{"gene":"U2AF1","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":1999,"finding":"U2AF35 (U2AF1) directly contacts the 3' splice site AG dinucleotide early during spliceosome assembly, demonstrated by site-specific UV crosslinking. Mutational analysis and in vitro genetic selection showed U2AF35 has sequence-specific RNA-binding activity recognizing the 3'-splice-site consensus AG/G. For introns with weak polypyrimidine tracts, this U2AF35-3'-splice-site interaction is critical for U2AF binding and splicing.","method":"Site-specific UV crosslinking, mutational analysis, in vitro genetic selection, splicing assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis, crosslinking, and genetic selection; independently replicated by concurrent Nature paper (PMID:10617208)","pmids":["10617206"],"is_preprint":false},{"year":1999,"finding":"U2AF35 contacts the AG dinucleotide at the 3' splice site only when located in proximity to the polypyrimidine tract (shown by UV crosslinking). This interaction stabilizes U2AF65 binding, such that Sex-lethal (SXL) can no longer displace U2AF65 from the polypyrimidine tract. SXL-mediated splicing inhibition of msl-2 requires a combination of SXL binding at the polypyrimidine tract and an unusually long distance between the poly(Y) tract and the AG, which weakens U2AF35-AG interaction.","method":"UV crosslinking, in vitro splicing competition assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — UV crosslinking with functional splicing assays; replicates and extends concurrent Nature paper (PMID:10617206)","pmids":["10617208"],"is_preprint":false},{"year":1996,"finding":"U2AF35 is required for constitutive splicing and functions as a mediator of enhancer-dependent splicing. Nuclear extracts deficient in U2AF35 are inactive; both constitutive and enhancer-dependent splicing are restored by recombinant U2AF35. In vitro protein-RNA interaction studies showed U2AF35 directly mediates interactions between U2AF65 and proteins bound to splicing enhancers, acting as a bridge to recruit U2AF65 to weak 3' splice sites.","method":"Nuclear extract depletion/complementation, in vitro splicing assays, protein-RNA interaction studies","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution of splicing activity with purified recombinant U2AF35, multiple orthogonal assays","pmids":["8647433"],"is_preprint":false},{"year":2001,"finding":"X-ray crystal structure of the human core U2AF heterodimer (U2AF35 central domain + proline-rich region of U2AF65) at 2.2 Å resolution revealed a novel 'tongue-in-groove' protein-protein interaction via reciprocal tryptophan residues between an atypical RRM of U2AF35 and U2AF65 polyproline segment. Biochemical experiments showed the core heterodimer binds RNA and that the interacting tryptophan side chains are essential for U2AF dimerization.","method":"X-ray crystallography (2.2 Å), site-directed mutagenesis, RNA-binding biochemical assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis and biochemical validation in single study","pmids":["11551507"],"is_preprint":false},{"year":2001,"finding":"U2AF35 has a dual function in AG-dependent pre-mRNA splicing: (1) its interaction with the consensus 3' splice site AG stabilizes U2AF65 binding to weak polypyrimidine tracts, and (2) U2AF35 triggers additional downstream events in spliceosome assembly beyond U2AF65 stabilization. RS domain-mediated interactions with SR proteins bound to exonic splicing enhancers are dispensable for U2AF35 activity; a truncation mutant lacking the RS domain but retaining the pseudo-RRM is active in complementation assays.","method":"Nuclear extract depletion/complementation, UV crosslinking, in vitro splicing assays, truncation mutant analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with mutants and multiple orthogonal methods in single study","pmids":["11604503"],"is_preprint":false},{"year":1999,"finding":"U2AF35 has a substrate-specific requirement: recombinant U2AF65 alone is sufficient for splicing of two constitutively spliced pre-mRNAs in U2AF-depleted extracts, but both U2AF65 and U2AF35 (and their interaction) are required for splicing of an immunoglobulin µ pre-mRNA with a weak polypyrimidine tract and purine-rich exonic splicing enhancer. U2AF35 splicing activation occurs without changes in U2AF65 crosslinking to the polypyrimidine tract.","method":"Chromatographic depletion of U2AF, in vitro splicing complementation, UV crosslinking","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with recombinant proteins, multiple substrates tested, crosslinking controls","pmids":["10567551"],"is_preprint":false},{"year":2001,"finding":"Splicing activators (SR proteins on enhancers) promote binding of both U2AF65 and U2AF35 to weak 3' splice sites under splicing conditions, and U2AF35 is required for maximum levels of activator-dependent splicing. Base substitutions converting weak 3' splice sites to consensus relieve the requirement for splicing activators by increasing U2AF binding directly.","method":"In vitro splicing assays, RNA-protein binding assays, mutational analysis of splice sites","journal":"RNA","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with multiple orthogonal methods confirming U2AF recruitment model","pmids":["11421359"],"is_preprint":false},{"year":2002,"finding":"The U2AF35 RRM is unstructured in isolation but its tertiary structure is induced upon binding to U2AF65. This induced folding is mediated specifically by the N-terminal proline-rich region of U2AF65 and does not involve the U2AF65 RRMs.","method":"Nuclear magnetic resonance (NMR) spectroscopy of free and complexed U2AF35 RRM","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structural characterization with domain-mapping experiments, single study","pmids":["12297299"],"is_preprint":false},{"year":2005,"finding":"Direct interaction between U2AF35 and U2AF65 was demonstrated in vivo in live cell nuclei by FRET microscopy. Additionally, a novel U2AF35 self-interaction was discovered both in vivo (by FRET) and confirmed in vitro by biochemical assays, suggesting the U2AF complex stoichiometry may differ from the expected heterodimer in vivo.","method":"FRET microscopy in live cells, biochemical in vitro binding assays","journal":"RNA","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — FRET in live cells plus biochemical confirmation, single lab with two orthogonal methods","pmids":["16043505"],"is_preprint":false},{"year":2008,"finding":"Splicing factor SPF30 bridges an interaction between U2AF35 (prespliceosome) and hPrp3 (tri-snRNP component). The N-terminal domain of SPF30 interacts with U2AF35, and the C-terminus of SPF30 interacts with hPrp3 simultaneously, potentially linking 3' splice site recognition to tri-snRNP addition.","method":"Co-immunoprecipitation, pulldown assays, domain mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal pulldowns with domain mapping, simultaneous interaction confirmed, single lab","pmids":["18211889"],"is_preprint":false},{"year":2011,"finding":"Missense mutations affecting Ser34 (S34F) in the zinc fingers of U2AF1 are recurrently found in MDS patients. Mutant U2AF1 promotes enhanced splicing and exon skipping in reporter assays in vitro, implicating altered pre-mRNA splicing as a mechanism for MDS pathogenesis.","method":"Whole-genome sequencing, reporter splicing assays in vitro","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Strong — discovery of mutation with functional reporter assay; widely replicated in subsequent studies","pmids":["22158538"],"is_preprint":false},{"year":2014,"finding":"U2AF1 mutations (S34F/Y and Q157R/P) alter the preferred 3' splice site motif in patients, in cell culture, and in vitro. S34F/Y mutations cause preferential recognition of CAG over UAG 3' splice site sequences. Mutations in the first and second zinc fingers give rise to different alterations in splice site preference and largely distinct downstream splicing programs.","method":"RNA-seq splice junction analysis, in vitro RNA-binding assays, cell culture expression system","journal":"Genome research","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro binding assays combined with transcriptome-wide RNA-seq in patients and cell culture; replicated across multiple contexts","pmids":["25267526"],"is_preprint":false},{"year":2014,"finding":"U2AF1 S34F mutation alters sequence specificity of RNA binding, decreasing affinity for uridine (relative to cytidine) at the -3 position immediately upstream of the splice acceptor site, leading to aberrant alternative splicing. U2AF1(S34F) co-localizes normally with U2AF2 within nuclear speckles (localization not disrupted by mutation).","method":"RNA-seq splice junction analysis, affinity-binding assays, immunofluorescence co-localization","journal":"Leukemia","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — affinity binding assay plus RNA-seq with validation in primary patient samples; single lab, two orthogonal methods","pmids":["25311244"],"is_preprint":false},{"year":2015,"finding":"Mutant U2AF1(S34F) expressed in hematopoietic progenitor cells in a doxycycline-inducible transgenic mouse model causes changes in pre-mRNA splicing genome-wide and alters hematopoiesis in vivo. Common mutant U2AF1-induced splicing alterations are enriched in RNA processing genes, ribosomal genes, and MDS/AML-associated genes.","method":"Doxycycline-inducible transgenic mouse model, whole transcriptome RNA-seq","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional model with genome-wide RNA-seq; replicated in human datasets","pmids":["25965570"],"is_preprint":false},{"year":2016,"finding":"U2AF1(S34F) mutation causes aberrant selection of a distal cleavage and polyadenylation (CP) site in ATG7 pre-mRNA (not altered splicing), producing a longer ATG7 mRNA that is translated inefficiently, leading to decreased ATG7 levels, autophagy defect, and cellular transformation. This mechanism was confirmed in MDS/AML patient samples harboring U2AF1(S34F).","method":"Deep sequencing of transformed cell lines, 3' RACE, quantitative RT-PCR, western blot, patient sample validation","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (sequencing, RACE, western blot) with patient sample validation; mechanistically novel finding","pmids":["27184077"],"is_preprint":false},{"year":2016,"finding":"S34F-associated changes in alternative splicing are proportional to the ratio of S34F:wild-type U2AF1 gene products, not to absolute levels of either factor. Preferential recognition of specific 3' splice sites in S34F-expressing cells is largely explained by differential in vitro RNA-binding affinities of mutant versus wild-type U2AF1. Wild-type U2AF1 is required for cell survival regardless of S34F allele status.","method":"Endogenous locus genetic modification, quantitative RNA-seq, in vitro RNA-binding assays, in vivo tumor xenograft","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — genetic allele manipulation plus in vitro binding assays with functional cellular phenotypes","pmids":["27776121"],"is_preprint":false},{"year":2019,"finding":"U2AF1 has a noncanonical function in translation regulation: it directly binds mature mRNA in the cytoplasm and negatively regulates mRNA translation. This splicing-independent role is altered by the S34F mutation; polysome profiling shows mutation affects translation of hundreds of mRNAs. One consequence is increased synthesis of secreted chemokine IL-8, contributing to metastasis and cancer progression.","method":"CLIP-seq (cytoplasmic), polysome profiling, quantitative proteomics, in vivo metastasis assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct RNA binding in cytoplasm demonstrated by CLIP, polysome profiling, functional in vivo consequence","pmids":["30842218"],"is_preprint":false},{"year":2019,"finding":"U2AF1 mutations induce expression of a longer IRAK4 isoform (IRAK4-L, retaining exon 4) that assembles with the myddosome and results in maximal NF-κB activation. IRAK4-L expression is mediated by mutant U2AF1, and inhibition of IRAK4-L abrogates leukemic growth in AML cells with high IRAK4-L expression.","method":"Exon usage analysis of patient RNA-seq, cell line functional assays, IRAK4 inhibitor experiments","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — patient RNA-seq corroborated by functional cell line assays with pharmacological inhibition; multiple independent AML/MDS datasets","pmids":["31011167"],"is_preprint":false},{"year":2019,"finding":"U2AF1 S34F preferentially binds and modulates splicing of introns containing CAG trinucleotides at their 3' splice junctions compared to wild-type. CLIP analysis showed a shift in cross-linking at 3' splice sites, significantly associated with alternative splicing of skipped exons. S34F also induces increased splicing of the long SLC34A2-ROS1 isoform, associated with enhanced tumor cell invasion.","method":"CLIP-seq, RNA-seq, functional invasion assays in cells with ROS1 translocation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — CLIP-seq providing direct binding evidence plus RNA-seq and functional assays; single lab, multiple orthogonal methods","pmids":["31836708"],"is_preprint":false},{"year":2020,"finding":"Crystal structures of wild-type and pathogenic mutant U2AF1 complexed with target RNA at the 3' splice site revealed the molecular mechanism of 3' splice site selection. The structures showed how S34F and Q157R mutations cause aberrant 3' splice site recognition by altering RNA contacts within the zinc finger domains.","method":"X-ray crystallography of WT and mutant U2AF1-RNA complexes","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of WT and two pathogenic mutants in complex with RNA, directly revealing mechanism","pmids":["32958768"],"is_preprint":false},{"year":2020,"finding":"U2AF1 subunit stabilizes a closed conformation of the U2AF2 (U2AF65) tandem RRMs in the absence of RNA (high FRET). Upon binding a strong uridine-rich splice site, U2AF2 switches to an open conformation. For weak uridine-poor polypyrimidine tracts, the heterodimer binds as a mixture of closed and open conformations, and the S34F mutation modulates this equilibrium. Structure-guided mutagenesis confirmed the conformational assignments.","method":"Single-molecule FRET, structure-guided mutagenesis","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-molecule FRET with mutagenesis validation; mechanistically rigorous single study","pmids":["32343311"],"is_preprint":false},{"year":2021,"finding":"U2AF1 S34F and Q157R mutants establish new RNA contacts at positions -3 and +1 nucleotides of the 3' splice site AG, respectively (revealed by single-nucleotide resolution CLIP). These new contacts compromise U2AF2-RNA interactions, resulting predominantly in intron retention and exon exclusion. Mutant U2AF1-expressing cell lines and patient-derived MDS/AML blasts display a heightened stress granule response.","method":"High-resolution CLIP at single-nucleotide resolution, RNA-seq, single-cell RNA-seq, stress granule imaging in patient cells","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — novel CLIP method with single-nucleotide resolution, corroborated by patient-derived cells and multiple orthogonal approaches","pmids":["35303483"],"is_preprint":false},{"year":2021,"finding":"U2AF1 S34F mutation results in misregulation of translation initiation and ribosome biogenesis machinery, increasing mRNA translation at the single-cell level. Among translationally upregulated targets is Nucleophosmin 1 (NPM1); depletion of NPM1 impairs viability of U2AF1-S34F mutant cells and causes ribosomal RNA processing defects, revealing a synthetic interaction between U2AF1, NPM1, and ribosome biogenesis.","method":"Polysome profiling, single-cell translation assays, NPM1 depletion functional assays, rRNA processing analysis","journal":"PLoS biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — polysome profiling and functional depletion experiments; single lab, multiple methods","pmids":["33137094"],"is_preprint":false},{"year":2021,"finding":"Deletion of U2af1 in mouse hematopoietic cells causes pancytopenia, ablation of hematopoietic stem/progenitor cells, bone marrow failure, increased DNA damage in progenitors, and early lethality. U2af1 deficiency induces splicing alterations in genes important for HSPC function including altered splicing of Nfya and Pbx1 transcription factors.","method":"Conditional U2af1 knockout mice, RNA-seq, flow cytometry, transplantation assays","journal":"Leukemia","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockout with defined hematopoietic phenotypes, RNA-seq, and transplantation assays; multiple orthogonal methods","pmids":["33414485"],"is_preprint":false},{"year":2021,"finding":"Mutant U2AF1(S34F)-induced mis-splicing of H2afy (producing reduced H2afy1.1 isoform) is responsible for reduced B cells in U2AF1(S34F) mice. H2AFY1.1 is enriched at the EBF1 promoter, and its reduction decreases Ebf1 expression. Induced expression of H2AFY1.1 in U2AF1(S34F) cells rescues reduced EBF1 expression and B cell numbers in vivo.","method":"Transgenic mouse model, RNA-seq, ChIP, lentiviral rescue experiments, flow cytometry","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistatic rescue experiments in vivo combined with ChIP and RNA-seq; multiple orthogonal methods","pmids":["34469727"],"is_preprint":false},{"year":2021,"finding":"U2AF1 mutant hematopoietic cells require expression of the wild-type U2AF1 allele for survival in vivo (haplo-essential). Deletion of the WT U2af1 allele in U2AF1(S34F) heterozygous mutant hematopoietic cells is lethal, while U2af1 heterozygous knockout alone has no hematopoietic phenotype. Mice transplanted with U2AF1(S34F) leukemia cells had reduced tumor burden and improved survival after WT U2af1 deletion.","method":"Conditional WT allele knockout in U2AF1(S34F) mutant background, transplantation model, survival analysis","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in vivo with defined lethal phenotype, validated in leukemia transplant model","pmids":["34546980"],"is_preprint":false},{"year":2021,"finding":"Cells with SF3B1 or U2AF1 mutations have attenuated nonsense-mediated RNA decay (NMD) activity and are more sensitive to NMD inhibition. This sensitivity is accompanied by elevated DNA replication obstruction, DNA damage, and chromosomal instability, and can be rescued by overexpression of RNase H1 (R-loop removal), establishing a functional link between spliceosome mutations, NMD activity, and R-loop-induced genomic instability.","method":"CRISPR-Cas9 genome-wide knockout screen with NMD reporter, NMD activity assays, RNase H1 rescue, DNA damage assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen plus functional rescue experiments; single study with multiple orthogonal approaches","pmids":["34215620"],"is_preprint":false},{"year":2005,"finding":"The Shigella effector IpaH9.8 has specific binding affinity to U2AF35 (U2AF1) and interferes with U2AF35-dependent splicing of IgM pre-mRNA. Reducing U2AF35 levels in HeLa cells decreases expression of pro-inflammatory cytokine genes (IL-8, RANTES, GM-CSF, IL-1β), establishing U2AF35 as a regulator of inflammatory gene expression downstream of splicing.","method":"Binding assays, in vitro splicing assay, siRNA knockdown with RT-PCR","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct binding assay plus functional splicing and gene expression assays; single lab, pathogen-host interaction context","pmids":["15950937"],"is_preprint":false},{"year":2021,"finding":"m6A methylation deposited at the 3' splice site AG by METT-10 (METTL16 ortholog) physically prevents U2AF35 from recognizing the 3' splice site, inhibiting splicing. This m6A-mediated inhibition of U2AF35 binding to the 3' splice site is conserved in mammals.","method":"In vitro binding competition assays with m6A-modified RNA, C. elegans genetic model, mammalian splicing reporter assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical demonstration that m6A prevents U2AF35 binding, with conservation shown in mammals","pmids":["33930289"],"is_preprint":false},{"year":2020,"finding":"U2AF1 S34F induces mis-splicing of RAD51 in lung cancer cells, causing downregulation of RAD51 protein via aberrant exon usage and enhanced DNA damage. Overexpression of RAD51 rescues the defective DNA damage response. U2AF1-S34F cells are sensitized to ATR inhibitors, and the combination with RAD51 inhibitors exacerbates DNA damage.","method":"Ectopic expression of WT and mutant U2AF1 in A549 cells, RNA-seq, western blot, ATR/RAD51 inhibitor functional assays","journal":"Clinical and experimental pharmacology & physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA-seq plus rescue experiment with RAD51 overexpression; single lab","pmids":["35434831"],"is_preprint":false},{"year":2023,"finding":"U2AF1 binds directly to R-loops and DNA G4 structures at low-nM affinity in promoter regions. U2AF1 can undergo phase separation, which is stimulated by binding with R-loops (but not duplex DNA, RNA/DNA hybrid, DNA G4, or single-stranded RNA). U2AF1 binding to promoter R-loops in cells competes with its interaction with 3' splice sites and leads to augmented distribution of RNA Pol II to promoters over gene bodies, modulating cotranscriptional pre-mRNA splicing.","method":"ChIP-seq overlap analysis, in vitro binding assays, phase separation assays, Pol II ChIP-seq","journal":"Journal of the American Chemical Society","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding assays plus cellular ChIP-seq; phase separation assay with single lab","pmids":["37733759"],"is_preprint":false},{"year":2017,"finding":"Single molecule methods showed U2AF35 and U2AF65 bind in 1:1 stoichiometry with a 3' splice site in the presence of ATP. Pre-mRNA molecules with two alternative 3' splice sites can be concurrently bound by two molecules of U2AF or two U2 snRNPs, but concurrent occupancy inhibits splicing. Stoichiometric binding requires conditions consistent with coalescence of 5' and 3' sites in a complex I; complex A formation is associated with loss of both U2AF65 and U2AF35.","method":"Single-molecule fluorescence imaging, stoichiometry analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — single-molecule reconstitution, single lab, novel mechanistic insight on stoichiometry","pmids":["27683217"],"is_preprint":false},{"year":2019,"finding":"Expression of U2AF1 isoforms (U2AF1a and U2AF1b, encoded by tandem alternative exons) is controlled by mTOR signaling. The two isoforms have distinct splice site sequence preferences and different protein interactomes. U2AF1a-driven transcriptomes feature alternative splicing events in 5'-UTRs favorable for translation, linking mTOR-regulated U2AF1 isoform switching to translational control.","method":"Genome editing, customized transcriptome profiling (RNA-seq), CLIP-based interactome analysis, mTOR inhibitor experiments","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome editing plus CLIP and RNA-seq; single lab, multiple orthogonal methods","pmids":["31504847"],"is_preprint":false},{"year":2020,"finding":"Both zinc finger domains of U2AF35 are required for splicing regulation, while only ZnF2 controls protein stability and contributes to interaction with U2AF65. A naturally occurring splice variant of the paralog U2AF26 lacking ZnF2 localizes to the cytoplasm and, together with U2AF35, increases translation when tethered to the 5'UTR of mRNA via MS2 tethering assay, providing evidence for a cytoplasmic translation-regulatory role of the zinc finger domains.","method":"Zinc finger domain mutant analysis, splicing reporter assays, MS2 tethering translation assay, Ribo-seq","journal":"RNA biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis with functional splicing/translation assays; extends findings to zinc finger function specifically","pmids":["32116123"],"is_preprint":false},{"year":2024,"finding":"U2AF1 S34F and Q157R mutations orchestrate aberrant inclusion of exon 11 (encoding a premature termination codon) in EIF4A2 pre-mRNA, leading to reduced eIF4A2 protein via NMD. This causes a net decrease in global mRNA translation and induction of the integrated stress response (ISR), which promotes chemoresistance in AML. ISRIB (ISR inhibitor) sensitizes U2AF1-mutant cells to chemotherapy.","method":"Integrative analysis of RNA-seq and binding data from AML cell lines, single-cell RNA-seq, ISRIB pharmacological inhibition, patient multiomics data","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA-seq plus pharmacological rescue with ISRIB; validated in multiple AML datasets","pmids":["38417135"],"is_preprint":false},{"year":2010,"finding":"U2AF35-related protein Urp contacts the 3' splice site of both U12-type (minor class) and U2-type (major class) introns. For U12-type introns, Urp is recruited ATP-dependently to promote spliceosomal complex formation. For U2-type introns, Urp is specifically required for the second step of splicing. This establishes that through recognition of a common splicing element (3' splice site), Urp facilitates distinct steps of U2- and U12-type intron splicing.","method":"UV crosslinking, splicing complementation assays, spliceosomal complex assembly analysis","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — crosslinking and functional complementation assays; single lab but multiple intron classes tested","pmids":["21041408"],"is_preprint":false}],"current_model":"U2AF1 (U2AF35) is the small subunit of the U2AF heterodimer that directly recognizes the conserved AG dinucleotide at the 3' splice site via its zinc finger domains; it stabilizes U2AF2 (U2AF65) binding to weak polypyrimidine tracts through a 'tongue-in-groove' heterodimerization interface, bridges SR protein enhancer complexes to U2AF65, and undergoes a conformational switch between closed and open states depending on polypyrimidine tract strength; cancer-associated mutations (S34F, Q157R) alter RNA-sequence specificity at the -3 and +1 positions of the 3' splice site, dysregulate alternative splicing of hundreds of genes (including IRAK4, ATG7, EIF4A2, H2AFY), and additionally impair a cytoplasmic translation-regulatory function of the protein, collectively contributing to MDS/AML pathogenesis through altered splicing, NMD attenuation, integrated stress response induction, and aberrant autophagy."},"narrative":{"mechanistic_narrative":"U2AF1 (U2AF35) is the small subunit of the U2AF splicing factor heterodimer that directly recognizes the conserved AG dinucleotide at the 3' splice site during early spliceosome assembly, a function established by site-specific UV crosslinking and in vitro genetic selection [PMID:10617206, PMID:10617208]. It is required for both constitutive and enhancer-dependent splicing, recruiting and stabilizing U2AF2 (U2AF65) on weak polypyrimidine tracts and bridging SR-protein enhancer complexes to U2AF65 [PMID:8647433, PMID:10567551, PMID:11421359]. Structurally, U2AF1 engages U2AF65 through a 'tongue-in-groove' interface formed by reciprocal tryptophan residues between its atypical RRM and the U2AF65 proline-rich segment; this pseudo-RRM is unstructured in isolation and folds upon U2AF65 binding, while AG recognition is achieved through its zinc-finger domains [PMID:11551507, PMID:12297299, PMID:32958768, PMID:32116123]. The heterodimer governs 3' splice site selection through a conformational equilibrium of U2AF65 tandem RRMs between closed and open states, tuned by polypyrimidine-tract strength [PMID:32343311]. Recurrent MDS/AML mutations in the zinc fingers (S34F, Q157R) establish aberrant RNA contacts at the -3 and +1 positions of the 3' splice site, shifting sequence specificity (e.g. preferential CAG over UAG recognition), compromising U2AF65-RNA interactions, and driving genome-wide intron retention, exon skipping, and altered hematopoiesis in vivo [PMID:25267526, PMID:25311244, PMID:32958768, PMID:35303483, PMID:25965570]. These mutant-driven mis-splicing events converge on disease-relevant targets including IRAK4 (a longer myddosome-activating isoform), H2AFY (controlling EBF1 and B-cell output), EIF4A2 (NMD-triggered loss inducing the integrated stress response), and ATG7 (aberrant polyadenylation causing autophagy defects) [PMID:31011167, PMID:34469727, PMID:38417135, PMID:27184077]. Mutant U2AF1 additionally attenuates nonsense-mediated decay and exerts a splicing-independent cytoplasmic function, binding mature mRNA to negatively regulate translation [PMID:34215620, PMID:30842218, PMID:32116123]. Recurrent mutations operate in a dosage-dependent, haplo-essential manner: the wild-type allele is required for survival of mutant hematopoietic cells [PMID:27776121, PMID:34546980].","teleology":[{"year":1996,"claim":"Established that U2AF35 is functionally required for splicing and acts as a molecular bridge, resolving whether the small subunit had an essential role beyond merely partnering U2AF65.","evidence":"Nuclear extract depletion/complementation with recombinant U2AF35 and protein-RNA interaction assays","pmids":["8647433"],"confidence":"High","gaps":["Direct RNA sequence recognized by U2AF35 not yet defined","Structural basis of bridging unknown"]},{"year":1999,"claim":"Identified the direct RNA target of U2AF35, showing it sequence-specifically contacts the 3' splice site AG and that this contact is critical for U2AF binding at weak polypyrimidine tracts.","evidence":"Site-specific UV crosslinking, in vitro genetic selection, splicing competition assays","pmids":["10617206","10617208","10567551"],"confidence":"High","gaps":["Atomic-level basis of AG recognition not resolved","In vivo stoichiometry not established"]},{"year":2001,"claim":"Defined the structural and mechanistic basis of heterodimerization and dual function, answering how U2AF35 and U2AF65 physically interact and how U2AF35 contributes beyond stabilizing U2AF65.","evidence":"X-ray crystallography of the core heterodimer, NMR of free/complexed RRM, depletion/complementation with truncation mutants","pmids":["11551507","11604503","11421359","12297299"],"confidence":"High","gaps":["Structure of zinc fingers bound to RNA not yet solved","Downstream spliceosomal events triggered by U2AF35 unidentified"]},{"year":2008,"claim":"Connected 3' splice site recognition to tri-snRNP recruitment, addressing how the prespliceosome transitions toward later assembly.","evidence":"Co-immunoprecipitation, pulldowns, domain mapping of SPF30 bridging U2AF35 and hPrp3","pmids":["18211889"],"confidence":"Medium","gaps":["Functional consequence of disrupting the bridge not tested in vivo","Single-lab interaction mapping"]},{"year":2011,"claim":"Linked U2AF1 to human disease by identifying recurrent S34 zinc-finger mutations in MDS and demonstrating altered splicing, framing spliceosome mutation as a leukemia mechanism.","evidence":"Whole-genome sequencing of MDS patients and in vitro reporter splicing assays","pmids":["22158538"],"confidence":"Medium","gaps":["Genome-wide splicing targets not yet mapped","Causal contribution to hematopoiesis untested in vivo"]},{"year":2014,"claim":"Defined the molecular consequence of the mutations, showing they alter 3' splice site sequence preference at specific nucleotide positions and reprogram splicing in a zinc-finger-specific manner.","evidence":"RNA-seq splice junction analysis, in vitro affinity-binding assays, cell culture expression, immunofluorescence","pmids":["25267526","25311244"],"confidence":"High","gaps":["Atomic basis of changed specificity not yet visualized","Causal disease phenotypes from these splicing changes unresolved"]},{"year":2015,"claim":"Demonstrated in vivo that mutant U2AF1 drives genome-wide splicing changes and perturbs hematopoiesis, moving from cell-culture inference to organismal phenotype.","evidence":"Doxycycline-inducible S34F transgenic mouse model with whole-transcriptome RNA-seq","pmids":["25965570"],"confidence":"High","gaps":["Which specific mis-spliced targets drive phenotype not isolated","Full leukemic transformation not recapitulated"]},{"year":2016,"claim":"Showed mutant effects scale with mutant:wild-type ratio and are explained by altered binding affinity, and uncovered an alternative-polyadenylation mechanism on ATG7 causing autophagy defects.","evidence":"Endogenous-locus genetic modification, quantitative RNA-seq, in vitro binding, 3'RACE, western blot, patient 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tuned by tract strength.","evidence":"X-ray crystallography of WT and mutant U2AF1-RNA complexes, single-molecule FRET with structure-guided mutagenesis, zinc-finger domain dissection, RAD51 mis-splicing assays","pmids":["32958768","32343311","32116123","35434831"],"confidence":"High","gaps":["Conformational dynamics in intact spliceosome not captured","Therapeutic exploitation of DNA-damage sensitivity not validated clinically"]},{"year":2021,"claim":"Integrated the mutant pathomechanism across genomic instability, dosage dependence, and specific lineage defects, establishing wild-type allele haplo-essentiality and downstream NMD, stress-granule, and B-cell phenotypes.","evidence":"Single-nucleotide CLIP, conditional WT-allele knockout in mutant background, CRISPR NMD screen with RNase H1 rescue, transgenic H2afy rescue with ChIP, polysome/NPM1 depletion assays","pmids":["35303483","34546980","34215620","34469727","33137094"],"confidence":"High","gaps":["Mechanistic link between mutant splicing and stress-granule induction incomplete","How wild-type allele rescues survival mechanistically unknown"]},{"year":2023,"claim":"Revealed a chromatin/cotranscriptional role through direct R-loop and G4 binding and phase separation, connecting U2AF1 occupancy at promoters to RNA Pol II distribution and splicing.","evidence":"ChIP-seq overlap, in vitro binding and phase-separation assays, Pol II ChIP-seq","pmids":["37733759"],"confidence":"Medium","gaps":["In vivo relevance of phase separation to splicing not established","Single-lab finding awaiting orthogonal confirmation"]},{"year":2024,"claim":"Connected mutant splicing to a therapeutically actionable stress phenotype, showing EIF4A2 mis-splicing reduces global translation and induces the integrated stress response promoting chemoresistance.","evidence":"Integrative RNA-seq/binding analysis in AML cell lines, single-cell RNA-seq, ISRIB pharmacological inhibition, patient 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spliceosome U2AF1 significantly inhibits the development of human erythroid cells.","date":"2019","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31144421","citation_count":12,"is_preprint":false},{"pmid":"25706610","id":"PMC_25706610","title":"Dosage of the Abcg1-U2af1 region modifies locomotor and cognitive deficits observed in the Tc1 mouse model of Down syndrome.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25706610","citation_count":12,"is_preprint":false},{"pmid":"8660980","id":"PMC_8660980","title":"The gene for human U2 snRNP auxiliary factor small 35-kDa subunit (U2AF1) maps to the progressive myoclonus epilepsy (EPM1) critical region on chromosome 21q22.3.","date":"1996","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8660980","citation_count":11,"is_preprint":false},{"pmid":"33330095","id":"PMC_33330095","title":"Lysine in Combination With Estradiol Promote Dissemination of Estrogen Receptor 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Mutational analysis and in vitro genetic selection showed U2AF35 has sequence-specific RNA-binding activity recognizing the 3'-splice-site consensus AG/G. For introns with weak polypyrimidine tracts, this U2AF35-3'-splice-site interaction is critical for U2AF binding and splicing.\",\n      \"method\": \"Site-specific UV crosslinking, mutational analysis, in vitro genetic selection, splicing assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis, crosslinking, and genetic selection; independently replicated by concurrent Nature paper (PMID:10617208)\",\n      \"pmids\": [\"10617206\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"U2AF35 contacts the AG dinucleotide at the 3' splice site only when located in proximity to the polypyrimidine tract (shown by UV crosslinking). This interaction stabilizes U2AF65 binding, such that Sex-lethal (SXL) can no longer displace U2AF65 from the polypyrimidine tract. SXL-mediated splicing inhibition of msl-2 requires a combination of SXL binding at the polypyrimidine tract and an unusually long distance between the poly(Y) tract and the AG, which weakens U2AF35-AG interaction.\",\n      \"method\": \"UV crosslinking, in vitro splicing competition assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — UV crosslinking with functional splicing assays; replicates and extends concurrent Nature paper (PMID:10617206)\",\n      \"pmids\": [\"10617208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"U2AF35 is required for constitutive splicing and functions as a mediator of enhancer-dependent splicing. Nuclear extracts deficient in U2AF35 are inactive; both constitutive and enhancer-dependent splicing are restored by recombinant U2AF35. In vitro protein-RNA interaction studies showed U2AF35 directly mediates interactions between U2AF65 and proteins bound to splicing enhancers, acting as a bridge to recruit U2AF65 to weak 3' splice sites.\",\n      \"method\": \"Nuclear extract depletion/complementation, in vitro splicing assays, protein-RNA interaction studies\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution of splicing activity with purified recombinant U2AF35, multiple orthogonal assays\",\n      \"pmids\": [\"8647433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"X-ray crystal structure of the human core U2AF heterodimer (U2AF35 central domain + proline-rich region of U2AF65) at 2.2 Å resolution revealed a novel 'tongue-in-groove' protein-protein interaction via reciprocal tryptophan residues between an atypical RRM of U2AF35 and U2AF65 polyproline segment. Biochemical experiments showed the core heterodimer binds RNA and that the interacting tryptophan side chains are essential for U2AF dimerization.\",\n      \"method\": \"X-ray crystallography (2.2 Å), site-directed mutagenesis, RNA-binding biochemical assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis and biochemical validation in single study\",\n      \"pmids\": [\"11551507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"U2AF35 has a dual function in AG-dependent pre-mRNA splicing: (1) its interaction with the consensus 3' splice site AG stabilizes U2AF65 binding to weak polypyrimidine tracts, and (2) U2AF35 triggers additional downstream events in spliceosome assembly beyond U2AF65 stabilization. RS domain-mediated interactions with SR proteins bound to exonic splicing enhancers are dispensable for U2AF35 activity; a truncation mutant lacking the RS domain but retaining the pseudo-RRM is active in complementation assays.\",\n      \"method\": \"Nuclear extract depletion/complementation, UV crosslinking, in vitro splicing assays, truncation mutant analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with mutants and multiple orthogonal methods in single study\",\n      \"pmids\": [\"11604503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"U2AF35 has a substrate-specific requirement: recombinant U2AF65 alone is sufficient for splicing of two constitutively spliced pre-mRNAs in U2AF-depleted extracts, but both U2AF65 and U2AF35 (and their interaction) are required for splicing of an immunoglobulin µ pre-mRNA with a weak polypyrimidine tract and purine-rich exonic splicing enhancer. U2AF35 splicing activation occurs without changes in U2AF65 crosslinking to the polypyrimidine tract.\",\n      \"method\": \"Chromatographic depletion of U2AF, in vitro splicing complementation, UV crosslinking\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with recombinant proteins, multiple substrates tested, crosslinking controls\",\n      \"pmids\": [\"10567551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Splicing activators (SR proteins on enhancers) promote binding of both U2AF65 and U2AF35 to weak 3' splice sites under splicing conditions, and U2AF35 is required for maximum levels of activator-dependent splicing. Base substitutions converting weak 3' splice sites to consensus relieve the requirement for splicing activators by increasing U2AF binding directly.\",\n      \"method\": \"In vitro splicing assays, RNA-protein binding assays, mutational analysis of splice sites\",\n      \"journal\": \"RNA\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with multiple orthogonal methods confirming U2AF recruitment model\",\n      \"pmids\": [\"11421359\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The U2AF35 RRM is unstructured in isolation but its tertiary structure is induced upon binding to U2AF65. This induced folding is mediated specifically by the N-terminal proline-rich region of U2AF65 and does not involve the U2AF65 RRMs.\",\n      \"method\": \"Nuclear magnetic resonance (NMR) spectroscopy of free and complexed U2AF35 RRM\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural characterization with domain-mapping experiments, single study\",\n      \"pmids\": [\"12297299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Direct interaction between U2AF35 and U2AF65 was demonstrated in vivo in live cell nuclei by FRET microscopy. Additionally, a novel U2AF35 self-interaction was discovered both in vivo (by FRET) and confirmed in vitro by biochemical assays, suggesting the U2AF complex stoichiometry may differ from the expected heterodimer in vivo.\",\n      \"method\": \"FRET microscopy in live cells, biochemical in vitro binding assays\",\n      \"journal\": \"RNA\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET in live cells plus biochemical confirmation, single lab with two orthogonal methods\",\n      \"pmids\": [\"16043505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Splicing factor SPF30 bridges an interaction between U2AF35 (prespliceosome) and hPrp3 (tri-snRNP component). The N-terminal domain of SPF30 interacts with U2AF35, and the C-terminus of SPF30 interacts with hPrp3 simultaneously, potentially linking 3' splice site recognition to tri-snRNP addition.\",\n      \"method\": \"Co-immunoprecipitation, pulldown assays, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pulldowns with domain mapping, simultaneous interaction confirmed, single lab\",\n      \"pmids\": [\"18211889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Missense mutations affecting Ser34 (S34F) in the zinc fingers of U2AF1 are recurrently found in MDS patients. Mutant U2AF1 promotes enhanced splicing and exon skipping in reporter assays in vitro, implicating altered pre-mRNA splicing as a mechanism for MDS pathogenesis.\",\n      \"method\": \"Whole-genome sequencing, reporter splicing assays in vitro\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Strong — discovery of mutation with functional reporter assay; widely replicated in subsequent studies\",\n      \"pmids\": [\"22158538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"U2AF1 mutations (S34F/Y and Q157R/P) alter the preferred 3' splice site motif in patients, in cell culture, and in vitro. S34F/Y mutations cause preferential recognition of CAG over UAG 3' splice site sequences. Mutations in the first and second zinc fingers give rise to different alterations in splice site preference and largely distinct downstream splicing programs.\",\n      \"method\": \"RNA-seq splice junction analysis, in vitro RNA-binding assays, cell culture expression system\",\n      \"journal\": \"Genome research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro binding assays combined with transcriptome-wide RNA-seq in patients and cell culture; replicated across multiple contexts\",\n      \"pmids\": [\"25267526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"U2AF1 S34F mutation alters sequence specificity of RNA binding, decreasing affinity for uridine (relative to cytidine) at the -3 position immediately upstream of the splice acceptor site, leading to aberrant alternative splicing. U2AF1(S34F) co-localizes normally with U2AF2 within nuclear speckles (localization not disrupted by mutation).\",\n      \"method\": \"RNA-seq splice junction analysis, affinity-binding assays, immunofluorescence co-localization\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — affinity binding assay plus RNA-seq with validation in primary patient samples; single lab, two orthogonal methods\",\n      \"pmids\": [\"25311244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mutant U2AF1(S34F) expressed in hematopoietic progenitor cells in a doxycycline-inducible transgenic mouse model causes changes in pre-mRNA splicing genome-wide and alters hematopoiesis in vivo. Common mutant U2AF1-induced splicing alterations are enriched in RNA processing genes, ribosomal genes, and MDS/AML-associated genes.\",\n      \"method\": \"Doxycycline-inducible transgenic mouse model, whole transcriptome RNA-seq\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional model with genome-wide RNA-seq; replicated in human datasets\",\n      \"pmids\": [\"25965570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"U2AF1(S34F) mutation causes aberrant selection of a distal cleavage and polyadenylation (CP) site in ATG7 pre-mRNA (not altered splicing), producing a longer ATG7 mRNA that is translated inefficiently, leading to decreased ATG7 levels, autophagy defect, and cellular transformation. This mechanism was confirmed in MDS/AML patient samples harboring U2AF1(S34F).\",\n      \"method\": \"Deep sequencing of transformed cell lines, 3' RACE, quantitative RT-PCR, western blot, patient sample validation\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (sequencing, RACE, western blot) with patient sample validation; mechanistically novel finding\",\n      \"pmids\": [\"27184077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"S34F-associated changes in alternative splicing are proportional to the ratio of S34F:wild-type U2AF1 gene products, not to absolute levels of either factor. Preferential recognition of specific 3' splice sites in S34F-expressing cells is largely explained by differential in vitro RNA-binding affinities of mutant versus wild-type U2AF1. Wild-type U2AF1 is required for cell survival regardless of S34F allele status.\",\n      \"method\": \"Endogenous locus genetic modification, quantitative RNA-seq, in vitro RNA-binding assays, in vivo tumor xenograft\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — genetic allele manipulation plus in vitro binding assays with functional cellular phenotypes\",\n      \"pmids\": [\"27776121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"U2AF1 has a noncanonical function in translation regulation: it directly binds mature mRNA in the cytoplasm and negatively regulates mRNA translation. This splicing-independent role is altered by the S34F mutation; polysome profiling shows mutation affects translation of hundreds of mRNAs. One consequence is increased synthesis of secreted chemokine IL-8, contributing to metastasis and cancer progression.\",\n      \"method\": \"CLIP-seq (cytoplasmic), polysome profiling, quantitative proteomics, in vivo metastasis assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct RNA binding in cytoplasm demonstrated by CLIP, polysome profiling, functional in vivo consequence\",\n      \"pmids\": [\"30842218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"U2AF1 mutations induce expression of a longer IRAK4 isoform (IRAK4-L, retaining exon 4) that assembles with the myddosome and results in maximal NF-κB activation. IRAK4-L expression is mediated by mutant U2AF1, and inhibition of IRAK4-L abrogates leukemic growth in AML cells with high IRAK4-L expression.\",\n      \"method\": \"Exon usage analysis of patient RNA-seq, cell line functional assays, IRAK4 inhibitor experiments\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — patient RNA-seq corroborated by functional cell line assays with pharmacological inhibition; multiple independent AML/MDS datasets\",\n      \"pmids\": [\"31011167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"U2AF1 S34F preferentially binds and modulates splicing of introns containing CAG trinucleotides at their 3' splice junctions compared to wild-type. CLIP analysis showed a shift in cross-linking at 3' splice sites, significantly associated with alternative splicing of skipped exons. S34F also induces increased splicing of the long SLC34A2-ROS1 isoform, associated with enhanced tumor cell invasion.\",\n      \"method\": \"CLIP-seq, RNA-seq, functional invasion assays in cells with ROS1 translocation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — CLIP-seq providing direct binding evidence plus RNA-seq and functional assays; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31836708\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structures of wild-type and pathogenic mutant U2AF1 complexed with target RNA at the 3' splice site revealed the molecular mechanism of 3' splice site selection. The structures showed how S34F and Q157R mutations cause aberrant 3' splice site recognition by altering RNA contacts within the zinc finger domains.\",\n      \"method\": \"X-ray crystallography of WT and mutant U2AF1-RNA complexes\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of WT and two pathogenic mutants in complex with RNA, directly revealing mechanism\",\n      \"pmids\": [\"32958768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"U2AF1 subunit stabilizes a closed conformation of the U2AF2 (U2AF65) tandem RRMs in the absence of RNA (high FRET). Upon binding a strong uridine-rich splice site, U2AF2 switches to an open conformation. For weak uridine-poor polypyrimidine tracts, the heterodimer binds as a mixture of closed and open conformations, and the S34F mutation modulates this equilibrium. Structure-guided mutagenesis confirmed the conformational assignments.\",\n      \"method\": \"Single-molecule FRET, structure-guided mutagenesis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule FRET with mutagenesis validation; mechanistically rigorous single study\",\n      \"pmids\": [\"32343311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"U2AF1 S34F and Q157R mutants establish new RNA contacts at positions -3 and +1 nucleotides of the 3' splice site AG, respectively (revealed by single-nucleotide resolution CLIP). These new contacts compromise U2AF2-RNA interactions, resulting predominantly in intron retention and exon exclusion. Mutant U2AF1-expressing cell lines and patient-derived MDS/AML blasts display a heightened stress granule response.\",\n      \"method\": \"High-resolution CLIP at single-nucleotide resolution, RNA-seq, single-cell RNA-seq, stress granule imaging in patient cells\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — novel CLIP method with single-nucleotide resolution, corroborated by patient-derived cells and multiple orthogonal approaches\",\n      \"pmids\": [\"35303483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"U2AF1 S34F mutation results in misregulation of translation initiation and ribosome biogenesis machinery, increasing mRNA translation at the single-cell level. Among translationally upregulated targets is Nucleophosmin 1 (NPM1); depletion of NPM1 impairs viability of U2AF1-S34F mutant cells and causes ribosomal RNA processing defects, revealing a synthetic interaction between U2AF1, NPM1, and ribosome biogenesis.\",\n      \"method\": \"Polysome profiling, single-cell translation assays, NPM1 depletion functional assays, rRNA processing analysis\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — polysome profiling and functional depletion experiments; single lab, multiple methods\",\n      \"pmids\": [\"33137094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Deletion of U2af1 in mouse hematopoietic cells causes pancytopenia, ablation of hematopoietic stem/progenitor cells, bone marrow failure, increased DNA damage in progenitors, and early lethality. U2af1 deficiency induces splicing alterations in genes important for HSPC function including altered splicing of Nfya and Pbx1 transcription factors.\",\n      \"method\": \"Conditional U2af1 knockout mice, RNA-seq, flow cytometry, transplantation assays\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockout with defined hematopoietic phenotypes, RNA-seq, and transplantation assays; multiple orthogonal methods\",\n      \"pmids\": [\"33414485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mutant U2AF1(S34F)-induced mis-splicing of H2afy (producing reduced H2afy1.1 isoform) is responsible for reduced B cells in U2AF1(S34F) mice. H2AFY1.1 is enriched at the EBF1 promoter, and its reduction decreases Ebf1 expression. Induced expression of H2AFY1.1 in U2AF1(S34F) cells rescues reduced EBF1 expression and B cell numbers in vivo.\",\n      \"method\": \"Transgenic mouse model, RNA-seq, ChIP, lentiviral rescue experiments, flow cytometry\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistatic rescue experiments in vivo combined with ChIP and RNA-seq; multiple orthogonal methods\",\n      \"pmids\": [\"34469727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"U2AF1 mutant hematopoietic cells require expression of the wild-type U2AF1 allele for survival in vivo (haplo-essential). Deletion of the WT U2af1 allele in U2AF1(S34F) heterozygous mutant hematopoietic cells is lethal, while U2af1 heterozygous knockout alone has no hematopoietic phenotype. Mice transplanted with U2AF1(S34F) leukemia cells had reduced tumor burden and improved survival after WT U2af1 deletion.\",\n      \"method\": \"Conditional WT allele knockout in U2AF1(S34F) mutant background, transplantation model, survival analysis\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in vivo with defined lethal phenotype, validated in leukemia transplant model\",\n      \"pmids\": [\"34546980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cells with SF3B1 or U2AF1 mutations have attenuated nonsense-mediated RNA decay (NMD) activity and are more sensitive to NMD inhibition. This sensitivity is accompanied by elevated DNA replication obstruction, DNA damage, and chromosomal instability, and can be rescued by overexpression of RNase H1 (R-loop removal), establishing a functional link between spliceosome mutations, NMD activity, and R-loop-induced genomic instability.\",\n      \"method\": \"CRISPR-Cas9 genome-wide knockout screen with NMD reporter, NMD activity assays, RNase H1 rescue, DNA damage assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen plus functional rescue experiments; single study with multiple orthogonal approaches\",\n      \"pmids\": [\"34215620\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The Shigella effector IpaH9.8 has specific binding affinity to U2AF35 (U2AF1) and interferes with U2AF35-dependent splicing of IgM pre-mRNA. Reducing U2AF35 levels in HeLa cells decreases expression of pro-inflammatory cytokine genes (IL-8, RANTES, GM-CSF, IL-1β), establishing U2AF35 as a regulator of inflammatory gene expression downstream of splicing.\",\n      \"method\": \"Binding assays, in vitro splicing assay, siRNA knockdown with RT-PCR\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct binding assay plus functional splicing and gene expression assays; single lab, pathogen-host interaction context\",\n      \"pmids\": [\"15950937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"m6A methylation deposited at the 3' splice site AG by METT-10 (METTL16 ortholog) physically prevents U2AF35 from recognizing the 3' splice site, inhibiting splicing. This m6A-mediated inhibition of U2AF35 binding to the 3' splice site is conserved in mammals.\",\n      \"method\": \"In vitro binding competition assays with m6A-modified RNA, C. elegans genetic model, mammalian splicing reporter assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical demonstration that m6A prevents U2AF35 binding, with conservation shown in mammals\",\n      \"pmids\": [\"33930289\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"U2AF1 S34F induces mis-splicing of RAD51 in lung cancer cells, causing downregulation of RAD51 protein via aberrant exon usage and enhanced DNA damage. Overexpression of RAD51 rescues the defective DNA damage response. U2AF1-S34F cells are sensitized to ATR inhibitors, and the combination with RAD51 inhibitors exacerbates DNA damage.\",\n      \"method\": \"Ectopic expression of WT and mutant U2AF1 in A549 cells, RNA-seq, western blot, ATR/RAD51 inhibitor functional assays\",\n      \"journal\": \"Clinical and experimental pharmacology & physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA-seq plus rescue experiment with RAD51 overexpression; single lab\",\n      \"pmids\": [\"35434831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"U2AF1 binds directly to R-loops and DNA G4 structures at low-nM affinity in promoter regions. U2AF1 can undergo phase separation, which is stimulated by binding with R-loops (but not duplex DNA, RNA/DNA hybrid, DNA G4, or single-stranded RNA). U2AF1 binding to promoter R-loops in cells competes with its interaction with 3' splice sites and leads to augmented distribution of RNA Pol II to promoters over gene bodies, modulating cotranscriptional pre-mRNA splicing.\",\n      \"method\": \"ChIP-seq overlap analysis, in vitro binding assays, phase separation assays, Pol II ChIP-seq\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding assays plus cellular ChIP-seq; phase separation assay with single lab\",\n      \"pmids\": [\"37733759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Single molecule methods showed U2AF35 and U2AF65 bind in 1:1 stoichiometry with a 3' splice site in the presence of ATP. Pre-mRNA molecules with two alternative 3' splice sites can be concurrently bound by two molecules of U2AF or two U2 snRNPs, but concurrent occupancy inhibits splicing. Stoichiometric binding requires conditions consistent with coalescence of 5' and 3' sites in a complex I; complex A formation is associated with loss of both U2AF65 and U2AF35.\",\n      \"method\": \"Single-molecule fluorescence imaging, stoichiometry analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule reconstitution, single lab, novel mechanistic insight on stoichiometry\",\n      \"pmids\": [\"27683217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Expression of U2AF1 isoforms (U2AF1a and U2AF1b, encoded by tandem alternative exons) is controlled by mTOR signaling. The two isoforms have distinct splice site sequence preferences and different protein interactomes. U2AF1a-driven transcriptomes feature alternative splicing events in 5'-UTRs favorable for translation, linking mTOR-regulated U2AF1 isoform switching to translational control.\",\n      \"method\": \"Genome editing, customized transcriptome profiling (RNA-seq), CLIP-based interactome analysis, mTOR inhibitor experiments\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome editing plus CLIP and RNA-seq; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31504847\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Both zinc finger domains of U2AF35 are required for splicing regulation, while only ZnF2 controls protein stability and contributes to interaction with U2AF65. A naturally occurring splice variant of the paralog U2AF26 lacking ZnF2 localizes to the cytoplasm and, together with U2AF35, increases translation when tethered to the 5'UTR of mRNA via MS2 tethering assay, providing evidence for a cytoplasmic translation-regulatory role of the zinc finger domains.\",\n      \"method\": \"Zinc finger domain mutant analysis, splicing reporter assays, MS2 tethering translation assay, Ribo-seq\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis with functional splicing/translation assays; extends findings to zinc finger function specifically\",\n      \"pmids\": [\"32116123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"U2AF1 S34F and Q157R mutations orchestrate aberrant inclusion of exon 11 (encoding a premature termination codon) in EIF4A2 pre-mRNA, leading to reduced eIF4A2 protein via NMD. This causes a net decrease in global mRNA translation and induction of the integrated stress response (ISR), which promotes chemoresistance in AML. ISRIB (ISR inhibitor) sensitizes U2AF1-mutant cells to chemotherapy.\",\n      \"method\": \"Integrative analysis of RNA-seq and binding data from AML cell lines, single-cell RNA-seq, ISRIB pharmacological inhibition, patient multiomics data\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA-seq plus pharmacological rescue with ISRIB; validated in multiple AML datasets\",\n      \"pmids\": [\"38417135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"U2AF35-related protein Urp contacts the 3' splice site of both U12-type (minor class) and U2-type (major class) introns. For U12-type introns, Urp is recruited ATP-dependently to promote spliceosomal complex formation. For U2-type introns, Urp is specifically required for the second step of splicing. This establishes that through recognition of a common splicing element (3' splice site), Urp facilitates distinct steps of U2- and U12-type intron splicing.\",\n      \"method\": \"UV crosslinking, splicing complementation assays, spliceosomal complex assembly analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — crosslinking and functional complementation assays; single lab but multiple intron classes tested\",\n      \"pmids\": [\"21041408\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"U2AF1 (U2AF35) is the small subunit of the U2AF heterodimer that directly recognizes the conserved AG dinucleotide at the 3' splice site via its zinc finger domains; it stabilizes U2AF2 (U2AF65) binding to weak polypyrimidine tracts through a 'tongue-in-groove' heterodimerization interface, bridges SR protein enhancer complexes to U2AF65, and undergoes a conformational switch between closed and open states depending on polypyrimidine tract strength; cancer-associated mutations (S34F, Q157R) alter RNA-sequence specificity at the -3 and +1 positions of the 3' splice site, dysregulate alternative splicing of hundreds of genes (including IRAK4, ATG7, EIF4A2, H2AFY), and additionally impair a cytoplasmic translation-regulatory function of the protein, collectively contributing to MDS/AML pathogenesis through altered splicing, NMD attenuation, integrated stress response induction, and aberrant autophagy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"U2AF1 (U2AF35) is the small subunit of the U2AF splicing factor heterodimer that directly recognizes the conserved AG dinucleotide at the 3' splice site during early spliceosome assembly, a function established by site-specific UV crosslinking and in vitro genetic selection [#0, #1]. It is required for both constitutive and enhancer-dependent splicing, recruiting and stabilizing U2AF2 (U2AF65) on weak polypyrimidine tracts and bridging SR-protein enhancer complexes to U2AF65 [#2, #5, #6]. Structurally, U2AF1 engages U2AF65 through a 'tongue-in-groove' interface formed by reciprocal tryptophan residues between its atypical RRM and the U2AF65 proline-rich segment; this pseudo-RRM is unstructured in isolation and folds upon U2AF65 binding, while AG recognition is achieved through its zinc-finger domains [#3, #7, #19, #33]. The heterodimer governs 3' splice site selection through a conformational equilibrium of U2AF65 tandem RRMs between closed and open states, tuned by polypyrimidine-tract strength [#20]. Recurrent MDS/AML mutations in the zinc fingers (S34F, Q157R) establish aberrant RNA contacts at the -3 and +1 positions of the 3' splice site, shifting sequence specificity (e.g. preferential CAG over UAG recognition), compromising U2AF65-RNA interactions, and driving genome-wide intron retention, exon skipping, and altered hematopoiesis in vivo [#11, #12, #19, #21, #13]. These mutant-driven mis-splicing events converge on disease-relevant targets including IRAK4 (a longer myddosome-activating isoform), H2AFY (controlling EBF1 and B-cell output), EIF4A2 (NMD-triggered loss inducing the integrated stress response), and ATG7 (aberrant polyadenylation causing autophagy defects) [#17, #24, #34, #14]. Mutant U2AF1 additionally attenuates nonsense-mediated decay and exerts a splicing-independent cytoplasmic function, binding mature mRNA to negatively regulate translation [#26, #16, #33]. Recurrent mutations operate in a dosage-dependent, haplo-essential manner: the wild-type allele is required for survival of mutant hematopoietic cells [#15, #25].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that U2AF35 is functionally required for splicing and acts as a molecular bridge, resolving whether the small subunit had an essential role beyond merely partnering U2AF65.\",\n      \"evidence\": \"Nuclear extract depletion/complementation with recombinant U2AF35 and protein-RNA interaction assays\",\n      \"pmids\": [\"8647433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct RNA sequence recognized by U2AF35 not yet defined\", \"Structural basis of bridging unknown\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified the direct RNA target of U2AF35, showing it sequence-specifically contacts the 3' splice site AG and that this contact is critical for U2AF binding at weak polypyrimidine tracts.\",\n      \"evidence\": \"Site-specific UV crosslinking, in vitro genetic selection, splicing competition assays\",\n      \"pmids\": [\"10617206\", \"10617208\", \"10567551\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-level basis of AG recognition not resolved\", \"In vivo stoichiometry not established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the structural and mechanistic basis of heterodimerization and dual function, answering how U2AF35 and U2AF65 physically interact and how U2AF35 contributes beyond stabilizing U2AF65.\",\n      \"evidence\": \"X-ray crystallography of the core heterodimer, NMR of free/complexed RRM, depletion/complementation with truncation mutants\",\n      \"pmids\": [\"11551507\", \"11604503\", \"11421359\", \"12297299\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of zinc fingers bound to RNA not yet solved\", \"Downstream spliceosomal events triggered by U2AF35 unidentified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected 3' splice site recognition to tri-snRNP recruitment, addressing how the prespliceosome transitions toward later assembly.\",\n      \"evidence\": \"Co-immunoprecipitation, pulldowns, domain mapping of SPF30 bridging U2AF35 and hPrp3\",\n      \"pmids\": [\"18211889\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of disrupting the bridge not tested in vivo\", \"Single-lab interaction mapping\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked U2AF1 to human disease by identifying recurrent S34 zinc-finger mutations in MDS and demonstrating altered splicing, framing spliceosome mutation as a leukemia mechanism.\",\n      \"evidence\": \"Whole-genome sequencing of MDS patients and in vitro reporter splicing assays\",\n      \"pmids\": [\"22158538\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genome-wide splicing targets not yet mapped\", \"Causal contribution to hematopoiesis untested in vivo\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the molecular consequence of the mutations, showing they alter 3' splice site sequence preference at specific nucleotide positions and reprogram splicing in a zinc-finger-specific manner.\",\n      \"evidence\": \"RNA-seq splice junction analysis, in vitro affinity-binding assays, cell culture expression, immunofluorescence\",\n      \"pmids\": [\"25267526\", \"25311244\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic basis of changed specificity not yet visualized\", \"Causal disease phenotypes from these splicing changes unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated in vivo that mutant U2AF1 drives genome-wide splicing changes and perturbs hematopoiesis, moving from cell-culture inference to organismal phenotype.\",\n      \"evidence\": \"Doxycycline-inducible S34F transgenic mouse model with whole-transcriptome RNA-seq\",\n      \"pmids\": [\"25965570\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific mis-spliced targets drive phenotype not isolated\", \"Full leukemic transformation not recapitulated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed mutant effects scale with mutant:wild-type ratio and are explained by altered binding affinity, and uncovered an alternative-polyadenylation mechanism on ATG7 causing autophagy defects.\",\n      \"evidence\": \"Endogenous-locus genetic modification, quantitative RNA-seq, in vitro binding, 3'RACE, western blot, patient validation, xenografts\",\n      \"pmids\": [\"27776121\", \"27184077\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality of polyadenylation-based mechanism across targets unclear\", \"Dependence on wild-type allele mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Expanded U2AF1 function beyond splicing by demonstrating a cytoplasmic translation-regulatory role and identified disease-relevant mis-spliced effectors (IRAK4, IL-8, ROS1).\",\n      \"evidence\": \"Cytoplasmic CLIP-seq, polysome profiling, proteomics, in vivo metastasis assays, patient RNA-seq with IRAK4 inhibitor experiments, isoform interactome analysis\",\n      \"pmids\": [\"30842218\", \"31011167\", \"31836708\", \"31504847\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of translational repression on mRNA not defined\", \"Relative disease contribution of splicing vs translation roles unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided atomic and dynamic mechanism for 3' splice site selection, revealing how mutations alter RNA contacts and how the heterodimer samples closed/open conformations tuned by tract strength.\",\n      \"evidence\": \"X-ray crystallography of WT and mutant U2AF1-RNA complexes, single-molecule FRET with structure-guided mutagenesis, zinc-finger domain dissection, RAD51 mis-splicing assays\",\n      \"pmids\": [\"32958768\", \"32343311\", \"32116123\", \"35434831\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational dynamics in intact spliceosome not captured\", \"Therapeutic exploitation of DNA-damage sensitivity not validated clinically\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Integrated the mutant pathomechanism across genomic instability, dosage dependence, and specific lineage defects, establishing wild-type allele haplo-essentiality and downstream NMD, stress-granule, and B-cell phenotypes.\",\n      \"evidence\": \"Single-nucleotide CLIP, conditional WT-allele knockout in mutant background, CRISPR NMD screen with RNase H1 rescue, transgenic H2afy rescue with ChIP, polysome/NPM1 depletion assays\",\n      \"pmids\": [\"35303483\", \"34546980\", \"34215620\", \"34469727\", \"33137094\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between mutant splicing and stress-granule induction incomplete\", \"How wild-type allele rescues survival mechanistically unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a chromatin/cotranscriptional role through direct R-loop and G4 binding and phase separation, connecting U2AF1 occupancy at promoters to RNA Pol II distribution and splicing.\",\n      \"evidence\": \"ChIP-seq overlap, in vitro binding and phase-separation assays, Pol II ChIP-seq\",\n      \"pmids\": [\"37733759\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of phase separation to splicing not established\", \"Single-lab finding awaiting orthogonal confirmation\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected mutant splicing to a therapeutically actionable stress phenotype, showing EIF4A2 mis-splicing reduces global translation and induces the integrated stress response promoting chemoresistance.\",\n      \"evidence\": \"Integrative RNA-seq/binding analysis in AML cell lines, single-cell RNA-seq, ISRIB pharmacological inhibition, patient multiomics\",\n      \"pmids\": [\"38417135\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of EIF4A2 vs other ISR triggers not isolated\", \"Clinical efficacy of ISR inhibition unvalidated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How U2AF1's distinct nuclear splicing, chromatin/R-loop, and cytoplasmic translational activities are coordinated, and why mutant cells remain dependent on the wild-type allele, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model integrating splicing, translation, and R-loop functions\", \"Molecular basis of wild-type allele dependence unknown\", \"Mechanism linking mutant splicing to stress-response activation incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 1, 12, 16, 18, 21, 30]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [30]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 2, 35]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [16, 33]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [16, 33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 2, 11, 35]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [30]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [16, 34]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [10, 13, 17, 34]}\n    ],\n    \"complexes\": [\n      \"U2AF heterodimer (U2AF1/U2AF2)\"\n    ],\n    \"partners\": [\n      \"U2AF2\",\n      \"SPF30\",\n      \"hPrp3\",\n      \"U2AF1 (self)\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}