{"gene":"POLR2J","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":1993,"finding":"Yeast RPB11 (ortholog of human POLR2J) is an essential subunit of RNA polymerase II; it shares a conserved 19-amino-acid segment with RNA polymerase I/III subunit AC19 and bacterial RNA polymerase alpha subunit; mutations affecting RNA polymerase assembly map within this segment, implicating it in subunit–subunit interactions.","method":"Gene isolation, sequence analysis, genetic essentiality testing, and mutational mapping","journal":"Gene expression","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic essentiality established, assembly mutations mapped to conserved region, single lab but multiple lines of evidence","pmids":["8508029"],"is_preprint":false},{"year":1994,"finding":"Human POLR2J (hRPB14) contains a conserved 19-amino-acid N-terminal motif shared with other RNA polymerase subunits and the bacterial alpha subunit; this motif is implicated in subunit assembly, and POLR2J is proposed to form a heterodimer with hRPB33 (RPB3) analogous to the bacterial alpha homodimer.","method":"cDNA cloning, amino acid sequence comparison, motif conservation analysis","journal":"Gene","confidence":"Low","confidence_rationale":"Tier 4 / Weak — sequence/comparative analysis only, no direct biochemical assembly assay performed","pmids":["8056345"],"is_preprint":false},{"year":2005,"finding":"Human POLR2J heterodimerizes with RPB3 primarily through conserved N-terminal alpha-motif interactions, whereas the yeast RPB3/RPB11 heterodimer critically requires the C-terminal region of RPB11; this divergence in heterodimerization interface allows multiple human RPB11 variants (including POLR2J) to dimerize with equivalent efficiency with RPB3.","method":"Yeast two-hybrid and in vitro heterodimerization assays comparing yeast and human subunit combinations with C-terminal truncations and N-terminal alpha-motif mutations","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction mapping with domain mutants, yeast and human systems compared, multiple orthogonal approaches in single rigorous study","pmids":["15987790"],"is_preprint":false},{"year":2009,"finding":"In yeast, the Med18 (Srb5) subunit of the Mediator complex was identified as a multicopy suppressor of the Leu111Ala point mutation in the C-terminal region of RPB11 (POLR2J ortholog), establishing a functional interaction between the Mediator complex and the RNA polymerase II core via the C-terminal region of RPB11.","method":"Multicopy suppressor screen; point mutation (L111A) complementation with SRB5/Med18 overexpression","journal":"Bioorganicheskaia khimiia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis/suppressor screen with defined point mutation, single lab","pmids":["19928061"],"is_preprint":false},{"year":2011,"finding":"A minor isoform of human POLR2J (hRPB11cα) interacts with three subunits of translation initiation factor eIF3 (eIF3a, eIF3i, and eIF3m) as detected by yeast two-hybrid, suggesting a role in coupling transcription to downstream mRNA processing/transport steps.","method":"Yeast two-hybrid (YTH) system; subcellular localization of eIF3m isoforms","journal":"Biochemistry. Biokhimiia","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single method (yeast two-hybrid), single lab, no biochemical validation of direct interaction","pmids":["22022972"],"is_preprint":false},{"year":2024,"finding":"POLR2J interacts with STAT3 in glioblastoma cells and this interaction promotes metastatic potential; POLR2J knockdown inhibits cell proliferation, induces G1/S cell cycle arrest, activates the unfolded protein response (UPR), and enhances sensitivity to vorinostat-induced apoptosis.","method":"Co-immunoprecipitation (interaction with STAT3), siRNA knockdown, cell proliferation/apoptosis/migration assays, cell cycle analysis","journal":"American journal of cancer research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP for STAT3 interaction, multiple functional readouts (proliferation, apoptosis, migration, cell cycle), single lab","pmids":["38859843"],"is_preprint":false},{"year":2026,"finding":"POLR2J knockdown in lung adenocarcinoma cells suppresses cell proliferation, increases ROS production and DNA damage response (DDR), decreases STAT3 phosphorylation and GPX4 expression, and promotes ferroptosis; IL-6 treatment reverses knockdown-mediated inhibition of p-STAT3/STAT3, implicating a POLR2J–STAT3–GPX4 signaling axis.","method":"siRNA knockdown and overexpression, MTT/colony formation assays, ROS assay, Western blotting, transcriptomic analysis, IL-6 rescue experiment","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (knockdown/OE, Western blot, ROS assay, rescue with IL-6), single lab, no direct binding assay for STAT3","pmids":["42063717"],"is_preprint":false}],"current_model":"POLR2J (hRPB14/RPB11) is an essential subunit of RNA polymerase II that heterodimerizes with RPB3 via conserved N-terminal alpha-motifs, contributes to RNAP II assembly through its C-terminal region (which also mediates a functional interaction with the Mediator subunit Med18/Srb5), and in human cells has minor isoforms that interact with eIF3 translation initiation factor subunits; additionally, POLR2J promotes cancer cell survival partly through activation of a STAT3–GPX4 signaling axis that suppresses oxidative stress and ferroptosis."},"narrative":{"mechanistic_narrative":"POLR2J (hRPB14/RPB11) is an essential subunit of RNA polymerase II that participates in assembly of the polymerase core through subunit–subunit interactions [PMID:8508029]. It heterodimerizes with RPB3, an interaction mediated in human cells primarily through a conserved N-terminal alpha-motif; this contrasts with yeast RPB11, where the C-terminal region is critical, and the divergence allows multiple human RPB11 variants to dimerize with RPB3 with equivalent efficiency [PMID:15987790]. The C-terminal region also mediates a functional link to the transcriptional machinery, as the Mediator subunit Med18/Srb5 acts as a multicopy suppressor of a C-terminal point mutation in the RPB11 ortholog, connecting the polymerase core to the Mediator complex [PMID:19928061]. Beyond its core transcriptional role, POLR2J interacts with STAT3 and supports cancer cell survival: its knockdown suppresses proliferation, induces cell cycle arrest and the unfolded protein response, and sensitizes cells to apoptosis [PMID:38859843], and in lung adenocarcinoma it sustains a STAT3–GPX4 signaling axis that limits ROS, DNA damage, and ferroptosis [PMID:42063717].","teleology":[{"year":1993,"claim":"Established that the POLR2J ortholog is an indispensable RNA polymerase II subunit and localized its assembly function to a conserved segment shared across RNA polymerase families, defining it as a subunit–subunit interaction module.","evidence":"Gene isolation, essentiality testing, and mutational mapping of assembly-defective alleles in yeast RPB11","pmids":["8508029"],"confidence":"Medium","gaps":["Does not resolve the direct binding partner of the conserved segment within the polymerase","No structural model of the assembly interface"]},{"year":1994,"claim":"Extended the conserved-motif concept to human POLR2J and predicted a heterodimer with RPB3 analogous to the bacterial alpha homodimer, framing how the human subunit fits into polymerase architecture.","evidence":"cDNA cloning and comparative sequence/motif analysis of human hRPB14","pmids":["8056345"],"confidence":"Low","gaps":["Sequence comparison only; no biochemical demonstration of the predicted heterodimer","Functional consequence of the motif not tested"]},{"year":2005,"claim":"Resolved how POLR2J contacts RPB3 and showed the human heterodimerization interface diverged from yeast, explaining why multiple human RPB11 variants can pair with RPB3.","evidence":"Yeast two-hybrid and in vitro heterodimerization assays with C-terminal truncations and N-terminal alpha-motif mutants, comparing yeast and human subunits","pmids":["15987790"],"confidence":"High","gaps":["Functional consequence of variant heterodimers within assembled polymerase not established","No structure of the human RPB3/RPB11 dimer"]},{"year":2009,"claim":"Connected the C-terminal region of the POLR2J ortholog to the Mediator complex, linking core polymerase architecture to transcriptional regulation.","evidence":"Multicopy suppressor screen in yeast identifying Med18/Srb5 as a suppressor of an RPB11 L111A point mutation","pmids":["19928061"],"confidence":"Medium","gaps":["Genetic suppression does not demonstrate direct physical contact between RPB11 and Med18","Human relevance not tested"]},{"year":2011,"claim":"Raised the possibility that a minor human POLR2J isoform couples transcription to translation initiation via contacts with eIF3 subunits.","evidence":"Yeast two-hybrid detection of interactions between hRPB11cα and eIF3a, eIF3i, and eIF3m, with eIF3m localization analysis","pmids":["22022972"],"confidence":"Low","gaps":["Single-method (yeast two-hybrid) with no biochemical validation of direct interaction","Functional role of the isoform-eIF3 link untested"]},{"year":2024,"claim":"Implicated POLR2J in cancer cell survival beyond its transcriptional role, identifying a STAT3 interaction and showing that its loss arrests the cell cycle and triggers stress responses.","evidence":"Co-immunoprecipitation with STAT3 plus siRNA knockdown with proliferation, migration, apoptosis, cell cycle, and UPR readouts in glioblastoma cells","pmids":["38859843"],"confidence":"Medium","gaps":["Co-IP does not establish a direct or reciprocally validated STAT3 interaction","Mechanism linking transcriptional subunit function to STAT3 signaling unclear"]},{"year":2026,"claim":"Defined a POLR2J–STAT3–GPX4 axis controlling redox balance and ferroptosis, providing a survival mechanism in lung adenocarcinoma.","evidence":"siRNA knockdown/overexpression, ROS assay, Western blotting, transcriptomics, and IL-6 rescue of p-STAT3 in lung adenocarcinoma cells","pmids":["42063717"],"confidence":"Medium","gaps":["No direct binding assay for the POLR2J–STAT3 interaction","Whether the axis reflects POLR2J's core transcriptional function or a separate activity is unresolved"]},{"year":null,"claim":"It remains unresolved how POLR2J's essential role in RNA polymerase II assembly mechanistically connects to the STAT3–GPX4 survival axis observed in cancer cells.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the human polymerase incorporating POLR2J variants","Direct physical basis of the STAT3 interaction not defined","Causal link between transcriptional and ferroptosis-suppressing functions unestablished"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,3]}],"complexes":["RNA polymerase II"],"partners":["RPB3","MED18","STAT3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P52435","full_name":"DNA-directed RNA polymerase II subunit RPB11-a","aliases":["DNA-directed RNA polymerase II subunit J-1","RNA polymerase II 13.3 kDa subunit"],"length_aa":117,"mass_kda":13.3,"function":"Core component of RNA polymerase II (Pol II), a DNA-dependent RNA polymerase which synthesizes mRNA precursors and many functional non-coding RNAs using the four ribonucleoside triphosphates as substrates","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P52435/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/POLR2J","classification":"Common Essential","n_dependent_lines":3,"n_total_lines":4,"dependency_fraction":0.75},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000005075","cell_line_id":"CID000705","localizations":[{"compartment":"nuclear_punctae","grade":3},{"compartment":"nucleoplasm","grade":3},{"compartment":"cytoplasmic","grade":1}],"interactors":[{"gene":"POLR2I","stoichiometry":10.0},{"gene":"POLR2C","stoichiometry":10.0},{"gene":"POLR2B","stoichiometry":10.0},{"gene":"POLR2J3;POLR2J;POLR2J2","stoichiometry":10.0},{"gene":"SUPT5H","stoichiometry":4.0},{"gene":"URI1","stoichiometry":0.2},{"gene":"PIH1D1","stoichiometry":0.2},{"gene":"POLR2K","stoichiometry":0.2},{"gene":"POLR2E","stoichiometry":0.2},{"gene":"POLR2A","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000705","total_profiled":1310},"omim":[{"mim_id":"611479","title":"GPN-LOOP GTPase 1; GPN1","url":"https://www.omim.org/entry/611479"},{"mim_id":"611477","title":"RNA POLYMERASE II-ASSOCIATED PROTEIN 3; RPAP3","url":"https://www.omim.org/entry/611477"},{"mim_id":"611475","title":"RNA POLYMERASE II-ASSOCIATED PROTEIN 1; RPAP1","url":"https://www.omim.org/entry/611475"},{"mim_id":"604150","title":"POLYMERASE II, RNA, SUBUNIT J; POLR2J","url":"https://www.omim.org/entry/604150"},{"mim_id":"180663","title":"POLYMERASE II, RNA, SUBUNIT C; POLR2C","url":"https://www.omim.org/entry/180663"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/POLR2J"},"hgnc":{"alias_symbol":["RPB11","hRPB14","RPB11A","RPB11m","POLR2J1"],"prev_symbol":[]},"alphafold":{"accession":"P52435","domains":[{"cath_id":"3.30.1360.10","chopping":"5-113","consensus_level":"high","plddt":95.1636,"start":5,"end":113}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P52435","model_url":"https://alphafold.ebi.ac.uk/files/AF-P52435-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P52435-F1-predicted_aligned_error_v6.png","plddt_mean":94.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=POLR2J","jax_strain_url":"https://www.jax.org/strain/search?query=POLR2J"},"sequence":{"accession":"P52435","fasta_url":"https://rest.uniprot.org/uniprotkb/P52435.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P52435/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P52435"}},"corpus_meta":[{"pmid":"8508029","id":"PMC_8508029","title":"Yeast RNA polymerase II subunit RPB11 is related to a subunit shared by RNA polymerase I and III.","date":"1993","source":"Gene expression","url":"https://pubmed.ncbi.nlm.nih.gov/8508029","citation_count":43,"is_preprint":false},{"pmid":"8056345","id":"PMC_8056345","title":"Human RNA polymerase II subunit hRPB14 is homologous to yeast RNA polymerase I, II, and III subunits (AC19 and RPB11) and is similar to a portion of the bacterial RNA polymerase alpha subunit.","date":"1994","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/8056345","citation_count":30,"is_preprint":false},{"pmid":"15987790","id":"PMC_15987790","title":"Distinct regions of RPB11 are required for heterodimerization with RPB3 in human and yeast RNA polymerase II.","date":"2005","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/15987790","citation_count":14,"is_preprint":false},{"pmid":"22022972","id":"PMC_22022972","title":"A minor isoform of the human RNA polymerase II subunit hRPB11 (POLR2J) interacts with several components of the translation initiation factor eIF3.","date":"2011","source":"Biochemistry. Biokhimiia","url":"https://pubmed.ncbi.nlm.nih.gov/22022972","citation_count":12,"is_preprint":false},{"pmid":"25549102","id":"PMC_25549102","title":"Measurement of mRNA decay rates in Saccharomyces cerevisiae using rpb1-1 strains.","date":"2014","source":"Journal of visualized experiments : JoVE","url":"https://pubmed.ncbi.nlm.nih.gov/25549102","citation_count":10,"is_preprint":false},{"pmid":"38859843","id":"PMC_38859843","title":"POLR2J expression promotes glioblastoma malignancy by regulating oxidative stress and the STAT3 signaling pathway.","date":"2024","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/38859843","citation_count":6,"is_preprint":false},{"pmid":"19928061","id":"PMC_19928061","title":"[The functional interaction of an RNA polymerase II Rpb11 subunit with the Med18 subunit (Srb5) of the Saccharomyces cerevisiae mediator complex].","date":"2009","source":"Bioorganicheskaia khimiia","url":"https://pubmed.ncbi.nlm.nih.gov/19928061","citation_count":4,"is_preprint":false},{"pmid":"21061629","id":"PMC_21061629","title":"[PSM2 and POLR2J gene families as molecular markers of the higher primate evolution].","date":"2010","source":"Genetika","url":"https://pubmed.ncbi.nlm.nih.gov/21061629","citation_count":3,"is_preprint":false},{"pmid":"42063717","id":"PMC_42063717","title":"POLR2J knockdown promotes ROS-induced DDR and ferroptosis by inhibiting the STAT3-GPX4 signaling axis in LUAD.","date":"2026","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/42063717","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":5816,"output_tokens":1776,"usd":0.022044,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8661,"output_tokens":2455,"usd":0.05234,"stage2_stop_reason":"end_turn"},"total_usd":0.074384,"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\": 1993,\n      \"finding\": \"Yeast RPB11 (ortholog of human POLR2J) is an essential subunit of RNA polymerase II; it shares a conserved 19-amino-acid segment with RNA polymerase I/III subunit AC19 and bacterial RNA polymerase alpha subunit; mutations affecting RNA polymerase assembly map within this segment, implicating it in subunit–subunit interactions.\",\n      \"method\": \"Gene isolation, sequence analysis, genetic essentiality testing, and mutational mapping\",\n      \"journal\": \"Gene expression\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic essentiality established, assembly mutations mapped to conserved region, single lab but multiple lines of evidence\",\n      \"pmids\": [\"8508029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Human POLR2J (hRPB14) contains a conserved 19-amino-acid N-terminal motif shared with other RNA polymerase subunits and the bacterial alpha subunit; this motif is implicated in subunit assembly, and POLR2J is proposed to form a heterodimer with hRPB33 (RPB3) analogous to the bacterial alpha homodimer.\",\n      \"method\": \"cDNA cloning, amino acid sequence comparison, motif conservation analysis\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — sequence/comparative analysis only, no direct biochemical assembly assay performed\",\n      \"pmids\": [\"8056345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Human POLR2J heterodimerizes with RPB3 primarily through conserved N-terminal alpha-motif interactions, whereas the yeast RPB3/RPB11 heterodimer critically requires the C-terminal region of RPB11; this divergence in heterodimerization interface allows multiple human RPB11 variants (including POLR2J) to dimerize with equivalent efficiency with RPB3.\",\n      \"method\": \"Yeast two-hybrid and in vitro heterodimerization assays comparing yeast and human subunit combinations with C-terminal truncations and N-terminal alpha-motif mutations\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction mapping with domain mutants, yeast and human systems compared, multiple orthogonal approaches in single rigorous study\",\n      \"pmids\": [\"15987790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In yeast, the Med18 (Srb5) subunit of the Mediator complex was identified as a multicopy suppressor of the Leu111Ala point mutation in the C-terminal region of RPB11 (POLR2J ortholog), establishing a functional interaction between the Mediator complex and the RNA polymerase II core via the C-terminal region of RPB11.\",\n      \"method\": \"Multicopy suppressor screen; point mutation (L111A) complementation with SRB5/Med18 overexpression\",\n      \"journal\": \"Bioorganicheskaia khimiia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis/suppressor screen with defined point mutation, single lab\",\n      \"pmids\": [\"19928061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A minor isoform of human POLR2J (hRPB11cα) interacts with three subunits of translation initiation factor eIF3 (eIF3a, eIF3i, and eIF3m) as detected by yeast two-hybrid, suggesting a role in coupling transcription to downstream mRNA processing/transport steps.\",\n      \"method\": \"Yeast two-hybrid (YTH) system; subcellular localization of eIF3m isoforms\",\n      \"journal\": \"Biochemistry. Biokhimiia\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single method (yeast two-hybrid), single lab, no biochemical validation of direct interaction\",\n      \"pmids\": [\"22022972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"POLR2J interacts with STAT3 in glioblastoma cells and this interaction promotes metastatic potential; POLR2J knockdown inhibits cell proliferation, induces G1/S cell cycle arrest, activates the unfolded protein response (UPR), and enhances sensitivity to vorinostat-induced apoptosis.\",\n      \"method\": \"Co-immunoprecipitation (interaction with STAT3), siRNA knockdown, cell proliferation/apoptosis/migration assays, cell cycle analysis\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP for STAT3 interaction, multiple functional readouts (proliferation, apoptosis, migration, cell cycle), single lab\",\n      \"pmids\": [\"38859843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"POLR2J knockdown in lung adenocarcinoma cells suppresses cell proliferation, increases ROS production and DNA damage response (DDR), decreases STAT3 phosphorylation and GPX4 expression, and promotes ferroptosis; IL-6 treatment reverses knockdown-mediated inhibition of p-STAT3/STAT3, implicating a POLR2J–STAT3–GPX4 signaling axis.\",\n      \"method\": \"siRNA knockdown and overexpression, MTT/colony formation assays, ROS assay, Western blotting, transcriptomic analysis, IL-6 rescue experiment\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (knockdown/OE, Western blot, ROS assay, rescue with IL-6), single lab, no direct binding assay for STAT3\",\n      \"pmids\": [\"42063717\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"POLR2J (hRPB14/RPB11) is an essential subunit of RNA polymerase II that heterodimerizes with RPB3 via conserved N-terminal alpha-motifs, contributes to RNAP II assembly through its C-terminal region (which also mediates a functional interaction with the Mediator subunit Med18/Srb5), and in human cells has minor isoforms that interact with eIF3 translation initiation factor subunits; additionally, POLR2J promotes cancer cell survival partly through activation of a STAT3–GPX4 signaling axis that suppresses oxidative stress and ferroptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"POLR2J (hRPB14/RPB11) is an essential subunit of RNA polymerase II that participates in assembly of the polymerase core through subunit–subunit interactions [#0]. It heterodimerizes with RPB3, an interaction mediated in human cells primarily through a conserved N-terminal alpha-motif; this contrasts with yeast RPB11, where the C-terminal region is critical, and the divergence allows multiple human RPB11 variants to dimerize with RPB3 with equivalent efficiency [#2]. The C-terminal region also mediates a functional link to the transcriptional machinery, as the Mediator subunit Med18/Srb5 acts as a multicopy suppressor of a C-terminal point mutation in the RPB11 ortholog, connecting the polymerase core to the Mediator complex [#3]. Beyond its core transcriptional role, POLR2J interacts with STAT3 and supports cancer cell survival: its knockdown suppresses proliferation, induces cell cycle arrest and the unfolded protein response, and sensitizes cells to apoptosis [#5], and in lung adenocarcinoma it sustains a STAT3–GPX4 signaling axis that limits ROS, DNA damage, and ferroptosis [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Established that the POLR2J ortholog is an indispensable RNA polymerase II subunit and localized its assembly function to a conserved segment shared across RNA polymerase families, defining it as a subunit–subunit interaction module.\",\n      \"evidence\": \"Gene isolation, essentiality testing, and mutational mapping of assembly-defective alleles in yeast RPB11\",\n      \"pmids\": [\"8508029\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not resolve the direct binding partner of the conserved segment within the polymerase\", \"No structural model of the assembly interface\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Extended the conserved-motif concept to human POLR2J and predicted a heterodimer with RPB3 analogous to the bacterial alpha homodimer, framing how the human subunit fits into polymerase architecture.\",\n      \"evidence\": \"cDNA cloning and comparative sequence/motif analysis of human hRPB14\",\n      \"pmids\": [\"8056345\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Sequence comparison only; no biochemical demonstration of the predicted heterodimer\", \"Functional consequence of the motif not tested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolved how POLR2J contacts RPB3 and showed the human heterodimerization interface diverged from yeast, explaining why multiple human RPB11 variants can pair with RPB3.\",\n      \"evidence\": \"Yeast two-hybrid and in vitro heterodimerization assays with C-terminal truncations and N-terminal alpha-motif mutants, comparing yeast and human subunits\",\n      \"pmids\": [\"15987790\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of variant heterodimers within assembled polymerase not established\", \"No structure of the human RPB3/RPB11 dimer\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected the C-terminal region of the POLR2J ortholog to the Mediator complex, linking core polymerase architecture to transcriptional regulation.\",\n      \"evidence\": \"Multicopy suppressor screen in yeast identifying Med18/Srb5 as a suppressor of an RPB11 L111A point mutation\",\n      \"pmids\": [\"19928061\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genetic suppression does not demonstrate direct physical contact between RPB11 and Med18\", \"Human relevance not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Raised the possibility that a minor human POLR2J isoform couples transcription to translation initiation via contacts with eIF3 subunits.\",\n      \"evidence\": \"Yeast two-hybrid detection of interactions between hRPB11cα and eIF3a, eIF3i, and eIF3m, with eIF3m localization analysis\",\n      \"pmids\": [\"22022972\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single-method (yeast two-hybrid) with no biochemical validation of direct interaction\", \"Functional role of the isoform-eIF3 link untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Implicated POLR2J in cancer cell survival beyond its transcriptional role, identifying a STAT3 interaction and showing that its loss arrests the cell cycle and triggers stress responses.\",\n      \"evidence\": \"Co-immunoprecipitation with STAT3 plus siRNA knockdown with proliferation, migration, apoptosis, cell cycle, and UPR readouts in glioblastoma cells\",\n      \"pmids\": [\"38859843\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-IP does not establish a direct or reciprocally validated STAT3 interaction\", \"Mechanism linking transcriptional subunit function to STAT3 signaling unclear\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Defined a POLR2J–STAT3–GPX4 axis controlling redox balance and ferroptosis, providing a survival mechanism in lung adenocarcinoma.\",\n      \"evidence\": \"siRNA knockdown/overexpression, ROS assay, Western blotting, transcriptomics, and IL-6 rescue of p-STAT3 in lung adenocarcinoma cells\",\n      \"pmids\": [\"42063717\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct binding assay for the POLR2J–STAT3 interaction\", \"Whether the axis reflects POLR2J's core transcriptional function or a separate activity is unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how POLR2J's essential role in RNA polymerase II assembly mechanistically connects to the STAT3–GPX4 survival axis observed in cancer cells.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the human polymerase incorporating POLR2J variants\", \"Direct physical basis of the STAT3 interaction not defined\", \"Causal link between transcriptional and ferroptosis-suppressing functions unestablished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [\"RNA polymerase II\"],\n    \"partners\": [\"RPB3\", \"MED18\", \"STAT3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}