Dvir\GJ15622 (UniProt B4MAQ2) is a predicted Exportin-5-like nuclear transport receptor in Drosophila virilis. The protein belongs to the karyopherin-beta (exportin) family and contains the hallmark domain architecture of Exportin-5 orthologs: an N-terminal Importin-beta domain (IBN_N, Pfam PF03810), an Exportin-1/Importin-beta-like domain (Xpo1, Pfam PF08389), and a C-terminal Exportin-5 signature domain (Pfam PF19273). Exportin-5 proteins function as RanGTP-dependent nuclear export receptors that recognize and export structured double-stranded RNAs, most notably pre-miRNAs and, in Drosophila, also pre-tRNAs and tRNAs, through the nuclear pore complex. In Drosophila species, Exportin-5 compensates for the absence of a canonical Exportin-t and thus serves as the primary factor for tRNA nuclear export in addition to its role in miRNA biogenesis. The protein shuttles between the nucleus and cytoplasm, loading cargo in complex with RanGTP in the nucleus, traversing the nuclear pore, and releasing cargo in the cytoplasm upon GTP hydrolysis. No direct experimental studies have been performed on this specific D. virilis protein; functional annotation is inferred from conserved domain architecture, exportin-family membership, and well-characterized Drosophila orthologs.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0003723
RNA binding
|
IEA
GO_REF:0000118 |
ACCEPT |
Summary: Exportin-5 proteins directly bind structured double-stranded RNAs (pre-miRNAs, tRNAs) as their transport cargo in a RanGTP-cooperative manner. RNA binding is a mechanistically central property of this transport receptor. However, "RNA binding" is a broad parent term; the more informative annotation would specify the type of RNA interaction (e.g., double-stranded RNA binding or structured RNA recognition). Nevertheless, RNA binding is correct and well-supported by the exportin-5 family assignment.
Reason: RNA binding is a genuine molecular function of Exportin-5 proteins, which directly contact structured RNA cargo. The term is somewhat broad but accurately reflects the protein's activity.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
Exportin-5 specializes as a RanGTP-dependent nuclear export receptor for double-stranded, minihelix RNA structures
file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
GO; GO:0003723; F:RNA binding; IEA:TreeGrafter
|
|
GO:0005049
nuclear export signal receptor activity
|
IEA
GO_REF:0000120 |
REMOVE |
Summary: Nuclear export signal (NES) receptor activity is the function of recognizing leucine-rich nuclear export signals on protein cargo, which is the hallmark activity of Exportin-1/CRM1, not Exportin-5. Exportin-5 recognizes structured RNA cargo (pre-miRNAs, tRNAs) through structure-dependent rather than NES-mediated recognition. This annotation appears to arise from the shared XPO1/5 InterPro family (IPR045065), which groups CRM1 and Exportin-5 together, but the NES receptor function is specific to the CRM1 branch. Although B4MAQ2 contains an Xpo1 domain, its overall domain architecture (particularly the Exportin-5_C domain) and PANTHER subfamily assignment (EXPORTIN-5, PTHR11223:SF3) place it firmly as an Exportin-5 ortholog rather than a CRM1/XPO1 ortholog.
Reason: NES receptor activity is specific to CRM1/Exportin-1. This protein's domain architecture and subfamily classification identify it as Exportin-5, which exports structured RNA cargo, not NES-bearing proteins. The annotation likely results from overgeneralization of the XPO1/5 superfamily InterPro entry.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
Exportin-5_C domain is the strongest clue that Dvir\GJ15622 is more likely XPO5-like than another exportin subtype
file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
PANTHER; PTHR11223:SF3; EXPORTIN-5; 1
|
|
GO:0005634
nucleus
|
IEA
GO_REF:0000118 |
ACCEPT |
Summary: Exportin-5 operates throughout the nucleocytoplasmic transport pathway and is present in the nucleus where it loads cargo in complex with RanGTP. Nuclear localization is expected and well-supported by the exportin family biology.
Reason: Nuclear localization is a fundamental aspect of exportin function, as these receptors must be present in the nucleus to bind cargo and RanGTP before translocation through the nuclear pore.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
they are present in the nucleus (where they bind cargo and RanGTP)
|
|
GO:0005737
cytoplasm
|
IEA
GO_REF:0000118 |
ACCEPT |
Summary: Exportin-5 shuttles to the cytoplasm where it releases cargo after RanGTP hydrolysis. Cytoplasmic localization is an expected and necessary part of the nucleocytoplasmic transport cycle.
Reason: Cytoplasmic presence is intrinsic to the exportin transport cycle, where cargo is released and the receptor is recycled back to the nucleus.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
in the cytoplasm (where they release cargo upon RanGTP hydrolysis)
|
|
GO:0006405
RNA export from nucleus
|
IEA
GO_REF:0000118 |
ACCEPT |
Summary: RNA export from the nucleus is the primary biological process in which Exportin-5 participates. In Drosophila, Exportin-5 mediates the nuclear export of pre-miRNAs, pre-tRNAs, and other structured RNAs. This is a well-supported core function of the protein.
Reason: RNA nuclear export is the central biological process for Exportin-5 proteins, directly supported by the domain architecture and Drosophila Exportin-5 literature showing export of pre-miRNAs and tRNAs.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
In flies, Exp5 is a major RNA export receptor and can compensate for missing canonical Exportin-t functions in tRNA export
|
|
GO:0006611
protein export from nucleus
|
IEA
GO_REF:0000120 |
REMOVE |
Summary: Protein export from the nucleus is characteristic of CRM1/Exportin-1, which recognizes leucine-rich NES motifs on protein cargo. Exportin-5 is primarily an RNA export receptor. While some exportins have minor protein cargo, the PANTHER subfamily assignment (EXPORTIN-5) and domain architecture strongly indicate that this protein functions in RNA export, not protein export. This annotation likely arises from the shared XPO1/5 InterPro classification.
Reason: Protein nuclear export is the function of CRM1/Exportin-1, not Exportin-5. This protein's Exportin-5_C domain and PANTHER EXPORTIN-5 subfamily assignment indicate it is an RNA transporter, and this annotation appears to be an overgeneralization from the XPO1/5 family.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
likely cargo class is structured RNA rather than leucine-rich NES-bearing proteins
file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
PANTHER; PTHR11223:SF3; EXPORTIN-5; 1
|
|
GO:0006886
intracellular protein transport
|
IEA
GO_REF:0000002 |
MODIFY |
Summary: This term was assigned via InterPro mapping from the Importin-beta_N domain (IPR001494), which is shared across karyopherin-beta family members including both importins and exportins. While karyopherin-beta proteins are involved in nucleocytoplasmic transport, Exportin-5 specifically transports RNA, not protein cargo. The term "intracellular protein transport" is misleading for an RNA export receptor.
Reason: The annotation confounds the transport of the receptor itself (which shuttles as a protein) with the cargo it carries. Exportin-5 transports RNA cargo, not protein cargo. A more accurate process term would reflect RNA transport.
Proposed replacements:
RNA export from nucleus
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
most evidence-based prediction is transporter function for structured RNAs, not small molecules
|
|
GO:0031267
small GTPase binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: Exportin-5, like all karyopherin-beta transport receptors, binds RanGTPase (a small GTPase) as a central part of the transport mechanism. Ran-GTP binding in the nucleus promotes cargo loading, and GTP hydrolysis in the cytoplasm triggers cargo release. This annotation is derived from the Importin-beta_N domain (IPR001494) via InterPro mapping and correctly reflects the Ran-binding capability of all karyopherin-beta proteins.
Reason: Small GTPase (Ran) binding is a mechanistically essential function of all karyopherin-beta transport receptors, including Exportin-5. The annotation is correct, though a more specific term like "Ran GTPase binding" (GO:0005099) would be more informative if available in the annotation pipelines.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
Exportins bind cargo cooperatively with RanGTP in the nucleus to form a trimeric export complex
|
|
GO:0042565
RNA nuclear export complex
|
IEA
GO_REF:0000118 |
ACCEPT |
Summary: Exportin-5 forms a trimeric RNA nuclear export complex with its RNA cargo and RanGTP. The complex assembles in the nucleus and traverses the nuclear pore complex for cytoplasmic cargo delivery. Membership in this complex is consistent with the known biology of Exportin-5 proteins.
Reason: The RNA nuclear export complex is the functional assembly through which Exportin-5 performs its transport activity, supported by extensive biochemical and structural evidence from the exportin-5 literature.
Supporting Evidence:
file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
Exportin-5 binds cargo in cooperation with RanGTP, forming a trimeric export complex
|
Q: Is Dvir\GJ15622 the sole Exportin-5 ortholog in D. virilis, and does it fully compensate for the lack of Exportin-t as shown for D. melanogaster Exportin-5?
Q: Does this protein have any protein cargo in addition to structured RNA substrates, or is its function entirely restricted to RNA export?
Experiment: Perform PAR-CLIP or eCLIP in D. virilis cells to identify the RNA substrates bound by B4MAQ2 in vivo, followed by subcellular fractionation to confirm nucleocytoplasmic shuttling. Compare the RNA cargo profile to that reported for D. melanogaster Exportin-5.
Hypothesis: B4MAQ2 functions as a nuclear export receptor for pre-miRNAs and pre-tRNAs in D. virilis cells.
Type: PAR-CLIP/eCLIP with subcellular fractionation
Experiment: Express and purify recombinant B4MAQ2 and test RanGTP-dependent binding to pre-miRNA and tRNA substrates in vitro using electrophoretic mobility shift assays or fluorescence anisotropy.
Hypothesis: B4MAQ2 binds RanGTP and forms a trimeric export complex with structured RNA cargo.
Type: In vitro binding assay (EMSA/fluorescence anisotropy)
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
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The gene symbol Dvir\GJ15622 (UniProt Accession: B4MAQ2) is confirmed to encode an uncharacterized protein in Drosophila virilis, with UniProt curation indicating it belongs to the exportin (karyopherin-beta) family. The organism is correct (Drosophila virilis), and the domain architecture includes ARM-like, Importin-beta_N, Exportin-5_C, and other hallmark exportin domains (wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 2-3, yang2023nucleartransportproteins pages 9-10). No evidence was found for any homolog or symbol ambiguity in a different organism context. No gene-specific literature exists for Dvir\GJ15622; function must be inferred from family and domain assignments.
Exportins are a subclass of karyopherin-beta transport receptors responsible for the nuclear export of proteins and RNAs in eukaryotic cells. They bind cargoes in the nucleus in cooperation with RanGTP and facilitate translocation through the nuclear pore complex (NPC). Once in the cytoplasm, they release cargo after GTP hydrolysis. Exportin-5 (XPO5) is a prototypical member that mediates export of specific structured RNAs, including pre-miRNAs and tRNAs, often through structure- rather than sequence-specific recognition (bohnsack2004exportin5is pages 1-2, li2024exportin5bindingprecedes pages 1-2, bohnsack2004exportin5is pages 3-5, yang2023nucleartransportproteins pages 9-10).
Exportin-5 and related exportins are built from tandem ARM/HEAT repeats (alpha-helical structures) creating a superhelical, flexible scaffold. The N-terminal Importin-beta_N domain and the C-terminal Exportin-5 signature are classic structural features. These confer the ability to form a "baseball mitt-like" binding site for RNA substrates, with the ARM/HEAT domains contributing to flexibility and cargo recognition (li2024exportin5bindingprecedes pages 1-2, yang2023nucleartransportproteins pages 2-3, yang2023nucleartransportproteins pages 9-10). Dvir\GJ15622 harbors all these domain features, substantiating its annotation as an exportin.
Exportins, including Exportin-5, operate throughout the nucleocytoplasmic transport pathway: they are present in the nucleus (where they bind cargo and RanGTP), at the nuclear pore complex (where they translocate), and in the cytoplasm (where they release cargo upon RanGTP hydrolysis) (bohnsack2004exportin5is pages 1-2, yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 9-10).
Exportin-5 specializes as a RanGTP-dependent nuclear export receptor for double-stranded, minihelix RNA structures, most notably pre-miRNAs, pre-tRNAs, and other structured noncoding RNAs. It does this via sequence-independent but structure-dependent recognition, with clear evidence that in Drosophila, Exportin-5 binds and exports both pre-miRNAs and pre-tRNAs, and may have a broader RNA substrate repertoire than in some other organisms (li2024exportin5bindingprecedes pages 1-2, bohnsack2004exportin5is pages 3-5).
Mechanism:
- In the nucleus, Exportin-5 binds cargo in cooperation with RanGTP, forming a trimeric export complex.
- This complex traverses the nuclear pore complex, interacting with FG-nucleoporins to facilitate passage.
- In the cytoplasm, GTP is hydrolyzed, leading to cargo release and recycling of the exportin back to the nucleus (bohnsack2004exportin5is pages 1-2, bohnsack2004exportin5is pages 2-3, bohnsack2004exportin5is pages 3-5, yang2023nucleartransportproteins pages 9-10).
In Drosophila, Exportin-5 also compensates for the absence of a canonical Exportin-t, acting as the major factor for tRNA export as well as pre-miRNA transport (li2024exportin5bindingprecedes pages 1-2).
Exportin-5βs main roles include:
- miRNA biogenesis: Nuclear export of pre-miRNAs for further cytoplasmic processing (kim2025thebiogenesisand pages 1-4).
- tRNA maturation/export: Especially pronounced in Drosophila, where Exp5 exports pre-tRNAs and tRNAs, including unprocessed forms (li2024exportin5bindingprecedes pages 1-2).
- General nucleocytoplasmic transport: Exportins are essential for maintaining nuclear/cytoplasmic compartmentalization, contributing to gene expression regulation and developmental control (yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 9-10).
Exportin family proteins are also being studied as clinical targets, e.g., inhibitors of XPO1 (CRM1) for cancer therapy (yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 9-10).
Recent reviews and experimental studies in Signal Transduction and Targeted Therapy (Yang et al. 2023, https://doi.org/10.1038/s41392-023-01649-4), Nature Reviews Molecular Cell Biology (Kim et al. 2025, https://doi.org/10.1038/s41580-024-00805-0), and RNA (Bohnsack et al. 2004, https://doi.org/10.1261/rna.5167604) provide consensus on the centrality of karyopherin-beta family proteins in eukaryotic transport, including detailed mechanisms, structural models, and biological implications. These authoritative sources support the proposed model function for Dvir\GJ15622 as an Exportin-5-like structured RNA export receptor.
| Protein / feature class | Key domains / architecture | Cellular localization | Substrate / cargo specificity | Mechanism of action | Biological processes / pathway context | Relevance to Drosophila virilis Dvir\GJ15622 (UniProt B4MAQ2) |
|---|---|---|---|---|---|---|
| Exportin family (general; karyopherin-Ξ² export receptors) | Members of the karyopherin-Ξ² superfamily; built from tandem Ξ±-solenoid repeats, commonly HEAT/ARM-like repeats that create a flexible superhelical scaffold for cargo, RanGTP, and FG-nucleoporin interactions (wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 2-3, yang2023nucleartransportproteins pages 9-10) | Shuttle between nucleus, nuclear pore complex (NPC), and cytoplasm; function at the nuclear envelope/NPC and in nucleoplasm/cytoplasm because exportins load cargo in the nucleus and release it after export to cytoplasm (bohnsack2004exportin5is pages 1-2, yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 9-10) | Exportins recognize specific protein or RNA cargo classes, often through structural motifs or adaptor-dependent signals; different exportins specialize for distinct cargoes such as pre-miRNA, tRNA, actin/profilin, or NES-bearing proteins (bohnsack2004exportin5is pages 1-2, yang2023nucleartransportproteins pages 9-10) | Exportins bind cargo cooperatively with RanGTP in the nucleus to form a trimeric export complex, traverse the NPC via FG-repeat interactions, and release cargo in the cytoplasm after RanGTP hydrolysis promoted by RanGAP/RanBP factors (bohnsack2004exportin5is pages 1-2, yang2023nucleartransportproteins pages 9-10) | Core nucleocytoplasmic transport system; contributes to RNA biogenesis, gene-expression control, maintenance of nuclear/cytoplasmic compartment identity, and developmental regulation (yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 9-10) | UniProt assigns B4MAQ2 to the exportin family and lists ARM-like, ARM-type fold, Importin-beta_N, Exportin-1/Importin-b-like, and Exportin-5_C domains, strongly supporting annotation as a RanGTP-dependent nuclear export receptor rather than an enzyme or structural protein (wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 2-3, yang2023nucleartransportproteins pages 9-10) |
| Exportin-5 / XPO5 (structural model) | ~20 HEAT-repeat / ARM-like Ξ±-helical solenoid described as a βbaseball mitt-likeβ structure; Importin-Ξ²-like N-terminal region participates in canonical karyopherin architecture; C-terminal regions contribute to RNA-binding geometry and export complex formation (li2024exportin5bindingprecedes pages 1-2, yang2023nucleartransportproteins pages 2-3) | Nucleocytoplasmic shuttle enriched at sites of nuclear RNA export; acts in nucleus for cargo loading, at NPC for translocation, and in cytoplasm for cargo release (bohnsack2004exportin5is pages 1-2, li2024exportin5bindingprecedes pages 1-2, yang2023nucleartransportproteins pages 9-10) | Best-characterized cargoes are pre-miRNAs; also binds tRNAs and other minihelix-containing RNAs, including 7SL RNA and some structured viral RNAs; in Drosophila, Exp5 can bind pre-tRNAs and additional structured RNAs/mRNAs/lncRNAs (bohnsack2004exportin5is pages 1-2, li2024exportin5bindingprecedes pages 1-2, bohnsack2004exportin5is pages 3-5) | RanGTP-dependent export receptor; directly binds dsRNA/minihelix cargoes in a sequence-independent but structure-dependent manner; forms export complexes with cargo and RanGTP in nucleus and releases cargo after cytoplasmic GTP hydrolysis (bohnsack2004exportin5is pages 1-2, bohnsack2004exportin5is pages 2-3, bohnsack2004exportin5is pages 3-5, yang2023nucleartransportproteins pages 9-10) | miRNA biogenesis, tRNA export, export of selected structured noncoding RNAs, and broader RNA-processing/export coordination (li2024exportin5bindingprecedes pages 1-2, kim2025thebiogenesisand pages 1-4) | Because B4MAQ2 contains both Importin-beta_N and Exportin-5_C signatures, the closest functional inference is that Dvir\GJ15622 is an Exportin-5-like transporter specialized for structured RNA export (li2024exportin5bindingprecedes pages 1-2, yang2023nucleartransportproteins pages 2-3) |
| ARM-like / ARM-type fold contribution | ARM-like Ξ±-helical repeats provide a curved interaction surface and structural flexibility; in karyopherin-like proteins these repeats participate in cargo recognition and conformational switching (wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 2-3) | Present throughout the soluble receptor as part of the nucleocytoplasmic shuttle machinery (wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 2-3) | Indirectly determines specificity by shaping binding grooves/tunnels for structured RNA or other cargo features (li2024exportin5bindingprecedes pages 1-2, bohnsack2004exportin5is pages 3-5) | Enables conformational plasticity needed for RanGTP-dependent assembly/disassembly and FG-nucleoporin engagement (yang2023nucleartransportproteins pages 11-12, yang2023nucleartransportproteins pages 9-10) | Supports selective macromolecular transport through NPCs (yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 11-12) | Presence of ARM-like and ARM-type fold annotations in B4MAQ2 is consistent with a soluble transport receptor scaffold rather than catalytic activity (yang2023nucleartransportproteins pages 2-3, yang2023nucleartransportproteins pages 9-10) |
| Importin-beta_N domain contribution | N-terminal importin-Ξ²-like region is characteristic of karyopherin receptors and participates in the canonical transport-receptor fold and Ran-regulated transport cycle (wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 9-10) | Operates in nucleus/cytoplasm/NPC as part of the shuttling receptor (yang2023nucleartransportproteins pages 9-10) | Does not define cargo alone, but contributes to receptor identity and transport-factor interactions (yang2023nucleartransportproteins pages 9-10) | Supports RanGTP-coupled transport and interactions with the NPC transport channel (bohnsack2004exportin5is pages 1-2, yang2023nucleartransportproteins pages 9-10) | Essential for directed nucleocytoplasmic transport (yang2023nucleartransportproteins pages 1-2, yang2023nucleartransportproteins pages 9-10) | Its presence in B4MAQ2 strongly supports assignment to the karyopherin/exportin transport machinery (yang2023nucleartransportproteins pages 9-10) |
| Exportin-5_C domain contribution | C-terminal Exportin-5 signature region associated with XPO5-like receptors; contributes to RNA-binding architecture and cargo selectivity for minihelix/overhang-containing RNAs (li2024exportin5bindingprecedes pages 1-2) | Same shuttling localization as full receptor (li2024exportin5bindingprecedes pages 1-2, yang2023nucleartransportproteins pages 9-10) | Associated especially with pre-miRNA and other minihelix RNA recognition (li2024exportin5bindingprecedes pages 1-2) | Works with the HEAT-repeat scaffold to create the RNA-binding surface/tunnel that recognizes duplex RNA features such as short stems and 3β² overhangs (li2024exportin5bindingprecedes pages 1-2) | Connects nuclear RNA processing to cytoplasmic maturation pathways, especially small-RNA pathways (li2024exportin5bindingprecedes pages 1-2, kim2025thebiogenesisand pages 1-4) | This domain is the strongest clue that Dvir\GJ15622 is more likely XPO5-like than another exportin subtype; likely cargo class is structured RNA rather than leucine-rich NES-bearing proteins (li2024exportin5bindingprecedes pages 1-2) |
| Cargo recognition principle of Exportin-5 | Structural recognition dominates over primary sequence; Exp5 binds double-stranded/minihelix RNA in a largely sequence-independent manner (bohnsack2004exportin5is pages 1-2, bohnsack2004exportin5is pages 3-5) | Nucleus for loading; cytoplasm after export for unloading (bohnsack2004exportin5is pages 1-2, yang2023nucleartransportproteins pages 9-10) | Pre-miRNA hairpins, tRNAs, pre-tRNAs in Drosophila, and other structured RNAs with short dsRNA stems and often 3β² overhangs (li2024exportin5bindingprecedes pages 1-2, bohnsack2004exportin5is pages 3-5) | Direct RNA binding plus RanGTP cooperation; competition data indicate overlapping binding logic for pre-miRNA and tRNA on Exp5 (bohnsack2004exportin5is pages 2-3, bohnsack2004exportin5is pages 3-5) | Small RNA maturation and RNA trafficking (li2024exportin5bindingprecedes pages 1-2, kim2025thebiogenesisand pages 1-4) | For B4MAQ2, the most evidence-based prediction is transporter function for structured RNAs, not small molecules; exact substrate cannot be assigned without experiment, but pre-miRNA/pre-tRNA-like cargo is plausible (li2024exportin5bindingprecedes pages 1-2, bohnsack2004exportin5is pages 3-5) |
| Drosophila Exportin-5 biology | In flies, Exp5 is a major RNA export receptor and can compensate for missing canonical Exportin-t functions in tRNA export; PAR-CLIP identified tRNAs, pre-tRNAs, miRNAs, and additional candidate RNAs as substrates (li2024exportin5bindingprecedes pages 1-2) | Expected nucleocytoplasmic localization associated with RNA export pathway (li2024exportin5bindingprecedes pages 1-2) | Strong evidence for tRNA/pre-tRNA and pre-miRNA export in Drosophila (li2024exportin5bindingprecedes pages 1-2) | Binding can precede complete tRNA end processing in Drosophila, implying a broader or earlier substrate-recognition stage than in some other systems (li2024exportin5bindingprecedes pages 1-2) | Links tRNA maturation/export and miRNA biogenesis in flies (li2024exportin5bindingprecedes pages 1-2) | Since the target protein is from Drosophila virilis, phylogenetic context strengthens the inference that Dvir\GJ15622 may participate in structured RNA export, potentially including pre-tRNAs and pre-miRNAs, though this remains untested for this exact protein (li2024exportin5bindingprecedes pages 1-2) |
| Evidence limitations for Dvir\GJ15622 | No direct gene-specific literature located for Dvir\GJ15622 / B4MAQ2 | Unknown experimentally | Unknown experimentally | Inferred from family/domain architecture only | Unknown experimentally | The safest annotation is: uncharacterized exportin-family, likely Exportin-5-like, ARM/HEAT-repeat nucleocytoplasmic transport receptor acting at nucleusβNPCβcytoplasm interfaces in RanGTP-dependent export of structured RNAs; substrate specificity and biological role in D. virilis require direct validation (li2024exportin5bindingprecedes pages 1-2, wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6, yang2023nucleartransportproteins pages 2-3, yang2023nucleartransportproteins pages 9-10) |
Table: This table summarizes the conserved structural and functional properties of exportin family proteins, especially Exportin-5, and maps those features onto the uncharacterized Drosophila virilis protein Dvir\GJ15622. It is useful for inferring likely function, localization, and cargo class when direct gene-specific literature is lacking.
No direct studies of Dvir\GJ15622 protein biochemistry in Drosophila virilis have been identified. Functional annotation is therefore predictive, based on robust domain structure and exportin-5 family homology. Experimental characterization in D. virilis is the next step to confirm RNA cargo specificity, transport activity, and biological roles.
References:
- Bohnsack MT, Czaplinski K, GΓΆrlich D. Exportin 5 is a RanGTP-dependent dsRNA-binding protein that mediates nuclear export of pre-miRNAs. RNA. 2004;10(2):185-191. doi:10.1261/rna.5167604. https://doi.org/10.1261/rna.5167604
- Li Z, Iida J, Shiimori M, Okamura K. Exportin-5 binding precedes 5β²- and 3β²-end processing of tRNA precursors in Drosophila. J Biol Chem. 2024;300(9):107632. doi:10.1016/j.jbc.2024.107632. https://doi.org/10.1016/j.jbc.2024.107632
- Yang Y, Guo L, Chen L, et al. Nuclear transport proteins: structure, function and disease relevance. Signal Transduction and Targeted Therapy. 2023;8:425. doi:10.1038/s41392-023-01649-4. https://doi.org/10.1038/s41392-023-01649-4
- Kim H, Lee Y-Y, Kim VN. The biogenesis and regulation of animal microRNAs. Nat Rev Mol Cell Biol. 2025. doi:10.1038/s41580-024-00805-0. https://doi.org/10.1038/s41580-024-00805-0
- Pasha T, Zatorska A, Sharipov D, et al. Karyopherin abnormalities in neurodegenerative proteinopathies. Brain. 2021;144:2915-2932. doi:10.1093/brain/awab201. https://doi.org/10.1093/brain/awab201
References
(wing2022karyopherinmediatednucleocytoplasmictransport pages 1-6): Casey E. Wing, Ho Yee Joyce Fung, and Yuh Min Chook. Karyopherin-mediated nucleocytoplasmic transport. Nature Reviews Molecular Cell Biology, 23:307-328, Jan 2022. URL: https://doi.org/10.1038/s41580-021-00446-7, doi:10.1038/s41580-021-00446-7. This article has 315 citations and is from a domain leading peer-reviewed journal.
(yang2023nucleartransportproteins pages 2-3): Yang Yang, Lu Guo, Lin Chen, Bo Gong, Da Jia, and Qingxiang Sun. Nuclear transport proteins: structure, function and disease relevance. Signal Transduction and Targeted Therapy, Nov 2023. URL: https://doi.org/10.1038/s41392-023-01649-4, doi:10.1038/s41392-023-01649-4. This article has 187 citations and is from a peer-reviewed journal.
(yang2023nucleartransportproteins pages 9-10): Yang Yang, Lu Guo, Lin Chen, Bo Gong, Da Jia, and Qingxiang Sun. Nuclear transport proteins: structure, function and disease relevance. Signal Transduction and Targeted Therapy, Nov 2023. URL: https://doi.org/10.1038/s41392-023-01649-4, doi:10.1038/s41392-023-01649-4. This article has 187 citations and is from a peer-reviewed journal.
(bohnsack2004exportin5is pages 1-2): MARKUS T. BOHNSACK, KEVIN CZAPLINSKI, and DIRK GΓRLICH. Exportin 5 is a rangtp-dependent dsrna-binding protein that mediates nuclear export of pre-mirnas. RNA, 10 2:185-91, Feb 2004. URL: https://doi.org/10.1261/rna.5167604, doi:10.1261/rna.5167604. This article has 2488 citations and is from a domain leading peer-reviewed journal.
(li2024exportin5bindingprecedes pages 1-2): Ze Li, Junko Iida, Masami Shiimori, and Katsutomo Okamura. Exportin-5 binding precedes 5β²- and 3β²-end processing of trna precursors in drosophila. Sep 2024. URL: https://doi.org/10.1016/j.jbc.2024.107632, doi:10.1016/j.jbc.2024.107632. This article has 1 citations and is from a domain leading peer-reviewed journal.
(bohnsack2004exportin5is pages 3-5): MARKUS T. BOHNSACK, KEVIN CZAPLINSKI, and DIRK GΓRLICH. Exportin 5 is a rangtp-dependent dsrna-binding protein that mediates nuclear export of pre-mirnas. RNA, 10 2:185-91, Feb 2004. URL: https://doi.org/10.1261/rna.5167604, doi:10.1261/rna.5167604. This article has 2488 citations and is from a domain leading peer-reviewed journal.
(yang2023nucleartransportproteins pages 1-2): Yang Yang, Lu Guo, Lin Chen, Bo Gong, Da Jia, and Qingxiang Sun. Nuclear transport proteins: structure, function and disease relevance. Signal Transduction and Targeted Therapy, Nov 2023. URL: https://doi.org/10.1038/s41392-023-01649-4, doi:10.1038/s41392-023-01649-4. This article has 187 citations and is from a peer-reviewed journal.
(bohnsack2004exportin5is pages 2-3): MARKUS T. BOHNSACK, KEVIN CZAPLINSKI, and DIRK GΓRLICH. Exportin 5 is a rangtp-dependent dsrna-binding protein that mediates nuclear export of pre-mirnas. RNA, 10 2:185-91, Feb 2004. URL: https://doi.org/10.1261/rna.5167604, doi:10.1261/rna.5167604. This article has 2488 citations and is from a domain leading peer-reviewed journal.
(kim2025thebiogenesisand pages 1-4): Haedong Kim, Young-Yoon Lee, and V. Narry Kim. The biogenesis and regulation of animal micrornas. Nature reviews. Molecular cell biology, Dec 2025. URL: https://doi.org/10.1038/s41580-024-00805-0, doi:10.1038/s41580-024-00805-0. This article has 165 citations.
(yang2023nucleartransportproteins pages 11-12): Yang Yang, Lu Guo, Lin Chen, Bo Gong, Da Jia, and Qingxiang Sun. Nuclear transport proteins: structure, function and disease relevance. Signal Transduction and Targeted Therapy, Nov 2023. URL: https://doi.org/10.1038/s41392-023-01649-4, doi:10.1038/s41392-023-01649-4. This article has 187 citations and is from a peer-reviewed journal.
id: B4MAQ2
gene_symbol: B4MAQ2
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:7244
label: Drosophila virilis
description: >-
Dvir\GJ15622 (UniProt B4MAQ2) is a predicted Exportin-5-like nuclear transport
receptor in Drosophila virilis. The protein belongs to the karyopherin-beta
(exportin) family and contains the hallmark domain architecture of Exportin-5
orthologs: an N-terminal Importin-beta domain (IBN_N, Pfam PF03810), an
Exportin-1/Importin-beta-like domain (Xpo1, Pfam PF08389), and a C-terminal
Exportin-5 signature domain (Pfam PF19273). Exportin-5 proteins function as
RanGTP-dependent nuclear export receptors that recognize and export structured
double-stranded RNAs, most notably pre-miRNAs and, in Drosophila, also
pre-tRNAs and tRNAs, through the nuclear pore complex. In Drosophila species,
Exportin-5 compensates for the absence of a canonical Exportin-t and thus
serves as the primary factor for tRNA nuclear export in addition to its role
in miRNA biogenesis. The protein shuttles between the nucleus and cytoplasm,
loading cargo in complex with RanGTP in the nucleus, traversing the nuclear
pore, and releasing cargo in the cytoplasm upon GTP hydrolysis. No direct
experimental studies have been performed on this specific D. virilis protein;
functional annotation is inferred from conserved domain architecture,
exportin-family membership, and well-characterized Drosophila orthologs.
existing_annotations:
- term:
id: GO:0003723
label: RNA binding
evidence_type: IEA
original_reference_id: GO_REF:0000118
qualifier: enables
review:
summary: >-
Exportin-5 proteins directly bind structured double-stranded RNAs
(pre-miRNAs, tRNAs) as their transport cargo in a RanGTP-cooperative
manner. RNA binding is a mechanistically central property of this
transport receptor. However, "RNA binding" is a broad parent term; the
more informative annotation would specify the type of RNA interaction
(e.g., double-stranded RNA binding or structured RNA recognition).
Nevertheless, RNA binding is correct and well-supported by the
exportin-5 family assignment.
action: ACCEPT
reason: >-
RNA binding is a genuine molecular function of Exportin-5 proteins,
which directly contact structured RNA cargo. The term is somewhat
broad but accurately reflects the protein's activity.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "Exportin-5 specializes as a RanGTP-dependent nuclear export receptor for double-stranded, minihelix RNA structures"
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
supporting_text: "GO; GO:0003723; F:RNA binding; IEA:TreeGrafter"
- term:
id: GO:0005049
label: nuclear export signal receptor activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
qualifier: enables
review:
summary: >-
Nuclear export signal (NES) receptor activity is the function of
recognizing leucine-rich nuclear export signals on protein cargo, which
is the hallmark activity of Exportin-1/CRM1, not Exportin-5. Exportin-5
recognizes structured RNA cargo (pre-miRNAs, tRNAs) through
structure-dependent rather than NES-mediated recognition. This annotation
appears to arise from the shared XPO1/5 InterPro family (IPR045065),
which groups CRM1 and Exportin-5 together, but the NES receptor function
is specific to the CRM1 branch. Although B4MAQ2 contains an Xpo1 domain,
its overall domain architecture (particularly the Exportin-5_C domain)
and PANTHER subfamily assignment (EXPORTIN-5, PTHR11223:SF3) place it
firmly as an Exportin-5 ortholog rather than a CRM1/XPO1 ortholog.
action: REMOVE
reason: >-
NES receptor activity is specific to CRM1/Exportin-1. This protein's
domain architecture and subfamily classification identify it as
Exportin-5, which exports structured RNA cargo, not NES-bearing proteins.
The annotation likely results from overgeneralization of the XPO1/5
superfamily InterPro entry.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "Exportin-5_C domain is the strongest clue that Dvir\\GJ15622 is more likely XPO5-like than another exportin subtype"
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
supporting_text: "PANTHER; PTHR11223:SF3; EXPORTIN-5; 1"
- term:
id: GO:0005634
label: nucleus
evidence_type: IEA
original_reference_id: GO_REF:0000118
qualifier: located_in
review:
summary: >-
Exportin-5 operates throughout the nucleocytoplasmic transport pathway
and is present in the nucleus where it loads cargo in complex with
RanGTP. Nuclear localization is expected and well-supported by the
exportin family biology.
action: ACCEPT
reason: >-
Nuclear localization is a fundamental aspect of exportin function, as
these receptors must be present in the nucleus to bind cargo and RanGTP
before translocation through the nuclear pore.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "they are present in the nucleus (where they bind cargo and RanGTP)"
- term:
id: GO:0005737
label: cytoplasm
evidence_type: IEA
original_reference_id: GO_REF:0000118
qualifier: located_in
review:
summary: >-
Exportin-5 shuttles to the cytoplasm where it releases cargo after
RanGTP hydrolysis. Cytoplasmic localization is an expected and necessary
part of the nucleocytoplasmic transport cycle.
action: ACCEPT
reason: >-
Cytoplasmic presence is intrinsic to the exportin transport cycle, where
cargo is released and the receptor is recycled back to the nucleus.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "in the cytoplasm (where they release cargo upon RanGTP hydrolysis)"
- term:
id: GO:0006405
label: RNA export from nucleus
evidence_type: IEA
original_reference_id: GO_REF:0000118
qualifier: involved_in
review:
summary: >-
RNA export from the nucleus is the primary biological process in which
Exportin-5 participates. In Drosophila, Exportin-5 mediates the nuclear
export of pre-miRNAs, pre-tRNAs, and other structured RNAs. This is a
well-supported core function of the protein.
action: ACCEPT
reason: >-
RNA nuclear export is the central biological process for Exportin-5
proteins, directly supported by the domain architecture and Drosophila
Exportin-5 literature showing export of pre-miRNAs and tRNAs.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "In flies, Exp5 is a major RNA export receptor and can compensate for missing canonical Exportin-t functions in tRNA export"
- term:
id: GO:0006611
label: protein export from nucleus
evidence_type: IEA
original_reference_id: GO_REF:0000120
qualifier: involved_in
review:
summary: >-
Protein export from the nucleus is characteristic of CRM1/Exportin-1,
which recognizes leucine-rich NES motifs on protein cargo. Exportin-5 is
primarily an RNA export receptor. While some exportins have minor protein
cargo, the PANTHER subfamily assignment (EXPORTIN-5) and domain
architecture strongly indicate that this protein functions in RNA export,
not protein export. This annotation likely arises from the shared XPO1/5
InterPro classification.
action: REMOVE
reason: >-
Protein nuclear export is the function of CRM1/Exportin-1, not
Exportin-5. This protein's Exportin-5_C domain and PANTHER EXPORTIN-5
subfamily assignment indicate it is an RNA transporter, and this
annotation appears to be an overgeneralization from the XPO1/5 family.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "likely cargo class is structured RNA rather than leucine-rich NES-bearing proteins"
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
supporting_text: "PANTHER; PTHR11223:SF3; EXPORTIN-5; 1"
- term:
id: GO:0006886
label: intracellular protein transport
evidence_type: IEA
original_reference_id: GO_REF:0000002
qualifier: involved_in
review:
summary: >-
This term was assigned via InterPro mapping from the Importin-beta_N
domain (IPR001494), which is shared across karyopherin-beta family
members including both importins and exportins. While karyopherin-beta
proteins are involved in nucleocytoplasmic transport, Exportin-5
specifically transports RNA, not protein cargo. The term
"intracellular protein transport" is misleading for an RNA export
receptor.
action: MODIFY
reason: >-
The annotation confounds the transport of the receptor itself (which
shuttles as a protein) with the cargo it carries. Exportin-5 transports
RNA cargo, not protein cargo. A more accurate process term would reflect
RNA transport.
proposed_replacement_terms:
- id: GO:0006405
label: RNA export from nucleus
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "most evidence-based prediction is transporter function for structured RNAs, not small molecules"
- term:
id: GO:0031267
label: small GTPase binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
qualifier: enables
review:
summary: >-
Exportin-5, like all karyopherin-beta transport receptors, binds
RanGTPase (a small GTPase) as a central part of the transport
mechanism. Ran-GTP binding in the nucleus promotes cargo loading, and
GTP hydrolysis in the cytoplasm triggers cargo release. This annotation
is derived from the Importin-beta_N domain (IPR001494) via InterPro
mapping and correctly reflects the Ran-binding capability of all
karyopherin-beta proteins.
action: ACCEPT
reason: >-
Small GTPase (Ran) binding is a mechanistically essential function of
all karyopherin-beta transport receptors, including Exportin-5. The
annotation is correct, though a more specific term like
"Ran GTPase binding" (GO:0005099) would be more informative if available
in the annotation pipelines.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "Exportins bind cargo cooperatively with RanGTP in the nucleus to form a trimeric export complex"
- term:
id: GO:0042565
label: RNA nuclear export complex
evidence_type: IEA
original_reference_id: GO_REF:0000118
qualifier: part_of
review:
summary: >-
Exportin-5 forms a trimeric RNA nuclear export complex with its RNA cargo
and RanGTP. The complex assembles in the nucleus and traverses the nuclear
pore complex for cytoplasmic cargo delivery. Membership in this complex
is consistent with the known biology of Exportin-5 proteins.
action: ACCEPT
reason: >-
The RNA nuclear export complex is the functional assembly through which
Exportin-5 performs its transport activity, supported by extensive
biochemical and structural evidence from the exportin-5 literature.
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "Exportin-5 binds cargo in cooperation with RanGTP, forming a trimeric export complex"
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings:
- statement: >-
InterPro maps the Importin-beta_N domain (IPR001494) to small GTPase
binding and intracellular protein transport. The GTPase binding annotation
is appropriate for karyopherin-beta family members, but intracellular
protein transport is misleading for an RNA export receptor.
- id: GO_REF:0000118
title: TreeGrafter-generated GO annotations
findings:
- statement: >-
TreeGrafter correctly identifies this protein as an RNA-binding nuclear
transport receptor localized to nucleus, cytoplasm, and the RNA nuclear
export complex, consistent with Exportin-5 biology.
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings:
- statement: >-
Combined IEA methods assign nuclear export signal receptor activity and
protein export from nucleus, both of which are CRM1/Exportin-1 functions
rather than Exportin-5 functions. These annotations appear to arise from
the shared XPO1/5 InterPro superfamily classification.
- id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
title: Deep research summary for B4MAQ2
findings:
- statement: >-
Identifies B4MAQ2 as an Exportin-5-like protein based on domain architecture
and family classification, with predicted function in RanGTP-dependent nuclear
export of structured RNAs.
- statement: >-
Notes that in Drosophila, Exportin-5 compensates for the absence of canonical
Exportin-t, serving as the major tRNA export factor.
- statement: >-
No gene-specific literature exists for Dvir\GJ15622; function is inferred
entirely from conserved family and domain assignments.
- id: file:DROVI/B4MAQ2/B4MAQ2-uniprot.txt
title: UniProt entry B4MAQ2
findings:
- statement: >-
UniProt classifies the protein in the exportin family with Importin-beta_N,
Exportin-1/Importin-b-like, and Exportin-5_C domains.
- statement: >-
PANTHER subfamily assignment is EXPORTIN-5 (PTHR11223:SF3), distinguishing
it from EXPORTIN-1/CRM1.
core_functions:
- description: >-
RanGTP-dependent nuclear export receptor for structured RNAs. Exportin-5
binds pre-miRNAs, pre-tRNAs, and other minihelix-containing RNAs in the
nucleus cooperatively with RanGTP, traverses the nuclear pore complex,
and releases cargo in the cytoplasm upon GTP hydrolysis. In Drosophila,
Exportin-5 is the primary tRNA export factor in addition to its role in
miRNA biogenesis.
molecular_function:
id: GO:0003723
label: RNA binding
directly_involved_in:
- id: GO:0006405
label: RNA export from nucleus
locations:
- id: GO:0005634
label: nucleus
- id: GO:0005737
label: cytoplasm
in_complex:
id: GO:0042565
label: RNA nuclear export complex
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "RanGTP-dependent export receptor; directly binds dsRNA/minihelix cargoes in a sequence-independent but structure-dependent manner"
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "In flies, Exp5 is a major RNA export receptor and can compensate for missing canonical Exportin-t functions in tRNA export"
- description: >-
Binds the small GTPase Ran in its GTP-bound form as part of the nuclear
export transport cycle. RanGTP binding is required for cargo loading in
the nucleus and is mechanistically essential for the directionality of
transport through the nuclear pore complex.
molecular_function:
id: GO:0031267
label: small GTPase binding
directly_involved_in:
- id: GO:0006405
label: RNA export from nucleus
locations:
- id: GO:0005634
label: nucleus
supported_by:
- reference_id: file:DROVI/B4MAQ2/B4MAQ2-deep-research-falcon.md
supporting_text: "Exportins bind cargo cooperatively with RanGTP in the nucleus to form a trimeric export complex"
suggested_questions:
- question: >-
Is Dvir\GJ15622 the sole Exportin-5 ortholog in D. virilis, and does it
fully compensate for the lack of Exportin-t as shown for D. melanogaster
Exportin-5?
- question: >-
Does this protein have any protein cargo in addition to structured RNA
substrates, or is its function entirely restricted to RNA export?
suggested_experiments:
- hypothesis: >-
B4MAQ2 functions as a nuclear export receptor for pre-miRNAs and
pre-tRNAs in D. virilis cells.
description: >-
Perform PAR-CLIP or eCLIP in D. virilis cells to identify the RNA
substrates bound by B4MAQ2 in vivo, followed by subcellular fractionation
to confirm nucleocytoplasmic shuttling. Compare the RNA cargo profile
to that reported for D. melanogaster Exportin-5.
experiment_type: PAR-CLIP/eCLIP with subcellular fractionation
- hypothesis: >-
B4MAQ2 binds RanGTP and forms a trimeric export complex with structured
RNA cargo.
description: >-
Express and purify recombinant B4MAQ2 and test RanGTP-dependent binding
to pre-miRNA and tRNA substrates in vitro using electrophoretic mobility
shift assays or fluorescence anisotropy.
experiment_type: In vitro binding assay (EMSA/fluorescence anisotropy)