{"gene":"NOP53","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":2011,"finding":"PICT1 (NOP53) binds RPL11 and retains it in the nucleolus; loss of PICT1 releases RPL11 to the nucleoplasm where it binds MDM2 and blocks MDM2-mediated ubiquitination of p53, leading to p53 accumulation and G1 arrest/apoptosis even without DNA damage.","method":"Pict1 knockout mice and ES cells, co-immunoprecipitation, ubiquitination assays, genetic rescue experiments","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, in vivo knockout, mechanistic rescue, replicated across multiple model systems","pmids":["21804542"],"is_preprint":false},{"year":2006,"finding":"PICT-1 (NOP53) binds and stabilizes PTEN protein; RNAi knockdown of PICT-1 downregulates endogenous PTEN, activates PI3K/AKT signaling, promotes cell proliferation, and reduces apoptosis in a PTEN-dependent manner.","method":"RNAi knockdown, Western blot, PIP3 downstream effector phosphorylation assays, anchorage-independent growth assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal functional assays with PTEN-null control cells confirming PTEN dependency","pmids":["16971513"],"is_preprint":false},{"year":2007,"finding":"GLTSCR2 (NOP53) is a nucleus-localized protein that induces caspase-independent, PTEN-modulated apoptotic cell death when overexpressed, through a mechanism divergent from PTEN-induced death pathways.","method":"Overexpression, co-immunoprecipitation, cell death assays, caspase activity assays","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 — clean loss/gain of function with defined phenotypic readout; single lab","pmids":["17657248"],"is_preprint":false},{"year":2012,"finding":"Under ribosomal stress, GLTSCR2 (NOP53) translocates from the nucleolus to the nucleoplasm where it directly interacts with and stabilizes p53, inhibiting cell cycle progression in an ARF-independent manner.","method":"Co-immunoprecipitation, subcellular fractionation, immunofluorescence, xenograft tumor model, siRNA knockdown","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including in vivo xenograft, direct interaction and ARF-independence demonstrated","pmids":["22522597"],"is_preprint":false},{"year":2017,"finding":"The crystal structure of S. cerevisiae Mtr4 bound to Nop53 at 3.2 Å resolution reveals that the KOW domain of Mtr4 recognizes the arch-interacting motif (AIM) of Nop53 through hydrophobic and electrostatic interactions; NMR shows the KOW domain can simultaneously bind AIM-containing protein and structured RNA at adjacent surfaces.","method":"X-ray crystallography (3.2 Å), NMR, mutagenesis","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure plus NMR with functional validation of binding interfaces","pmids":["28883156"],"is_preprint":false},{"year":2011,"finding":"GLTSCR2 (NOP53) is involved in the DNA damage response; its expression increases under genotoxic conditions, it mobilizes to the nucleoplasm, and its knockdown attenuates phosphorylation of ATM, ATR, Chk1, Chk2, and H2AX, delays DNA repair, and abolishes G2/M checkpoint activation.","method":"siRNA knockdown, immunofluorescence, Western blot for DDR kinase phosphorylation, flow cytometry, colony survival assay","journal":"The American journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 — clean knockdown with multiple defined phosphoprotein readouts; single lab","pmids":["21741933"],"is_preprint":false},{"year":2014,"finding":"Nucleolar stress induces ubiquitin-independent, 20S proteasome-mediated degradation of PICT1 (NOP53); nucleolar localization is required for stress-induced degradation, as a nucleoplasmic mutant is resistant to stress-induced but not in vitro degradation.","method":"Proteasome inhibitors, E1 ubiquitin-activating enzyme inhibitor, genetic inactivation, in vitro 20S proteasome degradation assay, nucleoplasmic localization mutant","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution of 20S proteasome degradation plus mutagenesis and genetic controls","pmids":["24923447"],"is_preprint":false},{"year":2016,"finding":"DNA damage triggers ATM-dependent phosphorylation of PICT-1 at S233 and T289, leading to its proteasomal degradation, release of RPL11 from the nucleolus, increased RPL11-MDM2 binding, and p53 accumulation/apoptosis.","method":"ATM inhibitors (wortmannin, KU55933), phosphosite mutagenesis (S233A/T289A alanine and S233D/T289D phosphomimetic mutants), co-immunoprecipitation, immunofluorescence","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 1–2 — phosphosite mutagenesis with phosphomimetic controls, inhibitor validation, multiple orthogonal readouts","pmids":["27829214"],"is_preprint":false},{"year":2010,"finding":"PICT-1 (NOP53) localizes to the nucleolus and interacts with Ser518-dephosphorylated merlin (growth-inhibitory form) in the nucleolus; the PICT-1 C-terminal truncation mutant (1-356) that loses merlin binding has markedly reduced inhibitory effects on cell cycle and proliferation.","method":"Co-immunoprecipitation, confocal microscopy, siRNA knockdown of merlin, overexpression of truncation mutants, flow cytometry","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP with deletion mapping and functional knockdown confirmation; single lab","pmids":["21167305"],"is_preprint":false},{"year":2016,"finding":"PICT-1 (NOP53) overexpression triggers pro-death autophagy by directly binding ribosomal DNA (rDNA) gene loci and interacting with UBF to inhibit phosphorylation of UBF and recruitment of RNA Pol I to the rDNA promoter, suppressing rRNA transcription and inactivating AKT/mTOR/p70S6K signaling.","method":"ChIP (chromatin immunoprecipitation), co-immunoprecipitation, deletion mutant analysis, Pol I inhibitor CX-5461 comparison, Western blot for mTOR pathway components","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP and Co-IP with deletion mutant controls; single lab","pmids":["27729611"],"is_preprint":false},{"year":2009,"finding":"PICT-1 (NOP53) interacts with KSHV KS-Bcl-2 and sequesters it from mitochondria to the nucleolus; this nucleolar targeting correlates with reduction of KS-Bcl-2 antiapoptotic activity, and knockdown of PICT-1 abolishes nucleolar localization of KS-Bcl-2.","method":"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, siRNA knockdown, deletion mapping of interaction domains","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2–3 — yeast two-hybrid confirmed by Co-IP and functional localization assay; single lab","pmids":["20042497"],"is_preprint":false},{"year":2012,"finding":"PICT-1/GLTSCR2 (NOP53) nucleolar localization is mediated by two independent nucleolar localization sequences (NoLS) containing arginine and leucine clusters; its nucleolar distribution resembles rRNA processing factors but does not precisely colocalize with UBF1 or Fibrillarin.","method":"Confocal microscopy of EGFP and myc-tagged fusion proteins, deletion mapping","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct imaging with systematic deletion mapping; single lab","pmids":["22292050"],"is_preprint":false},{"year":2014,"finding":"PICT-1 (NOP53) forms homo-oligomers (primarily dimers) mediated by its carboxy-terminal domain, as shown by yeast two-hybrid, co-immunoprecipitation, FRET, microfluidic affinity binding, glutaraldehyde cross-linking, and gel filtration.","method":"Yeast two-hybrid, co-immunoprecipitation, FRET, in vitro microfluidic affinity binding, glutaraldehyde cross-linking, gel filtration","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods including in vitro direct binding assay confirming self-association and domain mapping","pmids":["24735870"],"is_preprint":false},{"year":2015,"finding":"GLTSCR2 (NOP53) inhibits the NPM-MYC oncogenic axis: redistributed GLTSCR2 in the nucleoplasm competitively binds NPM, inhibiting formation of the NPM-MYC binary complex and reducing NPM-MYC recruitment to MYC target gene promoters, thereby suppressing MYC transcriptional activity.","method":"Co-immunoprecipitation, chromatin immunoprecipitation (ChIP), luciferase reporter assay, colony formation assay","journal":"The American journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP and ChIP with functional reporter assay; single lab","pmids":["25956029"],"is_preprint":false},{"year":2015,"finding":"GLTSCR2 (NOP53) acts as an upstream negative regulator of nucleophosmin (NPM): it induces nucleoplasmic translocation and proteasomal polyubiquitination-dependent degradation of NPM, and decreases NPM-mediated transforming activity.","method":"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, proteasome inhibitor treatment, shRNA knockdown","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple assays showing interaction, localization change, and degradation mechanism; single lab","pmids":["25818168"],"is_preprint":false},{"year":2017,"finding":"GLTSCR2 (NOP53) promotes translocation of ARF from the nucleolus to the nucleoplasm, increases ARF binding to the E3 ubiquitin ligase ULF/TRIP12, and enhances ARF degradation through the polyubiquitination pathway.","method":"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, overexpression and knockdown","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP and ubiquitination assay demonstrating mechanism; single lab","pmids":["27323397"],"is_preprint":false},{"year":2016,"finding":"Viral infection induces cytoplasmic translocation of GLTSCR2 (NOP53), where it interacts with RIG-I and USP15; this triple interaction promotes USP15-mediated removal of K63-linked ubiquitination from RIG-I, attenuating RIG-I signaling and type I IFN-β production to support viral replication. Deletion of the nuclear export sequence (NES) abolishes this activity.","method":"Co-immunoprecipitation, ubiquitination assays, NES deletion mutant, RIG-I activation assays, IFN-β reporter assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal assays with NES deletion control; single lab","pmids":["27824081"],"is_preprint":false},{"year":2018,"finding":"HSV-1 viral protein γ34.5 induces cytoplasmic translocation of NOP53; cytoplasmic NOP53 facilitates γ34.5 recruitment of protein phosphatase PP1α to dephosphorylate eIF2α, enabling efficient viral translation. NOP53 knockdown disrupts the γ34.5-PP1α interaction and impairs HSV-1 virulence in vivo.","method":"Co-immunoprecipitation, eIF2α phosphorylation assays, viral yield assays, NOP53 knockdown (shRNA), in vivo mouse infection model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with functional in vivo validation; single lab","pmids":["29367603"],"is_preprint":false},{"year":2016,"finding":"JNK phosphorylation of c-Jun is required for nucleolar retention and protein stability of GLTSCR2 (NOP53); inhibition of JNK (with SP600125) or addition of c-Jun peptide induces nucleoplasmic translocation of GLTSCR2 and its proteasomal polyubiquitination-dependent degradation, possibly by reducing GLTSCR2 monomer binding affinity.","method":"Kinase inhibitor treatment, immunocytochemistry, immunoblot, cycloheximide chase, ubiquitination assay, co-immunoprecipitation","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple assays linking JNK-c-Jun axis to GLTSCR2 localization and stability; single lab","pmids":["26903295"],"is_preprint":false},{"year":2014,"finding":"GLTSCR2/PICT1 (NOP53) enhances mitochondrial function and maintains oxygen consumption; it controls cellular proliferation and metabolism via the transcription factor Myc, and is induced by mitochondrial stress.","method":"High-throughput overexpression screen, flow cytometry, RNAi in C. elegans (ortholog), respiration assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — functional screen with ortholog validation across species; single lab","pmids":["24556985"],"is_preprint":false},{"year":2019,"finding":"Yeast Nop53 (ortholog of NOP53) acts as an adaptor recruiting the RNA exosome to pre-60S particles; it interacts with the 25S rRNA, the exosome catalytic subunit Rrp6, and the helicase Mtr4; proteomic analysis shows the exosome binds pre-ribosomal complexes earlier during ribosome maturation than previously thought.","method":"Co-immunoprecipitation, mass spectrometry (proteomics), yeast genetics, sucrose gradient sedimentation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — proteomics-based interactome with genetic and biochemical validation in yeast","pmids":["31662437"],"is_preprint":false},{"year":2021,"finding":"Yeast Nop53 (ortholog of NOP53) has a structural role in stabilizing the pre-60S foot interface and facilitating transition from nucleolar state E particle to nuclear stages; Nop53 depletion (unlike AIM-motif mutants) causes retention of unprocessed foot in late pre-60S intermediates and impairs late maturation events including Yvh1 recruitment.","method":"Yeast Nop53 depletion, AIM-motif mutant analysis, polysome profiling, mass spectrometry, Northern blot for pre-rRNA intermediates","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 — comprehensive biochemical analysis with mutant controls; single lab","pmids":["34125911"],"is_preprint":false},{"year":2022,"finding":"Human PICT1/NOP53 interacts with MTR4 and the RNA exosome in an arch-interacting motif (AIM)-dependent manner and is required for two distinct pre-rRNA processing steps: early cleavage of 32S intermediate RNA and late maturation of 12S precursor into 5.8S rRNA; only the late step requires AIM-dependent recruitment of MTR4 and exosome. Depletion of PICT1 or MTR4 (but not exosome catalytic subunits RRP6/DIS3) induces p53 stabilization.","method":"Co-immunoprecipitation, siRNA depletion, AIM-sequence mutant overexpression, Northern blot for pre-rRNA intermediates, Western blot for p53","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal approaches in human cells with AIM-mutant dissection of two distinct processing steps","pmids":["36403484"],"is_preprint":false},{"year":2021,"finding":"NOP53 suppresses autophagy through two divergent pathways: (1) a ZKSCAN3-dependent pathway where NOP53 transcriptionally activates autophagy suppressor ZKSCAN3 to inhibit LC3B induction; (2) a ZKSCAN3-independent pathway where NOP53 physically interacts with histone H3 and promotes dephosphorylation of H3 at S10, transcriptionally downregulating ATG7 and ATG12.","method":"siRNA knockdown, co-immunoprecipitation, chromatin immunoprecipitation, luciferase reporter assay, histone H3 phosphorylation assay, autophagy flux assays","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal assays establishing two distinct mechanistic pathways; single lab","pmids":["34502226"],"is_preprint":false},{"year":2022,"finding":"NOP53 undergoes liquid-liquid phase separation (LLPS) in vivo and in vitro; the intrinsically disordered region 1 (IDR1) is required for LLPS, while multivalent arginine-rich linear motifs (M-R motifs) are essential for nucleolar localization but dispensable for LLPS. NOP53 silencing sensitizes colorectal cancer cells to radiotherapy and negatively regulates the p53 pathway.","method":"In vitro droplet formation assay, FRAP, 1,6-hexanediol sensitivity, IDR1 deletion mutant, M-R motif mutagenesis, shRNA knockdown, clonogenic survival assay","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo LLPS with multiple biophysical validations and domain mutagenesis; single lab","pmids":["36316314"],"is_preprint":false},{"year":2018,"finding":"NOP53 knockdown causes abnormal nuclear morphology (large/irregular nuclei, multinucleated cells), aberrant chromosome congression in metaphase, spindle checkpoint activation, delayed mitosis, and chromosomal instability (micronuclei, nuclear buds); re-expression of NOP53 rescues these defects.","method":"shRNA knockdown, rescue by re-expression, immunofluorescence, live-cell imaging, Giemsa staining, flow cytometry","journal":"Pathology oncology research : POR","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function with rescue and multiple cellular phenotype readouts; single lab","pmids":["30421090"],"is_preprint":false},{"year":2024,"finding":"PICT1 (NOP53) interacts with MRE11, a DNA damage repair factor; PICT1 deletion in alveolar type II cells leads to mitochondrial and nuclear ROS accumulation, cell cycle arrest, mitochondrial and nuclear DNA damage, decreased mitochondrial respiration, and impaired DNA damage repair.","method":"Co-immunoprecipitation followed by mass spectrometry (identifying MRE11 as novel interactor), PICT1 deletion, ROS assay, mitochondrial respiration assay, comet assay","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP/MS identifying novel interactor with functional deletion phenotype; single lab","pmids":["39578839"],"is_preprint":false},{"year":2021,"finding":"PICT1 (NOP53) overexpression in medullary thyroid (TT) cells induces production of p53β (a p53 splice variant lacking C-terminus), decreases p21 expression, elevates cell viability, and reduces PTEN expression while increasing phospho-Akt-Ser47, suggesting a role in spliceosome regulation and mTOR pathway modulation.","method":"Lentiviral overexpression, Western blot, cell viability assay, mTOR pathway protein analysis","journal":"Journal of neuroendocrinology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, overexpression only with limited mechanistic follow-up","pmids":["36306198"],"is_preprint":false}],"current_model":"NOP53 (PICT1/GLTSCR2) is a nucleolar protein that functions as a central hub regulating ribosome biogenesis (recruiting the RNA exosome via its arch-interacting motif to process pre-60S rRNA), the MDM2-p53 tumor suppressor pathway (by retaining RPL11 in the nucleolus to prevent MDM2 inhibition; released upon nucleolar stress or DNA damage through ATM-dependent phosphorylation and ubiquitin-independent 20S proteasomal degradation), and multiple nucleoplasmic signaling axes (stabilizing PTEN, inhibiting NPM-MYC and ARF, suppressing autophagy via ZKSCAN3 and histone H3 dephosphorylation, maintaining chromosomal stability, and attenuating antiviral RIG-I/IFN-β signaling when translocated to the cytoplasm during viral infection)."},"narrative":{"teleology":[{"year":2006,"claim":"The first functional role for NOP53 was established as a stabilizer of the tumor suppressor PTEN, linking it to PI3K/AKT signaling control — answering whether this nucleolar protein had tumor-suppressive signaling functions.","evidence":"RNAi knockdown with PTEN-null controls, Western blot, and AKT phosphorylation readouts in cell lines","pmids":["16971513"],"confidence":"High","gaps":["Mechanism of PTEN stabilization (direct vs. indirect) not determined","Whether PTEN interaction occurs in the nucleolus or nucleoplasm unresolved"]},{"year":2009,"claim":"Discovery that NOP53 can sequester viral Bcl-2 to the nucleolus established the principle that NOP53 functions as a nucleolar tethering factor, a theme recurrent in its biology.","evidence":"Yeast two-hybrid, Co-IP, confocal imaging of KSHV KS-Bcl-2 localization, siRNA knockdown","pmids":["20042497"],"confidence":"Medium","gaps":["Physiological relevance during KSHV infection not tested in vivo","Whether sequestration applies to cellular Bcl-2 family members unknown"]},{"year":2011,"claim":"Two key advances in 2011 defined NOP53 as a central mediator of the ribosomal protein–MDM2–p53 axis and as a participant in the DNA damage response, answering how nucleolar integrity communicates with p53 surveillance.","evidence":"Pict1 knockout mice/ES cells with Co-IP and ubiquitination rescue (RPL11–MDM2 axis); siRNA knockdown with DDR kinase phosphorylation readouts and G2/M checkpoint analysis","pmids":["21804542","21741933"],"confidence":"High","gaps":["Whether RPL11 retention and DDR functions are mechanistically separable was unclear","Identity of the stress signals triggering NOP53 degradation not yet known"]},{"year":2012,"claim":"Demonstration that NOP53 translocates to the nucleoplasm under ribosomal stress where it directly stabilizes p53 in an ARF-independent manner established a second, direct route to p53 activation beyond RPL11 release, and mapping of nucleolar localization sequences defined the structural basis for compartmentalization.","evidence":"Co-IP, subcellular fractionation, xenograft model, EGFP fusion deletion mapping","pmids":["22522597","22292050"],"confidence":"High","gaps":["Relative contribution of direct p53 stabilization vs. RPL11-MDM2 pathway not quantified","Whether the two NoLS are differentially regulated unknown"]},{"year":2014,"claim":"Three discoveries established the biochemical properties of NOP53 itself and its metabolic connections: homo-oligomerization via the C-terminal domain, ubiquitin-independent 20S proteasomal degradation as the mechanism of stress-induced turnover, and a role in Myc-dependent mitochondrial metabolism.","evidence":"FRET, gel filtration, cross-linking (oligomerization); in vitro 20S proteasome reconstitution with nucleoplasmic mutant (degradation); overexpression screen with C. elegans ortholog validation (metabolism)","pmids":["24735870","24923447","24556985"],"confidence":"High","gaps":["Whether oligomerization state changes upon stress not tested","How 20S proteasome recognizes NOP53 without ubiquitin unclear","Direct Myc targets mediating metabolic effects uncharacterized"]},{"year":2015,"claim":"NOP53 was shown to regulate the NPM–MYC oncogenic axis by competitively binding NPM to disrupt NPM–MYC complex formation at target promoters, and separately to induce NPM proteasomal degradation, establishing NOP53 as a multilayered NPM antagonist.","evidence":"Co-IP, ChIP at MYC target promoters, luciferase reporters, ubiquitination assays with proteasome inhibitors","pmids":["25956029","25818168"],"confidence":"Medium","gaps":["Whether NPM regulation occurs in physiological stress contexts or only upon overexpression not established","Structural basis of NOP53–NPM interaction unknown"]},{"year":2016,"claim":"Multiple 2016 studies resolved upstream regulation and downstream effector mechanisms: JNK/c-Jun signaling maintains nucleolar retention and stability of NOP53; NOP53 binds rDNA and UBF to suppress RNA Pol I transcription and trigger pro-death autophagy; NOP53 promotes ARF degradation via ULF/TRIP12; and ATM-dependent phosphorylation at S233/T289 triggers NOP53 degradation linking DNA damage to p53 activation via RPL11.","evidence":"JNK inhibitor and c-Jun peptide treatment (JNK axis); ChIP at rDNA promoter with CX-5461 comparison (Pol I); Co-IP and ubiquitination assays (ARF); ATM inhibitors with phosphosite mutagenesis (S233A/T289A, S233D/T289D) and Co-IP (ATM axis)","pmids":["26903295","27729611","27323397","27829214"],"confidence":"High","gaps":["How JNK-mediated nucleolar retention and ATM-mediated degradation are coordinately regulated unknown","Whether rDNA binding is direct or UBF-dependent not resolved","Whether ARF degradation occurs under physiological nucleolar stress unclear"]},{"year":2017,"claim":"The 3.2 Å crystal structure of yeast Mtr4 KOW domain bound to the Nop53 AIM peptide revealed the molecular basis for exosome recruitment to pre-ribosomes, and NMR showed simultaneous RNA and protein binding, resolving how Nop53/NOP53 bridges rRNA substrate and processing machinery.","evidence":"X-ray crystallography at 3.2 Å, NMR, mutagenesis of binding interfaces in S. cerevisiae","pmids":["28883156"],"confidence":"High","gaps":["Human NOP53–MTR4 structure not yet determined","Whether AIM–KOW binding is regulated by post-translational modifications unknown"]},{"year":2018,"claim":"NOP53 was implicated in viral exploitation strategies: HSV-1 γ₁34.5 induces cytoplasmic translocation of NOP53 to facilitate PP1α recruitment for eIF2α dephosphorylation, and NOP53 knockdown impairs HSV-1 virulence in vivo, establishing NOP53 as a host factor co-opted by viruses.","evidence":"Co-IP, eIF2α phosphorylation assays, shRNA knockdown, mouse infection model","pmids":["29367603"],"confidence":"Medium","gaps":["Whether cytoplasmic NOP53 functions in antiviral RIG-I attenuation and viral eIF2α dephosphorylation are coordinated unknown","Generalizability to other DNA viruses untested"]},{"year":2019,"claim":"Proteomic analysis in yeast established Nop53 as the primary adaptor recruiting the RNA exosome and Rrp6 to pre-60S particles and showed exosome association occurs earlier in ribosome maturation than previously appreciated.","evidence":"Co-IP/mass spectrometry, yeast genetics, sucrose gradient sedimentation in S. cerevisiae","pmids":["31662437"],"confidence":"High","gaps":["Whether human NOP53 recruits exosome at the same maturation stage unconfirmed at this point","Stoichiometry of exosome–Nop53–pre-60S complex not determined"]},{"year":2021,"claim":"Three advances clarified distinct NOP53 functions: a structural role in pre-60S foot stabilization separable from AIM-dependent exosome recruitment (yeast); autophagy suppression via dual ZKSCAN3-dependent and histone H3 S10 dephosphorylation-dependent pathways; and maintenance of chromosomal stability during mitosis.","evidence":"Nop53 depletion vs. AIM mutant with polysome profiling and mass spectrometry (foot stabilization); siRNA, ChIP, histone phosphorylation assays (autophagy); shRNA with rescue, live-cell imaging, micronucleus scoring (chromosomal stability)","pmids":["34125911","34502226","30421090"],"confidence":"Medium","gaps":["Mechanism by which NOP53 promotes H3 S10 dephosphorylation (phosphatase identity) unknown","Whether chromosomal instability phenotype is secondary to ribosome biogenesis defects not excluded","Foot stabilization shown only in yeast"]},{"year":2022,"claim":"Two studies in human cells resolved the dual pre-rRNA processing function of NOP53 (AIM-independent early 32S cleavage and AIM-dependent late 5.8S maturation) and demonstrated that NOP53 undergoes liquid-liquid phase separation via its IDR1, with distinct M-R motifs governing nucleolar localization.","evidence":"AIM mutant complementation with Northern blot for pre-rRNA intermediates (processing); in vitro droplet formation, FRAP, 1,6-hexanediol, IDR1/M-R mutagenesis (LLPS)","pmids":["36403484","36316314"],"confidence":"High","gaps":["Whether LLPS is required for exosome recruitment or ribosome assembly function not tested","How the two processing steps are coordinated mechanistically unclear"]},{"year":2024,"claim":"Identification of MRE11 as a NOP53 interactor connected NOP53 directly to DNA damage repair, with NOP53 deletion causing ROS accumulation, mitochondrial dysfunction, and impaired DNA repair in alveolar type II cells.","evidence":"Co-IP/mass spectrometry identifying MRE11, PICT1 conditional deletion, ROS and comet assays, mitochondrial respiration measurement","pmids":["39578839"],"confidence":"Medium","gaps":["Whether NOP53–MRE11 interaction is direct or bridged by other factors unknown","Mechanism linking NOP53 to mitochondrial ROS control not established","Single cell type studied"]},{"year":null,"claim":"Key unresolved questions include: how NOP53's ribosome biogenesis, p53 surveillance, and signaling functions are hierarchically organized; whether LLPS regulates its stress-sensing switch; the structural basis of human NOP53–MTR4 and NOP53–RPL11 interactions; and how cytoplasmic translocation during viral infection is mechanistically triggered and whether it represents a general innate immune regulatory mechanism.","evidence":"","pmids":[],"confidence":"Low","gaps":["No integrated model connecting ribosome biogenesis defects to the multiple signaling outputs","Human NOP53 structure not available","In vivo validation of many signaling axes limited to single labs"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,20,22]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[20,21]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,13,14,15,16]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[23]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[9]}],"localization":[{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[0,8,11,24]},{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[3,5,13]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[16,17]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[4,20,21,22]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,2,7]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[5,7,26]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[6,14,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,13,16]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[9,23]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,25]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[16]}],"complexes":["pre-60S ribosomal particle","RNA exosome"],"partners":["RPL11","MTR4","NPM1","PTEN","RIG-I","USP15","MRE11","UBF"],"other_free_text":[]},"mechanistic_narrative":"NOP53 (PICT1/GLTSCR2) is a nucleolar protein that serves as a critical nexus linking ribosome biogenesis, the p53 tumor suppressor pathway, and nucleolar stress sensing. In its core ribosome biogenesis function, NOP53 acts as an adaptor recruiting the MTR4 helicase and RNA exosome to pre-60S ribosomal particles via its arch-interacting motif (AIM), mediating both early 32S pre-rRNA cleavage (AIM-independent) and late 5.8S rRNA maturation (AIM-dependent), while also stabilizing the pre-60S foot structure during nuclear export [PMID:36403484, PMID:31662437, PMID:34125911, PMID:28883156]. NOP53 retains RPL11 in the nucleolus under unstressed conditions, preventing RPL11–MDM2 interaction; upon nucleolar stress or DNA damage, ATM-dependent phosphorylation at S233/T289 triggers ubiquitin-independent 20S proteasomal degradation of NOP53, releasing RPL11 to inhibit MDM2 and stabilize p53 [PMID:21804542, PMID:27829214, PMID:24923447]. Beyond ribosome biogenesis, NOP53 stabilizes PTEN to suppress PI3K/AKT signaling, inhibits the NPM–MYC transcriptional axis, promotes ARF degradation via ULF/TRIP12, suppresses autophagy through ZKSCAN3 activation and histone H3 dephosphorylation, maintains chromosomal stability during mitosis, and—when translocated to the cytoplasm during viral infection—attenuates RIG-I/IFN-β antiviral signaling by facilitating USP15-mediated deubiquitination of RIG-I [PMID:16971513, PMID:25956029, PMID:27323397, PMID:34502226, PMID:30421090, PMID:27824081]."},"prefetch_data":{"uniprot":{"accession":"Q9NZM5","full_name":"Ribosome biogenesis protein NOP53","aliases":["Glioma tumor suppressor candidate region gene 2 protein","Protein interacting with carboxyl terminus 1","PICT-1","p60"],"length_aa":478,"mass_kda":54.4,"function":"Nucleolar protein which is involved in the integration of the 5S RNP into the ribosomal large subunit during ribosome biogenesis (PubMed:24120868). In ribosome biogenesis, may also play a role in rRNA transcription (PubMed:27729611). Also functions as a nucleolar sensor that regulates the activation of p53/TP53 in response to ribosome biogenesis perturbation, DNA damage and other stress conditions (PubMed:21741933, PubMed:24120868, PubMed:27829214). DNA damage or perturbation of ribosome biogenesis disrupt the interaction between NOP53 and RPL11 allowing RPL11 transport to the nucleoplasm where it can inhibit MDM2 and allow p53/TP53 activation (PubMed:24120868, PubMed:27829214). It may also positively regulate the function of p53/TP53 in cell cycle arrest and apoptosis through direct interaction, preventing its MDM2-dependent ubiquitin-mediated proteasomal degradation (PubMed:22522597). Originally identified as a tumor suppressor, it may also play a role in cell proliferation and apoptosis by positively regulating the stability of PTEN, thereby antagonizing the PI3K-AKT/PKB signaling pathway (PubMed:15355975, PubMed:16971513, PubMed:27729611). May also inhibit cell proliferation and increase apoptosis through its interaction with NF2 (PubMed:21167305). May negatively regulate NPM1 by regulating its nucleoplasmic localization, oligomerization and ubiquitin-mediated proteasomal degradation (PubMed:25818168). Thereby, may prevent NPM1 interaction with MYC and negatively regulate transcription mediated by the MYC-NPM1 complex (PubMed:25956029). May also regulate cellular aerobic respiration (PubMed:24556985). In the cellular response to viral infection, may play a role in the attenuation of interferon-beta through the inhibition of RIGI (PubMed:27824081)","subcellular_location":"Nucleus, nucleolus; Nucleus, nucleoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NZM5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/NOP53","classification":"Common Essential","n_dependent_lines":966,"n_total_lines":1208,"dependency_fraction":0.7996688741721855},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000105373","cell_line_id":"CID001056","localizations":[{"compartment":"nucleolus_gc","grade":3}],"interactors":[],"url":"https://opencell.sf.czbiohub.org/target/CID001056","total_profiled":1310},"omim":[{"mim_id":"605691","title":"RIBOSOME BIOGENESIS FACTOR NOP53; NOP53","url":"https://www.omim.org/entry/605691"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoli","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NOP53"},"hgnc":{"alias_symbol":["PICT-1","PICT1"],"prev_symbol":["GLTSCR2"]},"alphafold":{"accession":"Q9NZM5","domains":[{"cath_id":"-","chopping":"50-83","consensus_level":"medium","plddt":86.03,"start":50,"end":83},{"cath_id":"-","chopping":"412-455","consensus_level":"medium","plddt":90.8957,"start":412,"end":455}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZM5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZM5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZM5-F1-predicted_aligned_error_v6.png","plddt_mean":78.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NOP53","jax_strain_url":"https://www.jax.org/strain/search?query=NOP53"},"sequence":{"accession":"Q9NZM5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NZM5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NZM5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZM5"}},"corpus_meta":[{"pmid":"21804542","id":"PMC_21804542","title":"Regulation 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subunits","date":"2025-03-01","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.25.640171","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":25247,"output_tokens":6537,"usd":0.086898},"stage2":{"model":"claude-opus-4-6","input_tokens":10237,"output_tokens":4158,"usd":0.232703},"total_usd":0.319601,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"PICT1 (NOP53) binds RPL11 and retains it in the nucleolus; loss of PICT1 releases RPL11 to the nucleoplasm where it binds MDM2 and blocks MDM2-mediated ubiquitination of p53, leading to p53 accumulation and G1 arrest/apoptosis even without DNA damage.\",\n      \"method\": \"Pict1 knockout mice and ES cells, co-immunoprecipitation, ubiquitination assays, genetic rescue experiments\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, in vivo knockout, mechanistic rescue, replicated across multiple model systems\",\n      \"pmids\": [\"21804542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PICT-1 (NOP53) binds and stabilizes PTEN protein; RNAi knockdown of PICT-1 downregulates endogenous PTEN, activates PI3K/AKT signaling, promotes cell proliferation, and reduces apoptosis in a PTEN-dependent manner.\",\n      \"method\": \"RNAi knockdown, Western blot, PIP3 downstream effector phosphorylation assays, anchorage-independent growth assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal functional assays with PTEN-null control cells confirming PTEN dependency\",\n      \"pmids\": [\"16971513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"GLTSCR2 (NOP53) is a nucleus-localized protein that induces caspase-independent, PTEN-modulated apoptotic cell death when overexpressed, through a mechanism divergent from PTEN-induced death pathways.\",\n      \"method\": \"Overexpression, co-immunoprecipitation, cell death assays, caspase activity assays\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean loss/gain of function with defined phenotypic readout; single lab\",\n      \"pmids\": [\"17657248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Under ribosomal stress, GLTSCR2 (NOP53) translocates from the nucleolus to the nucleoplasm where it directly interacts with and stabilizes p53, inhibiting cell cycle progression in an ARF-independent manner.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, immunofluorescence, xenograft tumor model, siRNA knockdown\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including in vivo xenograft, direct interaction and ARF-independence demonstrated\",\n      \"pmids\": [\"22522597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The crystal structure of S. cerevisiae Mtr4 bound to Nop53 at 3.2 Å resolution reveals that the KOW domain of Mtr4 recognizes the arch-interacting motif (AIM) of Nop53 through hydrophobic and electrostatic interactions; NMR shows the KOW domain can simultaneously bind AIM-containing protein and structured RNA at adjacent surfaces.\",\n      \"method\": \"X-ray crystallography (3.2 Å), NMR, mutagenesis\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure plus NMR with functional validation of binding interfaces\",\n      \"pmids\": [\"28883156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GLTSCR2 (NOP53) is involved in the DNA damage response; its expression increases under genotoxic conditions, it mobilizes to the nucleoplasm, and its knockdown attenuates phosphorylation of ATM, ATR, Chk1, Chk2, and H2AX, delays DNA repair, and abolishes G2/M checkpoint activation.\",\n      \"method\": \"siRNA knockdown, immunofluorescence, Western blot for DDR kinase phosphorylation, flow cytometry, colony survival assay\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockdown with multiple defined phosphoprotein readouts; single lab\",\n      \"pmids\": [\"21741933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Nucleolar stress induces ubiquitin-independent, 20S proteasome-mediated degradation of PICT1 (NOP53); nucleolar localization is required for stress-induced degradation, as a nucleoplasmic mutant is resistant to stress-induced but not in vitro degradation.\",\n      \"method\": \"Proteasome inhibitors, E1 ubiquitin-activating enzyme inhibitor, genetic inactivation, in vitro 20S proteasome degradation assay, nucleoplasmic localization mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution of 20S proteasome degradation plus mutagenesis and genetic controls\",\n      \"pmids\": [\"24923447\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"DNA damage triggers ATM-dependent phosphorylation of PICT-1 at S233 and T289, leading to its proteasomal degradation, release of RPL11 from the nucleolus, increased RPL11-MDM2 binding, and p53 accumulation/apoptosis.\",\n      \"method\": \"ATM inhibitors (wortmannin, KU55933), phosphosite mutagenesis (S233A/T289A alanine and S233D/T289D phosphomimetic mutants), co-immunoprecipitation, immunofluorescence\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — phosphosite mutagenesis with phosphomimetic controls, inhibitor validation, multiple orthogonal readouts\",\n      \"pmids\": [\"27829214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PICT-1 (NOP53) localizes to the nucleolus and interacts with Ser518-dephosphorylated merlin (growth-inhibitory form) in the nucleolus; the PICT-1 C-terminal truncation mutant (1-356) that loses merlin binding has markedly reduced inhibitory effects on cell cycle and proliferation.\",\n      \"method\": \"Co-immunoprecipitation, confocal microscopy, siRNA knockdown of merlin, overexpression of truncation mutants, flow cytometry\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP with deletion mapping and functional knockdown confirmation; single lab\",\n      \"pmids\": [\"21167305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PICT-1 (NOP53) overexpression triggers pro-death autophagy by directly binding ribosomal DNA (rDNA) gene loci and interacting with UBF to inhibit phosphorylation of UBF and recruitment of RNA Pol I to the rDNA promoter, suppressing rRNA transcription and inactivating AKT/mTOR/p70S6K signaling.\",\n      \"method\": \"ChIP (chromatin immunoprecipitation), co-immunoprecipitation, deletion mutant analysis, Pol I inhibitor CX-5461 comparison, Western blot for mTOR pathway components\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP and Co-IP with deletion mutant controls; single lab\",\n      \"pmids\": [\"27729611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PICT-1 (NOP53) interacts with KSHV KS-Bcl-2 and sequesters it from mitochondria to the nucleolus; this nucleolar targeting correlates with reduction of KS-Bcl-2 antiapoptotic activity, and knockdown of PICT-1 abolishes nucleolar localization of KS-Bcl-2.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, siRNA knockdown, deletion mapping of interaction domains\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — yeast two-hybrid confirmed by Co-IP and functional localization assay; single lab\",\n      \"pmids\": [\"20042497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PICT-1/GLTSCR2 (NOP53) nucleolar localization is mediated by two independent nucleolar localization sequences (NoLS) containing arginine and leucine clusters; its nucleolar distribution resembles rRNA processing factors but does not precisely colocalize with UBF1 or Fibrillarin.\",\n      \"method\": \"Confocal microscopy of EGFP and myc-tagged fusion proteins, deletion mapping\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct imaging with systematic deletion mapping; single lab\",\n      \"pmids\": [\"22292050\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PICT-1 (NOP53) forms homo-oligomers (primarily dimers) mediated by its carboxy-terminal domain, as shown by yeast two-hybrid, co-immunoprecipitation, FRET, microfluidic affinity binding, glutaraldehyde cross-linking, and gel filtration.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, FRET, in vitro microfluidic affinity binding, glutaraldehyde cross-linking, gel filtration\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including in vitro direct binding assay confirming self-association and domain mapping\",\n      \"pmids\": [\"24735870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GLTSCR2 (NOP53) inhibits the NPM-MYC oncogenic axis: redistributed GLTSCR2 in the nucleoplasm competitively binds NPM, inhibiting formation of the NPM-MYC binary complex and reducing NPM-MYC recruitment to MYC target gene promoters, thereby suppressing MYC transcriptional activity.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation (ChIP), luciferase reporter assay, colony formation assay\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP and ChIP with functional reporter assay; single lab\",\n      \"pmids\": [\"25956029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GLTSCR2 (NOP53) acts as an upstream negative regulator of nucleophosmin (NPM): it induces nucleoplasmic translocation and proteasomal polyubiquitination-dependent degradation of NPM, and decreases NPM-mediated transforming activity.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, proteasome inhibitor treatment, shRNA knockdown\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple assays showing interaction, localization change, and degradation mechanism; single lab\",\n      \"pmids\": [\"25818168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GLTSCR2 (NOP53) promotes translocation of ARF from the nucleolus to the nucleoplasm, increases ARF binding to the E3 ubiquitin ligase ULF/TRIP12, and enhances ARF degradation through the polyubiquitination pathway.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, overexpression and knockdown\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP and ubiquitination assay demonstrating mechanism; single lab\",\n      \"pmids\": [\"27323397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Viral infection induces cytoplasmic translocation of GLTSCR2 (NOP53), where it interacts with RIG-I and USP15; this triple interaction promotes USP15-mediated removal of K63-linked ubiquitination from RIG-I, attenuating RIG-I signaling and type I IFN-β production to support viral replication. Deletion of the nuclear export sequence (NES) abolishes this activity.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, NES deletion mutant, RIG-I activation assays, IFN-β reporter assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal assays with NES deletion control; single lab\",\n      \"pmids\": [\"27824081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HSV-1 viral protein γ34.5 induces cytoplasmic translocation of NOP53; cytoplasmic NOP53 facilitates γ34.5 recruitment of protein phosphatase PP1α to dephosphorylate eIF2α, enabling efficient viral translation. NOP53 knockdown disrupts the γ34.5-PP1α interaction and impairs HSV-1 virulence in vivo.\",\n      \"method\": \"Co-immunoprecipitation, eIF2α phosphorylation assays, viral yield assays, NOP53 knockdown (shRNA), in vivo mouse infection model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with functional in vivo validation; single lab\",\n      \"pmids\": [\"29367603\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"JNK phosphorylation of c-Jun is required for nucleolar retention and protein stability of GLTSCR2 (NOP53); inhibition of JNK (with SP600125) or addition of c-Jun peptide induces nucleoplasmic translocation of GLTSCR2 and its proteasomal polyubiquitination-dependent degradation, possibly by reducing GLTSCR2 monomer binding affinity.\",\n      \"method\": \"Kinase inhibitor treatment, immunocytochemistry, immunoblot, cycloheximide chase, ubiquitination assay, co-immunoprecipitation\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple assays linking JNK-c-Jun axis to GLTSCR2 localization and stability; single lab\",\n      \"pmids\": [\"26903295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"GLTSCR2/PICT1 (NOP53) enhances mitochondrial function and maintains oxygen consumption; it controls cellular proliferation and metabolism via the transcription factor Myc, and is induced by mitochondrial stress.\",\n      \"method\": \"High-throughput overexpression screen, flow cytometry, RNAi in C. elegans (ortholog), respiration assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional screen with ortholog validation across species; single lab\",\n      \"pmids\": [\"24556985\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Yeast Nop53 (ortholog of NOP53) acts as an adaptor recruiting the RNA exosome to pre-60S particles; it interacts with the 25S rRNA, the exosome catalytic subunit Rrp6, and the helicase Mtr4; proteomic analysis shows the exosome binds pre-ribosomal complexes earlier during ribosome maturation than previously thought.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry (proteomics), yeast genetics, sucrose gradient sedimentation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — proteomics-based interactome with genetic and biochemical validation in yeast\",\n      \"pmids\": [\"31662437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Yeast Nop53 (ortholog of NOP53) has a structural role in stabilizing the pre-60S foot interface and facilitating transition from nucleolar state E particle to nuclear stages; Nop53 depletion (unlike AIM-motif mutants) causes retention of unprocessed foot in late pre-60S intermediates and impairs late maturation events including Yvh1 recruitment.\",\n      \"method\": \"Yeast Nop53 depletion, AIM-motif mutant analysis, polysome profiling, mass spectrometry, Northern blot for pre-rRNA intermediates\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive biochemical analysis with mutant controls; single lab\",\n      \"pmids\": [\"34125911\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Human PICT1/NOP53 interacts with MTR4 and the RNA exosome in an arch-interacting motif (AIM)-dependent manner and is required for two distinct pre-rRNA processing steps: early cleavage of 32S intermediate RNA and late maturation of 12S precursor into 5.8S rRNA; only the late step requires AIM-dependent recruitment of MTR4 and exosome. Depletion of PICT1 or MTR4 (but not exosome catalytic subunits RRP6/DIS3) induces p53 stabilization.\",\n      \"method\": \"Co-immunoprecipitation, siRNA depletion, AIM-sequence mutant overexpression, Northern blot for pre-rRNA intermediates, Western blot for p53\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal approaches in human cells with AIM-mutant dissection of two distinct processing steps\",\n      \"pmids\": [\"36403484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NOP53 suppresses autophagy through two divergent pathways: (1) a ZKSCAN3-dependent pathway where NOP53 transcriptionally activates autophagy suppressor ZKSCAN3 to inhibit LC3B induction; (2) a ZKSCAN3-independent pathway where NOP53 physically interacts with histone H3 and promotes dephosphorylation of H3 at S10, transcriptionally downregulating ATG7 and ATG12.\",\n      \"method\": \"siRNA knockdown, co-immunoprecipitation, chromatin immunoprecipitation, luciferase reporter assay, histone H3 phosphorylation assay, autophagy flux assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal assays establishing two distinct mechanistic pathways; single lab\",\n      \"pmids\": [\"34502226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NOP53 undergoes liquid-liquid phase separation (LLPS) in vivo and in vitro; the intrinsically disordered region 1 (IDR1) is required for LLPS, while multivalent arginine-rich linear motifs (M-R motifs) are essential for nucleolar localization but dispensable for LLPS. NOP53 silencing sensitizes colorectal cancer cells to radiotherapy and negatively regulates the p53 pathway.\",\n      \"method\": \"In vitro droplet formation assay, FRAP, 1,6-hexanediol sensitivity, IDR1 deletion mutant, M-R motif mutagenesis, shRNA knockdown, clonogenic survival assay\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo LLPS with multiple biophysical validations and domain mutagenesis; single lab\",\n      \"pmids\": [\"36316314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NOP53 knockdown causes abnormal nuclear morphology (large/irregular nuclei, multinucleated cells), aberrant chromosome congression in metaphase, spindle checkpoint activation, delayed mitosis, and chromosomal instability (micronuclei, nuclear buds); re-expression of NOP53 rescues these defects.\",\n      \"method\": \"shRNA knockdown, rescue by re-expression, immunofluorescence, live-cell imaging, Giemsa staining, flow cytometry\",\n      \"journal\": \"Pathology oncology research : POR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with rescue and multiple cellular phenotype readouts; single lab\",\n      \"pmids\": [\"30421090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PICT1 (NOP53) interacts with MRE11, a DNA damage repair factor; PICT1 deletion in alveolar type II cells leads to mitochondrial and nuclear ROS accumulation, cell cycle arrest, mitochondrial and nuclear DNA damage, decreased mitochondrial respiration, and impaired DNA damage repair.\",\n      \"method\": \"Co-immunoprecipitation followed by mass spectrometry (identifying MRE11 as novel interactor), PICT1 deletion, ROS assay, mitochondrial respiration assay, comet assay\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP/MS identifying novel interactor with functional deletion phenotype; single lab\",\n      \"pmids\": [\"39578839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PICT1 (NOP53) overexpression in medullary thyroid (TT) cells induces production of p53β (a p53 splice variant lacking C-terminus), decreases p21 expression, elevates cell viability, and reduces PTEN expression while increasing phospho-Akt-Ser47, suggesting a role in spliceosome regulation and mTOR pathway modulation.\",\n      \"method\": \"Lentiviral overexpression, Western blot, cell viability assay, mTOR pathway protein analysis\",\n      \"journal\": \"Journal of neuroendocrinology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, overexpression only with limited mechanistic follow-up\",\n      \"pmids\": [\"36306198\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NOP53 (PICT1/GLTSCR2) is a nucleolar protein that functions as a central hub regulating ribosome biogenesis (recruiting the RNA exosome via its arch-interacting motif to process pre-60S rRNA), the MDM2-p53 tumor suppressor pathway (by retaining RPL11 in the nucleolus to prevent MDM2 inhibition; released upon nucleolar stress or DNA damage through ATM-dependent phosphorylation and ubiquitin-independent 20S proteasomal degradation), and multiple nucleoplasmic signaling axes (stabilizing PTEN, inhibiting NPM-MYC and ARF, suppressing autophagy via ZKSCAN3 and histone H3 dephosphorylation, maintaining chromosomal stability, and attenuating antiviral RIG-I/IFN-β signaling when translocated to the cytoplasm during viral infection).\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NOP53 (PICT1/GLTSCR2) is a nucleolar protein that serves as a critical nexus linking ribosome biogenesis, the p53 tumor suppressor pathway, and nucleolar stress sensing. In its core ribosome biogenesis function, NOP53 acts as an adaptor recruiting the MTR4 helicase and RNA exosome to pre-60S ribosomal particles via its arch-interacting motif (AIM), mediating both early 32S pre-rRNA cleavage (AIM-independent) and late 5.8S rRNA maturation (AIM-dependent), while also stabilizing the pre-60S foot structure during nuclear export [PMID:36403484, PMID:31662437, PMID:34125911, PMID:28883156]. NOP53 retains RPL11 in the nucleolus under unstressed conditions, preventing RPL11–MDM2 interaction; upon nucleolar stress or DNA damage, ATM-dependent phosphorylation at S233/T289 triggers ubiquitin-independent 20S proteasomal degradation of NOP53, releasing RPL11 to inhibit MDM2 and stabilize p53 [PMID:21804542, PMID:27829214, PMID:24923447]. Beyond ribosome biogenesis, NOP53 stabilizes PTEN to suppress PI3K/AKT signaling, inhibits the NPM–MYC transcriptional axis, promotes ARF degradation via ULF/TRIP12, suppresses autophagy through ZKSCAN3 activation and histone H3 dephosphorylation, maintains chromosomal stability during mitosis, and—when translocated to the cytoplasm during viral infection—attenuates RIG-I/IFN-β antiviral signaling by facilitating USP15-mediated deubiquitination of RIG-I [PMID:16971513, PMID:25956029, PMID:27323397, PMID:34502226, PMID:30421090, PMID:27824081].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"The first functional role for NOP53 was established as a stabilizer of the tumor suppressor PTEN, linking it to PI3K/AKT signaling control — answering whether this nucleolar protein had tumor-suppressive signaling functions.\",\n      \"evidence\": \"RNAi knockdown with PTEN-null controls, Western blot, and AKT phosphorylation readouts in cell lines\",\n      \"pmids\": [\"16971513\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of PTEN stabilization (direct vs. indirect) not determined\", \"Whether PTEN interaction occurs in the nucleolus or nucleoplasm unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Discovery that NOP53 can sequester viral Bcl-2 to the nucleolus established the principle that NOP53 functions as a nucleolar tethering factor, a theme recurrent in its biology.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, confocal imaging of KSHV KS-Bcl-2 localization, siRNA knockdown\",\n      \"pmids\": [\"20042497\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance during KSHV infection not tested in vivo\", \"Whether sequestration applies to cellular Bcl-2 family members unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Two key advances in 2011 defined NOP53 as a central mediator of the ribosomal protein–MDM2–p53 axis and as a participant in the DNA damage response, answering how nucleolar integrity communicates with p53 surveillance.\",\n      \"evidence\": \"Pict1 knockout mice/ES cells with Co-IP and ubiquitination rescue (RPL11–MDM2 axis); siRNA knockdown with DDR kinase phosphorylation readouts and G2/M checkpoint analysis\",\n      \"pmids\": [\"21804542\", \"21741933\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RPL11 retention and DDR functions are mechanistically separable was unclear\", \"Identity of the stress signals triggering NOP53 degradation not yet known\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstration that NOP53 translocates to the nucleoplasm under ribosomal stress where it directly stabilizes p53 in an ARF-independent manner established a second, direct route to p53 activation beyond RPL11 release, and mapping of nucleolar localization sequences defined the structural basis for compartmentalization.\",\n      \"evidence\": \"Co-IP, subcellular fractionation, xenograft model, EGFP fusion deletion mapping\",\n      \"pmids\": [\"22522597\", \"22292050\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of direct p53 stabilization vs. RPL11-MDM2 pathway not quantified\", \"Whether the two NoLS are differentially regulated unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Three discoveries established the biochemical properties of NOP53 itself and its metabolic connections: homo-oligomerization via the C-terminal domain, ubiquitin-independent 20S proteasomal degradation as the mechanism of stress-induced turnover, and a role in Myc-dependent mitochondrial metabolism.\",\n      \"evidence\": \"FRET, gel filtration, cross-linking (oligomerization); in vitro 20S proteasome reconstitution with nucleoplasmic mutant (degradation); overexpression screen with C. elegans ortholog validation (metabolism)\",\n      \"pmids\": [\"24735870\", \"24923447\", \"24556985\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether oligomerization state changes upon stress not tested\", \"How 20S proteasome recognizes NOP53 without ubiquitin unclear\", \"Direct Myc targets mediating metabolic effects uncharacterized\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"NOP53 was shown to regulate the NPM–MYC oncogenic axis by competitively binding NPM to disrupt NPM–MYC complex formation at target promoters, and separately to induce NPM proteasomal degradation, establishing NOP53 as a multilayered NPM antagonist.\",\n      \"evidence\": \"Co-IP, ChIP at MYC target promoters, luciferase reporters, ubiquitination assays with proteasome inhibitors\",\n      \"pmids\": [\"25956029\", \"25818168\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NPM regulation occurs in physiological stress contexts or only upon overexpression not established\", \"Structural basis of NOP53–NPM interaction unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Multiple 2016 studies resolved upstream regulation and downstream effector mechanisms: JNK/c-Jun signaling maintains nucleolar retention and stability of NOP53; NOP53 binds rDNA and UBF to suppress RNA Pol I transcription and trigger pro-death autophagy; NOP53 promotes ARF degradation via ULF/TRIP12; and ATM-dependent phosphorylation at S233/T289 triggers NOP53 degradation linking DNA damage to p53 activation via RPL11.\",\n      \"evidence\": \"JNK inhibitor and c-Jun peptide treatment (JNK axis); ChIP at rDNA promoter with CX-5461 comparison (Pol I); Co-IP and ubiquitination assays (ARF); ATM inhibitors with phosphosite mutagenesis (S233A/T289A, S233D/T289D) and Co-IP (ATM axis)\",\n      \"pmids\": [\"26903295\", \"27729611\", \"27323397\", \"27829214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How JNK-mediated nucleolar retention and ATM-mediated degradation are coordinately regulated unknown\", \"Whether rDNA binding is direct or UBF-dependent not resolved\", \"Whether ARF degradation occurs under physiological nucleolar stress unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The 3.2 Å crystal structure of yeast Mtr4 KOW domain bound to the Nop53 AIM peptide revealed the molecular basis for exosome recruitment to pre-ribosomes, and NMR showed simultaneous RNA and protein binding, resolving how Nop53/NOP53 bridges rRNA substrate and processing machinery.\",\n      \"evidence\": \"X-ray crystallography at 3.2 Å, NMR, mutagenesis of binding interfaces in S. cerevisiae\",\n      \"pmids\": [\"28883156\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Human NOP53–MTR4 structure not yet determined\", \"Whether AIM–KOW binding is regulated by post-translational modifications unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"NOP53 was implicated in viral exploitation strategies: HSV-1 γ₁34.5 induces cytoplasmic translocation of NOP53 to facilitate PP1α recruitment for eIF2α dephosphorylation, and NOP53 knockdown impairs HSV-1 virulence in vivo, establishing NOP53 as a host factor co-opted by viruses.\",\n      \"evidence\": \"Co-IP, eIF2α phosphorylation assays, shRNA knockdown, mouse infection model\",\n      \"pmids\": [\"29367603\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether cytoplasmic NOP53 functions in antiviral RIG-I attenuation and viral eIF2α dephosphorylation are coordinated unknown\", \"Generalizability to other DNA viruses untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Proteomic analysis in yeast established Nop53 as the primary adaptor recruiting the RNA exosome and Rrp6 to pre-60S particles and showed exosome association occurs earlier in ribosome maturation than previously appreciated.\",\n      \"evidence\": \"Co-IP/mass spectrometry, yeast genetics, sucrose gradient sedimentation in S. cerevisiae\",\n      \"pmids\": [\"31662437\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether human NOP53 recruits exosome at the same maturation stage unconfirmed at this point\", \"Stoichiometry of exosome–Nop53–pre-60S complex not determined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Three advances clarified distinct NOP53 functions: a structural role in pre-60S foot stabilization separable from AIM-dependent exosome recruitment (yeast); autophagy suppression via dual ZKSCAN3-dependent and histone H3 S10 dephosphorylation-dependent pathways; and maintenance of chromosomal stability during mitosis.\",\n      \"evidence\": \"Nop53 depletion vs. AIM mutant with polysome profiling and mass spectrometry (foot stabilization); siRNA, ChIP, histone phosphorylation assays (autophagy); shRNA with rescue, live-cell imaging, micronucleus scoring (chromosomal stability)\",\n      \"pmids\": [\"34125911\", \"34502226\", \"30421090\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which NOP53 promotes H3 S10 dephosphorylation (phosphatase identity) unknown\", \"Whether chromosomal instability phenotype is secondary to ribosome biogenesis defects not excluded\", \"Foot stabilization shown only in yeast\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Two studies in human cells resolved the dual pre-rRNA processing function of NOP53 (AIM-independent early 32S cleavage and AIM-dependent late 5.8S maturation) and demonstrated that NOP53 undergoes liquid-liquid phase separation via its IDR1, with distinct M-R motifs governing nucleolar localization.\",\n      \"evidence\": \"AIM mutant complementation with Northern blot for pre-rRNA intermediates (processing); in vitro droplet formation, FRAP, 1,6-hexanediol, IDR1/M-R mutagenesis (LLPS)\",\n      \"pmids\": [\"36403484\", \"36316314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LLPS is required for exosome recruitment or ribosome assembly function not tested\", \"How the two processing steps are coordinated mechanistically unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of MRE11 as a NOP53 interactor connected NOP53 directly to DNA damage repair, with NOP53 deletion causing ROS accumulation, mitochondrial dysfunction, and impaired DNA repair in alveolar type II cells.\",\n      \"evidence\": \"Co-IP/mass spectrometry identifying MRE11, PICT1 conditional deletion, ROS and comet assays, mitochondrial respiration measurement\",\n      \"pmids\": [\"39578839\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NOP53–MRE11 interaction is direct or bridged by other factors unknown\", \"Mechanism linking NOP53 to mitochondrial ROS control not established\", \"Single cell type studied\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: how NOP53's ribosome biogenesis, p53 surveillance, and signaling functions are hierarchically organized; whether LLPS regulates its stress-sensing switch; the structural basis of human NOP53–MTR4 and NOP53–RPL11 interactions; and how cytoplasmic translocation during viral infection is mechanistically triggered and whether it represents a general innate immune regulatory mechanism.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No integrated model connecting ribosome biogenesis defects to the multiple signaling outputs\", \"Human NOP53 structure not available\", \"In vivo validation of many signaling axes limited to single labs\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 20, 22]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [20, 21]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 13, 14, 15, 16]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [23]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [0, 8, 11, 24]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [3, 5, 13]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [16, 17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [4, 20, 21, 22]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 2, 7]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [5, 7, 26]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [6, 14, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 13, 16]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [9, 23]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 25]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"complexes\": [\n      \"pre-60S ribosomal particle\",\n      \"RNA exosome\"\n    ],\n    \"partners\": [\n      \"RPL11\",\n      \"MTR4\",\n      \"NPM1\",\n      \"PTEN\",\n      \"RIG-I\",\n      \"USP15\",\n      \"MRE11\",\n      \"UBF\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}