{"gene":"CSN2","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2003,"finding":"Targeted disruption of Csn2 in mice disrupts the intact COP9 signalosome (CSN) complex, causes drastic accumulation of cyclin E (consistent with loss of SCF-ubiquitin-proteasome-mediated protein turnover), and elevates p53 and p21 levels, resulting in cell proliferation arrest in the inner cell mass and early embryonic lethality at the peri-implantation stage.","method":"Csn2 knockout mouse (targeted gene disruption); blastocyst outgrowth assay; Western blotting for cyclin E, p53, p21, and CSN complex integrity; Oct4 immunostaining","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean in vivo KO with multiple defined molecular phenotypes (complex disruption, cyclin E/p53 accumulation) replicated across several orthogonal readouts in a single rigorous study","pmids":["12972599"],"is_preprint":false},{"year":2000,"finding":"CSN2 (Trip15) directly interacts with the interferon consensus sequence-binding protein ICSBP via its IRF association domain (IAD), and this association with the CSN complex leads to phosphorylation of ICSBP at a unique serine residue within its IAD; this phosphorylated residue is required for efficient ICSBP association with IRF-1 and for ICSBP-mediated transcriptional repression of IRF-1.","method":"Yeast two-hybrid screen (ICSBP-IAD bait vs. B-cell cDNA library); GST pull-down assay (in vitro); co-immunoprecipitation in COS7 cells; in vitro kinase assay (CSN-associated kinase phosphorylating ICSBP); site-directed mutagenesis of phosphorylation site","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal binding confirmed by Y2H + GST pulldown + co-IP; kinase assay with mutagenesis; multiple orthogonal methods in one study","pmids":["10991940"],"is_preprint":false},{"year":2002,"finding":"Drosophila Rpn6, a non-ATPase subunit of the 19S regulatory particle lid complex of the 26S proteasome, physically interacts with Alien/CSN2 (the Drosophila ortholog of mammalian CSN2) via its PCI domain, as demonstrated by yeast two-hybrid analysis, and their expression patterns overlap during development.","method":"Yeast two-hybrid screen (Alien/CSN2 as bait); temporal/spatial expression pattern analysis by in situ hybridization and immunohistochemistry; genetic analysis of Rpn6 P-element insertion mutants","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Y2H interaction supported by overlapping expression patterns but no in vivo co-IP confirmation; interaction domain (PCI) identified","pmids":["12426099"],"is_preprint":false},{"year":2003,"finding":"Trip15/CSN2 interacts with Nif3l1, a conserved transcriptional repressor; this interaction promotes nuclear translocation of Nif3l1 during retinoic acid-induced neural differentiation of P19 cells, and together they synergistically repress transcription. Trip15/CSN2 overexpression drives neuronal (but not glial) differentiation via downregulation of Oct-3/4 and induction of neurogenic genes Brn-2 and Mash-1.","method":"Yeast two-hybrid screen (Trip15/CSN2 as bait vs. P19 cDNA library); GST pull-down assay; epitope-tagged co-immunoprecipitation; immunofluorescence localization; luciferase reporter assay; sense/antisense mRNA overexpression in P19 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — interaction confirmed by Y2H + pulldown + co-IP; functional consequence tested with reporter assay and gain/loss-of-function in differentiation model; multiple orthogonal methods","pmids":["12522100"],"is_preprint":false},{"year":2003,"finding":"Trip15/CSN2 mRNA is induced at an early stage of neuronal differentiation in retinoic acid-treated P19 cells; enforced expression of Trip15/CSN2 is sufficient to convert P19 cells into neurons (but not glial cells) after aggregation without retinoic acid, accompanied by downregulation of Oct-3/4 and induction of neurogenic Brn-2 and Mash-1; antisense suppression of Trip15/CSN2 blocks commitment to neuronal lineage. In neonatal rat CNS, Trip15/CSN2 protein is localized to neuronal nuclei.","method":"Sense/antisense mRNA overexpression in P19 embryonal carcinoma cells; RT-PCR for marker genes (Oct-3/4, Brn-2, Mash-1); immunofluorescence localization in rat brain sections; in situ hybridization","journal":"Brain research. Developmental brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with defined molecular markers; nuclear localization confirmed by immunofluorescence; single lab, two complementary approaches","pmids":["12524175"],"is_preprint":false},{"year":2017,"finding":"In hepatocellular carcinoma cells, RMP activates NF-κB, which directly promotes expression of CSN2 (COP9 signalosome subunit 2); elevated CSN2 represses degradation of Snail, a transcriptional repressor of E-cadherin, thereby facilitating epithelial-mesenchymal transition and metastasis.","method":"Overexpression/knockdown of RMP and CSN2 in HCC cell lines; migration/invasion assays; Western blotting for E-cadherin, Snail, p65, CSN2; reporter assays for NF-κB; pulmonary metastasis mouse model; immunohistochemistry of human HCC tissues","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway placement by epistasis (RMP→NF-κB→CSN2→Snail) supported by KD/OE with defined molecular readouts and in vivo validation; single lab","pmids":["28423737"],"is_preprint":false},{"year":2016,"finding":"DDA1 promotes colon cancer progression through activation of the NF-κB/CSN2/GSK-3β signaling pathway; DDA1-mediated NF-κB activation upregulates CSN2, which in turn modulates GSK-3β activity to promote cell cycle progression, invasion, and EMT.","method":"DDA1 overexpression/suppression in colon cancer cell lines; cell proliferation, apoptosis, invasion, and EMT assays; Western blotting for p65, CSN2, GSK-3β; in vivo tumor growth assay; immunohistochemistry of patient tissues","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established by gain/loss-of-function with defined molecular readouts (CSN2, GSK-3β) and in vivo validation; single lab","pmids":["26942699"],"is_preprint":false}],"current_model":"CSN2 (COPS2/Trip15/Alien) encodes the second subunit of the COP9 signalosome (CSN), an eight-subunit complex that deconjugates Nedd8 from SCF cullin components to regulate SCF ubiquitin ligase activity and protein turnover (e.g., cyclin E, Snail); CSN2 also serves as a scaffold for CSN-associated kinase activities that phosphorylate substrates including ICSBP, thereby modulating transcription factor interactions, and plays a direct role in neuronal differentiation by promoting nuclear translocation of co-repressor Nif3l1 and downregulating Oct-3/4 to induce neurogenic gene expression; additionally, CSN2 is transcriptionally upregulated downstream of NF-κB in cancer contexts to suppress Snail and GSK-3β degradation, promoting EMT."},"narrative":{"mechanistic_narrative":"CSN2 (COPS2/Trip15/Alien) is an essential subunit of the COP9 signalosome (CSN) that controls protein turnover and transcriptional programs across embryonic development, differentiation, and cancer [PMID:12972599, PMID:12522100]. As a structural component of the intact CSN complex, CSN2 is required for SCF-cullin-dependent ubiquitin-proteasome degradation: its loss in mice disrupts the CSN, causes drastic accumulation of cyclin E and elevation of p53 and p21, arresting proliferation in the inner cell mass and producing peri-implantation lethality [PMID:12972599]. Consistent with a link to the proteolytic machinery, the Drosophila ortholog Alien/CSN2 binds the 19S proteasome lid subunit Rpn6 through its PCI domain [PMID:12426099]. CSN2 also scaffolds a CSN-associated kinase activity: it interacts directly with the transcription factor ICSBP via the IRF association domain and directs its phosphorylation, which is required for ICSBP-IRF-1 association and transcriptional repression [PMID:10991940]. In neuronal differentiation, CSN2 promotes nuclear translocation of the co-repressor Nif3l1 and downregulates Oct-3/4 while inducing the neurogenic genes Brn-2 and Mash-1, and is itself sufficient to drive P19 cells toward a neuronal fate [PMID:12522100, PMID:12524175]. In cancer, CSN2 is transcriptionally induced downstream of NF-κB, where it stabilizes Snail and modulates GSK-3β to promote epithelial-mesenchymal transition and metastasis [PMID:28423737, PMID:26942699].","teleology":[{"year":2000,"claim":"Established that CSN2 is not only a structural subunit but a docking platform coupling CSN-associated kinase activity to a transcription factor, defining a mechanism by which the complex regulates gene expression beyond proteolysis.","evidence":"Yeast two-hybrid, GST pull-down, co-IP in COS7, and in vitro kinase assay with phosphosite mutagenesis of ICSBP","pmids":["10991940"],"confidence":"High","gaps":["The identity of the CSN-associated kinase that phosphorylates ICSBP is not resolved","Whether this kinase scaffolding occurs within the intact eight-subunit CSN or via free CSN2 is not addressed"]},{"year":2002,"claim":"Linked CSN2 to the 26S proteasome by identifying a direct PCI-domain interaction with the 19S lid subunit Rpn6, suggesting physical coupling between the CSN and degradation machinery.","evidence":"Yeast two-hybrid with Alien/CSN2 bait and overlapping developmental expression analysis in Drosophila","pmids":["12426099"],"confidence":"Medium","gaps":["Y2H interaction lacks in vivo co-IP confirmation","Functional consequence of the CSN2-Rpn6 interaction was not tested","Conservation of the interaction in mammals not established"]},{"year":2003,"claim":"Demonstrated that CSN2 actively drives neuronal differentiation by partnering with the co-repressor Nif3l1 and reprogramming a transcriptional fate decision, extending CSN2 function into developmental gene control.","evidence":"Y2H, GST pull-down, co-IP, reporter assays, and gain/loss-of-function in retinoic-acid-treated P19 cells, plus neuronal nuclear localization in rat CNS","pmids":["12522100","12524175"],"confidence":"High","gaps":["Whether neuronal differentiation requires the intact CSN or CSN2 alone is unresolved","Mechanism connecting Nif3l1 repression to Oct-3/4 downregulation is not defined"]},{"year":2003,"claim":"Established CSN2's organismal essentiality and its mechanistic basis, showing the intact CSN is required to maintain SCF-driven turnover of cyclin E and proliferation control during early embryogenesis.","evidence":"Targeted Csn2 knockout mouse with blastocyst outgrowth assay and Western blotting for cyclin E, p53, p21, and CSN integrity","pmids":["12972599"],"confidence":"High","gaps":["Direct enzymatic role of CSN2 in cullin deneddylation not assayed","Which downstream phenotype (cyclin E vs p53/p21 accumulation) is causal for lethality not separated"]},{"year":2017,"claim":"Placed CSN2 in an oncogenic signaling axis, showing it is induced downstream of NF-κB and stabilizes Snail to drive EMT and metastasis.","evidence":"RMP/CSN2 overexpression and knockdown in HCC cells, migration/invasion assays, NF-κB reporters, and a pulmonary metastasis mouse model","pmids":["28423737"],"confidence":"Medium","gaps":["Mechanism by which CSN2 represses Snail degradation not defined at the ligase level","Single-lab study without independent replication"]},{"year":2016,"claim":"Generalized the NF-κB/CSN2 axis to colon cancer, implicating CSN2 in modulation of GSK-3β to promote cell cycle progression, invasion, and EMT.","evidence":"DDA1 gain/loss-of-function in colon cancer cells with EMT/proliferation assays, Western blotting for p65/CSN2/GSK-3β, and in vivo tumor growth","pmids":["26942699"],"confidence":"Medium","gaps":["Direct biochemical link between CSN2 and GSK-3β not demonstrated","Single-lab study without independent replication"]},{"year":null,"claim":"Whether CSN2 itself contributes catalytically to CSN deneddylase activity, versus serving purely as a structural and kinase-scaffolding subunit, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of CSN2 within the human CSN in the corpus","No direct assay of CSN2 contribution to cullin deneddylation","Identity of the CSN2-associated kinase remains unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,3]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3,4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[5,6]}],"complexes":["COP9 signalosome"],"partners":["ICSBP","NIF3L1","RPN6","IRF-1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P61201","full_name":"COP9 signalosome complex subunit 2","aliases":["Alien homolog","JAB1-containing signalosome subunit 2","Thyroid receptor-interacting protein 15","TR-interacting protein 15","TRIP-15"],"length_aa":443,"mass_kda":51.6,"function":"Essential component of the COP9 signalosome complex (CSN), a complex involved in various cellular and developmental processes. The CSN complex is an essential regulator of the ubiquitin (Ubl) conjugation pathway by mediating the deneddylation of the cullin subunits of SCF-type E3 ligase complexes, leading to decrease the Ubl ligase activity of SCF-type complexes such as SCF, CSA or DDB2. The complex is also involved in phosphorylation of p53/TP53, c-jun/JUN, IkappaBalpha/NFKBIA, ITPK1 and IRF8/ICSBP, possibly via its association with CK2 and PKD kinases. CSN-dependent phosphorylation of TP53 and JUN promotes and protects degradation by the Ubl system, respectively. Involved in early stage of neuronal differentiation via its interaction with NIF3L1","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/P61201/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CSN2","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CSN2","total_profiled":1310},"omim":[{"mim_id":"619043","title":"INOSITOL-PENTAKISPHOSPHATE 2-KINASE; IPPK","url":"https://www.omim.org/entry/619043"},{"mim_id":"616008","title":"COP9 SIGNALOSOME, SUBUNIT 4; COPS4","url":"https://www.omim.org/entry/616008"},{"mim_id":"609798","title":"NIMA-RELATED KINASE 9; NEK9","url":"https://www.omim.org/entry/609798"},{"mim_id":"604850","title":"COP9 SIGNALOSOME, SUBUNIT 5; COPS5","url":"https://www.omim.org/entry/604850"},{"mim_id":"604508","title":"COP9 SIGNALOSOME, SUBUNIT 2; COPS2","url":"https://www.omim.org/entry/604508"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"breast","ntpm":538.2}],"url":"https://www.proteinatlas.org/search/CSN2"},"hgnc":{"alias_symbol":[],"prev_symbol":["CASB"]},"alphafold":{"accession":"P61201","domains":[{"cath_id":"1.10.10.10","chopping":"365-421","consensus_level":"medium","plddt":88.2091,"start":365,"end":421}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P61201","model_url":"https://alphafold.ebi.ac.uk/files/AF-P61201-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P61201-F1-predicted_aligned_error_v6.png","plddt_mean":85.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CSN2","jax_strain_url":"https://www.jax.org/strain/search?query=CSN2"},"sequence":{"accession":"P61201","fasta_url":"https://rest.uniprot.org/uniprotkb/P61201.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P61201/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P61201"}},"corpus_meta":[{"pmid":"12972599","id":"PMC_12972599","title":"Disruption of the COP9 signalosome Csn2 subunit in mice causes deficient cell proliferation, accumulation of p53 and cyclin E, and early embryonic death.","date":"2003","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12972599","citation_count":117,"is_preprint":false},{"pmid":"17176258","id":"PMC_17176258","title":"The Aspergillus fumigatus metacaspases CasA and CasB facilitate growth under conditions of endoplasmic reticulum stress.","date":"2006","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/17176258","citation_count":72,"is_preprint":false},{"pmid":"20655450","id":"PMC_20655450","title":"Effects of beta-kappa-casein (CSN2-CSN3) haplotypes and beta-lactoglobulin (BLG) genotypes on milk production traits and detailed protein composition of individual milk of Simmental cows.","date":"2010","source":"Journal of dairy science","url":"https://pubmed.ncbi.nlm.nih.gov/20655450","citation_count":55,"is_preprint":false},{"pmid":"21697083","id":"PMC_21697083","title":"Crystal structure of clustered regularly interspaced short palindromic repeats (CRISPR)-associated Csn2 protein revealed Ca2+-dependent double-stranded DNA binding activity.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21697083","citation_count":44,"is_preprint":false},{"pmid":"20655451","id":"PMC_20655451","title":"Effects of beta-kappa-casein (CSN2-CSN3) haplotypes, beta-lactoglobulin (BLG) genotypes, and detailed protein composition on coagulation properties of individual milk of Simmental cows.","date":"2010","source":"Journal of dairy science","url":"https://pubmed.ncbi.nlm.nih.gov/20655451","citation_count":44,"is_preprint":false},{"pmid":"23625968","id":"PMC_23625968","title":"Double-strand DNA end-binding and sliding of the toroidal CRISPR-associated protein Csn2.","date":"2013","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/23625968","citation_count":41,"is_preprint":false},{"pmid":"10991940","id":"PMC_10991940","title":"Interaction between interferon consensus sequence-binding protein and COP9/signalosome subunit CSN2 (Trip15). 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sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34822630","citation_count":4,"is_preprint":false},{"pmid":"8565637","id":"PMC_8565637","title":"Assignment of the gene for beta-casein (CSN2) to 4q13 --> q21 in humans and 3p13 --> p12 in chimpanzees.","date":"1996","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8565637","citation_count":4,"is_preprint":false},{"pmid":"18832232","id":"PMC_18832232","title":"Technical note: detection of the C allele of beta-casein (CSN2) in Czech Dairy goat breeds using LightCycler analysis.","date":"2008","source":"Journal of dairy science","url":"https://pubmed.ncbi.nlm.nih.gov/18832232","citation_count":4,"is_preprint":false},{"pmid":"35235484","id":"PMC_35235484","title":"Detection of A2A2 genotype of beta casein protein (CSN2) gene in local, exotic and cross bred cattle in Pakistan.","date":"2022","source":"Animal biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/35235484","citation_count":3,"is_preprint":false},{"pmid":"36670778","id":"PMC_36670778","title":"A New AS-PCR Method to Detect CSN201 Allele, Genotyping at Ca-Sensitive Caseins Loci and Milk Traits Association Studies in Autochthonous Lazio Goats.","date":"2023","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/36670778","citation_count":3,"is_preprint":false},{"pmid":"21841082","id":"PMC_21841082","title":"Technical note: A novel method for routine genotyping of the G allele of β-casein (CSN2) and T allele of κ-casein (CSN3) in a sheep population using LightCycler.","date":"2011","source":"Journal of animal science","url":"https://pubmed.ncbi.nlm.nih.gov/21841082","citation_count":3,"is_preprint":false},{"pmid":"35400971","id":"PMC_35400971","title":"Single and combined effects of CSN1S1 and CSN2-casein genes on Awassi sheep milk quantity and quality.","date":"2022","source":"Veterinary world","url":"https://pubmed.ncbi.nlm.nih.gov/35400971","citation_count":2,"is_preprint":false},{"pmid":"40184159","id":"PMC_40184159","title":"Associations Between Polymorphisms of the CSN1S1, CSN1S2, CSN2 and CSN3 Genes and Milk Composition Traits in Holstein Cattle.","date":"2025","source":"Veterinary medicine and science","url":"https://pubmed.ncbi.nlm.nih.gov/40184159","citation_count":2,"is_preprint":false},{"pmid":"36773313","id":"PMC_36773313","title":"Comparative analysis of A1 and A2 allele detection efficiency for bovine CSN2 gene by AS-PCR methods.","date":"2023","source":"Acta biochimica Polonica","url":"https://pubmed.ncbi.nlm.nih.gov/36773313","citation_count":2,"is_preprint":false},{"pmid":"23176777","id":"PMC_23176777","title":"Activation of a casB gene encoding β-glucosidase of Pectobacterium carotovorum subsp. carotovorum LY34.","date":"2012","source":"Microbiological research","url":"https://pubmed.ncbi.nlm.nih.gov/23176777","citation_count":1,"is_preprint":false},{"pmid":"40703919","id":"PMC_40703919","title":"Differential A1/A2 β-casein (CSN2) gene-derived allelic and genotypic frequencies across Ecuadorian exotic dairy cattle breeds.","date":"2025","source":"Frontiers in veterinary science","url":"https://pubmed.ncbi.nlm.nih.gov/40703919","citation_count":1,"is_preprint":false},{"pmid":"31277514","id":"PMC_31277514","title":"Characterization of a Novel Porcine CSN2 Polymorphism and Its Distribution in Five European Breeds.","date":"2019","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/31277514","citation_count":1,"is_preprint":false},{"pmid":"33474893","id":"PMC_33474893","title":"[Transcriptomic Analysis of csn2 Gene Mutant Strains of Streptococcus mutans CRISPR-Cas9 System].","date":"2021","source":"Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition","url":"https://pubmed.ncbi.nlm.nih.gov/33474893","citation_count":0,"is_preprint":false},{"pmid":"35012254","id":"PMC_35012254","title":"[Effect of csn2 gene deficiency on the starvation tolerance and the synthesis of extracellular polysaccharides in oligotrophic environment of Streptococcus mutans].","date":"2022","source":"Zhonghua kou qiang yi xue za zhi = Zhonghua kouqiang yixue zazhi = Chinese journal of stomatology","url":"https://pubmed.ncbi.nlm.nih.gov/35012254","citation_count":0,"is_preprint":false},{"pmid":"41923857","id":"PMC_41923857","title":"Association study of the CSN2 gene with milk yield in the Sapera goat.","date":"2025","source":"Journal of advanced veterinary and animal research","url":"https://pubmed.ncbi.nlm.nih.gov/41923857","citation_count":0,"is_preprint":false},{"pmid":"42088988","id":"PMC_42088988","title":"An ARMS-integrated high-resolution melting assay for reliable discrimination of the A1/A2 polymorphism in the bovine CSN2 gene.","date":"2026","source":"Food chemistry. Molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/42088988","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.06.12.659315","title":"Structural Basis for Cas9-Directed Spacer Acquisition in Type II-A CRISPR-Cas Systems","date":"2025-06-12","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.12.659315","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.12.659244","title":"Structural insights into Cas9-mediated prespacer selection in CRISPR-Cas adaptation","date":"2025-06-12","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.12.659244","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":29160,"output_tokens":3180,"usd":0.06759,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9377,"output_tokens":2727,"usd":0.05753,"stage2_stop_reason":"end_turn"},"total_usd":0.12512,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking at the corpus, I need to identify which papers are about the canonical human/mammalian CSN2 gene (COP9 signalosome subunit 2, also known as CASB/Trip15/Cops2/Alien) versus other genes sharing the \"CSN2\" symbol.\n\n**Classification:**\n- Papers about **COP9 signalosome subunit CSN2** (mammalian): PMIDs 12972599, 10991940, 12426099, 12522100, 12524175, 28423737, 26942699\n- Papers about **CRISPR-associated Csn2** (prokaryotic, different protein): PMIDs 21697083, 23625968, 22753072, 22479393, 22531577, 26671707, bio_10.1101_2025.06.12.659315, bio_10.1101_2025.06.12.659244 — EXCLUDE (symbol collision, fundamentally different protein)\n- Papers about **bovine/goat/sheep beta-casein (CSN2/CASB)**: dairy science papers — These are about the milk protein gene, which is the HGNC alias CASB. However, these papers are about the milk protein itself (expression, variants, dairy traits), not about the COP9 signalosome. The HGNC alias \"CASB\" actually refers to beta-casein in livestock contexts, but in human genetics, CSN2 with HGNC alias CASB refers to the COP9 signalosome subunit 2. I need to check carefully.\n\nRe-examining: The HGNC gene CSN2 with alias CASB is the **COP9 signalosome subunit 2** in humans (COPS2). The bovine/dairy CSN2 gene (beta-casein) is a different gene. The alias \"CASB\" for bovine beta-casein is a livestock genetics naming convention, not the HGNC human gene alias. The corpus's HGNC alias \"CASB\" for this query refers to the human COPS2/CSN2. I will exclude dairy/livestock beta-casein papers.\n\n- Papers about **Aspergillus fumigatus metacaspases CasA/CasB**: PMID 17176258 — EXCLUDE (fungal metacaspase, different protein)\n- Papers about **fungal chitosanase Csn2**: PMID 18722595 — EXCLUDE\n- Papers about **bacterial CasB** (Type I-E CRISPR Cascade): PMID 23079036 — EXCLUDE\n- Papers about **Streptococcus mutans csn2** (CRISPR component): PMIDs 32794605, 33474893, 35012254 — EXCLUDE\n- Papers about **Pectobacterium casB** (beta-glucosidase): PMID 23176777 — EXCLUDE\n- CASB sequencing/forensics paper (PMID 33821571) — EXCLUDE (concanavalin A barcoding method, unrelated)\n- Papers about **sheep/goat gene mapping CASB**: PMIDs 1892247, 1503272 — livestock beta-casein, EXCLUDE\n- Papers about **human beta-casein CSN2 chromosomal mapping**: PMIDs 1577486, 8565637 — these are about human beta-casein (milk protein), not COP9 signalosome. EXCLUDE.\n\n**Included papers (COP9 signalosome CSN2/COPS2):** 12972599, 10991940, 12426099, 12522100, 12524175, 28423737, 26942699\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"Targeted disruption of Csn2 in mice disrupts the intact COP9 signalosome (CSN) complex, causes drastic accumulation of cyclin E (consistent with loss of SCF-ubiquitin-proteasome-mediated protein turnover), and elevates p53 and p21 levels, resulting in cell proliferation arrest in the inner cell mass and early embryonic lethality at the peri-implantation stage.\",\n      \"method\": \"Csn2 knockout mouse (targeted gene disruption); blastocyst outgrowth assay; Western blotting for cyclin E, p53, p21, and CSN complex integrity; Oct4 immunostaining\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean in vivo KO with multiple defined molecular phenotypes (complex disruption, cyclin E/p53 accumulation) replicated across several orthogonal readouts in a single rigorous study\",\n      \"pmids\": [\"12972599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CSN2 (Trip15) directly interacts with the interferon consensus sequence-binding protein ICSBP via its IRF association domain (IAD), and this association with the CSN complex leads to phosphorylation of ICSBP at a unique serine residue within its IAD; this phosphorylated residue is required for efficient ICSBP association with IRF-1 and for ICSBP-mediated transcriptional repression of IRF-1.\",\n      \"method\": \"Yeast two-hybrid screen (ICSBP-IAD bait vs. B-cell cDNA library); GST pull-down assay (in vitro); co-immunoprecipitation in COS7 cells; in vitro kinase assay (CSN-associated kinase phosphorylating ICSBP); site-directed mutagenesis of phosphorylation site\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding confirmed by Y2H + GST pulldown + co-IP; kinase assay with mutagenesis; multiple orthogonal methods in one study\",\n      \"pmids\": [\"10991940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Drosophila Rpn6, a non-ATPase subunit of the 19S regulatory particle lid complex of the 26S proteasome, physically interacts with Alien/CSN2 (the Drosophila ortholog of mammalian CSN2) via its PCI domain, as demonstrated by yeast two-hybrid analysis, and their expression patterns overlap during development.\",\n      \"method\": \"Yeast two-hybrid screen (Alien/CSN2 as bait); temporal/spatial expression pattern analysis by in situ hybridization and immunohistochemistry; genetic analysis of Rpn6 P-element insertion mutants\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Y2H interaction supported by overlapping expression patterns but no in vivo co-IP confirmation; interaction domain (PCI) identified\",\n      \"pmids\": [\"12426099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Trip15/CSN2 interacts with Nif3l1, a conserved transcriptional repressor; this interaction promotes nuclear translocation of Nif3l1 during retinoic acid-induced neural differentiation of P19 cells, and together they synergistically repress transcription. Trip15/CSN2 overexpression drives neuronal (but not glial) differentiation via downregulation of Oct-3/4 and induction of neurogenic genes Brn-2 and Mash-1.\",\n      \"method\": \"Yeast two-hybrid screen (Trip15/CSN2 as bait vs. P19 cDNA library); GST pull-down assay; epitope-tagged co-immunoprecipitation; immunofluorescence localization; luciferase reporter assay; sense/antisense mRNA overexpression in P19 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction confirmed by Y2H + pulldown + co-IP; functional consequence tested with reporter assay and gain/loss-of-function in differentiation model; multiple orthogonal methods\",\n      \"pmids\": [\"12522100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Trip15/CSN2 mRNA is induced at an early stage of neuronal differentiation in retinoic acid-treated P19 cells; enforced expression of Trip15/CSN2 is sufficient to convert P19 cells into neurons (but not glial cells) after aggregation without retinoic acid, accompanied by downregulation of Oct-3/4 and induction of neurogenic Brn-2 and Mash-1; antisense suppression of Trip15/CSN2 blocks commitment to neuronal lineage. In neonatal rat CNS, Trip15/CSN2 protein is localized to neuronal nuclei.\",\n      \"method\": \"Sense/antisense mRNA overexpression in P19 embryonal carcinoma cells; RT-PCR for marker genes (Oct-3/4, Brn-2, Mash-1); immunofluorescence localization in rat brain sections; in situ hybridization\",\n      \"journal\": \"Brain research. Developmental brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with defined molecular markers; nuclear localization confirmed by immunofluorescence; single lab, two complementary approaches\",\n      \"pmids\": [\"12524175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In hepatocellular carcinoma cells, RMP activates NF-κB, which directly promotes expression of CSN2 (COP9 signalosome subunit 2); elevated CSN2 represses degradation of Snail, a transcriptional repressor of E-cadherin, thereby facilitating epithelial-mesenchymal transition and metastasis.\",\n      \"method\": \"Overexpression/knockdown of RMP and CSN2 in HCC cell lines; migration/invasion assays; Western blotting for E-cadherin, Snail, p65, CSN2; reporter assays for NF-κB; pulmonary metastasis mouse model; immunohistochemistry of human HCC tissues\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway placement by epistasis (RMP→NF-κB→CSN2→Snail) supported by KD/OE with defined molecular readouts and in vivo validation; single lab\",\n      \"pmids\": [\"28423737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"DDA1 promotes colon cancer progression through activation of the NF-κB/CSN2/GSK-3β signaling pathway; DDA1-mediated NF-κB activation upregulates CSN2, which in turn modulates GSK-3β activity to promote cell cycle progression, invasion, and EMT.\",\n      \"method\": \"DDA1 overexpression/suppression in colon cancer cell lines; cell proliferation, apoptosis, invasion, and EMT assays; Western blotting for p65, CSN2, GSK-3β; in vivo tumor growth assay; immunohistochemistry of patient tissues\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established by gain/loss-of-function with defined molecular readouts (CSN2, GSK-3β) and in vivo validation; single lab\",\n      \"pmids\": [\"26942699\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CSN2 (COPS2/Trip15/Alien) encodes the second subunit of the COP9 signalosome (CSN), an eight-subunit complex that deconjugates Nedd8 from SCF cullin components to regulate SCF ubiquitin ligase activity and protein turnover (e.g., cyclin E, Snail); CSN2 also serves as a scaffold for CSN-associated kinase activities that phosphorylate substrates including ICSBP, thereby modulating transcription factor interactions, and plays a direct role in neuronal differentiation by promoting nuclear translocation of co-repressor Nif3l1 and downregulating Oct-3/4 to induce neurogenic gene expression; additionally, CSN2 is transcriptionally upregulated downstream of NF-κB in cancer contexts to suppress Snail and GSK-3β degradation, promoting EMT.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CSN2 (COPS2/Trip15/Alien) is an essential subunit of the COP9 signalosome (CSN) that controls protein turnover and transcriptional programs across embryonic development, differentiation, and cancer [#0, #3]. As a structural component of the intact CSN complex, CSN2 is required for SCF-cullin-dependent ubiquitin-proteasome degradation: its loss in mice disrupts the CSN, causes drastic accumulation of cyclin E and elevation of p53 and p21, arresting proliferation in the inner cell mass and producing peri-implantation lethality [#0]. Consistent with a link to the proteolytic machinery, the Drosophila ortholog Alien/CSN2 binds the 19S proteasome lid subunit Rpn6 through its PCI domain [#2]. CSN2 also scaffolds a CSN-associated kinase activity: it interacts directly with the transcription factor ICSBP via the IRF association domain and directs its phosphorylation, which is required for ICSBP-IRF-1 association and transcriptional repression [#1]. In neuronal differentiation, CSN2 promotes nuclear translocation of the co-repressor Nif3l1 and downregulates Oct-3/4 while inducing the neurogenic genes Brn-2 and Mash-1, and is itself sufficient to drive P19 cells toward a neuronal fate [#3, #4]. In cancer, CSN2 is transcriptionally induced downstream of NF-\\u03baB, where it stabilizes Snail and modulates GSK-3\\u03b2 to promote epithelial-mesenchymal transition and metastasis [#5, #6].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that CSN2 is not only a structural subunit but a docking platform coupling CSN-associated kinase activity to a transcription factor, defining a mechanism by which the complex regulates gene expression beyond proteolysis.\",\n      \"evidence\": \"Yeast two-hybrid, GST pull-down, co-IP in COS7, and in vitro kinase assay with phosphosite mutagenesis of ICSBP\",\n      \"pmids\": [\"10991940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The identity of the CSN-associated kinase that phosphorylates ICSBP is not resolved\",\n        \"Whether this kinase scaffolding occurs within the intact eight-subunit CSN or via free CSN2 is not addressed\"\n      ]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Linked CSN2 to the 26S proteasome by identifying a direct PCI-domain interaction with the 19S lid subunit Rpn6, suggesting physical coupling between the CSN and degradation machinery.\",\n      \"evidence\": \"Yeast two-hybrid with Alien/CSN2 bait and overlapping developmental expression analysis in Drosophila\",\n      \"pmids\": [\"12426099\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Y2H interaction lacks in vivo co-IP confirmation\",\n        \"Functional consequence of the CSN2-Rpn6 interaction was not tested\",\n        \"Conservation of the interaction in mammals not established\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated that CSN2 actively drives neuronal differentiation by partnering with the co-repressor Nif3l1 and reprogramming a transcriptional fate decision, extending CSN2 function into developmental gene control.\",\n      \"evidence\": \"Y2H, GST pull-down, co-IP, reporter assays, and gain/loss-of-function in retinoic-acid-treated P19 cells, plus neuronal nuclear localization in rat CNS\",\n      \"pmids\": [\"12522100\", \"12524175\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether neuronal differentiation requires the intact CSN or CSN2 alone is unresolved\",\n        \"Mechanism connecting Nif3l1 repression to Oct-3/4 downregulation is not defined\"\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Established CSN2's organismal essentiality and its mechanistic basis, showing the intact CSN is required to maintain SCF-driven turnover of cyclin E and proliferation control during early embryogenesis.\",\n      \"evidence\": \"Targeted Csn2 knockout mouse with blastocyst outgrowth assay and Western blotting for cyclin E, p53, p21, and CSN integrity\",\n      \"pmids\": [\"12972599\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct enzymatic role of CSN2 in cullin deneddylation not assayed\",\n        \"Which downstream phenotype (cyclin E vs p53/p21 accumulation) is causal for lethality not separated\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed CSN2 in an oncogenic signaling axis, showing it is induced downstream of NF-\\u03baB and stabilizes Snail to drive EMT and metastasis.\",\n      \"evidence\": \"RMP/CSN2 overexpression and knockdown in HCC cells, migration/invasion assays, NF-\\u03baB reporters, and a pulmonary metastasis mouse model\",\n      \"pmids\": [\"28423737\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which CSN2 represses Snail degradation not defined at the ligase level\",\n        \"Single-lab study without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Generalized the NF-\\u03baB/CSN2 axis to colon cancer, implicating CSN2 in modulation of GSK-3\\u03b2 to promote cell cycle progression, invasion, and EMT.\",\n      \"evidence\": \"DDA1 gain/loss-of-function in colon cancer cells with EMT/proliferation assays, Western blotting for p65/CSN2/GSK-3\\u03b2, and in vivo tumor growth\",\n      \"pmids\": [\"26942699\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical link between CSN2 and GSK-3\\u03b2 not demonstrated\",\n        \"Single-lab study without independent replication\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether CSN2 itself contributes catalytically to CSN deneddylase activity, versus serving purely as a structural and kinase-scaffolding subunit, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural model of CSN2 within the human CSN in the corpus\",\n        \"No direct assay of CSN2 contribution to cullin deneddylation\",\n        \"Identity of the CSN2-associated kinase remains unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [5, 6]}\n    ],\n    \"complexes\": [\n      \"COP9 signalosome\"\n    ],\n    \"partners\": [\n      \"ICSBP\",\n      \"Nif3l1\",\n      \"Rpn6\",\n      \"IRF-1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}