{"gene":"RPS28","run_date":"2026-06-10T07:46:27","timeline":{"discoveries":[{"year":1976,"finding":"RPS28 (S28) was isolated and purified from rat liver 40S ribosomal subunit by ion-exchange chromatography and gel filtration; its molecular weight and amino acid composition were characterized, establishing it as a structural component of the small ribosomal subunit.","method":"Protein purification (ion-exchange chromatography, gel filtration), SDS-PAGE, amino acid composition analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical purification and characterization from native ribosome, single lab, foundational isolation study","pmids":["947902"],"is_preprint":false},{"year":1991,"finding":"The primary amino acid sequence of rat ribosomal protein S28 (RPS28) was determined: 69 amino acids, molecular weight 7,836 Da, encoded by 8–10 gene copies, with an mRNA of ~450 nucleotides; rat S28 is homologous to Saccharomyces cerevisiae S33.","method":"cDNA sequencing, Southern blot hybridization, sequence homology analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cDNA sequencing with genomic Southern blot, single lab, two orthogonal methods","pmids":["1679328"],"is_preprint":false},{"year":1995,"finding":"In yeast, different mutations in RPS28 (encoded by RPS28A and RPS28B) can have diametrically opposite effects on translational accuracy: substitutions in the diverged N-terminal portion cause nonsense suppression or antibiotic sensitivity, while substitutions in the conserved C-terminal portion counteract SUP44/SUP46-associated antibiotic sensitivity, establishing RPS28 as a regulator of translational fidelity at the decoding center.","method":"Site-directed and random mutagenesis, genetic suppressor analysis, antibiotic sensitivity assays","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple mutant alleles tested with orthogonal genetic and biochemical readouts, replicated across two independent studies (PMID 7498767 and 8950190)","pmids":["7498767"],"is_preprint":false},{"year":1996,"finding":"Using a poly(U)-dependent cell-free translation system with yeast ribosomes bearing RPS28 mutant proteins, specific substitutions at Lys-62 of S28 (Lys→Asn, Thr, or Gln) increased translational accuracy and antibiotic resistance, while Lys-62→Arg decreased accuracy. RPS28 and S4 (SUP44) interact functionally to control translational accuracy, and S28 mutations can partially reverse the translational infidelity caused by SUP44.","method":"In vitro cell-free translation system (poly(U)-directed), genetic epistasis with SUP44 alleles, antibiotic sensitivity assays, site-directed mutagenesis","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — quantitative in vitro translation assay with mutagenesis, confirmed by genetic epistasis, replicated across two labs (PMID 8950190 and 7498767)","pmids":["8950190"],"is_preprint":false},{"year":2010,"finding":"RNase H site-specific cleavage of the human 40S ribosomal subunit and mass spectrometry of the resulting head fragment showed that eukaryote-specific RPS28 (S28e) localizes to the head of the 40S subunit. Recombinant S28e binds specifically to the 3' major domain of 18S rRNA with high affinity (Ka = 8.0±0.5×10⁹ M⁻¹).","method":"RNase H cleavage of 40S subunit, mass spectrometry, in vitro RNA-binding assay (Ka measurement) with recombinant protein","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct biochemical fractionation, mass spectrometry, and quantitative in vitro binding assay with recombinant protein in a single study","pmids":["20951136"],"is_preprint":false},{"year":2013,"finding":"Yeast Edc3 protein directly and tightly binds to the globular core of Rps28 through a specific motif present only in Edc3 proteins from Saccharomycetaceae yeast. This Rps28-Edc3 interaction is exclusively required for the autoregulatory feedback loop controlling RPS28B mRNA decay but is dispensable for Edc3's general mRNA decay functions and YRA1 pre-mRNA decay regulation.","method":"Direct binding assay (in vitro), functional genetic analysis of Edc3 motif mutants, mRNA decay assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct in vitro binding combined with functional mutant analysis distinguishing RPS28B-specific from general Edc3 functions, single lab with multiple orthogonal methods","pmids":["23956223"],"is_preprint":false},{"year":2014,"finding":"De novo mutations affecting the RPS28 start codon (affecting translation initiation) were found in two unrelated probands with Diamond-Blackfan anemia combined with mandibulofacial dysostosis, identifying RPS28 as a novel DBA disease gene and implicating its loss in impaired ribosome biogenesis leading to defective erythropoiesis and abnormal development.","method":"Whole-exome sequencing, Sanger sequencing, clinical phenotyping","journal":"American journal of medical genetics. Part A","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — genetic identification in two independent families with consistent phenotype, but no direct functional rescue or molecular mechanism experiment in the paper","pmids":["24942156"],"is_preprint":false},{"year":2019,"finding":"The tRNA-derived small RNA LeuCAG3'tsRNA regulates RPS28 levels by binding to both the coding sequence (CDS) and 3' UTR of RPS28 mRNA, altering its secondary structure and enhancing translation at a post-initiation step. The functional 3' UTR target site is primate-specific while the CDS site is conserved across vertebrates, and this mechanism also operates in mouse Rps28.","method":"RNA secondary structure analysis, reporter assays, ribosome profiling, site-directed mutation of binding sites, species conservation analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (structure probing, reporter assays, cross-species validation in mouse), single lab with rigorous controls establishing post-initiation mechanism","pmids":["31851915"],"is_preprint":false},{"year":2021,"finding":"In Drosophila, muscle-specific overexpression of the RpS28a variant (at germline-like levels) promotes synthesis of a specific subset of proteins with anti-aging roles and decreases early mortality, demonstrating that RpS28 contributes to a specialized ribosome that selectively regulates the muscle proteome.","method":"Tissue-specific transgenic overexpression, proteomics (mass spectrometry), lifespan analysis","journal":"G3 (Bethesda, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics combined with functional overexpression in defined tissue, single lab, ortholog study in Drosophila","pmids":["33974070"],"is_preprint":false},{"year":2025,"finding":"FBL (Fibrillarin) knockdown in triple-negative breast cancer cells reduces RPS28 incorporation into ribosomes (confirmed by altered 18S rRNA structure via SHAPE); silencing RPS28 independently impairs oncogenic traits and reduces translation of MTA1, IRAK1, and TMSB10, establishing that RPS28 incorporation into ribosomes is required for selective translation of oncogenes downstream of FBL-mediated rRNA 2'-O-methylation.","method":"siRNA knockdown, RiboMethSeq, SHAPE (RNA structure probing), ribosome fractionation, translation efficiency measurement","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (SHAPE, RiboMethSeq, knockdown with phenotypic readouts) in a single lab; peer-reviewed publication","pmids":["41260515"],"is_preprint":false}],"current_model":"RPS28 is a eukaryote-specific protein of the 40S ribosomal subunit head that binds the 3' major domain of 18S rRNA, controls translational accuracy at the decoding center (with Lys-62 being critical), is regulated post-translationally via a LeuCAG3'tsRNA that enhances its mRNA translation at a post-initiation step, participates in an Edc3-mediated autoregulatory mRNA decay feedback loop in yeast, and when incorporated into ribosomes (dependent on FBL-catalyzed rRNA 2'-O-methylation) enables selective translation of a specific subset of proteins including oncogenes; loss-of-function mutations cause Diamond-Blackfan anemia with craniofacial anomalies."},"narrative":{"mechanistic_narrative":"RPS28 is a small, eukaryote-specific structural protein of the 40S ribosomal subunit head that contributes to translational accuracy and selective mRNA translation [PMID:947902, PMID:7498767]. It binds with high affinity to the 3' major domain of 18S rRNA and localizes to the head of the 40S subunit, where it sits near the decoding center [PMID:20951136]. Genetic and in vitro translation analyses in yeast established RPS28 as a regulator of translational fidelity that acts in functional concert with ribosomal protein S4/SUP44, with Lys-62 being a critical residue whose substitution shifts decoding accuracy and antibiotic sensitivity [PMID:7498767, PMID:8950190]. RPS28 levels are tuned post-transcriptionally: a tRNA-derived fragment, LeuCAG3'tsRNA, binds the RPS28 mRNA coding sequence and 3' UTR and enhances its translation at a post-initiation step [PMID:31851915], while in yeast an Edc3-bound autoregulatory feedback loop directs RPS28B mRNA decay through direct binding to the Rps28 core [PMID:23956223]. Incorporation of RPS28 into ribosomes, downstream of FBL-catalyzed rRNA 2'-O-methylation, enables selective translation of a defined protein subset including oncogenes such as MTA1, IRAK1, and TMSB10, indicating a specialized-ribosome function [PMID:41260515]. De novo mutations affecting the RPS28 start codon cause Diamond-Blackfan anemia with mandibulofacial dysostosis [PMID:24942156].","teleology":[{"year":1976,"claim":"Establishing whether S28 was a genuine ribosomal constituent was the first requirement; purification from native 40S subunits defined it as a structural small-subunit protein.","evidence":"Protein purification and amino acid composition analysis from rat liver 40S subunits","pmids":["947902"],"confidence":"Medium","gaps":["No sequence or gene identity","No functional role assigned","Position within the subunit unknown"]},{"year":1991,"claim":"Defining the primary structure and gene copy number converted the purified protein into a molecularly tractable entity and tied it to a yeast ortholog.","evidence":"cDNA sequencing and genomic Southern blot in rat, with homology to S. cerevisiae S33","pmids":["1679328"],"confidence":"Medium","gaps":["No functional consequence of sequence features","rRNA contacts unknown","No structural model"]},{"year":1996,"claim":"Whether RPS28 actively shapes decoding rather than merely scaffolding was answered by showing that specific substitutions, notably at Lys-62, bidirectionally alter translational accuracy and that RPS28 acts with S4/SUP44.","evidence":"Yeast genetic suppressor and antibiotic assays plus poly(U)-directed cell-free translation with mutant ribosomes","pmids":["7498767","8950190"],"confidence":"High","gaps":["Structural basis of Lys-62 effect on the decoding center not resolved","Mechanism of functional coupling to S4 unknown","Conservation of effect in mammalian ribosomes not tested"]},{"year":2010,"claim":"Localizing RPS28 and defining its rRNA target established the physical basis for its decoding-center role in the human ribosome.","evidence":"RNase H cleavage and mass spectrometry of human 40S plus quantitative in vitro binding of recombinant S28e to the 3' major domain of 18S rRNA","pmids":["20951136"],"confidence":"High","gaps":["Atomic-resolution contacts not defined","Assembly order into the subunit unknown","Link between binding site and fidelity not directly tested"]},{"year":2013,"claim":"How RPS28 abundance is homeostatically controlled was partly answered by identifying a direct Edc3-Rps28 interaction driving an autoregulatory mRNA decay loop in yeast.","evidence":"In vitro direct binding and functional analysis of Edc3 motif mutants with RPS28B mRNA decay assays","pmids":["23956223"],"confidence":"High","gaps":["Whether an equivalent autoregulatory loop exists in mammals unknown","Structural detail of the Edc3-binding motif on Rps28 not resolved","Trigger sensing excess Rps28 not defined"]},{"year":2014,"claim":"Linking RPS28 to human disease, start-codon mutations were identified as a cause of Diamond-Blackfan anemia with craniofacial anomalies, implicating defective ribosome function in erythropoiesis and development.","evidence":"Whole-exome and Sanger sequencing of two unrelated DBA probands with mandibulofacial dysostosis","pmids":["24942156"],"confidence":"Medium","gaps":["No functional rescue or molecular mechanism experiment","Tissue-specific basis of erythroid sensitivity unexplained","Quantitative effect on RPS28 protein not measured"]},{"year":2019,"claim":"A post-transcriptional regulator of RPS28 in mammals was identified, showing a tRNA-derived small RNA enhances RPS28 mRNA translation at a post-initiation step via structural remodeling.","evidence":"RNA structure probing, reporter assays, ribosome profiling, binding-site mutagenesis, and cross-species validation in mouse","pmids":["31851915"],"confidence":"High","gaps":["Mechanism of post-initiation enhancement at the ribosome unresolved","Physiological contexts engaging this regulation unclear","Protein machinery mediating tsRNA action not identified"]},{"year":2021,"claim":"Whether RPS28 could confer ribosome specialization was supported by showing muscle-specific RpS28a overexpression selectively reshapes the proteome and reduces early mortality in Drosophila.","evidence":"Tissue-specific transgenic overexpression with proteomics and lifespan analysis in Drosophila","pmids":["33974070"],"confidence":"Medium","gaps":["Molecular basis of selective translation not defined","Relevance to mammalian tissues untested","Overexpression rather than physiological-level effect"]},{"year":2025,"claim":"Connecting RPS28 incorporation to rRNA modification and oncogenic translation showed that FBL-dependent 2'-O-methylation controls RPS28 loading into ribosomes, which is required for selective translation of specific oncogenes.","evidence":"siRNA knockdown, RiboMethSeq, SHAPE, ribosome fractionation, and translation efficiency in triple-negative breast cancer cells","pmids":["41260515"],"confidence":"Medium","gaps":["How methylation regulates RPS28 incorporation mechanistically unresolved","Generality beyond TNBC unknown","Direct demonstration of selective decoding by RPS28-containing ribosomes lacking"]},{"year":null,"claim":"It remains unknown how RPS28's rRNA-binding position and Lys-62 chemistry mechanistically govern decoding-center fidelity and how this links to its emerging role in specialized, selective translation.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution model coupling RPS28 contacts to decoding accuracy","No unified mechanism connecting fidelity control to oncogene-selective translation","Mammalian autoregulation of RPS28 abundance uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[4]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,4]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[2,3,7]}],"localization":[{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[0,4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,3,7,9]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[5]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[6,9]}],"complexes":["40S ribosomal subunit"],"partners":["EDC3","FBL","RPS4/SUP44"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P62857","full_name":"Small ribosomal subunit protein eS28","aliases":["40S ribosomal protein S28"],"length_aa":69,"mass_kda":7.8,"function":"Component of the small ribosomal subunit (PubMed:23636399, PubMed:25901680, PubMed:25957688). The ribosome is a large ribonucleoprotein complex responsible for the synthesis of proteins in the cell (PubMed:23636399, PubMed:25901680, PubMed:25957688). Part of the small subunit (SSU) processome, first precursor of the small eukaryotic ribosomal subunit. During the assembly of the SSU processome in the nucleolus, many ribosome biogenesis factors, an RNA chaperone and ribosomal proteins associate with the nascent pre-rRNA and work in concert to generate RNA folding, modifications, rearrangements and cleavage as well as targeted degradation of pre-ribosomal RNA by the RNA exosome (PubMed:34516797)","subcellular_location":"Cytoplasm, cytosol; Cytoplasm; Rough endoplasmic reticulum; Nucleus, nucleolus","url":"https://www.uniprot.org/uniprotkb/P62857/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RPS28","classification":"Common Essential","n_dependent_lines":1089,"n_total_lines":1090,"dependency_fraction":0.9990825688073395},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CAPRIN1","stoichiometry":10.0},{"gene":"DDX21","stoichiometry":10.0},{"gene":"EIF2S3","stoichiometry":10.0},{"gene":"EIF3B","stoichiometry":10.0},{"gene":"ENY2","stoichiometry":10.0},{"gene":"G3BP1","stoichiometry":10.0},{"gene":"GSPT1","stoichiometry":10.0},{"gene":"METAP2","stoichiometry":10.0},{"gene":"NCAPH","stoichiometry":10.0},{"gene":"RACK1","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/RPS28","total_profiled":1310},"omim":[{"mim_id":"613309","title":"DIAMOND-BLACKFAN ANEMIA 10; DBA10","url":"https://www.omim.org/entry/613309"},{"mim_id":"606164","title":"DIAMOND-BLACKFAN ANEMIA 15 WITH MANDIBULOFACIAL DYSOSTOSIS; DBA15","url":"https://www.omim.org/entry/606164"},{"mim_id":"603701","title":"RIBOSOMAL PROTEIN S26; RPS26","url":"https://www.omim.org/entry/603701"},{"mim_id":"603685","title":"RIBOSOMAL PROTEIN S28; RPS28","url":"https://www.omim.org/entry/603685"},{"mim_id":"300946","title":"DIAMOND-BLACKFAN ANEMIA 14 WITH MANDIBULOFACIAL DYSOSTOSIS; DBA14","url":"https://www.omim.org/entry/300946"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RPS28"},"hgnc":{"alias_symbol":["S28","eS28"],"prev_symbol":[]},"alphafold":{"accession":"P62857","domains":[{"cath_id":"2.40.50.140","chopping":"9-57","consensus_level":"high","plddt":94.6802,"start":9,"end":57}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P62857","model_url":"https://alphafold.ebi.ac.uk/files/AF-P62857-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P62857-F1-predicted_aligned_error_v6.png","plddt_mean":91.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RPS28","jax_strain_url":"https://www.jax.org/strain/search?query=RPS28"},"sequence":{"accession":"P62857","fasta_url":"https://rest.uniprot.org/uniprotkb/P62857.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P62857/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P62857"}},"corpus_meta":[{"pmid":"21282660","id":"PMC_21282660","title":"Histone code pathway involving H3 S28 phosphorylation and K27 acetylation activates transcription and antagonizes polycomb silencing.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21282660","citation_count":139,"is_preprint":false},{"pmid":"24942156","id":"PMC_24942156","title":"Diamond-Blackfan anemia with mandibulofacial dystostosis is heterogeneous, including the novel DBA genes TSR2 and RPS28.","date":"2014","source":"American journal of medical genetics. 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phosphorylation","date":"2024-09-09","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.09.612097","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.29.679131","title":"A time-resolved atlas of histone modifications during mitotic entry","date":"2025-09-30","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.29.679131","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13260,"output_tokens":2632,"usd":0.03963,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9889,"output_tokens":3182,"usd":0.064497,"stage2_stop_reason":"end_turn"},"total_usd":0.104127,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1976,\n      \"finding\": \"RPS28 (S28) was isolated and purified from rat liver 40S ribosomal subunit by ion-exchange chromatography and gel filtration; its molecular weight and amino acid composition were characterized, establishing it as a structural component of the small ribosomal subunit.\",\n      \"method\": \"Protein purification (ion-exchange chromatography, gel filtration), SDS-PAGE, amino acid composition analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical purification and characterization from native ribosome, single lab, foundational isolation study\",\n      \"pmids\": [\"947902\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"The primary amino acid sequence of rat ribosomal protein S28 (RPS28) was determined: 69 amino acids, molecular weight 7,836 Da, encoded by 8–10 gene copies, with an mRNA of ~450 nucleotides; rat S28 is homologous to Saccharomyces cerevisiae S33.\",\n      \"method\": \"cDNA sequencing, Southern blot hybridization, sequence homology analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cDNA sequencing with genomic Southern blot, single lab, two orthogonal methods\",\n      \"pmids\": [\"1679328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"In yeast, different mutations in RPS28 (encoded by RPS28A and RPS28B) can have diametrically opposite effects on translational accuracy: substitutions in the diverged N-terminal portion cause nonsense suppression or antibiotic sensitivity, while substitutions in the conserved C-terminal portion counteract SUP44/SUP46-associated antibiotic sensitivity, establishing RPS28 as a regulator of translational fidelity at the decoding center.\",\n      \"method\": \"Site-directed and random mutagenesis, genetic suppressor analysis, antibiotic sensitivity assays\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple mutant alleles tested with orthogonal genetic and biochemical readouts, replicated across two independent studies (PMID 7498767 and 8950190)\",\n      \"pmids\": [\"7498767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Using a poly(U)-dependent cell-free translation system with yeast ribosomes bearing RPS28 mutant proteins, specific substitutions at Lys-62 of S28 (Lys→Asn, Thr, or Gln) increased translational accuracy and antibiotic resistance, while Lys-62→Arg decreased accuracy. RPS28 and S4 (SUP44) interact functionally to control translational accuracy, and S28 mutations can partially reverse the translational infidelity caused by SUP44.\",\n      \"method\": \"In vitro cell-free translation system (poly(U)-directed), genetic epistasis with SUP44 alleles, antibiotic sensitivity assays, site-directed mutagenesis\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — quantitative in vitro translation assay with mutagenesis, confirmed by genetic epistasis, replicated across two labs (PMID 8950190 and 7498767)\",\n      \"pmids\": [\"8950190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RNase H site-specific cleavage of the human 40S ribosomal subunit and mass spectrometry of the resulting head fragment showed that eukaryote-specific RPS28 (S28e) localizes to the head of the 40S subunit. Recombinant S28e binds specifically to the 3' major domain of 18S rRNA with high affinity (Ka = 8.0±0.5×10⁹ M⁻¹).\",\n      \"method\": \"RNase H cleavage of 40S subunit, mass spectrometry, in vitro RNA-binding assay (Ka measurement) with recombinant protein\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct biochemical fractionation, mass spectrometry, and quantitative in vitro binding assay with recombinant protein in a single study\",\n      \"pmids\": [\"20951136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Yeast Edc3 protein directly and tightly binds to the globular core of Rps28 through a specific motif present only in Edc3 proteins from Saccharomycetaceae yeast. This Rps28-Edc3 interaction is exclusively required for the autoregulatory feedback loop controlling RPS28B mRNA decay but is dispensable for Edc3's general mRNA decay functions and YRA1 pre-mRNA decay regulation.\",\n      \"method\": \"Direct binding assay (in vitro), functional genetic analysis of Edc3 motif mutants, mRNA decay assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct in vitro binding combined with functional mutant analysis distinguishing RPS28B-specific from general Edc3 functions, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"23956223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"De novo mutations affecting the RPS28 start codon (affecting translation initiation) were found in two unrelated probands with Diamond-Blackfan anemia combined with mandibulofacial dysostosis, identifying RPS28 as a novel DBA disease gene and implicating its loss in impaired ribosome biogenesis leading to defective erythropoiesis and abnormal development.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing, clinical phenotyping\",\n      \"journal\": \"American journal of medical genetics. Part A\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — genetic identification in two independent families with consistent phenotype, but no direct functional rescue or molecular mechanism experiment in the paper\",\n      \"pmids\": [\"24942156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The tRNA-derived small RNA LeuCAG3'tsRNA regulates RPS28 levels by binding to both the coding sequence (CDS) and 3' UTR of RPS28 mRNA, altering its secondary structure and enhancing translation at a post-initiation step. The functional 3' UTR target site is primate-specific while the CDS site is conserved across vertebrates, and this mechanism also operates in mouse Rps28.\",\n      \"method\": \"RNA secondary structure analysis, reporter assays, ribosome profiling, site-directed mutation of binding sites, species conservation analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (structure probing, reporter assays, cross-species validation in mouse), single lab with rigorous controls establishing post-initiation mechanism\",\n      \"pmids\": [\"31851915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In Drosophila, muscle-specific overexpression of the RpS28a variant (at germline-like levels) promotes synthesis of a specific subset of proteins with anti-aging roles and decreases early mortality, demonstrating that RpS28 contributes to a specialized ribosome that selectively regulates the muscle proteome.\",\n      \"method\": \"Tissue-specific transgenic overexpression, proteomics (mass spectrometry), lifespan analysis\",\n      \"journal\": \"G3 (Bethesda, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics combined with functional overexpression in defined tissue, single lab, ortholog study in Drosophila\",\n      \"pmids\": [\"33974070\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBL (Fibrillarin) knockdown in triple-negative breast cancer cells reduces RPS28 incorporation into ribosomes (confirmed by altered 18S rRNA structure via SHAPE); silencing RPS28 independently impairs oncogenic traits and reduces translation of MTA1, IRAK1, and TMSB10, establishing that RPS28 incorporation into ribosomes is required for selective translation of oncogenes downstream of FBL-mediated rRNA 2'-O-methylation.\",\n      \"method\": \"siRNA knockdown, RiboMethSeq, SHAPE (RNA structure probing), ribosome fractionation, translation efficiency measurement\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (SHAPE, RiboMethSeq, knockdown with phenotypic readouts) in a single lab; peer-reviewed publication\",\n      \"pmids\": [\"41260515\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RPS28 is a eukaryote-specific protein of the 40S ribosomal subunit head that binds the 3' major domain of 18S rRNA, controls translational accuracy at the decoding center (with Lys-62 being critical), is regulated post-translationally via a LeuCAG3'tsRNA that enhances its mRNA translation at a post-initiation step, participates in an Edc3-mediated autoregulatory mRNA decay feedback loop in yeast, and when incorporated into ribosomes (dependent on FBL-catalyzed rRNA 2'-O-methylation) enables selective translation of a specific subset of proteins including oncogenes; loss-of-function mutations cause Diamond-Blackfan anemia with craniofacial anomalies.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RPS28 is a small, eukaryote-specific structural protein of the 40S ribosomal subunit head that contributes to translational accuracy and selective mRNA translation [#0, #2]. It binds with high affinity to the 3' major domain of 18S rRNA and localizes to the head of the 40S subunit, where it sits near the decoding center [#4]. Genetic and in vitro translation analyses in yeast established RPS28 as a regulator of translational fidelity that acts in functional concert with ribosomal protein S4/SUP44, with Lys-62 being a critical residue whose substitution shifts decoding accuracy and antibiotic sensitivity [#2, #3]. RPS28 levels are tuned post-transcriptionally: a tRNA-derived fragment, LeuCAG3'tsRNA, binds the RPS28 mRNA coding sequence and 3' UTR and enhances its translation at a post-initiation step [#7], while in yeast an Edc3-bound autoregulatory feedback loop directs RPS28B mRNA decay through direct binding to the Rps28 core [#5]. Incorporation of RPS28 into ribosomes, downstream of FBL-catalyzed rRNA 2'-O-methylation, enables selective translation of a defined protein subset including oncogenes such as MTA1, IRAK1, and TMSB10, indicating a specialized-ribosome function [#9]. De novo mutations affecting the RPS28 start codon cause Diamond-Blackfan anemia with mandibulofacial dysostosis [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 1976,\n      \"claim\": \"Establishing whether S28 was a genuine ribosomal constituent was the first requirement; purification from native 40S subunits defined it as a structural small-subunit protein.\",\n      \"evidence\": \"Protein purification and amino acid composition analysis from rat liver 40S subunits\",\n      \"pmids\": [\"947902\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No sequence or gene identity\", \"No functional role assigned\", \"Position within the subunit unknown\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Defining the primary structure and gene copy number converted the purified protein into a molecularly tractable entity and tied it to a yeast ortholog.\",\n      \"evidence\": \"cDNA sequencing and genomic Southern blot in rat, with homology to S. cerevisiae S33\",\n      \"pmids\": [\"1679328\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional consequence of sequence features\", \"rRNA contacts unknown\", \"No structural model\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Whether RPS28 actively shapes decoding rather than merely scaffolding was answered by showing that specific substitutions, notably at Lys-62, bidirectionally alter translational accuracy and that RPS28 acts with S4/SUP44.\",\n      \"evidence\": \"Yeast genetic suppressor and antibiotic assays plus poly(U)-directed cell-free translation with mutant ribosomes\",\n      \"pmids\": [\"7498767\", \"8950190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Lys-62 effect on the decoding center not resolved\", \"Mechanism of functional coupling to S4 unknown\", \"Conservation of effect in mammalian ribosomes not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Localizing RPS28 and defining its rRNA target established the physical basis for its decoding-center role in the human ribosome.\",\n      \"evidence\": \"RNase H cleavage and mass spectrometry of human 40S plus quantitative in vitro binding of recombinant S28e to the 3' major domain of 18S rRNA\",\n      \"pmids\": [\"20951136\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution contacts not defined\", \"Assembly order into the subunit unknown\", \"Link between binding site and fidelity not directly tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"How RPS28 abundance is homeostatically controlled was partly answered by identifying a direct Edc3-Rps28 interaction driving an autoregulatory mRNA decay loop in yeast.\",\n      \"evidence\": \"In vitro direct binding and functional analysis of Edc3 motif mutants with RPS28B mRNA decay assays\",\n      \"pmids\": [\"23956223\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether an equivalent autoregulatory loop exists in mammals unknown\", \"Structural detail of the Edc3-binding motif on Rps28 not resolved\", \"Trigger sensing excess Rps28 not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linking RPS28 to human disease, start-codon mutations were identified as a cause of Diamond-Blackfan anemia with craniofacial anomalies, implicating defective ribosome function in erythropoiesis and development.\",\n      \"evidence\": \"Whole-exome and Sanger sequencing of two unrelated DBA probands with mandibulofacial dysostosis\",\n      \"pmids\": [\"24942156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional rescue or molecular mechanism experiment\", \"Tissue-specific basis of erythroid sensitivity unexplained\", \"Quantitative effect on RPS28 protein not measured\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A post-transcriptional regulator of RPS28 in mammals was identified, showing a tRNA-derived small RNA enhances RPS28 mRNA translation at a post-initiation step via structural remodeling.\",\n      \"evidence\": \"RNA structure probing, reporter assays, ribosome profiling, binding-site mutagenesis, and cross-species validation in mouse\",\n      \"pmids\": [\"31851915\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of post-initiation enhancement at the ribosome unresolved\", \"Physiological contexts engaging this regulation unclear\", \"Protein machinery mediating tsRNA action not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Whether RPS28 could confer ribosome specialization was supported by showing muscle-specific RpS28a overexpression selectively reshapes the proteome and reduces early mortality in Drosophila.\",\n      \"evidence\": \"Tissue-specific transgenic overexpression with proteomics and lifespan analysis in Drosophila\",\n      \"pmids\": [\"33974070\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of selective translation not defined\", \"Relevance to mammalian tissues untested\", \"Overexpression rather than physiological-level effect\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connecting RPS28 incorporation to rRNA modification and oncogenic translation showed that FBL-dependent 2'-O-methylation controls RPS28 loading into ribosomes, which is required for selective translation of specific oncogenes.\",\n      \"evidence\": \"siRNA knockdown, RiboMethSeq, SHAPE, ribosome fractionation, and translation efficiency in triple-negative breast cancer cells\",\n      \"pmids\": [\"41260515\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How methylation regulates RPS28 incorporation mechanistically unresolved\", \"Generality beyond TNBC unknown\", \"Direct demonstration of selective decoding by RPS28-containing ribosomes lacking\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how RPS28's rRNA-binding position and Lys-62 chemistry mechanistically govern decoding-center fidelity and how this links to its emerging role in specialized, selective translation.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic-resolution model coupling RPS28 contacts to decoding accuracy\", \"No unified mechanism connecting fidelity control to oncogene-selective translation\", \"Mammalian autoregulation of RPS28 abundance uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [2, 3, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 3, 7, 9]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [6, 9]}\n    ],\n    \"complexes\": [\"40S ribosomal subunit\"],\n    \"partners\": [\"EDC3\", \"FBL\", \"RPS4/SUP44\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}