NUFIP2

NUFIP2 is an RNA-binding protein that functions as a direct high-affinity cofactor of the Roquin-1/2 post-transcriptional regulators, cooperatively recognizing non-canonical stem-loop structures in target mRNA 3′-UTRs (including ICOS and Ox40) to promote mRNA decay (PMID:29352114). Independent UV-crosslinking and oligo(dT) capture studies confirmed NUFIP2 as a bona fide mRNA-binding protein, and it associates with pre-miRNA substrates and stress granule/processing body components (PMID:22658674, PMID:22681889, PMID:28431233). NUFIP2 protein stability depends on ATXN2L, and in neurodegenerative disease contexts NUFIP2 accumulates in pathological aggregates—homodimerizing in SCA2 spinal cord tissue with polyQ-expanded ATXN2 and co-localizing with cytoplasmic TDP-43 inclusions in ALS/FTLD patient tissue (PMID:40220918).

1. 2012 Medium

   Whether NUFIP2 directly contacts mRNA was unknown; two independent interactome capture studies using UV crosslinking in HeLa and HEK293 cells established NUFIP2 as a bona fide mRNA-binding protein, opening the question of which mRNAs and pathways it regulates.

   Evidence UV crosslinking/oligo(dT) capture (HeLa) and PAR-CLIP/oligo(dT) capture (HEK293) with quantitative mass spectrometry

   PMID:22658674 PMID:22681889

   Open questions at the time

   • Specific mRNA targets not identified
   • Functional consequence of mRNA binding not tested
   • RNA-binding domain(s) of NUFIP2 not mapped
2. 2017 Medium

   NUFIP2's interaction with pre-miRNA substrates was discovered through proteomics pull-downs, extending its RNA-binding repertoire beyond mRNA to miRNA precursors, though its functional role in miRNA biogenesis was not resolved.

   Evidence Proteomics-based pull-down with multiple pre-miRNA baits followed by mass spectrometry

   PMID:28431233

   Open questions at the time

   • No direct evidence that NUFIP2 regulates miRNA processing or maturation
   • Whether pre-miRNA binding is independent of or related to Roquin pathway unknown
3. 2018 High

   The central mechanistic question—how NUFIP2 participates in post-transcriptional regulation—was answered by showing it is a direct, high-affinity cofactor of Roquin-1/2 that is required for Roquin-mediated mRNA decay and cooperatively binds non-canonical stem-loop elements in 3′-UTRs of immune-regulatory transcripts.

   Evidence RNAi screen of ~1500 genes, co-immunoprecipitation, direct binding/EMSA, and 3′-UTR reporter decay assays in human and murine cells

   PMID:29352114

   Open questions at the time

   • Structural basis of the NUFIP2–Roquin interface not determined
   • Full transcriptome-wide repertoire of NUFIP2-dependent Roquin targets not mapped
   • Whether NUFIP2 has Roquin-independent mRNA-regulatory functions remains untested
4. 2025 Medium

   The question of what stabilizes NUFIP2 protein was resolved by identifying ATXN2L as its primary physical interactor whose loss depletes NUFIP2; furthermore, NUFIP2 homodimers accumulate in spinal cord aggregates in a SCA2 mouse model, linking NUFIP2 to polyglutamine neurodegeneration.

   Evidence Co-immunoprecipitation in wild-type and ATXN2L-null murine embryonic fibroblasts, proteome profiling, SCA2 Atxn2-CAG100 knock-in mouse tissue analysis

   PMID:40220918

   Open questions at the time

   • Mechanism by which ATXN2L stabilizes NUFIP2 (direct protection vs. transcriptional) not dissected
   • Whether NUFIP2 aggregation is a driver or bystander in SCA2 pathology unclear
   • Relationship between ATXN2L–NUFIP2 axis and Roquin-mediated mRNA decay not tested
5. 2025 Medium

   NUFIP2 was shown to interact with cytoplasmically mislocalized TDP-43, sequestering it into aggregates and co-localizing with TDP-43 pathology in ALS/FTLD patient tissue, establishing a disease-relevant gain-of-function interaction.

   Evidence APEX2 proximity labeling, RNAi functional screen, immunofluorescence in patient tissue (preprint)

   Open questions at the time

   • Preprint not yet peer-reviewed
   • Whether NUFIP2 knockdown rescues TDP-43 aggregation in vivo not shown
   • Molecular determinants of the NUFIP2–TDP-43 interaction not mapped

• Major open questions include whether NUFIP2 possesses Roquin-independent mRNA-regulatory activities, the structural basis of its interactions with Roquin and ATXN2L, and whether its aggregation in SCA2 and ALS/FTLD is pathogenic or a secondary consequence of broader RNA granule dysregulation.
• No genome-wide map of NUFIP2 direct RNA targets (e.g., CLIP-seq)
• No high-resolution structure of NUFIP2 or its complexes
• Causal role in neurodegeneration not established by genetic rescue or knockout models