{"gene":"RPS2","run_date":"2026-06-10T07:46:27","timeline":{"discoveries":[{"year":2007,"finding":"PRMT3 (a type I arginine methyltransferase) directly methylates ribosomal protein rpS2 (RPS2/uS5) at arginine residues; PRMT3 is tethered to ribosomes via its interaction with rpS2, which is also its substrate. In PRMT3-knockout mice, rpS2 is hypomethylated, establishing rpS2 as a bona fide in vivo PRMT3 substrate that cannot be compensated by other PRMTs.","method":"Targeted gene disruption (PRMT3 knockout mice), Western blot for methylarginine, ribosome fractionation (polysome profiling), co-fractionation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic knockout with direct biochemical readout (hypomethylation), replicated across multiple assays in a single rigorous study","pmids":["17439947"],"is_preprint":false},{"year":2009,"finding":"In budding yeast Saccharomyces cerevisiae, which lacks a zinc-finger-containing Rmt3/PRMT3 homolog, Rps2 is partially modified to asymmetric dimethylarginine and monomethylarginine by the major arginine methyltransferase Rmt1, demonstrating organism-specific methyltransferase usage for the same substrate.","method":"Arginine methylation assays, methyltransferase deletion strains, mass spectrometry/biochemical detection of methylarginine","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vivo genetic evidence (rmt1 deletion) with biochemical detection, single lab","pmids":["20035717"],"is_preprint":false},{"year":2008,"finding":"In fission yeast, Rps2 is required for nuclear export competence of pre-40S ribosomal subunits; its depletion causes retention of pre-40S particles in the nucleolus, blocks 40S subunit production, and impairs cleavage at site A2 within 32S pre-rRNA.","method":"Genetic depletion of Rps2 in Schizosaccharomyces pombe, pre-rRNA processing analysis, rRNA pulse-chase assays, nucleolar retention assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic depletion with multiple orthogonal readouts (rRNA processing, pulse-chase, localization), establishing a specific mechanistic role","pmids":["18820293"],"is_preprint":false},{"year":2018,"finding":"Human zinc finger protein ZNF277 forms an extraribosomal complex with uS5 (RPS2) in the cytoplasm and nucleolus using a C2H2-type zinc finger domain. ZNF277 and PRMT3 compete for uS5 binding: PRMT3 overexpression inhibits ZNF277-uS5 complex formation, and ZNF277 depletion increases uS5-PRMT3 levels. ZNF277 recognizes nascent uS5 co-translationally.","method":"Quantitative proteomics (affinity purification-MS), Co-IP in human cells, proximity ligation assay, overexpression/depletion experiments, subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — quantitative proteomics plus reciprocal Co-IP plus competition experiments, multiple orthogonal methods in a single study","pmids":["30530495"],"is_preprint":false},{"year":2019,"finding":"Tsr4 is a dedicated cytoplasmic chaperone for Rps2 (uS5) in S. cerevisiae. Tsr4 associates with Rps2 co-translationally, requires the eukaryote-specific N-terminal extension of Rps2 for interaction, promotes Rps2 solubility and expression, and is restricted to the cytoplasm despite Rps2 assembling into nuclear pre-40S particles.","method":"Co-translational co-IP, genetic depletion/perturbation of Tsr4, ribosome biogenesis assays, subcellular fractionation, yeast genetics","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-translational association established with multiple approaches, genetic phenocopy of Rps2 depletion, localization confirmed by fractionation","pmids":["31182640"],"is_preprint":false},{"year":2020,"finding":"Human PDCD2 functions as a dedicated ribosomal protein chaperone for uS5 (RPS2); PDCD2-uS5 complex is assembled co-translationally. Loss of PDCD2 impairs accumulation of soluble uS5 and its incorporation into 40S ribosomal subunits, causing defects in small ribosomal subunit synthesis that phenocopy uS5 deficiency.","method":"Quantitative proteomics (affinity purification-MS), co-translational Co-IP, PDCD2 knockdown with ribosome biogenesis readouts, polysome profiling","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — quantitative proteomics, co-translational assembly evidence, genetic loss-of-function with multiple ribosome biogenesis phenotypes, orthologous to yeast Tsr4","pmids":["33245768"],"is_preprint":false},{"year":2016,"finding":"In Drosophila, Zfrp8/PDCD2 directly interacts with RpS2 (uS5) of the 40S small ribosomal subunit. Zfrp8/PDCD2 regulates cytoplasmic levels of 40S ribosomal subunit components and controls cytoplasmic localization of specific mRNAs; knockdown causes nuclear accumulation of specific mRNAs and TE transcripts, suggesting Zfrp8 functions at late stages of ribosome assembly.","method":"Co-IP (Zfrp8-RpS2 pulldown), fluorescent tagging of ribosomal proteins, genetic knockdown (RNAi), RNA localization assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct Co-IP plus functional genetic knockdown, single lab, multiple readouts","pmids":["26807849"],"is_preprint":false},{"year":2022,"finding":"Ribosomal protein uS5/Rps2 residues at the mRNA entry channel of the 40S subunit influence start codon recognition in vivo; nonlethal substitutions of conserved Rps2 residues reduce bulk translation initiation, increase discrimination against poor initiation codons (near-cognate UUG and suboptimal Kozak context AUG), resembling substitutions in uS3/Rps3 and initiation factors eIF1/eIF1A.","method":"Site-directed mutagenesis of Rps2 residues, yeast genetic assays for translation initiation fidelity (UUG initiation reporters, Kozak context reporters), epistasis with known initiation mutants","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis combined with multiple in vivo reporter assays dissecting distinct mechanisms, single lab but multiple orthogonal genetic readouts","pmids":["34791232"],"is_preprint":false},{"year":2017,"finding":"Mutations in the loop 2 region (residues 20–31) of ribosomal protein uS5 in E. coli confer spectinomycin resistance and affect translational fidelity; a minority of loop 2 mutants also show altered rRNA processing or ribosome biogenesis defects, demonstrating that this region participates in subunit assembly and maintenance of translational accuracy.","method":"Site-directed mutagenesis (21 unique mutants), spectinomycin sensitivity assays, translational fidelity reporters, rRNA processing analysis","journal":"Antimicrobial agents and chemotherapy","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with multiple functional readouts (antibiotic resistance, fidelity, rRNA processing), replicated across multiple mutants","pmids":["27855073"],"is_preprint":false},{"year":2024,"finding":"In S. cerevisiae, the cyclin-dependent kinase pathway (via Ypk2) phosphorylates Ser176 of uS5 (RPS2), which is located at the uS4-uS5 interface; phospho-Ser176 forms a salt bridge with Arg57 of uS4, strengthening the interface and increasing decoding selectivity. A second kinase pathway involving TORC1 and Pkc1 opposes this phosphorylation, indicating that translational accuracy is dynamically regulated by competing phosphorylation on uS5.","method":"Site-directed mutagenesis of Ser176 and Arg57, genetic epistasis analysis with kinase mutants (ctk1, ypk2, TORC1, pkc1), translational fidelity reporters","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — mutagenesis and epistasis in single lab; phosphorylation-salt bridge model supported by genetic data but not confirmed by direct structural evidence in this study","pmids":["38340338"],"is_preprint":false},{"year":2023,"finding":"Nuclear import of Rps2 (uS5) in yeast requires two distinct import signals: (1) an internal region (amino acids 76–145) that interacts with the importin-β Pse1, with Arg95, Arg97, and Lys99 being critical determinants; (2) an N-terminal region (amino acids 10–28) containing basic residues that constitutes a second import pathway. Both pathways function independently of the dedicated chaperone Tsr4.","method":"GFP reporter nuclear import assays, deletion/mutation analysis of Rps2 import signals, Co-IP with Pse1, genetic dissection in yeast","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with reporter assays and interaction data, single lab with multiple mutants tested","pmids":["37509163"],"is_preprint":false},{"year":2022,"finding":"Heliangin (a sesquiterpene lactone) covalently binds to the C222 site of RPS2, disrupting pre-rRNA metabolic processes, causing nucleolar stress, and activating the ribosomal proteins–MDM2–p53 pathway with consequent p53 stabilization in NPM1-mutant AML cells.","method":"Quantitative thiol reactivity platform screening, molecular biology validation, covalent binding assays, pre-rRNA processing assays, Western blot for p53/MDM2","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — chemical proteomics identification of binding site plus functional validation in cells, single lab","pmids":["36873185"],"is_preprint":false},{"year":2010,"finding":"RPS2 specifically binds pre-let-7a-1 RNA and blocks its processing to mature let-7a/let-7f miRNA in prostate cancer cells; this was shown by EMSA, antibody supershift assay, and immunoprecipitation. Overexpression of RPS2 correlates with loss of let-7a and elevated ras/c-myc, while RPS2 knockdown restores let-7a and reduces oncogene expression and tumorigenesis.","method":"EMSA, antibody supershift assay, immunoprecipitation, stable transfection/shRNA knockdown, Northern blot, immunofluorescence, SCID mouse tumor model","journal":"Molecular cancer research : MCR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct RNA-binding shown by EMSA and IP, functional validation in multiple cell lines and in vivo, single lab","pmids":["21148031"],"is_preprint":false},{"year":2025,"finding":"RACK1 stabilizes RPS2 by inhibiting ubiquitin-mediated proteasomal degradation of RPS2; RACK1 knockdown increases RPS2 ubiquitination and accelerates its degradation (reversed by MG132). Both RACK1 and RPS2 positively regulate the NF-κB pathway, and RPS2 overexpression partially rescues the NF-κB inhibition caused by RACK1 knockdown in glioma cells.","method":"Co-immunoprecipitation, ubiquitination assays, MG132 proteasome inhibitor treatment, Western blot, NF-κB luciferase reporter assay, siRNA knockdown","journal":"Molecular biology reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct Co-IP and ubiquitination assays, functional rescue experiment, single lab","pmids":["40522528"],"is_preprint":false},{"year":2026,"finding":"A 30-amino-acid N-terminal region of uS5 (RPS2) is necessary and sufficient for interaction with its dedicated chaperone PDCD2; a conserved FxxGFG motif within this region mediates hydrophobic interactions with PDCD2. An 11-amino-acid uS5-derived peptide that inhibits PDCD2-uS5 interaction impairs cancer cell viability.","method":"Affinity purification assays, structural modeling, complementation-based biosensor in human cells and cell extracts, deletion/mutation analysis, cell viability assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical and cell-based interaction mapping with mutagenesis, single lab, functional consequence demonstrated","pmids":["41933732"],"is_preprint":false},{"year":2025,"finding":"In the absence of eIF2A, ubiquitination of RPS2 (and RPS3) is specifically diminished upon ribosome stalling, and eIF2A antagonizes USP10-dependent rescue of 40S ribosomes; this places RPS2 ubiquitination in a ribosome-associated quality control pathway regulated by eIF2A.","method":"TurboID proximity labeling combined with mass spectrometry, polysome gradient fractionation, eIF2A knockout cells, dynamic SILAC mass spectrometry, 40S footprinting","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — proximity labeling MS in a preprint, single lab, mechanistic placement is indirect","pmids":[],"is_preprint":true}],"current_model":"RPS2 (uS5) is a universally conserved 40S small ribosomal subunit protein that, beyond its structural ribosomal role, is subject to a conserved extraribosomal regulatory network: it is co-translationally captured by dedicated chaperones (PDCD2/Tsr4 in eukaryotes) via its N-terminal extension, methylated at arginine residues by PRMT3 (or Rmt1 in budding yeast), and competes for binding between PRMT3 and ZNF277; its residues at the mRNA entry channel regulate translational fidelity and start codon selection, with accuracy further tuned by Ypk2/TORC1-dependent phosphorylation of Ser176 forming a salt bridge with uS4; in pre-ribosome biogenesis it is required for A2 cleavage and nuclear export competence of pre-40S particles; it is subject to ubiquitin-mediated proteasomal degradation stabilized by RACK1; it can covalently bind small molecules at C222 triggering nucleolar stress and p53 activation; and it has been reported to bind pre-let-7a-1 RNA to suppress miRNA processing in cancer cells."},"narrative":{"mechanistic_narrative":"RPS2 (uS5) is a universally conserved small (40S) ribosomal subunit protein whose residues lining the mRNA entry channel govern translation initiation fidelity and start codon selection, with nonlethal substitutions reducing bulk initiation and increasing discrimination against poor initiation codons such as near-cognate UUG and suboptimal Kozak-context AUG [PMID:34791232]; in bacteria, mutations in the loop 2 region of uS5 confer spectinomycin resistance and likewise perturb translational accuracy and ribosome assembly [PMID:27855073]. Decoding selectivity is dynamically tuned by phosphorylation of Ser176 at the uS4-uS5 interface, where a Ypk2-dependent phospho-Ser176 forms a salt bridge with Arg57 of uS4 to strengthen the interface, opposed by a TORC1/Pkc1 pathway [PMID:38340338]. Before joining the ribosome, nascent uS5 is captured co-translationally by a dedicated chaperone — Tsr4 in budding yeast and its ortholog PDCD2 (Zfrp8 in Drosophila) in metazoans — which engages a conserved N-terminal extension (a FxxGFG motif within a 30-residue region) to promote uS5 solubility and incorporation into 40S subunits [PMID:31182640, PMID:33245768, PMID:26807849, PMID:41933732]. uS5 is also arginine-methylated by PRMT3 (Rmt1 in budding yeast), which is tethered to ribosomes through uS5 itself, while the zinc-finger protein ZNF277 competes with PRMT3 for binding to nascent uS5 [PMID:17439947, PMID:20035717, PMID:30530495]. During biogenesis uS5 is required for A2 cleavage and nuclear export competence of pre-40S particles, and its own nuclear import depends on importin-β (Pse1) and a second N-terminal basic signal [PMID:18820293, PMID:37509163]. Extraribosomal and disease-associated functions reported in the corpus include RACK1-mediated protection of RPS2 from ubiquitin-proteasomal degradation coupled to NF-κB signaling [PMID:40522528], covalent ligand binding at C222 that triggers nucleolar stress and ribosomal protein–MDM2–p53 activation [PMID:36873185], and binding of pre-let-7a-1 RNA to suppress let-7 maturation in prostate cancer [PMID:21148031].","teleology":[{"year":2007,"claim":"Established that uS5/RPS2 is a physiological substrate of a specific arginine methyltransferase, defining a post-translational modification of the protein beyond its structural role.","evidence":"PRMT3-knockout mice with Western blot for methylarginine and ribosome co-fractionation","pmids":["17439947"],"confidence":"High","gaps":["Functional consequence of rpS2 arginine methylation for translation not defined","Methylated residues not mapped"]},{"year":2008,"claim":"Defined uS5 as required for a discrete step of small-subunit maturation, showing it is needed for A2 cleavage and nuclear export of pre-40S particles rather than only the mature ribosome.","evidence":"Genetic depletion in S. pombe with pre-rRNA processing, pulse-chase and nucleolar retention assays","pmids":["18820293"],"confidence":"High","gaps":["Molecular partners mediating export competence not identified","Direct role versus assembly checkpoint effect not separated"]},{"year":2009,"claim":"Showed that the same uS5 substrate is methylated by an organism-specific enzyme (Rmt1) in yeast lacking a PRMT3 homolog, indicating divergent enzyme usage on a conserved target.","evidence":"rmt1 deletion strains with biochemical detection of asymmetric dimethyl/monomethylarginine","pmids":["20035717"],"confidence":"Medium","gaps":["Only partial modification observed","Biological role of yeast Rps2 methylation unresolved"]},{"year":2010,"claim":"Identified an extraribosomal RNA-binding function in which RPS2 binds pre-let-7a-1 and blocks its maturation, linking RPS2 to oncogenic miRNA regulation.","evidence":"EMSA, supershift, IP, knockdown/overexpression in prostate cancer cells and SCID tumor model","pmids":["21148031"],"confidence":"Medium","gaps":["RNA-binding interface on RPS2 not mapped","Relationship to ribosomal pool of RPS2 unclear"]},{"year":2016,"claim":"Demonstrated a direct PDCD2-family (Zfrp8) interaction with RpS2 in metazoa and a role in late ribosome assembly and cytoplasmic mRNA localization.","evidence":"Co-IP and RNAi knockdown with RNA localization assays in Drosophila","pmids":["26807849"],"confidence":"Medium","gaps":["Co-translational nature not established in this work","Interaction interface unmapped"]},{"year":2017,"claim":"Localized translational-accuracy and assembly determinants to the loop 2 region of bacterial uS5, connecting this region to antibiotic resistance and rRNA processing.","evidence":"Systematic site-directed mutagenesis in E. coli with spectinomycin and fidelity reporters","pmids":["27855073"],"confidence":"High","gaps":["Direct structural basis of fidelity effects not resolved","Generalizability to eukaryotic uS5 inferred only"]},{"year":2018,"claim":"Revealed a competition for nascent uS5 between PRMT3 and the zinc-finger protein ZNF277, defining an extraribosomal regulatory hub on uS5.","evidence":"AP-MS, reciprocal Co-IP, proximity ligation and competition experiments in human cells","pmids":["30530495"],"confidence":"High","gaps":["Functional outcome of ZNF277 binding for ribosome biogenesis unclear","Hierarchy with PDCD2 binding not established"]},{"year":2019,"claim":"Identified Tsr4 as a dedicated cytoplasmic chaperone that engages nascent Rps2 via its N-terminal extension, explaining how uS5 is kept soluble before assembly.","evidence":"Co-translational Co-IP, genetic depletion and fractionation in S. cerevisiae","pmids":["31182640"],"confidence":"High","gaps":["Handoff from chaperone to pre-40S not defined","Structural basis of N-terminal recognition not solved here"]},{"year":2020,"claim":"Established human PDCD2 as the functional Tsr4 ortholog, a co-translational uS5 chaperone whose loss phenocopies uS5 deficiency.","evidence":"AP-MS, co-translational Co-IP, PDCD2 knockdown with ribosome biogenesis and polysome readouts","pmids":["33245768"],"confidence":"High","gaps":["Precise binding motif not yet mapped at this stage","Coordination with nuclear import factors unresolved"]},{"year":2022,"claim":"Connected uS5 mRNA-entry-channel residues to start codon recognition, showing they tune initiation fidelity in concert with eIF1/eIF1A.","evidence":"Rps2 mutagenesis with UUG and Kozak-context initiation reporters and epistasis in yeast","pmids":["34791232"],"confidence":"High","gaps":["Structural mechanism at the entry channel not directly visualized","Whether effect is direct or via mRNA path geometry unresolved"]},{"year":2022,"claim":"Identified a covalent ligandable cysteine (C222) on RPS2 whose modification triggers nucleolar stress and p53 activation, defining a druggable extraribosomal stress node.","evidence":"Thiol-reactivity chemical proteomics and covalent binding/p53 assays in NPM1-mutant AML cells","pmids":["36873185"],"confidence":"Medium","gaps":["Selectivity of heliangin for RPS2 versus other targets not fully excluded","Mechanism linking C222 modification to rRNA disruption unclear"]},{"year":2023,"claim":"Defined the nuclear import logic of uS5, identifying two independent import signals and the importin-β Pse1 as a carrier.","evidence":"GFP import reporters, deletion/point mutants and Co-IP with Pse1 in yeast","pmids":["37509163"],"confidence":"Medium","gaps":["Relative in vivo contribution of the two pathways not quantified","Whether import is coupled to chaperone release unclear"]},{"year":2024,"claim":"Showed that phosphorylation of uS5 Ser176 at the uS4-uS5 interface dynamically regulates decoding selectivity through a salt bridge, with opposing kinase pathways setting accuracy.","evidence":"Ser176/Arg57 mutagenesis and kinase-mutant epistasis with fidelity reporters in yeast","pmids":["38340338"],"confidence":"Medium","gaps":["Salt bridge not confirmed by direct structural evidence","Physiological signals tuning the phosphorylation balance unknown"]},{"year":2025,"claim":"Linked RPS2 stability to RACK1-dependent protection from proteasomal degradation and to NF-κB signaling, providing an extraribosomal regulatory and oncogenic axis.","evidence":"Co-IP, ubiquitination/MG132 assays, NF-κB reporter and rescue in glioma cells","pmids":["40522528"],"confidence":"Medium","gaps":["E3 ligase for RPS2 not identified","Mechanism connecting RPS2 to NF-κB not defined"]},{"year":2026,"claim":"Mapped the uS5-PDCD2 interface to a 30-residue N-terminal region with a conserved FxxGFG motif and showed a peptide disruptor impairs cancer cell viability, defining a targetable chaperone interaction.","evidence":"Affinity purification, structural modeling, complementation biosensor, mutagenesis and viability assays in human cells","pmids":["41933732"],"confidence":"Medium","gaps":["High-resolution structure of the complex not determined","Specificity of peptide effect versus general translation inhibition not fully resolved"]},{"year":2025,"claim":"Placed RPS2 ubiquitination within an eIF2A-regulated ribosome-associated quality control pathway antagonizing USP10-dependent 40S rescue.","evidence":"TurboID proximity labeling MS, eIF2A knockout, SILAC and 40S footprinting (preprint)","pmids":[],"confidence":"Low","gaps":["Preprint, single lab, mechanistic placement is indirect","E3 ligase and ubiquitination sites on RPS2 not defined","Direct effect on RPS2 versus bystander labeling not separated"]},{"year":null,"claim":"How the multiple extraribosomal regulators of uS5 (chaperones, methylation, ZNF277, ubiquitination, RACK1) are coordinated in time and space, and how they feed back on translation fidelity, remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No integrated model linking modifications to ribosome function","Structural basis of the uS4-uS5 phospho-salt bridge unconfirmed","Functional role of arginine methylation undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,7,8]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[12]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[7,8,9]}],"localization":[{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[2,5,7]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[2,3,11]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[10]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[2,7]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[4,5,7]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[2]}],"complexes":["40S small ribosomal subunit","pre-40S particle"],"partners":["PRMT3","ZNF277","PDCD2","TSR4","RACK1","PSE1","US4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P15880","full_name":"Small ribosomal subunit protein uS5","aliases":["40S ribosomal protein S2","40S ribosomal protein S4","Protein LLRep3"],"length_aa":293,"mass_kda":31.3,"function":"Component of the ribosome, a large ribonucleoprotein complex responsible for the synthesis of proteins in the cell (PubMed:23636399). The small ribosomal subunit (SSU) binds messenger RNAs (mRNAs) and translates the encoded message by selecting cognate aminoacyl-transfer RNA (tRNA) molecules (PubMed:23636399). The large subunit (LSU) contains the ribosomal catalytic site termed the peptidyl transferase center (PTC), which catalyzes the formation of peptide bonds, thereby polymerizing the amino acids delivered by tRNAs into a polypeptide chain (PubMed:23636399). The nascent polypeptides leave the ribosome through a tunnel in the LSU and interact with protein factors that function in enzymatic processing, targeting, and the membrane insertion of nascent chains at the exit of the ribosomal tunnel (PubMed:23636399). Plays a role in the assembly and function of the 40S ribosomal subunit (By similarity). Mutations in this protein affects the control of translational fidelity (By similarity). Involved in nucleolar processing of pre-18S ribosomal RNA and ribosome assembly (By similarity)","subcellular_location":"Cytoplasm; Nucleus, nucleolus","url":"https://www.uniprot.org/uniprotkb/P15880/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/RPS2","classification":"Common Essential","n_dependent_lines":383,"n_total_lines":383,"dependency_fraction":1.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CAPRIN1","stoichiometry":10.0},{"gene":"DRG1","stoichiometry":10.0},{"gene":"EIF2S3","stoichiometry":10.0},{"gene":"ENY2","stoichiometry":10.0},{"gene":"RACK1","stoichiometry":10.0},{"gene":"RBM8A","stoichiometry":10.0},{"gene":"RPL11","stoichiometry":10.0},{"gene":"RPL13","stoichiometry":10.0},{"gene":"RPL4","stoichiometry":10.0},{"gene":"RPL5","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/RPS2","total_profiled":1310},"omim":[{"mim_id":"617508","title":"ZINC FINGER PROTEIN 598; ZNF598","url":"https://www.omim.org/entry/617508"},{"mim_id":"603624","title":"RIBOSOMAL PROTEIN S2; RPS2","url":"https://www.omim.org/entry/603624"},{"mim_id":"603251","title":"CYCLIN-DEPENDENT KINASE 9; CDK9","url":"https://www.omim.org/entry/603251"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RPS2"},"hgnc":{"alias_symbol":["LLREP3","S2","uS5"],"prev_symbol":[]},"alphafold":{"accession":"P15880","domains":[{"cath_id":"3.30.160.20","chopping":"64-163","consensus_level":"medium","plddt":93.2128,"start":64,"end":163},{"cath_id":"3.30.230.10","chopping":"183-254","consensus_level":"medium","plddt":93.5317,"start":183,"end":254}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P15880","model_url":"https://alphafold.ebi.ac.uk/files/AF-P15880-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P15880-F1-predicted_aligned_error_v6.png","plddt_mean":80.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RPS2","jax_strain_url":"https://www.jax.org/strain/search?query=RPS2"},"sequence":{"accession":"P15880","fasta_url":"https://rest.uniprot.org/uniprotkb/P15880.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P15880/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P15880"}},"corpus_meta":[{"pmid":"7923358","id":"PMC_7923358","title":"The A. thaliana disease resistance gene RPS2 encodes a protein containing a nucleotide-binding site and leucine-rich repeats.","date":"1994","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/7923358","citation_count":492,"is_preprint":false},{"pmid":"10516000","id":"PMC_10516000","title":"Herpes simplex virus inhibits apoptosis through the action of two genes, Us5 and Us3.","date":"1999","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/10516000","citation_count":189,"is_preprint":false},{"pmid":"15749765","id":"PMC_15749765","title":"Molecular basis for the RIN4 negative regulation of RPS2 disease resistance.","date":"2005","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/15749765","citation_count":127,"is_preprint":false},{"pmid":"17439947","id":"PMC_17439947","title":"Ribosomal protein rpS2 is hypomethylated in PRMT3-deficient mice.","date":"2007","source":"The Journal of biological 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In PRMT3-knockout mice, rpS2 is hypomethylated, establishing rpS2 as a bona fide in vivo PRMT3 substrate that cannot be compensated by other PRMTs.\",\n      \"method\": \"Targeted gene disruption (PRMT3 knockout mice), Western blot for methylarginine, ribosome fractionation (polysome profiling), co-fractionation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic knockout with direct biochemical readout (hypomethylation), replicated across multiple assays in a single rigorous study\",\n      \"pmids\": [\"17439947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In budding yeast Saccharomyces cerevisiae, which lacks a zinc-finger-containing Rmt3/PRMT3 homolog, Rps2 is partially modified to asymmetric dimethylarginine and monomethylarginine by the major arginine methyltransferase Rmt1, demonstrating organism-specific methyltransferase usage for the same substrate.\",\n      \"method\": \"Arginine methylation assays, methyltransferase deletion strains, mass spectrometry/biochemical detection of methylarginine\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vivo genetic evidence (rmt1 deletion) with biochemical detection, single lab\",\n      \"pmids\": [\"20035717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In fission yeast, Rps2 is required for nuclear export competence of pre-40S ribosomal subunits; its depletion causes retention of pre-40S particles in the nucleolus, blocks 40S subunit production, and impairs cleavage at site A2 within 32S pre-rRNA.\",\n      \"method\": \"Genetic depletion of Rps2 in Schizosaccharomyces pombe, pre-rRNA processing analysis, rRNA pulse-chase assays, nucleolar retention assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic depletion with multiple orthogonal readouts (rRNA processing, pulse-chase, localization), establishing a specific mechanistic role\",\n      \"pmids\": [\"18820293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Human zinc finger protein ZNF277 forms an extraribosomal complex with uS5 (RPS2) in the cytoplasm and nucleolus using a C2H2-type zinc finger domain. ZNF277 and PRMT3 compete for uS5 binding: PRMT3 overexpression inhibits ZNF277-uS5 complex formation, and ZNF277 depletion increases uS5-PRMT3 levels. ZNF277 recognizes nascent uS5 co-translationally.\",\n      \"method\": \"Quantitative proteomics (affinity purification-MS), Co-IP in human cells, proximity ligation assay, overexpression/depletion experiments, subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — quantitative proteomics plus reciprocal Co-IP plus competition experiments, multiple orthogonal methods in a single study\",\n      \"pmids\": [\"30530495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Tsr4 is a dedicated cytoplasmic chaperone for Rps2 (uS5) in S. cerevisiae. Tsr4 associates with Rps2 co-translationally, requires the eukaryote-specific N-terminal extension of Rps2 for interaction, promotes Rps2 solubility and expression, and is restricted to the cytoplasm despite Rps2 assembling into nuclear pre-40S particles.\",\n      \"method\": \"Co-translational co-IP, genetic depletion/perturbation of Tsr4, ribosome biogenesis assays, subcellular fractionation, yeast genetics\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-translational association established with multiple approaches, genetic phenocopy of Rps2 depletion, localization confirmed by fractionation\",\n      \"pmids\": [\"31182640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Human PDCD2 functions as a dedicated ribosomal protein chaperone for uS5 (RPS2); PDCD2-uS5 complex is assembled co-translationally. Loss of PDCD2 impairs accumulation of soluble uS5 and its incorporation into 40S ribosomal subunits, causing defects in small ribosomal subunit synthesis that phenocopy uS5 deficiency.\",\n      \"method\": \"Quantitative proteomics (affinity purification-MS), co-translational Co-IP, PDCD2 knockdown with ribosome biogenesis readouts, polysome profiling\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — quantitative proteomics, co-translational assembly evidence, genetic loss-of-function with multiple ribosome biogenesis phenotypes, orthologous to yeast Tsr4\",\n      \"pmids\": [\"33245768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In Drosophila, Zfrp8/PDCD2 directly interacts with RpS2 (uS5) of the 40S small ribosomal subunit. Zfrp8/PDCD2 regulates cytoplasmic levels of 40S ribosomal subunit components and controls cytoplasmic localization of specific mRNAs; knockdown causes nuclear accumulation of specific mRNAs and TE transcripts, suggesting Zfrp8 functions at late stages of ribosome assembly.\",\n      \"method\": \"Co-IP (Zfrp8-RpS2 pulldown), fluorescent tagging of ribosomal proteins, genetic knockdown (RNAi), RNA localization assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct Co-IP plus functional genetic knockdown, single lab, multiple readouts\",\n      \"pmids\": [\"26807849\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Ribosomal protein uS5/Rps2 residues at the mRNA entry channel of the 40S subunit influence start codon recognition in vivo; nonlethal substitutions of conserved Rps2 residues reduce bulk translation initiation, increase discrimination against poor initiation codons (near-cognate UUG and suboptimal Kozak context AUG), resembling substitutions in uS3/Rps3 and initiation factors eIF1/eIF1A.\",\n      \"method\": \"Site-directed mutagenesis of Rps2 residues, yeast genetic assays for translation initiation fidelity (UUG initiation reporters, Kozak context reporters), epistasis with known initiation mutants\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis combined with multiple in vivo reporter assays dissecting distinct mechanisms, single lab but multiple orthogonal genetic readouts\",\n      \"pmids\": [\"34791232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mutations in the loop 2 region (residues 20–31) of ribosomal protein uS5 in E. coli confer spectinomycin resistance and affect translational fidelity; a minority of loop 2 mutants also show altered rRNA processing or ribosome biogenesis defects, demonstrating that this region participates in subunit assembly and maintenance of translational accuracy.\",\n      \"method\": \"Site-directed mutagenesis (21 unique mutants), spectinomycin sensitivity assays, translational fidelity reporters, rRNA processing analysis\",\n      \"journal\": \"Antimicrobial agents and chemotherapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with multiple functional readouts (antibiotic resistance, fidelity, rRNA processing), replicated across multiple mutants\",\n      \"pmids\": [\"27855073\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In S. cerevisiae, the cyclin-dependent kinase pathway (via Ypk2) phosphorylates Ser176 of uS5 (RPS2), which is located at the uS4-uS5 interface; phospho-Ser176 forms a salt bridge with Arg57 of uS4, strengthening the interface and increasing decoding selectivity. A second kinase pathway involving TORC1 and Pkc1 opposes this phosphorylation, indicating that translational accuracy is dynamically regulated by competing phosphorylation on uS5.\",\n      \"method\": \"Site-directed mutagenesis of Ser176 and Arg57, genetic epistasis analysis with kinase mutants (ctk1, ypk2, TORC1, pkc1), translational fidelity reporters\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis and epistasis in single lab; phosphorylation-salt bridge model supported by genetic data but not confirmed by direct structural evidence in this study\",\n      \"pmids\": [\"38340338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Nuclear import of Rps2 (uS5) in yeast requires two distinct import signals: (1) an internal region (amino acids 76–145) that interacts with the importin-β Pse1, with Arg95, Arg97, and Lys99 being critical determinants; (2) an N-terminal region (amino acids 10–28) containing basic residues that constitutes a second import pathway. Both pathways function independently of the dedicated chaperone Tsr4.\",\n      \"method\": \"GFP reporter nuclear import assays, deletion/mutation analysis of Rps2 import signals, Co-IP with Pse1, genetic dissection in yeast\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with reporter assays and interaction data, single lab with multiple mutants tested\",\n      \"pmids\": [\"37509163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Heliangin (a sesquiterpene lactone) covalently binds to the C222 site of RPS2, disrupting pre-rRNA metabolic processes, causing nucleolar stress, and activating the ribosomal proteins–MDM2–p53 pathway with consequent p53 stabilization in NPM1-mutant AML cells.\",\n      \"method\": \"Quantitative thiol reactivity platform screening, molecular biology validation, covalent binding assays, pre-rRNA processing assays, Western blot for p53/MDM2\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — chemical proteomics identification of binding site plus functional validation in cells, single lab\",\n      \"pmids\": [\"36873185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RPS2 specifically binds pre-let-7a-1 RNA and blocks its processing to mature let-7a/let-7f miRNA in prostate cancer cells; this was shown by EMSA, antibody supershift assay, and immunoprecipitation. Overexpression of RPS2 correlates with loss of let-7a and elevated ras/c-myc, while RPS2 knockdown restores let-7a and reduces oncogene expression and tumorigenesis.\",\n      \"method\": \"EMSA, antibody supershift assay, immunoprecipitation, stable transfection/shRNA knockdown, Northern blot, immunofluorescence, SCID mouse tumor model\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct RNA-binding shown by EMSA and IP, functional validation in multiple cell lines and in vivo, single lab\",\n      \"pmids\": [\"21148031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RACK1 stabilizes RPS2 by inhibiting ubiquitin-mediated proteasomal degradation of RPS2; RACK1 knockdown increases RPS2 ubiquitination and accelerates its degradation (reversed by MG132). Both RACK1 and RPS2 positively regulate the NF-κB pathway, and RPS2 overexpression partially rescues the NF-κB inhibition caused by RACK1 knockdown in glioma cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, MG132 proteasome inhibitor treatment, Western blot, NF-κB luciferase reporter assay, siRNA knockdown\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct Co-IP and ubiquitination assays, functional rescue experiment, single lab\",\n      \"pmids\": [\"40522528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A 30-amino-acid N-terminal region of uS5 (RPS2) is necessary and sufficient for interaction with its dedicated chaperone PDCD2; a conserved FxxGFG motif within this region mediates hydrophobic interactions with PDCD2. An 11-amino-acid uS5-derived peptide that inhibits PDCD2-uS5 interaction impairs cancer cell viability.\",\n      \"method\": \"Affinity purification assays, structural modeling, complementation-based biosensor in human cells and cell extracts, deletion/mutation analysis, cell viability assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical and cell-based interaction mapping with mutagenesis, single lab, functional consequence demonstrated\",\n      \"pmids\": [\"41933732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In the absence of eIF2A, ubiquitination of RPS2 (and RPS3) is specifically diminished upon ribosome stalling, and eIF2A antagonizes USP10-dependent rescue of 40S ribosomes; this places RPS2 ubiquitination in a ribosome-associated quality control pathway regulated by eIF2A.\",\n      \"method\": \"TurboID proximity labeling combined with mass spectrometry, polysome gradient fractionation, eIF2A knockout cells, dynamic SILAC mass spectrometry, 40S footprinting\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — proximity labeling MS in a preprint, single lab, mechanistic placement is indirect\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"RPS2 (uS5) is a universally conserved 40S small ribosomal subunit protein that, beyond its structural ribosomal role, is subject to a conserved extraribosomal regulatory network: it is co-translationally captured by dedicated chaperones (PDCD2/Tsr4 in eukaryotes) via its N-terminal extension, methylated at arginine residues by PRMT3 (or Rmt1 in budding yeast), and competes for binding between PRMT3 and ZNF277; its residues at the mRNA entry channel regulate translational fidelity and start codon selection, with accuracy further tuned by Ypk2/TORC1-dependent phosphorylation of Ser176 forming a salt bridge with uS4; in pre-ribosome biogenesis it is required for A2 cleavage and nuclear export competence of pre-40S particles; it is subject to ubiquitin-mediated proteasomal degradation stabilized by RACK1; it can covalently bind small molecules at C222 triggering nucleolar stress and p53 activation; and it has been reported to bind pre-let-7a-1 RNA to suppress miRNA processing in cancer cells.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RPS2 (uS5) is a universally conserved small (40S) ribosomal subunit protein whose residues lining the mRNA entry channel govern translation initiation fidelity and start codon selection, with nonlethal substitutions reducing bulk initiation and increasing discrimination against poor initiation codons such as near-cognate UUG and suboptimal Kozak-context AUG [#7]; in bacteria, mutations in the loop 2 region of uS5 confer spectinomycin resistance and likewise perturb translational accuracy and ribosome assembly [#8]. Decoding selectivity is dynamically tuned by phosphorylation of Ser176 at the uS4-uS5 interface, where a Ypk2-dependent phospho-Ser176 forms a salt bridge with Arg57 of uS4 to strengthen the interface, opposed by a TORC1/Pkc1 pathway [#9]. Before joining the ribosome, nascent uS5 is captured co-translationally by a dedicated chaperone — Tsr4 in budding yeast and its ortholog PDCD2 (Zfrp8 in Drosophila) in metazoans — which engages a conserved N-terminal extension (a FxxGFG motif within a 30-residue region) to promote uS5 solubility and incorporation into 40S subunits [#4, #5, #6, #14]. uS5 is also arginine-methylated by PRMT3 (Rmt1 in budding yeast), which is tethered to ribosomes through uS5 itself, while the zinc-finger protein ZNF277 competes with PRMT3 for binding to nascent uS5 [#0, #1, #3]. During biogenesis uS5 is required for A2 cleavage and nuclear export competence of pre-40S particles, and its own nuclear import depends on importin-β (Pse1) and a second N-terminal basic signal [#2, #10]. Extraribosomal and disease-associated functions reported in the corpus include RACK1-mediated protection of RPS2 from ubiquitin-proteasomal degradation coupled to NF-κB signaling [#13], covalent ligand binding at C222 that triggers nucleolar stress and ribosomal protein–MDM2–p53 activation [#11], and binding of pre-let-7a-1 RNA to suppress let-7 maturation in prostate cancer [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that uS5/RPS2 is a physiological substrate of a specific arginine methyltransferase, defining a post-translational modification of the protein beyond its structural role.\",\n      \"evidence\": \"PRMT3-knockout mice with Western blot for methylarginine and ribosome co-fractionation\",\n      \"pmids\": [\"17439947\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of rpS2 arginine methylation for translation not defined\", \"Methylated residues not mapped\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined uS5 as required for a discrete step of small-subunit maturation, showing it is needed for A2 cleavage and nuclear export of pre-40S particles rather than only the mature ribosome.\",\n      \"evidence\": \"Genetic depletion in S. pombe with pre-rRNA processing, pulse-chase and nucleolar retention assays\",\n      \"pmids\": [\"18820293\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular partners mediating export competence not identified\", \"Direct role versus assembly checkpoint effect not separated\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed that the same uS5 substrate is methylated by an organism-specific enzyme (Rmt1) in yeast lacking a PRMT3 homolog, indicating divergent enzyme usage on a conserved target.\",\n      \"evidence\": \"rmt1 deletion strains with biochemical detection of asymmetric dimethyl/monomethylarginine\",\n      \"pmids\": [\"20035717\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only partial modification observed\", \"Biological role of yeast Rps2 methylation unresolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified an extraribosomal RNA-binding function in which RPS2 binds pre-let-7a-1 and blocks its maturation, linking RPS2 to oncogenic miRNA regulation.\",\n      \"evidence\": \"EMSA, supershift, IP, knockdown/overexpression in prostate cancer cells and SCID tumor model\",\n      \"pmids\": [\"21148031\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RNA-binding interface on RPS2 not mapped\", \"Relationship to ribosomal pool of RPS2 unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrated a direct PDCD2-family (Zfrp8) interaction with RpS2 in metazoa and a role in late ribosome assembly and cytoplasmic mRNA localization.\",\n      \"evidence\": \"Co-IP and RNAi knockdown with RNA localization assays in Drosophila\",\n      \"pmids\": [\"26807849\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-translational nature not established in this work\", \"Interaction interface unmapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Localized translational-accuracy and assembly determinants to the loop 2 region of bacterial uS5, connecting this region to antibiotic resistance and rRNA processing.\",\n      \"evidence\": \"Systematic site-directed mutagenesis in E. coli with spectinomycin and fidelity reporters\",\n      \"pmids\": [\"27855073\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct structural basis of fidelity effects not resolved\", \"Generalizability to eukaryotic uS5 inferred only\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed a competition for nascent uS5 between PRMT3 and the zinc-finger protein ZNF277, defining an extraribosomal regulatory hub on uS5.\",\n      \"evidence\": \"AP-MS, reciprocal Co-IP, proximity ligation and competition experiments in human cells\",\n      \"pmids\": [\"30530495\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional outcome of ZNF277 binding for ribosome biogenesis unclear\", \"Hierarchy with PDCD2 binding not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified Tsr4 as a dedicated cytoplasmic chaperone that engages nascent Rps2 via its N-terminal extension, explaining how uS5 is kept soluble before assembly.\",\n      \"evidence\": \"Co-translational Co-IP, genetic depletion and fractionation in S. cerevisiae\",\n      \"pmids\": [\"31182640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Handoff from chaperone to pre-40S not defined\", \"Structural basis of N-terminal recognition not solved here\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established human PDCD2 as the functional Tsr4 ortholog, a co-translational uS5 chaperone whose loss phenocopies uS5 deficiency.\",\n      \"evidence\": \"AP-MS, co-translational Co-IP, PDCD2 knockdown with ribosome biogenesis and polysome readouts\",\n      \"pmids\": [\"33245768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise binding motif not yet mapped at this stage\", \"Coordination with nuclear import factors unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected uS5 mRNA-entry-channel residues to start codon recognition, showing they tune initiation fidelity in concert with eIF1/eIF1A.\",\n      \"evidence\": \"Rps2 mutagenesis with UUG and Kozak-context initiation reporters and epistasis in yeast\",\n      \"pmids\": [\"34791232\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism at the entry channel not directly visualized\", \"Whether effect is direct or via mRNA path geometry unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a covalent ligandable cysteine (C222) on RPS2 whose modification triggers nucleolar stress and p53 activation, defining a druggable extraribosomal stress node.\",\n      \"evidence\": \"Thiol-reactivity chemical proteomics and covalent binding/p53 assays in NPM1-mutant AML cells\",\n      \"pmids\": [\"36873185\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Selectivity of heliangin for RPS2 versus other targets not fully excluded\", \"Mechanism linking C222 modification to rRNA disruption unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the nuclear import logic of uS5, identifying two independent import signals and the importin-β Pse1 as a carrier.\",\n      \"evidence\": \"GFP import reporters, deletion/point mutants and Co-IP with Pse1 in yeast\",\n      \"pmids\": [\"37509163\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative in vivo contribution of the two pathways not quantified\", \"Whether import is coupled to chaperone release unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed that phosphorylation of uS5 Ser176 at the uS4-uS5 interface dynamically regulates decoding selectivity through a salt bridge, with opposing kinase pathways setting accuracy.\",\n      \"evidence\": \"Ser176/Arg57 mutagenesis and kinase-mutant epistasis with fidelity reporters in yeast\",\n      \"pmids\": [\"38340338\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Salt bridge not confirmed by direct structural evidence\", \"Physiological signals tuning the phosphorylation balance unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked RPS2 stability to RACK1-dependent protection from proteasomal degradation and to NF-κB signaling, providing an extraribosomal regulatory and oncogenic axis.\",\n      \"evidence\": \"Co-IP, ubiquitination/MG132 assays, NF-κB reporter and rescue in glioma cells\",\n      \"pmids\": [\"40522528\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase for RPS2 not identified\", \"Mechanism connecting RPS2 to NF-κB not defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Mapped the uS5-PDCD2 interface to a 30-residue N-terminal region with a conserved FxxGFG motif and showed a peptide disruptor impairs cancer cell viability, defining a targetable chaperone interaction.\",\n      \"evidence\": \"Affinity purification, structural modeling, complementation biosensor, mutagenesis and viability assays in human cells\",\n      \"pmids\": [\"41933732\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"High-resolution structure of the complex not determined\", \"Specificity of peptide effect versus general translation inhibition not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed RPS2 ubiquitination within an eIF2A-regulated ribosome-associated quality control pathway antagonizing USP10-dependent 40S rescue.\",\n      \"evidence\": \"TurboID proximity labeling MS, eIF2A knockout, SILAC and 40S footprinting (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint, single lab, mechanistic placement is indirect\", \"E3 ligase and ubiquitination sites on RPS2 not defined\", \"Direct effect on RPS2 versus bystander labeling not separated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple extraribosomal regulators of uS5 (chaperones, methylation, ZNF277, ubiquitination, RACK1) are coordinated in time and space, and how they feed back on translation fidelity, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No integrated model linking modifications to ribosome function\", \"Structural basis of the uS4-uS5 phospho-salt bridge unconfirmed\", \"Functional role of arginine methylation undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 7, 8]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [7, 8, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [2, 5, 7]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [2, 3, 11]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [2, 7]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [4, 5, 7]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [\"40S small ribosomal subunit\", \"pre-40S particle\"],\n    \"partners\": [\"PRMT3\", \"ZNF277\", \"PDCD2\", \"Tsr4\", \"RACK1\", \"Pse1\", \"uS4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}