{"gene":"CHPF","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2025,"finding":"CHPF forms four heterodimeric complexes with CHSY1 or CHSY3 (CHSY1-CHPF, CHSY1-CHPF2, CHSY3-CHPF, CHSY3-CHPF2) that are responsible for chondroitin sulfate chain polymerization in humans. Cryo-EM structure of CHSY3-CHPF complex reveals that CHSY1 and CHSY3 are the enzymatically active subunits with bifunctional glycosyltransferase activity, while CHPF primarily plays a stabilizing role. Chain polymerization follows a non-processive, disruptive mechanism.","method":"Cryo-EM structure determination, in vitro glycosylation assay with chemo-enzymatically synthesized fluorescent substrates, mutational analysis of purified enzyme complexes, in cellulo complementation assay","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure combined with in vitro reconstitution assay, mutagenesis, and in cellulo complementation in a single rigorous study","pmids":["bio_10.1101_2025.03.21.644485"],"is_preprint":true},{"year":2021,"finding":"CHPF modifies syndecan-4 (SDC4) with chondroitin sulfate chains in breast cancer cells, promoting CS formation on SDC4. This modification is associated with increased G-CSF levels, expanded myeloid-derived suppressor cells in the tumor microenvironment, and enhanced tumor growth and metastasis.","method":"shRNA knockdown, co-localization of G-CSF with CS on cell surface, identification of SDC4 as a CHPF substrate, xenograft models","journal":"American journal of cancer research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab with multiple phenotypic readouts, but substrate identification relies on co-localization rather than direct biochemical reconstitution","pmids":["33791155"],"is_preprint":false},{"year":2021,"finding":"CHPF modifies the extracellular matrix proteoglycan decorin (DCN) with chondroitin sulfate chains in hepatocellular carcinoma cells, affecting DCN distribution on the cell surface. CHPF-modified DCN acts as a TGF-β regulator, and CHPF expression suppresses HCC cell growth, migration, and invasion through modulation of TGF-β signaling.","method":"Overexpression and knockdown experiments in vitro and in vivo, mechanistic investigation linking CHPF to DCN and TGF-β signaling, correlation of CHPF and DCN expression in primary tissues","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab with multiple phenotypic readouts and proposed substrate, but biochemical reconstitution of CHPF-DCN modification not demonstrated in abstract","pmids":["33809195"],"is_preprint":false},{"year":2021,"finding":"CHPF promotes gastric cancer development through regulation of E2F1, specifically by affecting UBE2T-mediated E2F1 ubiquitination. E2F1 knockdown decreased CHPF-induced promotion of gastric cancer.","method":"shRNA knockdown, Western blotting, flow cytometry, colony formation, transwell assays, xenograft mouse models, epistasis via E2F1 knockdown rescue experiment","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — genetic epistasis with knockdown rescue and ubiquitination pathway placement, single lab, mechanism inferred rather than directly reconstituted","pmids":["34564711"],"is_preprint":false},{"year":2022,"finding":"CHPF promotes osteosarcoma cell proliferation and migration by inhibiting SKP2 ubiquitination and activating the AKT signaling pathway.","method":"Overexpression and knockdown experiments, Western blotting for AKT pathway components, assessment of SKP2 ubiquitination status, xenograft models","journal":"Genes & diseases","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, mechanism inferred from expression changes and ubiquitination assays without full reconstitution","pmids":["37492722"],"is_preprint":false},{"year":2019,"finding":"CHPF promotes lung adenocarcinoma proliferation and inhibits apoptosis through regulation of the MAPK signaling pathway.","method":"Lentivirus-mediated CHPF knockdown, Western blotting for MAPK pathway components, cell proliferation/apoptosis assays, xenograft models","journal":"Pathology, research and practice","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, pathway placement based on expression changes in MAPK components after knockdown","pmids":["30826152"],"is_preprint":false},{"year":2023,"finding":"CHPF physically interacts with MAD1L1 (Mitotic arrest deficient 1-like 1) in glioma cells, as demonstrated by immunoprecipitation, co-immunoprecipitation, GST pulldown, and LC-MS/MS. Additionally, the transcription factor HNF4A binds to the CHPF promoter region, indicating HNF4A transcriptionally regulates CHPF expression.","method":"Co-immunoprecipitation, GST pulldown, LC-MS/MS, ChIP-PCR, CHPF knockdown with phenotypic readouts in vitro and in vivo","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus GST pulldown and ChIP-PCR from single lab with multiple orthogonal methods","pmids":["37851364"],"is_preprint":false},{"year":2024,"finding":"CHPF promotes colorectal cancer progression through regulation of SMAD9 via ASB2-mediated ubiquitination. CHPF mediates ASB2 activity, which in turn ubiquitinates SMAD9; SMAD9 knockdown abrogated CHPF overexpression-induced CRC promotion.","method":"CHPF knockdown/overexpression, SMAD9 knockdown rescue epistasis, assessment of ASB2-mediated SMAD9 ubiquitination, xenograft models","journal":"Histology and histopathology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, genetic epistasis with downstream ubiquitination pathway but no direct biochemical reconstitution reported in abstract","pmids":["38591191"],"is_preprint":false},{"year":2024,"finding":"CHPF promotes NLRP3 inflammasome activation in colorectal cancer by inducing the MAPK signaling pathway (evidenced by enhanced Phos-ERK1/2, Phos-MEK1, Phos-MEK2, and NLRP3 levels). The transcription factor NFIC acts as upstream regulator of CHPF, binding to promote its expression.","method":"CHPF and NFIC knockdown/overexpression, Western blotting for MAPK pathway phospho-proteins and NLRP3, colony formation, EdU, wound healing, transwell, flow cytometry assays in vitro and xenografts in vivo","journal":"Functional & integrative genomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, pathway placement inferred from phospho-protein expression changes; no direct binding assay for NFIC-CHPF promoter reported in abstract","pmids":["38267731"],"is_preprint":false},{"year":2023,"finding":"miR-150-3p, carried by extracellular vesicles from hypoxic trophoblasts, directly targets and inhibits CHPF expression in endothelial cells. CHPF inhibition by miR-150-3p suppresses endothelial cell proliferation, migration, and angiogenesis.","method":"Luciferase reporter assay (direct target validation of miR-150-3p binding to CHPF), qRT-PCR, Western blotting, functional cell assays","journal":"Placenta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter assay directly validates miR-150-3p targeting of CHPF, complemented by functional rescue experiments","pmids":["37156185"],"is_preprint":false},{"year":2021,"finding":"Knockout of ChSy-2 (CHPF/CSS2/CHSY2) in JEG3 choriocarcinoma cells using CRISPR/Cas9 led to significant reduction of placental-like chondroitin sulfate A (pl-CSA), which inhibited cell proliferation, migration, invasion, colony formation in vitro, and suppressed tumorigenesis and metastasis in xenograft models in vivo.","method":"CRISPR/Cas9 knockout, immunofluorescence, flow cytometry, Western blot, ELISA for pl-CSA, cell proliferation/migration/invasion assays, xenograft models","journal":"International journal of medical sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean CRISPR/Cas9 knockout with direct measurement of CS product (pl-CSA) and multiple functional readouts in vitro and in vivo, single lab","pmids":["33390789"],"is_preprint":false},{"year":2020,"finding":"CHPF knockdown in melanoma cells inhibits proliferation and promotes apoptosis; RNA-sequencing and Ingenuity Pathway Analysis identified CDK1 as a downstream target of CHPF in melanoma. CDK1 knockdown inhibited melanoma development and alleviated CHPF overexpression-induced promotion of malignancy.","method":"CHPF overexpression and knockdown, RNA-sequencing with IPA analysis, CDK1 knockdown rescue epistasis, in vitro proliferation/migration/apoptosis assays, xenograft models","journal":"Cell death & disease","confidence":"Low","confidence_rationale":"Tier 3 / Weak — genetic epistasis via CDK1 knockdown rescue; CDK1 identification based on transcriptomic analysis without direct biochemical mechanism","pmids":["32612115"],"is_preprint":false}],"current_model":"CHPF is a glycosyltransferase that forms heterodimeric complexes with CHSY1 or CHSY3, primarily playing a stabilizing role while the CHSY partner provides bifunctional enzymatic activity for non-processive chondroitin sulfate chain polymerization; in cancer contexts, CHPF-mediated CS modification of substrates such as syndecan-4 and decorin alters their surface distribution and downstream signaling (TGF-β, MAPK, AKT), and CHPF physically interacts with MAD1L1 while being transcriptionally regulated by HNF4A and NFIC."},"narrative":{"mechanistic_narrative":"CHPF is a chondroitin sulfate glycosyltransferase that drives biosynthesis of chondroitin sulfate chains by assembling into heterodimeric polymerizing complexes [PMID:bio_10.1101_2025.03.21.644485, PMID:33390789]. Cryo-EM and in vitro reconstitution of the CHSY3-CHPF complex established that CHPF pairs with the bifunctional active subunits CHSY1 or CHSY3 (forming CHSY1-CHPF, CHSY1-CHPF2, CHSY3-CHPF, and CHSY3-CHPF2), where CHPF chiefly stabilizes the enzymatically active CHSY partner and chain elongation proceeds by a non-processive, disruptive mechanism [PMID:bio_10.1101_2025.03.21.644485]; CRISPR knockout of CHPF (ChSy-2) confirms its requirement for cellular chondroitin sulfate output, reducing placental-type CS-A [PMID:33390789]. In cancer, CHPF-mediated CS modification of cell-surface and matrix proteoglycans reshapes signaling: it adds CS chains to syndecan-4 to promote G-CSF accumulation, myeloid-derived suppressor cell expansion, and breast tumor progression [PMID:33791155], and modifies the matrix proteoglycan decorin to alter its surface distribution and tune TGF-β signaling in hepatocellular carcinoma [PMID:33809195]. Across additional tumor types CHPF is recurrently linked to proliferative and survival signaling through MAPK and AKT pathways and to ubiquitination-dependent control of cell-cycle and signaling effectors [PMID:30826152, PMID:37492722]. CHPF physically interacts with MAD1L1 in glioma and is transcriptionally driven by HNF4A [PMID:37851364], and is post-transcriptionally repressed by extracellular-vesicle–delivered miR-150-3p in endothelial cells [PMID:37156185].","teleology":[{"year":2019,"claim":"Established a functional link between CHPF and a defined oncogenic signaling axis, moving CHPF from a glycosyltransferase to a cancer-relevant regulator.","evidence":"Lentiviral CHPF knockdown with MAPK pathway readouts and xenografts in lung adenocarcinoma","pmids":["30826152"],"confidence":"Low","gaps":["Pathway placement inferred from phospho/expression changes, not direct mechanism","No connection drawn to CHPF glycosyltransferase activity","Single lab"]},{"year":2020,"claim":"Tested whether CHPF drives proliferation through a specific cell-cycle effector, addressing how its expression promotes malignancy.","evidence":"CHPF gain/loss with RNA-seq/IPA and CDK1 knockdown rescue epistasis in melanoma plus xenografts","pmids":["32612115"],"confidence":"Low","gaps":["CDK1 link from transcriptomics, no direct biochemical mechanism","How CHPF enzymatic function connects to CDK1 unresolved"]},{"year":2021,"claim":"Identified specific proteoglycan substrates of CHPF and connected CS modification to extracellular signaling, defining a mechanism beyond bulk CS synthesis.","evidence":"shRNA knockdown with substrate (SDC4) co-localization and tumor microenvironment readouts in breast cancer; overexpression/knockdown linking CHPF-modified decorin to TGF-β in HCC","pmids":["33791155","33809195"],"confidence":"Medium","gaps":["Substrate modification shown by co-localization/correlation, not biochemical reconstitution","Opposite phenotypic directions across tumor types not mechanistically reconciled"]},{"year":2021,"claim":"Demonstrated that CHPF is required for cellular chondroitin sulfate production and that loss of CS output is anti-tumorigenic, tying enzymatic function to phenotype.","evidence":"CRISPR/Cas9 knockout of CHPF (ChSy-2) in JEG3 cells with direct pl-CSA measurement and in vitro/in vivo functional assays","pmids":["33390789"],"confidence":"Medium","gaps":["Does not resolve which CS-modified substrates mediate the phenotype","Single cell-line context"]},{"year":2021,"claim":"Placed CHPF upstream of ubiquitination-controlled cell-cycle regulators, proposing a route from CHPF to proliferation control.","evidence":"shRNA knockdown with E2F1 knockdown rescue epistasis and UBE2T-mediated ubiquitination assessment in gastric cancer","pmids":["34564711"],"confidence":"Medium","gaps":["Mechanism inferred via epistasis, not reconstituted","Link between CHPF glycosyltransferase activity and ubiquitination machinery unexplained"]},{"year":2022,"claim":"Extended CHPF's signaling reach to the AKT pathway via control of an E3 substrate-recognition factor's ubiquitination.","evidence":"Overexpression/knockdown with SKP2 ubiquitination and AKT pathway blotting in osteosarcoma plus xenografts","pmids":["37492722"],"confidence":"Low","gaps":["No reconstitution of SKP2 ubiquitination control by CHPF","Single lab"]},{"year":2023,"claim":"Provided the first direct physical interactor and transcriptional regulator of CHPF, beginning to define its protein-interaction and regulatory context.","evidence":"Reciprocal Co-IP, GST pulldown, LC-MS/MS for MAD1L1 interaction and ChIP-PCR for HNF4A binding in glioma","pmids":["37851364"],"confidence":"Medium","gaps":["Functional consequence of CHPF-MAD1L1 interaction not defined","Interaction not linked to CHPF catalytic role"]},{"year":2023,"claim":"Established CHPF as a direct target of microRNA regulation controlling endothelial angiogenic behavior.","evidence":"Luciferase reporter validation of miR-150-3p binding to CHPF with functional endothelial assays","pmids":["37156185"],"confidence":"Medium","gaps":["Downstream effectors of CHPF in endothelial cells not defined","Single context (hypoxic trophoblast EVs)"]},{"year":2024,"claim":"Added further ubiquitination-dependent and inflammasome-linked downstream axes plus an additional upstream transcription factor in colorectal cancer.","evidence":"Knockdown/overexpression with SMAD9/ASB2 ubiquitination epistasis and MAPK/NLRP3 phospho-protein readouts; NFIC regulation in colorectal cancer","pmids":["38591191","38267731"],"confidence":"Low","gaps":["Pathways placed by expression/phospho changes without reconstitution","NFIC-CHPF promoter binding not directly demonstrated"]},{"year":2025,"claim":"Resolved the molecular architecture and catalytic logic of CHPF, defining it as a stabilizing subunit of CHSY-containing chondroitin sulfate polymerase complexes.","evidence":"Cryo-EM structure of CHSY3-CHPF, in vitro glycosylation with synthetic fluorescent substrates, mutagenesis, and in cellulo complementation (preprint)","pmids":["bio_10.1101_2025.03.21.644485"],"confidence":"High","gaps":["How complex composition selects specific proteoglycan substrates unknown","Structural basis for non-processive disruptive mechanism not fully detailed"]},{"year":null,"claim":"How CHPF's biochemically defined CS-polymerizing activity mechanistically connects to its many reported ubiquitination and signaling outputs across cancers remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstitution linking CS modification of specific substrates to MAPK/AKT/TGF-β phenotypes","Whether non-enzymatic CHPF functions explain protein-interaction effects (e.g., MAD1L1) is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,10]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0]}],"localization":[],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,10]}],"complexes":["CHSY1-CHPF / CHSY3-CHPF chondroitin sulfate polymerase"],"partners":["CHSY1","CHSY3","MAD1L1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IZ52","full_name":"Chondroitin sulfate synthase 2","aliases":["Chondroitin glucuronyltransferase 2","Chondroitin-polymerizing factor","ChPF","Glucuronosyl-N-acetylgalactosaminyl-proteoglycan 4-beta-N-acetylgalactosaminyltransferase II","N-acetylgalactosaminyl-proteoglycan 3-beta-glucuronosyltransferase II","N-acetylgalactosaminyltransferase 2"],"length_aa":775,"mass_kda":85.5,"function":"Has both beta-1,3-glucuronic acid and beta-1,4-N-acetylgalactosamine transferase activity. Transfers glucuronic acid (GlcUA) from UDP-GlcUA and N-acetylgalactosamine (GalNAc) from UDP-GalNAc to the non-reducing end of the elongating chondroitin polymer. Seems to act as a specific activating factor for CHSY1 in chondroitin polymerization (PubMed:12716890) May facilitate PRKN transport into the mitochondria. In collaboration with PRKN, may enhance cell viability and protect cells from oxidative stress","subcellular_location":"Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/Q8IZ52/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CHPF","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CHPF","total_profiled":1310},"omim":[{"mim_id":"610405","title":"CHONDROITIN POLYMERIZING FACTOR; CHPF","url":"https://www.omim.org/entry/610405"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Vesicles","reliability":"Additional"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CHPF"},"hgnc":{"alias_symbol":["CSS2","CHSY2","CHPF1"],"prev_symbol":[]},"alphafold":{"accession":"Q8IZ52","domains":[{"cath_id":"3.90.550.50","chopping":"111-330","consensus_level":"high","plddt":90.7216,"start":111,"end":330},{"cath_id":"3.10.450.10","chopping":"396-491","consensus_level":"high","plddt":93.9874,"start":396,"end":491},{"cath_id":"3.90.550,3.90.550","chopping":"509-762","consensus_level":"medium","plddt":91.4537,"start":509,"end":762}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IZ52","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IZ52-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IZ52-F1-predicted_aligned_error_v6.png","plddt_mean":85.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CHPF","jax_strain_url":"https://www.jax.org/strain/search?query=CHPF"},"sequence":{"accession":"Q8IZ52","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IZ52.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IZ52/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IZ52"}},"corpus_meta":[{"pmid":"34564711","id":"PMC_34564711","title":"CHPF promotes gastric cancer tumorigenesis through the activation of E2F1.","date":"2021","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/34564711","citation_count":38,"is_preprint":false},{"pmid":"30826152","id":"PMC_30826152","title":"CHPF promotes lung adenocarcinoma proliferation and anti-apoptosis via the MAPK pathway.","date":"2019","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/30826152","citation_count":35,"is_preprint":false},{"pmid":"32612115","id":"PMC_32612115","title":"Chondroitin polymerizing factor (CHPF) promotes development of malignant melanoma through regulation of CDK1.","date":"2020","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/32612115","citation_count":22,"is_preprint":false},{"pmid":"33791155","id":"PMC_33791155","title":"CHPF promotes malignancy of breast cancer cells by modifying syndecan-4 and the tumor microenvironment.","date":"2021","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/33791155","citation_count":22,"is_preprint":false},{"pmid":"33809195","id":"PMC_33809195","title":"CHPF Regulates the Aggressive Phenotypes of Hepatocellular Carcinoma Cells via the Modulation of the Decorin and TGF-β Pathways.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/33809195","citation_count":17,"is_preprint":false},{"pmid":"31118773","id":"PMC_31118773","title":"Knockdown of CHPF suppresses cell progression of non-small-cell lung cancer.","date":"2019","source":"Cancer management and research","url":"https://pubmed.ncbi.nlm.nih.gov/31118773","citation_count":13,"is_preprint":false},{"pmid":"37156185","id":"PMC_37156185","title":"Extracellular vesicles derived from hypoxic HTR-8/SVneo trophoblast inhibit endothelial cell functions through the miR-150-3p /CHPF pathway.","date":"2023","source":"Placenta","url":"https://pubmed.ncbi.nlm.nih.gov/37156185","citation_count":13,"is_preprint":false},{"pmid":"32348423","id":"PMC_32348423","title":"Expression of CHPF modulates cell proliferation and invasion in lung cancer.","date":"2020","source":"Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas","url":"https://pubmed.ncbi.nlm.nih.gov/32348423","citation_count":11,"is_preprint":false},{"pmid":"32383983","id":"PMC_32383983","title":"Chondroitin polymerizing factor (CHPF) contributes to malignant proliferation and migration of hepatocellular carcinoma cells.","date":"2020","source":"Biochemistry and cell biology = Biochimie et biologie cellulaire","url":"https://pubmed.ncbi.nlm.nih.gov/32383983","citation_count":9,"is_preprint":false},{"pmid":"31828417","id":"PMC_31828417","title":"Tanshinol inhibits growth of malignant melanoma cells via regulating miR-1207-5p/CHPF pathway.","date":"2019","source":"Archives of dermatological research","url":"https://pubmed.ncbi.nlm.nih.gov/31828417","citation_count":8,"is_preprint":false},{"pmid":"38190270","id":"PMC_38190270","title":"MiR-214-3p overexpression-triggered chondroitin polymerizing factor (CHPF) inhibition modulates the ferroptosis and metabolism in colon cancer.","date":"2024","source":"The Kaohsiung journal of medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38190270","citation_count":8,"is_preprint":false},{"pmid":"33651657","id":"PMC_33651657","title":"Identification of chondroitin polymerizing factor (CHPF) as tumor promotor in cholangiocarcinoma through regulating cell proliferation, cell apoptosis and cell migration.","date":"2021","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/33651657","citation_count":7,"is_preprint":false},{"pmid":"37851364","id":"PMC_37851364","title":"The HNF4A-CHPF pathway promotes proliferation and invasion through interactions with MAD1L1 in glioma.","date":"2023","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/37851364","citation_count":6,"is_preprint":false},{"pmid":"37492722","id":"PMC_37492722","title":"Chondroitin Polymerizing Factor (CHPF) promotes cell proliferation and tumor growth in human osteosarcoma by inhibiting SKP2's ubiquitination while activating the AKT pathway.","date":"2022","source":"Genes & diseases","url":"https://pubmed.ncbi.nlm.nih.gov/37492722","citation_count":6,"is_preprint":false},{"pmid":"38591191","id":"PMC_38591191","title":"Chondroitin polymerizing factor (CHPF) promotes the progression of colorectal cancer through ASB2-mediated ubiquitylation of SMAD9.","date":"2024","source":"Histology and histopathology","url":"https://pubmed.ncbi.nlm.nih.gov/38591191","citation_count":4,"is_preprint":false},{"pmid":"38267731","id":"PMC_38267731","title":"Activation of CHPF by transcription factor NFIC promotes NLRP3 activation during the progression of colorectal cancer.","date":"2024","source":"Functional & integrative genomics","url":"https://pubmed.ncbi.nlm.nih.gov/38267731","citation_count":2,"is_preprint":false},{"pmid":"33390789","id":"PMC_33390789","title":"Reduction of pl-CSA through ChSy-2 knockout inhibits tumorigenesis and metastasis of choriocarcinoma in JEG3 cells.","date":"2021","source":"International journal of medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33390789","citation_count":2,"is_preprint":false},{"pmid":"39292317","id":"PMC_39292317","title":"Analysis of the role of CHPF in colorectal cancer tumorigenesis and immunotherapy based on bioinformatics and experiments.","date":"2024","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/39292317","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.21.644485","title":"Structural basis for human chondroitin sulfate chain polymerization","date":"2025-03-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.21.644485","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11067,"output_tokens":3115,"usd":0.039963,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10504,"output_tokens":3313,"usd":0.067672,"stage2_stop_reason":"end_turn"},"total_usd":0.107635,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2025,\n      \"finding\": \"CHPF forms four heterodimeric complexes with CHSY1 or CHSY3 (CHSY1-CHPF, CHSY1-CHPF2, CHSY3-CHPF, CHSY3-CHPF2) that are responsible for chondroitin sulfate chain polymerization in humans. Cryo-EM structure of CHSY3-CHPF complex reveals that CHSY1 and CHSY3 are the enzymatically active subunits with bifunctional glycosyltransferase activity, while CHPF primarily plays a stabilizing role. Chain polymerization follows a non-processive, disruptive mechanism.\",\n      \"method\": \"Cryo-EM structure determination, in vitro glycosylation assay with chemo-enzymatically synthesized fluorescent substrates, mutational analysis of purified enzyme complexes, in cellulo complementation assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure combined with in vitro reconstitution assay, mutagenesis, and in cellulo complementation in a single rigorous study\",\n      \"pmids\": [\"bio_10.1101_2025.03.21.644485\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CHPF modifies syndecan-4 (SDC4) with chondroitin sulfate chains in breast cancer cells, promoting CS formation on SDC4. This modification is associated with increased G-CSF levels, expanded myeloid-derived suppressor cells in the tumor microenvironment, and enhanced tumor growth and metastasis.\",\n      \"method\": \"shRNA knockdown, co-localization of G-CSF with CS on cell surface, identification of SDC4 as a CHPF substrate, xenograft models\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab with multiple phenotypic readouts, but substrate identification relies on co-localization rather than direct biochemical reconstitution\",\n      \"pmids\": [\"33791155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CHPF modifies the extracellular matrix proteoglycan decorin (DCN) with chondroitin sulfate chains in hepatocellular carcinoma cells, affecting DCN distribution on the cell surface. CHPF-modified DCN acts as a TGF-β regulator, and CHPF expression suppresses HCC cell growth, migration, and invasion through modulation of TGF-β signaling.\",\n      \"method\": \"Overexpression and knockdown experiments in vitro and in vivo, mechanistic investigation linking CHPF to DCN and TGF-β signaling, correlation of CHPF and DCN expression in primary tissues\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab with multiple phenotypic readouts and proposed substrate, but biochemical reconstitution of CHPF-DCN modification not demonstrated in abstract\",\n      \"pmids\": [\"33809195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CHPF promotes gastric cancer development through regulation of E2F1, specifically by affecting UBE2T-mediated E2F1 ubiquitination. E2F1 knockdown decreased CHPF-induced promotion of gastric cancer.\",\n      \"method\": \"shRNA knockdown, Western blotting, flow cytometry, colony formation, transwell assays, xenograft mouse models, epistasis via E2F1 knockdown rescue experiment\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — genetic epistasis with knockdown rescue and ubiquitination pathway placement, single lab, mechanism inferred rather than directly reconstituted\",\n      \"pmids\": [\"34564711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CHPF promotes osteosarcoma cell proliferation and migration by inhibiting SKP2 ubiquitination and activating the AKT signaling pathway.\",\n      \"method\": \"Overexpression and knockdown experiments, Western blotting for AKT pathway components, assessment of SKP2 ubiquitination status, xenograft models\",\n      \"journal\": \"Genes & diseases\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, mechanism inferred from expression changes and ubiquitination assays without full reconstitution\",\n      \"pmids\": [\"37492722\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CHPF promotes lung adenocarcinoma proliferation and inhibits apoptosis through regulation of the MAPK signaling pathway.\",\n      \"method\": \"Lentivirus-mediated CHPF knockdown, Western blotting for MAPK pathway components, cell proliferation/apoptosis assays, xenograft models\",\n      \"journal\": \"Pathology, research and practice\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, pathway placement based on expression changes in MAPK components after knockdown\",\n      \"pmids\": [\"30826152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CHPF physically interacts with MAD1L1 (Mitotic arrest deficient 1-like 1) in glioma cells, as demonstrated by immunoprecipitation, co-immunoprecipitation, GST pulldown, and LC-MS/MS. Additionally, the transcription factor HNF4A binds to the CHPF promoter region, indicating HNF4A transcriptionally regulates CHPF expression.\",\n      \"method\": \"Co-immunoprecipitation, GST pulldown, LC-MS/MS, ChIP-PCR, CHPF knockdown with phenotypic readouts in vitro and in vivo\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus GST pulldown and ChIP-PCR from single lab with multiple orthogonal methods\",\n      \"pmids\": [\"37851364\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CHPF promotes colorectal cancer progression through regulation of SMAD9 via ASB2-mediated ubiquitination. CHPF mediates ASB2 activity, which in turn ubiquitinates SMAD9; SMAD9 knockdown abrogated CHPF overexpression-induced CRC promotion.\",\n      \"method\": \"CHPF knockdown/overexpression, SMAD9 knockdown rescue epistasis, assessment of ASB2-mediated SMAD9 ubiquitination, xenograft models\",\n      \"journal\": \"Histology and histopathology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, genetic epistasis with downstream ubiquitination pathway but no direct biochemical reconstitution reported in abstract\",\n      \"pmids\": [\"38591191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CHPF promotes NLRP3 inflammasome activation in colorectal cancer by inducing the MAPK signaling pathway (evidenced by enhanced Phos-ERK1/2, Phos-MEK1, Phos-MEK2, and NLRP3 levels). The transcription factor NFIC acts as upstream regulator of CHPF, binding to promote its expression.\",\n      \"method\": \"CHPF and NFIC knockdown/overexpression, Western blotting for MAPK pathway phospho-proteins and NLRP3, colony formation, EdU, wound healing, transwell, flow cytometry assays in vitro and xenografts in vivo\",\n      \"journal\": \"Functional & integrative genomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, pathway placement inferred from phospho-protein expression changes; no direct binding assay for NFIC-CHPF promoter reported in abstract\",\n      \"pmids\": [\"38267731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"miR-150-3p, carried by extracellular vesicles from hypoxic trophoblasts, directly targets and inhibits CHPF expression in endothelial cells. CHPF inhibition by miR-150-3p suppresses endothelial cell proliferation, migration, and angiogenesis.\",\n      \"method\": \"Luciferase reporter assay (direct target validation of miR-150-3p binding to CHPF), qRT-PCR, Western blotting, functional cell assays\",\n      \"journal\": \"Placenta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter assay directly validates miR-150-3p targeting of CHPF, complemented by functional rescue experiments\",\n      \"pmids\": [\"37156185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Knockout of ChSy-2 (CHPF/CSS2/CHSY2) in JEG3 choriocarcinoma cells using CRISPR/Cas9 led to significant reduction of placental-like chondroitin sulfate A (pl-CSA), which inhibited cell proliferation, migration, invasion, colony formation in vitro, and suppressed tumorigenesis and metastasis in xenograft models in vivo.\",\n      \"method\": \"CRISPR/Cas9 knockout, immunofluorescence, flow cytometry, Western blot, ELISA for pl-CSA, cell proliferation/migration/invasion assays, xenograft models\",\n      \"journal\": \"International journal of medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean CRISPR/Cas9 knockout with direct measurement of CS product (pl-CSA) and multiple functional readouts in vitro and in vivo, single lab\",\n      \"pmids\": [\"33390789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CHPF knockdown in melanoma cells inhibits proliferation and promotes apoptosis; RNA-sequencing and Ingenuity Pathway Analysis identified CDK1 as a downstream target of CHPF in melanoma. CDK1 knockdown inhibited melanoma development and alleviated CHPF overexpression-induced promotion of malignancy.\",\n      \"method\": \"CHPF overexpression and knockdown, RNA-sequencing with IPA analysis, CDK1 knockdown rescue epistasis, in vitro proliferation/migration/apoptosis assays, xenograft models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — genetic epistasis via CDK1 knockdown rescue; CDK1 identification based on transcriptomic analysis without direct biochemical mechanism\",\n      \"pmids\": [\"32612115\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CHPF is a glycosyltransferase that forms heterodimeric complexes with CHSY1 or CHSY3, primarily playing a stabilizing role while the CHSY partner provides bifunctional enzymatic activity for non-processive chondroitin sulfate chain polymerization; in cancer contexts, CHPF-mediated CS modification of substrates such as syndecan-4 and decorin alters their surface distribution and downstream signaling (TGF-β, MAPK, AKT), and CHPF physically interacts with MAD1L1 while being transcriptionally regulated by HNF4A and NFIC.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CHPF is a chondroitin sulfate glycosyltransferase that drives biosynthesis of chondroitin sulfate chains by assembling into heterodimeric polymerizing complexes [#0, #10]. Cryo-EM and in vitro reconstitution of the CHSY3-CHPF complex established that CHPF pairs with the bifunctional active subunits CHSY1 or CHSY3 (forming CHSY1-CHPF, CHSY1-CHPF2, CHSY3-CHPF, and CHSY3-CHPF2), where CHPF chiefly stabilizes the enzymatically active CHSY partner and chain elongation proceeds by a non-processive, disruptive mechanism [#0]; CRISPR knockout of CHPF (ChSy-2) confirms its requirement for cellular chondroitin sulfate output, reducing placental-type CS-A [#10]. In cancer, CHPF-mediated CS modification of cell-surface and matrix proteoglycans reshapes signaling: it adds CS chains to syndecan-4 to promote G-CSF accumulation, myeloid-derived suppressor cell expansion, and breast tumor progression [#1], and modifies the matrix proteoglycan decorin to alter its surface distribution and tune TGF-\\u03b2 signaling in hepatocellular carcinoma [#2]. Across additional tumor types CHPF is recurrently linked to proliferative and survival signaling through MAPK and AKT pathways and to ubiquitination-dependent control of cell-cycle and signaling effectors [#5, #4]. CHPF physically interacts with MAD1L1 in glioma and is transcriptionally driven by HNF4A [#6], and is post-transcriptionally repressed by extracellular-vesicle\\u2013delivered miR-150-3p in endothelial cells [#9].\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Established a functional link between CHPF and a defined oncogenic signaling axis, moving CHPF from a glycosyltransferase to a cancer-relevant regulator.\",\n      \"evidence\": \"Lentiviral CHPF knockdown with MAPK pathway readouts and xenografts in lung adenocarcinoma\",\n      \"pmids\": [\"30826152\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway placement inferred from phospho/expression changes, not direct mechanism\", \"No connection drawn to CHPF glycosyltransferase activity\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Tested whether CHPF drives proliferation through a specific cell-cycle effector, addressing how its expression promotes malignancy.\",\n      \"evidence\": \"CHPF gain/loss with RNA-seq/IPA and CDK1 knockdown rescue epistasis in melanoma plus xenografts\",\n      \"pmids\": [\"32612115\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"CDK1 link from transcriptomics, no direct biochemical mechanism\", \"How CHPF enzymatic function connects to CDK1 unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified specific proteoglycan substrates of CHPF and connected CS modification to extracellular signaling, defining a mechanism beyond bulk CS synthesis.\",\n      \"evidence\": \"shRNA knockdown with substrate (SDC4) co-localization and tumor microenvironment readouts in breast cancer; overexpression/knockdown linking CHPF-modified decorin to TGF-\\u03b2 in HCC\",\n      \"pmids\": [\"33791155\", \"33809195\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate modification shown by co-localization/correlation, not biochemical reconstitution\", \"Opposite phenotypic directions across tumor types not mechanistically reconciled\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated that CHPF is required for cellular chondroitin sulfate production and that loss of CS output is anti-tumorigenic, tying enzymatic function to phenotype.\",\n      \"evidence\": \"CRISPR/Cas9 knockout of CHPF (ChSy-2) in JEG3 cells with direct pl-CSA measurement and in vitro/in vivo functional assays\",\n      \"pmids\": [\"33390789\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not resolve which CS-modified substrates mediate the phenotype\", \"Single cell-line context\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed CHPF upstream of ubiquitination-controlled cell-cycle regulators, proposing a route from CHPF to proliferation control.\",\n      \"evidence\": \"shRNA knockdown with E2F1 knockdown rescue epistasis and UBE2T-mediated ubiquitination assessment in gastric cancer\",\n      \"pmids\": [\"34564711\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism inferred via epistasis, not reconstituted\", \"Link between CHPF glycosyltransferase activity and ubiquitination machinery unexplained\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended CHPF's signaling reach to the AKT pathway via control of an E3 substrate-recognition factor's ubiquitination.\",\n      \"evidence\": \"Overexpression/knockdown with SKP2 ubiquitination and AKT pathway blotting in osteosarcoma plus xenografts\",\n      \"pmids\": [\"37492722\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No reconstitution of SKP2 ubiquitination control by CHPF\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided the first direct physical interactor and transcriptional regulator of CHPF, beginning to define its protein-interaction and regulatory context.\",\n      \"evidence\": \"Reciprocal Co-IP, GST pulldown, LC-MS/MS for MAD1L1 interaction and ChIP-PCR for HNF4A binding in glioma\",\n      \"pmids\": [\"37851364\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of CHPF-MAD1L1 interaction not defined\", \"Interaction not linked to CHPF catalytic role\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established CHPF as a direct target of microRNA regulation controlling endothelial angiogenic behavior.\",\n      \"evidence\": \"Luciferase reporter validation of miR-150-3p binding to CHPF with functional endothelial assays\",\n      \"pmids\": [\"37156185\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effectors of CHPF in endothelial cells not defined\", \"Single context (hypoxic trophoblast EVs)\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Added further ubiquitination-dependent and inflammasome-linked downstream axes plus an additional upstream transcription factor in colorectal cancer.\",\n      \"evidence\": \"Knockdown/overexpression with SMAD9/ASB2 ubiquitination epistasis and MAPK/NLRP3 phospho-protein readouts; NFIC regulation in colorectal cancer\",\n      \"pmids\": [\"38591191\", \"38267731\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathways placed by expression/phospho changes without reconstitution\", \"NFIC-CHPF promoter binding not directly demonstrated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved the molecular architecture and catalytic logic of CHPF, defining it as a stabilizing subunit of CHSY-containing chondroitin sulfate polymerase complexes.\",\n      \"evidence\": \"Cryo-EM structure of CHSY3-CHPF, in vitro glycosylation with synthetic fluorescent substrates, mutagenesis, and in cellulo complementation (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.03.21.644485\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How complex composition selects specific proteoglycan substrates unknown\", \"Structural basis for non-processive disruptive mechanism not fully detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CHPF's biochemically defined CS-polymerizing activity mechanistically connects to its many reported ubiquitination and signaling outputs across cancers remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reconstitution linking CS modification of specific substrates to MAPK/AKT/TGF-\\u03b2 phenotypes\", \"Whether non-enzymatic CHPF functions explain protein-interaction effects (e.g., MAD1L1) is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 10]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 10]}\n    ],\n    \"complexes\": [\"CHSY1-CHPF / CHSY3-CHPF chondroitin sulfate polymerase\"],\n    \"partners\": [\"CHSY1\", \"CHSY3\", \"MAD1L1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}