NUP35

NUP35 is a structural nucleoporin that scaffolds nuclear pore complex (NPC) assembly and supports selective nucleocytoplasmic transport (PMID:19146848, PMID:24363447). Its RRM domain adopts an atypical fold with non-canonical RNP1/RNP2 motifs and drives homodimerization through a beta-sheet hydrophobic interface centered on Met236 packed against Phe178 and Trp209 (PMID:16962612), and the protein is present at roughly 23 copies per pore (PMID:27613095). During NPC biogenesis NUP35 (Nup53/NPP-19 in orthologs) is specifically required to recruit Nup155 to the assembling pore — its interaction with Nup155 being the principal recruitment determinant — while its binding to the integral pore membrane protein Ndc1 overlaps with a membrane-bending region that modulates membrane deformation; loss of NUP35 blocks NPC assembly, lamina formation, and transport without affecting initial nuclear membrane targeting (PMID:19146848, PMID:24363447). NUP35 contains FG repeats and facilitates Ran-dependent translocation of inner nuclear membrane proteins through NPC peripheral channels via FG–FG interactions (PMID:21444689, PMID:22046461). Beyond structural roles, NUP35 acts as an mRNA export factor: its N-terminal domain directs nuclear export of nhe1 mRNA in cardiomyocytes by targeting its 5'-UTR (PMID:26260029), and it directly binds Wif1 mRNA, so that NUP35 deficiency causes nuclear retention of Wif1, activation of Wnt signaling, and pathological cardiac fibrosis and hypertrophy that is rescued by AAV9-delivered Wif1 mRNA (PMID:41145234). NUP35 additionally localizes to the meiotic spindle and microtubules in oocytes, where it is required for spindle assembly and chromosome alignment (PMID:30195030). It is exploited by HIV-1, whose capsid contacts NUP35 via FG-motif regions to support viral nuclear entry (PMID:37355754), and its UBA1-mediated ubiquitination and proteasomal degradation in macrophages impairs IκBα nuclear import to activate NF-κB inflammatory signaling (PMID:42049653). A point mutation in the NUP35 RRM domain causes a colonic smooth-muscle degenerative myopathy and megacolon in mice (PMID:27427419).

1. 2006 High

   Establishing the structural basis of NUP35 oligomerization showed how this nucleoporin builds higher-order assemblies, defining its RRM as a dimerization module rather than a conventional RNA-binding fold.

   Evidence X-ray crystallography of mouse Nup35 RRM with analytical ultracentrifugation

   PMID:16962612

   Open questions at the time

   • Does not address whether the RRM also binds RNA in vivo
   • No structure of full-length protein or RRM in context of the NPC scaffold
2. 2008 High

   In vivo loss-of-function placed NUP35 at a specific step of NPC biogenesis — required for Nup155 recruitment and pore assembly but dispensable for initial membrane-to-chromatin targeting — resolving where in the assembly hierarchy it acts.

   Evidence C. elegans npp-19 loss-of-function mutant with fluorescence imaging of NPC/NE markers and transport assays

   PMID:19146848

   Open questions at the time

   • Molecular detail of the Nup35-Nup155 interaction not defined here
   • Did not test mRNA export functions
3. 2011 High

   FRAP-based dissection revealed a transport function distinct from scaffolding: NUP35 mediates Ran-dependent translocation of inner nuclear membrane proteins through NPC peripheral channels via its FG repeats.

   Evidence FRAP after siRNA depletion with Ran/ATP depletion and FG-repeat addition constructs; companion perspective reinforcing FG-FG mechanism

   PMID:21444689 PMID:22046461

   Open questions at the time

   • Direct FG-FG contacts not structurally resolved
   • Full set of membrane-protein cargoes not enumerated
4. 2013 High

   Reciprocal interaction mapping defined the molecular interfaces — Nup53/Nup35 binding Ndc1 and Nup155 — and linked the Ndc1-binding site to membrane-bending activity, mechanistically explaining how it couples membrane deformation to pore assembly.

   Evidence Co-IP, interaction mapping, in vitro membrane-bending assay, and siRNA depletion microscopy

   PMID:24363447

   Open questions at the time

   • Structural basis of membrane bending not solved
   • Regulation of the Ndc1/Nup155 binding switch unknown
5. 2015 Medium

   Identification of nhe1 mRNA export control assigned NUP35 a selective mRNA-trafficking function with physiological consequence, showing its N-terminal domain targets a defined 5'-UTR region.

   Evidence siRNA knockdown, mRNA nuclear export assay, domain-deletion mapping, and ischemia/pH-challenge models

   PMID:26260029

   Open questions at the time

   • Whether export selectivity is direct RNA binding or indirect not resolved here
   • Single laboratory; export machinery partners unidentified
6. 2016 Medium

   An RRM point-mutation mouse tied NUP35 function to a tissue-specific disease, localizing the pathology to colonic smooth muscle and implicating RRM integrity in that cell type.

   Evidence ENU-induced point-mutation mouse model with histopathology and immunohistochemistry

   PMID:27427419

   Open questions at the time

   • No molecular mechanism linking RRM mutation to smooth-muscle defect
   • Tissue specificity unexplained
7. 2016 Medium

   Quantitative imaging fixed the stoichiometry of NUP35 at the pore (~23 copies), constraining models of its scaffolding role.

   Evidence Single-molecule GFP fluorescence calibration with knockdown/replacement in living cells

   PMID:27613095

   Open questions at the time

   • Single method/lab
   • Spatial arrangement of copies within the pore not determined
8. 2018 Medium

   Discovery of meiotic spindle/microtubule localization extended NUP35 function beyond the interphase NPC, implicating it in spindle assembly and chromosome alignment in oocytes.

   Evidence Immunofluorescence, siRNA knockdown, SAC and kinetochore-microtubule attachment analyses in mouse oocytes

   PMID:30195030

   Open questions at the time

   • Direct microtubule-binding interface not defined
   • Role of putative post-GVBD phosphorylation unconfirmed
9. 2022 Medium

   Acute degron depletion distinguished NUP35 from transcription-regulating nucleoporins, showing it does not directly control gene transcription, RNA Pol II loading, or BRD4 recruitment.

   Evidence Auxin-inducible degron depletion with Cut&Run and in situ Hi-C

   PMID:36323253

   Open questions at the time

   • Does not exclude indirect transcriptional effects via mRNA export
   • Single cell system
10. 2023 Medium

    Demonstrating direct HIV-1 capsid contact via NUP35 FG-motif regions identified the protein as a host factor for viral nuclear entry, gated by capsid-cyclophilin A interaction.

    Evidence Nup35 knockdown, HIV-1 nuclear entry assays, capsid mutant analysis, and direct binding assay

    PMID:37355754

    Open questions at the time

    • Structural detail of CA-NUP35 interface unresolved
    • Single study
11. 2025 High

    RIP-seq plus in vivo KO/OE with rescue established NUP35 as a direct Wif1 mRNA export factor whose loss activates Wnt signaling and drives cardiac fibrosis, providing a causal mRNA-to-disease axis.

    Evidence Cardiac-specific KO/OE mice, RIP-seq, AAV9 Wif1 mRNA rescue, and angiotensin II/TAC stress models

    PMID:41145234

    Open questions at the time

    • Whether RRM directly contacts Wif1 mRNA not structurally shown
    • Generality of mRNA-target selection rules unknown
12. 2026 High

    Identifying UBA1-driven ubiquitination and degradation of NUP35 connected its turnover to inflammatory signaling, showing NUP35 loss impairs IκBα nuclear import to activate NF-κB in macrophages.

    Evidence Myeloid-specific Uba1 KO mice, sepsis (CLP) model, ubiquitinome/proteomics, IκBα nuclear import assay, and pharmacologic inhibition

    PMID:42049653

    Open questions at the time

    • Direct E3 ligase mediating NUP35 ubiquitination not identified
    • Mechanism by which NUP35 supports IκBα import not structurally defined

• How NUP35 selects specific mRNA cargoes (nhe1, Wif1) and whether its RRM directly binds these transcripts versus acting through partner export factors remains unresolved.
• No structure of NUP35 bound to RNA
• Export-machinery partners for selective mRNA trafficking unidentified
• Reconciliation of structural nucleoporin role with mRNA-export and spindle roles incomplete