{"gene":"DPH3","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2014,"finding":"Yeast Dph3 (KTI11), a CSL-type zinc finger protein that can bind iron, functions as an electron donor in the reduced state to reduce the Fe-S cluster in the Dph1-Dph2 heterodimeric complex, enabling the first step of diphthamide biosynthesis (transfer of the 3-amino-3-carboxypropyl group from SAM to the histidine of EF2).","method":"In vitro reconstitution with purified yeast Dph1, Dph2, and Dph3; EPR spectroscopy to characterize Fe-S cluster redox states; mutagenesis of Dph3 iron-binding residues","journal":"Journal of the American Chemical Society","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with multiple orthogonal methods (EPR, biochemical assay, mutagenesis) in a single rigorous study","pmids":["24422557"],"is_preprint":false},{"year":2021,"finding":"Dph3 donates one iron atom to convert a [3Fe-4S] cluster in Dph1-Dph2 back to a functional [4Fe-4S] cluster, enabling aerobic diphthamide biosynthesis by maintaining radical-SAM enzyme activity in the presence of oxygen.","method":"In vitro biochemical reconstitution, EPR spectroscopy, Mössbauer spectroscopy, X-ray absorption spectroscopy; anaerobic vs. aerobic comparisons with purified proteins","journal":"Journal of the American Chemical Society","confidence":"High","confidence_rationale":"Tier 1 — multiple spectroscopic and biochemical methods in a single rigorous study demonstrating iron transfer mechanism","pmids":["34154323"],"is_preprint":false},{"year":2016,"finding":"Saccharomyces cerevisiae cytochrome b5 reductase Cbr1 is an NADH-dependent reductase for Dph3, reducing Dph3 so it can donate electrons for both diphthamide biosynthesis and tRNA wobble uridine modification, linking cellular metabolic state (NADH) to translational control.","method":"Proteomic identification of Cbr1 as Dph3 interactor; in vitro NADH-dependent reduction assay; genetic validation in yeast","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1–2 — proteomic identification plus in vitro biochemical assay with functional genetic validation","pmids":["27694803"],"is_preprint":false},{"year":2014,"finding":"Kti11/Dph3 forms a heterodimer with Kti13 (crystal structures solved at 2.9 Å); metal coordination by Kti11 and heterodimerization with Kti13 are essential for both diphthamide modification of eEF2 and Elongator-dependent tRNA wobble base modifications. Kti13 restricts access to the Kti11 iron atom, modulating electron transfer capacity, and is identified as an additional component of the diphthamide modification pathway.","method":"X-ray crystallography (2.4 Å Kti13 alone; 2.9 Å Kti11/Kti13 complex); mutational analysis of interface residues validated in vitro and in vivo; functional assays for tRNA modification and diphthamide biosynthesis","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus mutagenesis validated in vitro and in vivo, two orthogonal functional readouts","pmids":["25543256"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of the Kti11/Kti13 complex at 1.45 Å resolution shows Kti13 adopts a seven-bladed β-propeller (RCC1-like fold) and orients Kti11, restricting access to its electron-carrying iron atom and constraining electron transfer capacity. Mutagenesis confirmed key interface residues.","method":"X-ray crystallography (1.45 Å resolution, PDB 4X33); mutagenesis of complex interface residues; in vitro complex formation assays","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with mutagenesis validation; corroborates independent structural study (PMID 25543256)","pmids":["25604895"],"is_preprint":false},{"year":2008,"finding":"Kti11/Dph3 physically interacts with Dph1 and Dph2 (diphthamide synthesis factors), presumably as part of a trimeric complex; it also co-immunoprecipitates with Elp2 and Elp5, two subunits of the Elongator complex. A separation-of-function mutation (kti11-1, C-terminal truncation) dissociates Elongator interaction from Dph1/Dph2 association, demonstrating Kti11 operates in two distinct complexes.","method":"Co-immunoprecipitation; separation-of-function mutagenesis; genetic phenotype analysis (zymocin resistance, diphtheria toxin resistance)","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2–3 — reciprocal co-IP with separation-of-function mutant providing mechanistic dissection, single lab","pmids":["18627462"],"is_preprint":false},{"year":2008,"finding":"Kti13 co-purifies with Kti11/Dph3 and the Kti11 interaction requires the C-terminus of Kti13; double deletion of kti13 and kti11 causes synthetic sickness/lethality, indicating shared Elongator-independent essential function(s).","method":"Co-purification; yeast genetic interaction (double-deletion synthetic lethality); tRNA modification assays","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2–3 — co-purification plus genetic epistasis, single lab","pmids":["18466297"],"is_preprint":false},{"year":2006,"finding":"Dph3 is essential for mouse embryonic development; dph3-/- mice lack diphthamide modification on eEF2 and die by embryonic day 11.5, with defects in allantois-chorion fusion, neural tube degeneration, and placental labyrinth development.","method":"Knockout mouse generation; embryonic phenotype analysis; biochemical verification of loss of diphthamide modification on eEF2 in dph3-/- embryos","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined developmental phenotype and direct biochemical verification of diphthamide loss on eEF2","pmids":["16648478"],"is_preprint":false},{"year":2010,"finding":"In C. elegans, loss-of-function of dph-3 (ortholog of KTI11) causes defects in tRNA modifications (equivalent to yeast kti11 mutants) and suppresses an opal stop codon in lin-1(e1275) by promoting readthrough, placing DPH-3 in an evolutionarily conserved tRNA modification pathway with the ELP complex required for accurate translation.","method":"C. elegans genetic suppressor screen; positional cloning; tRNA modification assays; lin-1::gfp readthrough reporter assay; epistasis analysis with elpc-1-4 and urm-1 mutants","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with functional tRNA modification readout, C. elegans ortholog study","pmids":["20479142"],"is_preprint":false},{"year":2017,"finding":"In S. pombe, dph3Δ is epistatic to dph1Δ for sensitivity to hydroxyurea and MMS, and epistatic to elp3Δ for MMS sensitivity and cold-sensitive growth. Elevated tRNALysUUU levels suppress elp3Δ phenotypes and some dph3Δ phenotypes, indicating Dph3-dependent tRNA modification is required for accurate translation of stress-response proteins.","method":"S. pombe deletion mutant phenotype analysis; epistasis analysis (double mutants); tRNALysUUU overexpression suppression assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — epistasis analysis with multiple genetic combinations and functional suppression by tRNA overexpression","pmids":["28775286"],"is_preprint":false},{"year":2012,"finding":"Dph3 promotes migration and invasion of B16F10 murine melanoma cells through the AKT signaling pathway; Dph3 disruption or siRNA knockdown impairs migration, while overexpression promotes it, and knockdown inhibits in vivo metastasis.","method":"Insertional mutagenesis screen; siRNA knockdown; overexpression; in vitro migration/invasion assays; in vivo metastasis assay; AKT pathway analysis","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 — single lab, AKT pathway link based on correlative signaling assay without direct mechanistic dissection","pmids":["23185508"],"is_preprint":false},{"year":2002,"finding":"KTI11 (DPH3 ortholog) deletion in S. cerevisiae phenocopies Elongator-minus cells; combining kti11 or kti13 deletions with the Elongator HAT subunit ELP3/TOT3 deletion yields synthetic slow-growth effects, genetically linking KTI11 to Elongator function.","method":"Yeast gene disruption; RT-PCR; HA epitope tagging; synthetic genetic interaction (double deletion phenotype analysis)","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with multiple allele combinations, foundational study","pmids":["11994165"],"is_preprint":false}],"current_model":"DPH3/Kti11 is a small CSL-type zinc finger protein that binds iron and, in its reduced state, functions as an electron donor for the [4Fe-4S] cluster of the radical-SAM heterodimer Dph1-Dph2 (catalyzing the first step of diphthamide biosynthesis on eEF2) and also supports Elongator-dependent tRNA wobble uridine modification; it is reduced by the NADH-dependent cytochrome b5 reductase Cbr1, and it can donate an iron atom to repair an oxygen-damaged [3Fe-4S] cluster in Dph1-Dph2 back to a functional [4Fe-4S] cluster. DPH3 forms a heterodimer with Kti13 (whose RCC1-like β-propeller structure constrains Dph3 electron transfer), is essential for mouse embryonic development, and operates in two genetically separable complexes—one with Dph1/Dph2 for diphthamide biosynthesis and one with Elongator subunits for tRNA modification."},"narrative":{"teleology":[{"year":2002,"claim":"Establishing the genetic link between KTI11/DPH3 and Elongator: deletion of KTI11 phenocopied Elongator-minus cells and showed synthetic growth defects with ELP3 deletion, placing DPH3 in the Elongator-dependent pathway before its biochemical role was known.","evidence":"Yeast gene disruption and synthetic genetic interaction analysis in S. cerevisiae","pmids":["11994165"],"confidence":"Medium","gaps":["No biochemical mechanism identified","Physical interaction with Elongator not demonstrated","Role in tRNA modification vs. diphthamide biosynthesis not distinguished"]},{"year":2006,"claim":"Demonstrating physiological essentiality: Dph3 knockout mice die by E11.5 with verified loss of diphthamide on eEF2, establishing that DPH3 is essential for mammalian development and confirming its in vivo requirement for diphthamide biosynthesis.","evidence":"Knockout mouse generation with embryonic phenotype analysis and biochemical verification of diphthamide loss","pmids":["16648478"],"confidence":"High","gaps":["Whether lethality is due to diphthamide loss, tRNA modification defects, or both is unresolved","Tissue-specific requirements not defined"]},{"year":2008,"claim":"Resolving that DPH3 operates in two separable complexes: co-immunoprecipitation showed DPH3 interacts with both Dph1/Dph2 and Elongator subunits Elp2/Elp5, and a separation-of-function C-terminal truncation mutation dissociated these interactions, demonstrating dual complex membership.","evidence":"Co-immunoprecipitation with separation-of-function mutagenesis in S. cerevisiae; co-purification of Kti13 with Kti11","pmids":["18627462","18466297"],"confidence":"Medium","gaps":["Stoichiometry and architecture of the Dph1-Dph2-Dph3 complex not defined","Whether Kti13 participates in both complexes unclear"]},{"year":2014,"claim":"Defining the biochemical mechanism: in vitro reconstitution with purified components and EPR spectroscopy demonstrated that reduced DPH3 donates electrons to the [4Fe-4S] cluster of Dph1-Dph2, enabling the radical-SAM-dependent first step of diphthamide biosynthesis, establishing DPH3 as a physiological electron donor rather than a structural cofactor.","evidence":"In vitro reconstitution with purified yeast Dph1, Dph2, Dph3; EPR spectroscopy; mutagenesis of iron-binding residues","pmids":["24422557"],"confidence":"High","gaps":["In vivo electron transfer rate not measured","How DPH3 is itself re-reduced in vivo not yet identified"]},{"year":2014,"claim":"Structural basis of DPH3 regulation by Kti13: crystal structures of the Kti11–Kti13 heterodimer revealed that the RCC1-like β-propeller of Kti13 restricts access to the DPH3 iron center, modulating electron transfer, and confirmed that both metal coordination and heterodimerization are required for diphthamide and tRNA modification functions.","evidence":"X-ray crystallography (2.9 Å and 1.45 Å resolution) with interface mutagenesis validated in vitro and in vivo","pmids":["25543256","25604895"],"confidence":"High","gaps":["How Kti13-mediated restriction of iron access is dynamically regulated is unknown","No structure of the full Dph1-Dph2-Dph3 ternary complex"]},{"year":2016,"claim":"Identifying the upstream reductase: Cbr1 was identified as the NADH-dependent cytochrome b5 reductase that reduces DPH3, linking cellular NADH/NAD+ ratio to both diphthamide biosynthesis and tRNA modification, completing the electron transfer chain from metabolism to translational control.","evidence":"Proteomic identification of Cbr1 as DPH3 interactor; in vitro NADH-dependent reduction assay; genetic validation in yeast","pmids":["27694803"],"confidence":"High","gaps":["Whether Cbr1 is the sole reductase for DPH3 in vivo is not established","Regulation of Cbr1-DPH3 interaction not characterized"]},{"year":2021,"claim":"Revealing a dual function as iron donor: beyond electron transfer, DPH3 donates an iron atom to repair oxygen-damaged [3Fe-4S] clusters in Dph1-Dph2 back to functional [4Fe-4S], explaining how diphthamide biosynthesis operates under aerobic conditions.","evidence":"In vitro reconstitution with EPR, Mössbauer, and X-ray absorption spectroscopy under aerobic vs. anaerobic conditions","pmids":["34154323"],"confidence":"High","gaps":["Whether iron donation occurs in vivo under physiological O2 tensions not confirmed","Source of iron reloading onto DPH3 after donation is unknown"]},{"year":null,"claim":"Key unresolved questions include: the structural basis of DPH3 engagement with the Dph1-Dph2 complex versus Elongator, how DPH3 is reloaded with iron after donation, and whether the developmental lethality in mice reflects loss of diphthamide, tRNA modification, or both pathways.","evidence":"","pmids":[],"confidence":"High","gaps":["No ternary Dph1-Dph2-Dph3 structure available","Relative contribution of diphthamide vs. tRNA modification to embryonic lethality not dissected","Iron reloading mechanism onto DPH3 unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,1,2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,5]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,7]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[2,8,9,11]}],"complexes":["Dph1-Dph2-Dph3 diphthamide biosynthesis complex","Kti11-Kti13 heterodimer"],"partners":["DPH1","DPH2","KTI13","CBR1","ELP2","ELP5"],"other_free_text":[]},"mechanistic_narrative":"DPH3 (Kti11) is a small CSL-type zinc finger protein that serves as an electron and iron donor essential for both diphthamide biosynthesis on eEF2 and Elongator-dependent tRNA wobble uridine modification. In its reduced state, DPH3 donates electrons to the [4Fe-4S] cluster of the radical-SAM Dph1–Dph2 heterodimer, enabling the first biosynthetic step of diphthamide, and can additionally donate an iron atom to repair oxygen-damaged [3Fe-4S] clusters back to functional [4Fe-4S] form [PMID:24422557, PMID:34154323]. DPH3 is reduced by the NADH-dependent cytochrome b5 reductase Cbr1, coupling cellular metabolic state to translational fidelity, and forms a structurally characterized heterodimer with the RCC1-like β-propeller protein Kti13, which constrains access to the DPH3 iron center and modulates electron transfer [PMID:27694803, PMID:25543256, PMID:25604895]. A separation-of-function mutation demonstrates that DPH3 operates in two genetically distinct complexes—one with Dph1/Dph2 for diphthamide synthesis and one with Elongator subunits for tRNA modification—and Dph3 knockout in mice causes embryonic lethality by E11.5 with loss of eEF2 diphthamide modification [PMID:18627462, PMID:16648478]."},"prefetch_data":{"uniprot":{"accession":"Q96FX2","full_name":"Diphthamide biosynthesis protein 3","aliases":["CSL-type zinc finger-containing protein 2","DelGEF-interacting protein 1","DelGIP1"],"length_aa":82,"mass_kda":9.2,"function":"Required for the first step of diphthamide biosynthesis, a post-translational modification of histidine which occurs in elongation factor 2. DPH1 and DPH2 transfer a 3-amino-3-carboxypropyl (ACP) group from S-adenosyl-L-methionine (SAM) to a histidine residue, the reaction is assisted by a reduction system comprising DPH3 and a NADH-dependent reductase. Acts as an electron donor to reduce the Fe-S cluster in DPH1-DPH2 keeping the [4Fe-4S] clusters in the active and reduced state. Restores iron to DPH1-DPH2 iron-sulfur clusters which have degraded from [4Fe-4S] to [3Fe-4S] by donating an iron atom to reform [4Fe-4S] clusters, in a manner dependent on the presence of elongation factor 2 and SAM. Associates with the elongator complex and is required for tRNA Wobble base modifications mediated by the elongator complex. The elongator complex is required for multiple tRNA modifications, including mcm5U (5-methoxycarbonylmethyl uridine), mcm5s 2U (5-methoxycarbonylmethyl-2-thiouridine), and ncm5U (5-carbamoylmethyl uridine)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q96FX2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/DPH3","classification":"Common Essential","n_dependent_lines":1131,"n_total_lines":1208,"dependency_fraction":0.9362582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DPH3","total_profiled":1310},"omim":[{"mim_id":"608959","title":"DIPHTHAMIDE BIOSYNTHESIS PROTEIN 3; DPH3","url":"https://www.omim.org/entry/608959"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/DPH3"},"hgnc":{"alias_symbol":["DESR1","DELGIP1","MGC20197","KTI11","DELGIP","DPH3A"],"prev_symbol":["ZCSL2"]},"alphafold":{"accession":"Q96FX2","domains":[{"cath_id":"3.10.660.10","chopping":"5-61","consensus_level":"high","plddt":94.1412,"start":5,"end":61}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96FX2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96FX2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96FX2-F1-predicted_aligned_error_v6.png","plddt_mean":83.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DPH3","jax_strain_url":"https://www.jax.org/strain/search?query=DPH3"},"sequence":{"accession":"Q96FX2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96FX2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96FX2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96FX2"}},"corpus_meta":[{"pmid":"11994165","id":"PMC_11994165","title":"KTI11 and KTI13, Saccharomyces cerevisiae genes controlling sensitivity to G1 arrest induced by Kluyveromyces lactis zymocin.","date":"2002","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/11994165","citation_count":61,"is_preprint":false},{"pmid":"24422557","id":"PMC_24422557","title":"Dph3 is an electron donor for Dph1-Dph2 in the first step of eukaryotic diphthamide biosynthesis.","date":"2014","source":"Journal of the American Chemical Society","url":"https://pubmed.ncbi.nlm.nih.gov/24422557","citation_count":58,"is_preprint":false},{"pmid":"16648478","id":"PMC_16648478","title":"Dph3, a small protein required for diphthamide biosynthesis, is essential in mouse development.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16648478","citation_count":56,"is_preprint":false},{"pmid":"26416425","id":"PMC_26416425","title":"Frequent DPH3 promoter mutations in skin cancers.","date":"2015","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/26416425","citation_count":52,"is_preprint":false},{"pmid":"18627462","id":"PMC_18627462","title":"A versatile partner of eukaryotic protein complexes that is involved in multiple biological processes: Kti11/Dph3.","date":"2008","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/18627462","citation_count":48,"is_preprint":false},{"pmid":"25543256","id":"PMC_25543256","title":"Structure of the Kti11/Kti13 heterodimer and its double role in modifications of tRNA and eukaryotic elongation factor 2.","date":"2014","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/25543256","citation_count":37,"is_preprint":false},{"pmid":"18466297","id":"PMC_18466297","title":"Yeast alpha-tubulin suppressor Ats1/Kti13 relates to the Elongator complex and interacts with Elongator partner protein Kti11.","date":"2008","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/18466297","citation_count":30,"is_preprint":false},{"pmid":"25604895","id":"PMC_25604895","title":"Structure of the Elongator cofactor complex Kti11/Kti13 provides insight into the role of Kti13 in Elongator-dependent tRNA modification.","date":"2015","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/25604895","citation_count":21,"is_preprint":false},{"pmid":"23185508","id":"PMC_23185508","title":"Silencing of diphthamide synthesis 3 (Dph3) reduces metastasis of murine melanoma.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23185508","citation_count":20,"is_preprint":false},{"pmid":"27694803","id":"PMC_27694803","title":"Cbr1 is a Dph3 reductase required for the tRNA wobble uridine modification.","date":"2016","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/27694803","citation_count":17,"is_preprint":false},{"pmid":"34154323","id":"PMC_34154323","title":"Dph3 Enables Aerobic Diphthamide Biosynthesis by Donating One Iron Atom to Transform a [3Fe-4S] to a [4Fe-4S] Cluster in Dph1-Dph2.","date":"2021","source":"Journal of the American Chemical Society","url":"https://pubmed.ncbi.nlm.nih.gov/34154323","citation_count":11,"is_preprint":false},{"pmid":"28775286","id":"PMC_28775286","title":"Elp3 and Dph3 of Schizosaccharomyces pombe mediate cellular stress responses through tRNALysUUU modifications.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28775286","citation_count":8,"is_preprint":false},{"pmid":"28555368","id":"PMC_28555368","title":"A mutated dph3 gene causes sensitivity of Schizosaccharomyces pombe cells to cytotoxic agents.","date":"2017","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28555368","citation_count":7,"is_preprint":false},{"pmid":"20479142","id":"PMC_20479142","title":"Allele-specific suppressors of lin-1(R175Opal) identify functions of MOC-3 and DPH-3 in tRNA modification complexes in Caenorhabditis elegans.","date":"2010","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20479142","citation_count":7,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.06.01.24308209","title":"Comprehensive Druggable Genome-Wide Mendelian Randomization Reveals Therapeutic Targets for Kidney Diseases","date":"2024-06-05","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.01.24308209","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8918,"output_tokens":3120,"usd":0.036777},"stage2":{"model":"claude-opus-4-6","input_tokens":6513,"output_tokens":2305,"usd":0.135285},"total_usd":0.172062,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"Yeast Dph3 (KTI11), a CSL-type zinc finger protein that can bind iron, functions as an electron donor in the reduced state to reduce the Fe-S cluster in the Dph1-Dph2 heterodimeric complex, enabling the first step of diphthamide biosynthesis (transfer of the 3-amino-3-carboxypropyl group from SAM to the histidine of EF2).\",\n      \"method\": \"In vitro reconstitution with purified yeast Dph1, Dph2, and Dph3; EPR spectroscopy to characterize Fe-S cluster redox states; mutagenesis of Dph3 iron-binding residues\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with multiple orthogonal methods (EPR, biochemical assay, mutagenesis) in a single rigorous study\",\n      \"pmids\": [\"24422557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Dph3 donates one iron atom to convert a [3Fe-4S] cluster in Dph1-Dph2 back to a functional [4Fe-4S] cluster, enabling aerobic diphthamide biosynthesis by maintaining radical-SAM enzyme activity in the presence of oxygen.\",\n      \"method\": \"In vitro biochemical reconstitution, EPR spectroscopy, Mössbauer spectroscopy, X-ray absorption spectroscopy; anaerobic vs. aerobic comparisons with purified proteins\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple spectroscopic and biochemical methods in a single rigorous study demonstrating iron transfer mechanism\",\n      \"pmids\": [\"34154323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Saccharomyces cerevisiae cytochrome b5 reductase Cbr1 is an NADH-dependent reductase for Dph3, reducing Dph3 so it can donate electrons for both diphthamide biosynthesis and tRNA wobble uridine modification, linking cellular metabolic state (NADH) to translational control.\",\n      \"method\": \"Proteomic identification of Cbr1 as Dph3 interactor; in vitro NADH-dependent reduction assay; genetic validation in yeast\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — proteomic identification plus in vitro biochemical assay with functional genetic validation\",\n      \"pmids\": [\"27694803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Kti11/Dph3 forms a heterodimer with Kti13 (crystal structures solved at 2.9 Å); metal coordination by Kti11 and heterodimerization with Kti13 are essential for both diphthamide modification of eEF2 and Elongator-dependent tRNA wobble base modifications. Kti13 restricts access to the Kti11 iron atom, modulating electron transfer capacity, and is identified as an additional component of the diphthamide modification pathway.\",\n      \"method\": \"X-ray crystallography (2.4 Å Kti13 alone; 2.9 Å Kti11/Kti13 complex); mutational analysis of interface residues validated in vitro and in vivo; functional assays for tRNA modification and diphthamide biosynthesis\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus mutagenesis validated in vitro and in vivo, two orthogonal functional readouts\",\n      \"pmids\": [\"25543256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of the Kti11/Kti13 complex at 1.45 Å resolution shows Kti13 adopts a seven-bladed β-propeller (RCC1-like fold) and orients Kti11, restricting access to its electron-carrying iron atom and constraining electron transfer capacity. Mutagenesis confirmed key interface residues.\",\n      \"method\": \"X-ray crystallography (1.45 Å resolution, PDB 4X33); mutagenesis of complex interface residues; in vitro complex formation assays\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with mutagenesis validation; corroborates independent structural study (PMID 25543256)\",\n      \"pmids\": [\"25604895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kti11/Dph3 physically interacts with Dph1 and Dph2 (diphthamide synthesis factors), presumably as part of a trimeric complex; it also co-immunoprecipitates with Elp2 and Elp5, two subunits of the Elongator complex. A separation-of-function mutation (kti11-1, C-terminal truncation) dissociates Elongator interaction from Dph1/Dph2 association, demonstrating Kti11 operates in two distinct complexes.\",\n      \"method\": \"Co-immunoprecipitation; separation-of-function mutagenesis; genetic phenotype analysis (zymocin resistance, diphtheria toxin resistance)\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — reciprocal co-IP with separation-of-function mutant providing mechanistic dissection, single lab\",\n      \"pmids\": [\"18627462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Kti13 co-purifies with Kti11/Dph3 and the Kti11 interaction requires the C-terminus of Kti13; double deletion of kti13 and kti11 causes synthetic sickness/lethality, indicating shared Elongator-independent essential function(s).\",\n      \"method\": \"Co-purification; yeast genetic interaction (double-deletion synthetic lethality); tRNA modification assays\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-purification plus genetic epistasis, single lab\",\n      \"pmids\": [\"18466297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Dph3 is essential for mouse embryonic development; dph3-/- mice lack diphthamide modification on eEF2 and die by embryonic day 11.5, with defects in allantois-chorion fusion, neural tube degeneration, and placental labyrinth development.\",\n      \"method\": \"Knockout mouse generation; embryonic phenotype analysis; biochemical verification of loss of diphthamide modification on eEF2 in dph3-/- embryos\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined developmental phenotype and direct biochemical verification of diphthamide loss on eEF2\",\n      \"pmids\": [\"16648478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In C. elegans, loss-of-function of dph-3 (ortholog of KTI11) causes defects in tRNA modifications (equivalent to yeast kti11 mutants) and suppresses an opal stop codon in lin-1(e1275) by promoting readthrough, placing DPH-3 in an evolutionarily conserved tRNA modification pathway with the ELP complex required for accurate translation.\",\n      \"method\": \"C. elegans genetic suppressor screen; positional cloning; tRNA modification assays; lin-1::gfp readthrough reporter assay; epistasis analysis with elpc-1-4 and urm-1 mutants\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with functional tRNA modification readout, C. elegans ortholog study\",\n      \"pmids\": [\"20479142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In S. pombe, dph3Δ is epistatic to dph1Δ for sensitivity to hydroxyurea and MMS, and epistatic to elp3Δ for MMS sensitivity and cold-sensitive growth. Elevated tRNALysUUU levels suppress elp3Δ phenotypes and some dph3Δ phenotypes, indicating Dph3-dependent tRNA modification is required for accurate translation of stress-response proteins.\",\n      \"method\": \"S. pombe deletion mutant phenotype analysis; epistasis analysis (double mutants); tRNALysUUU overexpression suppression assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epistasis analysis with multiple genetic combinations and functional suppression by tRNA overexpression\",\n      \"pmids\": [\"28775286\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Dph3 promotes migration and invasion of B16F10 murine melanoma cells through the AKT signaling pathway; Dph3 disruption or siRNA knockdown impairs migration, while overexpression promotes it, and knockdown inhibits in vivo metastasis.\",\n      \"method\": \"Insertional mutagenesis screen; siRNA knockdown; overexpression; in vitro migration/invasion assays; in vivo metastasis assay; AKT pathway analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, AKT pathway link based on correlative signaling assay without direct mechanistic dissection\",\n      \"pmids\": [\"23185508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"KTI11 (DPH3 ortholog) deletion in S. cerevisiae phenocopies Elongator-minus cells; combining kti11 or kti13 deletions with the Elongator HAT subunit ELP3/TOT3 deletion yields synthetic slow-growth effects, genetically linking KTI11 to Elongator function.\",\n      \"method\": \"Yeast gene disruption; RT-PCR; HA epitope tagging; synthetic genetic interaction (double deletion phenotype analysis)\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple allele combinations, foundational study\",\n      \"pmids\": [\"11994165\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DPH3/Kti11 is a small CSL-type zinc finger protein that binds iron and, in its reduced state, functions as an electron donor for the [4Fe-4S] cluster of the radical-SAM heterodimer Dph1-Dph2 (catalyzing the first step of diphthamide biosynthesis on eEF2) and also supports Elongator-dependent tRNA wobble uridine modification; it is reduced by the NADH-dependent cytochrome b5 reductase Cbr1, and it can donate an iron atom to repair an oxygen-damaged [3Fe-4S] cluster in Dph1-Dph2 back to a functional [4Fe-4S] cluster. DPH3 forms a heterodimer with Kti13 (whose RCC1-like β-propeller structure constrains Dph3 electron transfer), is essential for mouse embryonic development, and operates in two genetically separable complexes—one with Dph1/Dph2 for diphthamide biosynthesis and one with Elongator subunits for tRNA modification.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"DPH3 (Kti11) is a small CSL-type zinc finger protein that serves as an electron and iron donor essential for both diphthamide biosynthesis on eEF2 and Elongator-dependent tRNA wobble uridine modification. In its reduced state, DPH3 donates electrons to the [4Fe-4S] cluster of the radical-SAM Dph1–Dph2 heterodimer, enabling the first biosynthetic step of diphthamide, and can additionally donate an iron atom to repair oxygen-damaged [3Fe-4S] clusters back to functional [4Fe-4S] form [PMID:24422557, PMID:34154323]. DPH3 is reduced by the NADH-dependent cytochrome b5 reductase Cbr1, coupling cellular metabolic state to translational fidelity, and forms a structurally characterized heterodimer with the RCC1-like β-propeller protein Kti13, which constrains access to the DPH3 iron center and modulates electron transfer [PMID:27694803, PMID:25543256, PMID:25604895]. A separation-of-function mutation demonstrates that DPH3 operates in two genetically distinct complexes—one with Dph1/Dph2 for diphthamide synthesis and one with Elongator subunits for tRNA modification—and Dph3 knockout in mice causes embryonic lethality by E11.5 with loss of eEF2 diphthamide modification [PMID:18627462, PMID:16648478].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing the genetic link between KTI11/DPH3 and Elongator: deletion of KTI11 phenocopied Elongator-minus cells and showed synthetic growth defects with ELP3 deletion, placing DPH3 in the Elongator-dependent pathway before its biochemical role was known.\",\n      \"evidence\": \"Yeast gene disruption and synthetic genetic interaction analysis in S. cerevisiae\",\n      \"pmids\": [\"11994165\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No biochemical mechanism identified\", \"Physical interaction with Elongator not demonstrated\", \"Role in tRNA modification vs. diphthamide biosynthesis not distinguished\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating physiological essentiality: Dph3 knockout mice die by E11.5 with verified loss of diphthamide on eEF2, establishing that DPH3 is essential for mammalian development and confirming its in vivo requirement for diphthamide biosynthesis.\",\n      \"evidence\": \"Knockout mouse generation with embryonic phenotype analysis and biochemical verification of diphthamide loss\",\n      \"pmids\": [\"16648478\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether lethality is due to diphthamide loss, tRNA modification defects, or both is unresolved\", \"Tissue-specific requirements not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Resolving that DPH3 operates in two separable complexes: co-immunoprecipitation showed DPH3 interacts with both Dph1/Dph2 and Elongator subunits Elp2/Elp5, and a separation-of-function C-terminal truncation mutation dissociated these interactions, demonstrating dual complex membership.\",\n      \"evidence\": \"Co-immunoprecipitation with separation-of-function mutagenesis in S. cerevisiae; co-purification of Kti13 with Kti11\",\n      \"pmids\": [\"18627462\", \"18466297\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and architecture of the Dph1-Dph2-Dph3 complex not defined\", \"Whether Kti13 participates in both complexes unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defining the biochemical mechanism: in vitro reconstitution with purified components and EPR spectroscopy demonstrated that reduced DPH3 donates electrons to the [4Fe-4S] cluster of Dph1-Dph2, enabling the radical-SAM-dependent first step of diphthamide biosynthesis, establishing DPH3 as a physiological electron donor rather than a structural cofactor.\",\n      \"evidence\": \"In vitro reconstitution with purified yeast Dph1, Dph2, Dph3; EPR spectroscopy; mutagenesis of iron-binding residues\",\n      \"pmids\": [\"24422557\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo electron transfer rate not measured\", \"How DPH3 is itself re-reduced in vivo not yet identified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Structural basis of DPH3 regulation by Kti13: crystal structures of the Kti11–Kti13 heterodimer revealed that the RCC1-like β-propeller of Kti13 restricts access to the DPH3 iron center, modulating electron transfer, and confirmed that both metal coordination and heterodimerization are required for diphthamide and tRNA modification functions.\",\n      \"evidence\": \"X-ray crystallography (2.9 Å and 1.45 Å resolution) with interface mutagenesis validated in vitro and in vivo\",\n      \"pmids\": [\"25543256\", \"25604895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Kti13-mediated restriction of iron access is dynamically regulated is unknown\", \"No structure of the full Dph1-Dph2-Dph3 ternary complex\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identifying the upstream reductase: Cbr1 was identified as the NADH-dependent cytochrome b5 reductase that reduces DPH3, linking cellular NADH/NAD+ ratio to both diphthamide biosynthesis and tRNA modification, completing the electron transfer chain from metabolism to translational control.\",\n      \"evidence\": \"Proteomic identification of Cbr1 as DPH3 interactor; in vitro NADH-dependent reduction assay; genetic validation in yeast\",\n      \"pmids\": [\"27694803\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Cbr1 is the sole reductase for DPH3 in vivo is not established\", \"Regulation of Cbr1-DPH3 interaction not characterized\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealing a dual function as iron donor: beyond electron transfer, DPH3 donates an iron atom to repair oxygen-damaged [3Fe-4S] clusters in Dph1-Dph2 back to functional [4Fe-4S], explaining how diphthamide biosynthesis operates under aerobic conditions.\",\n      \"evidence\": \"In vitro reconstitution with EPR, Mössbauer, and X-ray absorption spectroscopy under aerobic vs. anaerobic conditions\",\n      \"pmids\": [\"34154323\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether iron donation occurs in vivo under physiological O2 tensions not confirmed\", \"Source of iron reloading onto DPH3 after donation is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis of DPH3 engagement with the Dph1-Dph2 complex versus Elongator, how DPH3 is reloaded with iron after donation, and whether the developmental lethality in mice reflects loss of diphthamide, tRNA modification, or both pathways.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No ternary Dph1-Dph2-Dph3 structure available\", \"Relative contribution of diphthamide vs. tRNA modification to embryonic lethality not dissected\", \"Iron reloading mechanism onto DPH3 unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 7]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [2, 8, 9, 11]}\n    ],\n    \"complexes\": [\n      \"Dph1-Dph2-Dph3 diphthamide biosynthesis complex\",\n      \"Kti11-Kti13 heterodimer\"\n    ],\n    \"partners\": [\n      \"DPH1\",\n      \"DPH2\",\n      \"KTI13\",\n      \"CBR1\",\n      \"ELP2\",\n      \"ELP5\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}