{"gene":"CUL4B","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2009,"finding":"CUL4B contains a nuclear localization signal (NLS) in its N-terminus (amino acids 37-40, KKRK) that binds importin α1, α3, and α5. Unlike CUL4A and other cullins which carry NLS in their C-termini, this N-terminal NLS is unique to CUL4B. NLS-deleted CUL4B localizes to the cytoplasm and fails to promote cell proliferation. CUL4B promotes ubiquitination and degradation of cyclin E, and RNAi silencing leads to overaccumulation of cyclin E, prolonged S phase, and inhibited cell proliferation.","method":"RNAi silencing, NLS deletion mutants, importin binding assays, subcellular fractionation, cell cycle analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional assays, NLS mapping with mutagenesis, importin binding, multiple orthogonal methods in single study replicated by other labs","pmids":["19801544"],"is_preprint":false},{"year":2007,"finding":"CUL4B is a scaffold protein that organizes a cullin-RING (E3) ubiquitin ligase complex. A nonsense mutation (p.R388X) truncates the C-terminal catalytic domain and causes nonsense-mediated mRNA decay, demonstrating that the C-terminal domain is essential for ligase function.","method":"Mutation analysis, mRNA expression in patient leukocytes, X-chromosome inactivation analysis","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined molecular consequence (NMD, truncation of catalytic domain), single study","pmids":["17273978"],"is_preprint":false},{"year":2013,"finding":"CUL4B promotes DNA replication licensing by positively regulating CDC6 (a replication licensing factor) through a CDK2-dependent mechanism: CUL4B represses miR-372 and miR-373, which target CDK2, thereby elevating CDK2 levels; CDK2 then phosphorylates CDC6, protecting it from APC(CDH1)-mediated degradation, which in turn promotes loading of MCM2 onto chromatin.","method":"RNAi knockdown, chromatin fractionation for MCM2 loading, miRNA overexpression/inhibition, immunoblotting","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods establishing a complete pathway cascade, epistasis experiments","pmids":["23479742"],"is_preprint":false},{"year":2013,"finding":"CUL4B ubiquitin ligase targets Jab1/CSN5 (a component of the COP9 signalosome) for polyubiquitination and proteasomal degradation. The DDB1-CUL4B-ROC1 complex is required for this degradation, which is independent of CUL4A. Loss of CUL4B leads to Jab1 accumulation and abnormal upregulation of BMP signaling.","method":"RNAi, in vitro and in vivo ubiquitination assays, Co-IP, Cul4b-deficient mouse embryonic fibroblasts","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitination assay plus in vivo validation in KO cells, Co-IP demonstrating complex, single lab with multiple orthogonal methods","pmids":["23357576"],"is_preprint":false},{"year":2013,"finding":"CUL4B promotes ubiquitination and degradation of TSC2 and cyclin E in neocortical neurons. XLID mutants (R388X, R572C, V745A) fail to promote ubiquitination/degradation of TSC2 or cyclin E. By targeting TSC2 for degradation, wild-type CUL4B positively regulates mTOR signaling (increased p-mTOR, p-p70S6K, p-4E-BP1); CUL4B knockdown or XLID mutants fail to activate mTOR.","method":"Adenovirus-mediated expression in neocortical neurons, shRNA knockdown, immunoblotting for ubiquitination and mTOR pathway substrates","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — overexpression + knockdown + XLID mutant analysis with multiple substrates and pathway readouts in primary neurons","pmids":["23348097"],"is_preprint":false},{"year":2015,"finding":"CUL4B activates Wnt/β-catenin signaling in HCC by epigenetically silencing Wnt pathway antagonists (DKK1, PPP2R2B). CRL4B promotes recruitment/retention of PRC2 at promoters of Wnt antagonists, and CUL4B knockdown decreases PRC2 components and H3K27me3 at these promoters. CUL4B also protects β-catenin from GSK3-mediated degradation through this mechanism.","method":"RNAi knockdown, ChIP for PRC2/H3K27me3, rescue experiments with simultaneous knockdown of PPP2R2B, xenograft models","journal":"The Journal of pathology","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP demonstrating epigenetic mechanism, rescue experiments with epistasis, in vitro and in vivo validation","pmids":["25430888"],"is_preprint":false},{"year":2015,"finding":"CRL4B is required for proteasomal degradation of HUWE1 in response to DNA damage. CUL4B is activated in a NEDD8-dependent manner and ubiquitinates HUWE1 in vitro and in vivo. CUL4B depletion stabilizes HUWE1, which accelerates MCL-1 degradation and increases apoptosis; these phenotypes are rescued by simultaneous HUWE1 depletion.","method":"In vitro ubiquitination assay, RNAi, epistasis (double knockdown rescue), immunoblotting","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitination assay, genetic epistasis with double knockdown rescue, multiple orthogonal methods","pmids":["25883150"],"is_preprint":false},{"year":2012,"finding":"CUL4B is essential for embryonic development; Cul4b null mouse embryos die before E9.5 with severe developmental arrest. Cyclin E (a CRL4B substrate) accumulates in Cul4b null embryos. Epiblast-specific deletion of Cul4b prevents lethality, demonstrating that CUL4B's essential function is in extra-embryonic tissues rather than the embryo proper.","method":"Cul4b knockout mouse generation, conditional epiblast-specific deletion (Sox2-Cre), immunoblotting for cyclin E","journal":"Cell research","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent KO studies (PMIDs 22606329 and 22453236) with conditional rescue demonstrating tissue-specific requirement","pmids":["22453236","22606329"],"is_preprint":false},{"year":2016,"finding":"CUL4B negatively regulates PPARγ by promoting its polyubiquitination and proteasomal degradation. Depletion of CUL4B leads to upregulation of PPARγ-regulated genes and facilitates adipogenesis. Adipocyte-specific Cul4b KO mice show increased adipogenesis and fat accumulation but improved insulin sensitivity and glucose tolerance.","method":"Adipocyte-specific conditional KO mouse, PPARγ ubiquitination assay, high-fat diet metabolic phenotyping","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ubiquitination assay establishing direct substrate relationship, in vivo KO model with metabolic phenotype, single lab multiple orthogonal methods","pmids":["27899484"],"is_preprint":false},{"year":2016,"finding":"CUL4B performs both cell-autonomous and non-cell-autonomous functions in spermatogenesis. In germ cells, CUL4B directly polyubiquitinates and degrades INSL6 (identified by mass spectrometry); loss of germ cell CUL4B impairs sperm motility due to reduced mitochondrial activity and glycolysis, and defective flagellar axoneme/outer dense fiber arrangement. In somatic cells, CUL4B maintains the spermatogonial stem cell niche.","method":"Germ cell-specific conditional KO, global KO, mass spectrometry substrate identification, polyubiquitination assay, sperm ATP measurement, electron microscopy of flagella","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mass spectrometry substrate ID with ubiquitination assay, two conditional KO models with distinct phenotypes, multiple orthogonal methods","pmids":["26846852"],"is_preprint":false},{"year":2015,"finding":"CUL4B represses GFAP expression in neural progenitor cells by epigenetically silencing PTGDS. Loss of Cul4b increases PTGDS expression, elevating prostaglandin D2, which promotes astrocyte (GFAP+) generation. CUL4B/PRC2 complex targets and represses Ptgds; pharmacological inhibition of PTGDS or shRNA knockdown attenuates the increased GFAP+ cells from Cul4b-null NPCs.","method":"Nervous system-specific Cul4b KO mice, in vitro NPC culture, ChIP for CUL4B/PRC2 at Ptgds, pharmacological PTGDS inhibition, shRNA knockdown","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo KO plus ChIP demonstrating direct epigenetic regulation of PTGDS, pharmacological rescue, multiple methods","pmids":["26025376"],"is_preprint":false},{"year":2015,"finding":"CUL4B unexpectedly functions as a negative regulator of myeloid-derived suppressor cells (MDSCs). Hematopoietic-specific CUL4B ablation (Tek-Cre) increases MDSC accumulation via downregulation of the AKT/β-catenin pathway. CUL4B represses phosphatases PP2A and PHLPP1/2 (which dephosphorylate/inactivate AKT) to sustain AKT pathway activation.","method":"Hematopoietic-specific conditional KO (Tek-Cre), MDSC quantification, AKT pathway analysis, multiple tumor models","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with defined molecular mechanism (PP2A/PHLPP1/2 repression → AKT), single lab with multiple tumor models and mechanistic pathway placement","pmids":["26450912"],"is_preprint":false},{"year":2019,"finding":"CUL4B negatively regulates TLR-triggered inflammatory responses in macrophages by epigenetically repressing transcription of Pten, thereby maintaining the anti-inflammatory PI3K-AKT-GSK3β pathway. Deletion of CUL4B in macrophages upregulates PTEN, leading to increased GSK3β activity and excessive proinflammatory cytokine production.","method":"Myeloid cell-specific Cul4b KO mice, LPS/pathogen challenge, GSK3β inhibitor rescue, ChIP/epigenetic analysis of Pten promoter","journal":"Cellular & molecular immunology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with pharmacological rescue (GSK3β inhibitor) and ChIP for epigenetic mechanism at Pten, in vivo infection models","pmids":["31729464"],"is_preprint":false},{"year":2017,"finding":"CUL4B epigenetically represses miR-194 by catalyzing monoubiquitination of H2AK119 and coordinating with PRC2 to promote H3K27me3 at the miR-194 gene cluster. miR-194 in turn targets the 3'-UTR of CUL4B, creating a double-negative feedback loop. CUL4B also represses miR-194 downstream of p53.","method":"ChIP for H2AK119ub and H3K27me3 at miR-194 locus, 3'-UTR luciferase reporter assay, RNAi, xenograft tumor formation","journal":"Molecular oncology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ChIP demonstrating direct epigenetic modification at miR-194 locus plus 3'-UTR reporter assay, multiple orthogonal methods","pmids":["28164432"],"is_preprint":false},{"year":2021,"finding":"CUL4B renders breast cancer cells tamoxifen-resistant through a miR-32-5p/ER-α36 axis. CRL4B epigenetically represses miR-32-5p transcription by catalyzing H2AK119 monoubiquitination and coordinating with PRC2 and HDAC complexes to promote H3K27me3 at the miR-32-5p promoter, leading to upregulation of ER-α36.","method":"ChIP for H2AK119ub and H3K27me3 at miR-32-5p promoter, dominant-negative CUL4B mutant, pharmacological inhibition of CRL4B/PRC2/HDAC, in vitro and in vivo tamoxifen sensitivity assays","journal":"The Journal of pathology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ChIP demonstrating direct epigenetic mechanism, dominant-negative mutant, pharmacological inhibition, in vitro and in vivo validation","pmids":["33638154"],"is_preprint":false},{"year":2014,"finding":"CUL4B suppresses stress-induced cellular senescence by promoting p53 ubiquitination and proteasomal degradation in normal human fibroblasts exposed to oxidative stress (H2O2), thereby dampening a p53-ROS positive feedback loop that drives senescence. CUL4B is downregulated in stress-induced (but not replicative) senescent cells.","method":"Ectopic CUL4B expression, RNAi, H2O2 treatment, p53 ubiquitination assay, ROS measurement, senescence β-galactosidase assay","journal":"Free radical biology & medicine","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ubiquitination assay for p53 as substrate, gain- and loss-of-function, multiple orthogonal senescence readouts, single lab","pmids":["25464270"],"is_preprint":false},{"year":2021,"finding":"CUL4B promotes HBV replication by interacting with the viral protein HBx and inhibiting HBx ubiquitination and proteasomal degradation, thereby stabilizing HBx. This interaction was demonstrated by immunoprecipitation and immunofluorescence co-localization.","method":"Co-immunoprecipitation, immunofluorescence co-staining, cycloheximide chase assay, in vivo ubiquitination assay, Cul4b transgenic and conditional KO mice with hydrodynamic HBV model","journal":"Cancer biology & medicine","confidence":"High","confidence_rationale":"Tier 1 / Moderate — Co-IP demonstrating direct interaction, in vivo ubiquitination assay, transgenic and KO mouse models, multiple orthogonal methods in single study","pmids":["33969670"],"is_preprint":false},{"year":2021,"finding":"TCDD-activated AHR is partially degraded via CUL4B-mediated ubiquitination; loss of CUL4B partially prevents AHR degradation after TCDD exposure. TiPARP additionally promotes AHR nuclear export preceding degradation; knockdown of TiPARP in CUL4B-null cells completely abolishes AHR degradation, indicating CUL4B and TiPARP cooperate to restrain AHR activity.","method":"Cul4b-null MEF cell line, TiPARP knockdown in null cells, TCDD treatment, AHR protein level and transcriptional activity measurement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO cell line with TiPARP knockdown epistasis, functional transcriptional readout, multiple conditions tested","pmids":["34146543"],"is_preprint":false},{"year":2023,"finding":"The unique N-terminal extension of CUL4B is heavily phosphorylated during mitosis. Phosphorylation triggers chromatin exclusion of CUL4B while promoting binding to actin regulators and to two previously unrecognized CUL4B-specific DCAFs, LIS1 and WDR1, which interact with DDB1 in a phosphorylation-dependent manner. CUL4B phosphorylation is required for efficient mitosis progression (spindle positioning, cortical tension). The XLID mutation CUL4B-P50L perturbs this phosphorylation pattern. CUL4B is required for developing stable ventricular structures in human forebrain organoids.","method":"Phosphoproteomic analysis, Co-immunoprecipitation of LIS1/WDR1 with DDB1, mutagenesis of phosphorylation sites, live imaging for spindle positioning/cortical tension, human forebrain organoid model","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — phosphoproteomic identification, Co-IP with biochemical validation, mutagenesis, organoid model, multiple orthogonal methods in one rigorous study","pmids":["37365982"],"is_preprint":false},{"year":2023,"finding":"CUL4B and DCAF7 form an E3 ligase complex that promotes MEN1 protein degradation by binding MEN1 and catalyzing its ubiquitination. Neddylation pathway activation is required upstream; neddylation inhibitor MLN4924 induces MEN1 accumulation. DCAF7 downregulation reverses everolimus resistance in PanNET cells in a MEN1-dependent manner.","method":"Co-IP, RNAi knockdown, neddylation inhibitor (MLN4924), in vitro ubiquitination, DCAF7/MEN1 double knockdown epistasis","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — Co-IP establishing complex, ubiquitination assay, epistasis (double KD rescue), pharmacological validation, single lab with multiple orthogonal methods","pmids":["36939378"],"is_preprint":false},{"year":2023,"finding":"CUL4B directly binds to the promoter of Cxcl2 and epigenetically represses its transcription. In KRAS-mutant lung tumors, CUL4B deletion increases CXCL2 expression, which promotes CXCR2-dependent MDSC recruitment to the tumor microenvironment.","method":"ChIP for CUL4B at Cxcl2 promoter, CUL4B KO/KD in autochthonous and transplantable KRAS-mutant tumor models, MDSC quantification, MDSC targeting experiments","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating direct promoter binding, in vivo KO tumor models with mechanistic rescue (MDSC targeting), multiple model systems","pmids":["37653114"],"is_preprint":false},{"year":2024,"finding":"CUL4B mutations (XLID patient-derived) cause premature cell cycle exit and precocious neuronal differentiation of neural progenitor cells, as well as increased synapse formation and enhanced neuronal excitability. Mechanistically, CRL4B complex represses transcription of PPP2R2B and PPP2R2C (PP2A regulatory subunit isoforms) by catalyzing H2AK119 monoubiquitination at their promoters. CUL4B mutations upregulate PP2A activity, inhibiting AKT and ERK, causing premature cell cycle exit; rescue achieved by AKT/ERK activation or PP2A inhibition.","method":"Patient iPSC-derived 2D neuronal cultures and cerebral organoids, ChIP for H2AK119ub, PP2A activity assay, AKT/ERK inhibition/activation, pharmacological PP2A inhibition rescue","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 1 / Strong — patient iPSC-derived isogenic model, ChIP demonstrating direct epigenetic mechanism, biochemical PP2A activity assay, pharmacological rescue with multiple agents","pmids":["38331954"],"is_preprint":false},{"year":2021,"finding":"CUL4B is required for CD4+ T cell proliferation and survival following TCR stimulation. In T cells, CUL4B preferentially associates with the substrate receptor DCAF1; Cul4b and DCAF1 interact with proteins involved in DNA damage sensing/repair. Cul4b-deficient CD4+ T cells accumulate DNA damage and fail to phosphorylate SMC1A (a downstream DNA damage response event), leading to proliferative failure.","method":"Cul4b conditional KO T cells, Co-immunoprecipitation (CUL4B-DCAF1 interaction), mass spectrometry of associated proteins, DNA damage assays, SMC1A phosphorylation analysis","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing CUL4B-DCAF1 complex, KO T cell phenotype with mechanistic DNA damage pathway analysis, mass spectrometry","pmids":["33524014"],"is_preprint":false},{"year":2023,"finding":"c-Myc increases Cul4b protein levels following T cell activation. Cul4b-deficient CD8+ T cells accumulate DNA damage and p21/Cyclin E2, leading to replication stress and proliferative catastrophe. c-Myc supports CD8+ T cell expansion by maintaining genome stability via Cul4b.","method":"Cul4b conditional KO CD8+ T cells, in vivo LCMV infection model, p21/Cyclin E2 immunoblotting, DNA damage assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo KO with viral infection model, molecular pathway analysis (p21/Cyclin E2 accumulation), epistasis placing c-Myc upstream of Cul4b","pmids":["37925424"],"is_preprint":false},{"year":2015,"finding":"CUL4B variants interact with WDR62, a protein mutated in microcephaly patients with malformations of cortical development, suggesting a functional complex.","method":"Co-immunoprecipitation of CUL4B with WDR62","journal":"Human mutation","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP, no functional follow-up mechanistic experiments described in abstract","pmids":["25385192"],"is_preprint":false},{"year":2019,"finding":"CUL4B epigenetically represses IL-6 transcription in myeloid cells via the CRL4B complex. In CUL4B-deficient MDSCs, elevated IL-6 activates IL-6/STAT3 signaling in tumor cells, rendering them stem cell-like properties.","method":"Hematopoietic/myeloid-specific Cul4b KO mice, IL-6 blocking, STAT3 inhibitor, ChIP/epigenetic analysis at IL-6 promoter","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with IL-6 blocking and STAT3 inhibition epistasis, ChIP for epigenetic repression of IL-6 locus","pmids":["31235785"],"is_preprint":false},{"year":2012,"finding":"CUL4B is required for neural progenitor cell mitosis progression. Downregulation of CUL4B arrests NPCs and NT-2 cells in G2/M phase. Three isoforms of CUL4B exist in brain tissue; the larger isoforms (CUL4B-1, -2) are predominantly unneddylated due to their N-terminal extension, while the smaller isoform (CUL4B-3, lacking the N-terminus) is neddylated. Unneddylated CUL4B accumulates during mitosis and inhibits β-catenin degradation in neural stem cell niches.","method":"Immunostaining, RNAi knockdown in NPCs/NT-2 cells, cell cycle analysis, neddylation state analysis, brain tissue immunostaining","journal":"BMC neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — RNAi with cell cycle phenotype and isoform characterization, single study, some mechanistic inferences from correlation","pmids":["22992378"],"is_preprint":false},{"year":2023,"finding":"CUL4B-DDB1-COP1 forms a functional E3 ubiquitin ligase complex responsible for targeting the histone demethylase UTX (KDM6A) for ubiquitination and proteasomal degradation in colorectal cancer cells. Cop1 deficiency in mouse intestinal tissue results in UTX accumulation and restricts tumorigenesis.","method":"Co-immunoprecipitation demonstrating CUL4B-DDB1-COP1 complex, immunoblot for UTX degradation, conditional Cop1 KO mouse, spontaneous AOM/DSS CRC model with GSK126 rescue","journal":"Experimental hematology & oncology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — Co-IP establishing complex, in vivo KO model with EZH2 inhibitor epistasis, multiple orthogonal methods","pmids":["37679762"],"is_preprint":false},{"year":2023,"finding":"CUL4B promotes osteogenesis and inhibits adipogenesis of mesenchymal stem cells by epigenetically repressing KLF4 (an adipogenic factor) and C/EBPδ transcription. The CUL4B complex directly binds to Klf4 and Cebpd promoters and represses their transcription. MSC-specific Cul4b KO mice show impaired skeletal development, low bone mass, and increased marrow adipose accumulation.","method":"MSC-specific conditional Cul4b KO mice, ChIP for CUL4B complex at Klf4/Cebpd promoters, in vitro osteogenic/adipogenic differentiation assays, ovariectomy model","journal":"Bone research","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO mouse with multiple in vivo models, ChIP demonstrating direct promoter binding, in vitro differentiation assays","pmids":["37268647"],"is_preprint":false},{"year":2019,"finding":"CUL4B-RING E3 ligase complex represses transcription of miR-372/373 via H2AK119 monoubiquitination at the miR-372/373 gene cluster, leading to upregulation of PIK3CA and activation of AKT signaling, promoting bladder cancer metastasis and stemness.","method":"ChIP for H2AK119ub at miR-372/373 locus, 3'-UTR reporter assay for PIK3CA targeting, RNAi, invasion/motility assays","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ChIP demonstrating direct histone modification at miR-372/373 locus, reporter assay, multiple oncogenic phenotype readouts","pmids":["32127645"],"is_preprint":false},{"year":2024,"finding":"Prior to radiation exposure, CUL4B inhibits ubiquitination of PSME3, leading to PSME3 accumulation that negatively regulates p53-mediated apoptosis. After radiation, CUL4B dissociates from PSME3 and translocates to γH2AX foci in the nucleus, where it impedes DNA damage repair by inhibiting BRCA1 phosphorylation and RAD51, augmenting p53-mediated apoptosis.","method":"In vivo and in vitro intestinal models, co-IP for CUL4B-PSME3 interaction, BRCA1 phosphorylation and RAD51 immunoblotting, γH2AX co-localization by immunofluorescence","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing CUL4B-PSME3 interaction, multiple pathway readouts, dynamic relocalization demonstrated, single lab","pmids":["38689033"],"is_preprint":false},{"year":2024,"finding":"CUL4B protects kidneys from acute injury by promoting polyubiquitination and proteasomal degradation of p53, thereby suppressing p53-dependent PAI-1 expression. CUL4B-deficient kidneys show exacerbated apoptosis and inflammation upon cisplatin or ischemia-reperfusion injury; inhibition of PAI-1 or p53 prevents this aggravation.","method":"Kidney-specific Cul4b KO mice, cisplatin and IR injury models, p53 ubiquitination assay, PAI-1 and p53 inhibition rescue experiments, transcriptome analysis","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ubiquitination assay for p53, conditional KO with pharmacological rescue (PAI-1/p53 inhibition), multiple injury models, transcriptome validation","pmids":["39695153"],"is_preprint":false},{"year":2019,"finding":"CUL4B in macrophages represses miR-194-5p expression; loss of CUL4B in macrophages suppresses their migration, adhesion, and renal infiltration by elevating miR-194-5p, which targets and reduces integrin α9 (ITGA9). High glucose upregulates CUL4B in macrophages in diabetic conditions.","method":"Myeloid-specific Cul4b KO mice with diabetic kidney disease models, miR-194-5p/ITGA9 pathway analysis, macrophage migration/adhesion assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — conditional KO with two DKD mouse models, pathway epistasis (miR-194-5p/ITGA9), in vitro and in vivo validation","pmids":["37224018"],"is_preprint":false},{"year":2019,"finding":"Small molecule TSC01682 specifically disrupts the CUL4B-DDB1 protein-protein interaction, preventing CRL4B complex assembly. TSC01682 treatment decreases CRL4B components DCAF11 and DCAF13, and increases the CRL4B substrates p21 and PTEN by inhibiting their ubiquitination, consistent with CUL4B-DDB1 interaction being required for substrate ubiquitination.","method":"In vitro high-throughput screening (yeast), Co-IP in osteosarcoma cells, p21/PTEN ubiquitination assay, xenograft tumor model","journal":"American journal of cancer research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — HTS-identified compound validated in cells, ubiquitination assay demonstrating substrate stabilization upon complex disruption, in vivo xenograft validation","pmids":["31598391"],"is_preprint":false},{"year":2020,"finding":"CUL4B contributes to colorectal cancer stemness by coordinating with PRC2 to epigenetically repress miR34a expression, leading to upregulation of MYCN and NOTCH1 (miR34a targets). Inhibition of CUL4B in patient-derived tumor organoids reduces sphere formation and metastatic capacity.","method":"RNAi in cell lines and patient-derived organoids, ChIP for CUL4B/PRC2 at miR34a locus, sphere formation assays","journal":"Oncogenesis","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating direct epigenetic repression, patient-derived organoid validation, multiple cancer biology readouts","pmids":["32054830"],"is_preprint":false},{"year":2021,"finding":"CUL4B promotes temozolomide resistance in glioblastoma by coordinating with HDAC to co-occupy the CDKN1A (p21) promoter and epigenetically silence CDKN1A transcription, thereby attenuating TMZ-induced cellular senescence.","method":"ChIP demonstrating CUL4B and HDAC co-occupancy at CDKN1A promoter, senescence β-galactosidase assay, CUL4B KD/OE in GBM cells","journal":"Frontiers in oncology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ChIP demonstrating direct promoter co-occupancy, senescence functional readout, gain- and loss-of-function, single lab with multiple orthogonal methods","pmids":["33869025"],"is_preprint":false},{"year":2025,"finding":"CUL4B drives thyroid cancer dedifferentiation by promoting ubiquitination of ARID1A (a SWI/SNF complex subunit), leading to its degradation and decreased expression of the differentiation marker PAX8.","method":"In vivo TC models, RNA-seq, Co-IP and ubiquitination assay for CUL4B-ARID1A, immunohistochemistry, in vitro functional experiments","journal":"Translational oncology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ubiquitination assay establishing ARID1A as substrate, in vivo model, mechanistic pathway from ubiquitination to PAX8 downregulation, multiple methods","pmids":["40203790"],"is_preprint":false},{"year":2021,"finding":"THAP7-AS1 lncRNA interacts with the N-terminal 1-50 amino acid region (NLS) of CUL4B and promotes the interaction between the NLS and importin α1, thereby facilitating CUL4B nuclear import. Nuclear CUL4B then represses miR-22-3p and miR-320a by catalyzing H2AK119ub1 and coordinating EZH2-mediated H3K27me3.","method":"Co-IP/RIP for THAP7-AS1-CUL4B interaction, NLS domain mapping, importin α1 interaction assay, ChIP for H2AK119ub1 and H3K27me3","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/domain mapping and ChIP, multiple orthogonal methods, but the nuclear import mechanism adds to the known NLS/importin interaction rather than being entirely novel","pmids":["34608273"],"is_preprint":false},{"year":2016,"finding":"CUL4B promotes invasion and metastasis of gastric cancer by epigenetically repressing miR-125a expression, leading to HER2 upregulation and subsequent activation of PI3K/AKT signaling. HER2 inhibitors reverse CUL4B-induced EMT.","method":"ChIP for epigenetic marks at miR-125a locus, HER2 inhibitor treatment, gain- and loss-of-function experiments, xenograft metastasis model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP for epigenetic repression, pharmacological rescue with HER2 inhibitors, in vivo xenograft validation, single lab","pmids":["29106389"],"is_preprint":false},{"year":2023,"finding":"CUL4B directly interacts with the promoter of Csf3 (encoding G-CSF) by coordinating with PRC2, epigenetically repressing G-CSF expression. CUL4B deletion in intestinal epithelium epigenetically activates G-CSF, promoting MDSC recruitment and ApcMin/+ adenoma formation.","method":"ChIP for CUL4B/PRC2 at Csf3 promoter, ApcMin/+;Cul4bΔIEC mouse model, MDSC depletion rescue, organoid co-culture with MDSCs","journal":"Neoplasia","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating direct CUL4B binding at Csf3 promoter, conditional KO mouse model, MDSC rescue experiments, multiple orthogonal methods","pmids":["38761506"],"is_preprint":false}],"current_model":"CUL4B is an X chromosome-encoded scaffold protein that assembles CUL4B-RING E3 ubiquitin ligase (CRL4B) complexes with DDB1, RBX1/ROC1, and various DCAF substrate receptors; it ubiquitinates diverse substrates for proteasomal degradation (cyclin E, TSC2, p53, HUWE1, PPARγ, INSL6, ARID1A, MEN1 via DCAF7, UTX via DDB1-COP1) and mono-ubiquitinates H2AK119 in concert with PRC2/HDAC complexes to epigenetically silence tumor suppressors and microRNAs; its unique N-terminal NLS (KKRK, aa 37-40) binds importins and is required for nuclear localization, and the N-terminal domain undergoes mitosis-specific phosphorylation that recruits novel DCAFs (LIS1, WDR1) and is essential for spindle positioning and brain development; loss of CUL4B causes embryonic lethality in mice (due to extra-embryonic tissue failure) and X-linked intellectual disability in humans through multiple mechanisms including PP2A-dependent inhibition of AKT/ERK in neural progenitors."},"narrative":{"mechanistic_narrative":"CUL4B is the scaffold subunit of a cullin-RING E3 ubiquitin ligase (CRL4B) that assembles with DDB1, RBX1/ROC1, and interchangeable DCAF substrate receptors to drive both proteasomal degradation of specific substrates and epigenetic gene silencing through chromatin modification [PMID:17273978, PMID:37679762]. A nonsense mutation truncating its C-terminal catalytic domain abolishes ligase function and causes X-linked intellectual disability, establishing the C-terminus as essential for catalysis [PMID:17273978]. As a degradative ligase, CRL4B targets a broad substrate set in a NEDD8-dependent manner — cyclin E and TSC2 (the latter activating mTOR signaling) [PMID:23348097], p53 [PMID:25464270, PMID:39695153], the COP9 signalosome component Jab1/CSN5 [PMID:23357576], HUWE1 [PMID:25883150], PPARγ [PMID:27899484], INSL6 [PMID:26846852], MEN1 via DCAF7 [PMID:36939378], the histone demethylase UTX via a DDB1-COP1 module [PMID:37679762], and ARID1A [PMID:40203790] — coupling it to cell-cycle progression, metabolism, stress responses, and tumor differentiation. In parallel, CRL4B acts as a chromatin-modifying repressor: it catalyzes monoubiquitination of H2AK119 and coordinates with PRC2 (H3K27me3) and HDAC complexes to silence tumor-suppressor microRNAs and target genes, including miR-194 (a reciprocal feedback partner) [PMID:28164432], miR-372/373 [PMID:32127645], miR-34a [PMID:32054830], and the CDKN1A/p21 promoter [PMID:33869025], thereby activating oncogenic Wnt/β-catenin, PI3K/AKT, and Notch pathways [PMID:25430888, PMID:32127645]. CUL4B carries a unique N-terminal NLS (KKRK, aa 37-40) that binds importin α isoforms and is required for nuclear localization and proliferation [PMID:19801544], and its N-terminal extension is heavily phosphorylated during mitosis to recruit the noncanonical DCAFs LIS1 and WDR1, controlling spindle positioning and forebrain development [PMID:37365982]. CUL4B is essential for mouse embryonic development through a requirement in extra-embryonic tissues [PMID:22453236, PMID:22606329], and in neural progenitors its loss derepresses PP2A regulatory subunits PPP2R2B/PPP2R2C, inhibiting AKT/ERK to cause premature cell-cycle exit and precocious neuronal differentiation underlying X-linked intellectual disability [PMID:38331954].","teleology":[{"year":2007,"claim":"Established CUL4B as a cullin-RING E3 ligase scaffold whose C-terminal catalytic domain is essential, linking its loss of function to human disease.","evidence":"Mutation analysis of an XLID nonsense allele (p.R388X) with NMD and X-inactivation analysis in patient cells","pmids":["17273978"],"confidence":"Medium","gaps":["Did not define substrate receptors or specific substrates","Mechanism connecting ligase loss to intellectual disability not addressed"]},{"year":2009,"claim":"Resolved why CUL4B differs from other cullins by mapping a unique N-terminal NLS required for nuclear localization and proliferation, and identified cyclin E as a degradation substrate.","evidence":"NLS deletion mutants, importin α1/α3/α5 binding assays, subcellular fractionation, RNAi and cell-cycle analysis","pmids":["19801544"],"confidence":"High","gaps":["DCAF receptor mediating cyclin E recognition not identified","Did not address how nuclear/cytoplasmic partitioning is regulated"]},{"year":2012,"claim":"Demonstrated that CUL4B is required for embryonic viability and localized its essential function to extra-embryonic tissues, distinguishing it from the embryo-intrinsic role.","evidence":"Conventional and epiblast-specific (Sox2-Cre) Cul4b knockout mice with cyclin E immunoblotting","pmids":["22453236","22606329"],"confidence":"High","gaps":["Extra-embryonic substrate(s) driving lethality not defined","Mechanistic basis of tissue specificity unresolved"]},{"year":2013,"claim":"Expanded the degradative substrate repertoire (Jab1/CSN5, TSC2, cyclin E) and connected CRL4B to mTOR signaling and DNA replication licensing through CDC6/CDK2.","evidence":"In vitro/in vivo ubiquitination assays, Co-IP, Cul4b-deficient MEFs, neocortical neuron expression, chromatin fractionation, miRNA manipulation","pmids":["23357576","23348097","23479742"],"confidence":"High","gaps":["DCAF receptors for these substrates not specified","Whether degradative and replication-licensing functions are mechanistically separable unknown"]},{"year":2014,"claim":"Identified p53 as a CRL4B substrate, defining a role in suppressing stress-induced senescence via a p53-ROS feedback loop.","evidence":"Gain/loss-of-function with p53 ubiquitination assay, H2O2 treatment, ROS and senescence β-gal readouts in fibroblasts","pmids":["25464270"],"confidence":"High","gaps":["Distinction between stress-induced and replicative senescence regulation not fully mechanistic","DCAF receptor for p53 not identified"]},{"year":2015,"claim":"Established CRL4B as an epigenetic repressor that recruits PRC2 to silence pathway antagonists, and extended its developmental roles to neural progenitor astrocytogenesis and HUWE1-controlled apoptosis.","evidence":"ChIP for PRC2/H3K27me3, rescue/epistasis experiments, nervous-system-specific KO mice, pharmacological PTGDS inhibition, in vitro ubiquitination","pmids":["25430888","26025376","25883150"],"confidence":"High","gaps":["Mechanism of PRC2 recruitment to specific loci unresolved","Relationship between degradative and chromatin-silencing activities at the complex level unclear"]},{"year":2016,"claim":"Defined tissue-specific physiological roles via conditional knockouts (adipocyte PPARγ regulation; germ cell INSL6 degradation in spermatogenesis), with mass-spectrometry substrate identification.","evidence":"Adipocyte- and germ-cell-specific conditional KO mice, ubiquitination assays, mass spectrometry, metabolic and sperm phenotyping, EM of flagella","pmids":["27899484","26846852"],"confidence":"High","gaps":["DCAF receptors for PPARγ and INSL6 not defined","Non-cell-autonomous niche mechanism in spermatogenesis incompletely resolved"]},{"year":2017,"claim":"Demonstrated that CRL4B directly catalyzes H2AK119 monoubiquitination at microRNA loci, establishing a catalytic chromatin mechanism and a miR-194 double-negative feedback loop downstream of p53.","evidence":"ChIP for H2AK119ub/H3K27me3 at miR-194 cluster, 3'-UTR luciferase reporter, RNAi, xenografts","pmids":["28164432"],"confidence":"High","gaps":["How H2AK119ub coordinates with PRC2 H3K27me3 mechanistically unresolved","Locus-specificity determinants of CRL4B chromatin targeting unknown"]},{"year":2019,"claim":"Revealed immune-regulatory roles in which CRL4B epigenetically tunes myeloid and T-cell programs (PTEN, IL-6, miR-372/373, miR-194-5p) and defined DCAF1 as the T-cell substrate receptor linked to DNA-damage response.","evidence":"Myeloid- and T-cell-specific conditional KOs, ChIP at target promoters, pharmacological/blocking rescues, Co-IP and mass spectrometry, DNA damage and SMC1A phosphorylation assays","pmids":["31729464","31235785","32127645","37224018","33524014"],"confidence":"High","gaps":["How CRL4B switches between degradative DCAF1-dependent and chromatin-repressive modes unclear","Direct chromatin substrates versus indirect effects not always distinguished"]},{"year":2021,"claim":"Broadened CRL4B oncogenic and viral roles (tamoxifen resistance via miR-32-5p/ER-α36, HBx stabilization to promote HBV, TMZ resistance via CDKN1A silencing) and refined nuclear import via THAP7-AS1 lncRNA enhancing NLS-importin α1 binding.","evidence":"ChIP at miR/promoter loci, dominant-negative and KD/OE mutants, Co-IP/RIP/IF, cycloheximide chase, in vivo HBV and tumor models","pmids":["33638154","33969670","33869025","34608273","34146543"],"confidence":"High","gaps":["Generality of lncRNA-assisted nuclear import beyond tested contexts unknown","Whether HBx stabilization reflects substrate competition or altered complex composition unresolved"]},{"year":2023,"claim":"Connected mitosis-specific N-terminal phosphorylation to recruitment of noncanonical DCAFs (LIS1, WDR1) controlling spindle positioning, and defined additional DCAF-based substrate complexes (DCAF7-MEN1, DDB1-COP1-UTX) and tumor-microenvironment chromatin targets (Cxcl2, Csf3).","evidence":"Phosphoproteomics, Co-IP of LIS1/WDR1/DCAF7/COP1 with DDB1, mutagenesis, live imaging, forebrain organoids, ChIP, conditional KO tumor models","pmids":["37365982","36939378","37679762","37653114","38761506","37925424"],"confidence":"High","gaps":["Kinase(s) phosphorylating the N-terminal extension not identified","Structural basis of phosphorylation-dependent DCAF selection unresolved"]},{"year":2024,"claim":"Provided a patient-iPSC mechanistic model of XLID showing that CRL4B represses PP2A regulatory subunits (PPP2R2B/C) via H2AK119ub, sustaining AKT/ERK to prevent premature neuronal differentiation, and added p53/PSME3-dependent radiation and kidney-injury roles.","evidence":"Patient iPSC-derived neurons/organoids, ChIP for H2AK119ub, PP2A activity assay, AKT/ERK and PP2A pharmacological rescue, kidney conditional KO injury models, Co-IP for CUL4B-PSME3","pmids":["38331954","38689033","39695153"],"confidence":"High","gaps":["How a single XLID lesion produces both degradative and epigenetic deficits not integrated","PSME3 relocalization to γH2AX foci mechanism incompletely defined (Medium-confidence)"]},{"year":2025,"claim":"Extended CRL4B substrate degradation to chromatin-remodeling factor ARID1A, linking it to thyroid cancer dedifferentiation via PAX8 downregulation.","evidence":"Co-IP and ubiquitination assay for CUL4B-ARID1A, in vivo thyroid cancer models, RNA-seq, IHC","pmids":["40203790"],"confidence":"High","gaps":["DCAF receptor recognizing ARID1A not identified","Whether ARID1A degradation and chromatin repression act on overlapping gene programs unknown"]},{"year":null,"claim":"It remains unresolved how the CRL4B complex partitions between its degradative substrate-receptor repertoire and its catalytic chromatin-silencing activity, and what determines locus- and substrate-specific targeting in different tissues.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model integrating DCAF substrate selection with H2AK119ub chromatin function","DCAF receptors for most degradative substrates remain unidentified","Rules governing context-specific microRNA/gene-locus targeting unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,3,6,8,9,19,27,36]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[1,6,8,33]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[13,14,29,34,35]},{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[13,14,29]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,27,19]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,37]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]},{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[13,29,18,30]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,3,6,8,15,19,27,36]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[13,14,29,34,35]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,2,18,26]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,5,11,21,29]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[11,12,22,23,25]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,10,18,21,28]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,21,14,16]}],"complexes":["CRL4B (CUL4B-DDB1-RBX1/ROC1)","CUL4B-DDB1-COP1","CUL4B-PRC2","CUL4B-DCAF1"],"partners":["DDB1","RBX1","COP1","DCAF1","DCAF7","LIS1","WDR1","PSME3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q13620","full_name":"Cullin-4B","aliases":[],"length_aa":913,"mass_kda":104.0,"function":"Core component of multiple cullin-RING-based E3 ubiquitin-protein ligase complexes which mediate the ubiquitination and subsequent proteasomal degradation of target proteins (PubMed:14578910, PubMed:16322693, PubMed:16678110, PubMed:18593899, PubMed:22118460, PubMed:29779948, PubMed:30166453, PubMed:33854232, PubMed:33854239, PubMed:25970626). The functional specificity of the E3 ubiquitin-protein ligase complex depends on the variable substrate recognition subunit (PubMed:14578910, PubMed:16678110, PubMed:18593899, PubMed:22118460, PubMed:29779948). CUL4B may act within the complex as a scaffold protein, contributing to catalysis through positioning of the substrate and the ubiquitin-conjugating enzyme (PubMed:14578910, PubMed:16678110, PubMed:18593899, PubMed:22118460). Plays a role as part of the E3 ubiquitin-protein ligase complex in polyubiquitination of CDT1, histone H2A, histone H3 and histone H4 in response to radiation-induced DNA damage (PubMed:14578910, PubMed:16678110, PubMed:18593899). Targeted to UV damaged chromatin by DDB2 and may be important for DNA repair and DNA replication (PubMed:16678110). A number of DCX complexes (containing either TRPC4AP or DCAF12 as substrate-recognition component) are part of the DesCEND (destruction via C-end degrons) pathway, which recognizes a C-degron located at the extreme C terminus of target proteins, leading to their ubiquitination and degradation (PubMed:29779948). The DCX(AMBRA1) complex is a master regulator of the transition from G1 to S cell phase by mediating ubiquitination of phosphorylated cyclin-D (CCND1, CCND2 and CCND3) (PubMed:33854232, PubMed:33854239). The DCX(AMBRA1) complex also acts as a regulator of Cul5-RING (CRL5) E3 ubiquitin-protein ligase complexes by mediating ubiquitination and degradation of Elongin-C (ELOC) component of CRL5 complexes (PubMed:30166453). Required for ubiquitination of cyclin E (CCNE1 or CCNE2), and consequently, normal G1 cell cycle progression (PubMed:16322693, PubMed:19801544). Regulates the mammalian target-of-rapamycin (mTOR) pathway involved in control of cell growth, size and metabolism (PubMed:18235224). Specific CUL4B regulation of the mTORC1-mediated pathway is dependent upon 26S proteasome function and requires interaction between CUL4B and MLST8 (PubMed:18235224). With CUL4A, contributes to ribosome biogenesis (PubMed:26711351)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q13620/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CUL4B","classification":"Not Classified","n_dependent_lines":26,"n_total_lines":1208,"dependency_fraction":0.02152317880794702},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"NUCKS1","stoichiometry":10.0},{"gene":"DDB1","stoichiometry":4.0},{"gene":"CAPZB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CUL4B","total_profiled":1310},"omim":[{"mim_id":"620524","title":"DDB1- AND CUL4-ASSOCIATED FACTOR 16; DCAF16","url":"https://www.omim.org/entry/620524"},{"mim_id":"619763","title":"WD AND TETRATRICOPEPTIDE REPEATS PROTEIN 1; WDTC1","url":"https://www.omim.org/entry/619763"},{"mim_id":"616704","title":"COMM DOMAIN-CONTAINING PROTEIN 10; COMMD10","url":"https://www.omim.org/entry/616704"},{"mim_id":"616656","title":"COMM DOMAIN-CONTAINING PROTEIN 8; COMMD8","url":"https://www.omim.org/entry/616656"},{"mim_id":"603137","title":"CULLIN 4A; CUL4A","url":"https://www.omim.org/entry/603137"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CUL4B"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q13620","domains":[{"cath_id":"1.20.1310.10","chopping":"212-337","consensus_level":"high","plddt":91.4782,"start":212,"end":337},{"cath_id":"1.20.1310.10","chopping":"462-653","consensus_level":"medium","plddt":92.4129,"start":462,"end":653},{"cath_id":"-","chopping":"654-716","consensus_level":"medium","plddt":90.047,"start":654,"end":716},{"cath_id":"3.30.230.130","chopping":"729-831","consensus_level":"medium","plddt":89.0862,"start":729,"end":831},{"cath_id":"1.10.10.10","chopping":"835-912","consensus_level":"high","plddt":91.2955,"start":835,"end":912}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13620","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q13620-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q13620-F1-predicted_aligned_error_v6.png","plddt_mean":78.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CUL4B","jax_strain_url":"https://www.jax.org/strain/search?query=CUL4B"},"sequence":{"accession":"Q13620","fasta_url":"https://rest.uniprot.org/uniprotkb/Q13620.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q13620/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13620"}},"corpus_meta":[{"pmid":"17236139","id":"PMC_17236139","title":"Mutations in CUL4B, which encodes a ubiquitin E3 ligase subunit, cause an X-linked mental retardation syndrome associated with aggressive outbursts, seizures, relative macrocephaly, central obesity, hypogonadism, pes cavus, and tremor.","date":"2007","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17236139","citation_count":195,"is_preprint":false},{"pmid":"34608273","id":"PMC_34608273","title":"lncRNA THAP7-AS1, transcriptionally activated by SP1 and post-transcriptionally stabilized by METTL3-mediated m6A modification, exerts oncogenic properties by improving CUL4B entry into the nucleus.","date":"2021","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/34608273","citation_count":163,"is_preprint":false},{"pmid":"17273978","id":"PMC_17273978","title":"Mutation in CUL4B, which encodes a member of cullin-RING ubiquitin ligase complex, causes X-linked mental retardation.","date":"2007","source":"American journal of human 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Unlike CUL4A and other cullins which carry NLS in their C-termini, this N-terminal NLS is unique to CUL4B. NLS-deleted CUL4B localizes to the cytoplasm and fails to promote cell proliferation. CUL4B promotes ubiquitination and degradation of cyclin E, and RNAi silencing leads to overaccumulation of cyclin E, prolonged S phase, and inhibited cell proliferation.\",\n      \"method\": \"RNAi silencing, NLS deletion mutants, importin binding assays, subcellular fractionation, cell cycle analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional assays, NLS mapping with mutagenesis, importin binding, multiple orthogonal methods in single study replicated by other labs\",\n      \"pmids\": [\"19801544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CUL4B is a scaffold protein that organizes a cullin-RING (E3) ubiquitin ligase complex. A nonsense mutation (p.R388X) truncates the C-terminal catalytic domain and causes nonsense-mediated mRNA decay, demonstrating that the C-terminal domain is essential for ligase function.\",\n      \"method\": \"Mutation analysis, mRNA expression in patient leukocytes, X-chromosome inactivation analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined molecular consequence (NMD, truncation of catalytic domain), single study\",\n      \"pmids\": [\"17273978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CUL4B promotes DNA replication licensing by positively regulating CDC6 (a replication licensing factor) through a CDK2-dependent mechanism: CUL4B represses miR-372 and miR-373, which target CDK2, thereby elevating CDK2 levels; CDK2 then phosphorylates CDC6, protecting it from APC(CDH1)-mediated degradation, which in turn promotes loading of MCM2 onto chromatin.\",\n      \"method\": \"RNAi knockdown, chromatin fractionation for MCM2 loading, miRNA overexpression/inhibition, immunoblotting\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods establishing a complete pathway cascade, epistasis experiments\",\n      \"pmids\": [\"23479742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CUL4B ubiquitin ligase targets Jab1/CSN5 (a component of the COP9 signalosome) for polyubiquitination and proteasomal degradation. The DDB1-CUL4B-ROC1 complex is required for this degradation, which is independent of CUL4A. Loss of CUL4B leads to Jab1 accumulation and abnormal upregulation of BMP signaling.\",\n      \"method\": \"RNAi, in vitro and in vivo ubiquitination assays, Co-IP, Cul4b-deficient mouse embryonic fibroblasts\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitination assay plus in vivo validation in KO cells, Co-IP demonstrating complex, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"23357576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CUL4B promotes ubiquitination and degradation of TSC2 and cyclin E in neocortical neurons. XLID mutants (R388X, R572C, V745A) fail to promote ubiquitination/degradation of TSC2 or cyclin E. By targeting TSC2 for degradation, wild-type CUL4B positively regulates mTOR signaling (increased p-mTOR, p-p70S6K, p-4E-BP1); CUL4B knockdown or XLID mutants fail to activate mTOR.\",\n      \"method\": \"Adenovirus-mediated expression in neocortical neurons, shRNA knockdown, immunoblotting for ubiquitination and mTOR pathway substrates\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — overexpression + knockdown + XLID mutant analysis with multiple substrates and pathway readouts in primary neurons\",\n      \"pmids\": [\"23348097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CUL4B activates Wnt/β-catenin signaling in HCC by epigenetically silencing Wnt pathway antagonists (DKK1, PPP2R2B). CRL4B promotes recruitment/retention of PRC2 at promoters of Wnt antagonists, and CUL4B knockdown decreases PRC2 components and H3K27me3 at these promoters. CUL4B also protects β-catenin from GSK3-mediated degradation through this mechanism.\",\n      \"method\": \"RNAi knockdown, ChIP for PRC2/H3K27me3, rescue experiments with simultaneous knockdown of PPP2R2B, xenograft models\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP demonstrating epigenetic mechanism, rescue experiments with epistasis, in vitro and in vivo validation\",\n      \"pmids\": [\"25430888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CRL4B is required for proteasomal degradation of HUWE1 in response to DNA damage. CUL4B is activated in a NEDD8-dependent manner and ubiquitinates HUWE1 in vitro and in vivo. CUL4B depletion stabilizes HUWE1, which accelerates MCL-1 degradation and increases apoptosis; these phenotypes are rescued by simultaneous HUWE1 depletion.\",\n      \"method\": \"In vitro ubiquitination assay, RNAi, epistasis (double knockdown rescue), immunoblotting\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitination assay, genetic epistasis with double knockdown rescue, multiple orthogonal methods\",\n      \"pmids\": [\"25883150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CUL4B is essential for embryonic development; Cul4b null mouse embryos die before E9.5 with severe developmental arrest. Cyclin E (a CRL4B substrate) accumulates in Cul4b null embryos. Epiblast-specific deletion of Cul4b prevents lethality, demonstrating that CUL4B's essential function is in extra-embryonic tissues rather than the embryo proper.\",\n      \"method\": \"Cul4b knockout mouse generation, conditional epiblast-specific deletion (Sox2-Cre), immunoblotting for cyclin E\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent KO studies (PMIDs 22606329 and 22453236) with conditional rescue demonstrating tissue-specific requirement\",\n      \"pmids\": [\"22453236\", \"22606329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CUL4B negatively regulates PPARγ by promoting its polyubiquitination and proteasomal degradation. Depletion of CUL4B leads to upregulation of PPARγ-regulated genes and facilitates adipogenesis. Adipocyte-specific Cul4b KO mice show increased adipogenesis and fat accumulation but improved insulin sensitivity and glucose tolerance.\",\n      \"method\": \"Adipocyte-specific conditional KO mouse, PPARγ ubiquitination assay, high-fat diet metabolic phenotyping\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ubiquitination assay establishing direct substrate relationship, in vivo KO model with metabolic phenotype, single lab multiple orthogonal methods\",\n      \"pmids\": [\"27899484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CUL4B performs both cell-autonomous and non-cell-autonomous functions in spermatogenesis. In germ cells, CUL4B directly polyubiquitinates and degrades INSL6 (identified by mass spectrometry); loss of germ cell CUL4B impairs sperm motility due to reduced mitochondrial activity and glycolysis, and defective flagellar axoneme/outer dense fiber arrangement. In somatic cells, CUL4B maintains the spermatogonial stem cell niche.\",\n      \"method\": \"Germ cell-specific conditional KO, global KO, mass spectrometry substrate identification, polyubiquitination assay, sperm ATP measurement, electron microscopy of flagella\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mass spectrometry substrate ID with ubiquitination assay, two conditional KO models with distinct phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"26846852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CUL4B represses GFAP expression in neural progenitor cells by epigenetically silencing PTGDS. Loss of Cul4b increases PTGDS expression, elevating prostaglandin D2, which promotes astrocyte (GFAP+) generation. CUL4B/PRC2 complex targets and represses Ptgds; pharmacological inhibition of PTGDS or shRNA knockdown attenuates the increased GFAP+ cells from Cul4b-null NPCs.\",\n      \"method\": \"Nervous system-specific Cul4b KO mice, in vitro NPC culture, ChIP for CUL4B/PRC2 at Ptgds, pharmacological PTGDS inhibition, shRNA knockdown\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO plus ChIP demonstrating direct epigenetic regulation of PTGDS, pharmacological rescue, multiple methods\",\n      \"pmids\": [\"26025376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CUL4B unexpectedly functions as a negative regulator of myeloid-derived suppressor cells (MDSCs). Hematopoietic-specific CUL4B ablation (Tek-Cre) increases MDSC accumulation via downregulation of the AKT/β-catenin pathway. CUL4B represses phosphatases PP2A and PHLPP1/2 (which dephosphorylate/inactivate AKT) to sustain AKT pathway activation.\",\n      \"method\": \"Hematopoietic-specific conditional KO (Tek-Cre), MDSC quantification, AKT pathway analysis, multiple tumor models\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with defined molecular mechanism (PP2A/PHLPP1/2 repression → AKT), single lab with multiple tumor models and mechanistic pathway placement\",\n      \"pmids\": [\"26450912\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CUL4B negatively regulates TLR-triggered inflammatory responses in macrophages by epigenetically repressing transcription of Pten, thereby maintaining the anti-inflammatory PI3K-AKT-GSK3β pathway. Deletion of CUL4B in macrophages upregulates PTEN, leading to increased GSK3β activity and excessive proinflammatory cytokine production.\",\n      \"method\": \"Myeloid cell-specific Cul4b KO mice, LPS/pathogen challenge, GSK3β inhibitor rescue, ChIP/epigenetic analysis of Pten promoter\",\n      \"journal\": \"Cellular & molecular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with pharmacological rescue (GSK3β inhibitor) and ChIP for epigenetic mechanism at Pten, in vivo infection models\",\n      \"pmids\": [\"31729464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CUL4B epigenetically represses miR-194 by catalyzing monoubiquitination of H2AK119 and coordinating with PRC2 to promote H3K27me3 at the miR-194 gene cluster. miR-194 in turn targets the 3'-UTR of CUL4B, creating a double-negative feedback loop. CUL4B also represses miR-194 downstream of p53.\",\n      \"method\": \"ChIP for H2AK119ub and H3K27me3 at miR-194 locus, 3'-UTR luciferase reporter assay, RNAi, xenograft tumor formation\",\n      \"journal\": \"Molecular oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ChIP demonstrating direct epigenetic modification at miR-194 locus plus 3'-UTR reporter assay, multiple orthogonal methods\",\n      \"pmids\": [\"28164432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL4B renders breast cancer cells tamoxifen-resistant through a miR-32-5p/ER-α36 axis. CRL4B epigenetically represses miR-32-5p transcription by catalyzing H2AK119 monoubiquitination and coordinating with PRC2 and HDAC complexes to promote H3K27me3 at the miR-32-5p promoter, leading to upregulation of ER-α36.\",\n      \"method\": \"ChIP for H2AK119ub and H3K27me3 at miR-32-5p promoter, dominant-negative CUL4B mutant, pharmacological inhibition of CRL4B/PRC2/HDAC, in vitro and in vivo tamoxifen sensitivity assays\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ChIP demonstrating direct epigenetic mechanism, dominant-negative mutant, pharmacological inhibition, in vitro and in vivo validation\",\n      \"pmids\": [\"33638154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CUL4B suppresses stress-induced cellular senescence by promoting p53 ubiquitination and proteasomal degradation in normal human fibroblasts exposed to oxidative stress (H2O2), thereby dampening a p53-ROS positive feedback loop that drives senescence. CUL4B is downregulated in stress-induced (but not replicative) senescent cells.\",\n      \"method\": \"Ectopic CUL4B expression, RNAi, H2O2 treatment, p53 ubiquitination assay, ROS measurement, senescence β-galactosidase assay\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ubiquitination assay for p53 as substrate, gain- and loss-of-function, multiple orthogonal senescence readouts, single lab\",\n      \"pmids\": [\"25464270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL4B promotes HBV replication by interacting with the viral protein HBx and inhibiting HBx ubiquitination and proteasomal degradation, thereby stabilizing HBx. This interaction was demonstrated by immunoprecipitation and immunofluorescence co-localization.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-staining, cycloheximide chase assay, in vivo ubiquitination assay, Cul4b transgenic and conditional KO mice with hydrodynamic HBV model\",\n      \"journal\": \"Cancer biology & medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — Co-IP demonstrating direct interaction, in vivo ubiquitination assay, transgenic and KO mouse models, multiple orthogonal methods in single study\",\n      \"pmids\": [\"33969670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TCDD-activated AHR is partially degraded via CUL4B-mediated ubiquitination; loss of CUL4B partially prevents AHR degradation after TCDD exposure. TiPARP additionally promotes AHR nuclear export preceding degradation; knockdown of TiPARP in CUL4B-null cells completely abolishes AHR degradation, indicating CUL4B and TiPARP cooperate to restrain AHR activity.\",\n      \"method\": \"Cul4b-null MEF cell line, TiPARP knockdown in null cells, TCDD treatment, AHR protein level and transcriptional activity measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO cell line with TiPARP knockdown epistasis, functional transcriptional readout, multiple conditions tested\",\n      \"pmids\": [\"34146543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The unique N-terminal extension of CUL4B is heavily phosphorylated during mitosis. Phosphorylation triggers chromatin exclusion of CUL4B while promoting binding to actin regulators and to two previously unrecognized CUL4B-specific DCAFs, LIS1 and WDR1, which interact with DDB1 in a phosphorylation-dependent manner. CUL4B phosphorylation is required for efficient mitosis progression (spindle positioning, cortical tension). The XLID mutation CUL4B-P50L perturbs this phosphorylation pattern. CUL4B is required for developing stable ventricular structures in human forebrain organoids.\",\n      \"method\": \"Phosphoproteomic analysis, Co-immunoprecipitation of LIS1/WDR1 with DDB1, mutagenesis of phosphorylation sites, live imaging for spindle positioning/cortical tension, human forebrain organoid model\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — phosphoproteomic identification, Co-IP with biochemical validation, mutagenesis, organoid model, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"37365982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CUL4B and DCAF7 form an E3 ligase complex that promotes MEN1 protein degradation by binding MEN1 and catalyzing its ubiquitination. Neddylation pathway activation is required upstream; neddylation inhibitor MLN4924 induces MEN1 accumulation. DCAF7 downregulation reverses everolimus resistance in PanNET cells in a MEN1-dependent manner.\",\n      \"method\": \"Co-IP, RNAi knockdown, neddylation inhibitor (MLN4924), in vitro ubiquitination, DCAF7/MEN1 double knockdown epistasis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — Co-IP establishing complex, ubiquitination assay, epistasis (double KD rescue), pharmacological validation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"36939378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CUL4B directly binds to the promoter of Cxcl2 and epigenetically represses its transcription. In KRAS-mutant lung tumors, CUL4B deletion increases CXCL2 expression, which promotes CXCR2-dependent MDSC recruitment to the tumor microenvironment.\",\n      \"method\": \"ChIP for CUL4B at Cxcl2 promoter, CUL4B KO/KD in autochthonous and transplantable KRAS-mutant tumor models, MDSC quantification, MDSC targeting experiments\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating direct promoter binding, in vivo KO tumor models with mechanistic rescue (MDSC targeting), multiple model systems\",\n      \"pmids\": [\"37653114\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CUL4B mutations (XLID patient-derived) cause premature cell cycle exit and precocious neuronal differentiation of neural progenitor cells, as well as increased synapse formation and enhanced neuronal excitability. Mechanistically, CRL4B complex represses transcription of PPP2R2B and PPP2R2C (PP2A regulatory subunit isoforms) by catalyzing H2AK119 monoubiquitination at their promoters. CUL4B mutations upregulate PP2A activity, inhibiting AKT and ERK, causing premature cell cycle exit; rescue achieved by AKT/ERK activation or PP2A inhibition.\",\n      \"method\": \"Patient iPSC-derived 2D neuronal cultures and cerebral organoids, ChIP for H2AK119ub, PP2A activity assay, AKT/ERK inhibition/activation, pharmacological PP2A inhibition rescue\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — patient iPSC-derived isogenic model, ChIP demonstrating direct epigenetic mechanism, biochemical PP2A activity assay, pharmacological rescue with multiple agents\",\n      \"pmids\": [\"38331954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL4B is required for CD4+ T cell proliferation and survival following TCR stimulation. In T cells, CUL4B preferentially associates with the substrate receptor DCAF1; Cul4b and DCAF1 interact with proteins involved in DNA damage sensing/repair. Cul4b-deficient CD4+ T cells accumulate DNA damage and fail to phosphorylate SMC1A (a downstream DNA damage response event), leading to proliferative failure.\",\n      \"method\": \"Cul4b conditional KO T cells, Co-immunoprecipitation (CUL4B-DCAF1 interaction), mass spectrometry of associated proteins, DNA damage assays, SMC1A phosphorylation analysis\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing CUL4B-DCAF1 complex, KO T cell phenotype with mechanistic DNA damage pathway analysis, mass spectrometry\",\n      \"pmids\": [\"33524014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"c-Myc increases Cul4b protein levels following T cell activation. Cul4b-deficient CD8+ T cells accumulate DNA damage and p21/Cyclin E2, leading to replication stress and proliferative catastrophe. c-Myc supports CD8+ T cell expansion by maintaining genome stability via Cul4b.\",\n      \"method\": \"Cul4b conditional KO CD8+ T cells, in vivo LCMV infection model, p21/Cyclin E2 immunoblotting, DNA damage assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with viral infection model, molecular pathway analysis (p21/Cyclin E2 accumulation), epistasis placing c-Myc upstream of Cul4b\",\n      \"pmids\": [\"37925424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CUL4B variants interact with WDR62, a protein mutated in microcephaly patients with malformations of cortical development, suggesting a functional complex.\",\n      \"method\": \"Co-immunoprecipitation of CUL4B with WDR62\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP, no functional follow-up mechanistic experiments described in abstract\",\n      \"pmids\": [\"25385192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CUL4B epigenetically represses IL-6 transcription in myeloid cells via the CRL4B complex. In CUL4B-deficient MDSCs, elevated IL-6 activates IL-6/STAT3 signaling in tumor cells, rendering them stem cell-like properties.\",\n      \"method\": \"Hematopoietic/myeloid-specific Cul4b KO mice, IL-6 blocking, STAT3 inhibitor, ChIP/epigenetic analysis at IL-6 promoter\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with IL-6 blocking and STAT3 inhibition epistasis, ChIP for epigenetic repression of IL-6 locus\",\n      \"pmids\": [\"31235785\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CUL4B is required for neural progenitor cell mitosis progression. Downregulation of CUL4B arrests NPCs and NT-2 cells in G2/M phase. Three isoforms of CUL4B exist in brain tissue; the larger isoforms (CUL4B-1, -2) are predominantly unneddylated due to their N-terminal extension, while the smaller isoform (CUL4B-3, lacking the N-terminus) is neddylated. Unneddylated CUL4B accumulates during mitosis and inhibits β-catenin degradation in neural stem cell niches.\",\n      \"method\": \"Immunostaining, RNAi knockdown in NPCs/NT-2 cells, cell cycle analysis, neddylation state analysis, brain tissue immunostaining\",\n      \"journal\": \"BMC neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — RNAi with cell cycle phenotype and isoform characterization, single study, some mechanistic inferences from correlation\",\n      \"pmids\": [\"22992378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CUL4B-DDB1-COP1 forms a functional E3 ubiquitin ligase complex responsible for targeting the histone demethylase UTX (KDM6A) for ubiquitination and proteasomal degradation in colorectal cancer cells. Cop1 deficiency in mouse intestinal tissue results in UTX accumulation and restricts tumorigenesis.\",\n      \"method\": \"Co-immunoprecipitation demonstrating CUL4B-DDB1-COP1 complex, immunoblot for UTX degradation, conditional Cop1 KO mouse, spontaneous AOM/DSS CRC model with GSK126 rescue\",\n      \"journal\": \"Experimental hematology & oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — Co-IP establishing complex, in vivo KO model with EZH2 inhibitor epistasis, multiple orthogonal methods\",\n      \"pmids\": [\"37679762\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CUL4B promotes osteogenesis and inhibits adipogenesis of mesenchymal stem cells by epigenetically repressing KLF4 (an adipogenic factor) and C/EBPδ transcription. The CUL4B complex directly binds to Klf4 and Cebpd promoters and represses their transcription. MSC-specific Cul4b KO mice show impaired skeletal development, low bone mass, and increased marrow adipose accumulation.\",\n      \"method\": \"MSC-specific conditional Cul4b KO mice, ChIP for CUL4B complex at Klf4/Cebpd promoters, in vitro osteogenic/adipogenic differentiation assays, ovariectomy model\",\n      \"journal\": \"Bone research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO mouse with multiple in vivo models, ChIP demonstrating direct promoter binding, in vitro differentiation assays\",\n      \"pmids\": [\"37268647\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CUL4B-RING E3 ligase complex represses transcription of miR-372/373 via H2AK119 monoubiquitination at the miR-372/373 gene cluster, leading to upregulation of PIK3CA and activation of AKT signaling, promoting bladder cancer metastasis and stemness.\",\n      \"method\": \"ChIP for H2AK119ub at miR-372/373 locus, 3'-UTR reporter assay for PIK3CA targeting, RNAi, invasion/motility assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ChIP demonstrating direct histone modification at miR-372/373 locus, reporter assay, multiple oncogenic phenotype readouts\",\n      \"pmids\": [\"32127645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Prior to radiation exposure, CUL4B inhibits ubiquitination of PSME3, leading to PSME3 accumulation that negatively regulates p53-mediated apoptosis. After radiation, CUL4B dissociates from PSME3 and translocates to γH2AX foci in the nucleus, where it impedes DNA damage repair by inhibiting BRCA1 phosphorylation and RAD51, augmenting p53-mediated apoptosis.\",\n      \"method\": \"In vivo and in vitro intestinal models, co-IP for CUL4B-PSME3 interaction, BRCA1 phosphorylation and RAD51 immunoblotting, γH2AX co-localization by immunofluorescence\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing CUL4B-PSME3 interaction, multiple pathway readouts, dynamic relocalization demonstrated, single lab\",\n      \"pmids\": [\"38689033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CUL4B protects kidneys from acute injury by promoting polyubiquitination and proteasomal degradation of p53, thereby suppressing p53-dependent PAI-1 expression. CUL4B-deficient kidneys show exacerbated apoptosis and inflammation upon cisplatin or ischemia-reperfusion injury; inhibition of PAI-1 or p53 prevents this aggravation.\",\n      \"method\": \"Kidney-specific Cul4b KO mice, cisplatin and IR injury models, p53 ubiquitination assay, PAI-1 and p53 inhibition rescue experiments, transcriptome analysis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ubiquitination assay for p53, conditional KO with pharmacological rescue (PAI-1/p53 inhibition), multiple injury models, transcriptome validation\",\n      \"pmids\": [\"39695153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CUL4B in macrophages represses miR-194-5p expression; loss of CUL4B in macrophages suppresses their migration, adhesion, and renal infiltration by elevating miR-194-5p, which targets and reduces integrin α9 (ITGA9). High glucose upregulates CUL4B in macrophages in diabetic conditions.\",\n      \"method\": \"Myeloid-specific Cul4b KO mice with diabetic kidney disease models, miR-194-5p/ITGA9 pathway analysis, macrophage migration/adhesion assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with two DKD mouse models, pathway epistasis (miR-194-5p/ITGA9), in vitro and in vivo validation\",\n      \"pmids\": [\"37224018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Small molecule TSC01682 specifically disrupts the CUL4B-DDB1 protein-protein interaction, preventing CRL4B complex assembly. TSC01682 treatment decreases CRL4B components DCAF11 and DCAF13, and increases the CRL4B substrates p21 and PTEN by inhibiting their ubiquitination, consistent with CUL4B-DDB1 interaction being required for substrate ubiquitination.\",\n      \"method\": \"In vitro high-throughput screening (yeast), Co-IP in osteosarcoma cells, p21/PTEN ubiquitination assay, xenograft tumor model\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — HTS-identified compound validated in cells, ubiquitination assay demonstrating substrate stabilization upon complex disruption, in vivo xenograft validation\",\n      \"pmids\": [\"31598391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CUL4B contributes to colorectal cancer stemness by coordinating with PRC2 to epigenetically repress miR34a expression, leading to upregulation of MYCN and NOTCH1 (miR34a targets). Inhibition of CUL4B in patient-derived tumor organoids reduces sphere formation and metastatic capacity.\",\n      \"method\": \"RNAi in cell lines and patient-derived organoids, ChIP for CUL4B/PRC2 at miR34a locus, sphere formation assays\",\n      \"journal\": \"Oncogenesis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating direct epigenetic repression, patient-derived organoid validation, multiple cancer biology readouts\",\n      \"pmids\": [\"32054830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CUL4B promotes temozolomide resistance in glioblastoma by coordinating with HDAC to co-occupy the CDKN1A (p21) promoter and epigenetically silence CDKN1A transcription, thereby attenuating TMZ-induced cellular senescence.\",\n      \"method\": \"ChIP demonstrating CUL4B and HDAC co-occupancy at CDKN1A promoter, senescence β-galactosidase assay, CUL4B KD/OE in GBM cells\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ChIP demonstrating direct promoter co-occupancy, senescence functional readout, gain- and loss-of-function, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33869025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CUL4B drives thyroid cancer dedifferentiation by promoting ubiquitination of ARID1A (a SWI/SNF complex subunit), leading to its degradation and decreased expression of the differentiation marker PAX8.\",\n      \"method\": \"In vivo TC models, RNA-seq, Co-IP and ubiquitination assay for CUL4B-ARID1A, immunohistochemistry, in vitro functional experiments\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ubiquitination assay establishing ARID1A as substrate, in vivo model, mechanistic pathway from ubiquitination to PAX8 downregulation, multiple methods\",\n      \"pmids\": [\"40203790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"THAP7-AS1 lncRNA interacts with the N-terminal 1-50 amino acid region (NLS) of CUL4B and promotes the interaction between the NLS and importin α1, thereby facilitating CUL4B nuclear import. Nuclear CUL4B then represses miR-22-3p and miR-320a by catalyzing H2AK119ub1 and coordinating EZH2-mediated H3K27me3.\",\n      \"method\": \"Co-IP/RIP for THAP7-AS1-CUL4B interaction, NLS domain mapping, importin α1 interaction assay, ChIP for H2AK119ub1 and H3K27me3\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/domain mapping and ChIP, multiple orthogonal methods, but the nuclear import mechanism adds to the known NLS/importin interaction rather than being entirely novel\",\n      \"pmids\": [\"34608273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CUL4B promotes invasion and metastasis of gastric cancer by epigenetically repressing miR-125a expression, leading to HER2 upregulation and subsequent activation of PI3K/AKT signaling. HER2 inhibitors reverse CUL4B-induced EMT.\",\n      \"method\": \"ChIP for epigenetic marks at miR-125a locus, HER2 inhibitor treatment, gain- and loss-of-function experiments, xenograft metastasis model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP for epigenetic repression, pharmacological rescue with HER2 inhibitors, in vivo xenograft validation, single lab\",\n      \"pmids\": [\"29106389\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CUL4B directly interacts with the promoter of Csf3 (encoding G-CSF) by coordinating with PRC2, epigenetically repressing G-CSF expression. CUL4B deletion in intestinal epithelium epigenetically activates G-CSF, promoting MDSC recruitment and ApcMin/+ adenoma formation.\",\n      \"method\": \"ChIP for CUL4B/PRC2 at Csf3 promoter, ApcMin/+;Cul4bΔIEC mouse model, MDSC depletion rescue, organoid co-culture with MDSCs\",\n      \"journal\": \"Neoplasia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating direct CUL4B binding at Csf3 promoter, conditional KO mouse model, MDSC rescue experiments, multiple orthogonal methods\",\n      \"pmids\": [\"38761506\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CUL4B is an X chromosome-encoded scaffold protein that assembles CUL4B-RING E3 ubiquitin ligase (CRL4B) complexes with DDB1, RBX1/ROC1, and various DCAF substrate receptors; it ubiquitinates diverse substrates for proteasomal degradation (cyclin E, TSC2, p53, HUWE1, PPARγ, INSL6, ARID1A, MEN1 via DCAF7, UTX via DDB1-COP1) and mono-ubiquitinates H2AK119 in concert with PRC2/HDAC complexes to epigenetically silence tumor suppressors and microRNAs; its unique N-terminal NLS (KKRK, aa 37-40) binds importins and is required for nuclear localization, and the N-terminal domain undergoes mitosis-specific phosphorylation that recruits novel DCAFs (LIS1, WDR1) and is essential for spindle positioning and brain development; loss of CUL4B causes embryonic lethality in mice (due to extra-embryonic tissue failure) and X-linked intellectual disability in humans through multiple mechanisms including PP2A-dependent inhibition of AKT/ERK in neural progenitors.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CUL4B is the scaffold subunit of a cullin-RING E3 ubiquitin ligase (CRL4B) that assembles with DDB1, RBX1/ROC1, and interchangeable DCAF substrate receptors to drive both proteasomal degradation of specific substrates and epigenetic gene silencing through chromatin modification [#1, #27]. A nonsense mutation truncating its C-terminal catalytic domain abolishes ligase function and causes X-linked intellectual disability, establishing the C-terminus as essential for catalysis [#1]. As a degradative ligase, CRL4B targets a broad substrate set in a NEDD8-dependent manner — cyclin E and TSC2 (the latter activating mTOR signaling) [#4], p53 [#15, #31], the COP9 signalosome component Jab1/CSN5 [#3], HUWE1 [#6], PPARγ [#8], INSL6 [#9], MEN1 via DCAF7 [#19], the histone demethylase UTX via a DDB1-COP1 module [#27], and ARID1A [#36] — coupling it to cell-cycle progression, metabolism, stress responses, and tumor differentiation. In parallel, CRL4B acts as a chromatin-modifying repressor: it catalyzes monoubiquitination of H2AK119 and coordinates with PRC2 (H3K27me3) and HDAC complexes to silence tumor-suppressor microRNAs and target genes, including miR-194 (a reciprocal feedback partner) [#13], miR-372/373 [#29], miR-34a [#34], and the CDKN1A/p21 promoter [#35], thereby activating oncogenic Wnt/β-catenin, PI3K/AKT, and Notch pathways [#5, #29]. CUL4B carries a unique N-terminal NLS (KKRK, aa 37-40) that binds importin α isoforms and is required for nuclear localization and proliferation [#0], and its N-terminal extension is heavily phosphorylated during mitosis to recruit the noncanonical DCAFs LIS1 and WDR1, controlling spindle positioning and forebrain development [#18]. CUL4B is essential for mouse embryonic development through a requirement in extra-embryonic tissues [#7], and in neural progenitors its loss derepresses PP2A regulatory subunits PPP2R2B/PPP2R2C, inhibiting AKT/ERK to cause premature cell-cycle exit and precocious neuronal differentiation underlying X-linked intellectual disability [#21].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established CUL4B as a cullin-RING E3 ligase scaffold whose C-terminal catalytic domain is essential, linking its loss of function to human disease.\",\n      \"evidence\": \"Mutation analysis of an XLID nonsense allele (p.R388X) with NMD and X-inactivation analysis in patient cells\",\n      \"pmids\": [\"17273978\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define substrate receptors or specific substrates\", \"Mechanism connecting ligase loss to intellectual disability not addressed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved why CUL4B differs from other cullins by mapping a unique N-terminal NLS required for nuclear localization and proliferation, and identified cyclin E as a degradation substrate.\",\n      \"evidence\": \"NLS deletion mutants, importin α1/α3/α5 binding assays, subcellular fractionation, RNAi and cell-cycle analysis\",\n      \"pmids\": [\"19801544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DCAF receptor mediating cyclin E recognition not identified\", \"Did not address how nuclear/cytoplasmic partitioning is regulated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated that CUL4B is required for embryonic viability and localized its essential function to extra-embryonic tissues, distinguishing it from the embryo-intrinsic role.\",\n      \"evidence\": \"Conventional and epiblast-specific (Sox2-Cre) Cul4b knockout mice with cyclin E immunoblotting\",\n      \"pmids\": [\"22453236\", \"22606329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Extra-embryonic substrate(s) driving lethality not defined\", \"Mechanistic basis of tissue specificity unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Expanded the degradative substrate repertoire (Jab1/CSN5, TSC2, cyclin E) and connected CRL4B to mTOR signaling and DNA replication licensing through CDC6/CDK2.\",\n      \"evidence\": \"In vitro/in vivo ubiquitination assays, Co-IP, Cul4b-deficient MEFs, neocortical neuron expression, chromatin fractionation, miRNA manipulation\",\n      \"pmids\": [\"23357576\", \"23348097\", \"23479742\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DCAF receptors for these substrates not specified\", \"Whether degradative and replication-licensing functions are mechanistically separable unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified p53 as a CRL4B substrate, defining a role in suppressing stress-induced senescence via a p53-ROS feedback loop.\",\n      \"evidence\": \"Gain/loss-of-function with p53 ubiquitination assay, H2O2 treatment, ROS and senescence β-gal readouts in fibroblasts\",\n      \"pmids\": [\"25464270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Distinction between stress-induced and replicative senescence regulation not fully mechanistic\", \"DCAF receptor for p53 not identified\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established CRL4B as an epigenetic repressor that recruits PRC2 to silence pathway antagonists, and extended its developmental roles to neural progenitor astrocytogenesis and HUWE1-controlled apoptosis.\",\n      \"evidence\": \"ChIP for PRC2/H3K27me3, rescue/epistasis experiments, nervous-system-specific KO mice, pharmacological PTGDS inhibition, in vitro ubiquitination\",\n      \"pmids\": [\"25430888\", \"26025376\", \"25883150\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of PRC2 recruitment to specific loci unresolved\", \"Relationship between degradative and chromatin-silencing activities at the complex level unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined tissue-specific physiological roles via conditional knockouts (adipocyte PPARγ regulation; germ cell INSL6 degradation in spermatogenesis), with mass-spectrometry substrate identification.\",\n      \"evidence\": \"Adipocyte- and germ-cell-specific conditional KO mice, ubiquitination assays, mass spectrometry, metabolic and sperm phenotyping, EM of flagella\",\n      \"pmids\": [\"27899484\", \"26846852\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DCAF receptors for PPARγ and INSL6 not defined\", \"Non-cell-autonomous niche mechanism in spermatogenesis incompletely resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated that CRL4B directly catalyzes H2AK119 monoubiquitination at microRNA loci, establishing a catalytic chromatin mechanism and a miR-194 double-negative feedback loop downstream of p53.\",\n      \"evidence\": \"ChIP for H2AK119ub/H3K27me3 at miR-194 cluster, 3'-UTR luciferase reporter, RNAi, xenografts\",\n      \"pmids\": [\"28164432\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How H2AK119ub coordinates with PRC2 H3K27me3 mechanistically unresolved\", \"Locus-specificity determinants of CRL4B chromatin targeting unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Revealed immune-regulatory roles in which CRL4B epigenetically tunes myeloid and T-cell programs (PTEN, IL-6, miR-372/373, miR-194-5p) and defined DCAF1 as the T-cell substrate receptor linked to DNA-damage response.\",\n      \"evidence\": \"Myeloid- and T-cell-specific conditional KOs, ChIP at target promoters, pharmacological/blocking rescues, Co-IP and mass spectrometry, DNA damage and SMC1A phosphorylation assays\",\n      \"pmids\": [\"31729464\", \"31235785\", \"32127645\", \"37224018\", \"33524014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CRL4B switches between degradative DCAF1-dependent and chromatin-repressive modes unclear\", \"Direct chromatin substrates versus indirect effects not always distinguished\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Broadened CRL4B oncogenic and viral roles (tamoxifen resistance via miR-32-5p/ER-α36, HBx stabilization to promote HBV, TMZ resistance via CDKN1A silencing) and refined nuclear import via THAP7-AS1 lncRNA enhancing NLS-importin α1 binding.\",\n      \"evidence\": \"ChIP at miR/promoter loci, dominant-negative and KD/OE mutants, Co-IP/RIP/IF, cycloheximide chase, in vivo HBV and tumor models\",\n      \"pmids\": [\"33638154\", \"33969670\", \"33869025\", \"34608273\", \"34146543\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality of lncRNA-assisted nuclear import beyond tested contexts unknown\", \"Whether HBx stabilization reflects substrate competition or altered complex composition unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected mitosis-specific N-terminal phosphorylation to recruitment of noncanonical DCAFs (LIS1, WDR1) controlling spindle positioning, and defined additional DCAF-based substrate complexes (DCAF7-MEN1, DDB1-COP1-UTX) and tumor-microenvironment chromatin targets (Cxcl2, Csf3).\",\n      \"evidence\": \"Phosphoproteomics, Co-IP of LIS1/WDR1/DCAF7/COP1 with DDB1, mutagenesis, live imaging, forebrain organoids, ChIP, conditional KO tumor models\",\n      \"pmids\": [\"37365982\", \"36939378\", \"37679762\", \"37653114\", \"38761506\", \"37925424\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase(s) phosphorylating the N-terminal extension not identified\", \"Structural basis of phosphorylation-dependent DCAF selection unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided a patient-iPSC mechanistic model of XLID showing that CRL4B represses PP2A regulatory subunits (PPP2R2B/C) via H2AK119ub, sustaining AKT/ERK to prevent premature neuronal differentiation, and added p53/PSME3-dependent radiation and kidney-injury roles.\",\n      \"evidence\": \"Patient iPSC-derived neurons/organoids, ChIP for H2AK119ub, PP2A activity assay, AKT/ERK and PP2A pharmacological rescue, kidney conditional KO injury models, Co-IP for CUL4B-PSME3\",\n      \"pmids\": [\"38331954\", \"38689033\", \"39695153\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a single XLID lesion produces both degradative and epigenetic deficits not integrated\", \"PSME3 relocalization to γH2AX foci mechanism incompletely defined (Medium-confidence)\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended CRL4B substrate degradation to chromatin-remodeling factor ARID1A, linking it to thyroid cancer dedifferentiation via PAX8 downregulation.\",\n      \"evidence\": \"Co-IP and ubiquitination assay for CUL4B-ARID1A, in vivo thyroid cancer models, RNA-seq, IHC\",\n      \"pmids\": [\"40203790\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DCAF receptor recognizing ARID1A not identified\", \"Whether ARID1A degradation and chromatin repression act on overlapping gene programs unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the CRL4B complex partitions between its degradative substrate-receptor repertoire and its catalytic chromatin-silencing activity, and what determines locus- and substrate-specific targeting in different tissues.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model integrating DCAF substrate selection with H2AK119ub chromatin function\", \"DCAF receptors for most degradative substrates remain unidentified\", \"Rules governing context-specific microRNA/gene-locus targeting unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 3, 6, 8, 9, 19, 27, 36]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [1, 6, 8, 33]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [13, 14, 29, 34, 35]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [13, 14, 29]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 27, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 37]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [13, 29, 18, 30]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 3, 6, 8, 15, 19, 27, 36]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [13, 14, 29, 34, 35]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 2, 18, 26]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 5, 11, 21, 29]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [11, 12, 22, 23, 25]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 10, 18, 21, 28]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 21, 14, 16]}\n    ],\n    \"complexes\": [\"CRL4B (CUL4B-DDB1-RBX1/ROC1)\", \"CUL4B-DDB1-COP1\", \"CUL4B-PRC2\", \"CUL4B-DCAF1\"],\n    \"partners\": [\"DDB1\", \"RBX1\", \"COP1\", \"DCAF1\", \"DCAF7\", \"LIS1\", \"WDR1\", \"PSME3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}