Glorund (Glo, CG6946) is a Drosophila RNA-binding protein of the hnRNP F/H-like group within the ESRP/hnRNP H/F family (PANTHER PTHR13976). The long product (Q9VGH5, 586 residues) has three quasi-RNA-recognition motifs (qRRMs) separated by a glycine/asparagine-rich region. Each qRRM binds single-stranded G-tract RNA, and each also has a basic RNP2 surface that recognizes a double-stranded UA-rich motif. In late oogenesis Glo binds the translational control element (TCE) in the nanos 3' UTR, using both binding modes and at least two qRRMs. It represses translation of the unlocalized nanos mRNA at initiation and after initiation, the latter in part by recruiting dFMRP through qRRM2. This restricts Nanos protein to the posterior pole. Glo is found in the nucleus and cytoplasm of nurse cells, the oocyte and follicle cells. It binds the hnRNP Hrp48 and the splicing factor Half-pint, and probably regulates alternative splicing of ovarian tumor. Through this activity, which needs only the G-tract binding mode, it is required for nurse-cell chromosome dispersion, gurken mRNA localization and dorsal-ventral patterning. Knockdown studies also implicate glo in lipid storage and in expression of lipoprotein genes in the fat body and intestine. Q8INJ6 is isoform C, a 179-residue product: residues 1-168 match the long product, followed by an 11-residue unique tail. It has a complete qRRM1, only the first 27 residues of qRRM2, no qRRM3 and no glycine-rich region. A Glo protein with a single intact qRRM does not bind or repress nanos in vivo, so isoform C alone is not expected to carry out nanos repression. Its own expression and activity have not been tested.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003676 nucleic acid binding | IEA GO_REF:0000002 | MODIFY | Summary: InterPro-derived nucleic acid binding. It is correct but less specific than the RNA binding that has been shown directly for Glo qRRMs. Reason: The RBD superfamily match (IPR035979) is correct. Glorund qRRMs, including qRRM1 (residues 45-141), which is complete in this isoform, bind single-stranded G-tract RNA in EMSA. The nucleic-acid ligand is RNA, so the term should be refined to RNA binding (GO:0003723), which the gene already carries. Proposed replacements: RNA binding Supporting Evidence: file:DROME/glo/glo-uniprot.txt DR InterPro; IPR035979; RBD_domain_sf. PMID:28380354 Each qRRM domain bound independently to G-tract RNA (Figure 2), and qRRM1 and qRRM3 exhibited several-fold higher affinity than qRRM2 |
| GO:0003723 RNA binding | IEA GO_REF:0000120 | ACCEPT | Summary: RNA binding is supported by the RRM signature and by direct binding assays on Glo qRRMs, including qRRM1, which is the one complete qRRM in isoform C. Reason: The RRM domain (PS50102, residues 49-129) lies within qRRM1. Purified Glo qRRM1 alone binds G-tract RNA with a Kd of about 0.18 uM (PMID:28380354), so RNA binding is supported even for the short isoform-C product. At the gene level, Glo binds the nanos TCE (PMID:16516833, PMID:28380354, PMID:37427795). The canonical long product also carries an IBA for this term from PANTHER node PTN000360053, the hnRNP F/H-ESRP-fusilli clade, so the activity is also supported phylogenetically. Supporting Evidence: file:DROME/glo/glo-uniprot.txt DR InterPro; IPR000504; RRM_dom. PMID:28380354 We conclude that, like hnRNP F qRRMs, Glo qRRMs are each capable of interacting with G-tract RNA. PMID:16516833 Here we identify a Drosophila hnRNP, Glorund, that interacts specifically with stem-loop III. |
| GO:0003729 mRNA binding | ISS PMID:10908586 The drosophila melanogaster genome: translation factors and ... | ACCEPT | Summary: Glo is a direct mRNA-binding protein. It binds the nanos 3' UTR TCE in vitro and in vivo. The cited genome survey does not discuss Glo, but direct evidence supports the claim. Reason: The ISS rests on a genome-wide survey of RNA-binding proteins (PMID:10908586) that does not name Glorund. Later direct experiments confirm the claim. Recombinant Glo binds nanos TCE RNA, and binding correlates with repression in vivo (PMID:16516833). Tandem qRRM1,2 binds the TCE with two affinity components (PMID:28380354). GFP-Glo co-immunoprecipitates nanos mRNA in vivo when at least two qRRMs are intact (PMID:37427795). This is a gene-level claim. A product with a single intact qRRM, like isoform C, did not co-immunoprecipitate nanos, so this row should not be read as an isoform-C-specific measurement. More specific mRNA 3'-UTR binding is proposed as NEW. Supporting Evidence: PMID:16516833 We establish that the ability of the TCE to repress translation in vivo reflects its ability to bind Glorund in vitro. PMID:37427795 GFP-Glo mutants with any two qRRMs intact retained the ability to interact with nos mRNA in vivo |
| GO:0005515 protein binding | IPI PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | REMOVE | Summary: The Glo-Hrp48 interaction is real (RNase-resistant co-IP and in vitro binding), but generic protein binding is uninformative. Reason: Under the repository's GO:0005515 policy, bare protein binding is removed as uninformative. This does not deny the interaction. Kalifa et al. 2009 show that Glo associates with Hrp48 (Hrb27C, FBgn0004838) in an RNA-independent way and binds it in vitro. The paper does not establish a more specific molecular function, such as adaptor or splicing-factor activity, for that interaction. The biology is kept in the protein-containing complex rows and the core function narrative. Supporting Evidence: PMID:19013444 Here we show that Glorund is part of a complex containing the hnRNP protein Hrp48 and the splicing factor Half-pint |
| GO:0005515 protein binding | IPI PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | REMOVE | Summary: The Glo-Half-pint interaction is real and RNase-resistant, but generic protein binding is uninformative. Reason: Under the GO:0005515 policy this generic term is removed. The interaction with Half-pint (Hfp, FBgn0028577) is not in doubt. Native Glo and Hfp co-immunoprecipitate after RNase treatment, and they bind in vitro (PMID:19013444). No more informative molecular function is established for it. Supporting Evidence: PMID:19013444 We confirmed directly that native Glo and Hfp can be co-immunoprecipitated from ovary extract, using antibodies to either protein, but not using a control anti-Sxl antibody |
| GO:0006417 regulation of translation | IMP PMID:16516833 Glorund, a Drosophila hnRNP F/H homolog, is an ovarian repre... | MODIFY | Summary: Glo is a translational repressor of unlocalized nanos mRNA in late oogenesis. The direction of regulation is known, so negative regulation of translation is the more precise term. Reason: Loss of glo derepresses nanos translation in late oocytes (PMID:16516833, PMID:28380354). Glo blocks translation initiation and also imposes a post-initiation block (PMID:21460235). The post-initiation block involves recruiting dFMRP to inhibit elongation (PMID:35699205). The direction is unambiguously negative, so the term should be refined to negative regulation of translation (GO:0017148). Glo does this work itself, because its qRRMs bind the TCE. This applies to the gene's long product. Isoform C, with one complete qRRM, is not expected to repress nanos alone (PMID:37427795). Proposed replacements: negative regulation of translation Supporting Evidence: PMID:16516833 reveal a specific role for an hnRNP in repression of nanos translation during oogenesis PMID:21460235 Furthermore, we show that, during late oogenesis, nos translation is also repressed post-initiation and provide evidence that Glo mediates this event. PMID:35699205 Our findings suggest that Glo regulates nos translation elongation by recruiting dFMRP |
| GO:0007311 maternal specification of dorsal/ventral axis, oocyte, germ-line encoded | IMP PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | KEEP AS NON CORE | Summary: Germline glo clones give dorsal-ventral polarity defects through gurken mislocalization. This is a genuine germline requirement, but it is downstream of Glo's RNA-processing role, probably otu splicing. Reason: Germline clones of glo162x produce dorsal-ventral polarity defects and mislocalized gurken (PMID:19013444). Rescue by an Otu-104 transgene places Glo upstream of otu isoform production. Tamayo et al. (PMID:28380354) showed that gurken regulation needs only the G-tract binding mode of Glo. The germline-encoded maternal specification term is an appropriate developmental annotation, but it is not the core activity of the protein, which is RNA binding and post-transcriptional regulation. Supporting Evidence: PMID:19013444 glo appears to be required for proper localization of grk mRNA to the dorsal-anterior region of the oocyte PMID:28380354 regulation of Glo target RNAs required for chromosome organization and grk regulation specifically require the G-tract RNA binding mode |
| GO:0032991 protein-containing complex | IPI PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | KEEP AS NON CORE | Summary: Glo is in a complex with Hrp48 and Half-pint. This generic term is as precise as the evidence allows, but it is not core. Reason: The Glo-Hrp48-Hfp association is RNase-resistant and direct in vitro (PMID:19013444). The authors propose that it is a nuclear splicing complex but did not show this. Because the interaction is RNA-independent, ribonucleoprotein complex is not demonstrated either. No more specific GO complex term is supported, so the generic term is retained as non-core. Supporting Evidence: PMID:19013444 We propose that Glo and Hrp48 participate together in a nuclear splicing complex |
| GO:0032991 protein-containing complex | IPI PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | KEEP AS NON CORE | Summary: The same Glo-Hrp48-Half-pint complex, recorded with Half-pint as the partner. Kept as non-core. Reason: Consistent with the Hrp48 row. Native Glo and Hfp co-immunoprecipitate after RNase treatment (PMID:19013444). The complex is real, but a more specific complex term is not supported. Supporting Evidence: PMID:19013444 We confirmed directly that native Glo and Hfp can be co-immunoprecipitated from ovary extract, using antibodies to either protein, but not using a control anti-Sxl antibody |
| GO:0042060 wound healing | HMP PMID:19884309 Genetic screen in Drosophila melanogaster uncovers a novel s... | UNDECIDED | Summary: The annotation comes from a large insertional-mutagenesis screen for embryonic epithelial repair. Glo is not discussed in the accessible abstract, and the full text could not be retrieved. Reason: The cached record of PMID:19884309 is abstract-only, and Europe PMC returned no full text. The abstract reports 30 lethal insertional mutants and names karst, but not glo, so the specific glo allele and phenotype cannot be checked. glo mutants have broad lethality and pleiotropic phenotypes. A defect in a lethal-insertion screen may therefore be indirect, and the RNA-binding activity of Glo suggests no direct mechanism in purse-string wound closure. Without the full text, the curator's call cannot be judged. Supporting Evidence: PMID:19884309 performed a forward genetics screen on the basis of insertional mutagenesis by transposons that led to the identification of 30 lethal insertional mutants with defects in embryonic epithelia repair |
| GO:0045451 germ plasm oskar mRNA localization | IMP PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | KEEP AS NON CORE | Summary: A minority of glo mutant oocytes or embryos mislocalize oskar mRNA. Glo has not been shown to bind oskar mRNA, so the role is low-penetrance and probably indirect. Reason: Kalifa et al. report oskar localization defects in a small proportion of glo mutants (PMID:19013444). The defect is consistent with Glo's place in the Hrp48/Otu RNP network. Glo is not required for oskar first-intron splicing, and direct oskar binding was not shown. The phenotype is real, so the curated experimental annotation is kept, but it is peripheral to Glo's core RNA-binding regulatory role. Supporting Evidence: PMID:19013444 a small proportion of glo mutant embryos show osk mRNA localization defects PMID:19013444 indicating that glo is not required for osk first intron splicing |
| GO:0051276 chromosome organization | IMP PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | MARK AS OVER ANNOTATED | Summary: glo mutant nurse-cell chromosomes fail to disperse from the polytene state. The defect is partly rescued by Otu-104, so Glo acts upstream by regulating RNA, not as a chromatin-organizing factor. Reason: The phenotype is robust and is rescued by a genomic glo transgene (PMID:19013444). Glo supplies none of the structural or catalytic work of chromosome organization. The defect is partially suppressed by expressing the otu isoform Otu-104, which places Glo upstream through regulation of otu RNA processing. PMID:28380354 shows that this function needs only Glo's G-tract RNA-binding mode. Annotating the protein as directly involved in chromosome organization overstates a downstream consequence of its RNA-regulatory activity. The phenotype itself is not disputed. Supporting Evidence: PMID:19013444 In nurse cells from glo162x ovaries, chromosomes fail to disperse during mid-oogenesis and maintain a polytene morphology PMID:19013444 probably by regulating alternative splicing of ovarian tumor |
| GO:0060810 intracellular mRNA localization involved in pattern specification process | IMP PMID:19013444 Glorund interactions in the regulation of gurken and oskar m... | KEEP AS NON CORE | Summary: glo is needed for correct gurken (and less often oskar) mRNA localization in the oocyte. The requirement is genuine, but Glo has not been shown to bind these mRNAs. Reason: In glo germline clones, gurken mRNA spreads along the anterior cortex instead of staying in the dorsal-anterior corner (PMID:19013444). The requirement depends on Glo's G-tract binding mode (PMID:28380354) and is probably mediated by otu splicing. The process term is an accepted developmental annotation for the gene but is not core. Supporting Evidence: PMID:19013444 glo appears to be required for proper localization of grk mRNA to the dorsal-anterior region of the oocyte |
| GO:0003730 mRNA 3'-UTR binding | IDA PMID:28380354 The Drosophila hnRNP F/H Homolog Glorund Uses Two Distinct R... | NEW | Summary: Glo binds the translational control element in the nanos 3' UTR directly in vitro, and binds nanos mRNA in vivo. Reason: The direct ligand of Glo's best-characterized activity is a defined 3'-UTR element. Kalifa et al. identified Glo by its specific binding to TCE stem-loop III (PMID:16516833). Tamayo et al. showed by EMSA that Glo qRRM1,2 binds the TCE through the TCEI G-tract and the TCEIII UA-rich stem, and that both are needed in vivo (PMID:28380354). Warden et al. confirmed in vivo association with nanos mRNA (PMID:37427795). This term is more specific than the existing mRNA binding term. It describes the long product, because isoform C, with one complete qRRM, is not expected to bind the TCE stably. Supporting Evidence: PMID:28380354 Glo qRRM1,2 did bind stably to the TCE, with two plateaus apparent in the binding curve PMID:16516833 Here we identify a Drosophila hnRNP, Glorund, that interacts specifically with stem-loop III. |
| GO:0000900 mRNA regulatory element binding translation repressor activity | IMP PMID:28380354 The Drosophila hnRNP F/H Homolog Glorund Uses Two Distinct R... | NEW | Summary: Glo represses nanos translation by binding the TCE in its 3' UTR. Mutations that remove either RNA-binding mode abolish repression in vivo, which matches this molecular function. Reason: GO:0000900 combines sequence-element binding with translational repression. Glo binds the nanos TCE (PMID:16516833, PMID:28380354). Triple point mutants that remove either binding mode (GloWYY, GloRKH) fail to repress nanos even though they are expressed at normal levels (PMID:28380354). Mutating both Glo recognition motifs in the TCE disrupts repression (PMID:28380354). Repression needs at least two intact qRRMs (PMID:37427795). Glo is therefore the factor that binds the element and causes repression, not merely a requirement for it. This is the core activity of the full-length gene product, not of the one-qRRM isoform C. Supporting Evidence: PMID:28380354 both modes of RNA recognition are required for translational repression of nos during oogenesis PMID:37427795 at least two qRRMs are required for TCE recognition and translational repression of nos in vivo |
| GO:0005634 nucleus | IDA PMID:16516833 Glorund, a Drosophila hnRNP F/H homolog, is an ovarian repre... | NEW | Summary: Glo is detected in the nuclei and cytoplasm of nurse cells, the oocyte and follicle cells. Reason: The 2009 study, citing antibody staining by Kalifa et al. 2006, states that Glo is nuclear and cytoplasmic and proposes a nuclear Glo-Hrp48-Hfp splicing complex (PMID:19013444). The nuclear pool matches its proposed role in otu splicing and its requirement for nurse-cell chromosome dispersion. The canonical long product carries an IBA for nucleoplasm from the hnRNP F/H clade node PTN000360053. This localization is established for the gene's long product. It is not mapped to isoform C, which has not been localized. Supporting Evidence: PMID:19013444 whereas Glo and Hrp48 are both nuclear and cytoplasmic |
| GO:0005737 cytoplasm | IDA PMID:16516833 Glorund, a Drosophila hnRNP F/H homolog, is an ovarian repre... | NEW | Summary: The cytoplasmic pool, in the oocyte and in nurse cells, is where Glo represses nanos translation. Reason: Glo is both nuclear and cytoplasmic (PMID:19013444, citing Kalifa et al. 2006). It represses nanos mRNA that remains in the bulk oocyte cytoplasm (PMID:28380354), and it acts on translating ribosomes through dFMRP (PMID:35699205), so its translational activity is cytoplasmic. Isoform C has not been localized. Supporting Evidence: PMID:19013444 whereas Glo and Hrp48 are both nuclear and cytoplasmic PMID:28380354 the repression of nos mRNA remaining within the bulk cytoplasm |
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Download this section (compressed HTML)Q: Is Glorund isoform C (Q8INJ6, with one complete qRRM plus 27 residues of qRRM2) made as a stable protein, and does it act as a dominant-negative competitor of full-length Glo for G-tract targets?
Q: Does Glo bind otu pre-mRNA directly, or is otu splicing regulated indirectly through Half-pint? The answer would decide whether a splicing-regulation process term (for example GO:0000381) is warranted.
Experiment: Express tagged isoform C (Q8INJ6) in glo mutant ovaries and test nanos co-immunoprecipitation, Nos repression, and rescue of nurse-cell chromosome dispersion and gurken localization. Compare with the full-length product.
Type: transgenic rescue / RNA immunoprecipitation
Experiment: CLIP or RIP-seq of endogenous Glo in ovaries to identify otu and other G-tract targets.
Type: CLIP-seq
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Download this section (compressed HTML)glorund (glo) encodes a hnRNP F/H family RNA-binding protein that binds directly to nanos mRNA and regulates its translation during late stages of oogenesis. The functions of the product of glo include nurse cell nuclear chromatin organization, axis patterning as well as being required for viability to adulthood.
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