{"gene":"PNRC2","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2001,"finding":"PNRC2 was identified as a nuclear receptor coactivator that interacts with the ligand-binding domains of multiple nuclear receptors (SF1, ERRα1, ER, GR, PR, TR, RAR, RXR) via a proline-rich SH3-binding motif (SEPPSPS); a functional AF-2 domain is required on the receptor side, and mutagenesis of the SH3-binding motif abolishes these interactions.","method":"Yeast two-hybrid screening, mutagenesis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid with mutagenesis across multiple receptors, single lab, no in vitro reconstitution","pmids":["11574675"],"is_preprint":false},{"year":2003,"finding":"PNRC2 directly interacts with the AF-1 domain of orphan nuclear receptor ERRγ and functions as a transcriptional coactivator for ERRγ, as demonstrated by phage display biopanning, pull-down assays, and reporter gene analysis.","method":"Phage display biopanning, pull-down assay, reporter gene (luciferase) assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein interaction confirmed by pull-down and functional reporter, single lab, two orthogonal methods","pmids":["14651967"],"is_preprint":false},{"year":2005,"finding":"Transcription of the mouse PNRC2 gene is activated by nuclear factor Y (NFY) and repressed by E2F1; NFY and E2F1 directly bind the minimal PNRC2 promoter region (-67/+53), as shown by gel shift, supershift, and ChIP assays.","method":"Deletion mutagenesis, luciferase reporter assay, gel shift/supershift, ChIP","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (EMSA, ChIP, reporter), single lab","pmids":["16181749"],"is_preprint":false},{"year":2007,"finding":"PNRC2-null mice generated by gene targeting are lean, resistant to high-fat diet-induced obesity, and have higher metabolic rates (increased oxygen consumption and heat production) without insulin resistance, establishing PNRC2's role in energy balance and adiposity.","method":"Gene targeting (knockout mice), metabolic phenotyping (indirect calorimetry, body composition)","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with defined metabolic phenotype, single lab","pmids":["17971453"],"is_preprint":false},{"year":2012,"finding":"Crystal structure of Dcp1a in complex with PNRC2 reveals that the proline-rich region of PNRC2 binds the EVH1 domain of Dcp1a (via a mode distinct from other EVH1/proline-rich interactions), while the NR-box of PNRC2 mediates interaction with hyperphosphorylated UPF1. Disruption of the Dcp1a-PNRC2 interaction abolishes P-body localization and mRNA degradation activity. PNRC2 bridges Dcp1a and Dcp2, stimulating decapping activity, identifying it as a decapping coactivator.","method":"X-ray crystallography, tethering/reporter mRNA decay assays, co-immunoprecipitation, P-body localization (microscopy), mutagenesis","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional mutagenesis, multiple orthogonal methods (structural, biochemical, cellular), single rigorous study","pmids":["23085078"],"is_preprint":false},{"year":2012,"finding":"PNRC2 preferentially forms a complex with SMG5 (but not SMG6 or SMG7) during NMD; knockdown of PNRC2 abolishes the SMG5–Dcp1a interaction; tethering experiments place UPF1, SMG5, and PNRC2 at the same NMD step; microarray analysis shows SMG5-dependent NMD substrates overlap more with PNRC2-dependent than SMG7-dependent substrates, indicating functional dominance of the SMG5-PNRC2 complex.","method":"Co-immunoprecipitation, siRNA knockdown, tethering assay, microarray","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and functional tethering assays with genome-wide support, single lab","pmids":["23234702"],"is_preprint":false},{"year":2013,"finding":"Peptides derived from the PxxP SH3-binding motifs of PNRC2 adopt polyproline II (PPII) helical conformations (confirmed by ECD, MD, and NMR) and competitively displace a synthetic ERα-derived peptide from the AF-2 coregulator recruitment site of ERα, supporting a PPII-based mechanism for PNRC2–ERα interaction.","method":"Electronic circular dichroism (ECD), molecular dynamics, 2D NMR, competitive binding assay","journal":"Chirality","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — structural (NMR/ECD) with binding assay, single lab, peptide-level study without full-protein validation","pmids":["23925889"],"is_preprint":false},{"year":2015,"finding":"Glucocorticoid receptor (GR) recruits UPF1 through PNRC2 in a ligand-dependent manner when preloaded on the 5'UTR of target mRNAs, triggering GR-mediated mRNA decay (GMD); GMD is mechanistically distinct from NMD and SMD despite sharing UPF1 and PNRC2; GMD targets CCL2 mRNA and functionally controls chemotaxis of human monocytes.","method":"Co-immunoprecipitation, tethering assay, siRNA knockdown, microarray, chemotaxis assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, tethering, KD, functional cell assay, genome-wide substrate identification), single rigorous study","pmids":["25775514"],"is_preprint":false},{"year":2017,"finding":"In zebrafish, pnrc2 (tortuga locus) is required for decay of cyclic segmentation clock transcripts (her1, deltaC); the her1 3'UTR confers Pnrc2-dependent instability to heterologous transcripts; decay is Dicer-independent and likely employs a Pnrc2-UPF1-containing mRNA decay complex; loss of pnrc2 causes cyclic mRNA accumulation without loss of oscillatory protein expression.","method":"Zebrafish forward genetic screen, loss-of-function (mutant), inducible in vivo reporter system (3'UTR stability assay), genetic epistasis","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined molecular phenotype and in vivo reporter validation, single lab","pmids":["28648842"],"is_preprint":false},{"year":2018,"finding":"Contrary to prior reports, no physical or functional interaction between SMG5 and PNRC2 was detected in NMD; instead, UPF1 directly interacts with PNRC2; PNRC2 interacts mainly with decapping factors; PNRC2 knockdown does not affect NMD reporter RNA levels, suggesting PNRC2 is an mRNA decapping factor but is not required for NMD.","method":"Interaction mapping (Co-IP), siRNA knockdown, tethering/reporter assay","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction mapping and functional reporter assay, single lab; contradicts prior SMG5-PNRC2 complex reports","pmids":["29348139"],"is_preprint":false},{"year":2020,"finding":"In zebrafish, the terminal 179 nt of the her1 3'UTR (containing Pumilio response elements [PREs] and AU-rich elements [AREs]) are necessary and sufficient for Pnrc2-dependent rapid mRNA decay; mutation of Pnrc2 residues that mediate interactions with DCP1A and UPF1 reduces its ability to restore cyclic gene expression, confirming that Pnrc2 acts through these decay factor interactions in vivo.","method":"Transgenic inducible reporter lines (3'UTR deletion/mutation series), in vivo mRNA stability assay, site-directed mutagenesis of Pnrc2 interaction domains","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic transgenic reporter series with mutagenesis of interaction domains, single lab, in vivo","pmids":["32246943"],"is_preprint":false},{"year":2025,"finding":"In zebrafish pnrc2 mutants, overexpressed transcripts accumulate with shortened poly(A) tails and are disengaged from ribosomes; deadenylation inhibition causes somite defects in pnrc2 mutants; transcripts encoding P-body protein Ddx61 are overexpressed and engaged with ribosomes, increasing Ddx61 protein; co-depletion of Ddx61 and Ddx6 enhances her1 accumulation and causes morphological defects in pnrc2 mutants, revealing a compensatory post-transcriptional mechanism.","method":"Polysome profiling, poly(A) tail length assay, genetic co-depletion (morpholino/mutant), pharmacological deadenylation inhibition, western blot","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (polysome profiling, poly(A) assay, genetic epistasis), preprint not yet peer-reviewed","pmids":["40463158"],"is_preprint":true}],"current_model":"PNRC2 is a small proline-rich adaptor protein that bridges mRNA surveillance and decapping machinery: its NR-box interacts with hyperphosphorylated UPF1 while its proline-rich region binds the EVH1 domain of DCP1A (crystal structure resolved), and it stimulates DCP2 decapping activity by bridging DCP1A–DCP2; it functions as an adaptor in multiple mRNA decay pathways including NMD (in complex with SMG5), glucocorticoid receptor-mediated mRNA decay (GMD, recruited by ligand-bound GR to target mRNAs), and decay of segmentation clock transcripts in zebrafish (promoting 3'UTR-directed, PRE/ARE-dependent rapid turnover); it also acts as a coactivator for multiple nuclear receptors via its SH3-binding motif, and its loss in mice causes lean phenotype with increased energy expenditure."},"narrative":{"mechanistic_narrative":"PNRC2 is a small proline-rich adaptor protein that links mRNA surveillance machinery to the decapping apparatus and additionally serves as a nuclear receptor coactivator [PMID:23085078, PMID:11574675]. Its proline-rich region binds the EVH1 domain of the decapping factor DCP1A through a distinct binding mode resolved by crystallography, while its NR-box engages hyperphosphorylated UPF1; through these contacts PNRC2 bridges DCP1A and DCP2 to stimulate decapping activity, and disruption of the DCP1A interaction abolishes both P-body localization and mRNA degradation [PMID:23085078]. PNRC2 acts as an adaptor across multiple UPF1-dependent decay pathways: it operates in glucocorticoid receptor-mediated mRNA decay (GMD), in which ligand-bound GR preloaded on target 5'UTRs recruits UPF1 via PNRC2 to drive decay of substrates such as CCL2 and thereby control monocyte chemotaxis [PMID:25775514], and in zebrafish it is required for the rapid 3'UTR-directed turnover of cyclic segmentation clock transcripts (her1, deltaC), acting through PRE/ARE elements and its DCP1A and UPF1 interaction surfaces [PMID:28648842, PMID:32246943]. In its second role, PNRC2 functions as a coactivator for multiple nuclear receptors, binding receptor ligand-binding and activation-function domains through a polyproline II-forming SH3-binding motif (SEPPSPS) [PMID:11574675, PMID:14651967, PMID:23925889]. Loss of PNRC2 in mice produces a lean phenotype with increased energy expenditure and resistance to diet-induced obesity, establishing a role in energy balance [PMID:17971453]. The role of PNRC2 in classical NMD is unresolved within the corpus: one study placed it in an SMG5-PNRC2 complex acting at the same step as UPF1 [PMID:23234702], while a later study failed to detect SMG5-PNRC2 interaction and found PNRC2 knockdown did not affect NMD reporter levels, recasting PNRC2 as a decapping factor dispensable for NMD [PMID:29348139].","teleology":[{"year":2001,"claim":"Established PNRC2's first identified function as a broad nuclear receptor coactivator, defining the SH3-binding motif as its receptor-engaging element.","evidence":"Yeast two-hybrid screening with mutagenesis across multiple nuclear receptors","pmids":["11574675"],"confidence":"Medium","gaps":["No in vitro reconstitution of the coactivation event","Transcriptional consequences shown only via interaction, not endogenous target genes"]},{"year":2003,"claim":"Extended coactivator function to ERRγ and showed PNRC2 engages an activation-function domain directly, supporting a general coregulatory role.","evidence":"Phage display biopanning, pull-down, and luciferase reporter assays","pmids":["14651967"],"confidence":"Medium","gaps":["Single receptor context","Mechanism of transcriptional activation not defined"]},{"year":2005,"claim":"Defined how PNRC2 expression itself is controlled, placing the gene downstream of NFY activation and E2F1 repression.","evidence":"Promoter deletion, reporter, EMSA/supershift, and ChIP assays in mouse","pmids":["16181749"],"confidence":"Medium","gaps":["Physiological conditions driving NFY/E2F1 control not established","Links to PNRC2 functional output not addressed"]},{"year":2007,"claim":"Demonstrated an organismal role for PNRC2 in energy balance, showing its loss confers leanness and elevated metabolic rate.","evidence":"Knockout mice with indirect calorimetry and body composition phenotyping","pmids":["17971453"],"confidence":"Medium","gaps":["Molecular basis linking PNRC2 loss to increased energy expenditure unresolved","Tissue-specific contributions not dissected"]},{"year":2012,"claim":"Provided the structural and mechanistic core: PNRC2 bridges DCP1A and DCP2 to stimulate decapping and uses its NR-box to bind hyperphosphorylated UPF1, defining it as a decapping coactivator.","evidence":"X-ray crystallography of DCP1A-PNRC2, tethered decay assays, Co-IP, P-body microscopy, mutagenesis","pmids":["23085078"],"confidence":"High","gaps":["Stoichiometry of the DCP1A-DCP2-PNRC2 assembly not fully defined","How UPF1 phosphorylation gates recruitment not structurally resolved"]},{"year":2012,"claim":"Placed PNRC2 in NMD via a preferential SMG5-PNRC2 complex acting at the UPF1 step, proposing functional dominance over the SMG7 branch.","evidence":"Reciprocal Co-IP, siRNA knockdown, tethering assays, and microarray substrate overlap","pmids":["23234702"],"confidence":"Medium","gaps":["SMG5-PNRC2 interaction later not reproduced","Direct requirement for PNRC2 in NMD contested"]},{"year":2015,"claim":"Identified a distinct decay pathway, GMD, in which ligand-bound GR recruits UPF1 through PNRC2 to degrade 5'UTR-loaded target mRNAs with a defined cellular output.","evidence":"Co-IP, tethering, siRNA knockdown, microarray, and monocyte chemotaxis assay","pmids":["25775514"],"confidence":"High","gaps":["How GR loading on 5'UTRs is targeted to specific transcripts not fully defined","Generality of GMD beyond identified substrates unclear"]},{"year":2017,"claim":"Demonstrated an in vivo developmental requirement for PNRC2-mediated decay in clearing oscillatory segmentation clock transcripts.","evidence":"Zebrafish forward genetic screen, loss-of-function mutant, inducible 3'UTR reporter, epistasis","pmids":["28648842"],"confidence":"Medium","gaps":["Decay complex composition inferred rather than purified","Why protein oscillation persists despite mRNA accumulation unexplained"]},{"year":2018,"claim":"Reassessed PNRC2's role in NMD, finding direct UPF1-PNRC2 and decapping-factor interactions but no SMG5 link and no NMD reporter dependence, recasting PNRC2 as a decapping factor not required for NMD.","evidence":"Interaction mapping by Co-IP, siRNA knockdown, tethering/reporter assays","pmids":["29348139"],"confidence":"Medium","gaps":["Discrepancy with prior SMG5-PNRC2 model unresolved","Conditions under which PNRC2 contributes to endogenous NMD not delineated"]},{"year":2020,"claim":"Mapped the cis-element basis of PNRC2-dependent decay and confirmed in vivo that PNRC2 acts through its DCP1A and UPF1 interaction surfaces.","evidence":"Transgenic inducible 3'UTR deletion/mutation reporter series with PNRC2 interaction-domain mutagenesis in zebrafish","pmids":["32246943"],"confidence":"Medium","gaps":["Factors reading PREs/AREs to recruit PNRC2 not identified","Quantitative contribution of each element not separated"]},{"year":2025,"claim":"Revealed that PNRC2-dependent decay involves deadenylation and translational disengagement and that compensatory P-body machinery buffers its loss.","evidence":"Polysome profiling, poly(A) tail assays, genetic co-depletion, and pharmacological deadenylation inhibition in zebrafish (preprint)","pmids":["40463158"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Order of deadenylation versus decapping in the pathway not resolved","Mechanism of Ddx61/Ddx6 compensation not detailed"]},{"year":null,"claim":"Whether PNRC2 functions in canonical NMD and how its decapping-adaptor role mechanistically connects to its nuclear receptor coactivation and the murine metabolic phenotype remain open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Conflicting evidence on PNRC2 requirement in NMD unreconciled","No mechanistic bridge between cytoplasmic decay function and nuclear coactivator function","Molecular cause of the lean knockout phenotype unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,7]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4]}],"localization":[{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[4,5,7]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,1]}],"complexes":["DCP1A-DCP2 decapping complex"],"partners":["DCP1A","DCP2","UPF1","SMG5","GR","ERRG","ESR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NPJ4","full_name":"Proline-rich nuclear receptor coactivator 2","aliases":[],"length_aa":139,"mass_kda":15.6,"function":"Involved in nonsense-mediated mRNA decay (NMD) by acting as a bridge between the mRNA decapping complex and the NMD machinery (PubMed:19150429). May act by targeting the NMD machinery to the P-body and recruiting the decapping machinery to aberrant mRNAs (PubMed:19150429). Required for UPF1/RENT1 localization to the P-body (PubMed:19150429). Plays a role in glucocorticoid receptor-mediated mRNA degradation by interacting with the glucocorticoid receptor NR3C1 in a ligand-dependent manner when it is bound to the 5' UTR of target mRNAs and recruiting the RNA helicase UPF1 and the mRNA-decapping enzyme DCP1A, leading to RNA decay (PubMed:25775514). Also acts as a nuclear receptor coactivator (PubMed:11574675). May play a role in controlling the energy balance between energy storage and energy expenditure (By similarity)","subcellular_location":"Nucleus; Cytoplasm, P-body","url":"https://www.uniprot.org/uniprotkb/Q9NPJ4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PNRC2","classification":"Not Classified","n_dependent_lines":177,"n_total_lines":1208,"dependency_fraction":0.14652317880794702},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PNRC2","total_profiled":1310},"omim":[{"mim_id":"611882","title":"PROLINE-RICH NUCLEAR RECEPTOR COACTIVATOR 2; PNRC2","url":"https://www.omim.org/entry/611882"},{"mim_id":"602969","title":"ESTROGEN-RELATED RECEPTOR, GAMMA; ESRRG","url":"https://www.omim.org/entry/602969"},{"mim_id":"600189","title":"TLE FAMILY MEMBER 1, TRANSCRIPTIONAL COREPRESSOR; TLE1","url":"https://www.omim.org/entry/600189"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PNRC2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9NPJ4","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NPJ4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NPJ4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NPJ4-F1-predicted_aligned_error_v6.png","plddt_mean":67.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PNRC2","jax_strain_url":"https://www.jax.org/strain/search?query=PNRC2"},"sequence":{"accession":"Q9NPJ4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NPJ4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NPJ4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NPJ4"}},"corpus_meta":[{"pmid":"23234702","id":"PMC_23234702","title":"SMG5-PNRC2 is functionally dominant compared with SMG5-SMG7 in mammalian nonsense-mediated mRNA decay.","date":"2012","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/23234702","citation_count":73,"is_preprint":false},{"pmid":"23085078","id":"PMC_23085078","title":"Structural basis of the PNRC2-mediated link between mrna surveillance and decapping.","date":"2012","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/23085078","citation_count":62,"is_preprint":false},{"pmid":"25775514","id":"PMC_25775514","title":"Glucocorticoid receptor interacts with PNRC2 in a ligand-dependent manner to recruit UPF1 for rapid mRNA degradation.","date":"2015","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/25775514","citation_count":61,"is_preprint":false},{"pmid":"11574675","id":"PMC_11574675","title":"PNRC2 is a 16 kDa coactivator that interacts with nuclear receptors through an SH3-binding motif.","date":"2001","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/11574675","citation_count":52,"is_preprint":false},{"pmid":"29348139","id":"PMC_29348139","title":"Dissecting the functions of SMG5, SMG7, and PNRC2 in nonsense-mediated mRNA decay of human cells.","date":"2018","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/29348139","citation_count":27,"is_preprint":false},{"pmid":"14651967","id":"PMC_14651967","title":"Identification of PNRC2 and TLE1 as activation function-1 cofactors of the orphan nuclear receptor ERRgamma.","date":"2003","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/14651967","citation_count":27,"is_preprint":false},{"pmid":"33686892","id":"PMC_33686892","title":"LncRNA OTUD6B-AS1 inhibits many cellular processes in colorectal cancer by sponging miR-21-5p and regulating PNRC2.","date":"2021","source":"Human & experimental toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/33686892","citation_count":14,"is_preprint":false},{"pmid":"17971453","id":"PMC_17971453","title":"Nuclear receptor coactivator PNRC2 regulates energy expenditure and adiposity.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17971453","citation_count":13,"is_preprint":false},{"pmid":"16181749","id":"PMC_16181749","title":"Transcriptional regulation of the mouse PNRC2 promoter by the nuclear factor Y (NFY) and E2F1.","date":"2005","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/16181749","citation_count":13,"is_preprint":false},{"pmid":"32246943","id":"PMC_32246943","title":"Pumilio response and AU-rich elements drive rapid decay of Pnrc2-regulated cyclic gene transcripts.","date":"2020","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/32246943","citation_count":5,"is_preprint":false},{"pmid":"28648842","id":"PMC_28648842","title":"Pnrc2 regulates 3'UTR-mediated decay of segmentation clock-associated transcripts during zebrafish segmentation.","date":"2017","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/28648842","citation_count":5,"is_preprint":false},{"pmid":"23925889","id":"PMC_23925889","title":"Identification of polyproline II regions derived from the proline-rich nuclear receptor coactivators PNRC and PNRC2: new insights for ERα coactivator interactions.","date":"2013","source":"Chirality","url":"https://pubmed.ncbi.nlm.nih.gov/23925889","citation_count":4,"is_preprint":false},{"pmid":"33752469","id":"PMC_33752469","title":"Long non-coding (lnc)RNA profiling and the role of a key regulator lnc-PNRC2-1 in the transforming growth factor-β1-induced epithelial-mesenchymal transition of CNE1 nasopharyngeal carcinoma cells.","date":"2021","source":"The Journal of international medical research","url":"https://pubmed.ncbi.nlm.nih.gov/33752469","citation_count":3,"is_preprint":false},{"pmid":"40463158","id":"PMC_40463158","title":"Pnrc2 promotes rapid mRNA decay and coordinately supports early development with P-body factors Ddx6 and Ddx61.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40463158","citation_count":0,"is_preprint":false},{"pmid":"39851226","id":"PMC_39851226","title":"LncRNA ZNF667-AS1: A Promising Therapeutic Target for Colorectal Cancer by Regulating PNRC2-Mediated Cell Proliferation, Invasion and Apoptosis.","date":"2025","source":"Discovery medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39851226","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.08.652725","title":"P-body factors Ddx6 and Ddx61 support development in mRNA-decay deficient  <i>pnrc2</i>  mutants","date":"2025-05-14","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.08.652725","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10087,"output_tokens":3177,"usd":0.038958,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10639,"output_tokens":3658,"usd":0.072322,"stage2_stop_reason":"end_turn"},"total_usd":0.11128,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"PNRC2 was identified as a nuclear receptor coactivator that interacts with the ligand-binding domains of multiple nuclear receptors (SF1, ERRα1, ER, GR, PR, TR, RAR, RXR) via a proline-rich SH3-binding motif (SEPPSPS); a functional AF-2 domain is required on the receptor side, and mutagenesis of the SH3-binding motif abolishes these interactions.\",\n      \"method\": \"Yeast two-hybrid screening, mutagenesis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid with mutagenesis across multiple receptors, single lab, no in vitro reconstitution\",\n      \"pmids\": [\"11574675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PNRC2 directly interacts with the AF-1 domain of orphan nuclear receptor ERRγ and functions as a transcriptional coactivator for ERRγ, as demonstrated by phage display biopanning, pull-down assays, and reporter gene analysis.\",\n      \"method\": \"Phage display biopanning, pull-down assay, reporter gene (luciferase) assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein interaction confirmed by pull-down and functional reporter, single lab, two orthogonal methods\",\n      \"pmids\": [\"14651967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Transcription of the mouse PNRC2 gene is activated by nuclear factor Y (NFY) and repressed by E2F1; NFY and E2F1 directly bind the minimal PNRC2 promoter region (-67/+53), as shown by gel shift, supershift, and ChIP assays.\",\n      \"method\": \"Deletion mutagenesis, luciferase reporter assay, gel shift/supershift, ChIP\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (EMSA, ChIP, reporter), single lab\",\n      \"pmids\": [\"16181749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PNRC2-null mice generated by gene targeting are lean, resistant to high-fat diet-induced obesity, and have higher metabolic rates (increased oxygen consumption and heat production) without insulin resistance, establishing PNRC2's role in energy balance and adiposity.\",\n      \"method\": \"Gene targeting (knockout mice), metabolic phenotyping (indirect calorimetry, body composition)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with defined metabolic phenotype, single lab\",\n      \"pmids\": [\"17971453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structure of Dcp1a in complex with PNRC2 reveals that the proline-rich region of PNRC2 binds the EVH1 domain of Dcp1a (via a mode distinct from other EVH1/proline-rich interactions), while the NR-box of PNRC2 mediates interaction with hyperphosphorylated UPF1. Disruption of the Dcp1a-PNRC2 interaction abolishes P-body localization and mRNA degradation activity. PNRC2 bridges Dcp1a and Dcp2, stimulating decapping activity, identifying it as a decapping coactivator.\",\n      \"method\": \"X-ray crystallography, tethering/reporter mRNA decay assays, co-immunoprecipitation, P-body localization (microscopy), mutagenesis\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional mutagenesis, multiple orthogonal methods (structural, biochemical, cellular), single rigorous study\",\n      \"pmids\": [\"23085078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PNRC2 preferentially forms a complex with SMG5 (but not SMG6 or SMG7) during NMD; knockdown of PNRC2 abolishes the SMG5–Dcp1a interaction; tethering experiments place UPF1, SMG5, and PNRC2 at the same NMD step; microarray analysis shows SMG5-dependent NMD substrates overlap more with PNRC2-dependent than SMG7-dependent substrates, indicating functional dominance of the SMG5-PNRC2 complex.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, tethering assay, microarray\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and functional tethering assays with genome-wide support, single lab\",\n      \"pmids\": [\"23234702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Peptides derived from the PxxP SH3-binding motifs of PNRC2 adopt polyproline II (PPII) helical conformations (confirmed by ECD, MD, and NMR) and competitively displace a synthetic ERα-derived peptide from the AF-2 coregulator recruitment site of ERα, supporting a PPII-based mechanism for PNRC2–ERα interaction.\",\n      \"method\": \"Electronic circular dichroism (ECD), molecular dynamics, 2D NMR, competitive binding assay\",\n      \"journal\": \"Chirality\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — structural (NMR/ECD) with binding assay, single lab, peptide-level study without full-protein validation\",\n      \"pmids\": [\"23925889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Glucocorticoid receptor (GR) recruits UPF1 through PNRC2 in a ligand-dependent manner when preloaded on the 5'UTR of target mRNAs, triggering GR-mediated mRNA decay (GMD); GMD is mechanistically distinct from NMD and SMD despite sharing UPF1 and PNRC2; GMD targets CCL2 mRNA and functionally controls chemotaxis of human monocytes.\",\n      \"method\": \"Co-immunoprecipitation, tethering assay, siRNA knockdown, microarray, chemotaxis assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, tethering, KD, functional cell assay, genome-wide substrate identification), single rigorous study\",\n      \"pmids\": [\"25775514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In zebrafish, pnrc2 (tortuga locus) is required for decay of cyclic segmentation clock transcripts (her1, deltaC); the her1 3'UTR confers Pnrc2-dependent instability to heterologous transcripts; decay is Dicer-independent and likely employs a Pnrc2-UPF1-containing mRNA decay complex; loss of pnrc2 causes cyclic mRNA accumulation without loss of oscillatory protein expression.\",\n      \"method\": \"Zebrafish forward genetic screen, loss-of-function (mutant), inducible in vivo reporter system (3'UTR stability assay), genetic epistasis\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined molecular phenotype and in vivo reporter validation, single lab\",\n      \"pmids\": [\"28648842\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Contrary to prior reports, no physical or functional interaction between SMG5 and PNRC2 was detected in NMD; instead, UPF1 directly interacts with PNRC2; PNRC2 interacts mainly with decapping factors; PNRC2 knockdown does not affect NMD reporter RNA levels, suggesting PNRC2 is an mRNA decapping factor but is not required for NMD.\",\n      \"method\": \"Interaction mapping (Co-IP), siRNA knockdown, tethering/reporter assay\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction mapping and functional reporter assay, single lab; contradicts prior SMG5-PNRC2 complex reports\",\n      \"pmids\": [\"29348139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In zebrafish, the terminal 179 nt of the her1 3'UTR (containing Pumilio response elements [PREs] and AU-rich elements [AREs]) are necessary and sufficient for Pnrc2-dependent rapid mRNA decay; mutation of Pnrc2 residues that mediate interactions with DCP1A and UPF1 reduces its ability to restore cyclic gene expression, confirming that Pnrc2 acts through these decay factor interactions in vivo.\",\n      \"method\": \"Transgenic inducible reporter lines (3'UTR deletion/mutation series), in vivo mRNA stability assay, site-directed mutagenesis of Pnrc2 interaction domains\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic transgenic reporter series with mutagenesis of interaction domains, single lab, in vivo\",\n      \"pmids\": [\"32246943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In zebrafish pnrc2 mutants, overexpressed transcripts accumulate with shortened poly(A) tails and are disengaged from ribosomes; deadenylation inhibition causes somite defects in pnrc2 mutants; transcripts encoding P-body protein Ddx61 are overexpressed and engaged with ribosomes, increasing Ddx61 protein; co-depletion of Ddx61 and Ddx6 enhances her1 accumulation and causes morphological defects in pnrc2 mutants, revealing a compensatory post-transcriptional mechanism.\",\n      \"method\": \"Polysome profiling, poly(A) tail length assay, genetic co-depletion (morpholino/mutant), pharmacological deadenylation inhibition, western blot\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (polysome profiling, poly(A) assay, genetic epistasis), preprint not yet peer-reviewed\",\n      \"pmids\": [\"40463158\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"PNRC2 is a small proline-rich adaptor protein that bridges mRNA surveillance and decapping machinery: its NR-box interacts with hyperphosphorylated UPF1 while its proline-rich region binds the EVH1 domain of DCP1A (crystal structure resolved), and it stimulates DCP2 decapping activity by bridging DCP1A–DCP2; it functions as an adaptor in multiple mRNA decay pathways including NMD (in complex with SMG5), glucocorticoid receptor-mediated mRNA decay (GMD, recruited by ligand-bound GR to target mRNAs), and decay of segmentation clock transcripts in zebrafish (promoting 3'UTR-directed, PRE/ARE-dependent rapid turnover); it also acts as a coactivator for multiple nuclear receptors via its SH3-binding motif, and its loss in mice causes lean phenotype with increased energy expenditure.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PNRC2 is a small proline-rich adaptor protein that links mRNA surveillance machinery to the decapping apparatus and additionally serves as a nuclear receptor coactivator [#4, #0]. Its proline-rich region binds the EVH1 domain of the decapping factor DCP1A through a distinct binding mode resolved by crystallography, while its NR-box engages hyperphosphorylated UPF1; through these contacts PNRC2 bridges DCP1A and DCP2 to stimulate decapping activity, and disruption of the DCP1A interaction abolishes both P-body localization and mRNA degradation [#4]. PNRC2 acts as an adaptor across multiple UPF1-dependent decay pathways: it operates in glucocorticoid receptor-mediated mRNA decay (GMD), in which ligand-bound GR preloaded on target 5'UTRs recruits UPF1 via PNRC2 to drive decay of substrates such as CCL2 and thereby control monocyte chemotaxis [#7], and in zebrafish it is required for the rapid 3'UTR-directed turnover of cyclic segmentation clock transcripts (her1, deltaC), acting through PRE/ARE elements and its DCP1A and UPF1 interaction surfaces [#8, #10]. In its second role, PNRC2 functions as a coactivator for multiple nuclear receptors, binding receptor ligand-binding and activation-function domains through a polyproline II-forming SH3-binding motif (SEPPSPS) [#0, #1, #6]. Loss of PNRC2 in mice produces a lean phenotype with increased energy expenditure and resistance to diet-induced obesity, establishing a role in energy balance [#3]. The role of PNRC2 in classical NMD is unresolved within the corpus: one study placed it in an SMG5-PNRC2 complex acting at the same step as UPF1 [#5], while a later study failed to detect SMG5-PNRC2 interaction and found PNRC2 knockdown did not affect NMD reporter levels, recasting PNRC2 as a decapping factor dispensable for NMD [#9].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established PNRC2's first identified function as a broad nuclear receptor coactivator, defining the SH3-binding motif as its receptor-engaging element.\",\n      \"evidence\": \"Yeast two-hybrid screening with mutagenesis across multiple nuclear receptors\",\n      \"pmids\": [\"11574675\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of the coactivation event\", \"Transcriptional consequences shown only via interaction, not endogenous target genes\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Extended coactivator function to ERRγ and showed PNRC2 engages an activation-function domain directly, supporting a general coregulatory role.\",\n      \"evidence\": \"Phage display biopanning, pull-down, and luciferase reporter assays\",\n      \"pmids\": [\"14651967\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single receptor context\", \"Mechanism of transcriptional activation not defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined how PNRC2 expression itself is controlled, placing the gene downstream of NFY activation and E2F1 repression.\",\n      \"evidence\": \"Promoter deletion, reporter, EMSA/supershift, and ChIP assays in mouse\",\n      \"pmids\": [\"16181749\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological conditions driving NFY/E2F1 control not established\", \"Links to PNRC2 functional output not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrated an organismal role for PNRC2 in energy balance, showing its loss confers leanness and elevated metabolic rate.\",\n      \"evidence\": \"Knockout mice with indirect calorimetry and body composition phenotyping\",\n      \"pmids\": [\"17971453\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis linking PNRC2 loss to increased energy expenditure unresolved\", \"Tissue-specific contributions not dissected\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Provided the structural and mechanistic core: PNRC2 bridges DCP1A and DCP2 to stimulate decapping and uses its NR-box to bind hyperphosphorylated UPF1, defining it as a decapping coactivator.\",\n      \"evidence\": \"X-ray crystallography of DCP1A-PNRC2, tethered decay assays, Co-IP, P-body microscopy, mutagenesis\",\n      \"pmids\": [\"23085078\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of the DCP1A-DCP2-PNRC2 assembly not fully defined\", \"How UPF1 phosphorylation gates recruitment not structurally resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Placed PNRC2 in NMD via a preferential SMG5-PNRC2 complex acting at the UPF1 step, proposing functional dominance over the SMG7 branch.\",\n      \"evidence\": \"Reciprocal Co-IP, siRNA knockdown, tethering assays, and microarray substrate overlap\",\n      \"pmids\": [\"23234702\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"SMG5-PNRC2 interaction later not reproduced\", \"Direct requirement for PNRC2 in NMD contested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified a distinct decay pathway, GMD, in which ligand-bound GR recruits UPF1 through PNRC2 to degrade 5'UTR-loaded target mRNAs with a defined cellular output.\",\n      \"evidence\": \"Co-IP, tethering, siRNA knockdown, microarray, and monocyte chemotaxis assay\",\n      \"pmids\": [\"25775514\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How GR loading on 5'UTRs is targeted to specific transcripts not fully defined\", \"Generality of GMD beyond identified substrates unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated an in vivo developmental requirement for PNRC2-mediated decay in clearing oscillatory segmentation clock transcripts.\",\n      \"evidence\": \"Zebrafish forward genetic screen, loss-of-function mutant, inducible 3'UTR reporter, epistasis\",\n      \"pmids\": [\"28648842\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Decay complex composition inferred rather than purified\", \"Why protein oscillation persists despite mRNA accumulation unexplained\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Reassessed PNRC2's role in NMD, finding direct UPF1-PNRC2 and decapping-factor interactions but no SMG5 link and no NMD reporter dependence, recasting PNRC2 as a decapping factor not required for NMD.\",\n      \"evidence\": \"Interaction mapping by Co-IP, siRNA knockdown, tethering/reporter assays\",\n      \"pmids\": [\"29348139\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Discrepancy with prior SMG5-PNRC2 model unresolved\", \"Conditions under which PNRC2 contributes to endogenous NMD not delineated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Mapped the cis-element basis of PNRC2-dependent decay and confirmed in vivo that PNRC2 acts through its DCP1A and UPF1 interaction surfaces.\",\n      \"evidence\": \"Transgenic inducible 3'UTR deletion/mutation reporter series with PNRC2 interaction-domain mutagenesis in zebrafish\",\n      \"pmids\": [\"32246943\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Factors reading PREs/AREs to recruit PNRC2 not identified\", \"Quantitative contribution of each element not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed that PNRC2-dependent decay involves deadenylation and translational disengagement and that compensatory P-body machinery buffers its loss.\",\n      \"evidence\": \"Polysome profiling, poly(A) tail assays, genetic co-depletion, and pharmacological deadenylation inhibition in zebrafish (preprint)\",\n      \"pmids\": [\"40463158\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Order of deadenylation versus decapping in the pathway not resolved\", \"Mechanism of Ddx61/Ddx6 compensation not detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether PNRC2 functions in canonical NMD and how its decapping-adaptor role mechanistically connects to its nuclear receptor coactivation and the murine metabolic phenotype remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conflicting evidence on PNRC2 requirement in NMD unreconciled\", \"No mechanistic bridge between cytoplasmic decay function and nuclear coactivator function\", \"Molecular cause of the lean knockout phenotype unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 7]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [4, 5, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [\"DCP1A-DCP2 decapping complex\"],\n    \"partners\": [\"DCP1A\", \"DCP2\", \"UPF1\", \"SMG5\", \"GR\", \"ERRG\", \"ESR1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}