{"gene":"RPP30","run_date":"2026-04-28T20:42:06","timeline":{"discoveries":[{"year":2010,"finding":"Archaeal RNase P protein homologs Pop5 and Rpp30 (from Pyrococcus horikoshii) function equivalently to the bacterial C5 protein in activating the catalytic RNA C-domain of RNase P, while Rpp21 and Rpp29 are implicated in stabilization of the S-domain. This was demonstrated using chimeric RNase P RNAs in which C- and S-domains of E. coli M1 RNA and P. horikoshii RNA were exchanged, and reconstitution assays with pre-tRNA cleavage activity.","method":"Chimeric RNA reconstitution assay, in vitro pre-tRNA cleavage activity","journal":"Bioscience, biotechnology, and biochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with domain-swapped chimeric RNAs and mutagenesis-level dissection of functional domains","pmids":["20139629"],"is_preprint":false},{"year":2011,"finding":"Archaeal RPP30 and Pop5 (from Pyrococcus furiosus) form a tight 1:1 protein-protein interaction with net heterotetramer stoichiometry (two copies each of Pop5 and RPP30, ~78 kDa). NMR chemical shift perturbation mapping revealed the binding surface of Pop5 on RPP30. RPP30 is well-structured in solution with a TIM-barrel fold. ITC confirmed tight binding with complex isotherms indicating higher-order assembly.","method":"NMR spectroscopy (backbone assignments + chemical shift perturbation), isothermal titration calorimetry (ITC), size-exclusion chromatography, light scattering","journal":"Archaea (Vancouver, B.C.)","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal biophysical methods (NMR, ITC, SEC, light scattering) in a single study with rigorous controls","pmids":["22162665"],"is_preprint":false},{"year":2015,"finding":"The archaeal Pop5-Rpp30 heterotetramer (PhoRpp30-(PhoPop5)2-PhoRpp30) strongly interacts with the stem-loop SL3 of RNase P RNA (PhopRNA), whereas Pop5 alone has markedly reduced affinity and Rpp30 alone has little affinity to SL3. The C-terminal helix (α4) of Pop5 functions as the molecular recognition element for SL3. Rpp30 assists Pop5 in attaining a functionally active conformation by shielding hydrophobic surfaces, enabling the tetramer to bridge SL3 and SL16 in PhopRNA for C-domain activation.","method":"Surface plasmon resonance (SPR) with Pop5 mutants, gel filtration chromatography","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1-2 — SPR binding assays with site-directed mutants plus structural modeling, multiple orthogonal methods","pmids":["26152732"],"is_preprint":false},{"year":2006,"finding":"A Dictyostelium discoideum Rpp30 homolog (DRpp30, 40.7 kDa) co-purifies with RNase P holoenzyme and can bind both D. discoideum RNase P RNA and tRNA transcripts in vitro. Homology modeling indicates DRpp30 adopts a TIM-barrel fold, consistent with archaeal and human Rpp30 structures.","method":"Immunochemical analysis of RNase P active fractions, in vitro RNA-binding assay, homology modeling","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-purification with active RNase P fractions and direct in vitro RNA binding, single study","pmids":["17207566"],"is_preprint":false},{"year":2015,"finding":"Archaeal Rpp30 from Thermococcus kodakarensis (TkoRpp30) adopts a TIM-barrel fold and forms a complex with TkoPop5, as determined by crystal structures of TkoRpp30 alone and in complex with TkoPop5. Reconstitution experiments showed that TkoRpp30 can substitute for PhoRpp30 in P. horikoshii RNase P with slightly reduced pre-tRNA cleavage activity, confirming functional and structural conservation of Rpp30 across archaea.","method":"X-ray crystallography (crystal structures of Rpp30 alone and in complex with Pop5), in vitro pre-tRNA cleavage reconstitution assay","journal":"Bioscience, biotechnology, and biochemistry","confidence":"High","confidence_rationale":"Tier 1 — crystal structures combined with functional reconstitution assay","pmids":["25704799"],"is_preprint":false},{"year":2019,"finding":"Human RNase P/MRP complex (of which RPP30 is a protein subunit) mediates endoribonucleolytic cleavage of m6A-containing RNAs. YTHDF2 (m6A reader) recruits RNase P/MRP via the adaptor protein HRSP12, which bridges YTHDF2 and RNase P/MRP to elicit rapid degradation of m6A-modified RNAs, including a subset of circular RNAs. Transcriptome-wide analyses identified HRSP12-binding sites and RNase P/MRP-directed cleavage sites flanking YTHDF2-binding sites.","method":"Co-immunoprecipitation, in vitro cleavage assays, transcriptome-wide RNA-seq, CLIP-seq, domain-mapping experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including in vitro reconstitution, transcriptome-wide analyses, and domain-level mechanistic dissection; highly cited","pmids":["30930054"],"is_preprint":false}],"current_model":"RPP30 is a protein subunit of the RNase P/MRP ribonucleoprotein complex that adopts a TIM-barrel fold; it forms a heterotetrameric subcomplex with Pop5 (two copies each), wherein Rpp30 stabilizes Pop5's active conformation and the tetramer activates the catalytic C-domain of RNase P RNA by engaging stem-loops SL3 and SL16; beyond canonical pre-tRNA 5'-maturation, the human RNase P/MRP complex containing RPP30 is recruited by YTHDF2–HRSP12 to perform endoribonucleolytic cleavage of m6A-modified mRNAs and circular RNAs."},"narrative":{"teleology":[{"year":2006,"claim":"Identification of a Dictyostelium Rpp30 homolog that co-purifies with RNase P and binds its RNA subunit extended the known phylogenetic range of RPP30 as an integral RNase P component with a conserved TIM-barrel fold.","evidence":"Immunochemical co-purification with active RNase P fractions and in vitro RNA-binding assay in D. discoideum","pmids":["17207566"],"confidence":"Medium","gaps":["Single study without reciprocal validation","No stoichiometric or structural data for the eukaryotic complex at this stage"]},{"year":2010,"claim":"Domain-swap experiments established that the Pop5–Rpp30 pair specifically activates the catalytic C-domain of RNase P RNA, resolving which protein subunits control which functional domain of the ribozyme.","evidence":"Chimeric archaeal/bacterial RNase P RNA reconstitution with in vitro pre-tRNA cleavage assays","pmids":["20139629"],"confidence":"High","gaps":["Mechanism by which Pop5–Rpp30 contacts the C-domain RNA was not resolved at atomic level","Whether human RPP30 functions identically was not directly tested"]},{"year":2011,"claim":"Biophysical characterization revealed that RPP30 adopts a TIM-barrel fold and forms a tight heterotetrameric complex with Pop5 (2:2 stoichiometry), defining the minimal assembly unit for C-domain activation.","evidence":"NMR backbone assignments, chemical shift perturbation mapping, ITC, SEC, and light scattering on archaeal Rpp30–Pop5","pmids":["22162665"],"confidence":"High","gaps":["Exact RNA-binding interface of the heterotetramer was not mapped","Human complex stoichiometry not directly confirmed"]},{"year":2015,"claim":"Crystal structures of Rpp30 alone and in complex with Pop5, combined with SPR binding studies, showed that Rpp30 stabilizes Pop5's α4 helix — the key RNA-recognition element — enabling the tetramer to bridge stem-loops SL3 and SL16 for C-domain activation.","evidence":"X-ray crystallography of archaeal Rpp30 and Rpp30–Pop5 complex; SPR with Pop5 mutants; cross-species reconstitution assays","pmids":["25704799","26152732"],"confidence":"High","gaps":["High-resolution structure of the full RNase P holoenzyme with RNA was not yet available","Whether the SL3/SL16-bridging model applies to the human complex is inferred, not demonstrated"]},{"year":2019,"claim":"Discovery that the human RNase P/MRP complex (containing RPP30) functions in m6A-dependent mRNA and circRNA decay — recruited by YTHDF2 via HRSP12 — expanded RPP30's role beyond tRNA processing to a regulated mRNA turnover pathway.","evidence":"Co-immunoprecipitation, in vitro cleavage assays, transcriptome-wide RNA-seq and CLIP-seq in human cells","pmids":["30930054"],"confidence":"High","gaps":["Whether RPP30 has a specific or essential role within the complex for m6A-RNA cleavage, versus being a structural subunit, is unresolved","Structural basis for HRSP12-mediated recruitment of RNase P/MRP is unknown"]},{"year":null,"claim":"A high-resolution structure of the human RNase P holoenzyme with its RNA subunit, and direct dissection of RPP30's individual contribution to m6A-RNA cleavage versus tRNA processing, remain open questions.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of human RPP30 in the context of the full holoenzyme–substrate complex","Distinct or overlapping functions of RPP30 in tRNA processing versus m6A-RNA decay not separated genetically","Regulation of RPP30 expression or post-translational modification is uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[2,3]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,5]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2,4]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3,5]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,5]}],"complexes":["RNase P","RNase MRP"],"partners":["POP5","YTHDF2","HRSP12"],"other_free_text":[]},"mechanistic_narrative":"RPP30 is a protein subunit of the RNase P/MRP ribonucleoprotein complex that plays essential roles in pre-tRNA 5'-leader processing and endoribonucleolytic cleavage of m6A-modified mRNAs and circular RNAs. RPP30 adopts a TIM-barrel fold and forms a heterotetrameric subcomplex with Pop5 (two copies each), in which RPP30 shields hydrophobic surfaces of Pop5 to stabilize its active conformation and enable the tetramer to engage stem-loops SL3 and SL16 of RNase P RNA, thereby activating the catalytic C-domain for pre-tRNA cleavage [PMID:20139629, PMID:22162665, PMID:26152732, PMID:25704799]. Beyond canonical tRNA maturation, the human RNase P/MRP complex containing RPP30 is recruited by the m6A-reader YTHDF2 through the adaptor HRSP12 to perform endoribonucleolytic cleavage of m6A-containing transcripts, establishing a non-canonical RNA decay pathway [PMID:30930054]."},"prefetch_data":{"uniprot":{"accession":"P78346","full_name":"Ribonuclease P protein subunit p30","aliases":["RNase P subunit 2"],"length_aa":268,"mass_kda":29.3,"function":"Component of ribonuclease P, a ribonucleoprotein complex that generates mature tRNA molecules by cleaving their 5'-ends (PubMed:30454648, PubMed:9037013, PubMed:9630247). Also a component of the MRP ribonuclease complex, which cleaves pre-rRNA sequences (PubMed:28115465)","subcellular_location":"Nucleus, nucleolus","url":"https://www.uniprot.org/uniprotkb/P78346/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RPP30","classification":"Common 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RPP38","url":"https://www.omim.org/entry/606116"},{"mim_id":"606115","title":"RIBONUCLEASE P/MRP SUBUNIT p30; RPP30","url":"https://www.omim.org/entry/606115"},{"mim_id":"606114","title":"POP4 HOMOLOG, RIBONUCLEASE P/MRP SUBUNIT; POP4","url":"https://www.omim.org/entry/606114"},{"mim_id":"606113","title":"POP7 HOMOLOG, RIBONUCLEASE P/MRP SUBUNIT; POP7","url":"https://www.omim.org/entry/606113"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nucleoli","reliability":"Approved"},{"location":"Microtubule ends","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RPP30"},"hgnc":{"alias_symbol":["TSG15"],"prev_symbol":[]},"alphafold":{"accession":"P78346","domains":[{"cath_id":"3.20.20.140","chopping":"6-237","consensus_level":"medium","plddt":90.3406,"start":6,"end":237}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P78346","model_url":"https://alphafold.ebi.ac.uk/files/AF-P78346-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P78346-F1-predicted_aligned_error_v6.png","plddt_mean":84.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RPP30","jax_strain_url":"https://www.jax.org/strain/search?query=RPP30"},"sequence":{"accession":"P78346","fasta_url":"https://rest.uniprot.org/uniprotkb/P78346.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P78346/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P78346"}},"corpus_meta":[{"pmid":"29483619","id":"PMC_29483619","title":"Normalization of cell associated 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standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":18875,"output_tokens":2694,"usd":0.048517},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":5339,"output_tokens":1682,"usd":0.103118}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"Archaeal RPP30 homolog (PhoRpp30) pairs with Pop5 to activate the catalytic (C-domain) of RNase P RNA, while RPP21/RPP29 stabilize the specificity (S-domain); demonstrated using chimeric RNase P RNAs exchanging C- and S-domains between E. coli and P. horikoshii.\",\n      \"method\": \"Chimeric RNA reconstitution assay, pre-tRNA cleavage activity\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted enzymatic activity with chimeric RNAs and domain-specific functional readout\",\n      \"pmids\": [\"20139629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Archaeal RPP30 homolog (PfuRpp30) forms a 78 kDa heterotetramer (2:2) with Pop5; NMR chemical shift perturbations map the Pop5 binding surface on RPP30, and ITC confirms a tight 1:1 net stoichiometry with complex isotherms indicative of higher-order assembly.\",\n      \"method\": \"NMR spectroscopy, isothermal titration calorimetry (ITC), size exclusion chromatography, light scattering\",\n      \"journal\": \"Archaea\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal biophysical methods (NMR, ITC, SEC, light scattering) in a single study\",\n      \"pmids\": [\"22162665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The PhoRpp30/PhoPop5 heterotetramer binds stem-loop SL3 of RNase P RNA with high affinity; PhoRpp30 assists Pop5 in attaining a functionally active conformation by shielding hydrophobic surfaces, and the C-terminal helix (α4) of PhoPop5 is the molecular recognition element for SL3 binding.\",\n      \"method\": \"Surface plasmon resonance (SPR), gel filtration, site-directed mutagenesis of Pop5\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — SPR binding assay with mutant analysis and gel filtration, multiple orthogonal methods\",\n      \"pmids\": [\"26152732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structures of TkoRpp30 alone and in complex with TkoPop5 show that Rpp30 adopts a TIM-barrel fold and Pop5 adopts an RRM-like fold; reconstituted RNase P particles with TkoRpp30 or TkoPop5 substituted for their P. horikoshii counterparts retain pre-tRNA cleavage activity, demonstrating functional and structural conservation.\",\n      \"method\": \"X-ray crystallography, reconstitution assay with pre-tRNA cleavage\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus functional reconstitution assay\",\n      \"pmids\": [\"25704799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Dictyostelium discoideum RNase P contains a Rpp30 homolog (DRpp30, 40.7 kDa with TIM-barrel fold) that co-purifies with RNase P holoenzyme activity and can bind RNase P RNA and tRNA transcripts in vitro.\",\n      \"method\": \"Heterologous expression, immunochemical co-purification with RNase P active fractions, in vitro RNA binding, homology modeling\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — co-purification with active fractions and in vitro RNA binding, single lab study\",\n      \"pmids\": [\"17207566\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RPP30 is a TIM-barrel-fold protein subunit of the RNase P ribonucleoprotein complex that heterodimerizes (forming a 2:2 heterotetramer) with Pop5; together they activate the catalytic C-domain of RNase P RNA by directly contacting a stem-loop of the RNA subunit, enabling pre-tRNA 5′-end maturation.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries only from KEPT papers.\n\n**Classification:**\n\nRetrieved papers:\n1. PMID:29483619 — RPP30 used as a reference gene for ddPCR normalization. No mechanistic findings about RPP30 protein function. EXCLUDE (no mechanism).\n2. PMID:33932077 — Rice OsRpp30 in immunity. SYMBOL COLLISION — plant (rice) gene with fundamentally different cellular context (immunity/histone deacetylase). EXCLUDE.\n3. PMID:20139629 — Archaeal Rpp30 homologs. KEEP (ortholog, consistent with mammalian RNase P protein function).\n4. PMID:32702667 — Transcriptomics/bioinformatics study on RPP30 in GBM. No direct mechanistic experiment. EXCLUDE (expression correlation only).\n5. PMID:22162665 — Archaeal Pop5-RPP30 assembly. KEEP (ortholog).\n6. PMID:26152732 — Archaeal PhoPop5/PhoRpp30 functional study. KEEP (ortholog).\n7. PMID:17207566 — Dictyostelium Rpp30 homolog. KEEP (ortholog, consistent RNase P context).\n8. PMID:25704799 — Thermococcus archaeal Rpp30. KEEP (ortholog).\n9. PMID:41873718 — Rice OsRpp30. EXCLUDE (plant, same issue as #2).\n10. PMID:41133709 — RPP30 as reference gene for NBS ddPCR. No mechanism. EXCLUDE.\n11. bio_10.1101_2025.06.11.659223 — RPP30 as human reference gene in ddPCR. No mechanism. EXCLUDE.\n\nGene2pubmed curated papers:\n- PMID:30930054 — RNase P/MRP complex cleaves m6A-containing RNAs. KEEP (directly describes human RNase P/MRP complex mechanism; RPP30 is a subunit).\n- PMID:17081983 — Phosphoproteomics. EXCLUDE (no RPP30-specific mechanism).\n- PMID:22658674 — mRNA-binding proteins atlas. EXCLUDE (no RPP30-specific mechanism).\n- PMID:12477932, 14702039, 15489334, 8125298, 16344560, 8889548 — cDNA/genome projects. EXCLUDE.\n- PMID:26472758, 26472760 — Essential genes screens. EXCLUDE (RPP30 mentioned incidentally as essential, no mechanism).\n- PMID:26186194, 28514442, 32296183, 25416956 — Interactome maps. EXCLUDE (no RPP30-specific mechanism extracted).\n- PMID:15635413 — Nucleolar proteomics. EXCLUDE (proteomics, no RPP30-specific mechanism).\n- PMID:22939629, 26344197 — Complex proteomics. EXCLUDE.\n- PMID:21873635 — GO annotation. EXCLUDE.\n- PMID:29656893, 21145461, 22863883, 30033366, 29568061, 32807901, 18461144, 16385451, 21081503 — Various topics unrelated to RPP30 mechanism. EXCLUDE.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"Archaeal RNase P protein homologs Pop5 and Rpp30 (from Pyrococcus horikoshii) function equivalently to the bacterial C5 protein in activating the catalytic RNA C-domain of RNase P, while Rpp21 and Rpp29 are implicated in stabilization of the S-domain. This was demonstrated using chimeric RNase P RNAs in which C- and S-domains of E. coli M1 RNA and P. horikoshii RNA were exchanged, and reconstitution assays with pre-tRNA cleavage activity.\",\n      \"method\": \"Chimeric RNA reconstitution assay, in vitro pre-tRNA cleavage activity\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with domain-swapped chimeric RNAs and mutagenesis-level dissection of functional domains\",\n      \"pmids\": [\"20139629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Archaeal RPP30 and Pop5 (from Pyrococcus furiosus) form a tight 1:1 protein-protein interaction with net heterotetramer stoichiometry (two copies each of Pop5 and RPP30, ~78 kDa). NMR chemical shift perturbation mapping revealed the binding surface of Pop5 on RPP30. RPP30 is well-structured in solution with a TIM-barrel fold. ITC confirmed tight binding with complex isotherms indicating higher-order assembly.\",\n      \"method\": \"NMR spectroscopy (backbone assignments + chemical shift perturbation), isothermal titration calorimetry (ITC), size-exclusion chromatography, light scattering\",\n      \"journal\": \"Archaea (Vancouver, B.C.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal biophysical methods (NMR, ITC, SEC, light scattering) in a single study with rigorous controls\",\n      \"pmids\": [\"22162665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The archaeal Pop5-Rpp30 heterotetramer (PhoRpp30-(PhoPop5)2-PhoRpp30) strongly interacts with the stem-loop SL3 of RNase P RNA (PhopRNA), whereas Pop5 alone has markedly reduced affinity and Rpp30 alone has little affinity to SL3. The C-terminal helix (α4) of Pop5 functions as the molecular recognition element for SL3. Rpp30 assists Pop5 in attaining a functionally active conformation by shielding hydrophobic surfaces, enabling the tetramer to bridge SL3 and SL16 in PhopRNA for C-domain activation.\",\n      \"method\": \"Surface plasmon resonance (SPR) with Pop5 mutants, gel filtration chromatography\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — SPR binding assays with site-directed mutants plus structural modeling, multiple orthogonal methods\",\n      \"pmids\": [\"26152732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A Dictyostelium discoideum Rpp30 homolog (DRpp30, 40.7 kDa) co-purifies with RNase P holoenzyme and can bind both D. discoideum RNase P RNA and tRNA transcripts in vitro. Homology modeling indicates DRpp30 adopts a TIM-barrel fold, consistent with archaeal and human Rpp30 structures.\",\n      \"method\": \"Immunochemical analysis of RNase P active fractions, in vitro RNA-binding assay, homology modeling\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-purification with active RNase P fractions and direct in vitro RNA binding, single study\",\n      \"pmids\": [\"17207566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Archaeal Rpp30 from Thermococcus kodakarensis (TkoRpp30) adopts a TIM-barrel fold and forms a complex with TkoPop5, as determined by crystal structures of TkoRpp30 alone and in complex with TkoPop5. Reconstitution experiments showed that TkoRpp30 can substitute for PhoRpp30 in P. horikoshii RNase P with slightly reduced pre-tRNA cleavage activity, confirming functional and structural conservation of Rpp30 across archaea.\",\n      \"method\": \"X-ray crystallography (crystal structures of Rpp30 alone and in complex with Pop5), in vitro pre-tRNA cleavage reconstitution assay\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structures combined with functional reconstitution assay\",\n      \"pmids\": [\"25704799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Human RNase P/MRP complex (of which RPP30 is a protein subunit) mediates endoribonucleolytic cleavage of m6A-containing RNAs. YTHDF2 (m6A reader) recruits RNase P/MRP via the adaptor protein HRSP12, which bridges YTHDF2 and RNase P/MRP to elicit rapid degradation of m6A-modified RNAs, including a subset of circular RNAs. Transcriptome-wide analyses identified HRSP12-binding sites and RNase P/MRP-directed cleavage sites flanking YTHDF2-binding sites.\",\n      \"method\": \"Co-immunoprecipitation, in vitro cleavage assays, transcriptome-wide RNA-seq, CLIP-seq, domain-mapping experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including in vitro reconstitution, transcriptome-wide analyses, and domain-level mechanistic dissection; highly cited\",\n      \"pmids\": [\"30930054\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RPP30 is a protein subunit of the RNase P/MRP ribonucleoprotein complex that adopts a TIM-barrel fold; it forms a heterotetrameric subcomplex with Pop5 (two copies each), wherein Rpp30 stabilizes Pop5's active conformation and the tetramer activates the catalytic C-domain of RNase P RNA by engaging stem-loops SL3 and SL16; beyond canonical pre-tRNA 5'-maturation, the human RNase P/MRP complex containing RPP30 is recruited by YTHDF2–HRSP12 to perform endoribonucleolytic cleavage of m6A-modified mRNAs and circular RNAs.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"RPP30 is a TIM-barrel-fold protein subunit of the RNase P ribonucleoprotein complex that heterodimerizes with Pop5 to form a 2:2 heterotetramer, which binds directly to stem-loop SL3 of the catalytic (C-domain) RNA subunit and activates pre-tRNA 5′-end cleavage [PMID:20139629, PMID:22162665, PMID:26152732]. Within this complex, RPP30 shields hydrophobic surfaces of Pop5, stabilizing Pop5 in a conformation competent for RNA recognition [PMID:26152732]. Crystal structures confirm the TIM-barrel architecture of RPP30 and the RRM-like fold of Pop5, and functional interchangeability of archaeal orthologs demonstrates deep structural and mechanistic conservation [PMID:25704799, PMID:17207566].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Establishing that RPP30 is a bona fide RNase P subunit: before this, whether a TIM-barrel protein co-purified with eukaryotic RNase P activity and could bind RNase P RNA was unresolved; the study showed that DRpp30 co-purifies with holoenzyme activity and binds RNase P RNA and tRNA in vitro.\",\n      \"evidence\": \"Co-purification of recombinant DRpp30 with Dictyostelium RNase P active fractions and in vitro RNA-binding assays\",\n      \"pmids\": [\"17207566\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-organism study without reciprocal depletion/rescue\", \"Direct contribution to catalysis not tested\", \"Binding stoichiometry not determined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defining the domain-specific role of RPP30: it was unclear which RNA domain RPP30 activates; chimeric RNA reconstitution showed that RPP30–Pop5 specifically activates the catalytic C-domain, while RPP21–RPP29 acts on the specificity S-domain, establishing a modular activation model.\",\n      \"evidence\": \"Chimeric E. coli/P. horikoshii RNase P RNA reconstitution with pre-tRNA cleavage activity readout\",\n      \"pmids\": [\"20139629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact RNA contacts within the C-domain not mapped\", \"Whether the same modularity applies to the eukaryal (as opposed to archaeal) holoenzyme is untested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolving RPP30–Pop5 quaternary structure: the oligomeric state of the RPP30–Pop5 subcomplex was unknown; NMR, ITC, and light scattering demonstrated a 2:2 heterotetramer and mapped the Pop5-binding surface on RPP30.\",\n      \"evidence\": \"NMR chemical shift perturbation, ITC, SEC, and multi-angle light scattering on PfuRpp30–Pop5\",\n      \"pmids\": [\"22162665\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the 2:2 stoichiometry is maintained in the context of the full holoenzyme\", \"No high-resolution structure of the heterotetramer at this stage\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identifying the RNA recognition element and the chaperoning role of RPP30: it was unknown how the RPP30–Pop5 complex contacts RNase P RNA; SPR and mutagenesis showed that the heterotetramer binds stem-loop SL3 via the C-terminal helix of Pop5, with RPP30 shielding Pop5 hydrophobic surfaces to enable an active conformation.\",\n      \"evidence\": \"SPR binding assays, gel filtration, and site-directed mutagenesis of Pop5 in the P. horikoshii system\",\n      \"pmids\": [\"26152732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the RPP30 chaperoning mechanism not resolved at atomic level\", \"Contribution of RPP30 residues to direct RNA contacts not dissected\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Establishing the atomic fold and evolutionary conservation: crystal structures of TkoRpp30 alone and with TkoPop5 confirmed the TIM-barrel fold and demonstrated that archaeal orthologs are functionally interchangeable, proving deep structural conservation.\",\n      \"evidence\": \"X-ray crystallography of T. kodakarensis Rpp30 and Rpp30–Pop5, plus cross-species reconstitution assays\",\n      \"pmids\": [\"25704799\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal structure of the human RPP30–POP5 complex\", \"Role of RPP30 in human-specific RNase P functions (e.g., RNase MRP) not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Open question: the structural basis by which human RPP30 integrates into the complete eukaryal RNase P/MRP holoenzyme and whether it performs additional roles beyond pre-tRNA processing remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of human RNase P holoenzyme with RPP30\", \"Potential non-RNase-P functions of RPP30 are unexplored\", \"In vivo consequences of RPP30 loss in mammalian cells not characterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [\"RNase P\"],\n    \"partners\": [\"POP5\"],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"RPP30 is a protein subunit of the RNase P/MRP ribonucleoprotein complex that plays essential roles in pre-tRNA 5'-leader processing and endoribonucleolytic cleavage of m6A-modified mRNAs and circular RNAs. RPP30 adopts a TIM-barrel fold and forms a heterotetrameric subcomplex with Pop5 (two copies each), in which RPP30 shields hydrophobic surfaces of Pop5 to stabilize its active conformation and enable the tetramer to engage stem-loops SL3 and SL16 of RNase P RNA, thereby activating the catalytic C-domain for pre-tRNA cleavage [PMID:20139629, PMID:22162665, PMID:26152732, PMID:25704799]. Beyond canonical tRNA maturation, the human RNase P/MRP complex containing RPP30 is recruited by the m6A-reader YTHDF2 through the adaptor HRSP12 to perform endoribonucleolytic cleavage of m6A-containing transcripts, establishing a non-canonical RNA decay pathway [PMID:30930054].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Identification of a Dictyostelium Rpp30 homolog that co-purifies with RNase P and binds its RNA subunit extended the known phylogenetic range of RPP30 as an integral RNase P component with a conserved TIM-barrel fold.\",\n      \"evidence\": \"Immunochemical co-purification with active RNase P fractions and in vitro RNA-binding assay in D. discoideum\",\n      \"pmids\": [\"17207566\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single study without reciprocal validation\", \"No stoichiometric or structural data for the eukaryotic complex at this stage\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Domain-swap experiments established that the Pop5–Rpp30 pair specifically activates the catalytic C-domain of RNase P RNA, resolving which protein subunits control which functional domain of the ribozyme.\",\n      \"evidence\": \"Chimeric archaeal/bacterial RNase P RNA reconstitution with in vitro pre-tRNA cleavage assays\",\n      \"pmids\": [\"20139629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Pop5–Rpp30 contacts the C-domain RNA was not resolved at atomic level\", \"Whether human RPP30 functions identically was not directly tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Biophysical characterization revealed that RPP30 adopts a TIM-barrel fold and forms a tight heterotetrameric complex with Pop5 (2:2 stoichiometry), defining the minimal assembly unit for C-domain activation.\",\n      \"evidence\": \"NMR backbone assignments, chemical shift perturbation mapping, ITC, SEC, and light scattering on archaeal Rpp30–Pop5\",\n      \"pmids\": [\"22162665\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact RNA-binding interface of the heterotetramer was not mapped\", \"Human complex stoichiometry not directly confirmed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Crystal structures of Rpp30 alone and in complex with Pop5, combined with SPR binding studies, showed that Rpp30 stabilizes Pop5's α4 helix — the key RNA-recognition element — enabling the tetramer to bridge stem-loops SL3 and SL16 for C-domain activation.\",\n      \"evidence\": \"X-ray crystallography of archaeal Rpp30 and Rpp30–Pop5 complex; SPR with Pop5 mutants; cross-species reconstitution assays\",\n      \"pmids\": [\"25704799\", \"26152732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure of the full RNase P holoenzyme with RNA was not yet available\", \"Whether the SL3/SL16-bridging model applies to the human complex is inferred, not demonstrated\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Discovery that the human RNase P/MRP complex (containing RPP30) functions in m6A-dependent mRNA and circRNA decay — recruited by YTHDF2 via HRSP12 — expanded RPP30's role beyond tRNA processing to a regulated mRNA turnover pathway.\",\n      \"evidence\": \"Co-immunoprecipitation, in vitro cleavage assays, transcriptome-wide RNA-seq and CLIP-seq in human cells\",\n      \"pmids\": [\"30930054\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RPP30 has a specific or essential role within the complex for m6A-RNA cleavage, versus being a structural subunit, is unresolved\", \"Structural basis for HRSP12-mediated recruitment of RNase P/MRP is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the human RNase P holoenzyme with its RNA subunit, and direct dissection of RPP30's individual contribution to m6A-RNA cleavage versus tRNA processing, remain open questions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of human RPP30 in the context of the full holoenzyme–substrate complex\", \"Distinct or overlapping functions of RPP30 in tRNA processing versus m6A-RNA decay not separated genetically\", \"Regulation of RPP30 expression or post-translational modification is uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [\n      \"RNase P\",\n      \"RNase MRP\"\n    ],\n    \"partners\": [\n      \"POP5\",\n      \"YTHDF2\",\n      \"HRSP12\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}