpm":17.3}],"url":"https://www.proteinatlas.org/search/POLE2"},"hgnc":{"alias_symbol":["DPE2"],"prev_symbol":[]},"alphafold":{"accession":"P56282","domains":[{"cath_id":"1.10.8.60","chopping":"4-78","consensus_level":"high","plddt":86.4535,"start":4,"end":78}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P56282","model_url":"https://alphafold.ebi.ac.uk/files/AF-P56282-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P56282-F1-predicted_aligned_error_v6.png","plddt_mean":93.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=POLE2","jax_strain_url":"https://www.jax.org/strain/search?query=POLE2"},"sequence":{"accession":"P56282","fasta_url":"https://rest.uniprot.org/uniprotkb/P56282.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P56282/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P56282"}},"corpus_meta":[{"pmid":"30132567","id":"PMC_30132567","title":"Knockdown of POLE2 expression suppresses lung adenocarcinoma cell malignant phenotypes in vitro.","date":"2018","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/30132567","citation_count":28,"is_preprint":false},{"pmid":"35039475","id":"PMC_35039475","title":"POLE2 facilitates the malignant phenotypes of glioblastoma through promoting AURKA-mediated stabilization of FOXM1.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35039475","citation_count":20,"is_preprint":false},{"pmid":"32831648","id":"PMC_32831648","title":"POLE2 knockdown reduce tumorigenesis in esophageal squamous cells.","date":"2020","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/32831648","citation_count":20,"is_preprint":false},{"pmid":"26006747","id":"PMC_26006747","title":"In silico analysis of family GH77 with focus on amylomaltases from borreliae and disproportionating enzymes DPE2 from plants and bacteria.","date":"2015","source":"Biochimica et biophysica 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therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/37657752","citation_count":12,"is_preprint":false},{"pmid":"33644060","id":"PMC_33644060","title":"Targeting POLE2 Creates a Novel Vulnerability in Renal Cell Carcinoma via Modulating Stanniocalcin 1.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/33644060","citation_count":12,"is_preprint":false},{"pmid":"35173608","id":"PMC_35173608","title":"Berberine Inhibits FOXM1 Dependent Transcriptional Regulation of POLE2 and Interferes With the Survival of Lung Adenocarcinoma.","date":"2022","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/35173608","citation_count":10,"is_preprint":false},{"pmid":"38070189","id":"PMC_38070189","title":"Inhibition of ferroptosis by POLE2 in gastric cancer cells involves the activation of NRF2/GPX4 pathway.","date":"2023","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38070189","citation_count":9,"is_preprint":false},{"pmid":"28576440","id":"PMC_28576440","title":"Photometric assay of maltose and maltose-forming enzyme activity by using 4-alpha-glucanotransferase (DPE2) from higher plants.","date":"2017","source":"Analytical biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/28576440","citation_count":7,"is_preprint":false},{"pmid":"38079056","id":"PMC_38079056","title":"POLE2 Regulates Apoptosis of Oral Squamous Cell Carcinoma Cells through the PI3K/AKT Signaling Pathway.","date":"2023","source":"Current medical science","url":"https://pubmed.ncbi.nlm.nih.gov/38079056","citation_count":5,"is_preprint":false},{"pmid":"39155507","id":"PMC_39155507","title":"POLE2 silencing inhibits the progression of colorectal carcinoma cells via wnt signaling axis.","date":"2024","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/39155507","citation_count":5,"is_preprint":false},{"pmid":"38627379","id":"PMC_38627379","title":"POLE2 promotes osteosarcoma progression by enhancing the stability of CD44.","date":"2024","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/38627379","citation_count":5,"is_preprint":false},{"pmid":"36335878","id":"PMC_36335878","title":"Phosphorylation of DPE2 at S786 partially regulates starch degradation.","date":"2022","source":"Plant physiology and biochemistry : PPB","url":"https://pubmed.ncbi.nlm.nih.gov/36335878","citation_count":5,"is_preprint":false},{"pmid":"37097331","id":"PMC_37097331","title":"POLE2 knockdown suppresses lymphoma progression via downregulating Wnt/β-catenin signaling pathway.","date":"2023","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37097331","citation_count":4,"is_preprint":false},{"pmid":"40081544","id":"PMC_40081544","title":"GINS4 silencing mediates hepatocellular cancer cell proliferation, cycle and ferroptosis through POLE2.","date":"2025","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/40081544","citation_count":3,"is_preprint":false},{"pmid":"37733085","id":"PMC_37733085","title":"Silencing POLE2 promotes apoptosis and inhibits proliferation of oral squamous cell carcinomas by inhibiting PI3K/AKT signaling pathway.","date":"2023","source":"Medical oncology (Northwood, London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/37733085","citation_count":1,"is_preprint":false},{"pmid":"41893924","id":"PMC_41893924","title":"Role of POLE2/GINS1-mediated AKT/mTOR pathway in RCC autophagy, proliferation, and metastasis: evidences from bioinformatic, clinical, and experimental data.","date":"2026","source":"Apoptosis : an international journal on programmed cell death","url":"https://pubmed.ncbi.nlm.nih.gov/41893924","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.17.643635","title":"The non-catalytic ε DNA polymerase subunit is an NPF motif recognition protein","date":"2025-03-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.17.643635","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.12.01.626218","title":"TTF2 drives mitotic replisome disassembly and MiDAS by coupling the TRAIP ubiquitin ligase to Polε","date":"2024-12-02","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.01.626218","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12566,"output_tokens":3164,"usd":0.042579,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10640,"output_tokens":2610,"usd":0.059225,"stage2_stop_reason":"end_turn"},"total_usd":0.101804,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"The second largest subunit of mouse DNA polymerase epsilon (DPE2/POLE2) interacts with SAP18, a polypeptide associated with the Sin3 co-repressor protein. The interaction was identified by yeast two-hybrid screening and the N-terminal region of DPE2 (amino acids 85-250) was found to be responsible for binding SAP18. This interaction recruited Sin3/HDAC to repress transcription in reporter assays, an effect inhibited by trichostatin A, indicating that DPE2 can recruit histone deacetylase to modify chromatin structure at the replication fork.\",\n      \"method\": \"Yeast two-hybrid screening, reporter plasmid assay, trichostatin A inhibition\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus functional reporter assay with domain mapping, single lab\",\n      \"pmids\": [\"11872158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The POLE2 promoter contains a 75 bp core region within exon 1 with a critical Sp1 element and two overlapping E2F elements required for full promoter activity and serum response. E2F1 and NF-1 binding sites reside downstream from the core promoter, and POLE2 is regulated by two E2F-pocket protein complexes (one associated with Sp1, one with NF-1), establishing E2F-mediated transcriptional induction of POLE2 in response to mitogenic signals.\",\n      \"method\": \"Luciferase reporter assay, EMSA (electrophoretic mobility shift assay), DNase I footprinting\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (luciferase reporter, EMSA, DNase I footprinting) in a single focused study\",\n      \"pmids\": [\"11433027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"POLE2 knockdown in glioblastoma cells promoted ubiquitination and reduced the stability of FOXM1 transcription factor through Aurora kinase A (AURKA). Knockdown of FOXM1 reversed the pro-malignant effects of POLE2, placing POLE2 upstream of AURKA-mediated FOXM1 stabilization in GBM.\",\n      \"method\": \"Loss-of-function (shRNA knockdown), ubiquitination assay, Western blot, rescue experiment with FOXM1 knockdown\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by knockdown + rescue, ubiquitination assay, single lab\",\n      \"pmids\": [\"35039475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"POLE2 knockdown in renal cell carcinoma identified stanniocalcin 1 (STC1) as a downstream gene of POLE2, with co-immunoprecipitation and microarray analysis showing POLE2 regulates STC1 to promote RCC progression; POLE2 knockdown also inhibited p-Akt, CCND1, MAPK9, and PIK3CA protein expression.\",\n      \"method\": \"Co-immunoprecipitation, microarray, Western blot, rescue experiment, xenograft model\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus rescue experiment and microarray, single lab\",\n      \"pmids\": [\"33644060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HDAC10 deacetylates SP1; HDAC10 knockdown elevated SP1 acetylation and reduced SP1 binding to the POLE2 promoter, leading to reduced POLE2 expression. Overexpression of SP1 or POLE2 partially reversed the effects of HDAC10 deletion on NSCLC proliferation and ferroptosis, placing HDAC10 upstream of SP1-driven POLE2 transcription.\",\n      \"method\": \"ChIP (SP1 promoter binding), Western blot (acetylation), rescue overexpression, knockdown\",\n      \"journal\": \"Pulmonary pharmacology & therapeutics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway established by chromatin binding assay, acetylation Western blot, and rescue, single lab\",\n      \"pmids\": [\"37657752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FOXM1 transcription factor binds the POLE2 promoter and drives POLE2 expression in lung adenocarcinoma; berberine downregulated FOXM1, which in turn reduced POLE2 expression, and this mechanism was confirmed by plasmid transfection rescue experiments.\",\n      \"method\": \"Plasmid transfection (FOXM1 overexpression/knockdown), quantitative RT-PCR, Western blotting, xenograft\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — transcriptional regulation supported by rescue transfection, single lab, no direct ChIP\",\n      \"pmids\": [\"35173608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"POLE2 overexpression in gastric cancer cells elevated NRF2 expression and activity, which subsequently activated GPX4 to prevent lipid peroxidation and ferroptosis; silencing NRF2 or GPX4 prevented POLE2-mediated induction of proliferation and inhibition of ferroptosis, placing POLE2 upstream of the NRF2/GPX4 anti-ferroptosis axis.\",\n      \"method\": \"Lentiviral overexpression/knockdown, ferroptosis assay, Western blot, rescue experiment (NRF2/GPX4 silencing)\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistatic rescue with NRF2/GPX4 silencing, single lab, multiple readouts\",\n      \"pmids\": [\"38070189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"POLE2 promotes CD44 protein stability in osteosarcoma cells by reducing MDM2-mediated ubiquitination and degradation of CD44; POLE2 knockdown increased CD44 ubiquitination, and CD44 knockdown inhibited the tumor-promoting effects of POLE2 overexpression, with downstream activation of Rac signaling.\",\n      \"method\": \"Ubiquitination assay, Western blot, knockdown/overexpression rescue, xenograft\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay plus epistatic rescue, single lab\",\n      \"pmids\": [\"38627379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"POLE2 silencing in colorectal carcinoma cells inactivated the Wnt/β-catenin signaling pathway; activation of Wnt/β-catenin reversed the effects of POLE2 knockdown on CRC cell proliferation, migration and invasion, placing POLE2 upstream of Wnt/β-catenin signaling.\",\n      \"method\": \"Western blot (pathway proteins), rescue activation of Wnt pathway, knockdown, xenograft\",\n      \"journal\": \"Cancer biology & therapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pathway placement by Western blot with Wnt pathway rescue, single lab, no direct binding evidence\",\n      \"pmids\": [\"39155507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"POLE2 functions as a general NPF-motif receptor through a shallow binding pocket near its C-terminus, with residues Y513, E520, and S522 critical for motif coordination. POLE2 binds diverse NPF-containing nuclear proteins (including WDHD1, DONSON, TTF2) with micromolar affinities; motif mutations abolished binding in cell extracts. This identifies POLE2 as a hub linking DNA replication with other processes via broad NPF-motif recognition beyond its primary role of tethering catalytic POLE to replication forks.\",\n      \"method\": \"Native holdup assay (quantitative binding), mutational analysis, AlphaFold structural prediction, proteome-scale affinity screens, cell extract binding assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — quantitative binding assay with mutagenesis and structural prediction, preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.03.17.643635\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TTF2 binds directly to POLE2 via a specific TTF2 amino-terminal motif that recognizes POLE2, coupling the TRAIP ubiquitin ligase to DNA Polymerase ε at mitotic replication forks. This complex enables TRAIP to ubiquitylate the CDC45-MCM-GINS (CMG) helicase, triggering replisome disassembly and Mitotic DNA Synthesis (MiDAS); TTF2 also contains tandem zinc fingers that recognize phosphorylated TRAIP.\",\n      \"method\": \"Biochemical reconstitution, co-immunoprecipitation, mutational analysis (TTF2 motif), in vitro ubiquitylation assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — biochemical reconstitution with mutagenesis, preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [\"bio_10.1101_2024.12.01.626218\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GINS4 physically binds to POLE2 (predicted by STRING and HDOCK databases, assessed by immunofluorescence), and GINS4 silencing inhibited POLE2 expression; POLE2 overexpression reversed GINS4 knockdown effects on proliferation, cell cycle, and ferroptosis by restoring PI3K/AKT signaling activation.\",\n      \"method\": \"Protein-protein interaction prediction (STRING/HDOCK), immunofluorescence, Western blot, rescue overexpression, xenograft\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — interaction primarily from computational prediction with limited direct biochemical validation, single lab\",\n      \"pmids\": [\"40081544\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"POLE2 (DPE2) is the non-catalytic B-subunit of human DNA polymerase epsilon that tethers the catalytic POLE subunit to replication forks, recruits the Sin3/HDAC co-repressor complex to chromatin via SAP18 interaction, serves as a general NPF-motif receptor that binds diverse nuclear proteins (WDHD1, DONSON, TTF2) through a C-terminal pocket (key residues Y513, E520, S522), and participates in mitotic replisome disassembly by enabling TTF2 to couple the TRAIP ubiquitin ligase to Polε for CMG ubiquitylation; its transcription is driven by E2F/Sp1-mediated promoter activity in response to mitogenic signals, and in cancer contexts POLE2 modulates downstream signaling through AURKA/FOXM1 stabilization, NRF2/GPX4-mediated ferroptosis resistance, and Wnt/β-catenin pathway activation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"POLE2 (DPE2) is the non-catalytic B-subunit of human DNA polymerase epsilon, where it tethers the catalytic POLE subunit to replication forks and functions as a general NPF-motif receptor through a shallow C-terminal pocket whose residues Y513, E520, and S522 coordinate diverse NPF-containing nuclear partners including WDHD1, DONSON, and TTF2 [#9]. Through this motif-recognition activity, POLE2 acts as a hub coupling DNA replication to other replisome-associated processes: by binding the TTF2 N-terminal motif it recruits the TRAIP ubiquitin ligase to Pol\\u03b5 at mitotic replication forks, enabling ubiquitylation of the CDC45-MCM-GINS (CMG) helicase that drives mitotic replisome disassembly and mitotic DNA synthesis [#10]. Beyond replication, POLE2 recruits the Sin3/HDAC co-repressor to chromatin via an N-terminal interaction with SAP18, mediating trichostatin A-sensitive transcriptional repression at the fork [#0]. Its own expression is induced by mitogenic signals through E2F- and Sp1-dependent promoter elements [#1]. In cancer contexts POLE2 sits upstream of multiple proliferative and survival programs, stabilizing FOXM1 via AURKA [#2] and supporting NRF2/GPX4-mediated ferroptosis resistance [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established how POLE2 expression is controlled, showing it is a mitogen-responsive gene rather than constitutively expressed, linking its production to proliferative signals.\",\n      \"evidence\": \"Luciferase reporter, EMSA, and DNase I footprinting of the POLE2 promoter identifying Sp1 and overlapping E2F elements\",\n      \"pmids\": [\"11433027\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address the protein's biochemical function\", \"In vivo relevance of individual E2F/Sp1 sites to physiological replication timing not tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified an unexpected chromatin-modifying role for POLE2 beyond replication, showing it can couple the replication fork to transcriptional repression.\",\n      \"evidence\": \"Yeast two-hybrid screen with domain mapping (aa 85-250) plus reporter assays with trichostatin A inhibition in mouse\",\n      \"pmids\": [\"11872158\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No demonstration at endogenous chromatin loci\", \"Physiological consequence of HDAC recruitment during replication unresolved\", \"Mouse system; human validation absent\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a direct biochemical mechanism by which POLE2 couples DNA Pol\\u03b5 to replisome disassembly, answering how the TRAIP ligase is delivered to the CMG helicase at mitosis.\",\n      \"evidence\": \"Biochemical reconstitution, co-IP, TTF2 motif mutagenesis, and in vitro ubiquitylation (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.12.01.626218\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Cellular requirement for the POLE2-TTF2 interaction in MiDAS not fully established\", \"Structural basis of the POLE2 pocket-TTF2 interface not resolved at the time\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Generalized POLE2's partner-binding role, showing the C-terminal pocket is a broad NPF-motif receptor rather than a dedicated single-partner interface, recasting POLE2 as a replication hub.\",\n      \"evidence\": \"Native holdup quantitative binding, residue mutagenesis (Y513/E520/S522), AlphaFold prediction, and proteome-scale affinity screens (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.03.17.643635\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not peer-reviewed\", \"Functional consequences of WDHD1 and DONSON recruitment via this pocket not dissected\", \"No experimental crystal/cryo-EM structure of the bound pocket\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected POLE2 levels to a cancer survival program, placing it upstream of an anti-ferroptosis axis that sustains tumor cell proliferation.\",\n      \"evidence\": \"Lentiviral overexpression/knockdown with NRF2/GPX4 silencing rescue and ferroptosis assays in gastric cancer cells\",\n      \"pmids\": [\"38070189\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking the replication subunit to NRF2 induction unknown\", \"Correlative epistasis rather than direct biochemical coupling\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked POLE2 to transcription-factor stabilization in tumors, placing it upstream of AURKA-dependent FOXM1 control of proliferation.\",\n      \"evidence\": \"shRNA knockdown, ubiquitination assay, and FOXM1-knockdown rescue in glioblastoma\",\n      \"pmids\": [\"35039475\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical link between POLE2 and AURKA/FOXM1 not shown\", \"Whether effect reflects replication-stress signaling versus a moonlighting role unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how POLE2's defined replisome/NPF-receptor biochemistry mechanistically produces the diverse oncogenic signaling outputs (FOXM1/AURKA, NRF2/GPX4, CD44/MDM2, Wnt/\\u03b2-catenin, PI3K/AKT) reported in cancer models.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct biochemical bridge between the replication B-subunit function and the cytoplasmic/transcriptional signaling axes\", \"Most cancer findings are single-lab knockdown/rescue without structural or interaction-level mechanism\", \"Several pathway placements rest on Western blot epistasis or computational prediction only\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\n      \"DNA polymerase epsilon\",\n      \"Sin3/HDAC co-repressor complex\"\n    ],\n    \"partners\": [\n      \"POLE\",\n      \"SAP18\",\n      \"TTF2\",\n      \"WDHD1\",\n      \"DONSON\",\n      \"TRAIP\",\n      \"GINS4\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":3,"faith_total":3,"faith_pct":100.0}}