{"gene":"PABPC1","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2007,"finding":"PABPC1 position relative to the stop codon is a critical determinant for PTC definition in NMD: tethering PABPC1 downstream of a premature termination codon (PTC) abolishes NMD in Drosophila, while elongating the 3' UTR of natural stop codons triggers NMD. Depletion of PABPC1 also suppresses NMD independently of translation efficiency effects, indicating PABPC1 has a direct role in mRNA surveillance beyond positional information.","method":"PABPC1 tethering assays, 3' UTR length manipulation, PABPC1 depletion in Drosophila melanogaster cells","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal experimental approaches (tethering, depletion, UTR manipulation) in a focused study, replicated across conditions","pmids":["17318186"],"is_preprint":false},{"year":2009,"finding":"The GW182 silencing domain competes with eIF4G for binding to PABPC1; the GW182–PABPC1 interaction is required for miRNA target deadenylation and translational repression. PABPC1 overexpression suppresses miRNA-mediated silencing. PABPC1 also associates with components of the CCR4-NOT deadenylase complex.","method":"Co-immunoprecipitation, tethering assays, overexpression rescue experiments, interaction domain mapping in Drosophila and human cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, functional competition assays, overexpression rescue, multiple orthogonal methods in one study","pmids":["19797087"],"is_preprint":false},{"year":1997,"finding":"Yeast Pab1 interacts with Rna15, a component of cleavage and polyadenylation factor CF I, and copurifies with CF I. Pab1 participates in controlling poly(A) tail length during polyadenylation in vitro: immunoneutralization or thermosensitive pab1 mutant extracts produce longer poly(A) tails, which are restored by adding recombinant Pab1.","method":"Two-hybrid assay, co-immunoprecipitation, anion-exchange chromatography co-purification, in vitro polyadenylation assay with mutant extracts and recombinant protein add-back","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro reconstitution with add-back, multiple orthogonal methods (two-hybrid, Co-IP, co-purification, in vitro assay)","pmids":["9199303"],"is_preprint":false},{"year":2010,"finding":"Two distinct regions of GW182 proteins interact with PABPC1: one contains a PAM2 motif (binding the PABPC1 MLLE/C-terminal domain) and the second contains M2 and C-terminal sequences mediating indirect binding to the PABPC1 N-terminal domain. A single amino acid substitution in the TNRC6A-C PAM2 motif abolishes the interaction with PABPC1 and impairs GW182 silencing activity.","method":"Co-immunoprecipitation, domain mapping, point mutagenesis, silencing activity assays in Drosophila and human cells","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — point mutagenesis combined with functional silencing assays and Co-IP, multiple species and cell systems","pmids":["21063388"],"is_preprint":false},{"year":2010,"finding":"Yeast Pab1 self-association (oligomerization and circularization) via its proline-rich region and RRM1 domains is required for CCR4 deadenylation in vivo. Self-associated PAB1 multimers and circular PAB1 species are unable to bind poly(A), and removal of RRM3 (which promoted oligomerization) accelerates CCR4 deadenylation, supporting a model where PAB1 self-association removes it from the poly(A) tail to permit deadenylation.","method":"Deletion mutagenesis of PAB1 domains, in vivo deadenylation assays, protein-protein interaction assays, analytical ultracentrifugation","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple domain deletion mutants with in vivo deadenylation readouts plus biophysical characterization of PAB1 conformational states","pmids":["17620415"],"is_preprint":false},{"year":2005,"finding":"Yeast Pab1 shuttles between nucleus and cytoplasm, functioning as export cargo of Xpo1/Crm1 via RanGTP-dependent interaction, and can also exit via the MEX67 mRNA export pathway. Import is mediated by Kap108/Sxm1 through a nuclear localization signal in Pab1's fourth RRM domain. Inhibition of Pab1 nuclear import causes a kinetic delay in mRNA export, and pab1Δ lethality is suppressed by deletion of the nuclear exosome subunit RRP6.","method":"Nuclear export inhibition (LMB treatment), subcellular fractionation, direct binding assay with Xpo1/Crm1, genetic epistasis (rrp6 suppressor), import receptor identification","journal":"RNA","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding to export receptor, functional nuclear import/export experiments, genetic suppressor analysis, multiple orthogonal approaches","pmids":["15769879"],"is_preprint":false},{"year":2011,"finding":"PABPC1 interactions with the cap-binding complex subunit eIF4G and the 40S recruitment factor eIF3, as well as the ribosome release factor eRF3, underlie critical 3'–5' linkage of translation initiation with efficient termination at AUG-proximal PTCs, providing NMD resistance. Translation termination at AUG-proximal PTCs lacks ribosome stalling seen at NMD-sensitive PTCs.","method":"Co-immunoprecipitation of PABPC1 with eIF4G, eIF3, and eRF3; ribosome stalling assays; NMD reporter assays in human cells","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with multiple translation factors, functional ribosome stalling and NMD reporter assays in single lab","pmids":["21989405"],"is_preprint":false},{"year":2016,"finding":"The APRO domain of BTG2 interacts directly with the first RRM domain of PABPC1. The PABPC1 RRM1 and BTG2 APRO domains together are sufficient to stimulate CAF1 deadenylase activity in vitro without other CCR4-NOT subunits. BTG2's interaction with PABPC1 RRM1 is required for BTG2 to control cell proliferation.","method":"In vitro deadenylase activity assay with purified proteins, domain mapping, cell proliferation assay with interaction-deficient mutants","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of deadenylase stimulation with purified components, functional mutagenesis, single lab with multiple orthogonal methods","pmids":["26912148"],"is_preprint":false},{"year":2021,"finding":"MKRN3 E3 ligase ubiquitinates PABPC1 (identified by mass spectrometry proteomics screen as major substrate). MKRN3 missense mutations found in patients substantially compromise MKRN3-mediated PABPC1 ubiquitination. MKRN3 modulates cell proliferation through nonproteolytic PABPC1 ubiquitination, which in turn regulates PABPC1-mediated global protein synthesis.","method":"Mass spectrometry substrate screen, in vitro ubiquitination assay, patient mutation analysis, cell proliferation assays, MKRN3 knockout mouse models","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — MS-based substrate identification, in vitro ubiquitination assay, patient mutation functional validation, in vivo mouse models","pmids":["34143182"],"is_preprint":false},{"year":2022,"finding":"Paip2A competitively binds to the RRM2–RRM3 regions of PABPC1 at the same interface as poly(A), with higher affinity for RRM2 and RRM3 individually than poly(A). Paip2A initially binds RRM2 of poly(A)-bound PABPC1, then displaces RRM3 from poly(A), causing dissociation of the whole PABPC1 molecule and thereby repressing poly(A)-dependent translation.","method":"Isothermal titration calorimetry (ITC), NMR chemical shift perturbation analysis, competition binding experiments with isolated RRM domains","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ITC and NMR with purified proteins, mechanistic model supported by multiple binding measurements, single lab","pmids":["35307347"],"is_preprint":false},{"year":2010,"finding":"Targeting cytosolic PABPC1 to mitochondria (as mtPABP1) coats the mitochondrial poly(A) tail but does not cause transcript decay; instead, it causes marked inhibition of mitochondrial translation, demonstrating that poly(A) tail-binding by PABPC1 is functionally important for translation and that endogenous poly(A)-binding factors interact with the mt-mRNA poly(A) tail to optimize mitochondrial protein synthesis.","method":"Mitochondrial targeting sequence fusion constructs, steady-state mt-mRNA level measurement, mitochondrial translation assay in mammalian cells","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence (translation inhibition), single lab, two readouts (transcript levels and translation)","pmids":["20144953"],"is_preprint":false},{"year":2013,"finding":"Phosphorylation at serine/threonine residues in intrinsically disordered regions flanking PAM2 motifs of PAM2-containing proteins (Tob2, Pan3, Tnrc6c) regulates their interactions with PABPC1; phosphomimetic mutations in these proteins reduce binding to PABPC1 and impair their functions in mRNA turnover and gene silencing.","method":"Phosphorylation state manipulation (kinase activation, phosphatase inhibition), phospho-blocking and phosphomimetic mutants, Co-immunoprecipitation, mRNA stability and gene silencing reporter assays","journal":"RNA","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphomimetic mutagenesis with functional assays, multiple PAM2-containing proteins tested, single lab","pmids":["23340509"],"is_preprint":false},{"year":2017,"finding":"PABPC1 directly interacts with hnRNPLL in T cells and plasma cells. Although PABPC1 is not required for alternative splicing of CD45, it promotes hnRNPLL binding to immunoglobulin mRNA and regulates switching from membrane to secreted IgH isoform through mRNA alternative polyadenylation.","method":"Co-immunoprecipitation, RNA immunoprecipitation, functional switching assays in plasma cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP and RIP with functional immunoglobulin switching assay, single lab","pmids":["28611064"],"is_preprint":false},{"year":2017,"finding":"Regulated changes in poly(A) tail length dynamically control PABPC1 protein synthesis in cardiomyocytes, titrating cellular translation capacity in response to developmental and hypertrophic cues. PABPC1 is identified as a direct regulator of cardiac hypertrophy.","method":"Poly(A) tail length measurements, PABPC1 knockdown and overexpression in cardiomyocytes, cardiac hypertrophy models in vivo and in vitro","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct poly(A) tail length manipulation with translational readout, loss- and gain-of-function in primary cells, single lab","pmids":["28653618"],"is_preprint":false},{"year":2020,"finding":"PABPC1 interacts with AGO2 in the cytoplasm of HCC cells; this interaction increases recruitment of mRNA to RISC and enhances miRNA-mediated inhibition efficiency.","method":"Anti-AGO2 co-immunoprecipitation and mass spectrometry, cytoplasmic fractionation, functional miRNA reporter assays","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP with MS identification, functional RISC recruitment assay, single lab","pmids":["26188282"],"is_preprint":false},{"year":2021,"finding":"LARP1 requires PABPC1 for association with its specific mRNA targets: the mRNA interactome of LARP1 and PABPC1 show high overlap, and PABPC1 depletion reduces LARP1 binding to its mRNA targets including TOP-containing mRNAs. mRNAs bound by both LARP1 and PABPC1 are in a translationally repressed state.","method":"RNA-binding protein capture (mRNA interactome), PABPC1 knockdown effect on LARP1 mRNA binding, polysome profiling","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RBP capture with functional epistasis (PABPC1 KD abrogates LARP1 mRNA association), single lab","pmids":["33332560"],"is_preprint":false},{"year":2020,"finding":"The isolated La-module of LARP1 mediates poly(A) length protection and mRNA stabilization in a manner dependent on its PAM2 motif binding to PABPC1. A point mutation in the PAM2 motif impairs mRNA stabilization and PABP binding in vivo without affecting oligo(A) RNA binding by the purified recombinant La-module in vitro.","method":"PAM2 point mutagenesis, mRNA stability assays in HEK293 cells, in vitro RNA binding assay with recombinant protein, Co-immunoprecipitation","journal":"RNA biology","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — mutagenesis with in vitro binding and in vivo functional assay, single lab","pmids":["33292040"],"is_preprint":false},{"year":2020,"finding":"The viral protease SVV 3Cpro cleaves PABPC1 at residue 437, generating N-terminal (50 kDa) and C-terminal (25 kDa) fragments. PABPC1 inhibits SVV replication, and 3Cpro cleavage of PABPC1 (dependent on active site residues H48 and C160 of 3Cpro) decreases host protein synthesis rates.","method":"Viral infection and protease expression, point mutagenesis of 3Cpro active site, cleavage site mapping, protein synthesis rate measurement","journal":"Pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — active site mutagenesis of protease with cleavage site mapping, functional translation assay, single lab","pmids":["32512928"],"is_preprint":false},{"year":2023,"finding":"USP10 deubiquitinase directly interacts with PABPC1 and removes K27/K29-linked ubiquitin from the RRM2 domain of PABPC1. Deubiquitinated PABPC1 more efficiently couples CLK2 mRNA with eIF4G1, increasing CLK2 translation efficiency and promoting PDAC tumor growth.","method":"Co-immunoprecipitation, deubiquitination assay, linkage-specific ubiquitination analysis, mRNA-protein interaction assay, RRM2 domain mutants, xenograft models","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and deubiquitination assay with domain mapping, functional translation assay, mutant rescue, single lab","pmids":["37757903"],"is_preprint":false},{"year":2022,"finding":"De novo variants in the PABP domain of PABPC1 cluster causing developmental delay weaken the interaction between PABPC1 and PAIP2 (confirmed by co-immunoprecipitation). Pabpc1 knockdown in mouse embryo brain decreases neural progenitor cell proliferation; wild-type Pabpc1 rescues this defect, whereas three of four patient variants do not.","method":"Exome sequencing, co-immunoprecipitation, in silico modeling, in utero electroporation with rescue experiments","journal":"Genetics in medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP interaction validation plus in vivo neural proliferation assay with rescue, single study","pmids":["35511136"],"is_preprint":false},{"year":2021,"finding":"A conserved boxC motif in BTG1 and BTG2 APRO domains is necessary and sufficient for interaction with PABPC1 RRM1, and is required (but not for PRMT1 binding) for stimulation of deadenylation both in cellulo and in vitro.","method":"NMR chemical shift perturbation, mutagenesis, pulldown assays, in vitro and in cellulo deadenylation assays","journal":"RNA biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structural analysis with mutagenesis and in vitro deadenylation reconstitution, single lab with orthogonal biochemical and functional methods","pmids":["34060423"],"is_preprint":false},{"year":2020,"finding":"Crystal structure of the PAM2w variant motif of LARP4B bound to the MLLE domain of PABPC1 was solved, uncovering a new mode of interaction between PAM2 motifs and MLLE domains. Mutational studies in vitro and in vivo validated the structural findings.","method":"X-ray crystallography, in vitro binding mutagenesis, in vivo functional assays","journal":"Biomolecules","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with mutational validation in vitro and in vivo, single lab","pmids":["32517187"],"is_preprint":false},{"year":2012,"finding":"Expanded ATXN2 (CAG42) sequesters PABPC1 into insolubility in cerebellum of knock-in mice, with decreasing soluble PABPC1 levels correlating with progressive ATXN2 insolubility. This sequestration of PABPC1 into insolubility by expanded ATXN2 was validated in human cell culture.","method":"Knock-in mouse model, protein fractionation (soluble vs. insoluble), immunoblot, human cell culture overexpression","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knock-in model plus cell culture validation, multiple tissues analyzed, single lab","pmids":["22956915"],"is_preprint":false},{"year":2001,"finding":"Yeast Ssa (hsp70) physically interacts with both Sis1 (hsp40) and Pab1 (poly(A)-binding protein) preferentially on translating ribosomes; this interaction is mediated by the variable C-terminal domain of Ssa. Depletion of Ssa dramatically reduces the interaction of Pab1 with the translation initiation factor eIF4G, suggesting Ssa is required for proper Pab1-eIF4G interaction.","method":"Subcellular fractionation, co-immunoprecipitation on polysomes, domain mapping, Ssa depletion followed by Pab1-eIF4G interaction assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP on polysomes with domain mapping, depletion experiment showing downstream effect on Pab1-eIF4G interaction, single lab","pmids":["11279042"],"is_preprint":false},{"year":2014,"finding":"In yeast, the Pab1–eRF3 interaction negatively regulates translation termination (deletion of interacting domains produces antisuppression phenotype / decreased readthrough); the Pab1 C-terminal domain role in mRNA stability is independent of eRF3. Yeast eRF3 does not contain a consensus PAM2 motif, indicating a different mode of interaction from metazoan Pab1-eRF3.","method":"Domain deletion analysis, genetic interaction (double deletion), readthrough assays, mRNA stability assays in yeast","journal":"RNA","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with double domain deletions, translation termination functional assay, single lab","pmids":["25411355"],"is_preprint":false},{"year":2025,"finding":"PABPC1 preferentially enhances translation efficiency of leukaemogenic mRNAs with long, highly structured 5' UTRs by forming biomolecular condensates/phase separation in CML blast crisis cells. CRISPR-Cas9 screening identified PABPC1 as a driver of CML blast crisis progression, and genetic or pharmacological inhibition of PABPC1 suppresses CML cell proliferation and overcomes TKI resistance with minimal effects on normal haematopoiesis.","method":"CRISPR-Cas9 high-throughput screen, biomolecular condensate imaging, polysome profiling, translational efficiency analysis, pharmacological inhibition in murine and human CML models","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-scale functional screen validated with multiple orthogonal mechanistic experiments (phase separation, translation efficiency assays, in vivo mouse models), multiple approaches","pmids":["40102686"],"is_preprint":false},{"year":2025,"finding":"SUMOylation of PABPC1 under stress conditions promotes stress granule assembly and selectively stabilizes mRNAs enriched in conserved U-rich elements. SUMOylated PABPC1 interacts with TIA1 to form a PABPC1-SUMO-TIA1 complex that recruits U-rich mRNAs into stress granules, protecting them from degradation and facilitating expression of mitophagy-related genes (FUNDC1, BNIP3L).","method":"SUMOylation assay, stress granule imaging, transcriptome-wide mRNA stability analysis, co-immunoprecipitation of SUMOylated PABPC1 with TIA1, mitophagy assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — SUMOylation biochemistry, transcriptome-wide analysis, Co-IP with TIA1, functional mitophagy readout, single lab with multiple orthogonal methods","pmids":["40774970"],"is_preprint":false},{"year":2025,"finding":"Yeast Pab1 primarily controls translation initiation in vivo by blocking mRNA decapping and decay: auxin-induced Pab1 degradation reduces mRNA and polysome abundance, and this effect is suppressed by deletion of the decapping enzyme catalytic subunit Dcp2. Assembly of the closed-loop mRNP via PABP–eIF4G interaction is dispensable for wild-type translation of most yeast transcripts at normal mRNA levels.","method":"Auxin-inducible degron system for Pab1 depletion, RNA-Seq, Ribo-Seq, dcp2Δ epistasis, polysome profiling","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — auxin-induced depletion with genetic epistasis (dcp2Δ suppressor), transcriptome-wide and ribosome profiling, peer-reviewed and preprint versions concordant","pmids":["40071937"],"is_preprint":false},{"year":2022,"finding":"Acetylation of Pab1 at lysine 131 (K131) reduces stress granule formation upon glucose deprivation and other stressors. Rpd3 deacetylase is the primary enzyme responsible for deacetylation of Pab1-K131. Acetylation mimic at K131 negatively impacts poly(A) RNA binding by Pab1.","method":"Acetylation mimetic mutants, stress granule imaging, EMSA (electromobility shift assay) for poly(A) binding, genetic epistasis with rpd3 mutant","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — acetylation mimetic mutagenesis with functional stress granule and RNA binding assays, genetic deacetylase identification, single lab","pmids":["36572187"],"is_preprint":false},{"year":2024,"finding":"PABPC1 interacts with hnRNPA3 and the RNA exosome complex, and knockdown of PABPC1 increases accumulation of C9orf72 GGGGCC repeat RNA and RNA foci to the same extent as hnRNPA3 knockdown. Proximity ligation assays show PABPC1-hnRNPA3 and PABPC1-RNA exosome co-localize preferentially when repeat RNA is present, supporting PABPC1 as a mediator of polyadenylated GGGGCC repeat RNA degradation.","method":"APEX2-mediated proximity biotinylation, proximity ligation assay, PABPC1 knockdown with repeat RNA accumulation readout","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — proximity biotinylation and ligation assays with functional knockdown, single lab","pmids":["38444607"],"is_preprint":false},{"year":2025,"finding":"EV-D68 3Cpro cleaves PABPC1 to redirect host translation machinery toward viral RNA. Overexpression of PABPC1 inhibits EV-D68 replication and reduces virus-mediated suppression of host translation. This mechanism is conserved in EV-A71 and CV-A16.","method":"Viral protease expression, overexpression rescue assay for viral replication and host translation, comparison across multiple enterovirus species","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — protease cleavage with functional translation and replication assays, multi-enterovirus validation, single lab","pmids":["40294010"],"is_preprint":false},{"year":2024,"finding":"PABPC1 is required for the nuclear retention of newly produced adenosine-rich circRNAs in H9 stem cells: nuclear PABPC1 binds A-rich circRNAs and, in complex with nuclear basket protein TPR, prevents their cytoplasmic export. Decreased nuclear PABPC1 upon neuronal differentiation enables export of A-rich circRNAs (including circRTN4(2,3)) to the cytoplasm, which is required for neurite outgrowth.","method":"Nuclear/cytoplasmic fractionation, PABPC1 manipulation (overexpression/knockdown), A-rich motif mutagenesis in circRNAs, neurite outgrowth assay, co-immunoprecipitation with TPR","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence (neurite outgrowth), circRNA motif mutagenesis, Co-IP with nuclear basket protein, single lab","pmids":["38838666"],"is_preprint":false},{"year":2018,"finding":"PIWIL1 interacts with PABPC1 through its N- and C-terminal domains in an RNA-dependent manner, and binds 3'-UTRs of post-meiotic mRNAs via its N-terminal domain. PIWIL1 augments protein translation together with PABPC1 in the presence of 3'-UTRs of spermiogenic mRNAs, as shown by luciferase reporter assay and polysome profiling.","method":"Co-immunoprecipitation domain mapping, luciferase reporter translation assay, sucrose gradient sedimentation (polysome profiling), heterologous cell system","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain-level Co-IP plus functional translation assay with polysome profiling, single lab","pmids":["29701755"],"is_preprint":false},{"year":2008,"finding":"In yeast, neither the poly(A) tail nor Pab1p is required for NMD: mRNAs lacking poly(A) tails containing a PTC are still NMD substrates, and cells lacking Pab1p retain NMD substrate recognition and destabilization activity. This establishes that the poly(A)/Pab1 model for NMD substrate discrimination does not apply in yeast.","method":"Poly(A)-tail removal constructs, pab1Δ genetic analysis, NMD reporter assays in yeast","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic null mutant (pab1Δ) combined with engineered poly(A)-less mRNAs and NMD reporters, two independent experimental approaches establishing a negative result of broad mechanistic significance","pmids":["18206975"],"is_preprint":false}],"current_model":"PABPC1 is a multifunctional cytoplasmic RNA-binding protein that binds poly(A) tails via its RRM domains and acts as a scaffold for translation initiation (interacting with eIF4G, eIF3, and eRF3 to promote closed-loop mRNP formation and efficient termination), mRNA stabilization (protecting mRNAs from deadenylation and decapping), and mRNA decay (recruiting CCR4-NOT deadenylase complex via GW182 proteins and BTG/Tob factors); its C-terminal MLLE domain interacts with PAM2-containing proteins (GW182, LARP1, LARP4B, Tob2, Pan3) to regulate mRNA stability, while post-translational modifications including nonproteolytic ubiquitination by MKRN3, deubiquitination by USP10, SUMOylation, and acetylation dynamically tune its activity in translation regulation, stress granule assembly, and selective mRNA stabilization; it also shuttles between nucleus and cytoplasm to participate in mRNA export and quality control, and its position relative to stop codons is a key determinant for NMD suppression in higher eukaryotes."},"narrative":{"mechanistic_narrative":"PABPC1 is the principal cytoplasmic poly(A)-binding protein, coating mRNA poly(A) tails through its tandem RRM domains and acting as a central hub that couples poly(A) status to translation, mRNA stability, and surveillance [PMID:35307347, PMID:20144953]. It uses its modular architecture for combinatorial control: the RRM domains engage the poly(A) tail and competing regulators—Paip2A binds the RRM2–RRM3 interface to displace PABPC1 and repress poly(A)-dependent translation [PMID:35307347], while the APRO/boxC domains of BTG1/BTG2 dock on RRM1 to stimulate CAF1/CCR4-NOT deadenylase activity [PMID:26912148, PMID:34060423]. Its C-terminal MLLE domain recognizes PAM2 motifs in a family of effectors, including GW182/TNRC6, LARP1, LARP4B, Tob2, and Pan3, and these PAM2 contacts are tuned by phosphorylation of the flanking disordered regions [PMID:21063388, PMID:23340509, PMID:33292040, PMID:32517187]. Through GW182 and association with the CCR4-NOT complex, PABPC1 enables miRNA-directed deadenylation and silencing, and it cooperates with AGO2 to enhance RISC recruitment [PMID:19797087, PMID:21063388, PMID:26188282], whereas its interactions with eIF4G, eIF3, and the release factor eRF3 link initiation to efficient termination and form the basis of its role in NMD: PABPC1 position relative to the stop codon is a key determinant of premature-termination-codon definition in higher eukaryotes [PMID:19797087, PMID:21989405, PMID:17318186]. A layer of post-translational modification dynamically gates these activities—nonproteolytic ubiquitination by the E3 ligase MKRN3 regulates global protein synthesis and proliferation, USP10-mediated deubiquitination of RRM2 selectively boosts translation of target mRNAs, and stress-induced SUMOylation drives stress-granule assembly via a TIA1 complex that stabilizes U-rich mRNAs [PMID:34143182, PMID:37757903, PMID:40774970]. PABPC1 also shuttles between nucleus and cytoplasm, contributing to mRNA export and to nuclear retention of A-rich circRNAs, and serves as an antiviral target cleaved by enteroviral 3C proteases to shut down host translation [PMID:15769879, PMID:38838666, PMID:32512928, PMID:40294010]. De novo variants in its PABP domain that weaken the PABPC1–PAIP2 interaction cause a developmental-delay disorder and impair neural progenitor proliferation [PMID:35511136].","teleology":[{"year":1997,"claim":"Established that the poly(A)-binding protein is not merely a passive tail coat but an active participant in 3'-end processing, linking it physically to the cleavage/polyadenylation machinery and to control of poly(A) tail length.","evidence":"Two-hybrid, Co-IP, co-purification with CF I component Rna15, and in vitro polyadenylation with pab1 mutant extracts plus recombinant add-back in yeast","pmids":["9199303"],"confidence":"High","gaps":["Did not resolve which RRM domains mediate the CF I interaction","Yeast-based; relevance to metazoan PABPC1 not addressed in this study"]},{"year":2001,"claim":"Showed that the Pab1–eIF4G closed-loop contact required for translation is itself chaperone-dependent, placing Hsp70/Hsp40 upstream of PABP function on translating ribosomes.","evidence":"Polysome Co-IP, domain mapping, and Ssa depletion followed by Pab1–eIF4G interaction assay in yeast","pmids":["11279042"],"confidence":"Medium","gaps":["Mechanism by which Ssa promotes the interaction (folding vs. assembly) not defined","Not tested in metazoan systems"]},{"year":2005,"claim":"Demonstrated that PABP is a nucleocytoplasmic shuttling protein with defined import and export receptors, connecting it to mRNA export rather than confining it to cytoplasmic translation.","evidence":"LMB export inhibition, fractionation, direct Xpo1/Crm1 binding, Kap108/Sxm1 import receptor mapping to RRM4, and rrp6 genetic suppression in yeast","pmids":["15769879"],"confidence":"High","gaps":["Nuclear function distinct from export not delineated","Human PABPC1 shuttling receptors not mapped here"]},{"year":2007,"claim":"Identified PABPC1 position relative to the stop codon as a determinant of premature-termination-codon definition, giving the protein a direct role in mRNA surveillance/NMD.","evidence":"Tethering downstream of a PTC, 3'-UTR elongation, and PABPC1 depletion in Drosophila cells","pmids":["17318186"],"confidence":"High","gaps":["Molecular link between PABPC1 position and the NMD machinery not fully defined","Insect-cell findings"]},{"year":2008,"claim":"Revealed that the poly(A)/Pab1 NMD model is not universal: in yeast neither poly(A) nor Pab1 is required for substrate recognition, sharpening the surveillance role as a higher-eukaryote feature.","evidence":"Poly(A)-less PTC reporters and pab1Δ NMD reporter assays in yeast","pmids":["18206975"],"confidence":"High","gaps":["Does not explain the basis of the metazoan-specific positional dependence","Negative result; what substitutes for Pab1 in yeast NMD unaddressed"]},{"year":2009,"claim":"Mechanistically connected PABPC1 to miRNA silencing by showing GW182 competes with eIF4G for PABPC1 and that this contact is required for target deadenylation and repression.","evidence":"Reciprocal Co-IP, tethering, overexpression rescue, and CCR4-NOT association in Drosophila and human cells","pmids":["19797087"],"confidence":"High","gaps":["Did not map the precise GW182 surfaces (resolved later)","Whether eIF4G displacement is sufficient for repression untested"]},{"year":2010,"claim":"Defined a bipartite GW182–PABPC1 interaction (PAM2/MLLE plus N-terminal contacts) and proved a single PAM2 residue controls silencing, establishing the MLLE–PAM2 module as functionally essential.","evidence":"Domain mapping, point mutagenesis, Co-IP, and silencing assays in Drosophila and human cells","pmids":["21063388"],"confidence":"High","gaps":["Structural basis of MLLE–PAM2 recognition not resolved here","Relative contribution of each contact to deadenylation vs. repression unquantified"]},{"year":2010,"claim":"Proposed that PABP self-association/circularization removes it from the poly(A) tail to license CCR4 deadenylation, coupling PABP conformational state to mRNA turnover.","evidence":"Domain-deletion mutants, in vivo deadenylation, and analytical ultracentrifugation in yeast","pmids":["17620415"],"confidence":"High","gaps":["Trigger for self-association in vivo unknown","Yeast-specific; human PABPC1 oligomerization not tested"]},{"year":2010,"claim":"Showed by ectopic mitochondrial targeting that poly(A) coating by PABPC1 directly governs translation efficiency rather than transcript stability, isolating its translational function on a poly(A) tail.","evidence":"Mitochondrial targeting fusion (mtPABP1), steady-state mt-mRNA measurement, and mitochondrial translation assay in mammalian cells","pmids":["20144953"],"confidence":"Medium","gaps":["Artificial mitochondrial context","Endogenous mitochondrial poly(A)-binding factor identity not established"]},{"year":2011,"claim":"Linked PABPC1's translation-factor contacts (eIF4G, eIF3, eRF3) to NMD resistance at AUG-proximal PTCs, providing a molecular basis for how termination context determines surveillance.","evidence":"Reciprocal Co-IP, ribosome stalling assays, and NMD reporters in human cells","pmids":["21989405"],"confidence":"High","gaps":["Causal order of factor recruitment during termination not resolved","Quantitative contribution of each contact unmeasured"]},{"year":2012,"claim":"Connected PABPC1 to neurodegeneration by showing expanded ATXN2 sequesters it into insolubility, implicating loss of soluble PABPC1 in disease pathology.","evidence":"ATXN2 CAG42 knock-in mouse fractionation/immunoblot and human cell-culture validation","pmids":["22956915"],"confidence":"Medium","gaps":["Functional consequence of PABPC1 sequestration on translation not measured","Causality vs. correlation in disease progression unresolved"]},{"year":2013,"claim":"Established phosphorylation of PAM2-flanking disordered regions as a switch tuning effector binding to PABPC1, adding a regulatory layer to MLLE-mediated interactions.","evidence":"Phosphomimetic/phospho-blocking mutants of Tob2, Pan3, Tnrc6c with Co-IP and mRNA stability/silencing reporters","pmids":["23340509"],"confidence":"Medium","gaps":["Responsible kinases not identified","In vivo signaling contexts that trigger these phosphorylations unknown"]},{"year":2014,"claim":"Distinguished the yeast Pab1–eRF3 termination-regulatory function from its eRF3-independent mRNA-stability role, and showed the metazoan PAM2-based eRF3 contact differs mechanistically from yeast.","evidence":"Domain deletion, genetic epistasis, readthrough and mRNA stability assays in yeast","pmids":["25411355"],"confidence":"Medium","gaps":["Yeast eRF3 binding mode not structurally defined","Direct extrapolation to human eRF3 limited"]},{"year":2016,"claim":"Reconstituted minimal deadenylation stimulation, showing the BTG2 APRO domain plus PABPC1 RRM1 are sufficient to activate CAF1, and linked this contact to proliferation control.","evidence":"In vitro deadenylase assay with purified proteins, domain mapping, proliferation assays with interaction-deficient mutants","pmids":["26912148"],"confidence":"High","gaps":["How RRM1 engagement positions CAF1 on the tail not structurally resolved","Role of full CCR4-NOT in the in vivo reaction not addressed"]},{"year":2017,"claim":"Implicated PABPC1 in immune cell mRNA processing by promoting hnRNPLL binding and IgH membrane-to-secreted isoform switching via alternative polyadenylation.","evidence":"Co-IP, RIP, and functional switching assays in plasma cells","pmids":["28611064"],"confidence":"Medium","gaps":["Mechanism by which PABPC1 favors a specific poly(A) site unclear","Direct vs. indirect effect on hnRNPLL recruitment not separated"]},{"year":2017,"claim":"Demonstrated that poly(A) tail-length control of PABPC1's own synthesis titrates cellular translation capacity, identifying it as a regulator of cardiac hypertrophy.","evidence":"Poly(A) tail measurements, PABPC1 knockdown/overexpression, and in vivo/in vitro hypertrophy models in cardiomyocytes","pmids":["28653618"],"confidence":"Medium","gaps":["Upstream cues setting PABPC1 mRNA tail length not defined","Whether this is tissue-specific unaddressed"]},{"year":2018,"claim":"Showed PABPC1 partners with PIWIL1 to augment translation of spermiogenic mRNAs, extending its translational-activator role to germ-cell post-meiotic gene expression.","evidence":"Domain-level Co-IP, luciferase reporter, and polysome profiling in a heterologous cell system","pmids":["29701755"],"confidence":"Medium","gaps":["Endogenous germ-cell validation limited","RNA-dependence of the interaction not mechanistically dissected"]},{"year":2020,"claim":"Provided the structural basis for MLLE–PAM2 recognition by solving the LARP4B PAM2w–MLLE crystal structure, revealing a new variant binding mode.","evidence":"X-ray crystallography with in vitro and in vivo mutational validation","pmids":["32517187"],"confidence":"High","gaps":["Functional output of LARP4B–PABPC1 binding not quantified here","Generality across other PAM2 variants untested in this structure"]},{"year":2020,"claim":"Established that LARP1's La-module stabilizes mRNA and protects poly(A) length specifically through its PAM2–PABPC1 contact, separating the in vivo stabilization role from intrinsic RNA binding.","evidence":"PAM2 point mutagenesis, mRNA stability assays, in vitro RNA binding, and Co-IP in HEK293 cells","pmids":["33292040"],"confidence":"Medium","gaps":["Mechanism of poly(A) protection (occlusion vs. deadenylase exclusion) not resolved","Single cell system"]},{"year":2020,"claim":"Showed PABPC1 is required for LARP1 to engage its mRNA targets, including TOP mRNAs, placing PABPC1 upstream of LARP1-mediated translational repression.","evidence":"mRNA interactome capture, PABPC1-knockdown effect on LARP1 binding, and polysome profiling","pmids":["33332560"],"confidence":"Medium","gaps":["Whether PABPC1 directly handoffs mRNA to LARP1 or acts indirectly unresolved","Effect on translation of specific targets not quantified per-transcript"]},{"year":2020,"claim":"Identified PABPC1 as an antiviral factor cleaved by SVV 3C protease, showing host poly(A)-binding capacity is targeted to suppress host translation during infection.","evidence":"3Cpro active-site mutagenesis, cleavage-site mapping at residue 437, and protein synthesis rate measurement","pmids":["32512928"],"confidence":"Medium","gaps":["Functional consequence of each cleavage fragment not defined","In vivo relevance to viral pathogenesis unaddressed"]},{"year":2020,"claim":"Showed PABPC1 enhances RISC function by interacting with AGO2 in the cytoplasm to increase mRNA recruitment, deepening its role in miRNA-mediated regulation in cancer cells.","evidence":"Anti-AGO2 Co-IP/MS, cytoplasmic fractionation, and miRNA reporter assays in HCC cells","pmids":["26188282"],"confidence":"Medium","gaps":["Direct vs. RNA-bridged AGO2 contact not distinguished","Single cancer cell context"]},{"year":2021,"claim":"Identified MKRN3 as the E3 ligase that nonproteolytically ubiquitinates PABPC1 to regulate global protein synthesis and proliferation, with patient mutations impairing this activity.","evidence":"MS substrate screen, in vitro ubiquitination, patient mutation analysis, and MKRN3-knockout mouse models","pmids":["34143182"],"confidence":"High","gaps":["Ubiquitin linkage type and modified residues not fully mapped","How nonproteolytic ubiquitin alters PABPC1 activity mechanistically unclear"]},{"year":2021,"claim":"Defined a conserved boxC motif in BTG1/BTG2 APRO domains as necessary and sufficient for PABPC1 RRM1 binding and deadenylation stimulation, refining the deadenylation-activation interface.","evidence":"NMR chemical shift perturbation, mutagenesis, pulldowns, and in vitro/in cellulo deadenylation assays","pmids":["34060423"],"confidence":"High","gaps":["Structural model of the ternary RRM1–boxC–deadenylase assembly not solved","Selectivity between BTG1 and BTG2 functions unaddressed"]},{"year":2022,"claim":"Resolved the molecular logic of Paip2A-mediated translational repression: sequential RRM2 then RRM3 engagement displaces PABPC1 from poly(A), defining a competitive eviction mechanism.","evidence":"ITC, NMR, and competition binding with isolated RRM domains","pmids":["35307347"],"confidence":"High","gaps":["Cellular triggers controlling Paip2A availability not addressed","Kinetics of eviction on full-length mRNP unmeasured"]},{"year":2022,"claim":"Established PABPC1 (PABP domain) as a developmental-delay disease gene, with variants weakening the PAIP2 interaction and failing to support neural progenitor proliferation.","evidence":"Exome sequencing, Co-IP, in silico modeling, and in utero electroporation rescue in mouse embryo brain","pmids":["35511136"],"confidence":"Medium","gaps":["Whether weakened PAIP2 binding is the causal mechanism for all variants unconfirmed","Downstream translational targets affected in neural progenitors unidentified"]},{"year":2022,"claim":"Showed acetylation of Pab1 at K131 by reducing poly(A) binding suppresses stress-granule formation, with Rpd3 as the deacetylase, adding acetylation as a stress-responsive switch.","evidence":"Acetylation-mimetic mutants, stress-granule imaging, EMSA, and rpd3 genetic epistasis in yeast","pmids":["36572187"],"confidence":"Medium","gaps":["Acetyltransferase responsible not identified","Human PABPC1 K131 acetylation not tested"]},{"year":2023,"claim":"Demonstrated USP10 deubiquitinates K27/K29 chains on PABPC1 RRM2 to enhance coupling of specific mRNAs to eIF4G1, providing a tumor-promoting translational control mechanism.","evidence":"Co-IP, deubiquitination and linkage-specific assays, RRM2 mutants, and xenograft models in PDAC","pmids":["37757903"],"confidence":"Medium","gaps":["Counterbalancing E3 ligase for these chains not defined here","Selectivity for CLK2 mRNA mechanistically unexplained"]},{"year":2024,"claim":"Revealed a nuclear function in which PABPC1, with TPR, retains A-rich circRNAs in the nucleus, and its downregulation during differentiation permits circRNA export required for neurite outgrowth.","evidence":"Nuclear/cytoplasmic fractionation, PABPC1 manipulation, circRNA A-rich motif mutagenesis, neurite assays, and TPR Co-IP","pmids":["38838666"],"confidence":"Medium","gaps":["How PABPC1 distinguishes circRNA from linear poly(A) substrates unclear","Generality beyond stem-cell/neuronal context untested"]},{"year":2024,"claim":"Implicated PABPC1 in degradation of pathogenic C9orf72 GGGGCC repeat RNA via interactions with hnRNPA3 and the RNA exosome, linking it to repeat-expansion disease surveillance.","evidence":"APEX2 proximity biotinylation, proximity ligation, and PABPC1-knockdown repeat-RNA accumulation assays","pmids":["38444607"],"confidence":"Medium","gaps":["Direct exosome recruitment vs. indirect effect not separated","Proximity-based evidence lacks reconstitution"]},{"year":2025,"claim":"Identified PABPC1 condensate formation as a driver of leukaemogenic mRNA translation in CML blast crisis, nominating it as a therapeutic target that overcomes TKI resistance.","evidence":"Genome-scale CRISPR screen, condensate imaging, polysome profiling, translation-efficiency analysis, and pharmacological inhibition in CML models","pmids":["40102686"],"confidence":"High","gaps":["Determinants of condensate selectivity for structured 5' UTR mRNAs not defined","How condensation alters initiation kinetics mechanistically unresolved"]},{"year":2025,"claim":"Showed stress-induced SUMOylation of PABPC1 drives stress-granule assembly via a TIA1 complex that selectively stabilizes U-rich mRNAs and supports mitophagy gene expression.","evidence":"SUMOylation assays, stress-granule imaging, transcriptome-wide stability analysis, TIA1 Co-IP, and mitophagy readouts","pmids":["40774970"],"confidence":"High","gaps":["SUMO sites and responsible E3 ligase not fully mapped","How SUMO-PABPC1 selects U-rich elements mechanistically unclear"]},{"year":2025,"claim":"Used acute Pab1 depletion to show its primary in vivo role is blocking decapping/decay, with closed-loop eIF4G contact dispensable for most yeast translation, reframing the canonical scaffolding model.","evidence":"Auxin-inducible degron depletion, RNA-Seq, Ribo-Seq, dcp2Δ epistasis, and polysome profiling in yeast","pmids":["40071937"],"confidence":"High","gaps":["Whether the same hierarchy holds in metazoan PABPC1 untested","Transcript subsets that do require closed-loop initiation not fully enumerated"]},{"year":null,"claim":"It remains unresolved how the array of PABPC1 post-translational modifications, conformational states, and partner interactions are integrated to determine, on a given mRNA, whether PABPC1 promotes translation, licenses deadenylation, or drives condensate/stress-granule sequestration.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking modification state to functional output","Quantitative rules governing partner competition on a single mRNP unknown","Crosstalk between nuclear and cytoplasmic functions undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[9,10,26,28,31]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[6,10,25,27,32]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,3,7,20,21]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,20,27]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[14,31]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5,31]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[1,2,4,7,20]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[6,8,18,25,27]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[26,28]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[19,22,25,29]}],"complexes":["stress granule","CCR4-NOT (associated)"],"partners":["EIF4G1","ERF3","TNRC6A","BTG2","PAIP2","LARP1","TIA1","AGO2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P11940","full_name":"Polyadenylate-binding protein 1","aliases":[],"length_aa":636,"mass_kda":70.7,"function":"Binds the poly(A) tail of mRNA, including that of its own transcript, and regulates processes of mRNA metabolism such as pre-mRNA splicing and mRNA stability (PubMed:11051545, PubMed:17212783, PubMed:25480299). Its function in translational initiation regulation can either be enhanced by PAIP1 or repressed by PAIP2 (PubMed:11051545, PubMed:20573744). Can probably bind to cytoplasmic RNA sequences other than poly(A) in vivo. Binds to N6-methyladenosine (m6A)-containing mRNAs and contributes to MYC stability by binding to m6A-containing MYC mRNAs (PubMed:32245947). Involved in translationally coupled mRNA turnover (PubMed:11051545). Implicated with other RNA-binding proteins in the cytoplasmic deadenylation/translational and decay interplay of the FOS mRNA mediated by the major coding-region determinant of instability (mCRD) domain (PubMed:11051545). Involved in regulation of nonsense-mediated decay (NMD) of mRNAs containing premature stop codons; for the recognition of premature termination codons (PTC) and initiation of NMD a competitive interaction between UPF1 and PABPC1 with the ribosome-bound release factors is proposed (PubMed:18447585). By binding to long poly(A) tails, may protect them from uridylation by ZCCHC6/ZCCHC11 and hence contribute to mRNA stability (PubMed:25480299) (Microbial infection) Positively regulates the replication of dengue virus (DENV)","subcellular_location":"Cytoplasm; Cytoplasm, Stress granule; Nucleus; Cell projection, lamellipodium","url":"https://www.uniprot.org/uniprotkb/P11940/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/PABPC1","classification":"Common Essential","n_dependent_lines":1109,"n_total_lines":1208,"dependency_fraction":0.918046357615894},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ENY2","stoichiometry":10.0},{"gene":"ATG13","stoichiometry":0.2},{"gene":"ATG4B","stoichiometry":0.2},{"gene":"EMC9","stoichiometry":0.2},{"gene":"NCAPH","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PABPC1","total_profiled":1310},"omim":[{"mim_id":"621297","title":"LYMPHATIC ENDOTHELIAL TRANSCRIPTIONAL REGULATOR lncRNA 1; LETR1","url":"https://www.omim.org/entry/621297"},{"mim_id":"621055","title":"POLYADENYLATE-BINDING PROTEIN, CYTOPLASMIC, 1-LIKE; PABPC1L","url":"https://www.omim.org/entry/621055"},{"mim_id":"618657","title":"La RIBONUCLEOPROTEIN 4; LARP4","url":"https://www.omim.org/entry/618657"},{"mim_id":"618206","title":"ZINC FINGER CCCH DOMAIN-CONTAINING PROTEIN 7B; ZC3H7B","url":"https://www.omim.org/entry/618206"},{"mim_id":"617448","title":"PABP-DEPENDENT POLY(A) NUCLEASE 3; PAN3","url":"https://www.omim.org/entry/617448"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"salivary gland","ntpm":1212.8}],"url":"https://www.proteinatlas.org/search/PABPC1"},"hgnc":{"alias_symbol":["PABP1","PABPL1"],"prev_symbol":["PAB1","PABPC2"]},"alphafold":{"accession":"P11940","domains":[{"cath_id":"3.30.70.330","chopping":"11-183","consensus_level":"medium","plddt":93.0506,"start":11,"end":183},{"cath_id":"3.30.70.330","chopping":"189-266","consensus_level":"high","plddt":92.794,"start":189,"end":266},{"cath_id":"3.30.70.330","chopping":"292-373","consensus_level":"high","plddt":94.3507,"start":292,"end":373},{"cath_id":"1.10.1900.10","chopping":"553-627","consensus_level":"high","plddt":87.1763,"start":553,"end":627}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P11940","model_url":"https://alphafold.ebi.ac.uk/files/AF-P11940-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P11940-F1-predicted_aligned_error_v6.png","plddt_mean":77.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PABPC1","jax_strain_url":"https://www.jax.org/strain/search?query=PABPC1"},"sequence":{"accession":"P11940","fasta_url":"https://rest.uniprot.org/uniprotkb/P11940.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P11940/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P11940"}},"corpus_meta":[{"pmid":"17318186","id":"PMC_17318186","title":"A conserved role for cytoplasmic poly(A)-binding protein 1 (PABPC1) in nonsense-mediated mRNA decay.","date":"2007","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/17318186","citation_count":185,"is_preprint":false},{"pmid":"19797087","id":"PMC_19797087","title":"The silencing domain of GW182 interacts with PABPC1 to promote translational repression and degradation of microRNA targets and is required for target release.","date":"2009","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19797087","citation_count":137,"is_preprint":false},{"pmid":"9199303","id":"PMC_9199303","title":"Yeast Pab1 interacts with Rna15 and participates in the control of the poly(A) tail length in vitro.","date":"1997","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/9199303","citation_count":118,"is_preprint":false},{"pmid":"20368989","id":"PMC_20368989","title":"Localization to, and effects of Pbp1, Pbp4, Lsm12, Dhh1, and Pab1 on stress granules in Saccharomyces cerevisiae.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20368989","citation_count":110,"is_preprint":false},{"pmid":"15769879","id":"PMC_15769879","title":"Yeast poly(A)-binding protein Pab1 shuttles between the nucleus and the cytoplasm and functions in mRNA export.","date":"2005","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/15769879","citation_count":109,"is_preprint":false},{"pmid":"36436682","id":"PMC_36436682","title":"CircPTK2/PABPC1/SETDB1 axis promotes EMT-mediated tumor metastasis and gemcitabine resistance in bladder cancer.","date":"2022","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/36436682","citation_count":102,"is_preprint":false},{"pmid":"30063126","id":"PMC_30063126","title":"Long non-coding RNA SNHG14 induces trastuzumab resistance of breast cancer via regulating PABPC1 expression through H3K27 acetylation.","date":"2018","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30063126","citation_count":94,"is_preprint":false},{"pmid":"15630021","id":"PMC_15630021","title":"Yeast poly(A)-binding protein, Pab1, and PAN, a poly(A) nuclease complex recruited by Pab1, connect mRNA biogenesis to export.","date":"2005","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/15630021","citation_count":92,"is_preprint":false},{"pmid":"21989405","id":"PMC_21989405","title":"Interaction of PABPC1 with the translation initiation complex is critical to the NMD resistance of AUG-proximal nonsense mutations.","date":"2011","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/21989405","citation_count":86,"is_preprint":false},{"pmid":"21063388","id":"PMC_21063388","title":"Two PABPC1-binding sites in GW182 proteins promote miRNA-mediated gene silencing.","date":"2010","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/21063388","citation_count":83,"is_preprint":false},{"pmid":"35346324","id":"PMC_35346324","title":"PABPC1-induced stabilization of IFI27 mRNA promotes angiogenesis and malignant progression in esophageal squamous cell carcinoma through exosomal miRNA-21-5p.","date":"2022","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/35346324","citation_count":80,"is_preprint":false},{"pmid":"22956915","id":"PMC_22956915","title":"ATXN2-CAG42 sequesters PABPC1 into insolubility and induces FBXW8 in cerebellum of old ataxic knock-in mice.","date":"2012","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22956915","citation_count":76,"is_preprint":false},{"pmid":"20379206","id":"PMC_20379206","title":"Role of GW182 proteins and PABPC1 in the miRNA pathway: a sense of déjà vu.","date":"2010","source":"Nature reviews. Molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20379206","citation_count":74,"is_preprint":false},{"pmid":"28653618","id":"PMC_28653618","title":"Poly(A) tail length regulates PABPC1 expression to tune translation in the heart.","date":"2017","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/28653618","citation_count":74,"is_preprint":false},{"pmid":"26912148","id":"PMC_26912148","title":"BTG2 bridges PABPC1 RNA-binding domains and CAF1 deadenylase to control cell proliferation.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/26912148","citation_count":69,"is_preprint":false},{"pmid":"22043172","id":"PMC_22043172","title":"Stability of a long noncoding viral RNA depends on a 9-nt core element at the RNA 5' end to interact with viral ORF57 and cellular PABPC1.","date":"2011","source":"International journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/22043172","citation_count":64,"is_preprint":false},{"pmid":"30655779","id":"PMC_30655779","title":"circRNA of AR-suppressed PABPC1 91 bp enhances the cytotoxicity of natural killer cells against hepatocellular carcinoma via upregulating UL16 binding protein 1.","date":"2018","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/30655779","citation_count":63,"is_preprint":false},{"pmid":"11279042","id":"PMC_11279042","title":"The yeast hsp70 homologue Ssa is required for translation and interacts with Sis1 and Pab1 on translating ribosomes.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11279042","citation_count":61,"is_preprint":false},{"pmid":"32015336","id":"PMC_32015336","title":"PABPC1-induced stabilization of BDNF-AS inhibits malignant progression of glioblastoma cells through STAU1-mediated decay.","date":"2020","source":"Cell death & 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Depletion of PABPC1 also suppresses NMD independently of translation efficiency effects, indicating PABPC1 has a direct role in mRNA surveillance beyond positional information.\",\n      \"method\": \"PABPC1 tethering assays, 3' UTR length manipulation, PABPC1 depletion in Drosophila melanogaster cells\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal experimental approaches (tethering, depletion, UTR manipulation) in a focused study, replicated across conditions\",\n      \"pmids\": [\"17318186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The GW182 silencing domain competes with eIF4G for binding to PABPC1; the GW182–PABPC1 interaction is required for miRNA target deadenylation and translational repression. PABPC1 overexpression suppresses miRNA-mediated silencing. PABPC1 also associates with components of the CCR4-NOT deadenylase complex.\",\n      \"method\": \"Co-immunoprecipitation, tethering assays, overexpression rescue experiments, interaction domain mapping in Drosophila and human cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, functional competition assays, overexpression rescue, multiple orthogonal methods in one study\",\n      \"pmids\": [\"19797087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Yeast Pab1 interacts with Rna15, a component of cleavage and polyadenylation factor CF I, and copurifies with CF I. Pab1 participates in controlling poly(A) tail length during polyadenylation in vitro: immunoneutralization or thermosensitive pab1 mutant extracts produce longer poly(A) tails, which are restored by adding recombinant Pab1.\",\n      \"method\": \"Two-hybrid assay, co-immunoprecipitation, anion-exchange chromatography co-purification, in vitro polyadenylation assay with mutant extracts and recombinant protein add-back\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro reconstitution with add-back, multiple orthogonal methods (two-hybrid, Co-IP, co-purification, in vitro assay)\",\n      \"pmids\": [\"9199303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Two distinct regions of GW182 proteins interact with PABPC1: one contains a PAM2 motif (binding the PABPC1 MLLE/C-terminal domain) and the second contains M2 and C-terminal sequences mediating indirect binding to the PABPC1 N-terminal domain. A single amino acid substitution in the TNRC6A-C PAM2 motif abolishes the interaction with PABPC1 and impairs GW182 silencing activity.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, point mutagenesis, silencing activity assays in Drosophila and human cells\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — point mutagenesis combined with functional silencing assays and Co-IP, multiple species and cell systems\",\n      \"pmids\": [\"21063388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Yeast Pab1 self-association (oligomerization and circularization) via its proline-rich region and RRM1 domains is required for CCR4 deadenylation in vivo. Self-associated PAB1 multimers and circular PAB1 species are unable to bind poly(A), and removal of RRM3 (which promoted oligomerization) accelerates CCR4 deadenylation, supporting a model where PAB1 self-association removes it from the poly(A) tail to permit deadenylation.\",\n      \"method\": \"Deletion mutagenesis of PAB1 domains, in vivo deadenylation assays, protein-protein interaction assays, analytical ultracentrifugation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple domain deletion mutants with in vivo deadenylation readouts plus biophysical characterization of PAB1 conformational states\",\n      \"pmids\": [\"17620415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Yeast Pab1 shuttles between nucleus and cytoplasm, functioning as export cargo of Xpo1/Crm1 via RanGTP-dependent interaction, and can also exit via the MEX67 mRNA export pathway. Import is mediated by Kap108/Sxm1 through a nuclear localization signal in Pab1's fourth RRM domain. Inhibition of Pab1 nuclear import causes a kinetic delay in mRNA export, and pab1Δ lethality is suppressed by deletion of the nuclear exosome subunit RRP6.\",\n      \"method\": \"Nuclear export inhibition (LMB treatment), subcellular fractionation, direct binding assay with Xpo1/Crm1, genetic epistasis (rrp6 suppressor), import receptor identification\",\n      \"journal\": \"RNA\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding to export receptor, functional nuclear import/export experiments, genetic suppressor analysis, multiple orthogonal approaches\",\n      \"pmids\": [\"15769879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PABPC1 interactions with the cap-binding complex subunit eIF4G and the 40S recruitment factor eIF3, as well as the ribosome release factor eRF3, underlie critical 3'–5' linkage of translation initiation with efficient termination at AUG-proximal PTCs, providing NMD resistance. Translation termination at AUG-proximal PTCs lacks ribosome stalling seen at NMD-sensitive PTCs.\",\n      \"method\": \"Co-immunoprecipitation of PABPC1 with eIF4G, eIF3, and eRF3; ribosome stalling assays; NMD reporter assays in human cells\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with multiple translation factors, functional ribosome stalling and NMD reporter assays in single lab\",\n      \"pmids\": [\"21989405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The APRO domain of BTG2 interacts directly with the first RRM domain of PABPC1. The PABPC1 RRM1 and BTG2 APRO domains together are sufficient to stimulate CAF1 deadenylase activity in vitro without other CCR4-NOT subunits. BTG2's interaction with PABPC1 RRM1 is required for BTG2 to control cell proliferation.\",\n      \"method\": \"In vitro deadenylase activity assay with purified proteins, domain mapping, cell proliferation assay with interaction-deficient mutants\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of deadenylase stimulation with purified components, functional mutagenesis, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"26912148\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MKRN3 E3 ligase ubiquitinates PABPC1 (identified by mass spectrometry proteomics screen as major substrate). MKRN3 missense mutations found in patients substantially compromise MKRN3-mediated PABPC1 ubiquitination. MKRN3 modulates cell proliferation through nonproteolytic PABPC1 ubiquitination, which in turn regulates PABPC1-mediated global protein synthesis.\",\n      \"method\": \"Mass spectrometry substrate screen, in vitro ubiquitination assay, patient mutation analysis, cell proliferation assays, MKRN3 knockout mouse models\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — MS-based substrate identification, in vitro ubiquitination assay, patient mutation functional validation, in vivo mouse models\",\n      \"pmids\": [\"34143182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Paip2A competitively binds to the RRM2–RRM3 regions of PABPC1 at the same interface as poly(A), with higher affinity for RRM2 and RRM3 individually than poly(A). Paip2A initially binds RRM2 of poly(A)-bound PABPC1, then displaces RRM3 from poly(A), causing dissociation of the whole PABPC1 molecule and thereby repressing poly(A)-dependent translation.\",\n      \"method\": \"Isothermal titration calorimetry (ITC), NMR chemical shift perturbation analysis, competition binding experiments with isolated RRM domains\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ITC and NMR with purified proteins, mechanistic model supported by multiple binding measurements, single lab\",\n      \"pmids\": [\"35307347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Targeting cytosolic PABPC1 to mitochondria (as mtPABP1) coats the mitochondrial poly(A) tail but does not cause transcript decay; instead, it causes marked inhibition of mitochondrial translation, demonstrating that poly(A) tail-binding by PABPC1 is functionally important for translation and that endogenous poly(A)-binding factors interact with the mt-mRNA poly(A) tail to optimize mitochondrial protein synthesis.\",\n      \"method\": \"Mitochondrial targeting sequence fusion constructs, steady-state mt-mRNA level measurement, mitochondrial translation assay in mammalian cells\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence (translation inhibition), single lab, two readouts (transcript levels and translation)\",\n      \"pmids\": [\"20144953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Phosphorylation at serine/threonine residues in intrinsically disordered regions flanking PAM2 motifs of PAM2-containing proteins (Tob2, Pan3, Tnrc6c) regulates their interactions with PABPC1; phosphomimetic mutations in these proteins reduce binding to PABPC1 and impair their functions in mRNA turnover and gene silencing.\",\n      \"method\": \"Phosphorylation state manipulation (kinase activation, phosphatase inhibition), phospho-blocking and phosphomimetic mutants, Co-immunoprecipitation, mRNA stability and gene silencing reporter assays\",\n      \"journal\": \"RNA\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphomimetic mutagenesis with functional assays, multiple PAM2-containing proteins tested, single lab\",\n      \"pmids\": [\"23340509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PABPC1 directly interacts with hnRNPLL in T cells and plasma cells. Although PABPC1 is not required for alternative splicing of CD45, it promotes hnRNPLL binding to immunoglobulin mRNA and regulates switching from membrane to secreted IgH isoform through mRNA alternative polyadenylation.\",\n      \"method\": \"Co-immunoprecipitation, RNA immunoprecipitation, functional switching assays in plasma cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP and RIP with functional immunoglobulin switching assay, single lab\",\n      \"pmids\": [\"28611064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Regulated changes in poly(A) tail length dynamically control PABPC1 protein synthesis in cardiomyocytes, titrating cellular translation capacity in response to developmental and hypertrophic cues. PABPC1 is identified as a direct regulator of cardiac hypertrophy.\",\n      \"method\": \"Poly(A) tail length measurements, PABPC1 knockdown and overexpression in cardiomyocytes, cardiac hypertrophy models in vivo and in vitro\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct poly(A) tail length manipulation with translational readout, loss- and gain-of-function in primary cells, single lab\",\n      \"pmids\": [\"28653618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PABPC1 interacts with AGO2 in the cytoplasm of HCC cells; this interaction increases recruitment of mRNA to RISC and enhances miRNA-mediated inhibition efficiency.\",\n      \"method\": \"Anti-AGO2 co-immunoprecipitation and mass spectrometry, cytoplasmic fractionation, functional miRNA reporter assays\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP with MS identification, functional RISC recruitment assay, single lab\",\n      \"pmids\": [\"26188282\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"LARP1 requires PABPC1 for association with its specific mRNA targets: the mRNA interactome of LARP1 and PABPC1 show high overlap, and PABPC1 depletion reduces LARP1 binding to its mRNA targets including TOP-containing mRNAs. mRNAs bound by both LARP1 and PABPC1 are in a translationally repressed state.\",\n      \"method\": \"RNA-binding protein capture (mRNA interactome), PABPC1 knockdown effect on LARP1 mRNA binding, polysome profiling\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RBP capture with functional epistasis (PABPC1 KD abrogates LARP1 mRNA association), single lab\",\n      \"pmids\": [\"33332560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The isolated La-module of LARP1 mediates poly(A) length protection and mRNA stabilization in a manner dependent on its PAM2 motif binding to PABPC1. A point mutation in the PAM2 motif impairs mRNA stabilization and PABP binding in vivo without affecting oligo(A) RNA binding by the purified recombinant La-module in vitro.\",\n      \"method\": \"PAM2 point mutagenesis, mRNA stability assays in HEK293 cells, in vitro RNA binding assay with recombinant protein, Co-immunoprecipitation\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — mutagenesis with in vitro binding and in vivo functional assay, single lab\",\n      \"pmids\": [\"33292040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The viral protease SVV 3Cpro cleaves PABPC1 at residue 437, generating N-terminal (50 kDa) and C-terminal (25 kDa) fragments. PABPC1 inhibits SVV replication, and 3Cpro cleavage of PABPC1 (dependent on active site residues H48 and C160 of 3Cpro) decreases host protein synthesis rates.\",\n      \"method\": \"Viral infection and protease expression, point mutagenesis of 3Cpro active site, cleavage site mapping, protein synthesis rate measurement\",\n      \"journal\": \"Pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — active site mutagenesis of protease with cleavage site mapping, functional translation assay, single lab\",\n      \"pmids\": [\"32512928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"USP10 deubiquitinase directly interacts with PABPC1 and removes K27/K29-linked ubiquitin from the RRM2 domain of PABPC1. Deubiquitinated PABPC1 more efficiently couples CLK2 mRNA with eIF4G1, increasing CLK2 translation efficiency and promoting PDAC tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, deubiquitination assay, linkage-specific ubiquitination analysis, mRNA-protein interaction assay, RRM2 domain mutants, xenograft models\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and deubiquitination assay with domain mapping, functional translation assay, mutant rescue, single lab\",\n      \"pmids\": [\"37757903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"De novo variants in the PABP domain of PABPC1 cluster causing developmental delay weaken the interaction between PABPC1 and PAIP2 (confirmed by co-immunoprecipitation). Pabpc1 knockdown in mouse embryo brain decreases neural progenitor cell proliferation; wild-type Pabpc1 rescues this defect, whereas three of four patient variants do not.\",\n      \"method\": \"Exome sequencing, co-immunoprecipitation, in silico modeling, in utero electroporation with rescue experiments\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP interaction validation plus in vivo neural proliferation assay with rescue, single study\",\n      \"pmids\": [\"35511136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A conserved boxC motif in BTG1 and BTG2 APRO domains is necessary and sufficient for interaction with PABPC1 RRM1, and is required (but not for PRMT1 binding) for stimulation of deadenylation both in cellulo and in vitro.\",\n      \"method\": \"NMR chemical shift perturbation, mutagenesis, pulldown assays, in vitro and in cellulo deadenylation assays\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural analysis with mutagenesis and in vitro deadenylation reconstitution, single lab with orthogonal biochemical and functional methods\",\n      \"pmids\": [\"34060423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structure of the PAM2w variant motif of LARP4B bound to the MLLE domain of PABPC1 was solved, uncovering a new mode of interaction between PAM2 motifs and MLLE domains. Mutational studies in vitro and in vivo validated the structural findings.\",\n      \"method\": \"X-ray crystallography, in vitro binding mutagenesis, in vivo functional assays\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with mutational validation in vitro and in vivo, single lab\",\n      \"pmids\": [\"32517187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Expanded ATXN2 (CAG42) sequesters PABPC1 into insolubility in cerebellum of knock-in mice, with decreasing soluble PABPC1 levels correlating with progressive ATXN2 insolubility. This sequestration of PABPC1 into insolubility by expanded ATXN2 was validated in human cell culture.\",\n      \"method\": \"Knock-in mouse model, protein fractionation (soluble vs. insoluble), immunoblot, human cell culture overexpression\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knock-in model plus cell culture validation, multiple tissues analyzed, single lab\",\n      \"pmids\": [\"22956915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Yeast Ssa (hsp70) physically interacts with both Sis1 (hsp40) and Pab1 (poly(A)-binding protein) preferentially on translating ribosomes; this interaction is mediated by the variable C-terminal domain of Ssa. Depletion of Ssa dramatically reduces the interaction of Pab1 with the translation initiation factor eIF4G, suggesting Ssa is required for proper Pab1-eIF4G interaction.\",\n      \"method\": \"Subcellular fractionation, co-immunoprecipitation on polysomes, domain mapping, Ssa depletion followed by Pab1-eIF4G interaction assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP on polysomes with domain mapping, depletion experiment showing downstream effect on Pab1-eIF4G interaction, single lab\",\n      \"pmids\": [\"11279042\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In yeast, the Pab1–eRF3 interaction negatively regulates translation termination (deletion of interacting domains produces antisuppression phenotype / decreased readthrough); the Pab1 C-terminal domain role in mRNA stability is independent of eRF3. Yeast eRF3 does not contain a consensus PAM2 motif, indicating a different mode of interaction from metazoan Pab1-eRF3.\",\n      \"method\": \"Domain deletion analysis, genetic interaction (double deletion), readthrough assays, mRNA stability assays in yeast\",\n      \"journal\": \"RNA\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with double domain deletions, translation termination functional assay, single lab\",\n      \"pmids\": [\"25411355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PABPC1 preferentially enhances translation efficiency of leukaemogenic mRNAs with long, highly structured 5' UTRs by forming biomolecular condensates/phase separation in CML blast crisis cells. CRISPR-Cas9 screening identified PABPC1 as a driver of CML blast crisis progression, and genetic or pharmacological inhibition of PABPC1 suppresses CML cell proliferation and overcomes TKI resistance with minimal effects on normal haematopoiesis.\",\n      \"method\": \"CRISPR-Cas9 high-throughput screen, biomolecular condensate imaging, polysome profiling, translational efficiency analysis, pharmacological inhibition in murine and human CML models\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-scale functional screen validated with multiple orthogonal mechanistic experiments (phase separation, translation efficiency assays, in vivo mouse models), multiple approaches\",\n      \"pmids\": [\"40102686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SUMOylation of PABPC1 under stress conditions promotes stress granule assembly and selectively stabilizes mRNAs enriched in conserved U-rich elements. SUMOylated PABPC1 interacts with TIA1 to form a PABPC1-SUMO-TIA1 complex that recruits U-rich mRNAs into stress granules, protecting them from degradation and facilitating expression of mitophagy-related genes (FUNDC1, BNIP3L).\",\n      \"method\": \"SUMOylation assay, stress granule imaging, transcriptome-wide mRNA stability analysis, co-immunoprecipitation of SUMOylated PABPC1 with TIA1, mitophagy assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SUMOylation biochemistry, transcriptome-wide analysis, Co-IP with TIA1, functional mitophagy readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"40774970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Yeast Pab1 primarily controls translation initiation in vivo by blocking mRNA decapping and decay: auxin-induced Pab1 degradation reduces mRNA and polysome abundance, and this effect is suppressed by deletion of the decapping enzyme catalytic subunit Dcp2. Assembly of the closed-loop mRNP via PABP–eIF4G interaction is dispensable for wild-type translation of most yeast transcripts at normal mRNA levels.\",\n      \"method\": \"Auxin-inducible degron system for Pab1 depletion, RNA-Seq, Ribo-Seq, dcp2Δ epistasis, polysome profiling\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — auxin-induced depletion with genetic epistasis (dcp2Δ suppressor), transcriptome-wide and ribosome profiling, peer-reviewed and preprint versions concordant\",\n      \"pmids\": [\"40071937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Acetylation of Pab1 at lysine 131 (K131) reduces stress granule formation upon glucose deprivation and other stressors. Rpd3 deacetylase is the primary enzyme responsible for deacetylation of Pab1-K131. Acetylation mimic at K131 negatively impacts poly(A) RNA binding by Pab1.\",\n      \"method\": \"Acetylation mimetic mutants, stress granule imaging, EMSA (electromobility shift assay) for poly(A) binding, genetic epistasis with rpd3 mutant\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — acetylation mimetic mutagenesis with functional stress granule and RNA binding assays, genetic deacetylase identification, single lab\",\n      \"pmids\": [\"36572187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PABPC1 interacts with hnRNPA3 and the RNA exosome complex, and knockdown of PABPC1 increases accumulation of C9orf72 GGGGCC repeat RNA and RNA foci to the same extent as hnRNPA3 knockdown. Proximity ligation assays show PABPC1-hnRNPA3 and PABPC1-RNA exosome co-localize preferentially when repeat RNA is present, supporting PABPC1 as a mediator of polyadenylated GGGGCC repeat RNA degradation.\",\n      \"method\": \"APEX2-mediated proximity biotinylation, proximity ligation assay, PABPC1 knockdown with repeat RNA accumulation readout\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — proximity biotinylation and ligation assays with functional knockdown, single lab\",\n      \"pmids\": [\"38444607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"EV-D68 3Cpro cleaves PABPC1 to redirect host translation machinery toward viral RNA. Overexpression of PABPC1 inhibits EV-D68 replication and reduces virus-mediated suppression of host translation. This mechanism is conserved in EV-A71 and CV-A16.\",\n      \"method\": \"Viral protease expression, overexpression rescue assay for viral replication and host translation, comparison across multiple enterovirus species\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — protease cleavage with functional translation and replication assays, multi-enterovirus validation, single lab\",\n      \"pmids\": [\"40294010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PABPC1 is required for the nuclear retention of newly produced adenosine-rich circRNAs in H9 stem cells: nuclear PABPC1 binds A-rich circRNAs and, in complex with nuclear basket protein TPR, prevents their cytoplasmic export. Decreased nuclear PABPC1 upon neuronal differentiation enables export of A-rich circRNAs (including circRTN4(2,3)) to the cytoplasm, which is required for neurite outgrowth.\",\n      \"method\": \"Nuclear/cytoplasmic fractionation, PABPC1 manipulation (overexpression/knockdown), A-rich motif mutagenesis in circRNAs, neurite outgrowth assay, co-immunoprecipitation with TPR\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence (neurite outgrowth), circRNA motif mutagenesis, Co-IP with nuclear basket protein, single lab\",\n      \"pmids\": [\"38838666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PIWIL1 interacts with PABPC1 through its N- and C-terminal domains in an RNA-dependent manner, and binds 3'-UTRs of post-meiotic mRNAs via its N-terminal domain. PIWIL1 augments protein translation together with PABPC1 in the presence of 3'-UTRs of spermiogenic mRNAs, as shown by luciferase reporter assay and polysome profiling.\",\n      \"method\": \"Co-immunoprecipitation domain mapping, luciferase reporter translation assay, sucrose gradient sedimentation (polysome profiling), heterologous cell system\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain-level Co-IP plus functional translation assay with polysome profiling, single lab\",\n      \"pmids\": [\"29701755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In yeast, neither the poly(A) tail nor Pab1p is required for NMD: mRNAs lacking poly(A) tails containing a PTC are still NMD substrates, and cells lacking Pab1p retain NMD substrate recognition and destabilization activity. This establishes that the poly(A)/Pab1 model for NMD substrate discrimination does not apply in yeast.\",\n      \"method\": \"Poly(A)-tail removal constructs, pab1Δ genetic analysis, NMD reporter assays in yeast\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic null mutant (pab1Δ) combined with engineered poly(A)-less mRNAs and NMD reporters, two independent experimental approaches establishing a negative result of broad mechanistic significance\",\n      \"pmids\": [\"18206975\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PABPC1 is a multifunctional cytoplasmic RNA-binding protein that binds poly(A) tails via its RRM domains and acts as a scaffold for translation initiation (interacting with eIF4G, eIF3, and eRF3 to promote closed-loop mRNP formation and efficient termination), mRNA stabilization (protecting mRNAs from deadenylation and decapping), and mRNA decay (recruiting CCR4-NOT deadenylase complex via GW182 proteins and BTG/Tob factors); its C-terminal MLLE domain interacts with PAM2-containing proteins (GW182, LARP1, LARP4B, Tob2, Pan3) to regulate mRNA stability, while post-translational modifications including nonproteolytic ubiquitination by MKRN3, deubiquitination by USP10, SUMOylation, and acetylation dynamically tune its activity in translation regulation, stress granule assembly, and selective mRNA stabilization; it also shuttles between nucleus and cytoplasm to participate in mRNA export and quality control, and its position relative to stop codons is a key determinant for NMD suppression in higher eukaryotes.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PABPC1 is the principal cytoplasmic poly(A)-binding protein, coating mRNA poly(A) tails through its tandem RRM domains and acting as a central hub that couples poly(A) status to translation, mRNA stability, and surveillance [#9, #10]. It uses its modular architecture for combinatorial control: the RRM domains engage the poly(A) tail and competing regulators—Paip2A binds the RRM2–RRM3 interface to displace PABPC1 and repress poly(A)-dependent translation [#9], while the APRO/boxC domains of BTG1/BTG2 dock on RRM1 to stimulate CAF1/CCR4-NOT deadenylase activity [#7, #20]. Its C-terminal MLLE domain recognizes PAM2 motifs in a family of effectors, including GW182/TNRC6, LARP1, LARP4B, Tob2, and Pan3, and these PAM2 contacts are tuned by phosphorylation of the flanking disordered regions [#3, #11, #16, #21]. Through GW182 and association with the CCR4-NOT complex, PABPC1 enables miRNA-directed deadenylation and silencing, and it cooperates with AGO2 to enhance RISC recruitment [#1, #3, #14], whereas its interactions with eIF4G, eIF3, and the release factor eRF3 link initiation to efficient termination and form the basis of its role in NMD: PABPC1 position relative to the stop codon is a key determinant of premature-termination-codon definition in higher eukaryotes [#1, #6, #0]. A layer of post-translational modification dynamically gates these activities—nonproteolytic ubiquitination by the E3 ligase MKRN3 regulates global protein synthesis and proliferation, USP10-mediated deubiquitination of RRM2 selectively boosts translation of target mRNAs, and stress-induced SUMOylation drives stress-granule assembly via a TIA1 complex that stabilizes U-rich mRNAs [#8, #18, #26]. PABPC1 also shuttles between nucleus and cytoplasm, contributing to mRNA export and to nuclear retention of A-rich circRNAs, and serves as an antiviral target cleaved by enteroviral 3C proteases to shut down host translation [#5, #31, #17, #30]. De novo variants in its PABP domain that weaken the PABPC1–PAIP2 interaction cause a developmental-delay disorder and impair neural progenitor proliferation [#19].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established that the poly(A)-binding protein is not merely a passive tail coat but an active participant in 3'-end processing, linking it physically to the cleavage/polyadenylation machinery and to control of poly(A) tail length.\",\n      \"evidence\": \"Two-hybrid, Co-IP, co-purification with CF I component Rna15, and in vitro polyadenylation with pab1 mutant extracts plus recombinant add-back in yeast\",\n      \"pmids\": [\"9199303\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which RRM domains mediate the CF I interaction\", \"Yeast-based; relevance to metazoan PABPC1 not addressed in this study\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showed that the Pab1–eIF4G closed-loop contact required for translation is itself chaperone-dependent, placing Hsp70/Hsp40 upstream of PABP function on translating ribosomes.\",\n      \"evidence\": \"Polysome Co-IP, domain mapping, and Ssa depletion followed by Pab1–eIF4G interaction assay in yeast\",\n      \"pmids\": [\"11279042\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which Ssa promotes the interaction (folding vs. assembly) not defined\", \"Not tested in metazoan systems\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated that PABP is a nucleocytoplasmic shuttling protein with defined import and export receptors, connecting it to mRNA export rather than confining it to cytoplasmic translation.\",\n      \"evidence\": \"LMB export inhibition, fractionation, direct Xpo1/Crm1 binding, Kap108/Sxm1 import receptor mapping to RRM4, and rrp6 genetic suppression in yeast\",\n      \"pmids\": [\"15769879\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nuclear function distinct from export not delineated\", \"Human PABPC1 shuttling receptors not mapped here\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified PABPC1 position relative to the stop codon as a determinant of premature-termination-codon definition, giving the protein a direct role in mRNA surveillance/NMD.\",\n      \"evidence\": \"Tethering downstream of a PTC, 3'-UTR elongation, and PABPC1 depletion in Drosophila cells\",\n      \"pmids\": [\"17318186\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between PABPC1 position and the NMD machinery not fully defined\", \"Insect-cell findings\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Revealed that the poly(A)/Pab1 NMD model is not universal: in yeast neither poly(A) nor Pab1 is required for substrate recognition, sharpening the surveillance role as a higher-eukaryote feature.\",\n      \"evidence\": \"Poly(A)-less PTC reporters and pab1Δ NMD reporter assays in yeast\",\n      \"pmids\": [\"18206975\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not explain the basis of the metazoan-specific positional dependence\", \"Negative result; what substitutes for Pab1 in yeast NMD unaddressed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Mechanistically connected PABPC1 to miRNA silencing by showing GW182 competes with eIF4G for PABPC1 and that this contact is required for target deadenylation and repression.\",\n      \"evidence\": \"Reciprocal Co-IP, tethering, overexpression rescue, and CCR4-NOT association in Drosophila and human cells\",\n      \"pmids\": [\"19797087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map the precise GW182 surfaces (resolved later)\", \"Whether eIF4G displacement is sufficient for repression untested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined a bipartite GW182–PABPC1 interaction (PAM2/MLLE plus N-terminal contacts) and proved a single PAM2 residue controls silencing, establishing the MLLE–PAM2 module as functionally essential.\",\n      \"evidence\": \"Domain mapping, point mutagenesis, Co-IP, and silencing assays in Drosophila and human cells\",\n      \"pmids\": [\"21063388\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MLLE–PAM2 recognition not resolved here\", \"Relative contribution of each contact to deadenylation vs. repression unquantified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Proposed that PABP self-association/circularization removes it from the poly(A) tail to license CCR4 deadenylation, coupling PABP conformational state to mRNA turnover.\",\n      \"evidence\": \"Domain-deletion mutants, in vivo deadenylation, and analytical ultracentrifugation in yeast\",\n      \"pmids\": [\"17620415\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger for self-association in vivo unknown\", \"Yeast-specific; human PABPC1 oligomerization not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed by ectopic mitochondrial targeting that poly(A) coating by PABPC1 directly governs translation efficiency rather than transcript stability, isolating its translational function on a poly(A) tail.\",\n      \"evidence\": \"Mitochondrial targeting fusion (mtPABP1), steady-state mt-mRNA measurement, and mitochondrial translation assay in mammalian cells\",\n      \"pmids\": [\"20144953\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Artificial mitochondrial context\", \"Endogenous mitochondrial poly(A)-binding factor identity not established\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked PABPC1's translation-factor contacts (eIF4G, eIF3, eRF3) to NMD resistance at AUG-proximal PTCs, providing a molecular basis for how termination context determines surveillance.\",\n      \"evidence\": \"Reciprocal Co-IP, ribosome stalling assays, and NMD reporters in human cells\",\n      \"pmids\": [\"21989405\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal order of factor recruitment during termination not resolved\", \"Quantitative contribution of each contact unmeasured\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Connected PABPC1 to neurodegeneration by showing expanded ATXN2 sequesters it into insolubility, implicating loss of soluble PABPC1 in disease pathology.\",\n      \"evidence\": \"ATXN2 CAG42 knock-in mouse fractionation/immunoblot and human cell-culture validation\",\n      \"pmids\": [\"22956915\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of PABPC1 sequestration on translation not measured\", \"Causality vs. correlation in disease progression unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established phosphorylation of PAM2-flanking disordered regions as a switch tuning effector binding to PABPC1, adding a regulatory layer to MLLE-mediated interactions.\",\n      \"evidence\": \"Phosphomimetic/phospho-blocking mutants of Tob2, Pan3, Tnrc6c with Co-IP and mRNA stability/silencing reporters\",\n      \"pmids\": [\"23340509\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Responsible kinases not identified\", \"In vivo signaling contexts that trigger these phosphorylations unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Distinguished the yeast Pab1–eRF3 termination-regulatory function from its eRF3-independent mRNA-stability role, and showed the metazoan PAM2-based eRF3 contact differs mechanistically from yeast.\",\n      \"evidence\": \"Domain deletion, genetic epistasis, readthrough and mRNA stability assays in yeast\",\n      \"pmids\": [\"25411355\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Yeast eRF3 binding mode not structurally defined\", \"Direct extrapolation to human eRF3 limited\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Reconstituted minimal deadenylation stimulation, showing the BTG2 APRO domain plus PABPC1 RRM1 are sufficient to activate CAF1, and linked this contact to proliferation control.\",\n      \"evidence\": \"In vitro deadenylase assay with purified proteins, domain mapping, proliferation assays with interaction-deficient mutants\",\n      \"pmids\": [\"26912148\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How RRM1 engagement positions CAF1 on the tail not structurally resolved\", \"Role of full CCR4-NOT in the in vivo reaction not addressed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Implicated PABPC1 in immune cell mRNA processing by promoting hnRNPLL binding and IgH membrane-to-secreted isoform switching via alternative polyadenylation.\",\n      \"evidence\": \"Co-IP, RIP, and functional switching assays in plasma cells\",\n      \"pmids\": [\"28611064\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which PABPC1 favors a specific poly(A) site unclear\", \"Direct vs. indirect effect on hnRNPLL recruitment not separated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated that poly(A) tail-length control of PABPC1's own synthesis titrates cellular translation capacity, identifying it as a regulator of cardiac hypertrophy.\",\n      \"evidence\": \"Poly(A) tail measurements, PABPC1 knockdown/overexpression, and in vivo/in vitro hypertrophy models in cardiomyocytes\",\n      \"pmids\": [\"28653618\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream cues setting PABPC1 mRNA tail length not defined\", \"Whether this is tissue-specific unaddressed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed PABPC1 partners with PIWIL1 to augment translation of spermiogenic mRNAs, extending its translational-activator role to germ-cell post-meiotic gene expression.\",\n      \"evidence\": \"Domain-level Co-IP, luciferase reporter, and polysome profiling in a heterologous cell system\",\n      \"pmids\": [\"29701755\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous germ-cell validation limited\", \"RNA-dependence of the interaction not mechanistically dissected\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided the structural basis for MLLE–PAM2 recognition by solving the LARP4B PAM2w–MLLE crystal structure, revealing a new variant binding mode.\",\n      \"evidence\": \"X-ray crystallography with in vitro and in vivo mutational validation\",\n      \"pmids\": [\"32517187\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional output of LARP4B–PABPC1 binding not quantified here\", \"Generality across other PAM2 variants untested in this structure\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established that LARP1's La-module stabilizes mRNA and protects poly(A) length specifically through its PAM2–PABPC1 contact, separating the in vivo stabilization role from intrinsic RNA binding.\",\n      \"evidence\": \"PAM2 point mutagenesis, mRNA stability assays, in vitro RNA binding, and Co-IP in HEK293 cells\",\n      \"pmids\": [\"33292040\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of poly(A) protection (occlusion vs. deadenylase exclusion) not resolved\", \"Single cell system\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed PABPC1 is required for LARP1 to engage its mRNA targets, including TOP mRNAs, placing PABPC1 upstream of LARP1-mediated translational repression.\",\n      \"evidence\": \"mRNA interactome capture, PABPC1-knockdown effect on LARP1 binding, and polysome profiling\",\n      \"pmids\": [\"33332560\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PABPC1 directly handoffs mRNA to LARP1 or acts indirectly unresolved\", \"Effect on translation of specific targets not quantified per-transcript\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified PABPC1 as an antiviral factor cleaved by SVV 3C protease, showing host poly(A)-binding capacity is targeted to suppress host translation during infection.\",\n      \"evidence\": \"3Cpro active-site mutagenesis, cleavage-site mapping at residue 437, and protein synthesis rate measurement\",\n      \"pmids\": [\"32512928\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of each cleavage fragment not defined\", \"In vivo relevance to viral pathogenesis unaddressed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed PABPC1 enhances RISC function by interacting with AGO2 in the cytoplasm to increase mRNA recruitment, deepening its role in miRNA-mediated regulation in cancer cells.\",\n      \"evidence\": \"Anti-AGO2 Co-IP/MS, cytoplasmic fractionation, and miRNA reporter assays in HCC cells\",\n      \"pmids\": [\"26188282\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. RNA-bridged AGO2 contact not distinguished\", \"Single cancer cell context\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified MKRN3 as the E3 ligase that nonproteolytically ubiquitinates PABPC1 to regulate global protein synthesis and proliferation, with patient mutations impairing this activity.\",\n      \"evidence\": \"MS substrate screen, in vitro ubiquitination, patient mutation analysis, and MKRN3-knockout mouse models\",\n      \"pmids\": [\"34143182\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin linkage type and modified residues not fully mapped\", \"How nonproteolytic ubiquitin alters PABPC1 activity mechanistically unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined a conserved boxC motif in BTG1/BTG2 APRO domains as necessary and sufficient for PABPC1 RRM1 binding and deadenylation stimulation, refining the deadenylation-activation interface.\",\n      \"evidence\": \"NMR chemical shift perturbation, mutagenesis, pulldowns, and in vitro/in cellulo deadenylation assays\",\n      \"pmids\": [\"34060423\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model of the ternary RRM1–boxC–deadenylase assembly not solved\", \"Selectivity between BTG1 and BTG2 functions unaddressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the molecular logic of Paip2A-mediated translational repression: sequential RRM2 then RRM3 engagement displaces PABPC1 from poly(A), defining a competitive eviction mechanism.\",\n      \"evidence\": \"ITC, NMR, and competition binding with isolated RRM domains\",\n      \"pmids\": [\"35307347\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular triggers controlling Paip2A availability not addressed\", \"Kinetics of eviction on full-length mRNP unmeasured\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established PABPC1 (PABP domain) as a developmental-delay disease gene, with variants weakening the PAIP2 interaction and failing to support neural progenitor proliferation.\",\n      \"evidence\": \"Exome sequencing, Co-IP, in silico modeling, and in utero electroporation rescue in mouse embryo brain\",\n      \"pmids\": [\"35511136\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether weakened PAIP2 binding is the causal mechanism for all variants unconfirmed\", \"Downstream translational targets affected in neural progenitors unidentified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed acetylation of Pab1 at K131 by reducing poly(A) binding suppresses stress-granule formation, with Rpd3 as the deacetylase, adding acetylation as a stress-responsive switch.\",\n      \"evidence\": \"Acetylation-mimetic mutants, stress-granule imaging, EMSA, and rpd3 genetic epistasis in yeast\",\n      \"pmids\": [\"36572187\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Acetyltransferase responsible not identified\", \"Human PABPC1 K131 acetylation not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated USP10 deubiquitinates K27/K29 chains on PABPC1 RRM2 to enhance coupling of specific mRNAs to eIF4G1, providing a tumor-promoting translational control mechanism.\",\n      \"evidence\": \"Co-IP, deubiquitination and linkage-specific assays, RRM2 mutants, and xenograft models in PDAC\",\n      \"pmids\": [\"37757903\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Counterbalancing E3 ligase for these chains not defined here\", \"Selectivity for CLK2 mRNA mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a nuclear function in which PABPC1, with TPR, retains A-rich circRNAs in the nucleus, and its downregulation during differentiation permits circRNA export required for neurite outgrowth.\",\n      \"evidence\": \"Nuclear/cytoplasmic fractionation, PABPC1 manipulation, circRNA A-rich motif mutagenesis, neurite assays, and TPR Co-IP\",\n      \"pmids\": [\"38838666\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How PABPC1 distinguishes circRNA from linear poly(A) substrates unclear\", \"Generality beyond stem-cell/neuronal context untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Implicated PABPC1 in degradation of pathogenic C9orf72 GGGGCC repeat RNA via interactions with hnRNPA3 and the RNA exosome, linking it to repeat-expansion disease surveillance.\",\n      \"evidence\": \"APEX2 proximity biotinylation, proximity ligation, and PABPC1-knockdown repeat-RNA accumulation assays\",\n      \"pmids\": [\"38444607\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct exosome recruitment vs. indirect effect not separated\", \"Proximity-based evidence lacks reconstitution\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified PABPC1 condensate formation as a driver of leukaemogenic mRNA translation in CML blast crisis, nominating it as a therapeutic target that overcomes TKI resistance.\",\n      \"evidence\": \"Genome-scale CRISPR screen, condensate imaging, polysome profiling, translation-efficiency analysis, and pharmacological inhibition in CML models\",\n      \"pmids\": [\"40102686\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants of condensate selectivity for structured 5' UTR mRNAs not defined\", \"How condensation alters initiation kinetics mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed stress-induced SUMOylation of PABPC1 drives stress-granule assembly via a TIA1 complex that selectively stabilizes U-rich mRNAs and supports mitophagy gene expression.\",\n      \"evidence\": \"SUMOylation assays, stress-granule imaging, transcriptome-wide stability analysis, TIA1 Co-IP, and mitophagy readouts\",\n      \"pmids\": [\"40774970\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SUMO sites and responsible E3 ligase not fully mapped\", \"How SUMO-PABPC1 selects U-rich elements mechanistically unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Used acute Pab1 depletion to show its primary in vivo role is blocking decapping/decay, with closed-loop eIF4G contact dispensable for most yeast translation, reframing the canonical scaffolding model.\",\n      \"evidence\": \"Auxin-inducible degron depletion, RNA-Seq, Ribo-Seq, dcp2Δ epistasis, and polysome profiling in yeast\",\n      \"pmids\": [\"40071937\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the same hierarchy holds in metazoan PABPC1 untested\", \"Transcript subsets that do require closed-loop initiation not fully enumerated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the array of PABPC1 post-translational modifications, conformational states, and partner interactions are integrated to determine, on a given mRNA, whether PABPC1 promotes translation, licenses deadenylation, or drives condensate/stress-granule sequestration.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking modification state to functional output\", \"Quantitative rules governing partner competition on a single mRNP unknown\", \"Crosstalk between nuclear and cytoplasmic functions undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [9, 10, 26, 28, 31]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [6, 10, 25, 27, 32]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 3, 7, 20, 21]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 20, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [14, 31]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 31]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [1, 2, 4, 7, 20]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [6, 8, 18, 25, 27]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [26, 28]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [19, 22, 25, 29]}\n    ],\n    \"complexes\": [\"stress granule\", \"CCR4-NOT (associated)\"],\n    \"partners\": [\"EIF4G1\", \"ERF3\", \"TNRC6A\", \"BTG2\", \"PAIP2\", \"LARP1\", \"TIA1\", \"AGO2\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}