znfx-1

id: E9P860
gene_symbol: znfx-1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:6239
  label: Caenorhabditis elegans
description: ZNFX-1 is a conserved NFX1-type zinc finger-containing RNA helicase that
  is the defining component of Z granules, a class of liquid-like condensates distinct
  from P granules. ZNFX-1 functions as a dedicated transgenerational RNAi inheritance
  factor, required for transmitting small RNA-mediated gene silencing signals across
  generations. The protein localizes to perinuclear nuage where it interacts with
  Argonaute proteins (WAGO-4, CSR-1, WAGO-1, PRG-1) and the RNA-dependent RNA polymerase
  EGO-1. ZNFX-1 and WAGO-4 co-localize in P granules during early germline development,
  then segregate to form Z granules during oocyte maturation. In adult germ cells,
  P granules, Z granules, and Mutator foci assemble into ordered tri-condensate "PZM"
  assemblages. ZNFX-1's helicase activity is essential for balancing epigenetic signals
  by preventing the spread of small RNA targeting toward the 5'-end of mRNAs, thereby
  maintaining stable transgenerational silencing.
existing_annotations:
- term:
    id: GO:0003723
    label: RNA binding
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: ZNFX-1 contains NF-X1 type zinc finger domains and functions within RNA/protein
      granules (Z granules). The protein interacts with Argonaute proteins (CSR-1,
      WAGO-1, WAGO-4, PRG-1) and the RdRP EGO-1, all of which are RNA-binding proteins
      involved in small RNA pathways [PMID:29775580, PMID:29769721]. RNA binding is
      consistent with its role in RNA helicase activity and small RNA-mediated gene
      silencing.
    action: ACCEPT
    reason: 'RNA binding is a core function supported by multiple lines of evidence:
      the protein contains NFX1-type zinc finger domains (4 copies), localizes to
      RNA/protein granules, and functions in small RNA pathways. IBA phylogenetic
      inference is appropriate given conservation across species.'
    supported_by:
    - reference_id: PMID:29775580
      supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
        as an epigenetic regulator and component of nuage that interacts with Argonaute
        systems to balance epigenetic inheritance
    - reference_id: PMID:29769721
      supporting_text: ZNFX-1 is a conserved RNA helicase, which marks RNAs produced
        from genes undergoing heritable silencing
- term:
    id: GO:0031048
    label: regulatory ncRNA-mediated heterochromatin formation
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: This annotation is inferred from S. pombe ortholog hrr1 (SPCC1739.03).
      While ZNFX-1 is involved in regulatory ncRNA-mediated gene silencing, its primary
      function in C. elegans appears to be cytoplasmic post-transcriptional silencing
      rather than heterochromatin formation. The key role of ZNFX-1 is transgenerational
      siRNA inheritance via cytoplasmic Z granules, not nuclear heterochromatin assembly.
    action: MODIFY
    reason: While the S. pombe ortholog hrr1 functions in heterochromatin formation,
      C. elegans ZNFX-1 functions primarily in cytoplasmic transgenerational RNAi
      inheritance. The term is too specific to the nuclear heterochromatin pathway.
      A more appropriate term would reflect its role in siRNA-mediated gene silencing.
    proposed_replacement_terms:
    - id: GO:0140766
      label: siRNA-mediated post-transcriptional gene silencing
    - id: GO:0031047
      label: regulatory ncRNA-mediated gene silencing
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: The data establish that ZNFX-1 is a dedicated RNAi inheritance
        factor
    - reference_id: UniProt:E9P860
      supporting_text: Epigenetic inheritance factor which, in association with the
        Argonaute protein wago-4, mediates small RNA-directed transgenerational epigenetic
        inheritance
- term:
    id: GO:0031380
    label: nuclear RNA-directed RNA polymerase complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: This annotation is inferred from S. pombe ortholog hrr1. However, in
      C. elegans, ZNFX-1 does not localize to the nucleus but rather to cytoplasmic
      perinuclear granules (Z granules). While ZNFX-1 interacts with the RdRP EGO-1,
      this interaction occurs in cytoplasmic nuage, not in a nuclear complex. The
      primary localization of ZNFX-1 is to Z granules adjacent to P granules in the
      perinuclear region.
    action: REMOVE
    reason: UniProt explicitly states ZNFX-1 localizes to "Cytoplasm, perinuclear
      region" and "Cytoplasmic granule" (Z granules). There is no evidence for nuclear
      localization in C. elegans. The S. pombe ortholog hrr1 has a distinct nuclear
      function that does not apply to the C. elegans protein.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: Later in germline development, ZNFX-1 and WAGO-4 separate from
        P granules to define an independent liquid-like condensate that we term the
        Z granule
    - reference_id: PMID:29775580
      supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
        as an epigenetic regulator and component of nuage
- term:
    id: GO:0000166
    label: nucleotide binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: ZNFX-1 contains a UvrD-like helicase ATP-binding domain (residues 1040-1545)
      and has been assigned EC 3.6.4.13 (RNA helicase) activity. The protein has a
      characterized ATP binding site (residues 1061-1068). Nucleotide binding is consistent
      with its helicase function.
    action: ACCEPT
    reason: This is a parent term of ATP binding (GO:0005524) which is directly supported
      by the domain architecture. While less specific, it is not incorrect. The IEA
      annotation from UniProt keyword mapping is valid.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: Alternative splicing; ATP-binding; Cytoplasm; Helicase; Hydrolase
- term:
    id: GO:0003723
    label: RNA binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: Duplicate of the IBA annotation. ZNFX-1 contains NFX1-type zinc finger
      domains and functions in RNA/protein granules involved in small RNA pathways.
      RNA binding is consistent with its role as an RNA helicase.
    action: ACCEPT
    reason: While this duplicates the IBA annotation, both are valid. The IEA annotation
      from UniProt keyword mapping independently supports RNA binding based on domain
      content.
    supported_by:
    - reference_id: PMID:29775580
      supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
        as an epigenetic regulator and component of nuage that interacts with Argonaute
        systems to balance epigenetic inheritance
- term:
    id: GO:0003724
    label: RNA helicase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000003
  review:
    summary: ZNFX-1 is assigned EC 3.6.4.13 (RNA helicase) and contains a UvrD-like
      helicase ATP-binding domain. Mutagenesis studies show that mutations in the
      helicase domain (K1067A in Walker A motif, L1530F, Y1562C) disrupt RNA-induced
      gene silencing, demonstrating the functional importance of helicase activity.
    action: ACCEPT
    reason: This is a core molecular function of ZNFX-1. The protein is classified
      as an RNA helicase (EC 3.6.4.13) and contains the characteristic helicase domain.
      Mutagenesis of helicase domain residues abolishes function.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: EC=3.6.4.13 {ECO:0000305|PubMed:29775580}
    - reference_id: PMID:29769721
      supporting_text: ZK1067.2 encodes a 2443 amino acid protein that contains a
        superfamily one (SF1) RNA helicase domain and a Zn finger domain
- term:
    id: GO:0004386
    label: helicase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: This is a parent term of RNA helicase activity (GO:0003724). ZNFX-1 contains
      InterPro domain IPR041677 (DNA2/NAM7_AAA_11) which supports helicase activity
      classification.
    action: ACCEPT
    reason: Valid parent term of the more specific RNA helicase activity. The annotation
      is consistent with domain architecture and functional data.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: ZK1067.2 encodes a 2443 amino acid protein that contains a
        superfamily one (SF1) RNA helicase domain and a Zn finger domain
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: ZNFX-1 has a characterized ATP binding site at residues 1061-1068 within
      the UvrD-like helicase ATP-binding domain. The Walker A motif lysine (K1067)
      is critical for function, as K1067A mutation causes defective RNA-induced gene
      silencing.
    action: ACCEPT
    reason: ATP binding is a core molecular function supported by domain architecture
      and validated by mutagenesis.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: Alternative splicing; ATP-binding; Cytoplasm; Helicase; Hydrolase
    - reference_id: UniProt:E9P860
      supporting_text: 'K->A: In ne4382; defective RNA-induced gene silencing'
- term:
    id: GO:0005634
    label: nucleus
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: This annotation is based on InterPro domain IPR000967 (NF-X1 zinc finger),
      which in some family members is associated with nuclear localization. However,
      experimental evidence in C. elegans shows ZNFX-1 localizes to cytoplasmic perinuclear
      granules (Z granules), not the nucleus itself.
    action: REMOVE
    reason: Experimental evidence from multiple publications demonstrates cytoplasmic
      localization to Z granules and perinuclear region, not nuclear localization.
      UniProt subcellular location explicitly lists "Cytoplasm, perinuclear region"
      and "Cytoplasmic granule" with no nuclear localization.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: Later in germline development, ZNFX-1 and WAGO-4 separate from
        P granules to define an independent liquid-like condensate that we term the
        Z granule
    - reference_id: UniProt:E9P860
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm, perinuclear region'
    - reference_id: PMID:32843637
      supporting_text: In the adult germline, both proteins colocalise to P granules
        from the mitotic zone to the pachytene region
- term:
    id: GO:0005694
    label: chromosome
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  review:
    summary: This annotation from ARBA machine learning model (ARBA00026361) is not
      supported by experimental evidence. ZNFX-1 localizes to cytoplasmic granules
      (Z granules, P granules), not chromosomes. There is no evidence for direct chromosome
      association.
    action: REMOVE
    reason: No experimental evidence supports chromosome localization. The protein
      functions in cytoplasmic RNA granules and perinuclear nuage. This appears to
      be an erroneous inference.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: Later in germline development, ZNFX-1 and WAGO-4 separate from
        P granules to define an independent liquid-like condensate that we term the
        Z granule
    - reference_id: PMID:29775580
      supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
        as an epigenetic regulator and component of nuage
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: ZNFX-1 localizes to cytoplasmic Z granules and P granules. UniProt explicitly
      states "Cytoplasm" and "Cytoplasm, perinuclear region" as subcellular locations.
    action: ACCEPT
    reason: Cytoplasmic localization is well-supported by experimental evidence from
      multiple publications. This is a valid general localization term.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm, perinuclear region'
    - reference_id: PMID:29769721
      supporting_text: Later in germline development, ZNFX-1 and WAGO-4 separate from
        P granules to define an independent liquid-like condensate that we term the
        Z granule
- term:
    id: GO:0008270
    label: zinc ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: ZNFX-1 contains four NF-X1-type zinc finger domains (at positions 1769-1791,
      1853-1873, 1912-1930, 2027-2044). These domains require zinc ions for structural
      integrity and function.
    action: ACCEPT
    reason: Zinc ion binding is directly supported by the presence of multiple NFX1-type
      zinc finger domains in the protein sequence. This is a valid molecular function
      annotation.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: RNA-mediated gene silencing; Zinc; Zinc-finger
- term:
    id: GO:0016787
    label: hydrolase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: ZNFX-1 is classified as EC 3.6.4.13 (RNA helicase), which is a subclass
      of hydrolase activity. The protein catalyzes ATP hydrolysis coupled to RNA unwinding.
    action: ACCEPT
    reason: This is a valid parent term of ATP hydrolysis activity, consistent with
      the RNA helicase function.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: EC=3.6.4.13 {ECO:0000305|PubMed:29775580}
- term:
    id: GO:0016887
    label: ATP hydrolysis activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000116
  review:
    summary: ZNFX-1 catalyzes ATP hydrolysis as part of its RNA helicase function.
      UniProt assigns the reaction "ATP + H2O = ADP + phosphate + H(+)" with Rhea
      reference RHEA:13065.
    action: ACCEPT
    reason: ATP hydrolysis is the energy source for RNA helicase activity. This is
      a core molecular function directly supported by the EC classification and Rhea
      reaction mapping.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: Reaction=ATP + H2O = ADP + phosphate + H(+)
- term:
    id: GO:0031047
    label: regulatory ncRNA-mediated gene silencing
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: ZNFX-1 is essential for small RNA-mediated transgenerational gene silencing.
      It functions in the RNAi inheritance pathway, maintaining silencing signals
      across generations. znfx-1 mutants respond normally to RNAi but cannot transmit
      silencing to progeny.
    action: ACCEPT
    reason: This is a core biological process function of ZNFX-1. The protein is dedicated
      to transgenerational siRNA-mediated gene silencing in the germline.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: The data establish that ZNFX-1 is a dedicated RNAi inheritance
        factor
    - reference_id: UniProt:E9P860
      supporting_text: Plays a role in small RNA- induced gene silencing in the germline
        (PubMed:29775580)
- term:
    id: GO:0046872
    label: metal ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: This is a parent term of zinc ion binding. ZNFX-1 contains four NFX1-type
      zinc finger domains that bind zinc ions.
    action: ACCEPT
    reason: Valid parent term of zinc ion binding, consistent with the zinc finger
      domain content.
    supported_by:
    - reference_id: UniProt:E9P860
      supporting_text: Metal-binding; Nucleotide-binding; Reference proteome
- term:
    id: GO:0048471
    label: perinuclear region of cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: ZNFX-1 localizes to perinuclear nuage where it defines Z granules. P
      granules, Z granules, and Mutator foci form ordered PZM assemblages in the perinuclear
      region of germline cells.
    action: ACCEPT
    reason: Perinuclear localization is strongly supported by experimental evidence.
      This is a core localization for ZNFX-1 in germline cells.
    supported_by:
    - reference_id: PMID:29775580
      supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
        as an epigenetic regulator and component of nuage
    - reference_id: PMID:29769721
      supporting_text: In adult germ cells, GFP::ZNFX-1 was concentrated in foci that
        were distributed in a perinuclear pattern around nuclei
- term:
    id: GO:0120279
    label: Z granule
  evidence_type: IDA
  original_reference_id: PMID:29769721
  review:
    summary: ZNFX-1 is the defining marker of Z granules, a class of liquid-like condensates
      distinct from P granules. Z granules were named for ZNFX-1, which defines these
      structures. The protein localizes to Z granules during oocyte maturation and
      in adult germ cells.
    action: NEW
    reason: Z granule localization is the most specific and characteristic localization
      for ZNFX-1. The granules are named after this protein. This annotation should
      have IDA evidence based on direct microscopy observation.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: Later in germline development, ZNFX-1 and WAGO-4 separate from
        P granules to define an independent liquid-like condensate that we term the
        Z granule
    - reference_id: PMID:29775580
      supporting_text: recently identified subdomains of nuage, including ZNFX-1 granules
        or "Z-granules," may define spatial and temporal zones of molecular activity
        during epigenetic regulation
- term:
    id: GO:0043186
    label: P granule
  evidence_type: IDA
  original_reference_id: PMID:29769721
  review:
    summary: ZNFX-1 co-localizes with WAGO-4 in P granules in germline blastomeres
      until the 100-cell stage. The protein also localizes to P granules before Z
      granule segregation during development. In adult germline, ZNFX-1 co-localizes
      with DEPS-1 in P granules.
    action: NEW
    reason: P granule localization is experimentally demonstrated and represents an
      important developmental aspect of ZNFX-1 localization before Z granule segregation.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: GFP::ZNFX-1 and GFP::WAGO-4 colocalized with PGL-1::TagRFP
        in P1-P3 germline blastomeres, suggesting that ZNFX-1 and WAGO-4 are P granule
        factors
    - reference_id: PMID:32843637
      supporting_text: In the adult germline, both proteins colocalise to P granules
        from the mitotic zone to the pachytene region
- term:
    id: GO:0140766
    label: siRNA-mediated post-transcriptional gene silencing
  evidence_type: IMP
  original_reference_id: PMID:29769721
  review:
    summary: ZNFX-1 is required for transgenerational siRNA inheritance. znfx-1 mutants
      respond normally to RNAi but cannot transmit silencing to progeny, demonstrating
      a specific role in siRNA inheritance rather than the initial silencing response.
    action: NEW
    reason: This is more specific than the general "regulatory ncRNA-mediated gene
      silencing" term and accurately reflects the siRNA-specific function of ZNFX-1.
    supported_by:
    - reference_id: PMID:29769721
      supporting_text: The data establish that ZNFX-1 is a dedicated RNAi inheritance
        factor
    - reference_id: UniProt:E9P860
      supporting_text: Plays a role in small RNA- induced gene silencing in the germline
        (PubMed:29775580)
references:
- id: PMID:29769721
  title: Spatiotemporal regulation of liquid-like condensates in epigenetic inheritance
  findings:
  - statement: ZNFX-1 defines Z granules, liquid-like condensates distinct from P
      granules
    supporting_text: Later in germline development, ZNFX-1 and WAGO-4 separate from
      P granules to define an independent liquid-like condensate that we term the
      Z granule
  - statement: ZNFX-1 and WAGO-4 act cooperatively for transgenerational siRNA inheritance
    supporting_text: WAGO-4 functions with ZNFX-1 to transmit RNA-based epigenetic
      information across generations
  - statement: Z granules form tri-condensate PZM assemblages with P granules and
      Mutator foci
    supporting_text: In adult germ cells, Z granules assemble into ordered tri-condensate
      assemblages with P granules and Mutator foci, which we term PZM granules
  - statement: ZNFX-1 is a dedicated RNAi inheritance factor
    supporting_text: The data establish that ZNFX-1 is a dedicated RNAi inheritance
      factor
  - statement: ZNFX-1 is a conserved RNA helicase in small RNA pathways
    supporting_text: ZNFX-1 is a conserved RNA helicase, which marks RNAs produced
      from genes undergoing heritable silencing
- id: PMID:29775580
  title: ZNFX-1 Functions within Perinuclear Nuage to Balance Epigenetic Signals
  findings:
  - statement: ZNFX-1 interacts with Argonaute systems
    supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
      as an epigenetic regulator and component of nuage that interacts with Argonaute
      systems to balance epigenetic inheritance
  - statement: ZNFX-1 prevents spread of epigenetic signals toward 5'-end of target
      mRNAs
    supporting_text: Our findings suggest that ZNFX-1 promotes the 3' recruitment
      of machinery that propagates the small RNA epigenetic signal and thus counteracts
      a tendency for Argonaute targeting to shift 5' along the mRNA
  - statement: Z granules are subdomains of nuage named for ZNFX-1
    supporting_text: recently identified subdomains of nuage, including ZNFX-1 granules
      or "Z-granules," may define spatial and temporal zones of molecular activity
      during epigenetic regulation
- id: PMID:32843637
  title: DEPS-1 is required for piRNA-dependent silencing and PIWI condensate organisation
    in Caenorhabditis elegans
  findings:
  - statement: ZNFX-1 co-localizes with DEPS-1 in P granules in adult germline
    supporting_text: In the adult germline, both proteins colocalise to P granules
      from the mitotic zone to the pachytene region
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000003
  title: Gene Ontology annotation based on Enzyme Commission mapping
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping
  findings: []
- id: GO_REF:0000116
  title: Automatic Gene Ontology annotation based on Rhea mapping
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
core_functions:
- description: ZNFX-1 functions as an RNA helicase dedicated to transgenerational
    siRNA inheritance, maintaining small RNA-mediated gene silencing signals across
    generations.
  molecular_function:
    id: GO:0003724
    label: RNA helicase activity
  directly_involved_in:
  - id: GO:0031047
    label: regulatory ncRNA-mediated gene silencing
  - id: GO:0140766
    label: siRNA-mediated post-transcriptional gene silencing
  locations:
  - id: GO:0120279
    label: Z granule
  - id: GO:0048471
    label: perinuclear region of cytoplasm
  supported_by:
  - reference_id: PMID:29769721
    supporting_text: The data establish that ZNFX-1 is a dedicated RNAi inheritance
      factor
  - reference_id: PMID:29775580
    supporting_text: we identify the deeply conserved helicase-domain protein, ZNFX-1,
      as an epigenetic regulator and component of nuage that interacts with Argonaute
      systems to balance epigenetic inheritance
proposed_new_terms: []
suggested_questions:
- question: What is the precise mechanism by which ZNFX-1 helicase activity prevents
    5'-ward spread of small RNA signals on target mRNAs?
- question: How is ZNFX-1 inherited from oocyte to embryo, and what determines Z granule
    segregation from P granules during development?
suggested_experiments:
- description: In vitro helicase assays with purified ZNFX-1 to determine substrate
    specificity (ssRNA vs dsRNA, specific RNA sequences). This would reveal the molecular
    substrate requirements for ZNFX-1 function.
  hypothesis: ZNFX-1 preferentially unwinds specific RNA structures involved in siRNA
    biogenesis
  experiment_type: biochemical assay
- description: Proximity labeling (BioID or APEX) to comprehensively identify ZNFX-1
    interacting proteins in Z granules vs P granules. This would reveal the complete
    protein composition of Z granules and how it differs from P granules.
  hypothesis: Z granules contain a distinct proteome specialized for transgenerational
    inheritance
  experiment_type: proteomics
tags:
- caeel-p-granules