id: Q6P3W2
gene_symbol: DNAJC24
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: DNAJC24 (DnaJ homolog subfamily C member 24; also DPH4 / ZCSL3, Diphthamide biosynthesis protein 4) is a small cytoplasmic J-domain co-chaperone of the HSP70 system that also functions in diphthamide biosynthesis. It comprises an N-terminal J-domain (with the canonical HPD motif) and a C-terminal DPH-type CSL metal-binding domain that can coordinate either zinc or iron. Through its J-domain it stimulates the ATPase activity of HSP70-type chaperones; its CSL domain binds metal ions, and iron binding promotes oligomerization and confers redox/electron-carrier activity. DNAJC24 participates in the conserved multi-step diphthamide pathway that installs the diphthamide modification on a specific histidine of translation elongation factor 2 (EEF2), the residue targeted by diphtheria toxin and Pseudomonas exotoxin A.
alternative_products:
- name: '1'
  id: Q6P3W2-1
- name: '2'
  id: Q6P3W2-2
  sequence_note: VSP_056274
existing_annotations:
- term:
    id: GO:0001671
    label: ATPase activator activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: As a J-domain protein, DNAJC24/DPH4 stimulates the ATPase activity of HSP70-type chaperones. This phylogenetic inference is directly confirmed for the human protein.
    action: ACCEPT
    reason: The J-domain of DPH4 catalytically stimulates HSP70 ATPase activity; this is the canonical molecular function of the gene, supported by both orthology and direct experimental evidence.
    supported_by:
    - reference_id: PMID:22367199
      supporting_text: catalytically stimulate the ATPase activity of Hsp70
- term:
    id: GO:0008198
    label: ferrous iron binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: The CSL metal-binding domain of DPH4 binds iron (in addition to zinc), conferring redox/electron-carrier activity. Supported experimentally for the human protein.
    action: ACCEPT
    reason: DPH4's CSL domain binds iron in solution (loss on the C139S mutation), a genuine molecular function corroborated by direct experimental evidence.
    supported_by:
    - reference_id: PMID:22367199
      supporting_text: Dph4 possesses the intrinsic ability to bind iron in solution
- term:
    id: GO:0005856
    label: cytoskeleton
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Cytoplasm/cytoskeleton localization is annotated from the UniProt subcellular location (by similarity). The cytoskeletal association is weakly supported.
    action: KEEP_AS_NON_CORE
    reason: The cytoplasm-cytoskeleton localization is by-similarity (ECO:0000250) rather than direct; DPH4 is a cytoplasmic co-chaperone, but cytoskeletal localization is not central to its characterized function.
    supported_by:
    - reference_id: file:human/DNAJC24/DNAJC24-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm, cytoskeleton'
- term:
    id: GO:0015629
    label: actin cytoskeleton
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: is_active_in
  review:
    summary: Actin-cytoskeleton localization transferred by orthology from the mouse protein. There is no direct human functional evidence linking DPH4 to the actin cytoskeleton.
    action: MARK_AS_OVER_ANNOTATED
    reason: This is an Ensembl-Compara orthology transfer from mouse with no direct human evidence; DPH4's characterized roles are HSP70 co-chaperone and diphthamide biosynthesis, not actin-cytoskeleton activity.
    supported_by:
    - reference_id: file:human/DNAJC24/DNAJC24-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm, cytoskeleton'
- term:
    id: GO:0017183
    label: protein histidyl modification to diphthamide
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: DPH4 participates in the diphthamide biosynthesis pathway, a post-translational modification of a histidine in EEF2. This is the gene's defining biological process and is supported experimentally.
    action: ACCEPT
    reason: DPH4 plays a documented role in diphthamide biosynthesis (the EEF2 histidine modification); this is the core biological process, supported by functional studies and pathway membership.
    supported_by:
    - reference_id: file:human/DNAJC24/DNAJC24-uniprot.txt
      supporting_text: Plays a role in the diphthamide biosynthesis, a post-translational modification of histidine which occurs in translation elongation factor 2 (EEF2)
- term:
    id: GO:0001671
    label: ATPase activator activity
  evidence_type: IDA
  original_reference_id: PMID:22367199
  qualifier: enables
  review:
    summary: Direct experimental evidence that DPH4 stimulates the ATPase activity of HSP70-type chaperones. The core molecular function of the J-protein.
    action: ACCEPT
    reason: IDA evidence that DPH4's J-domain stimulates HSP70 ATPase activity confirms its canonical co-chaperone molecular function.
    supported_by:
    - reference_id: PMID:22367199
      supporting_text: catalytically stimulate the ATPase activity of Hsp70
- term:
    id: GO:0006457
    label: protein folding
  evidence_type: TAS
  original_reference_id: PMID:22367199
  qualifier: involved_in
  review:
    summary: As an HSP70 co-chaperone, DPH4 is annotated to protein folding. This is a downstream process of the HSP70 machine it assists rather than autonomous foldase activity.
    action: KEEP_AS_NON_CORE
    reason: DPH4 is a J-domain co-chaperone that delivers substrates to and stimulates HSP70; protein folding is a generic downstream process, non-core relative to its ATPase-activator function and diphthamide role.
    supported_by:
    - reference_id: PMID:22367199
      supporting_text: The J-proteins sequester and deliver unfolded proteins to Hsp70 in the ATP-bound state
- term:
    id: GO:0008198
    label: ferrous iron binding
  evidence_type: IDA
  original_reference_id: PMID:22367199
  qualifier: enables
  review:
    summary: Direct experimental evidence that DPH4 binds iron through its CSL domain, conferring redox properties. A genuine molecular function.
    action: ACCEPT
    reason: IDA evidence (iron-binding lost in the C139S mutant) confirms DPH4 binds ferrous iron via its CSL metal-binding domain.
    supported_by:
    - reference_id: PMID:22367199
      supporting_text: Dph4 possesses the intrinsic ability to bind iron in solution
- term:
    id: GO:0008270
    label: zinc ion binding
  evidence_type: IDA
  original_reference_id: PMID:22367199
  qualifier: enables
  review:
    summary: Direct experimental and structural (NMR, PDB 2L6L) evidence that the CSL/DPH-type domain of DPH4 binds zinc ions via four conserved residues.
    action: ACCEPT
    reason: IDA/structural evidence that the DPH-type metal-binding domain coordinates zinc confirms this molecular function; the domain can bind either zinc or iron.
    supported_by:
    - reference_id: file:human/DNAJC24/DNAJC24-uniprot.txt
      supporting_text: The DPH-type metal-binding (MB) domain can bind either zinc or iron ions.
- term:
    id: GO:0032781
    label: positive regulation of ATP-dependent activity
  evidence_type: IDA
  original_reference_id: PMID:22367199
  qualifier: involved_in
  review:
    summary: A process-level annotation reflecting DPH4's stimulation of HSP70 ATPase activity. Redundant with the more informative ATPase activator activity molecular function.
    action: KEEP_AS_NON_CORE
    reason: This generic process term captures the same underlying activity as the ATPase activator activity MF; non-core because the MF term is more informative.
    supported_by:
    - reference_id: PMID:22367199
      supporting_text: catalytically stimulate the ATPase activity of Hsp70
references:
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:22367199
  title: Structure and mechanistic insights into novel iron-mediated moonlighting functions of human J-protein cochaperone, Dph4.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: "Cached publication title matches the YAML title; the text establishes DPH4 as a J-protein cochaperone whose J-domain stimulates HSP70 ATPase activity, with an iron/zinc-binding redox-active CSL domain, supporting the ATPase-activator MF and diphthamide-biosynthesis role. Primary reference cited in core_functions.supported_by."
  findings:
  - statement: DPH4 is a J-protein co-chaperone whose J-domain catalytically stimulates HSP70 ATPase activity; its CSL domain binds zinc or iron, and the iron-bound form is redox-active with electron-carrier activity, supporting moonlighting roles including diphthamide biosynthesis.
    reference_section_type: RESULTS
- id: PMID:22509046
  title: Immunotoxin resistance via reversible methylation of the DPH4 promoter is a unique survival strategy.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: "Cached publication title matches the YAML title; the text confirms DPH4 is required for diphthamide biosynthesis on EF2 and that DPH4 silencing renders EF2 refractory to immunotoxins, corroborating the diphthamide-biosynthesis biological-process role (functional/disease context rather than direct MF characterization)."
  findings:
  - statement: DPH4 is required for diphthamide biosynthesis on EEF2; silencing DPH4 (via promoter methylation) confers resistance to immunotoxins/diphtheria-toxin-like agents that ADP-ribosylate the diphthamide residue.
    reference_section_type: RESULTS
- id: file:human/DNAJC24/DNAJC24-uniprot.txt
  title: UniProt entry Q6P3W2 (DJC24_HUMAN), DnaJ homolog subfamily C member 24 (DPH4)
  findings:
  - statement: Stimulates the ATPase activity of HSP70-type chaperones (enhanced by iron binding); CSL domain binds zinc or iron; iron-bound form is redox-active; participates in diphthamide biosynthesis on EEF2; cytoplasmic.
    reference_section_type: OTHER
core_functions:
- description: J-domain co-chaperone that catalytically stimulates the ATPase activity of HSP70-type chaperones, delivering substrates to HSP70 in the ATP-bound state.
  molecular_function:
    id: GO:0001671
    label: ATPase activator activity
  locations:
  - id: GO:0005737
    label: cytoplasm
  supported_by:
  - reference_id: PMID:22367199
    supporting_text: catalytically stimulate the ATPase activity of Hsp70
- description: Component of the diphthamide biosynthesis pathway that installs the diphthamide modification on a specific histidine of translation elongation factor 2 (EEF2); its CSL domain binds zinc/iron and the iron-bound form is redox-active.
  locations:
  - id: GO:0005737
    label: cytoplasm
  supported_by:
  - reference_id: file:human/DNAJC24/DNAJC24-uniprot.txt
    supporting_text: Plays a role in the diphthamide biosynthesis, a post-translational modification of histidine which occurs in translation elongation factor 2 (EEF2)
  - reference_id: PMID:22367199
    supporting_text: Dph4 possesses the intrinsic ability to bind iron in solution
  directly_involved_in:
  - id: GO:0017183
    label: protein histidyl modification to diphthamide
proposed_new_terms: []
suggested_questions:
- question: Which HSP70 paralog(s) does DPH4 stimulate in vivo, and is the J-domain co-chaperone activity required for diphthamide biosynthesis or separable from it?
- question: Is the iron-dependent redox/electron-carrier activity of DPH4 physiologically relevant to the radical-SAM chemistry of the diphthamide pathway (e.g. DPH1-DPH2)?
suggested_experiments:
- description: Reconstitute the diphthamide pathway in vitro with DPH1-DPH7 and test whether DPH4 J-domain (HPD) mutants or iron-binding (C139S) mutants impair EEF2 diphthamide formation.
- description: Measure DPH4-stimulated ATPase activity of candidate HSP70 partners (HSPA8, HSPA9) and map which clients require DPH4 hand-off.
- description: Knockout DPH4 in cells and assay EEF2 diphthamidation and sensitivity to diphtheria toxin / Pseudomonas exotoxin A to confirm its in-vivo pathway role.