GLH-4 (Germline Helicase 4) is a Vasa/DDX4-class ATP-dependent DEAD-box RNA helicase that localizes to perinuclear P granules in the C. elegans germline. It functions redundantly with GLH-1 to organize P granule architecture and maintain piRNA pathway fidelity. GLH-4 contains a conserved DEAD-box helicase domain, five CCHC-type zinc fingers, and N-terminal glycine-rich FG/FGG repeats that promote perinuclear localization by interacting with nuclear pore-like FG hydrogels. The protein acts as a scaffold that recruits Argonaute proteins (PRG-1, WAGO-4) and coordinates 22G-RNA amplification at piRNA targets. While single glh-4 mutants show minimal phenotypes, glh-1;glh-4 double mutants exhibit severe germline defects including sterility, under-proliferated germlines lacking oocytes, and dispersed P granule components, demonstrating the critical redundant role of these helicases in germline development and fertility.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0030490 maturation of SSU-rRNA | IBA GO_REF:0000033 | REMOVE | Summary: IBA annotation based on phylogenetic inference from PANTHER. While GLH-4 belongs to the DEAD-box helicase family (DDX4/VASA subfamily), there is no direct evidence that GLH-4 participates in SSU-rRNA maturation. The primary literature consistently describes GLH-4's role in P granule organization and piRNA pathway function rather than ribosome biogenesis (PMID:10851135, Chen et al. 2022). This may be an over-extension from more distant DEAD-box helicase family members. Reason: GLH-4 is a germline-specific P granule component with established functions in germline development and piRNA pathway fidelity. There is no literature evidence supporting a role in SSU-rRNA maturation. The IBA inference likely derives from distant DEAD-box helicase family members with different cellular functions. Supporting Evidence: file:worm/glh-4/glh-4-deep-research-falcon.md GLH-4 is a core organizer of germ granules, acting redundantly with GLH-1 to scaffold liquid condensates that concentrate Argonautes and target RNAs, thereby promoting fidelity of piRNA-guided transcriptome surveillance |
| GO:0000166 nucleotide binding | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation from UniProtKB keyword mapping. GLH-4 contains a conserved DEAD-box helicase ATP-binding domain (IPR014001) with Walker A and B motifs essential for ATP binding and hydrolysis. Reason: Nucleotide binding is a fundamental property of DEAD-box RNA helicases. GLH-4 has conserved ATP-binding domains and the DEAD-box motif (positions 897-900). This general annotation is correct but subsumed by more specific ATP binding and RNA helicase activity terms. Supporting Evidence: PMID:10851135 GLHs are homologous to Drosophila VASA |
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro domain mapping (IPR001878 CCHC zinc finger, IPR011545 DEAD/DEAH helicase domain). GLH-4 contains five CCHC-type zinc fingers that can bind nucleic acids, and the DEAD-box helicase domain engages RNA. Reason: GLH-4 has structural features for nucleic acid binding including CCHC zinc fingers and DEAD-box helicase domains. The term is accurate but general; more specific terms like RNA binding are also present. Supporting Evidence: PMID:10851135 the GLHs are distinguished by containing multiple CCHC zinc fingers |
| GO:0003723 RNA binding | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation from UniProtKB keyword mapping. DEAD-box helicases are ATP-dependent RNA-binding proteins. GLH-4 is classified as an RNA helicase (EC 3.6.4.13) that binds and remodels RNA within P granules, functioning as an "RNA solvent" to ensure mRNA accessibility for small-RNA surveillance. Reason: RNA binding is a core molecular function of DEAD-box RNA helicases. GLH-4 belongs to the DDX4/VASA subfamily and functions in RNP remodeling within P granules. Supporting Evidence: file:worm/glh-4/glh-4-deep-research-falcon.md DEAD-box helicases that bind and remodel RNA or RNPs; ATP hydrolysis drives cycles of RNA engagement/release |
| GO:0003724 RNA helicase activity | IEA GO_REF:0000003 | ACCEPT | Summary: IEA annotation from EC number mapping (EC 3.6.4.13). GLH-4 is designated as an ATP-dependent RNA helicase with the conserved DEAD-box motif and helicase ATP-binding/C-terminal domains characteristic of active helicases. Reason: RNA helicase activity is the primary molecular function of GLH-4. The protein has all conserved motifs (Q motif, DEAD box, helicase domains) required for ATP-dependent RNA unwinding activity. This annotation represents a core function. Supporting Evidence: PMID:10851135 four putative germline RNA helicases, GLHs, are components of the germline-specific P granules |
| GO:0004386 helicase activity | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation from UniProtKB keyword mapping (helicase). GLH-4 contains conserved helicase ATP-binding (IPR014001) and C-terminal helicase (IPR001650) domains, as well as the DEAD-box motif signature. Reason: Helicase activity is correct but general. The more specific term "RNA helicase activity" (GO:0003724) is also annotated and better captures the function. Supporting Evidence: PMID:10851135 four putative germline RNA helicases, GLHs |
| GO:0005524 ATP binding | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation from combined automated methods using InterPro and UniProtKB keywords. GLH-4 has a conserved ATP-binding site (residues 780-787) within the helicase ATP-binding domain. ATP hydrolysis by GLH helicases regulates P granule dynamics and is essential for germline maintenance. Reason: ATP binding is a core property of DEAD-box helicases and essential for GLH-4 function. Studies on GLH-1 ATPase mutants demonstrate the importance of ATP hydrolysis cycling for P granule assembly and Argonaute recruitment. Supporting Evidence: file:worm/glh-4/glh-4-deep-research-falcon.md ATP-dependent RNA helicases that bind and remodel RNA or RNPs; ATP hydrolysis drives cycles of RNA engagement/release important for condensate dynamics |
| GO:0008270 zinc ion binding | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation from InterPro domain mapping. GLH-4 contains five CCHC-type zinc finger domains that coordinate zinc ions. These zinc fingers distinguish GLH proteins from Drosophila VASA (PMID:10851135). Reason: The five CCHC zinc fingers in GLH-4 require zinc ion binding for structural integrity. This is a distinguishing feature of C. elegans GLH proteins. Supporting Evidence: PMID:10851135 the GLHs are distinguished by containing multiple CCHC zinc fingers |
| GO:0008432 JUN kinase binding | IEA GO_REF:0000117 | ACCEPT | Summary: IEA annotation from ARBA machine learning model. This annotation is supported by the IPI annotation from PMID:12435362 which demonstrated GLH-KGB-1 interaction by yeast two-hybrid and GST pull-down assays. Reason: This annotation is redundant with the IPI annotation from PMID:12435362 that provides direct experimental evidence for GLH-KGB-1 binding. The ARBA annotation correctly captures this interaction. |
| GO:0016787 hydrolase activity | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation from UniProtKB keyword mapping. GLH-4 is an ATP-dependent RNA helicase (EC 3.6.4.13) that catalyzes ATP hydrolysis coupled to RNA unwinding. Reason: Hydrolase activity is correct but very general. The more specific term "ATP hydrolysis activity" (GO:0016887) better describes the reaction catalyzed by GLH-4. Supporting Evidence: UniProt:O76743 Reaction=ATP + H2O = ADP + phosphate + H(+); Xref=Rhea:RHEA:13065 |
| GO:0016887 ATP hydrolysis activity | IEA GO_REF:0000116 | ACCEPT | Summary: IEA annotation from Rhea reaction mapping. GLH-4 catalyzes ATP hydrolysis (RHEA:13065) coupled to RNA helicase activity. Studies on GLH-1 demonstrate that the ATPase cycle is essential for P granule dynamics and PRG-1 recruitment. Reason: ATP hydrolysis activity is a core catalytic function of DEAD-box helicases. The ATPase cycle controls P granule liquid droplet dynamics and is essential for germline function. Supporting Evidence: file:worm/glh-4/glh-4-deep-research-falcon.md ATP hydrolysis drives cycles of RNA engagement/release important for condensate dynamics and RNA surveillance functions in P granules |
| GO:0043186 P granule | IEA GO_REF:0000117 | ACCEPT | Summary: IEA annotation from ARBA machine learning model. This is well-supported by the IDA annotation from PMID:10851135 which directly demonstrated GLH-4 localization to P granules by immunofluorescence. Reason: P granule localization is a defining feature of GLH-4 function. This IEA annotation is redundant with the IDA experimental evidence but correctly captures the localization. |
| GO:0046872 metal ion binding | IEA GO_REF:0000043 | ACCEPT | Summary: IEA annotation from UniProtKB keyword mapping. GLH-4 binds zinc ions through its five CCHC-type zinc finger domains. Reason: Metal ion binding is correct but general. The more specific term "zinc ion binding" (GO:0008270) is also annotated and provides better precision. Supporting Evidence: UniProt:O76743 Belongs to the DEAD box helicase family. DDX4/VASA subfamily |
| GO:0008432 JUN kinase binding | IPI PMID:12435362 The GLH proteins, Caenorhabditis elegans P granule component... | ACCEPT | Summary: IPI annotation from yeast two-hybrid and GST pull-down experiments demonstrating physical interaction between GLH proteins (including GLH-4) and KGB-1, a C. elegans JNK MAP kinase. The GLH-KGB-1 interaction was mapped to the C-terminal region of GLH proteins (PMID:12435362). Reason: This is experimentally validated by yeast two-hybrid screening and GST pull-down assays. KGB-1 is a fertility factor whose loss phenocopies glh-1/glh-4 double mutant sterility. The interaction appears functionally relevant to germline development. Supporting Evidence: PMID:12435362 KGB-1 is a putative JNK MAP kinase that GLHs bind PMID:12435362 GST pull-down assays independently established that these proteins bind GLHs |
| GO:0003724 RNA helicase activity | ISS PMID:10851135 Combinatorial RNA interference indicates GLH-4 can compensat... | ACCEPT | Summary: ISS annotation based on sequence similarity to VASA/DDX4 DEAD-box RNA helicases. GLH-4 has conserved DEAD-box helicase domains and belongs to the DDX4/VASA subfamily. Direct RNA helicase activity has been inferred from the paralog GLH-1 where ATPase mutants perturb P granule dynamics. Reason: RNA helicase activity is strongly supported by domain architecture and family membership. GLH-4 has the complete complement of DEAD-box helicase motifs and functional studies on GLH-1 support ATPase-dependent RNA remodeling activity. Supporting Evidence: PMID:10851135 four putative germline RNA helicases, GLHs, are components of the germline-specific P granules in Caenorhabditis elegans file:worm/glh-4/glh-4-deep-research-falcon.md As a DEAD-box helicase, GLH proteins are ATP-dependent RNA helicases that bind and remodel RNA or RNPs |
| GO:0005737 cytoplasm | IDA PMID:10851135 Combinatorial RNA interference indicates GLH-4 can compensat... | ACCEPT | Summary: IDA annotation from immunolocalization studies. GLH-4 localizes to P granules, which are cytoplasmic non-membranous RNP condensates adjacent to nuclear pores in germline cells. While cytoplasm is technically correct, the more specific P granule localization better describes GLH-4's subcellular distribution. Reason: P granules are located in the cytoplasm, so this annotation is correct. However, the P granule annotation (GO:0043186) provides more specific localization information. GLH-4 is specifically perinuclear within P granules. Supporting Evidence: PMID:10851135 four putative germline RNA helicases, GLHs, are components of the germline-specific P granules in Caenorhabditis elegans |
| GO:0007276 gamete generation | IMP PMID:10851135 Combinatorial RNA interference indicates GLH-4 can compensat... | ACCEPT | Summary: IMP annotation based on RNAi knockdown experiments. Single glh-4(RNAi) has no effect at 20C, but glh-1/glh-4 double RNAi results in 97% sterility with under-proliferated germlines lacking oocytes. Sperm are produced but are delayed and defective (PMID:10851135). Reason: This is a core biological function of GLH-4, acting redundantly with GLH-1. The genetic evidence clearly demonstrates essential roles in gametogenesis. The annotation is well-supported by multiple publications. Supporting Evidence: PMID:10851135 loss of both GLH-1 and GLH-4 results in 97% sterility file:worm/glh-4/glh-4-deep-research-falcon.md maternal-zygotic glh-4 glh-1 double mutants lacked germ cells in 63% of animals |
| GO:0042127 regulation of cell population proliferation | IMP PMID:10851135 Combinatorial RNA interference indicates GLH-4 can compensat... | MODIFY | Summary: IMP annotation based on germline proliferation defects in glh-1/glh-4 double RNAi animals. The germlines are under-proliferated, indicating a role in regulating germ cell division (PMID:10851135). Reason: While GLH-4 affects germline proliferation, a more specific term would better capture this function. The phenotype is specifically germ cell proliferation defects, not general cell proliferation regulation. Consider GO:0036093 (germ cell proliferation) for more precision. Proposed replacements: germ cell proliferation Supporting Evidence: PMID:10851135 glh-1/4(RNAi) germlines are under-proliferated and are without oocytes |
| GO:0043186 P granule | IDA PMID:10851135 Combinatorial RNA interference indicates GLH-4 can compensat... | ACCEPT | Summary: IDA annotation from immunofluorescence localization. GLH-4 was directly observed to localize to P granules, which are germline-specific non-membranous RNP condensates at the nuclear periphery. This is a defining feature of GLH proteins (PMID:10851135). Reason: P granule localization is a core feature of GLH-4 function, supported by direct experimental evidence. P granules are the site where GLH-4 acts to organize piRNA pathway components and maintain germline integrity. Supporting Evidence: PMID:10851135 four putative germline RNA helicases, GLHs, are components of the germline-specific P granules in Caenorhabditis elegans file:worm/glh-4/glh-4-deep-research-falcon.md GLH proteins localize to C. elegans germ granules (P granules), which are phase-separated RNP condensates at the nuclear periphery of germ cells |
| GO:1903863 P granule assembly | IMP PMID:21402787 PGL proteins self associate and bind RNPs to mediate germ gr... | NEW | Summary: GLH-4 acts redundantly with GLH-1 to regulate P granule formation and granular structure in embryos. Combined knockdown results in smaller P granules and dispersal of PGL-1/PGL-3 scaffolds (PMID:21402787, Spike et al. 2008). The FG/FGG repeats promote perinuclear localization essential for P granule organization. Reason: P granule assembly is a major biological function of GLH-4 supported by multiple publications. This process-level annotation captures GLH-4's role in organizing germ granule structure. Supporting Evidence: UniProt:O76743 May act redundantly with the P-granule component glh-1 to regulate the formation of the granular structure of P-granules in embryos file:worm/glh-4/glh-4-deep-research-falcon.md P-granule markers (PGL-1/3) became completely dispersed in the cytoplasm |
| GO:0048477 oogenesis | IMP PMID:10851135 Combinatorial RNA interference indicates GLH-4 can compensat... | NEW | Summary: GLH-4 is critical for oogenesis, acting redundantly with GLH-1. Double RNAi animals lack oocytes entirely while producing (defective) sperm, indicating specific requirements in female gamete formation (PMID:10851135, PMID:12435362). Reason: Oogenesis defects are a prominent phenotype of glh-1/glh-4 double mutants. This provides more specificity than the general "gamete generation" term. Supporting Evidence: PMID:10851135 glh-1/4(RNAi) germlines are under-proliferated and are without oocytes PMID:12435362 loss of either CSN-5 or KGB-1 causes oogenesis to cease |
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Download this section (compressed HTML)Q: Does GLH-4 have direct RNA helicase activity in vitro, and what are its substrate preferences? While GLH-4 is classified as an RNA helicase based on domain architecture and family membership, direct biochemical demonstration of its helicase activity has not been reported.
Q: What is the specific division of labor between GLH-1 and GLH-4 in P granule function? While these proteins function redundantly, subtle differences in their expression patterns, protein interactions, or substrate preferences may exist.
Q: How does GLH-4 contribute to piRNA target discrimination and self/non-self recognition? Chen et al. 2022 showed GLH-1/GLH-4 are required for piRNA pathway fidelity, but the molecular mechanism is not fully understood.
Experiment: In vitro RNA helicase assay with purified GLH-4 protein. Direct biochemical demonstration of RNA helicase activity would confirm the ISS/IEA annotations and characterize substrate specificity. GLH-4 should show ATP-dependent RNA unwinding activity typical of DEAD-box helicases.
Experiment: IP-MS of GLH-4 protein complexes in wild-type and ATPase-mutant backgrounds. Similar experiments on GLH-1 identified Argonaute and P granule scaffold interactions. GLH-4-specific interactors could reveal unique functions and should include PRG-1, WAGO proteins, and DEPS-1.
Experiment: smFISH analysis of piRNA target mRNA localization in glh-4 single mutants. Most studies use double mutants. Single mutant analysis could reveal GLH-4-specific contributions to mRNA surveillance that are masked by GLH-1 redundancy.
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