{"gene":"CUL5","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2003,"finding":"HIV-1 Vif interacts with CUL5, Elongin B/C, and Rbx1 to form an SCF-like E3 ubiquitin ligase complex that ubiquitinates and degrades APOBEC3G/CEM15. A Vif mutant that retained APOBEC3G binding but lost CUL5-SCF interaction was functionally inactive, establishing CUL5-SCF as required for Vif-mediated APOBEC3G degradation.","method":"Co-immunoprecipitation, ubiquitination assay, dominant-negative CUL5 mutants, Vif point mutants","journal":"Science","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, in vivo ubiquitination, loss-of-function mutants), replicated across multiple subsequent studies","pmids":["14564014"],"is_preprint":false},{"year":2004,"finding":"SOCS-box proteins (containing a BC box and downstream Cul5-box) specifically assemble with CUL5-Rbx2, whereas VHL-box proteins assemble with Cul2-Rbx1. Domain-swapping showed that the Cul5-box and Cul2-box sequences determine which Cullin-Rbx module is recruited. RNAi knockdown of Cul5-Rbx2 did not affect VHL-mediated HIF-2α degradation, confirming functional distinction.","method":"Co-immunoprecipitation, domain-swapping mutagenesis, RNAi knockdown","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, mutagenesis, and RNAi functional validation in single study; foundational work replicated in subsequent papers","pmids":["15601820"],"is_preprint":false},{"year":2004,"finding":"HIV-1 Vif contains a novel SOCS-box in which alanine replaces the consensus cysteine; this SOCS box mediates interaction with Elongin C, but two conserved Cys residues outside the SOCS box are additionally required for interaction with CUL5 (not Elongin C), establishing that selective CUL5 assembly requires protein interfaces beyond the SOCS-box–Elongin C interaction.","method":"Mutagenesis, co-immunoprecipitation, pulldown assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — site-directed mutagenesis with Co-IP validation; replicated/extended by subsequent structural and biochemical studies","pmids":["15574593"],"is_preprint":false},{"year":2004,"finding":"Vif recruits CUL5-EloB-EloC through a novel SOCS-box that binds EloC. Serine phosphorylation in the BC-box motif negatively regulates Vif binding to EloC. Vif itself is autoubiquitinated within the assembled Vif-CUL5 complex, analogous to F-box protein autoubiquitination within SCF complexes.","method":"Co-immunoprecipitation, in vitro and in vivo ubiquitination assays, phosphorylation analysis, mutagenesis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro ubiquitination assay plus mutagenesis and phosphorylation studies; multiple orthogonal methods","pmids":["15574592"],"is_preprint":false},{"year":2005,"finding":"HIV-1 Vif exploits the CUL5-E3 ligase to ubiquitinate and degrade both APOBEC3F and APOBEC3G. Depletion of CUL5 by RNAi or overexpression of dominant-negative CUL5 mutants blocked Vif-mediated suppression of APOBEC3F. Vif stability itself is also regulated by CUL5-E3 ligase, suggesting the viral substrate receptor is itself a CUL5 substrate.","method":"RNA interference, dominant-negative CUL5 mutants, co-immunoprecipitation, ubiquitination assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNAi and dominant-negative approaches with functional readouts; extends PMID 14564014 findings to APOBEC3F","pmids":["16014920"],"is_preprint":false},{"year":2006,"finding":"HIV-1 Vif is a zinc-binding protein containing an H-x(5)-C-x(17-18)-C-x(3-5)-H (HCCH) motif. Zinc coordination stabilizes a conserved hydrophobic interface within the HCCH motif critical for Vif-CUL5 E3 assembly. An N-terminal region of the first Cullin repeat of CUL5, dispensable for Elongin C binding, is required for Vif interaction, and this region is the most divergent between CUL2 and CUL5.","method":"Zinc-binding characterization, mutagenesis, co-immunoprecipitation, deletion analysis of CUL5","journal":"Virology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — zinc-binding biochemistry plus structure-function mutagenesis of both Vif and CUL5; multiple orthogonal approaches","pmids":["16530799"],"is_preprint":false},{"year":2001,"finding":"MUF1, a novel leucine-rich repeat BC-box protein purified from rat liver, assembles with CUL5 and Rbx1 to reconstitute ubiquitin ligase activity in vitro. Elongin A, SOCS1, and WSB1 were also shown to assemble with the CUL5/Rbx1 module to reconstitute potential E3 ligases.","method":"Protein purification from rat liver, in vitro reconstitution of ubiquitin ligase activity, biochemical assembly assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro reconstitution of ubiquitin ligase activity with purified components; foundational biochemical demonstration","pmids":["11384984"],"is_preprint":false},{"year":2008,"finding":"Structure-function studies of BC-box proteins define CUL5-box and CUL2-box sequences in detail. The spacing between BC-box and Cullin-box can vary widely (3 to ~80 amino acids). The LPPhiP motif conserved in most Cul5-boxes is also compatible with Cul2 interaction, indicating the motif alone does not determine Cullin specificity.","method":"Purification of BC-box proteins, structure-function mutagenesis, biochemical reconstitution of ubiquitin ligases","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution and systematic structure-function analysis in single thorough study","pmids":["18187417"],"is_preprint":false},{"year":2010,"finding":"HIV-1 Vif binds ElonginBC (EloBC) at two locations via an induced-folding mechanism: (1) the established BC-box binding to EloC, and (2) a novel interaction between the conserved Pro-Pro-Leu-Pro (PPLP) motif of Vif and the C-terminal domain of EloB. Both interactions are required for formation of a functional CUL5-containing ligase complex.","method":"Purified protein binding assays, isothermal titration calorimetry, NMR spectroscopy, cell-based functional assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1 / Strong — ITC and NMR with purified proteins plus cell-based validation; multiple orthogonal methods in single study","pmids":["20532212"],"is_preprint":false},{"year":2014,"finding":"Crystal structure of the Vif-CBF-β-CUL5-ELOB-ELOC pentameric complex revealed that Vif uses two domains to organize complex formation: an α/β domain binds CBF-β (competing with RUNX1), and an α-domain contacts both ELOC and CUL5 cooperatively, mimicking SOCS2 interactions. A unique zinc-finger motif of Vif stabilizes the α-domain conformation required for CUL5 interaction.","method":"X-ray crystallography (crystal structure), structural analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure of the pentameric complex providing atomic-level mechanistic detail","pmids":["24402281"],"is_preprint":false},{"year":2013,"finding":"Crystal structures of the ASB9-Elongin B/C ternary complex and the N-terminal domain of CUL5 reveal that ankyrin repeat SOCS-box proteins (ASBs) assemble with EloBC and CUL5 in a distinct architecture where the ankyrin domain is coaxial to the SOCS box-EloBC complex, positioning the substrate-binding site to face the E2-ubiquitin. The CUL5 structure showed a rigid-body rotation between Cullin repeats distinguishing it from other Cullins.","method":"X-ray crystallography, structural modeling of complete CUL5-based E3 ligase","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with structural validation; single study but rigorous structural method","pmids":["23806657"],"is_preprint":false},{"year":2021,"finding":"CUL5-RBX2-based E3 ligases partner with ARIH2 (RBR E3) for substrate ubiquitylation. CUL5-linked NEDD8 does not directly recruit ARIH2 (unlike CUL1-linked NEDD8 recruiting ARIH1); instead, NEDD8 allosterically rearranges CUL5 to expose cryptic ARIH2-binding sites, revealing a cullin-specific indirect allosteric activation mechanism.","method":"Cryo-EM structure, biochemical assembly assays, structural comparison with ARIH1-CUL1 complex","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures with biochemical validation; multiple orthogonal structural and biochemical approaches","pmids":["34518685"],"is_preprint":false},{"year":2021,"finding":"CUL5 neddylation allosterically exposes its ARIH2-binding site, promoting high-affinity ARIH2 binding, and simultaneously sequesters the NEDD8 E2 (UBE2F) binding site on RBX2. ASB9-CRL5 ubiquitylates its substrate CKB via the ASB9-CRL5-ARIH2-UBE2L3 complex; additional E2s (UBE2R1, UBE2D2) contribute to polyubiquitylation but do not alter ubiquitylation sites.","method":"In vitro ubiquitination assay, hydrogen-deuterium exchange mass spectrometry (HDX-MS), mass spectrometry analysis of ubiquitylation sites","journal":"Molecular & cellular proteomics","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstituted in vitro ubiquitination with HDX-MS allosteric mapping; multiple orthogonal biochemical methods","pmids":["33268465"],"is_preprint":false},{"year":2019,"finding":"CUL5, RNF7, and UBE2F form a CRL5 complex that proteasomally regulates levels of BH3-only pro-apoptotic proteins Bim and Noxa. Loss of CRL5 components re-sensitizes lung cancer cells to CDK9 and MCL1 inhibitors. Noxa accumulation upon CRL5 depletion is responsible for re-sensitization to CDK9 inhibitor.","method":"Genome-wide CRISPR screen (flow cytometry-based), genetic knockouts, protein level analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide CRISPR screen with functional validation of specific substrates (Noxa, Bim) via KO; multiple orthogonal methods","pmids":["31294695"],"is_preprint":false},{"year":2019,"finding":"CUL5-ASB11 is an E3 ubiquitin ligase that ubiquitinates BIK (pro-apoptotic BH3-only protein) for proteasomal degradation. During ER stress, XBP1s activates ASB11, promoting BIK ubiquitination and interaction with p97/VCP, enabling ER stress adaptation (cell survival). Genotoxic agents down-regulate the IRE1α-XBP1s-ASB11 axis, stabilizing BIK and promoting apoptosis.","method":"Co-immunoprecipitation, ubiquitination assay, knockdown/knockout experiments, cell death assays, IRE1α inhibitor treatment","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — identification of substrate (BIK), E3 complex (CUL5-ASB11), and upstream regulation (XBP1s) with multiple functional readouts","pmids":["31387940"],"is_preprint":false},{"year":2022,"finding":"The Rab40b/CUL5 complex ubiquitylates the small GTPase Rap2. This ubiquitylation regulates Rap2 activation state and its recycling from the endolysosomal compartment to the lamellipodia of migrating breast cancer cells, controlling Rap2-dependent actin dynamics at the leading edge required for cell migration and invasion.","method":"Co-immunoprecipitation, ubiquitination assay, live-cell imaging, loss-of-function experiments, cell migration/invasion assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — substrate identification (Rap2), ubiquitination assay, localization imaging, and functional migration readout; multiple orthogonal methods","pmids":["35293963"],"is_preprint":false},{"year":2022,"finding":"CUL5 determines CD4+ T cell fate between T helper and T regulatory cells by regulating IL-4 receptor signaling. Upon T cell activation, CUL5 forms a complex with CIS (SOCS-box protein) and phospho-Jak1 (pJak1). CUL5 deletion reduces ubiquitination and degradation of pJak1, elevating pJak1 and pSTAT6 levels and lowering the threshold for IL-4 receptor signaling, diverting cells from Treg to Th9 fate.","method":"Conditional knockout mice (Cul5 fl/fl x CD4-Cre), co-immunoprecipitation of CUL5-CIS-pJak1 complex, Western blot for pJak1/pSTAT6, T cell differentiation assays, in vivo asthma model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with defined molecular mechanism (CUL5-CIS-pJak1 complex, substrate pJak1), multiple orthogonal methods, in vivo phenotype","pmids":["35589717"],"is_preprint":false},{"year":2024,"finding":"CUL5 is a negative regulator of TCR and cytokine (IL-2) signaling in CD8+ T cells. CUL5 is upregulated by TCR stimulation and interacts with SOCS-box-containing protein PCMTD2 to inhibit signaling. CUL5 knockout enhances CD8+ T cell anti-tumor activity. Neddylation inhibition (MLN4924), which blocks CUL5 activation, similarly enhances CD8+ effector activities with CUL5 validated as a major target.","method":"CRISPR-based stepwise screening, CUL5 knockout in mouse CD8+ T cells, proteomics, co-immunoprecipitation (CUL5-PCMTD2), neddylation inhibitor (MLN4924), tumor growth assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR screen with mechanistic follow-up (Co-IP, proteomics, chemical inhibition), in vivo tumor model; multiple orthogonal methods","pmids":["38242867"],"is_preprint":false},{"year":2020,"finding":"The CUL5-type ubiquitin ligase KLHDC1 targets truncated SELENOS (a selenoprotein lacking selenocysteine due to failed UGA/Sec decoding) for proteasomal degradation. KLHDC1 knockdown in U2OS cells decreased ER stress-induced cell death and increased the population with lower ROS levels.","method":"Protein interaction assays, knockdown experiments, flow cytometry for ROS/cell death, proteasome inhibition assays","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — substrate identification (truncated SELENOS) with functional knockdown phenotype; single lab, methods partially inferred from abstract","pmids":["32200094"],"is_preprint":false},{"year":2021,"finding":"CUL5-ASB6 complex acts as an E3 ubiquitin ligase mediating p62/SQSTM1 ubiquitination and proteasomal degradation. Depletion of CUL5 or ASB6 induced p62 accumulation; ASB6 overexpression promoted p62 ubiquitination and degradation, inhibited cell proliferation, and impaired autophagy.","method":"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, overexpression, cell proliferation and autophagy assays","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — substrate identification (p62) with ubiquitination assay and functional readouts; single lab","pmids":["34164402"],"is_preprint":false},{"year":2020,"finding":"Gossypol inhibits CUL5 neddylation by directly binding to the SAG-CUL5 complex (with CUL5-H572 playing a key role in gossypol binding), blocking CUL5 E3 ligase activation and causing accumulation of NOXA (a CUL5 substrate) in cancer cells.","method":"AlphaScreen high-throughput in vitro neddylation assay, biochemical binding studies, compound library screen, cellular substrate accumulation assays","journal":"Neoplasia","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro neddylation assay with direct binding evidence and mutagenesis of key binding residue (H572); single lab","pmids":["32145688"],"is_preprint":false},{"year":2009,"finding":"PKA-dependent phosphorylation of VACM-1/CUL5 at Ser730 controls its neddylation status. Mutation S730A increases NEDD8 modification of CUL5 and is associated with increased cellular growth. Induction of PKA activity with forskolin reduced NEDD8 modification of CUL5. PKC activity further promotes growth in S730A-CUL5 cells.","method":"Site-directed mutagenesis, Western blot with phospho-specific and NEDD8 antibodies, immunoprecipitation, cell growth assays, PKA/PKC agonists/inhibitors","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with biochemical readout of neddylation and growth; multiple methods but single lab","pmids":["19917606"],"is_preprint":false},{"year":2000,"finding":"VACM-1/CUL5 expression inhibits basal and stimulated cAMP production in a PKA-dependent manner. Mutation at the PKA phosphorylation site (S730A) reverses the inhibitory effect on cAMP. VACM-1 expression also stimulates inositol 1,4,5-trisphosphate (IP3) production in response to AVP, establishing CUL5 as a regulator of cAMP and calcium signaling pathways.","method":"Stable cell line overexpression, cAMP assays, IP3 assays, PKA/PKC inhibitor treatments, site-directed mutagenesis","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple signaling readouts with pharmacological and mutagenesis validation; single lab","pmids":["10898738"],"is_preprint":false},{"year":2025,"finding":"In hematopoietic stem cells, CUL5 forms a complex with LRRC41 (identified by reciprocal Co-IP), and CUL5 regulates STAT5 and LRRC41 protein levels during IL-3 stimulation. Mice lacking CUL5 in hematopoietic cells (Cul5Vav-Cre) accumulate LRRC41 and STAT5 during IL-3 stimulation, display myeloid/megakaryocyte-biased differentiation, increased HSC proliferation, and reduced CXCR4 surface expression. JAK1/2 inhibition (ruxolitinib) normalizes hematopoiesis.","method":"Conditional knockout mice (Cul5Vav-Cre), reciprocal co-immunoprecipitation (CUL5-LRRC41), whole-cell proteomics, cytokine stimulation assays, flow cytometry, ruxolitinib rescue","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with defined substrates/binding partners (LRRC41, STAT5), reciprocal Co-IP, proteomics, and pharmacological rescue; multiple orthogonal methods","pmids":["40569692"],"is_preprint":false},{"year":2016,"finding":"A nuclear localization signal (NLS: 640PKLKRQ646) in VACM-1/CUL5 is required for its nuclear translocation and antiproliferative effect. Mutation of Lys642 and Lys644 to Gly significantly reduced nuclear localization and compromised the growth-inhibitory effect. The NLS also controls the proliferative phenotype and nuclear NEDD8 signal of the S730A-CUL5 mutant.","method":"Site-directed mutagenesis, immunocytochemistry, cell growth assays, Western blot for neddylation","journal":"Cell and tissue research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — mutagenesis with localization and functional readout; single lab, localization linked to growth phenotype","pmids":["27834018"],"is_preprint":false},{"year":2012,"finding":"VACM-1/CUL5 expression in vitro reduces aquaporin-1 (AQP1) protein levels (~6-fold) in COS-1 cells. In vivo, water deprivation increases CUL5 NEDD8 modification in vascular tissue, and AQP1 levels are inversely correlated with the ratio of neddylated to total VACM-1/CUL5, suggesting CUL5 regulates endothelial AQP1 concentration.","method":"Microarray, transfection with VACM-1 cDNA, Western blot, immunocytochemistry, in vivo water deprivation model","journal":"Cell and tissue research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — correlation-based in vivo evidence and single overexpression experiment in vitro; no direct ubiquitination assay for AQP1","pmids":["22581383"],"is_preprint":false},{"year":2012,"finding":"VACM-1/CUL5 expression decreases AQP2 protein concentration in MDCK cells stably expressing AQP2 and in COS-1 cells co-transfected with AQP2 and VACM-1 cDNAs. In water-deprived rat kidneys, decreased CUL5 protein correlates with increased AQP2 levels in collecting duct.","method":"Overexpression/co-transfection, Western blot, immunocytochemistry, in vivo water deprivation","journal":"Cellular physiology and biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — overexpression phenotype with correlative in vivo data; no direct ubiquitination or mechanistic assay for AQP2; single lab","pmids":["23171819"],"is_preprint":false},{"year":2010,"finding":"In Drosophila oogenesis, reduced CUL-5 activity causes aberrant follicle formation with excess germ cells, overproliferation of germ line cells, defective cyst encapsulation, and germ cell depletion. These phenotypes are enhanced by reduced activity of gustavus (a SOCS-box-containing substrate receptor of CUL5-based E3 ligases), establishing CUL5/Gus E3 complexes as required for germ cell proliferation, maintenance, and follicular morphogenesis.","method":"Drosophila genetics (cul-5 loss-of-function mutants, gustavus mutants, genetic epistasis), histology, immunofluorescence","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in Drosophila ortholog with defined cellular phenotypes; functional relevance supported by SOCS-box enhancer interaction","pmids":["20140218"],"is_preprint":false},{"year":2010,"finding":"In zebrafish, d-Asb11 requires its CUL5-box domain to function as part of a CUL5-based E3 ligase. Zebrafish mutants lacking the Asb11 Cul5-box fail to degrade the Notch ligand DeltaA, impair Notch target gene expression, and show defective cell fate specification in neurogenic regions, demonstrating that the CUL5-box is required for Notch signaling and neurogenesis in vivo.","method":"Zebrafish genetics (Cul5-box mutant), Notch reporter assays, immunostaining for DeltaA, RNA injection rescue experiments","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo zebrafish mutant with defined molecular substrate (DeltaA) and signaling pathway (Notch); single study","pmids":["21124961"],"is_preprint":false},{"year":2025,"finding":"ASB9-CRL5 ubiquitylates histones H3 and H4 (but not H2A or H2B) via K48 and K63 polyubiquitin chains, targeting free histones for degradation. Neddylated ASB9-CRL5 binds histones with highest affinity via electrostatic interactions. Histones in nucleosomes or bound to chaperone Asf1 are not ubiquitylated. This CUL5-mediated ubiquitylation does not require the RING-between-RING helper ligase ARIH2, representing the first example of ARIH2-independent CUL5-mediated ubiquitylation.","method":"In vitro ubiquitination reconstitution, mass spectrometry for ubiquitylation sites and chain types, binding experiments, neddylated vs. unneddylated complex comparison","journal":"Molecular & cellular proteomics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified components, MS-based site mapping, multiple substrate conditions tested; single lab but multiple orthogonal methods","pmids":["41260500"],"is_preprint":false},{"year":2025,"finding":"The E3 ligase Cul5-Wsb2 uses BCL2 family proteins (Bcl-xl, Bcl-w, Bcl2 — but not Mcl1) as co-receptors to target Bim for ubiquitination and degradation. Wsb2 recognizes Bcl-xl through a conserved motif; disruption of this interaction prevents Wsb2 binding to the Bcl-xl/Bim dimer and blocks Bim degradation. Wsb2 contacts the Mcl1/Bim dimer through a separate Wsb2 interface.","method":"Co-immunoprecipitation, mutagenesis of Bcl-xl and Wsb2, ubiquitination assays, knockdown cell viability assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with mutagenesis, ubiquitination assay, and cell viability functional readout; preprint, single lab","pmids":["40832228"],"is_preprint":true},{"year":2021,"finding":"CUL5 interacts with NAMPT (Visfatin) as shown by co-immunoprecipitation, and CUL5 promotes NAMPT degradation. CUL5 overexpression in H2O2-stimulated human coronary artery endothelial cells reduces phosphorylation of p38 and Akt and decreases VEGF and MMP2 protein levels, inhibiting angiogenic functions.","method":"Co-immunoprecipitation, overexpression, Western blot for pAkt/p38/VEGF/MMP2, cell viability/migration/tube formation assays","journal":"Journal of cardiovascular pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP for substrate identification, no direct ubiquitination assay; single lab","pmids":["34596622"],"is_preprint":false},{"year":2026,"finding":"CUL5 loss in bladder cancer cells reduces ubiquitination of PTBP1. Loss of PTBP1 ubiquitination alters alternative splicing of RUBCN pre-mRNA, increasing the RUBCN-S isoform, which inhibits autophagy and thereby prevents immune evasion from CD8+ T cell-mediated killing.","method":"Genome-wide CRISPR-Cas9 screen under CD8+ T cell pressure, ubiquitination assay, alternative splicing analysis, in vivo xenograft with anti-PD-1 combination","journal":"PLoS biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen with mechanistic follow-up (ubiquitination assay, splicing analysis); single lab","pmids":["41662369"],"is_preprint":false},{"year":2026,"finding":"CUL5 neddylation at Lys724 is critical for its antiproliferative effect; K724R mutation converts CUL5 from a growth inhibitor to a growth promoter in endothelial and cancer cells. Multi-site neddylation (at K724, K727, K728) contributes to CUL5's regulatory effects. In T47D cells, MAPK phosphorylation and ERα expression are directly correlated with CUL5 neddylation status.","method":"Site-directed mutagenesis of neddylation sites, cell proliferation assays, Western blot, MLN4924 neddylation inhibitor, immunoprecipitation","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic mutagenesis of neddylation sites with functional proliferation and signaling readouts; single lab","pmids":["41797611"],"is_preprint":false}],"current_model":"CUL5 is the scaffold subunit of the Cullin-RING Ligase 5 (CRL5) complex, which assembles with RBX2, Elongin B/C, and SOCS-box-containing substrate receptors (including SOCS proteins, ASB proteins, and viral hijackers like HIV-1 Vif) to form E3 ubiquitin ligases that ubiquitinate and proteasomally degrade diverse substrates—including APOBEC3G/F, Rap2, BIK, p62, Noxa, Bim, STAT5, pJak1, PTBP1, and free histones H3/H4; CRL5 activity requires NEDD8-dependent neddylation of CUL5 (at Lys724 and other sites), which allosterically exposes the binding site for the co-E3 ARIH2 (though some substrates are ubiquitylated ARIH2-independently); and CUL5 controls key cellular processes including antiviral defense, T cell fate decisions, hematopoietic stem cell homeostasis, cell cycle progression, apoptosis, cell migration, and angiogenesis."},"narrative":{"mechanistic_narrative":"CUL5 is the scaffold subunit of Cullin-RING E3 ubiquitin ligase complexes (CRL5) that target diverse substrates for proteasomal degradation, thereby controlling antiviral defense, apoptosis, T cell and hematopoietic cell fate, cell migration, and proliferation [PMID:14564014, PMID:11384984, PMID:35589717]. CUL5 assembles with RBX2/RNF7 and the Elongin B/C adaptor module, which docks SOCS-box-containing substrate receptors via a BC-box, while a distinct Cul5-box determines selective CUL5 (versus CUL2) recruitment [PMID:15601820, PMID:11384984, PMID:18187417]. Through this architecture CUL5 partners with a broad family of substrate receptors—including ASB proteins (ASB9, ASB11, ASB6), CIS, WSB2, KLHDC1, gustavus, Rab40b, PCMTD2, and LRRC41—each delivering specific substrates such as creatine kinase, the pro-apoptotic BH3-only proteins BIK, Bim, and Noxa, p62/SQSTM1, truncated SELENOS, the GTPase Rap2, phospho-Jak1, STAT5, and PTBP1 [PMID:23806657, PMID:31294695, PMID:31387940, PMID:35293963, PMID:35589717, PMID:32200094, PMID:34164402, PMID:40569692, PMID:40832228]. CRL5 activity is gated by NEDD8 conjugation of CUL5 (at Lys724 and additional sites), which allosterically remodels CUL5 to expose a cryptic binding site for the co-E3 ARIH2 while sequestering the NEDD8 E2 UBE2F site on RBX2, although some substrates such as free histones H3/H4 are ubiquitylated ARIH2-independently [PMID:34518685, PMID:33268465, PMID:41260500, PMID:41797611]. HIV-1 Vif hijacks this machinery as a SOCS-box mimic, using a zinc-coordinated HCCH motif, CBF-β binding, and cooperative ELOC/CUL5 contacts to reconstitute a CRL5 that degrades the antiviral cytidine deaminases APOBEC3G and APOBEC3F [PMID:14564014, PMID:16014920, PMID:16530799, PMID:24402281]. CUL5 substrate selection is exploited physiologically to set signaling thresholds: CRL5-CIS degrades phospho-Jak1 to bias CD4+ T cell fate, CRL5 restrains TCR/IL-2 signaling in CD8+ T cells via PCMTD2, and CRL5-LRRC41 limits STAT5 to maintain hematopoietic stem cell homeostasis [PMID:35589717, PMID:38242867, PMID:40569692].","teleology":[{"year":2001,"claim":"Established that CUL5 is a functional E3 ligase scaffold, answering whether it could nucleate ubiquitin ligase activity with substrate receptors.","evidence":"In vitro reconstitution of ubiquitin ligase activity from CUL5/Rbx1 with purified BC-box proteins (MUF1, Elongin A, SOCS1, WSB1) from rat liver","pmids":["11384984"],"confidence":"High","gaps":["Did not define which physiological substrates are targeted","Did not establish CUL5-versus-CUL2 specificity determinants"]},{"year":2003,"claim":"Showed that HIV-1 Vif coopts a CUL5-Elongin B/C-Rbx1 ligase to degrade APOBEC3G, defining the first biologically critical CRL5 substrate axis.","evidence":"Co-IP, in vivo ubiquitination, dominant-negative CUL5 and Vif point mutants","pmids":["14564014"],"confidence":"High","gaps":["Atomic basis of Vif-CUL5 selectivity unresolved","Did not address host substrate receptors"]},{"year":2004,"claim":"Defined the molecular code for CUL5-specific receptor recruitment, distinguishing CRL5 from CRL2 assembly.","evidence":"Reciprocal Co-IP, domain-swapping mutagenesis, and RNAi separating Cul5-box/SOCS-box from VHL-box/Cul2-box; characterization of Vif's atypical SOCS box and additional Cys-dependent CUL5 contacts and autoubiquitination","pmids":["15601820","15574593","15574592"],"confidence":"High","gaps":["LPPhiP motif alone does not fully dictate Cullin choice","Structural mechanism of selectivity not yet visualized"]},{"year":2006,"claim":"Pinpointed the zinc-coordinated HCCH motif of Vif and the divergent N-terminal CUL5 region as the basis of selective viral CRL5 assembly.","evidence":"Zinc-binding biochemistry, mutagenesis, and CUL5 deletion analysis with Co-IP","pmids":["16530799"],"confidence":"High","gaps":["Mechanism extended to APOBEC3F via RNAi/dominant-negative but degradation kinetics not resolved [#16014920]"]},{"year":2008,"claim":"Systematically defined how BC-box-to-Cullin-box spacing and motif variation govern receptor assembly across the BC-box protein family.","evidence":"Purification of BC-box proteins with structure-function mutagenesis and in vitro ligase reconstitution","pmids":["18187417"],"confidence":"High","gaps":["Did not assign specific physiological substrates to each receptor"]},{"year":2014,"claim":"Provided atomic-level visualization of the Vif-CBF-β-CUL5-ELOB-ELOC pentamer, explaining cooperative ELOC/CUL5 engagement and SOCS2 mimicry.","evidence":"X-ray crystallography of the pentameric complex; complemented by earlier ITC/NMR mapping of dual EloBC contacts and ASB9/CUL5 structural architecture","pmids":["24402281","20532212","23806657"],"confidence":"High","gaps":["Did not capture the neddylated, catalytically active state","Substrate positioning relative to E2 inferred, not directly observed"]},{"year":2021,"claim":"Resolved how NEDD8 activates CRL5, establishing a cullin-specific allosteric mechanism distinct from CRL1.","evidence":"Cryo-EM, HDX-MS, and reconstituted ubiquitination showing NEDD8 allosterically exposes the ARIH2 site and sequesters the UBE2F site on RBX2; ASB9-CRL5-ARIH2-UBE2L3 ubiquitylates CKB","pmids":["34518685","33268465"],"confidence":"High","gaps":["Did not establish which substrates strictly require ARIH2 versus act independently"]},{"year":2022,"claim":"Demonstrated CRL5 as a tunable rheostat for immune-cell signaling and cytoskeletal control through receptor-specific substrate choice.","evidence":"Conditional Cul5 knockout mice and Co-IP defining CRL5-CIS-pJak1 control of CD4+ T cell fate; ubiquitination/imaging defining Rab40b-CUL5 control of Rap2 and migration","pmids":["35589717","35293963"],"confidence":"High","gaps":["In vivo substrate specificity for additional receptors not mapped","Direct ubiquitination kinetics in primary cells not resolved"]},{"year":2024,"claim":"Established CUL5 as a brake on CD8+ T cell anti-tumor activity, linking neddylation-dependent CRL5 activity to immunotherapy.","evidence":"CRISPR screening, CUL5 knockout, proteomics, CUL5-PCMTD2 Co-IP, MLN4924 treatment, and tumor models","pmids":["38242867"],"confidence":"High","gaps":["Direct PCMTD2 substrate(s) not fully enumerated","Relationship to other CRL5 immune substrates unclear"]},{"year":2025,"claim":"Extended CRL5 substrate scope to hematopoietic homeostasis and to ARIH2-independent ubiquitylation of free histones.","evidence":"Conditional Cul5 knockout mice with reciprocal CUL5-LRRC41 Co-IP and proteomics linking CUL5 to STAT5/LRRC41; in vitro reconstitution and MS showing neddylated ASB9-CRL5 ubiquitylates free H3/H4 ARIH2-independently","pmids":["40569692","41260500"],"confidence":"High","gaps":["Whether LRRC41 is a direct substrate or co-receptor not fully resolved","Cellular consequences of free-histone ubiquitylation not established in vivo"]},{"year":2026,"claim":"Connected CRL5 substrate control to mRNA splicing, autophagy, and tumor immune evasion, and refined the neddylation sites governing its growth-regulatory output.","evidence":"CRISPR screen under CD8+ T cell pressure with PTBP1 ubiquitination and RUBCN splicing analysis; site-directed mutagenesis showing Lys724/K727/K728 neddylation dictates antiproliferative activity","pmids":["41662369","41797611"],"confidence":"Medium","gaps":["PTBP1 receptor not identified","Mechanistic link between neddylation site occupancy and substrate selection incompletely defined"]},{"year":null,"claim":"It remains unresolved how individual SOCS-box receptors and upstream signals are coordinated to select among the large CRL5 substrate repertoire in a given cell type, and how non-canonical CUL5 signaling functions (cAMP/IP3 modulation, nuclear localization) integrate with its ligase activity.","evidence":"Not established in the available corpus","pmids":[],"confidence":"Low","gaps":["No unified model linking receptor abundance to substrate prioritization","Mechanism of reported nuclear/signaling roles not connected to E3 activity"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,6,14,15]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,12,29]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,6,7,11]},{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[11,12,33]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[24]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,16,17]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[13,14,30]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[16,23]}],"complexes":["CRL5 (CUL5-RBX2/RNF7-Elongin B/C E3 ubiquitin ligase)","Vif-CBF-β-CUL5-ELOB-ELOC complex","ASB9-CRL5-ARIH2 ligase"],"partners":["RBX2/RNF7","ELONGIN B/C","ARIH2","UBE2F","ASB9","ASB11","CIS","LRRC41"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q93034","full_name":"Cullin-5","aliases":["Vasopressin-activated calcium-mobilizing receptor 1","VACM-1"],"length_aa":780,"mass_kda":91.0,"function":"Core component of multiple cullin-5-RING E3 ubiquitin-protein ligase complexes (ECS complexes, also named CRL5 complexes), which mediate the ubiquitination and subsequent proteasomal degradation of target proteins (PubMed:11384984, PubMed:15601820, PubMed:21199876, PubMed:21980433, PubMed:23897481, PubMed:25505247, PubMed:27910872, PubMed:32200094, PubMed:33268465, PubMed:35512830, PubMed:38418882). Acts a scaffold protein that contributes to catalysis through positioning of the substrate and the ubiquitin-conjugating enzyme (PubMed:11384984, PubMed:15601820, PubMed:33268465). The functional specificity of the E3 ubiquitin-protein ligase complex depends on the variable SOCS box-containing substrate recognition component (PubMed:11384984, PubMed:15601820, PubMed:33268465). Acts as a key regulator of neuron positioning during cortex development: component of various SOCS-containing ECS complexes, such as the ECS(SOCS7) complex, that regulate reelin signaling by mediating ubiquitination and degradation of DAB1 (By similarity). ECS(SOCS1) seems to direct ubiquitination of JAK2 (PubMed:11384984). The ECS(SOCS2) complex mediates the ubiquitination and subsequent proteasomal degradation of phosphorylated EPOR and GHR (PubMed:21980433, PubMed:25505247). The ECS(SPSB3) complex catalyzes ubiquitination of nuclear CGAS (PubMed:38418882). ECS(KLHDC1) complex is part of the DesCEND (destruction via C-end degrons) pathway and mediates ubiquitination and degradation of truncated SELENOS selenoprotein produced by failed UGA/Sec decoding, which ends with a glycine (PubMed:32200094). The ECS(ASB9) complex mediates ubiquitination and degradation of CKB (PubMed:33268465). As part of some ECS complex, promotes 'Lys-11'-linked ubiquitination and degradation of BTRC (PubMed:27910872). As part of a multisubunit ECS complex, polyubiquitinates monoubiquitinated POLR2A (PubMed:19920177). As part of the ECS(RAB40C) complex, mediates ANKRD28 ubiquitination and degradation, thereby inhibiting protein phosphatase 6 (PP6) complex activity and focal adhesion assembly during cell migration (PubMed:35512830). As part of the ECS(RAB40A) complex, mediates RHOU 'Lys-48'-linked ubiquitination and degradation, thus inhibiting focal adhesion disassembly during cell migration (PubMed:26598620). As part of the ECS(RAB40B) complex, mediates LIMA1/EPLIN and RAP2 ubiquitination, thereby regulating actin cytoskeleton dynamics and stress fiber formation during cell migration (PubMed:33999101, PubMed:35293963). The ECS(ASB7) complex acts a negative regulator of H3K9me3 histone mark by mediating ubiquitination and degradation of SUV39H1 (PubMed:40440427). May form a cell surface vasopressin receptor (PubMed:9037604) (Microbial infection) Following infection by HIV-1 virus, CUL5 associates with HIV-1 Vif proteins and forms a cullin-5-RING E3 ubiquitin-protein ligase complex (ECS complex) that catalyzes ubiquitination and degradation of APOBEC3F and APOBEC3G (PubMed:16636053, PubMed:22190037). The complex can also ubiquitinate APOBEC3H to some extent (PubMed:37640699) (Microbial infection) Seems to be involved in proteasomal degradation of p53/TP53 stimulated by adenovirus E1B-55 kDa protein","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q93034/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CUL5","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CUL5","total_profiled":1310},"omim":[{"mim_id":"621134","title":"ANKYRIN REPEAT- AND SOCS BOX-CONTAINING PROTEIN 18; ASB18","url":"https://www.omim.org/entry/621134"},{"mim_id":"620091","title":"PROTEIN-L-ISOASPARTATE (D-ASPARTATE) O-METHYLTRANSFERASE DOMAIN-CONTAINING PROTEIN 1; PCMTD1","url":"https://www.omim.org/entry/620091"},{"mim_id":"620077","title":"PROTEIN-L-ISOASPARTATE (D-ASPARTATE) O-METHYLTRANSFERASE DOMAIN-CONTAINING PROTEIN 2; PCMTD2","url":"https://www.omim.org/entry/620077"},{"mim_id":"618753","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 41; LRRC41","url":"https://www.omim.org/entry/618753"},{"mim_id":"617700","title":"UBIQUITIN-CONJUGATING ENZYME E2 F; UBE2F","url":"https://www.omim.org/entry/617700"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CUL5"},"hgnc":{"alias_symbol":["VACM-1"],"prev_symbol":[]},"alphafold":{"accession":"Q93034","domains":[{"cath_id":"1.20.1310.10","chopping":"14-150","consensus_level":"high","plddt":85.7661,"start":14,"end":150},{"cath_id":"1.20.1310.10","chopping":"203-304","consensus_level":"medium","plddt":94.5267,"start":203,"end":304},{"cath_id":"1.20.1310.10","chopping":"312-486","consensus_level":"medium","plddt":88.2033,"start":312,"end":486},{"cath_id":"-","chopping":"496-557","consensus_level":"high","plddt":86.136,"start":496,"end":557},{"cath_id":"3.30.230.130","chopping":"575-693","consensus_level":"high","plddt":90.8181,"start":575,"end":693},{"cath_id":"1.10.10.10","chopping":"697-777","consensus_level":"high","plddt":90.6531,"start":697,"end":777}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q93034","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q93034-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q93034-F1-predicted_aligned_error_v6.png","plddt_mean":89.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CUL5","jax_strain_url":"https://www.jax.org/strain/search?query=CUL5"},"sequence":{"accession":"Q93034","fasta_url":"https://rest.uniprot.org/uniprotkb/Q93034.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q93034/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q93034"}},"corpus_meta":[{"pmid":"14564014","id":"PMC_14564014","title":"Induction 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ubiquitin ligase Cul5 regulates hematopoietic stem cell function for steady-state hematopoiesis in mice.","date":"2025","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/40569692","citation_count":5,"is_preprint":false},{"pmid":"30269386","id":"PMC_30269386","title":"Comparative Analysis of cul5 and rbx2 Expression in the Developing and Adult Murine Brain and Their Essentiality During Mouse Embryogenesis.","date":"2018","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/30269386","citation_count":5,"is_preprint":false},{"pmid":"16581022","id":"PMC_16581022","title":"Truncated form of VACM-1/cul-5 with an extended 3' untranslated region stimulates cell growth via a MAPK-dependent pathway.","date":"2006","source":"Biochemical and biophysical research 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Lett. 322 (2012) 148-158].","date":"2021","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/34274168","citation_count":1,"is_preprint":false},{"pmid":"42064089","id":"PMC_42064089","title":"Cul5: immune cell function and therapeutic potential.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/42064089","citation_count":0,"is_preprint":false},{"pmid":"42078440","id":"PMC_42078440","title":"CUL5-mediated ubiquitination in cancer cell therapy: context-dependent roles, molecular networks, and emerging therapeutic avenues.","date":"2026","source":"Frontiers in medicine","url":"https://pubmed.ncbi.nlm.nih.gov/42078440","citation_count":0,"is_preprint":false},{"pmid":"40832228","id":"PMC_40832228","title":"Cul5Wsb2 uses BCL2 proteins as co-receptors to target Bim for degradation.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40832228","citation_count":0,"is_preprint":false},{"pmid":"40501794","id":"PMC_40501794","title":"The Mechanism of Histone Ubiquitylation by the ASB9-CUL5 Ubiquitin Ligase.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40501794","citation_count":0,"is_preprint":false},{"pmid":"38740386","id":"PMC_38740386","title":"Selection and characterization of aptamers targeting the Vif-CBFβ-ELOB-ELOC-CUL5 complex.","date":"2024","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38740386","citation_count":0,"is_preprint":false},{"pmid":"41797611","id":"PMC_41797611","title":"Regulation of Cellular Signaling by CUL5 is Dependent on Its Neddylation Status.","date":"2026","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/41797611","citation_count":0,"is_preprint":false},{"pmid":"41260500","id":"PMC_41260500","title":"The Mechanism of Histone Ubiquitylation by the ASB9-CUL5 Ubiquitin Ligase.","date":"2025","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/41260500","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":35621,"output_tokens":9301,"usd":0.123189,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":18958,"output_tokens":4342,"usd":0.10167,"stage2_stop_reason":"end_turn"},"total_usd":0.224859,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"HIV-1 Vif interacts with CUL5, Elongin B/C, and Rbx1 to form an SCF-like E3 ubiquitin ligase complex that ubiquitinates and degrades APOBEC3G/CEM15. A Vif mutant that retained APOBEC3G binding but lost CUL5-SCF interaction was functionally inactive, establishing CUL5-SCF as required for Vif-mediated APOBEC3G degradation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, dominant-negative CUL5 mutants, Vif point mutants\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, in vivo ubiquitination, loss-of-function mutants), replicated across multiple subsequent studies\",\n      \"pmids\": [\"14564014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SOCS-box proteins (containing a BC box and downstream Cul5-box) specifically assemble with CUL5-Rbx2, whereas VHL-box proteins assemble with Cul2-Rbx1. Domain-swapping showed that the Cul5-box and Cul2-box sequences determine which Cullin-Rbx module is recruited. RNAi knockdown of Cul5-Rbx2 did not affect VHL-mediated HIF-2α degradation, confirming functional distinction.\",\n      \"method\": \"Co-immunoprecipitation, domain-swapping mutagenesis, RNAi knockdown\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, mutagenesis, and RNAi functional validation in single study; foundational work replicated in subsequent papers\",\n      \"pmids\": [\"15601820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"HIV-1 Vif contains a novel SOCS-box in which alanine replaces the consensus cysteine; this SOCS box mediates interaction with Elongin C, but two conserved Cys residues outside the SOCS box are additionally required for interaction with CUL5 (not Elongin C), establishing that selective CUL5 assembly requires protein interfaces beyond the SOCS-box–Elongin C interaction.\",\n      \"method\": \"Mutagenesis, co-immunoprecipitation, pulldown assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — site-directed mutagenesis with Co-IP validation; replicated/extended by subsequent structural and biochemical studies\",\n      \"pmids\": [\"15574593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Vif recruits CUL5-EloB-EloC through a novel SOCS-box that binds EloC. Serine phosphorylation in the BC-box motif negatively regulates Vif binding to EloC. Vif itself is autoubiquitinated within the assembled Vif-CUL5 complex, analogous to F-box protein autoubiquitination within SCF complexes.\",\n      \"method\": \"Co-immunoprecipitation, in vitro and in vivo ubiquitination assays, phosphorylation analysis, mutagenesis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro ubiquitination assay plus mutagenesis and phosphorylation studies; multiple orthogonal methods\",\n      \"pmids\": [\"15574592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"HIV-1 Vif exploits the CUL5-E3 ligase to ubiquitinate and degrade both APOBEC3F and APOBEC3G. Depletion of CUL5 by RNAi or overexpression of dominant-negative CUL5 mutants blocked Vif-mediated suppression of APOBEC3F. Vif stability itself is also regulated by CUL5-E3 ligase, suggesting the viral substrate receptor is itself a CUL5 substrate.\",\n      \"method\": \"RNA interference, dominant-negative CUL5 mutants, co-immunoprecipitation, ubiquitination assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNAi and dominant-negative approaches with functional readouts; extends PMID 14564014 findings to APOBEC3F\",\n      \"pmids\": [\"16014920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HIV-1 Vif is a zinc-binding protein containing an H-x(5)-C-x(17-18)-C-x(3-5)-H (HCCH) motif. Zinc coordination stabilizes a conserved hydrophobic interface within the HCCH motif critical for Vif-CUL5 E3 assembly. An N-terminal region of the first Cullin repeat of CUL5, dispensable for Elongin C binding, is required for Vif interaction, and this region is the most divergent between CUL2 and CUL5.\",\n      \"method\": \"Zinc-binding characterization, mutagenesis, co-immunoprecipitation, deletion analysis of CUL5\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — zinc-binding biochemistry plus structure-function mutagenesis of both Vif and CUL5; multiple orthogonal approaches\",\n      \"pmids\": [\"16530799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MUF1, a novel leucine-rich repeat BC-box protein purified from rat liver, assembles with CUL5 and Rbx1 to reconstitute ubiquitin ligase activity in vitro. Elongin A, SOCS1, and WSB1 were also shown to assemble with the CUL5/Rbx1 module to reconstitute potential E3 ligases.\",\n      \"method\": \"Protein purification from rat liver, in vitro reconstitution of ubiquitin ligase activity, biochemical assembly assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro reconstitution of ubiquitin ligase activity with purified components; foundational biochemical demonstration\",\n      \"pmids\": [\"11384984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Structure-function studies of BC-box proteins define CUL5-box and CUL2-box sequences in detail. The spacing between BC-box and Cullin-box can vary widely (3 to ~80 amino acids). The LPPhiP motif conserved in most Cul5-boxes is also compatible with Cul2 interaction, indicating the motif alone does not determine Cullin specificity.\",\n      \"method\": \"Purification of BC-box proteins, structure-function mutagenesis, biochemical reconstitution of ubiquitin ligases\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution and systematic structure-function analysis in single thorough study\",\n      \"pmids\": [\"18187417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HIV-1 Vif binds ElonginBC (EloBC) at two locations via an induced-folding mechanism: (1) the established BC-box binding to EloC, and (2) a novel interaction between the conserved Pro-Pro-Leu-Pro (PPLP) motif of Vif and the C-terminal domain of EloB. Both interactions are required for formation of a functional CUL5-containing ligase complex.\",\n      \"method\": \"Purified protein binding assays, isothermal titration calorimetry, NMR spectroscopy, cell-based functional assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — ITC and NMR with purified proteins plus cell-based validation; multiple orthogonal methods in single study\",\n      \"pmids\": [\"20532212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structure of the Vif-CBF-β-CUL5-ELOB-ELOC pentameric complex revealed that Vif uses two domains to organize complex formation: an α/β domain binds CBF-β (competing with RUNX1), and an α-domain contacts both ELOC and CUL5 cooperatively, mimicking SOCS2 interactions. A unique zinc-finger motif of Vif stabilizes the α-domain conformation required for CUL5 interaction.\",\n      \"method\": \"X-ray crystallography (crystal structure), structural analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure of the pentameric complex providing atomic-level mechanistic detail\",\n      \"pmids\": [\"24402281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structures of the ASB9-Elongin B/C ternary complex and the N-terminal domain of CUL5 reveal that ankyrin repeat SOCS-box proteins (ASBs) assemble with EloBC and CUL5 in a distinct architecture where the ankyrin domain is coaxial to the SOCS box-EloBC complex, positioning the substrate-binding site to face the E2-ubiquitin. The CUL5 structure showed a rigid-body rotation between Cullin repeats distinguishing it from other Cullins.\",\n      \"method\": \"X-ray crystallography, structural modeling of complete CUL5-based E3 ligase\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with structural validation; single study but rigorous structural method\",\n      \"pmids\": [\"23806657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL5-RBX2-based E3 ligases partner with ARIH2 (RBR E3) for substrate ubiquitylation. CUL5-linked NEDD8 does not directly recruit ARIH2 (unlike CUL1-linked NEDD8 recruiting ARIH1); instead, NEDD8 allosterically rearranges CUL5 to expose cryptic ARIH2-binding sites, revealing a cullin-specific indirect allosteric activation mechanism.\",\n      \"method\": \"Cryo-EM structure, biochemical assembly assays, structural comparison with ARIH1-CUL1 complex\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures with biochemical validation; multiple orthogonal structural and biochemical approaches\",\n      \"pmids\": [\"34518685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL5 neddylation allosterically exposes its ARIH2-binding site, promoting high-affinity ARIH2 binding, and simultaneously sequesters the NEDD8 E2 (UBE2F) binding site on RBX2. ASB9-CRL5 ubiquitylates its substrate CKB via the ASB9-CRL5-ARIH2-UBE2L3 complex; additional E2s (UBE2R1, UBE2D2) contribute to polyubiquitylation but do not alter ubiquitylation sites.\",\n      \"method\": \"In vitro ubiquitination assay, hydrogen-deuterium exchange mass spectrometry (HDX-MS), mass spectrometry analysis of ubiquitylation sites\",\n      \"journal\": \"Molecular & cellular proteomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstituted in vitro ubiquitination with HDX-MS allosteric mapping; multiple orthogonal biochemical methods\",\n      \"pmids\": [\"33268465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CUL5, RNF7, and UBE2F form a CRL5 complex that proteasomally regulates levels of BH3-only pro-apoptotic proteins Bim and Noxa. Loss of CRL5 components re-sensitizes lung cancer cells to CDK9 and MCL1 inhibitors. Noxa accumulation upon CRL5 depletion is responsible for re-sensitization to CDK9 inhibitor.\",\n      \"method\": \"Genome-wide CRISPR screen (flow cytometry-based), genetic knockouts, protein level analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide CRISPR screen with functional validation of specific substrates (Noxa, Bim) via KO; multiple orthogonal methods\",\n      \"pmids\": [\"31294695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CUL5-ASB11 is an E3 ubiquitin ligase that ubiquitinates BIK (pro-apoptotic BH3-only protein) for proteasomal degradation. During ER stress, XBP1s activates ASB11, promoting BIK ubiquitination and interaction with p97/VCP, enabling ER stress adaptation (cell survival). Genotoxic agents down-regulate the IRE1α-XBP1s-ASB11 axis, stabilizing BIK and promoting apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, knockdown/knockout experiments, cell death assays, IRE1α inhibitor treatment\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — identification of substrate (BIK), E3 complex (CUL5-ASB11), and upstream regulation (XBP1s) with multiple functional readouts\",\n      \"pmids\": [\"31387940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The Rab40b/CUL5 complex ubiquitylates the small GTPase Rap2. This ubiquitylation regulates Rap2 activation state and its recycling from the endolysosomal compartment to the lamellipodia of migrating breast cancer cells, controlling Rap2-dependent actin dynamics at the leading edge required for cell migration and invasion.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, live-cell imaging, loss-of-function experiments, cell migration/invasion assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — substrate identification (Rap2), ubiquitination assay, localization imaging, and functional migration readout; multiple orthogonal methods\",\n      \"pmids\": [\"35293963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CUL5 determines CD4+ T cell fate between T helper and T regulatory cells by regulating IL-4 receptor signaling. Upon T cell activation, CUL5 forms a complex with CIS (SOCS-box protein) and phospho-Jak1 (pJak1). CUL5 deletion reduces ubiquitination and degradation of pJak1, elevating pJak1 and pSTAT6 levels and lowering the threshold for IL-4 receptor signaling, diverting cells from Treg to Th9 fate.\",\n      \"method\": \"Conditional knockout mice (Cul5 fl/fl x CD4-Cre), co-immunoprecipitation of CUL5-CIS-pJak1 complex, Western blot for pJak1/pSTAT6, T cell differentiation assays, in vivo asthma model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with defined molecular mechanism (CUL5-CIS-pJak1 complex, substrate pJak1), multiple orthogonal methods, in vivo phenotype\",\n      \"pmids\": [\"35589717\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CUL5 is a negative regulator of TCR and cytokine (IL-2) signaling in CD8+ T cells. CUL5 is upregulated by TCR stimulation and interacts with SOCS-box-containing protein PCMTD2 to inhibit signaling. CUL5 knockout enhances CD8+ T cell anti-tumor activity. Neddylation inhibition (MLN4924), which blocks CUL5 activation, similarly enhances CD8+ effector activities with CUL5 validated as a major target.\",\n      \"method\": \"CRISPR-based stepwise screening, CUL5 knockout in mouse CD8+ T cells, proteomics, co-immunoprecipitation (CUL5-PCMTD2), neddylation inhibitor (MLN4924), tumor growth assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR screen with mechanistic follow-up (Co-IP, proteomics, chemical inhibition), in vivo tumor model; multiple orthogonal methods\",\n      \"pmids\": [\"38242867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The CUL5-type ubiquitin ligase KLHDC1 targets truncated SELENOS (a selenoprotein lacking selenocysteine due to failed UGA/Sec decoding) for proteasomal degradation. KLHDC1 knockdown in U2OS cells decreased ER stress-induced cell death and increased the population with lower ROS levels.\",\n      \"method\": \"Protein interaction assays, knockdown experiments, flow cytometry for ROS/cell death, proteasome inhibition assays\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — substrate identification (truncated SELENOS) with functional knockdown phenotype; single lab, methods partially inferred from abstract\",\n      \"pmids\": [\"32200094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL5-ASB6 complex acts as an E3 ubiquitin ligase mediating p62/SQSTM1 ubiquitination and proteasomal degradation. Depletion of CUL5 or ASB6 induced p62 accumulation; ASB6 overexpression promoted p62 ubiquitination and degradation, inhibited cell proliferation, and impaired autophagy.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, overexpression, cell proliferation and autophagy assays\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — substrate identification (p62) with ubiquitination assay and functional readouts; single lab\",\n      \"pmids\": [\"34164402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Gossypol inhibits CUL5 neddylation by directly binding to the SAG-CUL5 complex (with CUL5-H572 playing a key role in gossypol binding), blocking CUL5 E3 ligase activation and causing accumulation of NOXA (a CUL5 substrate) in cancer cells.\",\n      \"method\": \"AlphaScreen high-throughput in vitro neddylation assay, biochemical binding studies, compound library screen, cellular substrate accumulation assays\",\n      \"journal\": \"Neoplasia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro neddylation assay with direct binding evidence and mutagenesis of key binding residue (H572); single lab\",\n      \"pmids\": [\"32145688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PKA-dependent phosphorylation of VACM-1/CUL5 at Ser730 controls its neddylation status. Mutation S730A increases NEDD8 modification of CUL5 and is associated with increased cellular growth. Induction of PKA activity with forskolin reduced NEDD8 modification of CUL5. PKC activity further promotes growth in S730A-CUL5 cells.\",\n      \"method\": \"Site-directed mutagenesis, Western blot with phospho-specific and NEDD8 antibodies, immunoprecipitation, cell growth assays, PKA/PKC agonists/inhibitors\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with biochemical readout of neddylation and growth; multiple methods but single lab\",\n      \"pmids\": [\"19917606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"VACM-1/CUL5 expression inhibits basal and stimulated cAMP production in a PKA-dependent manner. Mutation at the PKA phosphorylation site (S730A) reverses the inhibitory effect on cAMP. VACM-1 expression also stimulates inositol 1,4,5-trisphosphate (IP3) production in response to AVP, establishing CUL5 as a regulator of cAMP and calcium signaling pathways.\",\n      \"method\": \"Stable cell line overexpression, cAMP assays, IP3 assays, PKA/PKC inhibitor treatments, site-directed mutagenesis\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple signaling readouts with pharmacological and mutagenesis validation; single lab\",\n      \"pmids\": [\"10898738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In hematopoietic stem cells, CUL5 forms a complex with LRRC41 (identified by reciprocal Co-IP), and CUL5 regulates STAT5 and LRRC41 protein levels during IL-3 stimulation. Mice lacking CUL5 in hematopoietic cells (Cul5Vav-Cre) accumulate LRRC41 and STAT5 during IL-3 stimulation, display myeloid/megakaryocyte-biased differentiation, increased HSC proliferation, and reduced CXCR4 surface expression. JAK1/2 inhibition (ruxolitinib) normalizes hematopoiesis.\",\n      \"method\": \"Conditional knockout mice (Cul5Vav-Cre), reciprocal co-immunoprecipitation (CUL5-LRRC41), whole-cell proteomics, cytokine stimulation assays, flow cytometry, ruxolitinib rescue\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with defined substrates/binding partners (LRRC41, STAT5), reciprocal Co-IP, proteomics, and pharmacological rescue; multiple orthogonal methods\",\n      \"pmids\": [\"40569692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A nuclear localization signal (NLS: 640PKLKRQ646) in VACM-1/CUL5 is required for its nuclear translocation and antiproliferative effect. Mutation of Lys642 and Lys644 to Gly significantly reduced nuclear localization and compromised the growth-inhibitory effect. The NLS also controls the proliferative phenotype and nuclear NEDD8 signal of the S730A-CUL5 mutant.\",\n      \"method\": \"Site-directed mutagenesis, immunocytochemistry, cell growth assays, Western blot for neddylation\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — mutagenesis with localization and functional readout; single lab, localization linked to growth phenotype\",\n      \"pmids\": [\"27834018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"VACM-1/CUL5 expression in vitro reduces aquaporin-1 (AQP1) protein levels (~6-fold) in COS-1 cells. In vivo, water deprivation increases CUL5 NEDD8 modification in vascular tissue, and AQP1 levels are inversely correlated with the ratio of neddylated to total VACM-1/CUL5, suggesting CUL5 regulates endothelial AQP1 concentration.\",\n      \"method\": \"Microarray, transfection with VACM-1 cDNA, Western blot, immunocytochemistry, in vivo water deprivation model\",\n      \"journal\": \"Cell and tissue research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — correlation-based in vivo evidence and single overexpression experiment in vitro; no direct ubiquitination assay for AQP1\",\n      \"pmids\": [\"22581383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"VACM-1/CUL5 expression decreases AQP2 protein concentration in MDCK cells stably expressing AQP2 and in COS-1 cells co-transfected with AQP2 and VACM-1 cDNAs. In water-deprived rat kidneys, decreased CUL5 protein correlates with increased AQP2 levels in collecting duct.\",\n      \"method\": \"Overexpression/co-transfection, Western blot, immunocytochemistry, in vivo water deprivation\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — overexpression phenotype with correlative in vivo data; no direct ubiquitination or mechanistic assay for AQP2; single lab\",\n      \"pmids\": [\"23171819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In Drosophila oogenesis, reduced CUL-5 activity causes aberrant follicle formation with excess germ cells, overproliferation of germ line cells, defective cyst encapsulation, and germ cell depletion. These phenotypes are enhanced by reduced activity of gustavus (a SOCS-box-containing substrate receptor of CUL5-based E3 ligases), establishing CUL5/Gus E3 complexes as required for germ cell proliferation, maintenance, and follicular morphogenesis.\",\n      \"method\": \"Drosophila genetics (cul-5 loss-of-function mutants, gustavus mutants, genetic epistasis), histology, immunofluorescence\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in Drosophila ortholog with defined cellular phenotypes; functional relevance supported by SOCS-box enhancer interaction\",\n      \"pmids\": [\"20140218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In zebrafish, d-Asb11 requires its CUL5-box domain to function as part of a CUL5-based E3 ligase. Zebrafish mutants lacking the Asb11 Cul5-box fail to degrade the Notch ligand DeltaA, impair Notch target gene expression, and show defective cell fate specification in neurogenic regions, demonstrating that the CUL5-box is required for Notch signaling and neurogenesis in vivo.\",\n      \"method\": \"Zebrafish genetics (Cul5-box mutant), Notch reporter assays, immunostaining for DeltaA, RNA injection rescue experiments\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo zebrafish mutant with defined molecular substrate (DeltaA) and signaling pathway (Notch); single study\",\n      \"pmids\": [\"21124961\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ASB9-CRL5 ubiquitylates histones H3 and H4 (but not H2A or H2B) via K48 and K63 polyubiquitin chains, targeting free histones for degradation. Neddylated ASB9-CRL5 binds histones with highest affinity via electrostatic interactions. Histones in nucleosomes or bound to chaperone Asf1 are not ubiquitylated. This CUL5-mediated ubiquitylation does not require the RING-between-RING helper ligase ARIH2, representing the first example of ARIH2-independent CUL5-mediated ubiquitylation.\",\n      \"method\": \"In vitro ubiquitination reconstitution, mass spectrometry for ubiquitylation sites and chain types, binding experiments, neddylated vs. unneddylated complex comparison\",\n      \"journal\": \"Molecular & cellular proteomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified components, MS-based site mapping, multiple substrate conditions tested; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"41260500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The E3 ligase Cul5-Wsb2 uses BCL2 family proteins (Bcl-xl, Bcl-w, Bcl2 — but not Mcl1) as co-receptors to target Bim for ubiquitination and degradation. Wsb2 recognizes Bcl-xl through a conserved motif; disruption of this interaction prevents Wsb2 binding to the Bcl-xl/Bim dimer and blocks Bim degradation. Wsb2 contacts the Mcl1/Bim dimer through a separate Wsb2 interface.\",\n      \"method\": \"Co-immunoprecipitation, mutagenesis of Bcl-xl and Wsb2, ubiquitination assays, knockdown cell viability assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with mutagenesis, ubiquitination assay, and cell viability functional readout; preprint, single lab\",\n      \"pmids\": [\"40832228\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL5 interacts with NAMPT (Visfatin) as shown by co-immunoprecipitation, and CUL5 promotes NAMPT degradation. CUL5 overexpression in H2O2-stimulated human coronary artery endothelial cells reduces phosphorylation of p38 and Akt and decreases VEGF and MMP2 protein levels, inhibiting angiogenic functions.\",\n      \"method\": \"Co-immunoprecipitation, overexpression, Western blot for pAkt/p38/VEGF/MMP2, cell viability/migration/tube formation assays\",\n      \"journal\": \"Journal of cardiovascular pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP for substrate identification, no direct ubiquitination assay; single lab\",\n      \"pmids\": [\"34596622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CUL5 loss in bladder cancer cells reduces ubiquitination of PTBP1. Loss of PTBP1 ubiquitination alters alternative splicing of RUBCN pre-mRNA, increasing the RUBCN-S isoform, which inhibits autophagy and thereby prevents immune evasion from CD8+ T cell-mediated killing.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 screen under CD8+ T cell pressure, ubiquitination assay, alternative splicing analysis, in vivo xenograft with anti-PD-1 combination\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen with mechanistic follow-up (ubiquitination assay, splicing analysis); single lab\",\n      \"pmids\": [\"41662369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CUL5 neddylation at Lys724 is critical for its antiproliferative effect; K724R mutation converts CUL5 from a growth inhibitor to a growth promoter in endothelial and cancer cells. Multi-site neddylation (at K724, K727, K728) contributes to CUL5's regulatory effects. In T47D cells, MAPK phosphorylation and ERα expression are directly correlated with CUL5 neddylation status.\",\n      \"method\": \"Site-directed mutagenesis of neddylation sites, cell proliferation assays, Western blot, MLN4924 neddylation inhibitor, immunoprecipitation\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic mutagenesis of neddylation sites with functional proliferation and signaling readouts; single lab\",\n      \"pmids\": [\"41797611\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CUL5 is the scaffold subunit of the Cullin-RING Ligase 5 (CRL5) complex, which assembles with RBX2, Elongin B/C, and SOCS-box-containing substrate receptors (including SOCS proteins, ASB proteins, and viral hijackers like HIV-1 Vif) to form E3 ubiquitin ligases that ubiquitinate and proteasomally degrade diverse substrates—including APOBEC3G/F, Rap2, BIK, p62, Noxa, Bim, STAT5, pJak1, PTBP1, and free histones H3/H4; CRL5 activity requires NEDD8-dependent neddylation of CUL5 (at Lys724 and other sites), which allosterically exposes the binding site for the co-E3 ARIH2 (though some substrates are ubiquitylated ARIH2-independently); and CUL5 controls key cellular processes including antiviral defense, T cell fate decisions, hematopoietic stem cell homeostasis, cell cycle progression, apoptosis, cell migration, and angiogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CUL5 is the scaffold subunit of Cullin-RING E3 ubiquitin ligase complexes (CRL5) that target diverse substrates for proteasomal degradation, thereby controlling antiviral defense, apoptosis, T cell and hematopoietic cell fate, cell migration, and proliferation [#0, #6, #16]. CUL5 assembles with RBX2/RNF7 and the Elongin B/C adaptor module, which docks SOCS-box-containing substrate receptors via a BC-box, while a distinct Cul5-box determines selective CUL5 (versus CUL2) recruitment [#1, #6, #7]. Through this architecture CUL5 partners with a broad family of substrate receptors—including ASB proteins (ASB9, ASB11, ASB6), CIS, WSB2, KLHDC1, gustavus, Rab40b, PCMTD2, and LRRC41—each delivering specific substrates such as creatine kinase, the pro-apoptotic BH3-only proteins BIK, Bim, and Noxa, p62/SQSTM1, truncated SELENOS, the GTPase Rap2, phospho-Jak1, STAT5, and PTBP1 [#10, #13, #14, #15, #16, #18, #19, #23, #30]. CRL5 activity is gated by NEDD8 conjugation of CUL5 (at Lys724 and additional sites), which allosterically remodels CUL5 to expose a cryptic binding site for the co-E3 ARIH2 while sequestering the NEDD8 E2 UBE2F site on RBX2, although some substrates such as free histones H3/H4 are ubiquitylated ARIH2-independently [#11, #12, #29, #33]. HIV-1 Vif hijacks this machinery as a SOCS-box mimic, using a zinc-coordinated HCCH motif, CBF-β binding, and cooperative ELOC/CUL5 contacts to reconstitute a CRL5 that degrades the antiviral cytidine deaminases APOBEC3G and APOBEC3F [#0, #4, #5, #9]. CUL5 substrate selection is exploited physiologically to set signaling thresholds: CRL5-CIS degrades phospho-Jak1 to bias CD4+ T cell fate, CRL5 restrains TCR/IL-2 signaling in CD8+ T cells via PCMTD2, and CRL5-LRRC41 limits STAT5 to maintain hematopoietic stem cell homeostasis [#16, #17, #23].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established that CUL5 is a functional E3 ligase scaffold, answering whether it could nucleate ubiquitin ligase activity with substrate receptors.\",\n      \"evidence\": \"In vitro reconstitution of ubiquitin ligase activity from CUL5/Rbx1 with purified BC-box proteins (MUF1, Elongin A, SOCS1, WSB1) from rat liver\",\n      \"pmids\": [\"11384984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define which physiological substrates are targeted\", \"Did not establish CUL5-versus-CUL2 specificity determinants\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed that HIV-1 Vif coopts a CUL5-Elongin B/C-Rbx1 ligase to degrade APOBEC3G, defining the first biologically critical CRL5 substrate axis.\",\n      \"evidence\": \"Co-IP, in vivo ubiquitination, dominant-negative CUL5 and Vif point mutants\",\n      \"pmids\": [\"14564014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic basis of Vif-CUL5 selectivity unresolved\", \"Did not address host substrate receptors\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the molecular code for CUL5-specific receptor recruitment, distinguishing CRL5 from CRL2 assembly.\",\n      \"evidence\": \"Reciprocal Co-IP, domain-swapping mutagenesis, and RNAi separating Cul5-box/SOCS-box from VHL-box/Cul2-box; characterization of Vif's atypical SOCS box and additional Cys-dependent CUL5 contacts and autoubiquitination\",\n      \"pmids\": [\"15601820\", \"15574593\", \"15574592\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"LPPhiP motif alone does not fully dictate Cullin choice\", \"Structural mechanism of selectivity not yet visualized\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Pinpointed the zinc-coordinated HCCH motif of Vif and the divergent N-terminal CUL5 region as the basis of selective viral CRL5 assembly.\",\n      \"evidence\": \"Zinc-binding biochemistry, mutagenesis, and CUL5 deletion analysis with Co-IP\",\n      \"pmids\": [\"16530799\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism extended to APOBEC3F via RNAi/dominant-negative but degradation kinetics not resolved [#16014920]\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Systematically defined how BC-box-to-Cullin-box spacing and motif variation govern receptor assembly across the BC-box protein family.\",\n      \"evidence\": \"Purification of BC-box proteins with structure-function mutagenesis and in vitro ligase reconstitution\",\n      \"pmids\": [\"18187417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not assign specific physiological substrates to each receptor\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided atomic-level visualization of the Vif-CBF-β-CUL5-ELOB-ELOC pentamer, explaining cooperative ELOC/CUL5 engagement and SOCS2 mimicry.\",\n      \"evidence\": \"X-ray crystallography of the pentameric complex; complemented by earlier ITC/NMR mapping of dual EloBC contacts and ASB9/CUL5 structural architecture\",\n      \"pmids\": [\"24402281\", \"20532212\", \"23806657\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not capture the neddylated, catalytically active state\", \"Substrate positioning relative to E2 inferred, not directly observed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Resolved how NEDD8 activates CRL5, establishing a cullin-specific allosteric mechanism distinct from CRL1.\",\n      \"evidence\": \"Cryo-EM, HDX-MS, and reconstituted ubiquitination showing NEDD8 allosterically exposes the ARIH2 site and sequesters the UBE2F site on RBX2; ASB9-CRL5-ARIH2-UBE2L3 ubiquitylates CKB\",\n      \"pmids\": [\"34518685\", \"33268465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish which substrates strictly require ARIH2 versus act independently\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated CRL5 as a tunable rheostat for immune-cell signaling and cytoskeletal control through receptor-specific substrate choice.\",\n      \"evidence\": \"Conditional Cul5 knockout mice and Co-IP defining CRL5-CIS-pJak1 control of CD4+ T cell fate; ubiquitination/imaging defining Rab40b-CUL5 control of Rap2 and migration\",\n      \"pmids\": [\"35589717\", \"35293963\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo substrate specificity for additional receptors not mapped\", \"Direct ubiquitination kinetics in primary cells not resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Established CUL5 as a brake on CD8+ T cell anti-tumor activity, linking neddylation-dependent CRL5 activity to immunotherapy.\",\n      \"evidence\": \"CRISPR screening, CUL5 knockout, proteomics, CUL5-PCMTD2 Co-IP, MLN4924 treatment, and tumor models\",\n      \"pmids\": [\"38242867\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct PCMTD2 substrate(s) not fully enumerated\", \"Relationship to other CRL5 immune substrates unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended CRL5 substrate scope to hematopoietic homeostasis and to ARIH2-independent ubiquitylation of free histones.\",\n      \"evidence\": \"Conditional Cul5 knockout mice with reciprocal CUL5-LRRC41 Co-IP and proteomics linking CUL5 to STAT5/LRRC41; in vitro reconstitution and MS showing neddylated ASB9-CRL5 ubiquitylates free H3/H4 ARIH2-independently\",\n      \"pmids\": [\"40569692\", \"41260500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LRRC41 is a direct substrate or co-receptor not fully resolved\", \"Cellular consequences of free-histone ubiquitylation not established in vivo\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Connected CRL5 substrate control to mRNA splicing, autophagy, and tumor immune evasion, and refined the neddylation sites governing its growth-regulatory output.\",\n      \"evidence\": \"CRISPR screen under CD8+ T cell pressure with PTBP1 ubiquitination and RUBCN splicing analysis; site-directed mutagenesis showing Lys724/K727/K728 neddylation dictates antiproliferative activity\",\n      \"pmids\": [\"41662369\", \"41797611\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PTBP1 receptor not identified\", \"Mechanistic link between neddylation site occupancy and substrate selection incompletely defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how individual SOCS-box receptors and upstream signals are coordinated to select among the large CRL5 substrate repertoire in a given cell type, and how non-canonical CUL5 signaling functions (cAMP/IP3 modulation, nuclear localization) integrate with its ligase activity.\",\n      \"evidence\": \"Not established in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model linking receptor abundance to substrate prioritization\", \"Mechanism of reported nuclear/signaling roles not connected to E3 activity\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 6, 14, 15]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 12, 29]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 6, 7, 11]},\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [11, 12, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [24]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-983168\", \"supporting_discovery_ids\": [0, 11, 12]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 16, 17]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [13, 14, 30]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [16, 23]}\n    ],\n    \"complexes\": [\n      \"CRL5 (CUL5-RBX2/RNF7-Elongin B/C E3 ubiquitin ligase)\",\n      \"Vif-CBF-β-CUL5-ELOB-ELOC complex\",\n      \"ASB9-CRL5-ARIH2 ligase\"\n    ],\n    \"partners\": [\n      \"RBX2/RNF7\",\n      \"Elongin B/C\",\n      \"ARIH2\",\n      \"UBE2F\",\n      \"ASB9\",\n      \"ASB11\",\n      \"CIS\",\n      \"LRRC41\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}