{"gene":"RPS27L","run_date":"2026-06-10T07:46:27","timeline":{"discoveries":[{"year":2006,"finding":"RPS27L is a direct transcriptional target of p53: a consensus p53-binding site in the first intron of RPS27L drives p53-dependent transactivation, demonstrated by direct p53 binding in vitro and in vivo (ChIP), luciferase reporter assays, and sensitivity to dominant-negative p53 mutants. Overexpression of RPS27L promotes, and siRNA silencing inhibits, etoposide-induced apoptosis.","method":"ChIP, in vitro binding, luciferase reporter, siRNA knockdown, overexpression with apoptosis assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (in vitro binding, ChIP, reporter assay, functional KD/OE) in a single focused study; replicated conceptually in subsequent papers","pmids":["17057733"],"is_preprint":false},{"year":2007,"finding":"RPS27L is a nuclear protein that forms nuclear foci upon DNA damage. Depletion of RPS27L causes deficiency in DNA damage checkpoints, converting p53-mediated cell cycle arrest to apoptosis, and RPS27L positively regulates p21 protein expression.","method":"siRNA knockdown, immunofluorescence/nuclear foci analysis, cell cycle and apoptosis assays, western blot for p21","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean siRNA KD with defined phenotypic readouts (cell fate switch, p21 levels) and localization data; single lab, multiple orthogonal methods","pmids":["18056458"],"is_preprint":false},{"year":2010,"finding":"The N-terminal region of RPS27L binds to the central acidic domain of MDM2, forming an in vivo triplex complex with MDM2 and p53. RPS27L competes with p53 for MDM2 binding, inhibits MDM2-mediated p53 ubiquitination, and extends p53 protein half-life. RPS27L is itself a short-lived MDM2 substrate whose degradation requires the RING or acidic domain of MDM2. Upon p53-activating signals, RPS27L shuttles from cytoplasm to nucleoplasm where it colocalizes with MDM2.","method":"Co-immunoprecipitation, domain-mapping experiments, ubiquitination assay, protein half-life (CHX chase), siRNA knockdown, immunofluorescence/subcellular fractionation","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal Co-IP, domain mapping, in vivo ubiquitination assay, CHX chase, and localization all in one study; multiple orthogonal methods","pmids":["21170087"],"is_preprint":false},{"year":2014,"finding":"In vivo mouse knockout shows that Rps27l disruption triggers ribosomal stress that stabilizes Mdm2, which then degrades Mdm4, reducing the Mdm2-Mdm4 E3 ligase activity toward p53 and leading to p53-dependent apoptotic depletion of hematopoietic stem cells and postnatal death rescued by Trp53 deletion. Under Trp53+/- background, Rps27l loss drives genomic instability and Trp53 LOH to promote lymphomagenesis.","method":"Germline knockout mice, genetic rescue (Trp53 deletion), western blot for Mdm2/Mdm4/p53 levels, hematopoietic stem cell assays, tumor incidence analysis, genome aneuploidy measurement","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic epistasis with multiple rescue experiments, replicated across two genetic backgrounds, multiple orthogonal readouts","pmids":["25144937"],"is_preprint":false},{"year":2018,"finding":"RPS27L silencing inactivates mTORC1 (but not mTORC2) and induces autophagy via the β-TrCP–DEPTOR axis: loss of RPS27L shortens β-TrCP protein half-life, causing DEPTOR accumulation that inhibits mTORC1. Simultaneous DEPTOR silencing partially rescues autophagy induction, establishing DEPTOR as a causal mediator. Autophagy inhibition with chloroquine or Bafilomycin A1 then triggers apoptosis in RPS27L-silenced cells.","method":"siRNA knockdown, protein half-life assay (CHX chase), mTOR pathway western blot, autophagy assays (LC3 flux), rescue experiments (DEPTOR co-knockdown), pharmacological inhibition","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (CHX chase, genetic rescue, pathway epistasis, pharmacological) in single lab; mechanistic pathway clearly delineated","pmids":["30425236"],"is_preprint":false},{"year":2018,"finding":"Rps27l inactivation causes radiosensitivity via two axes: (1) activated p53 pathway due to imbalanced Mdm2/Mdm4 levels and reduced E3 ligase activity; and (2) elevated Mdm2 binding to Nbs1 that inhibits Nbs1-Atm binding and subsequent Atm activation, reducing MRN/ATM-mediated DNA damage response. Heterozygous Mdm2 deletion restores the MRN/ATM signal.","method":"Rps27l−/−;Trp53+/− mice irradiation, western blot for Mdm2/Mdm4/p53/MRN/ATM, Co-IP of Mdm2-Nbs1, genetic rescue (Mdm2 heterozygous deletion), proliferation/apoptosis assays","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model with Co-IP interaction data, genetic rescue, and multiple pathway readouts; single lab with orthogonal methods","pmids":["29396424"],"is_preprint":false},{"year":2020,"finding":"Both RPS27L and RPS27 are subjected to neddylation by MDM2 E3 ligase and deneddylation by NEDP1. Blockage of neddylation with MLN4924 destabilizes RPS27L and RPS27 by shortening their protein half-lives. Knockdown of RPS27L/RPS27 sensitizes, and ectopic expression desensitizes, cancer cells to MLN4924-induced apoptosis, indicating that neddylation stabilizes these proteins for cancer cell survival.","method":"Neddylation assay, CHX chase (protein half-life), MLN4924 pharmacological inhibition, siRNA knockdown, overexpression, apoptosis assays","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — neddylation assay plus functional rescue; single lab, multiple orthogonal methods","pmids":["32779270"],"is_preprint":false},{"year":2020,"finding":"RPS27L binds directly to FANCD2 and FANCI. Upon RPS27L knockdown, FANCD2 and FANCI levels decrease due to accelerated degradation via p62-mediated autophagy-lysosome pathway (abrogated by chloroquine or Beclin1 knockdown). RPS27L knockdown suppresses FANCD2 foci formation and impairs ICL repair after mitomycin C treatment.","method":"Co-immunoprecipitation, siRNA knockdown, western blot, chloroquine/Beclin1 rescue, FANCD2 immunofluorescence foci, MMC sensitivity assay","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, genetic/pharmacological rescue, and functional ICL repair assay; single lab with multiple orthogonal methods","pmids":["33051438"],"is_preprint":false},{"year":2023,"finding":"Rps27 and Rps27l are functionally equivalent proteins arising from vertebrate whole-genome duplication: expressing Rps27 protein from the endogenous Rps27l locus or vice versa completely rescues loss-of-function lethality. Despite equivalent protein function, the paralogs associate preferentially with different mRNA transcripts in ribosomes and show inversely correlated, cell-type-specific expression patterns, indicating subfunctionalized expression rather than divergent protein function.","method":"Endogenous protein tagging, knock-in rescue (protein swap), ribosome-mRNA association profiling, homozygous lethal loss-of-function allele comparison, RNA-seq expression analysis across cell types","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — definitive genetic rescue (protein swap knock-in), endogenous tagging, ribosome profiling; multiple rigorous orthogonal methods in single comprehensive study","pmids":["37306301"],"is_preprint":false},{"year":2025,"finding":"PPP2R2C physically interacts with RPS27L (confirmed by IP-MS, Co-IP, and immunofluorescence) and stabilizes RPS27L protein by blocking proteasomal degradation (demonstrated by cycloheximide chase and proteasome inhibitor assays). RPS27L knockdown reverses PPP2R2C-mediated radioresistance and suppression of ferroptosis in nasopharyngeal carcinoma cells.","method":"IP-MS, Co-IP, immunofluorescence, cycloheximide chase, proteasome inhibition, siRNA knockdown, ferroptosis assays (lipid ROS, MDA, GPX4/SLC7A11 western blot, TEM)","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP confirmed by IP-MS and IF, CHX chase with proteasome rescue, functional genetic epistasis; single lab, multiple methods","pmids":["42115626"],"is_preprint":false},{"year":2025,"finding":"RPS27L functions as an RNA-binding protein whose N-terminal intrinsically disordered region mediates liquid-liquid phase separation (LLPS). RPS27L interacts with IGF1 to regulate myogenesis. Muscle-specific Rps27l knock-in mice show increased muscle mass, enlarged myofibers, higher fast-twitch fiber proportion, and enhanced muscle regeneration. RPS27L expression is negatively regulated by the myogenic transcription factor SIX4.","method":"Muscle-specific knock-in mice, myofiber size/composition analysis, LLPS assay, Co-IP/interaction studies with IGF1, siRNA/overexpression in myoblasts, SIX4 transcription factor assays","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knock-in mouse with clear phenotypic readouts plus LLPS and interaction data; single lab, multiple orthogonal methods","pmids":["40886325"],"is_preprint":false},{"year":2025,"finding":"Ribosome-associated factor Nufip1, highly expressed in long-lived bat fibroblasts, associates with ribosomal protein Rps27l and is proposed as an integrator of ribosomal and p53 signaling under DNA replication stress conditions.","method":"Comparative transcriptome analysis, co-association/interaction experiment (abstract does not specify Co-IP vs pulldown)","journal":"Zoological research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single interaction experiment without full methodological detail in abstract; single study, no replication","pmids":["40407135"],"is_preprint":false}],"current_model":"RPS27L is a direct p53 transcriptional target and evolutionarily conserved ribosomal protein that forms a multilevel regulatory circuit with the MDM2-p53 axis: its N-terminal domain binds the MDM2 acidic domain to compete with p53 for MDM2 binding, inhibit p53 ubiquitination, and extend p53 half-life, while MDM2 reciprocally neddylates and ubiquitinates RPS27L to control its stability; upon genotoxic stress, RPS27L shuttles to the nucleus, modulates DNA damage checkpoints (partly by protecting FANCD2/FANCI from autophagy-lysosomal degradation and by preventing Mdm2-mediated inhibition of the MRN-ATM axis), and in the absence of RPS27L, ribosomal stress stabilizes Mdm2 which degrades Mdm4, reducing E3 activity toward p53 and triggering p53-dependent apoptosis; additionally, RPS27L regulates autophagy via the β-TrCP–DEPTOR–mTORC1 axis, functions as an RNA-binding protein capable of liquid-liquid phase separation to regulate IGF1-dependent myogenesis, and its paralog Rps27 is functionally interchangeable at the protein level despite the two paralogs being cell-type-specifically expressed and associating with distinct ribosome-mRNA populations."},"narrative":{"mechanistic_narrative":"RPS27L is an evolutionarily conserved ribosomal protein that operates as a stress-responsive node within the MDM2–p53 axis and is itself a direct p53 transcriptional target driven by a consensus p53-binding site in its first intron [PMID:17057733]. Mechanistically, the N-terminal region of RPS27L binds the central acidic domain of MDM2 to form a triplex with p53, competing with p53 for MDM2 binding, inhibiting p53 ubiquitination, and extending p53 half-life, while RPS27L is reciprocally a short-lived MDM2 substrate whose turnover is controlled by MDM2-mediated ubiquitination and neddylation, the latter counteracted by NEDP1 deneddylation [PMID:21170087, PMID:32779270]. Upon genotoxic stress RPS27L shuttles to the nucleus, forms foci, and is required for intact DNA-damage checkpoints and p21 expression [PMID:18056458, PMID:21170087]. In vivo, loss of Rps27l provokes ribosomal stress that stabilizes Mdm2, leading to Mdm4 degradation, reduced E3 activity toward p53, and p53-dependent apoptotic depletion of hematopoietic stem cells, and it impairs the DNA-damage response by enhancing Mdm2 binding to Nbs1 and blocking Nbs1–Atm activation [PMID:25144937, PMID:29396424]. RPS27L additionally protects genome stability by binding FANCD2 and FANCI and shielding them from p62-mediated autophagy-lysosomal degradation, enabling interstrand crosslink repair [PMID:33051438], and it restrains autophagy through the β-TrCP–DEPTOR–mTORC1 axis [PMID:30425236]. Beyond ribosomal/p53 signaling, RPS27L acts as an RNA-binding protein whose N-terminal intrinsically disordered region drives liquid-liquid phase separation and which interacts with IGF1 to promote myogenesis under negative control by SIX4 [PMID:40886325]. Its paralog Rps27 is functionally interchangeable at the protein level, with the two genes differing in cell-type-specific expression and preferential association with distinct ribosome-bound mRNAs rather than in protein activity [PMID:37306301].","teleology":[{"year":2006,"claim":"Established that RPS27L is not merely a constitutive ribosomal protein but a direct effector of the p53 program, placing it downstream of p53 in stress responses.","evidence":"ChIP, in vitro p53 binding, luciferase reporter, and siRNA/overexpression apoptosis assays identifying a p53 site in the RPS27L first intron","pmids":["17057733"],"confidence":"High","gaps":["Did not define how RPS27L protein executes its pro-apoptotic effect downstream of p53","No mechanistic link to MDM2 yet"]},{"year":2007,"claim":"Showed RPS27L feeds back into DNA-damage checkpoint control, determining the arrest-versus-apoptosis decision rather than acting solely as a p53 output.","evidence":"siRNA knockdown with nuclear foci imaging, cell cycle/apoptosis assays, and p21 western blot","pmids":["18056458"],"confidence":"Medium","gaps":["Molecular basis of checkpoint regulation undefined","Mechanism of p21 stabilization not established"]},{"year":2010,"claim":"Defined the physical and reciprocal regulatory logic of the RPS27L–MDM2–p53 triplex, explaining how RPS27L stabilizes p53 and how MDM2 limits RPS27L.","evidence":"Reciprocal Co-IP, domain mapping, in vivo ubiquitination assay, CHX chase, and subcellular fractionation","pmids":["21170087"],"confidence":"High","gaps":["Stoichiometry and structure of the triplex unresolved","Signal triggering nuclear shuttling not identified"]},{"year":2014,"claim":"Demonstrated in vivo that RPS27L loss acts through a ribosomal-stress/Mdm2–Mdm4 rebalancing to drive p53-dependent stem cell apoptosis and, in a p53-haploinsufficient context, genomic instability and tumorigenesis.","evidence":"Germline Rps27l knockout mice with Trp53 genetic rescue, Mdm2/Mdm4/p53 western blots, HSC assays, and tumor incidence","pmids":["25144937"],"confidence":"High","gaps":["How RPS27L loss is sensed as ribosomal stress that stabilizes Mdm2 not mechanistically resolved","Whether checkpoint and ribosomal functions are separable in vivo unclear"]},{"year":2018,"claim":"Identified a second DNA-damage arm in which RPS27L loss enhances Mdm2–Nbs1 binding to suppress MRN/ATM activation, separating p53-axis and ATM-axis contributions to radiosensitivity.","evidence":"Irradiated Rps27l−/−;Trp53+/− mice, Mdm2-Nbs1 Co-IP, pathway western blots, and Mdm2 heterozygous genetic rescue","pmids":["29396424"],"confidence":"High","gaps":["Direct effect of RPS27L on Mdm2–Nbs1 interaction versus indirect via Mdm2 levels not fully dissected"]},{"year":2018,"claim":"Extended RPS27L function beyond p53 by showing it controls autophagy and mTORC1 activity through the β-TrCP–DEPTOR axis.","evidence":"siRNA knockdown, CHX chase of β-TrCP, mTOR pathway and LC3 flux assays, DEPTOR co-knockdown rescue, and pharmacological autophagy inhibition","pmids":["30425236"],"confidence":"High","gaps":["How RPS27L regulates β-TrCP stability mechanistically unknown","Relationship of this axis to its p53/MDM2 functions unclear"]},{"year":2020,"claim":"Showed RPS27L and RPS27 stability is set by an MDM2-neddylation/NEDP1-deneddylation cycle, linking neddylation pathway activity to cancer-cell survival.","evidence":"Neddylation assays, CHX chase, MLN4924 inhibition, knockdown and overexpression apoptosis assays","pmids":["32779270"],"confidence":"Medium","gaps":["Neddylation site(s) not mapped","Functional consequence of neddylation versus ubiquitination on RPS27L activity not separated"]},{"year":2020,"claim":"Revealed a direct genome-maintenance role in which RPS27L protects FANCD2/FANCI from autophagic degradation to enable interstrand crosslink repair.","evidence":"Co-IP, knockdown with chloroquine/Beclin1 rescue, FANCD2 foci imaging, and mitomycin C sensitivity assay","pmids":["33051438"],"confidence":"High","gaps":["How RPS27L shields FANCD2/FANCI from p62-mediated autophagy not defined","Whether this requires the MDM2/p53 axis unknown"]},{"year":2023,"claim":"Resolved the paralog relationship by demonstrating that Rps27 and Rps27l proteins are functionally interchangeable, with divergence residing in cell-type-specific expression and mRNA-selective ribosome association rather than protein activity.","evidence":"Protein-swap knock-in rescue of lethality, endogenous tagging, ribosome-mRNA association profiling, and cross-cell-type RNA-seq","pmids":["37306301"],"confidence":"High","gaps":["Determinants of paralog-specific mRNA association unknown","Whether non-ribosomal RPS27L functions are paralog-shared not tested"]},{"year":2025,"claim":"Identified an RNA-binding, phase-separating activity for RPS27L that drives IGF1-dependent myogenesis under SIX4 transcriptional control, broadening its role into tissue growth.","evidence":"Muscle-specific knock-in mice, myofiber phenotyping, LLPS assays, IGF1 interaction studies, and SIX4 transcription assays","pmids":["40886325"],"confidence":"Medium","gaps":["RNA targets of RPS27L not catalogued","Mechanistic link between LLPS and IGF1 signaling undefined"]},{"year":2025,"claim":"Implicated RPS27L as a stabilized effector of PPP2R2C-driven radioresistance and ferroptosis suppression, connecting its stability control to therapy response in cancer.","evidence":"IP-MS, Co-IP, immunofluorescence, CHX chase with proteasome inhibition, and ferroptosis assays in nasopharyngeal carcinoma cells","pmids":["42115626"],"confidence":"Medium","gaps":["How RPS27L suppresses ferroptosis mechanistically unknown","Whether PPP2R2C regulation intersects the MDM2/p53 axis untested"]},{"year":null,"claim":"How RPS27L's distinct functions — ribosomal incorporation, MDM2/p53 regulation, autophagy/mTORC1 control, FANCD2/FANCI protection, and RNA-binding/LLPS-driven myogenesis — are coordinated within a single protein and partitioned across cell types remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unifying structural or biochemical model links the ribosomal and non-ribosomal activities","Whether moonlighting functions occur on or off the ribosome is unknown","Cell-type determinants selecting among these functions undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[10]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,4]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]},{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[8]}],"pathway":[],"complexes":["ribosome"],"partners":["MDM2","TP53","FANCD2","FANCI","NBN","IGF1","PPP2R2C","DEPTOR"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q71UM5","full_name":"Ribosomal protein eS27-like","aliases":["40S ribosomal protein S27-like","Small ribosomal subunit protein eS27-like"],"length_aa":84,"mass_kda":9.5,"function":"","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q71UM5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/RPS27L","classification":"Not Classified","n_dependent_lines":20,"n_total_lines":1208,"dependency_fraction":0.016556291390728478},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RACK1","stoichiometry":10.0},{"gene":"RPL11","stoichiometry":10.0},{"gene":"RPL5","stoichiometry":10.0},{"gene":"RPS16","stoichiometry":10.0},{"gene":"SRP72","stoichiometry":10.0},{"gene":"DRG1","stoichiometry":4.0},{"gene":"EIF2S3","stoichiometry":4.0},{"gene":"EIF3B","stoichiometry":4.0},{"gene":"RBM8A","stoichiometry":4.0},{"gene":"RPL19","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/RPS27L","total_profiled":1310},"omim":[{"mim_id":"612055","title":"RIBOSOMAL PROTEIN S27-LIKE; RPS27L","url":"https://www.omim.org/entry/612055"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/RPS27L"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q71UM5","domains":[{"cath_id":"2.20.25.100","chopping":"29-80","consensus_level":"high","plddt":94.7173,"start":29,"end":80}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q71UM5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q71UM5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q71UM5-F1-predicted_aligned_error_v6.png","plddt_mean":92.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=RPS27L","jax_strain_url":"https://www.jax.org/strain/search?query=RPS27L"},"sequence":{"accession":"Q71UM5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q71UM5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q71UM5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q71UM5"}},"corpus_meta":[{"pmid":"21170087","id":"PMC_21170087","title":"Ribosomal protein S27-like and S27 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2006,\n      \"finding\": \"RPS27L is a direct transcriptional target of p53: a consensus p53-binding site in the first intron of RPS27L drives p53-dependent transactivation, demonstrated by direct p53 binding in vitro and in vivo (ChIP), luciferase reporter assays, and sensitivity to dominant-negative p53 mutants. Overexpression of RPS27L promotes, and siRNA silencing inhibits, etoposide-induced apoptosis.\",\n      \"method\": \"ChIP, in vitro binding, luciferase reporter, siRNA knockdown, overexpression with apoptosis assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (in vitro binding, ChIP, reporter assay, functional KD/OE) in a single focused study; replicated conceptually in subsequent papers\",\n      \"pmids\": [\"17057733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"RPS27L is a nuclear protein that forms nuclear foci upon DNA damage. Depletion of RPS27L causes deficiency in DNA damage checkpoints, converting p53-mediated cell cycle arrest to apoptosis, and RPS27L positively regulates p21 protein expression.\",\n      \"method\": \"siRNA knockdown, immunofluorescence/nuclear foci analysis, cell cycle and apoptosis assays, western blot for p21\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean siRNA KD with defined phenotypic readouts (cell fate switch, p21 levels) and localization data; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"18056458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The N-terminal region of RPS27L binds to the central acidic domain of MDM2, forming an in vivo triplex complex with MDM2 and p53. RPS27L competes with p53 for MDM2 binding, inhibits MDM2-mediated p53 ubiquitination, and extends p53 protein half-life. RPS27L is itself a short-lived MDM2 substrate whose degradation requires the RING or acidic domain of MDM2. Upon p53-activating signals, RPS27L shuttles from cytoplasm to nucleoplasm where it colocalizes with MDM2.\",\n      \"method\": \"Co-immunoprecipitation, domain-mapping experiments, ubiquitination assay, protein half-life (CHX chase), siRNA knockdown, immunofluorescence/subcellular fractionation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal Co-IP, domain mapping, in vivo ubiquitination assay, CHX chase, and localization all in one study; multiple orthogonal methods\",\n      \"pmids\": [\"21170087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In vivo mouse knockout shows that Rps27l disruption triggers ribosomal stress that stabilizes Mdm2, which then degrades Mdm4, reducing the Mdm2-Mdm4 E3 ligase activity toward p53 and leading to p53-dependent apoptotic depletion of hematopoietic stem cells and postnatal death rescued by Trp53 deletion. Under Trp53+/- background, Rps27l loss drives genomic instability and Trp53 LOH to promote lymphomagenesis.\",\n      \"method\": \"Germline knockout mice, genetic rescue (Trp53 deletion), western blot for Mdm2/Mdm4/p53 levels, hematopoietic stem cell assays, tumor incidence analysis, genome aneuploidy measurement\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic epistasis with multiple rescue experiments, replicated across two genetic backgrounds, multiple orthogonal readouts\",\n      \"pmids\": [\"25144937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"RPS27L silencing inactivates mTORC1 (but not mTORC2) and induces autophagy via the β-TrCP–DEPTOR axis: loss of RPS27L shortens β-TrCP protein half-life, causing DEPTOR accumulation that inhibits mTORC1. Simultaneous DEPTOR silencing partially rescues autophagy induction, establishing DEPTOR as a causal mediator. Autophagy inhibition with chloroquine or Bafilomycin A1 then triggers apoptosis in RPS27L-silenced cells.\",\n      \"method\": \"siRNA knockdown, protein half-life assay (CHX chase), mTOR pathway western blot, autophagy assays (LC3 flux), rescue experiments (DEPTOR co-knockdown), pharmacological inhibition\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (CHX chase, genetic rescue, pathway epistasis, pharmacological) in single lab; mechanistic pathway clearly delineated\",\n      \"pmids\": [\"30425236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Rps27l inactivation causes radiosensitivity via two axes: (1) activated p53 pathway due to imbalanced Mdm2/Mdm4 levels and reduced E3 ligase activity; and (2) elevated Mdm2 binding to Nbs1 that inhibits Nbs1-Atm binding and subsequent Atm activation, reducing MRN/ATM-mediated DNA damage response. Heterozygous Mdm2 deletion restores the MRN/ATM signal.\",\n      \"method\": \"Rps27l−/−;Trp53+/− mice irradiation, western blot for Mdm2/Mdm4/p53/MRN/ATM, Co-IP of Mdm2-Nbs1, genetic rescue (Mdm2 heterozygous deletion), proliferation/apoptosis assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model with Co-IP interaction data, genetic rescue, and multiple pathway readouts; single lab with orthogonal methods\",\n      \"pmids\": [\"29396424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Both RPS27L and RPS27 are subjected to neddylation by MDM2 E3 ligase and deneddylation by NEDP1. Blockage of neddylation with MLN4924 destabilizes RPS27L and RPS27 by shortening their protein half-lives. Knockdown of RPS27L/RPS27 sensitizes, and ectopic expression desensitizes, cancer cells to MLN4924-induced apoptosis, indicating that neddylation stabilizes these proteins for cancer cell survival.\",\n      \"method\": \"Neddylation assay, CHX chase (protein half-life), MLN4924 pharmacological inhibition, siRNA knockdown, overexpression, apoptosis assays\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — neddylation assay plus functional rescue; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"32779270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RPS27L binds directly to FANCD2 and FANCI. Upon RPS27L knockdown, FANCD2 and FANCI levels decrease due to accelerated degradation via p62-mediated autophagy-lysosome pathway (abrogated by chloroquine or Beclin1 knockdown). RPS27L knockdown suppresses FANCD2 foci formation and impairs ICL repair after mitomycin C treatment.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, western blot, chloroquine/Beclin1 rescue, FANCD2 immunofluorescence foci, MMC sensitivity assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, genetic/pharmacological rescue, and functional ICL repair assay; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33051438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Rps27 and Rps27l are functionally equivalent proteins arising from vertebrate whole-genome duplication: expressing Rps27 protein from the endogenous Rps27l locus or vice versa completely rescues loss-of-function lethality. Despite equivalent protein function, the paralogs associate preferentially with different mRNA transcripts in ribosomes and show inversely correlated, cell-type-specific expression patterns, indicating subfunctionalized expression rather than divergent protein function.\",\n      \"method\": \"Endogenous protein tagging, knock-in rescue (protein swap), ribosome-mRNA association profiling, homozygous lethal loss-of-function allele comparison, RNA-seq expression analysis across cell types\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — definitive genetic rescue (protein swap knock-in), endogenous tagging, ribosome profiling; multiple rigorous orthogonal methods in single comprehensive study\",\n      \"pmids\": [\"37306301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PPP2R2C physically interacts with RPS27L (confirmed by IP-MS, Co-IP, and immunofluorescence) and stabilizes RPS27L protein by blocking proteasomal degradation (demonstrated by cycloheximide chase and proteasome inhibitor assays). RPS27L knockdown reverses PPP2R2C-mediated radioresistance and suppression of ferroptosis in nasopharyngeal carcinoma cells.\",\n      \"method\": \"IP-MS, Co-IP, immunofluorescence, cycloheximide chase, proteasome inhibition, siRNA knockdown, ferroptosis assays (lipid ROS, MDA, GPX4/SLC7A11 western blot, TEM)\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP confirmed by IP-MS and IF, CHX chase with proteasome rescue, functional genetic epistasis; single lab, multiple methods\",\n      \"pmids\": [\"42115626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"RPS27L functions as an RNA-binding protein whose N-terminal intrinsically disordered region mediates liquid-liquid phase separation (LLPS). RPS27L interacts with IGF1 to regulate myogenesis. Muscle-specific Rps27l knock-in mice show increased muscle mass, enlarged myofibers, higher fast-twitch fiber proportion, and enhanced muscle regeneration. RPS27L expression is negatively regulated by the myogenic transcription factor SIX4.\",\n      \"method\": \"Muscle-specific knock-in mice, myofiber size/composition analysis, LLPS assay, Co-IP/interaction studies with IGF1, siRNA/overexpression in myoblasts, SIX4 transcription factor assays\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knock-in mouse with clear phenotypic readouts plus LLPS and interaction data; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40886325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Ribosome-associated factor Nufip1, highly expressed in long-lived bat fibroblasts, associates with ribosomal protein Rps27l and is proposed as an integrator of ribosomal and p53 signaling under DNA replication stress conditions.\",\n      \"method\": \"Comparative transcriptome analysis, co-association/interaction experiment (abstract does not specify Co-IP vs pulldown)\",\n      \"journal\": \"Zoological research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single interaction experiment without full methodological detail in abstract; single study, no replication\",\n      \"pmids\": [\"40407135\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RPS27L is a direct p53 transcriptional target and evolutionarily conserved ribosomal protein that forms a multilevel regulatory circuit with the MDM2-p53 axis: its N-terminal domain binds the MDM2 acidic domain to compete with p53 for MDM2 binding, inhibit p53 ubiquitination, and extend p53 half-life, while MDM2 reciprocally neddylates and ubiquitinates RPS27L to control its stability; upon genotoxic stress, RPS27L shuttles to the nucleus, modulates DNA damage checkpoints (partly by protecting FANCD2/FANCI from autophagy-lysosomal degradation and by preventing Mdm2-mediated inhibition of the MRN-ATM axis), and in the absence of RPS27L, ribosomal stress stabilizes Mdm2 which degrades Mdm4, reducing E3 activity toward p53 and triggering p53-dependent apoptosis; additionally, RPS27L regulates autophagy via the β-TrCP–DEPTOR–mTORC1 axis, functions as an RNA-binding protein capable of liquid-liquid phase separation to regulate IGF1-dependent myogenesis, and its paralog Rps27 is functionally interchangeable at the protein level despite the two paralogs being cell-type-specifically expressed and associating with distinct ribosome-mRNA populations.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RPS27L is an evolutionarily conserved ribosomal protein that operates as a stress-responsive node within the MDM2–p53 axis and is itself a direct p53 transcriptional target driven by a consensus p53-binding site in its first intron [#0]. Mechanistically, the N-terminal region of RPS27L binds the central acidic domain of MDM2 to form a triplex with p53, competing with p53 for MDM2 binding, inhibiting p53 ubiquitination, and extending p53 half-life, while RPS27L is reciprocally a short-lived MDM2 substrate whose turnover is controlled by MDM2-mediated ubiquitination and neddylation, the latter counteracted by NEDP1 deneddylation [#2, #6]. Upon genotoxic stress RPS27L shuttles to the nucleus, forms foci, and is required for intact DNA-damage checkpoints and p21 expression [#1, #2]. In vivo, loss of Rps27l provokes ribosomal stress that stabilizes Mdm2, leading to Mdm4 degradation, reduced E3 activity toward p53, and p53-dependent apoptotic depletion of hematopoietic stem cells, and it impairs the DNA-damage response by enhancing Mdm2 binding to Nbs1 and blocking Nbs1–Atm activation [#3, #5]. RPS27L additionally protects genome stability by binding FANCD2 and FANCI and shielding them from p62-mediated autophagy-lysosomal degradation, enabling interstrand crosslink repair [#7], and it restrains autophagy through the β-TrCP–DEPTOR–mTORC1 axis [#4]. Beyond ribosomal/p53 signaling, RPS27L acts as an RNA-binding protein whose N-terminal intrinsically disordered region drives liquid-liquid phase separation and which interacts with IGF1 to promote myogenesis under negative control by SIX4 [#10]. Its paralog Rps27 is functionally interchangeable at the protein level, with the two genes differing in cell-type-specific expression and preferential association with distinct ribosome-bound mRNAs rather than in protein activity [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established that RPS27L is not merely a constitutive ribosomal protein but a direct effector of the p53 program, placing it downstream of p53 in stress responses.\",\n      \"evidence\": \"ChIP, in vitro p53 binding, luciferase reporter, and siRNA/overexpression apoptosis assays identifying a p53 site in the RPS27L first intron\",\n      \"pmids\": [\"17057733\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how RPS27L protein executes its pro-apoptotic effect downstream of p53\", \"No mechanistic link to MDM2 yet\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showed RPS27L feeds back into DNA-damage checkpoint control, determining the arrest-versus-apoptosis decision rather than acting solely as a p53 output.\",\n      \"evidence\": \"siRNA knockdown with nuclear foci imaging, cell cycle/apoptosis assays, and p21 western blot\",\n      \"pmids\": [\"18056458\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of checkpoint regulation undefined\", \"Mechanism of p21 stabilization not established\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the physical and reciprocal regulatory logic of the RPS27L–MDM2–p53 triplex, explaining how RPS27L stabilizes p53 and how MDM2 limits RPS27L.\",\n      \"evidence\": \"Reciprocal Co-IP, domain mapping, in vivo ubiquitination assay, CHX chase, and subcellular fractionation\",\n      \"pmids\": [\"21170087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structure of the triplex unresolved\", \"Signal triggering nuclear shuttling not identified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated in vivo that RPS27L loss acts through a ribosomal-stress/Mdm2–Mdm4 rebalancing to drive p53-dependent stem cell apoptosis and, in a p53-haploinsufficient context, genomic instability and tumorigenesis.\",\n      \"evidence\": \"Germline Rps27l knockout mice with Trp53 genetic rescue, Mdm2/Mdm4/p53 western blots, HSC assays, and tumor incidence\",\n      \"pmids\": [\"25144937\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RPS27L loss is sensed as ribosomal stress that stabilizes Mdm2 not mechanistically resolved\", \"Whether checkpoint and ribosomal functions are separable in vivo unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified a second DNA-damage arm in which RPS27L loss enhances Mdm2–Nbs1 binding to suppress MRN/ATM activation, separating p53-axis and ATM-axis contributions to radiosensitivity.\",\n      \"evidence\": \"Irradiated Rps27l−/−;Trp53+/− mice, Mdm2-Nbs1 Co-IP, pathway western blots, and Mdm2 heterozygous genetic rescue\",\n      \"pmids\": [\"29396424\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct effect of RPS27L on Mdm2–Nbs1 interaction versus indirect via Mdm2 levels not fully dissected\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended RPS27L function beyond p53 by showing it controls autophagy and mTORC1 activity through the β-TrCP–DEPTOR axis.\",\n      \"evidence\": \"siRNA knockdown, CHX chase of β-TrCP, mTOR pathway and LC3 flux assays, DEPTOR co-knockdown rescue, and pharmacological autophagy inhibition\",\n      \"pmids\": [\"30425236\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RPS27L regulates β-TrCP stability mechanistically unknown\", \"Relationship of this axis to its p53/MDM2 functions unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed RPS27L and RPS27 stability is set by an MDM2-neddylation/NEDP1-deneddylation cycle, linking neddylation pathway activity to cancer-cell survival.\",\n      \"evidence\": \"Neddylation assays, CHX chase, MLN4924 inhibition, knockdown and overexpression apoptosis assays\",\n      \"pmids\": [\"32779270\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Neddylation site(s) not mapped\", \"Functional consequence of neddylation versus ubiquitination on RPS27L activity not separated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed a direct genome-maintenance role in which RPS27L protects FANCD2/FANCI from autophagic degradation to enable interstrand crosslink repair.\",\n      \"evidence\": \"Co-IP, knockdown with chloroquine/Beclin1 rescue, FANCD2 foci imaging, and mitomycin C sensitivity assay\",\n      \"pmids\": [\"33051438\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RPS27L shields FANCD2/FANCI from p62-mediated autophagy not defined\", \"Whether this requires the MDM2/p53 axis unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the paralog relationship by demonstrating that Rps27 and Rps27l proteins are functionally interchangeable, with divergence residing in cell-type-specific expression and mRNA-selective ribosome association rather than protein activity.\",\n      \"evidence\": \"Protein-swap knock-in rescue of lethality, endogenous tagging, ribosome-mRNA association profiling, and cross-cell-type RNA-seq\",\n      \"pmids\": [\"37306301\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants of paralog-specific mRNA association unknown\", \"Whether non-ribosomal RPS27L functions are paralog-shared not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified an RNA-binding, phase-separating activity for RPS27L that drives IGF1-dependent myogenesis under SIX4 transcriptional control, broadening its role into tissue growth.\",\n      \"evidence\": \"Muscle-specific knock-in mice, myofiber phenotyping, LLPS assays, IGF1 interaction studies, and SIX4 transcription assays\",\n      \"pmids\": [\"40886325\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RNA targets of RPS27L not catalogued\", \"Mechanistic link between LLPS and IGF1 signaling undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated RPS27L as a stabilized effector of PPP2R2C-driven radioresistance and ferroptosis suppression, connecting its stability control to therapy response in cancer.\",\n      \"evidence\": \"IP-MS, Co-IP, immunofluorescence, CHX chase with proteasome inhibition, and ferroptosis assays in nasopharyngeal carcinoma cells\",\n      \"pmids\": [\"42115626\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How RPS27L suppresses ferroptosis mechanistically unknown\", \"Whether PPP2R2C regulation intersects the MDM2/p53 axis untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How RPS27L's distinct functions — ribosomal incorporation, MDM2/p53 regulation, autophagy/mTORC1 control, FANCD2/FANCI protection, and RNA-binding/LLPS-driven myogenesis — are coordinated within a single protein and partitioned across cell types remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unifying structural or biochemical model links the ribosomal and non-ribosomal activities\", \"Whether moonlighting functions occur on or off the ribosome is unknown\", \"Cell-type determinants selecting among these functions undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": []}\n    ],\n    \"complexes\": [\"ribosome\"],\n    \"partners\": [\"MDM2\", \"TP53\", \"FANCD2\", \"FANCI\", \"NBN\", \"IGF1\", \"PPP2R2C\", \"DEPTOR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}