wago-4 (F58G1.1, O62275) — research notes

Curator research journal. Provenance is recorded inline as [PMID:xxxx "verbatim quote"].
All quotes below were verified as verbatim substrings of the cached publications/PMID_*.md.

Identity

• Gene: wago-4 / F58G1.1 / WBGene00010263. UniProt O62275 (WAGO4_CAEEL, 965 aa).
• Family: Argonaute family, WAGO (worm-specific Argonaute) subfamily. Domains: PAZ (318–428) and Piwi (594–924) [from UniProt record].
• One of the ~27 C. elegans Argonautes; a secondary Argonaute of the WAGO clade.

What is KNOWN (wago-4-specific, experimental)

Small-RNA binding / molecular function

• WAGO-4 binds secondary 22G-RNAs and their target mRNAs (not miRNAs):
  PMID:29791857
• Its 22G-RNAs overlap the CSR-1 germline gene cohort and carry 3′ uridylation:
  PMID:29791857
• 22G-RNAs are RdRP-derived endo-siRNAs (~22 nt, 5′ G) — i.e. siRNAs, not miRNAs. So the
  correct MF is siRNA binding (GO:0035197), and the IBA miRNA binding (GO:0035198) is a
  mischaracterization inherited from the pan-Argonaute tree.

Catalytic (slicer) activity — likely ABSENT

• The downstream/secondary WAGO-clade Argonautes lack the catalytic residues for target cleavage:
  PMID:17110334
• UniProt concurs (MISCELLANEOUS): "Members of the WAGO (worm-specific argonaute) subfamily
  lack conserved metal-binding residues found in other argonaute proteins and probably do not
  cleave target mRNAs directly." (ECO:0000303|PubMed:17110334).
• => The IBA RNA endonuclease activity (GO:0004521), propagated from catalytically active
  Argonautes elsewhere in the family tree, is not warranted for WAGO-4. This is the crux of the
  "is it catalytically active?" question and remains formally unproven for WAGO-4 (see gaps).

Biological process — RNAi inheritance / germline PTGS

• WAGO-4 is required for the inheritance (transgenerational maintenance) of RNAi:
  PMID:29791857
  PMID:29791857
• Independent screen (Wan/Kennedy) reached the same conclusion:
  PMID:29769721
• Essential for germline RNAi (Sendoel):
  PMID:30728462
• Dosage-sensitive positive regulator of silencing: WAGO-4 overexpression enhances RNAi:
  PMID:30728462
  (consistent with the general secondary-Argonaute behavior PMID:17110334)

Partners / mechanism of transgenerational transport

• Physically and functionally partners with the helicase ZNFX-1:
  PMID:29769721
• WAGO-4 is required for ZNFX-1 to engage target mRNA:
  PMID:29769721
  (verbatim string in text: "in wago-4 mutant animals, ZNFX-1 faile")
• Genetically/physically interacts with the KH-domain RBP MINA-1:
  PMID:30728462

Localization (experimental)

• Cytoplasmic; germline perinuclear foci:
  PMID:29791857
• P-granule associated (transient component), adjacent to P granules:
  PMID:30728462
• With ZNFX-1, localizes to P granules in early germline blastomeres:
  PMID:29769721
• Defines a distinct condensate, the Z granule, between P granules and Mutator foci:
  PMID:29769721
• Germline-restricted expression (UniProt TISSUE SPECIFICITY): hermaphrodite germline and oocytes;
  not in soma.

Heterochromatin / chromatin (redundant, indirect)

• In Gu 2012, wago-4 (F58G1.1, allele tm1019) was tested only as one member of the 6-gene "MAGO"
  secondary-Argonaute group required for dsRNA-triggered H3K9me3 chromatin modification:
  PMID:22231482
  PMID:22231482
  => This is a genetic-redundancy (group knockout) contribution; WAGO-4's own core role is
  cytoplasmic PTGS/inheritance, and heterochromatin formation is executed by the nuclear WAGOs
  (HRDE-1/NRDE-3). Keep the IGI (experimental) but as non-core.

What is NOT known (knowledge gaps)

1. Is WAGO-4 catalytically active? It lacks the conserved catalytic/metal-binding residues and
   "probably" does not slice, but no biochemical assay directly tests WAGO-4 slicer activity; a
   non-catalytic, siRNA-guided mRNA-binding/silencing mechanism is inferred, not proven.
2. Full target-mRNA repertoire and the silencing readout. WAGO-4 22G-RNAs overlap the CSR-1
   cohort, yet CSR-1 and WAGO-4 have divergent (protective vs silencing/inheritance) outputs; how
   the same target space yields different outcomes, and the direct mRNA-level consequence of
   WAGO-4 binding (destabilization vs translational block vs licensing), is undefined.
3. Mechanism of transgenerational transport. WAGO-4 and ZNFX-1 mark a Z granule between P
   granules and Mutator foci, but how 22G-RNA/mRNA information is physically handed across the
   PZM assemblage and transmitted to progeny is a model, not a mechanism.

Annotation-review plan (summary)

• GO:0035198 miRNA binding (IBA) → MODIFY to GO:0035197 siRNA binding (binds 22G-RNAs, not miRNAs).
• GO:0004521 RNA endonuclease activity (IBA) → REMOVE (WAGO subfamily lacks catalytic residues; over-propagated IBA).
• GO:0005634 nucleus (IBA) → REMOVE (WAGO-4 is a cytoplasmic Argonaute; no nuclear-action evidence; over-propagated IBA).
• GO:0003676 nucleic acid binding (IEA) / GO:0003723 RNA binding (IEA) → generic parents; KEEP_AS_NON_CORE.
• GO:0003727 single-stranded RNA binding (IBA) → ACCEPT (binds ss 22G guide + mRNA), non-core relative to siRNA binding.
• GO:0005737 cytoplasm (IBA/IEA/EXP), GO:0048471 perinuclear region (IEA), GO:0036464 cytoplasmic RNP granule (IBA) → ACCEPT; RNP granule refined to P granule in core_functions.
• GO:0016442 RISC complex (IBA) → ACCEPT.
• GO:0035194 regulatory ncRNA-mediated PTGS (IBA) → ACCEPT (core BP).
• GO:0060966 regulation of gene silencing by regulatory ncRNA (IMP, PMID:30728462) → ACCEPT (experimental).
• GO:0031048 regulatory ncRNA-mediated heterochromatin formation (IGI, PMID:22231482) → KEEP_AS_NON_CORE (redundant MAGO-group, indirect for a cytoplasmic Ago).

Deep research provenance

Falcon deep research (just deep-research-falcon worm wago-4 --fallback perplexity-lite) was
launched but the Edison endpoint was congested (multiple concurrent gene jobs) and had not
returned a file at review time. This review is therefore built entirely on the cached primary
literature below plus the UniProt/GOA records; every claim is PMID-anchored and independently
verified against the cached full text/abstract. No file: deep-research quotes are used, so the
review is self-contained. (If a real falcon file lands later it can be added as a supplementary
reference; it is not required for any conclusion here.) No annotation required UNDECIDED — each
had sufficient primary-literature evidence.

References used (all cached)

• PMID:29791857 Xu et al. 2018 Cell Rep — abstract-only cache; WAGO-4 = cytoplasmic Ago for RNAi inheritance; binds 22G-RNAs + mRNA targets.
• PMID:29769721 Wan et al. 2018 Nature — full text; Z granule, ZNFX-1 interaction, RNAi inheritance.
• PMID:30728462 Sendoel et al. 2019 Cell Death Differ — full text; MINA-1/WAGO-4 network; germline RNAi; P-granule.
• PMID:17110334 Yigit et al. 2006 Cell — abstract-only; WAGO clade lacks cleavage residues; secondary Argonautes act downstream.
• PMID:22231482 Gu et al. 2012 Nat Genet — full text; MAGO 6-gene group (incl. F58G1.1/wago-4) required for RNAi-triggered H3K9me3.