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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-5’s 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-β export receptors) | Members of the karyopherin-β superfamily; built from tandem α-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 α-helical solenoid described as a “baseball mitt-like” structure; Importin-β-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 α-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-β-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 3′ 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 3′ 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 nucleus–NPC–cytoplasm 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, Görlich 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 5′- and 3′-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
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(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 GÖRLICH. 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 5′- and 3′-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 GÖRLICH. 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 GÖRLICH. 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.