Affinage

NXT2

NTF2-related export protein 2 · UniProt Q9NPJ8

Round 2 corrected
Length
142 aa
Mass
16.2 kDa
Annotated
2026-04-29
42 papers in source corpus 6 papers cited in narrative 6 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

NXT2 (NTF2-related export protein 2) is an NTF2-like cofactor of the NXF family of nuclear mRNA export receptors, functioning redundantly with its paralog NXT1 to stabilize NXF1 and sustain bulk mRNA nuclear export (PMID:33883167). Through its NTF2-like domain, NXT2 directly binds NXF1, the testis-specific paralogs NXF2 and NXF3, and nuclear pore complex components NUP93 and NUP214 (PMID:11073998, PMID:40624043). Loss-of-function variants in human NXT2 cause germ cell aplasia and male infertility, establishing it as essential for fetal or early germ cell development in humans, whereas single Nxt2 knockout in mice is dispensable for spermatogenesis due to functional compensation by Nxt1 (PMID:40624043, PMID:29563520). In zebrafish, NXT2 disruption causes defective myocardial cell differentiation and cardiac valve malformation, indicating a conserved developmental role beyond germ cells (PMID:15790397).

Mechanistic history

Synthesis pass · year-by-year structured walk · 5 steps
  1. 2000 Medium

    Identification of NXT2 as a second NTF2-like export factor in humans resolved whether the NXF1 cofactor p15/NXT1 was unique, revealing that NXT2 binds the full NXF family (NXF1, NXF2, NXF3) and placing it in the nuclear mRNA export pathway.

    Evidence Database homology searches and co-affinity purification/binding assays in human cells

    PMID:11073998

    Open questions at the time
    • Binding shown by pulldown assays without reciprocal validation or domain mapping
    • No functional (export) assay demonstrating NXT2 is required for mRNA transport
    • Relationship to the paralog NXT1 in vivo not addressed
  2. 2005 Medium

    Demonstrating that NXT2 disruption in zebrafish causes embryonic cardiac defects established a developmental role beyond generic mRNA export, showing that NXT2 is required for myocardial differentiation and cardiac valve morphogenesis.

    Evidence Retroviral insertion mutagenesis and morpholino knockdown in zebrafish embryos with whole-mount in situ hybridization

    PMID:15790397

    Open questions at the time
    • Mechanism linking mRNA export to cardiac differentiation not determined
    • No identification of specific cardiac transcripts requiring NXT2 for export
    • Single model organism; not validated in mammalian cardiac development
  3. 2018 Medium

    CRISPR knockout of Nxt2 in mice yielded fully fertile males with normal spermatogenesis, establishing that Nxt2 is individually dispensable in mice and implying functional redundancy with Nxt1.

    Evidence CRISPR/Cas9 knockout in mice with histological analysis and sperm counts

    PMID:29563520

    Open questions at the time
    • Double knockout with Nxt1 not performed
    • Species-specific compensation could mask essential functions present in primates
    • Female fertility and non-reproductive phenotypes not systematically examined
  4. 2021 High

    Discovery that NXT1 and NXT2 are synthetic lethal — NXF1 protein is destabilized only when both are absent — defined the mechanistic basis for their redundancy and revealed NXT2 as a vulnerability axis in NXT1-deleted cancers.

    Evidence shRNA knockdown, CRISPR screens, co-immunoprecipitation, quantitative proteomics, and in vivo xenograft models

    PMID:33883167

    Open questions at the time
    • Structural basis for how NXT1/NXT2 binding stabilizes NXF1 not resolved
    • Whether NXT2 has NXF1-independent functions remains untested
    • Tissue-specific differences in NXT1 vs NXT2 expression driving differential dependency not mapped
  5. 2025 High

    Mapping NXT2's in vivo interactome in human testis and linking human loss-of-function variants to germ cell aplasia resolved the species discrepancy with the mouse knockout, demonstrating that NXT2 is essential for human fetal/early germ cell development and interacts with NXF2, NXF3, NUP93, and NUP214 via its NTF2-like domain.

    Evidence Co-immunoprecipitation from human testis, domain mutagenesis, identification of loss-of-function variants in infertile men, testicular histology

    PMID:40624043

    Open questions at the time
    • Specific mRNA cargo dependent on NXT2–NXF2/NXF3 complexes in germ cells not identified
    • Rescue experiments with NXT2 re-expression in human germ cells not performed
    • Whether NXT2 has a direct role at the nuclear pore versus indirect stabilization of NXF complexes is unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • The identity of specific mRNA transcripts whose export depends on NXT2 (as opposed to NXT1), the structural basis of NXT2-mediated NXF1 stabilization, and the mechanism linking NXT2 loss to germ cell aplasia at the fetal stage remain open questions.
  • No transcriptome-wide identification of NXT2-dependent export substrates
  • No crystal or cryo-EM structure of the NXT2–NXF1 or NXT2–NXF2 complex
  • Mechanism of germ cell loss (apoptosis, failure to proliferate, failure to migrate) not characterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 3
Localization
GO:0005634 nucleus 2
Pathway
R-HSA-8953854 Metabolism of RNA 3 R-HSA-9609507 Protein localization 3 GO:0005634 nucleus 2 R-HSA-1266738 Developmental Biology 1
Partners
NUP214NUP93NXF1NXF2NXF3NXT1

Evidence

Reading pass · 6 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 NXT2 (p15-2) was identified as a paralog of NXT1 (p15) encoded in the human genome. Both human p15 homologues (NXT1 and NXT2) bind TAP (NXF1), NXF2, and NXF3, indicating that NXT2 is a component of the nuclear mRNA export pathway with broad binding to the NXF family. Database searches, co-affinity purification / binding assays Molecular and cellular biology Medium 11073998
2005 Disruption of NXT2 in zebrafish causes specific embryonic heart defects, including deficient myocardial cell differentiation and malformation of the cardiac valve at the atrioventricular boundary. Loss of one alternatively spliced NXT2 mRNA isoform was responsible. Knockdown with morpholino antisense oligonucleotides reproduced the phenotype, establishing a critical role for NXT2 in maintaining morphogenetic integrity of the embryonic vertebrate heart. Retroviral insertion mutagenesis, whole-mount RNA in situ hybridization, morpholino antisense knockdown BMC developmental biology Medium 15790397
2018 CRISPR/Cas9 knockout of Nxt2 in mice results in fully fertile males with no detectable difference in testis/body weight ratios, epididymal sperm counts, or testicular/epididymal histology compared with wild-type, demonstrating that Nxt2 is individually dispensable for spermatogenesis and male fertility in mice under laboratory conditions. CRISPR/Cas9 knockout, histological analysis, sperm count Scientific reports Medium 29563520
2021 NXT1 and NXT2 exhibit a synthetic lethal relationship with respect to their shared essential binding partner NXF1: NXF1 protein is destabilized and lost only when both NXT1 and NXT2 are absent, not when either is lost alone. This demonstrates that NXT2 functionally compensates for NXT1 in stabilizing NXF1 and sustaining mRNA nuclear export. shRNA knockdown, CRISPR screens, co-immunoprecipitation, quantitative proteomics, in vivo xenograft models Cancer discovery High 33883167
2022 Adaptive (positive) selection has frequently contributed to genetic changes in primate NXT2, whereas murine NXT2 has evolved under conservative (purifying) constraints — a genetic divergence suggesting NXT2 may have acquired distinct functional implementations between primates and murine rodents. Phylogenetic analysis, molecular evolution analysis (dN/dS ratios) Zoology (Jena, Germany) Low 35219094
2025 In the human testis, NXT2 interacts in vivo with NXF1, the testis-specific NXF1 paralogs NXF2 and NXF3, and nuclear pore complex proteins NUP93 and NUP214. The NTF2-like domain of NXT2 mediates its binding to NXF2 and NXF3. Loss-of-function variants in NXT2 in infertile men cause near-complete absence of germ cells, indicating NXT2 is critical for fetal or early germ cell development, while loss of NXF3 affects later spermatogenic stages. Co-immunoprecipitation (in vivo interaction), domain mutagenesis, identification of human loss-of-function variants, testicular histology Nature communications High 40624043

Source papers

Stage 0 corpus · 42 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Towards a proteome-scale map of the human protein-protein interaction network. Nature 2090 16189514
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2005 The DNA sequence of the human X chromosome. Nature 816 15772651
2003 Complete sequencing and characterization of 21,243 full-length human cDNAs. Nature genetics 754 14702039
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2022 OpenCell: Endogenous tagging for the cartography of human cellular organization. Science (New York, N.Y.) 432 35271311
2005 Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes. Genome research 409 16344560
2011 Next-generation sequencing to generate interactome datasets. Nature methods 200 21516116
2013 The protein interaction landscape of the human CMGC kinase group. Cell reports 174 23602568
2000 TAP (NXF1) belongs to a multigene family of putative RNA export factors with a conserved modular architecture. Molecular and cellular biology 173 11073998
2000 Cloning and functional analysis of cDNAs with open reading frames for 300 previously undefined genes expressed in CD34+ hematopoietic stem/progenitor cells. Genome research 161 11042152
2009 Ubiquitin-mediated proteolysis of HuR by heat shock. The EMBO journal 142 19322201
2011 Interactions of pathological hallmark proteins: tubulin polymerization promoting protein/p25, beta-amyloid, and alpha-synuclein. The Journal of biological chemistry 131 21832049
2020 Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins and Uncovers Widespread Protein Aggregation in Affected Brains. Cell reports 79 32814053
2013 A negative genetic interaction map in isogenic cancer cell lines reveals cancer cell vulnerabilities. Molecular systems biology 76 24104479
2015 Phospho-tyrosine dependent protein-protein interaction network. Molecular systems biology 61 25814554
2019 Extensive disruption of protein interactions by genetic variants across the allele frequency spectrum in human populations. Nature communications 60 31515488
1991 Blepharophimosis sequence and de novo balanced autosomal translocation [46,XY,t(3;4)(q23;p15.2)]: possible assignment of the trait to 3q23. American journal of medical genetics 48 1746616
2018 The evolutionarily conserved genes: Tex37, Ccdc73, Prss55 and Nxt2 are dispensable for fertility in mice. Scientific reports 41 29563520
2005 NXT2 is required for embryonic heart development in zebrafish. BMC developmental biology 39 15790397
1994 Genomic organization, nucleotide sequence, biophysical properties, and localization of the voltage-gated K+ channel gene KCNA4/Kv1.4 to mouse chromosome 2/human 11p14 and mapping of KCNC1/Kv3.1 to mouse 7/human 11p14.3-p15.2 and KCNA1/Kv1.1 to human 12p13. Genomics 36 8020965
2021 Selective Modulation of a Pan-Essential Protein as a Therapeutic Strategy in Cancer. Cancer discovery 30 33883167
1999 Closing in on the BPES gene on 3q23: mapping of a de Novo reciprocal translocation t(3;4)(q23;p15.2) breakpoint within a 45-kb cosmid and mapping of three candidate genes, RBP1, RBP2, and beta'-COP, distal to the breakpoint. Genomics 27 10191085
2000 Identification of BPESC1, a novel gene disrupted by a balanced chromosomal translocation, t(3;4)(q23;p15.2), in a patient with BPES. Genomics 23 10995571
2022 HDLBP Promotes Hepatocellular Carcinoma Proliferation and Sorafenib Resistance by Suppressing Trim71-dependent RAF1 Degradation. Cellular and molecular gastroenterology and hepatology 19 36244648
2019 Integrated analysis of the critical region 5p15.3-p15.2 associated with cri-du-chat syndrome. Genetics and molecular biology 19 30985858
1986 De novo del(7)(pter----p21.2::p15.2----qter) and craniosynostosis. Implications for critical segment assignment in the 7p2 monosomy syndrome. Annales de genetique 19 3487273
1990 Anophthalmia in a retarded girl with partial trisomy 4p and 22 following a maternal translocation, rcp(4;22)(p15.2;q11.2). Ophthalmic paediatrics and genetics 8 2377354
2009 Case report: Meiotic segregation in spermatozoa of a 46,X,t(Y;10)(q11.2;p15.2) fertile translocation carrier. Reproductive biomedicine online 6 19400998
2000 Localization of the human SP3 gene to chromosome 7p14-p15.2. The lack of expression in multiple sclerosis does not reflect abnormal gene organization. Journal of neuroimmunology 6 10814800
1996 A new case of Beckwith-Wiedemann syndrome with an 11p15 duplication of paternal origin [46,XY,-21,+der(21), t(11;21)(p15.2;q22.3)pat]. Acta geneticae medicae et gemellologiae 5 8872040
2011 Turner Syndrome with Isochromosome Xq and Familial Reciprocal Translocation t(4;16)(p15.2;p13.1). Balkan journal of medical genetics : BJMG 3 24052704
2017 Interstitial deletion 5p14.1-p15.2 and 5q14.3-q23.2 in a patient with clubfoot, blepharophimosis, arthrogryposis, and multiple congenital abnormalities. American journal of medical genetics. Part A 2 28815864
2022 Genetic characterization of nuclear export factor NXT1 and its paralog NXT2 in primates and murine rodents. Zoology (Jena, Germany) 1 35219094
1999 Cri du chat and Turner syndrome features in a newborn girl with an unbalanced 45,X,psu dic(5;X)(p15.2;p22.1) karyotype: FISH and replication banding studies. Annales de genetique 1 10434125
2025 NXT2 is a key component of the RNA nuclear export factor complex in the human testis and essential for spermatogenesis. Nature communications 0 40624043