PGL-3 (C18G1.4, UniProt G5EBV6) is a constitutive PGL-family P-granule scaffold protein and paralog of PGL-1, present in germline P granules throughout development. Its core molecular activity is acting as a molecular condensate scaffold - PGL-1 and PGL-3 self-associate via a structured dimerization domain (DD, ~aa 205-447; a 13-helix homodimer forming a positively charged channel) and recruit mRNPs through a C-terminal RGG box, nucleating and maintaining the P-granule condensate in an RNA-dependent manner (it drives liquid-liquid phase separation in vitro). The same DD also confers a modest, conserved, guanosine-specific single-stranded RNase activity (RNase T1-like; EC 4.6.1.24) demonstrated for the PGL family including Ce-PGL-3, though this enzymatic activity may not be strictly required for fertility (an RNase-defective PGL-1 Q342A mutant remained fertile). PGL-3 functions redundantly with PGL-1 in germline development - pgl-3 single mutants are largely normal but pgl-1; pgl-3 double mutants are markedly sterile. By maintaining P-granule integrity, PGL-3 helps preserve germline identity/totipotency (antagonizing somatic differentiation programs) and protects germ cells from excessive apoptosis. It is selectively recognized by the autophagy adapter SEPA-1 for degradation of P granules in the soma, ensuring germline-restricted localization.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003723 RNA binding | IEA GO_REF:0000043 | ACCEPT | Summary: RNA binding is supported by experimental evidence showing the RGG box domain binds RNA, though this IEA annotation is too generic compared to the specific ribonuclease function. Reason: PGL-3 does bind RNA through its C-terminal RGG box domain (confirmed experimentally). While generic, this is a core molecular function that enables both its ribonuclease activity and P granule assembly roles. RNA binding is a distinct MF from the guanyl-specific ribonuclease activity (captured separately by GO:0046589/GO:0004521), so no replacement term is proposed here. Supporting Evidence: PMID:26787882 PGL-1 DD is a guanosine-specific, single-stranded endonuclease PMID:15238518 PGL-3 is associated with P granules at all stages of development file:worm/pgl-3/pgl-3-deep-research-falcon.md containing a C-terminal **RGG box** (an RNA-binding motif) with multiple RGG repeats |
| GO:0004518 nuclease activity | IEA GO_REF:0000043 | MODIFY | Summary: This broad nuclease activity term is correct but too generic - PGL-3 is specifically a guanyl-specific ribonuclease. Reason: While technically correct as PGL-3 is indeed a nuclease, this annotation is too broad. The protein has been experimentally characterized as a guanyl-specific single-stranded RNA endonuclease (ribonuclease T1 activity). Proposed replacements: ribonuclease T1 activity Supporting Evidence: PMID:26787882 PGL-1 DD is a guanosine-specific, single-stranded endonuclease file:worm/pgl-3/pgl-3-deep-research-falcon.md cleavage activity was also observed for **Ce-PGL-3**, supporting conserved RNase activity across PGL paralogs |
| GO:0004519 endonuclease activity | IEA GO_REF:0000043 | MODIFY | Summary: Correct but too generic - PGL-3 is specifically an RNA endonuclease with guanosine specificity. Reason: While PGL-3 is indeed an endonuclease, this term is too broad. The protein specifically cleaves single-stranded RNA after guanosine residues (ribonuclease T1 activity). Proposed replacements: ribonuclease T1 activity Supporting Evidence: PMID:26787882 discover unexpectedly that PGL-1 DD is a guanosine-specific, single-stranded endonuclease file:worm/pgl-3/pgl-3-deep-research-falcon.md Cleavage requires **ssRNA**, a **G** residue, and the **2β²-OH**; DNA or **2β²-fluoroguanosine** blocks activity |
| GO:0016787 hydrolase activity | IEA GO_REF:0000043 | REMOVE | Summary: Too broad and uninformative - should be replaced with the specific ribonuclease T1 activity. Reason: This extremely broad term provides no useful information about PGL-3 function. The specific enzymatic activity (guanyl-specific ribonuclease) is well-characterized and should be annotated instead. Proposed replacements: ribonuclease T1 activity Supporting Evidence: PMID:26787882 PGL-1 DD is a guanosine-specific, single-stranded endonuclease |
| GO:0016829 lyase activity | IEA GO_REF:0000043 | ACCEPT | Summary: Correct - PGL-3 is a lyase (EC 4.6.1.24) that forms cyclic phosphate intermediates. Reason: This annotation is correct. PGL-3 has EC number 4.6.1.24, which classifies it as a lyase that catalyzes the formation of 2",3"-cyclic phosphate intermediates during RNA cleavage. This is distinct from simple hydrolase activity. Supporting Evidence: PMID:26787882 PGL-1 DD is a guanosine-specific, single-stranded endonuclease |
| GO:0046589 ribonuclease T1 activity | IEA GO_REF:0000003 | ACCEPT | Summary: Excellent annotation - this precisely captures PGL-3 enzymatic function as a guanyl-specific ribonuclease. Reason: This is the most specific and accurate molecular function annotation for PGL-3. The protein has been experimentally demonstrated to be a guanosine-specific single-stranded RNA endonuclease, which is exactly what ribonuclease T1 activity describes. The EC mapping (4.6.1.24) is correct. Supporting Evidence: PMID:26787882 PGL-1 DD is a guanosine-specific, single-stranded endonuclease PMID:26787882 PGLβs enzymatic activity is modest compared with classic guanosine-specific RNases, like RNase T1 file:worm/pgl-3/pgl-3-deep-research-falcon.md mechanistically resembling **RNase T1-like** cleavage specificity but much weaker |
| GO:0005515 protein binding | IPI PMID:19167332 SEPA-1 mediates the specific recognition and degradation of ... | KEEP AS NON CORE | Summary: Protein binding term based on the SEPA-1 interaction, which targets P-granule components for selective autophagic degradation in somatic cells. SEPA-1 is a distinct protein (autophagy adapter), so the prior proposed replacement of GO:0042802 identical protein binding was incorrect (that term applies only to PGL-3 homodimerization, captured separately). This heterotypic adapter-recognition interaction is a regulatory, non-core aspect of PGL-3 biology rather than its core scaffolding/enzymatic function. Reason: The PGL-3/SEPA-1 interaction is real and functionally relevant to regulated P-granule turnover, but it is a downstream regulatory event (autophagic clearance of maternal P granules from the soma), not a core function. The generic 'protein binding' term is uninformative for an adapter-recognition partner, and no more specific MF term is well supported here, so it is retained as non-core rather than modified. Supporting Evidence: PMID:19167332 SEPA-1 directly binds to the P granule component PGL-3 |
| GO:0004521 RNA endonuclease activity | IDA PMID:26787882 PGL germ granule assembly protein is a base-specific, single... | MODIFY | Summary: Correct but could be more specific - PGL-3 is a guanyl-specific ribonuclease (ribonuclease T1 activity). Reason: While this experimental annotation is correct, the more specific term GO:0046589 (ribonuclease T1 activity) better captures the guanosine-specific nature of PGL-3 enzymatic activity as demonstrated in the same paper. Proposed replacements: ribonuclease T1 activity Supporting Evidence: PMID:26787882 discover unexpectedly that PGL-1 DD is a guanosine-specific, single-stranded endonuclease PMID:26787882 PGL-1 guanosine-specific RNA endonuclease activity file:worm/pgl-3/pgl-3-deep-research-falcon.md PGL-family RNase activity shows **guanosine specificity** and requires RNA (not DNA) and the **2β²-OH**, consistent with an ssRNA endonuclease mechanism |
| GO:0042802 identical protein binding | IPI PMID:26787882 PGL germ granule assembly protein is a base-specific, single... | ACCEPT | Summary: Correct - PGL-3 forms homodimers through its dimerization domain, essential for P granule assembly. Reason: This annotation accurately captures PGL-3 ability to form homodimers, which is experimentally demonstrated and critical for P granule assembly. The dimerization domain has been structurally characterized. Supporting Evidence: PMID:26787882 PGL-1 DD has a novel 13 Ξ±-helix fold that creates a positively charged channel as a homodimer file:worm/pgl-3/pgl-3-deep-research-falcon.md a **13-helix fold** forming a homodimer with a central channel (~15 Γ
diameter) and basic electrostatic surface, consistent with RNA binding and/or catalysis |
| GO:0043186 P granule | IDA PMID:18498356 Efficient production of monoclonal antibodies recognizing sp... | ACCEPT | Summary: Correct cellular component annotation - PGL-3 is a constitutive P granule component. Reason: This annotation correctly identifies PGL-3 localization to P granules, which has been extensively demonstrated through multiple experimental approaches. PGL-3 is a core structural component of P granules throughout development. Supporting Evidence: PMID:15238518 PGL-3 is associated with P granules at all stages of development file:worm/pgl-3/pgl-3-deep-research-falcon.md PGL-3 is a constitutive P-granule component βassociated with P granules throughout development.β |
| GO:0003723 RNA binding | ISS PMID:15238518 The PGL family proteins associate with germ granules and fun... | ACCEPT | Summary: RNA binding is a core molecular function of PGL-3, mediated by its C-terminal RGG box, and is experimentally supported (it both recruits mRNA into P granules and drives RNA-dependent phase separation). RNA binding is a distinct molecular function from the guanyl-specific ribonuclease activity (the latter is captured by separate GO:0046589/GO:0004521 annotations), so the previously proposed replacement of this term with ribonuclease T1 activity was removed. Reason: RNA binding via the RGG box is well supported and central to PGL-3's role as an RNA-dependent condensate scaffold and to recruitment of mRNPs into P granules. It should be retained as its own MF rather than collapsed into the RNase term. Supporting Evidence: PMID:27594427 Long messenger RNA molecules bind to PGL-3 protein with low sequence specificity and promote phase separation of PGL-3 drops. file:worm/pgl-3/pgl-3-deep-research-falcon.md containing a C-terminal **RGG box** (an RNA-binding motif) with multiple RGG repeats |
| GO:0005515 protein binding | IPI PMID:15238518 The PGL family proteins associate with germ granules and fun... | MODIFY | Summary: This IPI annotation captures PGL-3 self-association and heterotypic association with PGL-1/PGL-2. The bare 'protein binding' term is uninformative; the biologically meaningful function is that these self-/cross-associations nucleate the P-granule condensate. Falcon and the primary literature establish that PGL-1 and PGL-3 self-associate and nucleate granule formation, so the most informative MF is molecular condensate scaffold activity (GO:0140693) rather than generic protein binding or simple dimerization. Homodimerization per se is already captured by the separate GO:0042802 identical protein binding annotation. Reason: 'protein binding' is on the curation deny-list as uninformative. PGL-3's relevant molecular function here is acting as a scaffold that brings PGL proteins and mRNPs together to organize the P-granule condensate, which is precisely GO:0140693 molecular condensate scaffold activity. Proposed replacements: molecular condensate scaffold activity Supporting Evidence: PMID:15238518 All three PGL proteins interact with each other in vitro PMID:15238518 PGL-1 and PGL-3 are co-immunoprecipitated from embryo extracts, indicating that they are indeed in the same protein complex in vivo file:worm/pgl-3/pgl-3-deep-research-falcon.md Core P-granule components PGL-1 and PGL-3 βself-associate and nucleate granule formation,β positioning PGL-3 as part of the structural scaffold of the P compartment. |
| GO:0043186 P granule | IDA PMID:15238518 The PGL family proteins associate with germ granules and fun... | ACCEPT | Summary: Duplicate P granule annotation with different reference - correct and well-supported. Reason: This annotation correctly identifies PGL-3 localization to P granules with strong experimental evidence from the foundational paper characterizing PGL-3. Duplicates are acceptable when from different sources. Supporting Evidence: PMID:15238518 PGL-3 is associated with P granules at all stages of development, while PGL-2 is associated with P granules only during postembryonic development PMID:15238518 each PGL protein localizes to P granules independently of the other two file:worm/pgl-3/pgl-3-deep-research-falcon.md P granules are typically **perinuclear** for much of germline development and associate with nuclear pores |
| GO:1903863 P granule assembly | IDA PMID:21402787 PGL proteins self associate and bind RNPs to mediate germ gr... | NEW | Summary: Critical biological process - PGL-3 is essential for P granule assembly through its dimerization domain. Reason: This important biological process annotation is missing from the current set. PGL-3 is a core structural scaffold protein that assembles P granules through its dimerization domain, forming fundamental building blocks for granule assembly. Supporting Evidence: PMID:21402787 PGL proteins self associate and bind RNPs to mediate germ granule assembly in C. elegans PMID:26787882 we now suggest that the P-granule framework is constructed from multimers of PGL dimers file:worm/pgl-3/pgl-3-deep-research-falcon.md PGL-1 and PGL-3 βself-associate and nucleate granule formation,β |
| GO:0007281 germ cell development | IGI PMID:15238518 The PGL family proteins associate with germ granules and fun... | NEW | Summary: Core biological process - PGL-3 functions redundantly with PGL-1 in germline development. Reason: This fundamental biological process is missing. PGL-3 and PGL-1 function redundantly in germline development, with double mutants showing severe sterility and germline defects. Supporting Evidence: PMID:15238518 pgl-1; pgl-3 (but not pgl-2; pgl-1) double-mutant hermaphrodites and males show significantly enhanced sterility at all temperatures file:worm/pgl-3/pgl-3-deep-research-falcon.md PGL-3 functions redundantly with PGL-1 to support germline development. pgl-3 single mutants show little overt germline defect in the cited work, but **pgl-1; pgl-3** double mutants show markedly enhanced sterility and germline defects |
| GO:0043066 negative regulation of apoptotic process | IGI PMID:26598553 Loss of PGL-1 and PGL-3, members of a family of constitutive... | NEW | Summary: Important protective function - PGL-3 with PGL-1 protects germ cells from excessive apoptosis. Reason: This protective function is not annotated but is experimentally demonstrated. PGL-3 and PGL-1 together protect germ cells from excessive apoptosis during normal development and after DNA damage. Supporting Evidence: PMID:26598553 Loss of PGL-1 and PGL-3, members of a family of constitutive germ-granule components, promotes germline apoptosis in C. elegans |
| GO:0016070 RNA metabolic process | TAS PMID:26787882 PGL germ granule assembly protein is a base-specific, single... | NEW | Summary: PGL-3 directly contributes to RNA metabolism through its ribonuclease activity Reason: This is a core process that PGL-3 participates in through its enzymatic activity on RNA substrates within P granules Supporting Evidence: PMID:26787882 PGL germ granule assembly protein is a base-specific, single-stranded RNase |
| GO:0010608 post-transcriptional regulation of gene expression | TAS PMID:21402787 PGL proteins self associate and bind RNPs to mediate germ gr... | NEW | Summary: PGL-3 participates in post-transcriptional regulation through P granule-mediated RNA processing Reason: This is a fundamental process that PGL-3 mediates through its role in P granules which regulate RNA stability and translation Supporting Evidence: PMID:21402787 the common biochemical function of germ granules is to regulate the translation efficiency and/or stability of mRNAs in the germline |
| GO:0046983 protein dimerization activity | IDA PMID:21402787 PGL proteins self associate and bind RNPs to mediate germ gr... | NEW | Summary: PGL-3 self-associates via a structured self-interaction domain (residues 160-319), which is necessary and sufficient for it to form globular granules and to be recruited into PGL-3 granules. This self-association activity is the molecular building block from which the P-granule scaffold is constructed (multimers of PGL dimers) and is distinct from the bare 'protein binding' terms. The structural basis is the PGL dimerization domain, which adopts a 13-helix fold creating a positively charged channel as a homodimer (PMID:26787882). Reason: Protein dimerization is a well-supported molecular function: PMID:21402787 (Hanazawa et al. 2011) directly assayed PGL-3 self-interaction in mammalian cells, mapping residues 160-319 as essential for self-interaction, while PMID:26787882 provides the structural basis (PGL DD homodimer). This activity underpins both the condensate scaffold activity and the RNase channel, so it is captured here as an explicit MF anchored to the primary PGL-3 self-association assay. Supporting Evidence: PMID:21402787 it is likely that residues 160β319 of PGL-3 comprise a region essential for self-interaction of PGL proteins PMID:21402787 PGL-3 has two distinct domains for self-interaction and recruitment of RNA and RNA-binding proteins PMID:26787882 PGL-1 DD has a novel 13 Ξ±-helix fold that creates a positively charged channel as a homodimer file:worm/pgl-3/pgl-3-deep-research-falcon.md a **13-helix fold** forming a homodimer with a central channel (~15 Γ
diameter) and basic electrostatic surface, consistent with RNA binding and/or catalysis |
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Download this section (compressed HTML)Q: How does PGL-3's ribonuclease activity compare to PGL-1 in terms of substrate specificity and enzymatic efficiency?
Suggested experts: RNA biochemists, Enzyme kinetics specialists, RNP granule researchers
Q: What determines PGL-3's constitutive presence in P granules throughout development versus PGL-2's temporal restriction to postembryonic stages?
Suggested experts: Developmental biologists, Gene regulation experts, C. elegans specialists
Q: How does PGL-3's interaction with autophagy machinery through SEPA-1 regulate P granule homeostasis during development?
Suggested experts: Autophagy researchers, Cellular quality control specialists, Developmental biology experts
Q: What is the molecular basis for functional redundancy between PGL-1 and PGL-3 and why is PGL-2 unable to compensate in double mutants?
Suggested experts: Protein structure-function specialists, C. elegans geneticists, Molecular evolution researchers
Experiment: Side-by-side enzymatic assays of purified PGL-1 and PGL-3 to compare ribonuclease activity, substrate specificity, and kinetic parameters
Hypothesis: PGL-1 and PGL-3 have similar but not identical enzymatic properties that explain their functional redundancy
Type: Comparative biochemical analysis
Experiment: Express PGL-3 under PGL-2 temporal control and vice versa to test if temporal expression patterns determine functional specialization
Hypothesis: Temporal expression differences rather than protein function differences explain PGL-2/PGL-3 specialization
Type: Temporal expression rescue experiments
Experiment: Time-course analysis of PGL-3-SEPA-1 interactions and P granule clearance during different developmental stages and stress conditions
Hypothesis: Autophagy regulates P granule composition dynamically based on developmental needs and cellular stress
Type: Autophagy-P granule interaction mapping
Experiment: Create PGL-1/PGL-3 domain swaps to identify regions responsible for functional redundancy and test rescue ability in double mutants
Hypothesis: Specific domains determine functional equivalence while others confer protein-specific properties
Type: Domain swap complementation analysis
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