{"gene":"ENY2","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2004,"finding":"Sus1 (ENY2) is a component of both the SAGA histone acetyltransferase complex and the nuclear pore-associated Sac3-Thp1 mRNA export complex; it localizes to the nucleus with concentration at nuclear pores, associates with the promoter of a SAGA-dependent gene during transcription activation (ChIP), and its deletion impairs mRNA export.","method":"Biochemical co-purification, chromatin immunoprecipitation (ChIP), DNA macroarray, fluorescence microscopy","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-purification with two distinct complexes, ChIP, and functional mRNA export assay; foundational paper replicated by multiple subsequent studies","pmids":["14718168"],"is_preprint":false},{"year":2006,"finding":"Sus1 (ENY2) participates in SAGA-dependent histone H2B deubiquitylation and maintenance of normal H3 methylation levels; its binding to SAGA depends on Ubp8 and Sgf11, and a stable Sus1-Sgf11-Ubp8 subcomplex can be dissociated from SAGA under high-salt conditions. In vivo recruitment of Sus1 to the GAL1 promoter requires Ubp8, and vice versa.","method":"Deletion analysis, co-immunoprecipitation, ChIP, histone modification assays, salt dissociation of subcomplexes","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, ChIP, histone modification assays), replicated by structural and mutagenesis studies","pmids":["16855026"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of Sus1 bound to the Sac3 CID domain and Cdc31 revealed that Sus1 adopts an articulated helical hairpin fold that wraps around an extended alpha-helix in Sac3. Two Sus1 chains and one Cdc31 are present per Sac3 CID. Engineered mutations disrupting individual chain binding showed Sus1 and Cdc31 function synergistically to promote NPC association of TREX-2 and mRNA nuclear export.","method":"X-ray crystallography, structure-guided mutagenesis, in vivo NPC association assays, mRNA export assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis and functional in vivo validation","pmids":["19328066"],"is_preprint":false},{"year":2009,"finding":"Crystal structure of Sus1 bound to the N-terminal region of Sgf11 showed Sus1 wraps around a Sgf11 alpha-helix using a hydrophobic stripe mechanism similar to but narrower than the Sus1-Sac3 interface. A single Sus1 molecule cannot bind Sgf11 and Sac3 simultaneously, indicating Sus1 forms separate subcomplexes within SAGA and TREX-2.","method":"X-ray crystallography, in vitro mutagenesis disrupting the Sgf11-Sus1 interface","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis; mutually exclusive binding to Sgf11 and Sac3 structurally demonstrated","pmids":["20007317"],"is_preprint":false},{"year":2009,"finding":"Mutagenesis of Sus1 identified alleles (sus1-10, sus1-12) that dissociate Sus1 from TREX-2 while leaving SAGA interaction largely intact, and an allele (sus1-11) that impairs binding to both complexes. In vitro binding confirmed reduced affinity toward Sac3 and Sgf11 respectively. All three mutants were impaired in targeting TREX-2/Sac3 to nuclear pore complexes and showed mRNA export defects in vivo.","method":"Site-directed mutagenesis, in vitro binding assays, genetic interaction analysis, nuclear mRNA export assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — mutagenesis with in vitro binding and in vivo functional validation across multiple alleles","pmids":["19269973"],"is_preprint":false},{"year":2008,"finding":"Sus1 is required for transcription elongation and is associated with the elongating form of RNA Polymerase II phosphorylated on Ser5 and Ser2 of the CTD. Sus1 copurifies with mRNA export factors Yra1 and Mex67. ChIP shows Sus1 present at coding regions in a manner stimulated by Kin28-dependent CTD phosphorylation. Sgf73 is necessary for association of Sus1 with both SAGA and TREX-2.","method":"Co-immunoprecipitation, ChIP (coding regions and UAS), co-purification with export factors","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, ChIP at coding regions, co-purification) in a single study, replicated by other labs","pmids":["18923079"],"is_preprint":false},{"year":2008,"finding":"Thp1, Sac3, Sus1, and Cdc31 form a functional unit (THSC complex) with a role in mRNP biogenesis and genome integrity that is independent of SAGA. R-loop formation is consistent with genome instability in THSC mutants, analogous to THO/TREX mutants, defining a pathway connecting transcription elongation with mRNA export.","method":"Genetic epistasis, R-loop-forming constructs (ribozyme-containing transcription units), RNase H suppression, activation-induced cytidine deaminase assays","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with multiple orthogonal approaches, single lab","pmids":["18667528"],"is_preprint":false},{"year":2007,"finding":"Drosophila E(y)2/Sus1 is recruited to Su(Hw) insulators via direct binding to the zinc-finger domain of Su(Hw). Partial inactivation of E(y)2 (e(y)2^u1 mutation) impairs barrier activity but not enhancer-blocking activity of Su(Hw) insulators. Combining su(Hw)^- and e(y)2^u1 is lethal, demonstrating functional interaction in vivo.","method":"In vivo transgenic insulator assays, genetic interaction (lethality in double mutant), protein-protein interaction studies","journal":"Molecular cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo functional assays with genetic interaction and binding domain mapping, single lab","pmids":["17643381"],"is_preprint":false},{"year":2010,"finding":"Drosophila ENY2 is stably associated with the THO complex (involved in mRNP biogenesis), functioning independently of SAGA and AMEX. ENY2 and THO are recruited to the transcribed region of hsp70 by loading onto nascent mRNA (not via direct association with elongating RNA Pol II). ENY2 plays an important role in THO recruitment to nascent mRNA. Knockdown of either ENY2 or THO (but not SAGA or AMEX) affects 3' end processing of the transcript.","method":"Co-immunoprecipitation, ChIP, RNA immunoprecipitation, RNAi knockdown, nascent mRNA loading assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, ChIP, RNA-IP, and RNAi with specific phenotypic readout (3'-end processing), multiple orthogonal methods","pmids":["20048002"],"is_preprint":false},{"year":2007,"finding":"Sus1, Sac3, and Thp1 are required for the persistent tethering of mRNA foci (containing improperly processed mRNP) to cognate genes, and for the prolonged post-transcriptional association of activated GAL genes with the nuclear periphery after transcriptional shutoff.","method":"Fluorescence microscopy, genetic deletion analysis, live-cell imaging of mRNA foci","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence (gene-nuclear periphery tethering), single lab","pmids":["18003937"],"is_preprint":false},{"year":2016,"finding":"In human cells, depletion of the non-enzymatic SAGA DUBm components ATXN7L3 or ENY2 results in increased global H2Bub1 levels (in contrast to USP22 depletion which reduces H2Bub1). ENY2 and ATXN7L3 are shared subunits that coordinate activities of multiple H2B deubiquitinases including USP22 (SAGA), USP27X and USP51 (which function independently of SAGA); USP27X and USP51 require ATXN7L3 and ENY2 for their deubiquitinase activity.","method":"siRNA knockdown, histone modification assays (H2Bub1 levels), co-immunoprecipitation, identification of novel DUB complexes","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (knockdown, Co-IP, histone assays), discovery of two novel DUBs, rigorous controls showing contrasting effects of USP22 vs. ENY2 depletion","pmids":["27132940"],"is_preprint":false},{"year":2014,"finding":"Drosophila ENY2 is recruited to the zinc-finger domain of dCTCF and is required for the barrier activity of dCTCF-dependent insulators. ENY2 RNAi in BG3 cells leads to spreading of H3K27 trimethylation and Pc protein at several dCTCF boundaries.","method":"RNAi knockdown, ChIP (H3K27me3 and Pc spreading), transgenic insulator assays, protein-protein interaction","journal":"Epigenetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi with ChIP readout and transgenic functional assay, single lab","pmids":["25147918"],"is_preprint":false},{"year":2013,"finding":"In human TREX-2, ENY2 is NOT involved in nuclear protein export (negative result), in contrast to PCID2 and centrin 2. siRNA knockdown of ENY2 did not affect the rate of nuclear protein export.","method":"siRNA knockdown, nuclear protein export assays, immunofluorescence","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct siRNA KD with quantitative export assay; negative finding explicitly confirmed","pmids":["24291146"],"is_preprint":false},{"year":2022,"finding":"Sus1 function in lifespan control operates through the TREX-2 complex (mRNA export) rather than the SAGA DUB module. Sus1 is required for proper association of mRNA export factors Mex67 and Dbp5 with the nuclear rim; increased dosage of Mex67 and Dbp5 rescues growth defects, shortened lifespan, and nuclear poly(A)+ RNA accumulation in sus1Δ cells.","method":"Genetic epistasis (lifespan assays in double mutants), fluorescence microscopy (poly(A)+ RNA accumulation), dosage suppression","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with dosage suppression and localization assays, single lab","pmids":["35771153"],"is_preprint":false},{"year":2017,"finding":"Sus1 deletion leads to elongated telomeres in yeast. Sus1 physically and genetically interacts with telomere maintenance factors. The elevated H2BK123ub1 levels in sus1Δ mutants correlate with telomere elongation, suggesting Sus1's role as a H2B deubiquitination modulator negatively regulates telomere length.","method":"Telomere length assays (Southern blot), co-immunoprecipitation, histone modification assays (H2BK123ub1), genetic epistasis with telomere mutants","journal":"Current genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple assays (telomere length, H2B ubiquitination, Co-IP, epistasis) in a single lab study","pmids":["29116388"],"is_preprint":false},{"year":2010,"finding":"Sus1 has genetic interactions with P-body components (PAT1, LSM1, LSM6, DHH1); SUS1 deletion is synthetic lethal with LSM1 and PAT1. Sus1 overexpression leads to its accumulation in cytoplasmic granules that co-localize with P-bodies and stress granules. Novel physical interactions between Sus1 and P-body/stress granule factors were identified.","method":"Genetic interaction (synthetic lethality), co-immunoprecipitation, fluorescence microscopy (co-localization with P-body markers)","journal":"BMC cell biology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — synthetic lethality plus co-IP and co-localization, single lab","pmids":["20230609"],"is_preprint":false},{"year":2014,"finding":"Histone chaperone Asf1 co-purifies with Sus1 (TREX-2) and SAGA subunits; reciprocally, Sus1 and Thp1 interact with Asf1. Sus1 and Thp1 affect levels of Asf1-dependent histone H3K56 acetylation and histone H3/H4 incorporation onto chromatin, revealing a functional link between Asf1 and TREX-2 in histone metabolism near the nuclear pore.","method":"Tandem affinity purification coupled to mass spectrometry (TAP-MS), reciprocal co-immunoprecipitation, histone modification assays","journal":"Nucleus (Austin, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TAP-MS plus reciprocal Co-IP and histone modification assays, single lab","pmids":["24824343"],"is_preprint":false},{"year":2016,"finding":"Drosophila ENY2 forms mutually exclusive complexes with insulator proteins (Su(Hw)/dCTCF) and with Sgf11 (SAGA component), suggesting competitive partitioning of ENY2 between the SAGA complex and insulator complexes.","method":"Co-immunoprecipitation, competition binding assays","journal":"Doklady. Biochemistry and biophysics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, co-IP only, short report format","pmids":["27417714"],"is_preprint":false},{"year":2018,"finding":"Drosophila ENY2 interacts with the ORC complex, specifically with ORC4 and ORC6 subunits directly.","method":"Co-immunoprecipitation, direct protein interaction assays","journal":"Doklady. Biochemistry and biophysics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method (co-IP/pulldown), short report","pmids":["30008099"],"is_preprint":false},{"year":2020,"finding":"Drosophila ENY2 interacts with RNA helicase MLE; this interaction was confirmed by independent methods and shown to be evolutionarily conserved and important for MLE function in both sexes.","method":"Co-immunoprecipitation, independent binding confirmation assays, genetic analysis","journal":"Doklady. Biochemistry and biophysics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, interaction confirmed by independent methods but limited mechanistic detail in abstract","pmids":["32130612"],"is_preprint":false},{"year":2024,"finding":"Drosophila Paip2 directly binds ENY2 in vitro and associates with the ENY2-containing TREX-2 complex in vivo. Both Paip2 and ENY2 localize to histone locus bodies (HLBs). Paip2 knockdown by RNAi reduces binding of TREX-2 subunits to histone mRNPs, indicating Paip2 participates in TREX-2 binding to histone mRNPs.","method":"Yeast two-hybrid, in vitro direct binding assay, co-immunoprecipitation, immunofluorescence (HLB localization), RNAi knockdown with mRNP binding assay","journal":"Molekuliarnaia biologiia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Y2H, in vitro binding, Co-IP, localization, RNAi functional readout), single lab","pmids":["39707855"],"is_preprint":false},{"year":2026,"finding":"ENY2 is present at the histone locus body (HLB) in Drosophila and associates with histone gene chromatin as part of SAGA, THO, and TREX-2 complexes. ENY2 and subunits of all three complexes interact with FLASH (a structural HLB component). TREX-2 interacts with histone mRNA and participates in its nuclear export.","method":"Immunofluorescence (polytene chromosomes), ChIP, co-immunoprecipitation with FLASH and mRNP particles","journal":"Doklady. Biochemistry and biophysics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, localization plus co-IP, limited mechanistic detail in abstract","pmids":["41912850"],"is_preprint":false},{"year":2026,"finding":"ENY2 depletion in cancer cells facilitates release of NPM1 into the nucleoplasm, impeding ribosomal subunit export and inducing nucleolar stress. Released NPM1 interacts with MDM2 within the nucleus to stabilize p53 protein levels, inhibiting tumor growth. In p53-mutant cells, ENY2 knockdown enhances RISC binding/silencing efficacy toward target mRNAs (p53-independent pathway).","method":"Co-IP, molecular docking, western blotting, ubiquitination assays, immunofluorescence, RNA sequencing, polysome profiling, in vivo/in vitro tumor growth assays","journal":"Cellular oncology (Dordrecht, Netherlands)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (co-IP, ubiquitination assay, polysome profiling, in vivo), single lab, novel mechanistic pathway","pmids":["41642454"],"is_preprint":false}],"current_model":"ENY2/Sus1 is an evolutionarily conserved multifunctional nuclear protein that acts as a shared subunit of at least three distinct complexes — the SAGA histone acetyltransferase/deubiquitinase co-activator, the TREX-2 (Sac3-Thp1-Sus1-Cdc31) mRNA export complex at the nuclear pore, and the THO transcription elongation complex — where it adopts an articulated helical hairpin fold that wraps around alpha-helical scaffolds in partner proteins (Sac3, Sgf11) in a mutually exclusive manner, thereby coupling histone H2B deubiquitination (via Ubp8/USP22 and, in metazoans, USP27X and USP51 whose activity depends on ENY2 and ATXN7L3), transcription elongation, and mRNA nuclear export; ENY2 also mediates gene gating to the nuclear periphery, modulates telomere length through H2BK123 ubiquitination, and in Drosophila is required for the barrier activity of Su(Hw)- and dCTCF-dependent chromatin insulators."},"narrative":{"mechanistic_narrative":"ENY2 (Sus1) is an evolutionarily conserved nuclear protein that functions as a small shared subunit coupling histone modification, transcription elongation, and mRNA nuclear export by partitioning between distinct multiprotein complexes [PMID:14718168, PMID:18923079]. It is a component of both the SAGA histone-modifying co-activator and the nuclear pore-associated Sac3-Thp1 (TREX-2/THSC) mRNA export complex, and its loss impairs mRNA export [PMID:14718168, PMID:18667528]. Within SAGA, ENY2 supports H2B deubiquitylation: its incorporation depends on Ubp8 and Sgf11, and in human cells it acts together with ATXN7L3 as a non-enzymatic subunit required for the activity of multiple H2B deubiquitinases — USP22 within SAGA, and USP27X and USP51 acting independently of it [PMID:16855026, PMID:27132940]. Structurally, ENY2 adopts an articulated helical hairpin that wraps around extended alpha-helices in Sac3 and in Sgf11 through a hydrophobic-stripe mechanism; because a single ENY2 molecule cannot engage both partners at once, it forms mutually exclusive SAGA and TREX-2 subcomplexes, and engineered mutations that selectively dissociate it from either partner disrupt TREX-2 targeting to nuclear pores and cause mRNA export defects [PMID:19328066, PMID:20007317, PMID:19269973]. ENY2 also associates with elongating Ser5/Ser2-phosphorylated RNA Pol II and with export factors, links transcription to mRNP biogenesis and genome integrity through suppression of R-loops, and mediates the tethering of active genes to the nuclear periphery [PMID:18923079, PMID:18667528, PMID:18003937]. In Drosophila, ENY2 is stably part of the THO complex where it drives recruitment to nascent mRNA and 3' end processing, and is recruited to Su(Hw)- and dCTCF-dependent chromatin insulators where it is required for barrier activity that blocks the spreading of H3K27me3/Polycomb [PMID:17643381, PMID:20048002, PMID:25147918]. ENY2 additionally modulates telomere length through its effect on H2BK123 ubiquitination [PMID:29116388].","teleology":[{"year":2004,"claim":"Established ENY2/Sus1 as a physical bridge shared between a histone-modifying co-activator and the mRNA export machinery, raising the question of how one protein couples transcription to export.","evidence":"Biochemical co-purification with SAGA and the Sac3-Thp1 complex, ChIP, and mRNA export assays in yeast","pmids":["14718168"],"confidence":"High","gaps":["Did not resolve whether the two associations are simultaneous or mutually exclusive","No structural basis for partner binding","Molecular function within each complex unclear"]},{"year":2006,"claim":"Defined the SAGA-side role of Sus1 in H2B deubiquitylation and showed its incorporation depends on Ubp8 and Sgf11, situating it in a dissociable DUB subcomplex.","evidence":"Deletion analysis, co-IP, ChIP at GAL1, histone modification assays, and high-salt subcomplex dissociation in yeast","pmids":["16855026"],"confidence":"High","gaps":["Catalytic contribution of Sus1 itself versus a purely structural role not separated","Did not address the export complex function"]},{"year":2008,"claim":"Connected Sus1 to transcription elongation and to the THSC/TREX-2 export pathway, defining a route linking elongation, mRNP biogenesis, and genome integrity.","evidence":"Co-IP with elongating Pol II and export factors, ChIP at coding regions, and R-loop/genetic epistasis assays in yeast","pmids":["18923079","18667528"],"confidence":"High","gaps":["Mechanism by which Sus1 promotes elongation not defined","Direct versus indirect association with Pol II CTD unresolved"]},{"year":2009,"claim":"Provided the structural and mutational basis for ENY2's mutually exclusive partitioning, explaining how a single protein serves two complexes.","evidence":"X-ray crystallography of Sus1 with Sac3-CID/Cdc31 and with Sgf11, plus structure-guided and allele-specific mutagenesis with in vivo export and NPC-association assays in yeast","pmids":["19328066","20007317","19269973"],"confidence":"High","gaps":["Regulation governing complex choice in vivo not established","Stoichiometric switching dynamics unknown"]},{"year":2010,"claim":"Showed in metazoans that ENY2 is a stable THO subunit driving recruitment to nascent mRNA and 3' end processing, distinguishing this role from SAGA.","evidence":"Reciprocal co-IP, ChIP, RNA-IP, and RNAi with 3'-end processing readout in Drosophila","pmids":["20048002"],"confidence":"High","gaps":["How ENY2 mediates THO loading onto nascent RNA molecularly is unclear","Conservation of the 3'-processing role to yeast/human untested here"]},{"year":2014,"claim":"Extended ENY2's chromatin-boundary function to dCTCF insulators, linking it to prevention of Polycomb/H3K27me3 spreading.","evidence":"RNAi, ChIP for H3K27me3 and Pc spreading, and transgenic insulator assays in Drosophila","pmids":["25147918","17643381"],"confidence":"Medium","gaps":["Whether barrier activity uses SAGA DUB or a separate ENY2 function not resolved","Single-lab insulator system"]},{"year":2016,"claim":"Defined ENY2 as a non-enzymatic activator shared across multiple H2B deubiquitinases beyond SAGA, generalizing its DUB-supporting role in human cells.","evidence":"siRNA knockdown with H2Bub1 measurement and co-IP identifying USP22/USP27X/USP51 complexes in human cells","pmids":["27132940"],"confidence":"High","gaps":["Structural basis for ENY2 activation of USP27X/USP51 not determined","Biological substrates/contexts of the non-SAGA DUBs not mapped"]},{"year":2017,"claim":"Linked ENY2-dependent H2B ubiquitination control to telomere length regulation.","evidence":"Telomere Southern blots, H2BK123ub1 assays, co-IP, and genetic epistasis with telomere factors in yeast","pmids":["29116388"],"confidence":"Medium","gaps":["Causal chain from H2Bub1 to telomere length is correlative","Single lab"]},{"year":2013,"claim":"Clarified that the human TREX-2 role of ENY2 is mRNA-specific and not required for nuclear protein export, narrowing its functional scope.","evidence":"siRNA knockdown with quantitative nuclear protein export assays in human cells (negative result)","pmids":["24291146"],"confidence":"Medium","gaps":["Does not address mRNA export contribution in human cells","Single-pathway readout"]},{"year":2022,"claim":"Attributed a physiological lifespan/growth phenotype specifically to the TREX-2 export function of Sus1 rather than the SAGA DUB module.","evidence":"Lifespan epistasis, poly(A)+ RNA imaging, and Mex67/Dbp5 dosage suppression in yeast","pmids":["35771153"],"confidence":"Medium","gaps":["Mechanistic link between export defect and aging not detailed","Single lab"]},{"year":2024,"claim":"Connected ENY2/TREX-2 to histone mRNP biology via a direct Paip2 interaction at histone locus bodies.","evidence":"Y2H, in vitro binding, co-IP, HLB immunofluorescence, and RNAi mRNP-binding assays in Drosophila","pmids":["39707855","41912850"],"confidence":"Medium","gaps":["Functional consequence for histone mRNA export quantitatively limited","HLB recruitment mechanism incompletely defined"]},{"year":2026,"claim":"Proposed a cancer-relevant role in which ENY2 loss perturbs nucleolar/NPM1 dynamics to stabilize p53 and restrain tumor growth.","evidence":"Co-IP, ubiquitination assays, polysome profiling, RNA-seq, and in vivo tumor assays in cancer cells","pmids":["41642454"],"confidence":"Medium","gaps":["Mechanistic link between TREX-2/SAGA functions and NPM1 release not fully resolved","Single lab, requires independent confirmation"]},{"year":null,"claim":"How ENY2's partitioning between SAGA, TREX-2, THO, and chromatin-boundary complexes is regulated in vivo, and how these functions are coordinated within a single cell, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No mechanism governing complex-choice switching","Quantitative partitioning across complexes unmeasured","Integration of telomere, insulator, and export roles unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,3,4]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[10,1]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[8]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[15]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,6,8]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[1,10,11]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[5,0]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[2,4]}],"complexes":["SAGA","TREX-2 (THSC)","THO","SAGA DUB module"],"partners":["SAC3","SGF11","CDC31","UBP8","ATXN7L3","THP1","SU(HW)","DCTCF"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NPA8","full_name":"Transcription and mRNA export factor ENY2","aliases":["Enhancer of yellow 2 transcription factor homolog"],"length_aa":101,"mass_kda":11.5,"function":"Involved in mRNA export coupled transcription activation by association with both the TREX-2 and the SAGA complexes. The transcription regulatory histone acetylation (HAT) complex SAGA is a multiprotein complex that activates transcription by remodeling chromatin and mediating histone acetylation and deubiquitination. Within the SAGA complex, participates in a subcomplex that specifically deubiquitinates both histones H2A and H2B. The SAGA complex is recruited to specific gene promoters by activators such as MYC, where it is required for transcription. Required for nuclear receptor-mediated transactivation (PubMed:18206972, PubMed:21746879). As a component of the TREX-2 complex, involved in the export of mRNAs to the cytoplasm through the nuclear pores (PubMed:23591820)","subcellular_location":"Nucleus, nucleoplasm","url":"https://www.uniprot.org/uniprotkb/Q9NPA8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ENY2","classification":"Not Classified","n_dependent_lines":287,"n_total_lines":1208,"dependency_fraction":0.23758278145695363},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000120533","cell_line_id":"CID001798","localizations":[{"compartment":"nuclear_membrane","grade":3},{"compartment":"nuclear_punctae","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"RPLP1","stoichiometry":10.0},{"gene":"RPLP2","stoichiometry":10.0},{"gene":"RPLP0;RPLP0P6","stoichiometry":10.0},{"gene":"RPL22","stoichiometry":10.0},{"gene":"RPL3","stoichiometry":10.0},{"gene":"RPS19","stoichiometry":10.0},{"gene":"RPL13A;RPL13A","stoichiometry":10.0},{"gene":"RPL21","stoichiometry":10.0},{"gene":"RPL5","stoichiometry":10.0},{"gene":"RPL34","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID001798","total_profiled":1310},"omim":[{"mim_id":"619015","title":"ENY2 TRANSCRIPTION AND EXPORT COMPLEX 2 SUBUNIT; ENY2","url":"https://www.omim.org/entry/619015"},{"mim_id":"619010","title":"ATXN7-LIKE 3; ATXN7L3","url":"https://www.omim.org/entry/619010"},{"mim_id":"612116","title":"UBIQUITIN-SPECIFIC PROTEASE 22; USP22","url":"https://www.omim.org/entry/612116"},{"mim_id":"147640","title":"INTERFERON, BETA-1; IFNB1","url":"https://www.omim.org/entry/147640"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Mitochondria","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ENY2"},"hgnc":{"alias_symbol":["DC6","FLJ20480","Sus1"],"prev_symbol":[]},"alphafold":{"accession":"Q9NPA8","domains":[{"cath_id":"1.10.246.140","chopping":"1-101","consensus_level":"medium","plddt":93.6728,"start":1,"end":101}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NPA8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NPA8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NPA8-F1-predicted_aligned_error_v6.png","plddt_mean":93.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ENY2","jax_strain_url":"https://www.jax.org/strain/search?query=ENY2"},"sequence":{"accession":"Q9NPA8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NPA8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NPA8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NPA8"}},"corpus_meta":[{"pmid":"14718168","id":"PMC_14718168","title":"Sus1, a functional 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In vivo recruitment of Sus1 to the GAL1 promoter requires Ubp8, and vice versa.\",\n      \"method\": \"Deletion analysis, co-immunoprecipitation, ChIP, histone modification assays, salt dissociation of subcomplexes\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, ChIP, histone modification assays), replicated by structural and mutagenesis studies\",\n      \"pmids\": [\"16855026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of Sus1 bound to the Sac3 CID domain and Cdc31 revealed that Sus1 adopts an articulated helical hairpin fold that wraps around an extended alpha-helix in Sac3. Two Sus1 chains and one Cdc31 are present per Sac3 CID. Engineered mutations disrupting individual chain binding showed Sus1 and Cdc31 function synergistically to promote NPC association of TREX-2 and mRNA nuclear export.\",\n      \"method\": \"X-ray crystallography, structure-guided mutagenesis, in vivo NPC association assays, mRNA export assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis and functional in vivo validation\",\n      \"pmids\": [\"19328066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Crystal structure of Sus1 bound to the N-terminal region of Sgf11 showed Sus1 wraps around a Sgf11 alpha-helix using a hydrophobic stripe mechanism similar to but narrower than the Sus1-Sac3 interface. A single Sus1 molecule cannot bind Sgf11 and Sac3 simultaneously, indicating Sus1 forms separate subcomplexes within SAGA and TREX-2.\",\n      \"method\": \"X-ray crystallography, in vitro mutagenesis disrupting the Sgf11-Sus1 interface\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis; mutually exclusive binding to Sgf11 and Sac3 structurally demonstrated\",\n      \"pmids\": [\"20007317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Mutagenesis of Sus1 identified alleles (sus1-10, sus1-12) that dissociate Sus1 from TREX-2 while leaving SAGA interaction largely intact, and an allele (sus1-11) that impairs binding to both complexes. In vitro binding confirmed reduced affinity toward Sac3 and Sgf11 respectively. All three mutants were impaired in targeting TREX-2/Sac3 to nuclear pore complexes and showed mRNA export defects in vivo.\",\n      \"method\": \"Site-directed mutagenesis, in vitro binding assays, genetic interaction analysis, nuclear mRNA export assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — mutagenesis with in vitro binding and in vivo functional validation across multiple alleles\",\n      \"pmids\": [\"19269973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Sus1 is required for transcription elongation and is associated with the elongating form of RNA Polymerase II phosphorylated on Ser5 and Ser2 of the CTD. Sus1 copurifies with mRNA export factors Yra1 and Mex67. ChIP shows Sus1 present at coding regions in a manner stimulated by Kin28-dependent CTD phosphorylation. Sgf73 is necessary for association of Sus1 with both SAGA and TREX-2.\",\n      \"method\": \"Co-immunoprecipitation, ChIP (coding regions and UAS), co-purification with export factors\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, ChIP at coding regions, co-purification) in a single study, replicated by other labs\",\n      \"pmids\": [\"18923079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Thp1, Sac3, Sus1, and Cdc31 form a functional unit (THSC complex) with a role in mRNP biogenesis and genome integrity that is independent of SAGA. R-loop formation is consistent with genome instability in THSC mutants, analogous to THO/TREX mutants, defining a pathway connecting transcription elongation with mRNA export.\",\n      \"method\": \"Genetic epistasis, R-loop-forming constructs (ribozyme-containing transcription units), RNase H suppression, activation-induced cytidine deaminase assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with multiple orthogonal approaches, single lab\",\n      \"pmids\": [\"18667528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Drosophila E(y)2/Sus1 is recruited to Su(Hw) insulators via direct binding to the zinc-finger domain of Su(Hw). Partial inactivation of E(y)2 (e(y)2^u1 mutation) impairs barrier activity but not enhancer-blocking activity of Su(Hw) insulators. Combining su(Hw)^- and e(y)2^u1 is lethal, demonstrating functional interaction in vivo.\",\n      \"method\": \"In vivo transgenic insulator assays, genetic interaction (lethality in double mutant), protein-protein interaction studies\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo functional assays with genetic interaction and binding domain mapping, single lab\",\n      \"pmids\": [\"17643381\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Drosophila ENY2 is stably associated with the THO complex (involved in mRNP biogenesis), functioning independently of SAGA and AMEX. ENY2 and THO are recruited to the transcribed region of hsp70 by loading onto nascent mRNA (not via direct association with elongating RNA Pol II). ENY2 plays an important role in THO recruitment to nascent mRNA. Knockdown of either ENY2 or THO (but not SAGA or AMEX) affects 3' end processing of the transcript.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, RNA immunoprecipitation, RNAi knockdown, nascent mRNA loading assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, ChIP, RNA-IP, and RNAi with specific phenotypic readout (3'-end processing), multiple orthogonal methods\",\n      \"pmids\": [\"20048002\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Sus1, Sac3, and Thp1 are required for the persistent tethering of mRNA foci (containing improperly processed mRNP) to cognate genes, and for the prolonged post-transcriptional association of activated GAL genes with the nuclear periphery after transcriptional shutoff.\",\n      \"method\": \"Fluorescence microscopy, genetic deletion analysis, live-cell imaging of mRNA foci\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence (gene-nuclear periphery tethering), single lab\",\n      \"pmids\": [\"18003937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In human cells, depletion of the non-enzymatic SAGA DUBm components ATXN7L3 or ENY2 results in increased global H2Bub1 levels (in contrast to USP22 depletion which reduces H2Bub1). ENY2 and ATXN7L3 are shared subunits that coordinate activities of multiple H2B deubiquitinases including USP22 (SAGA), USP27X and USP51 (which function independently of SAGA); USP27X and USP51 require ATXN7L3 and ENY2 for their deubiquitinase activity.\",\n      \"method\": \"siRNA knockdown, histone modification assays (H2Bub1 levels), co-immunoprecipitation, identification of novel DUB complexes\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (knockdown, Co-IP, histone assays), discovery of two novel DUBs, rigorous controls showing contrasting effects of USP22 vs. ENY2 depletion\",\n      \"pmids\": [\"27132940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Drosophila ENY2 is recruited to the zinc-finger domain of dCTCF and is required for the barrier activity of dCTCF-dependent insulators. ENY2 RNAi in BG3 cells leads to spreading of H3K27 trimethylation and Pc protein at several dCTCF boundaries.\",\n      \"method\": \"RNAi knockdown, ChIP (H3K27me3 and Pc spreading), transgenic insulator assays, protein-protein interaction\",\n      \"journal\": \"Epigenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi with ChIP readout and transgenic functional assay, single lab\",\n      \"pmids\": [\"25147918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In human TREX-2, ENY2 is NOT involved in nuclear protein export (negative result), in contrast to PCID2 and centrin 2. siRNA knockdown of ENY2 did not affect the rate of nuclear protein export.\",\n      \"method\": \"siRNA knockdown, nuclear protein export assays, immunofluorescence\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct siRNA KD with quantitative export assay; negative finding explicitly confirmed\",\n      \"pmids\": [\"24291146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Sus1 function in lifespan control operates through the TREX-2 complex (mRNA export) rather than the SAGA DUB module. Sus1 is required for proper association of mRNA export factors Mex67 and Dbp5 with the nuclear rim; increased dosage of Mex67 and Dbp5 rescues growth defects, shortened lifespan, and nuclear poly(A)+ RNA accumulation in sus1Δ cells.\",\n      \"method\": \"Genetic epistasis (lifespan assays in double mutants), fluorescence microscopy (poly(A)+ RNA accumulation), dosage suppression\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with dosage suppression and localization assays, single lab\",\n      \"pmids\": [\"35771153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Sus1 deletion leads to elongated telomeres in yeast. Sus1 physically and genetically interacts with telomere maintenance factors. The elevated H2BK123ub1 levels in sus1Δ mutants correlate with telomere elongation, suggesting Sus1's role as a H2B deubiquitination modulator negatively regulates telomere length.\",\n      \"method\": \"Telomere length assays (Southern blot), co-immunoprecipitation, histone modification assays (H2BK123ub1), genetic epistasis with telomere mutants\",\n      \"journal\": \"Current genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple assays (telomere length, H2B ubiquitination, Co-IP, epistasis) in a single lab study\",\n      \"pmids\": [\"29116388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Sus1 has genetic interactions with P-body components (PAT1, LSM1, LSM6, DHH1); SUS1 deletion is synthetic lethal with LSM1 and PAT1. Sus1 overexpression leads to its accumulation in cytoplasmic granules that co-localize with P-bodies and stress granules. Novel physical interactions between Sus1 and P-body/stress granule factors were identified.\",\n      \"method\": \"Genetic interaction (synthetic lethality), co-immunoprecipitation, fluorescence microscopy (co-localization with P-body markers)\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — synthetic lethality plus co-IP and co-localization, single lab\",\n      \"pmids\": [\"20230609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Histone chaperone Asf1 co-purifies with Sus1 (TREX-2) and SAGA subunits; reciprocally, Sus1 and Thp1 interact with Asf1. Sus1 and Thp1 affect levels of Asf1-dependent histone H3K56 acetylation and histone H3/H4 incorporation onto chromatin, revealing a functional link between Asf1 and TREX-2 in histone metabolism near the nuclear pore.\",\n      \"method\": \"Tandem affinity purification coupled to mass spectrometry (TAP-MS), reciprocal co-immunoprecipitation, histone modification assays\",\n      \"journal\": \"Nucleus (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TAP-MS plus reciprocal Co-IP and histone modification assays, single lab\",\n      \"pmids\": [\"24824343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Drosophila ENY2 forms mutually exclusive complexes with insulator proteins (Su(Hw)/dCTCF) and with Sgf11 (SAGA component), suggesting competitive partitioning of ENY2 between the SAGA complex and insulator complexes.\",\n      \"method\": \"Co-immunoprecipitation, competition binding assays\",\n      \"journal\": \"Doklady. Biochemistry and biophysics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, co-IP only, short report format\",\n      \"pmids\": [\"27417714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Drosophila ENY2 interacts with the ORC complex, specifically with ORC4 and ORC6 subunits directly.\",\n      \"method\": \"Co-immunoprecipitation, direct protein interaction assays\",\n      \"journal\": \"Doklady. Biochemistry and biophysics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method (co-IP/pulldown), short report\",\n      \"pmids\": [\"30008099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Drosophila ENY2 interacts with RNA helicase MLE; this interaction was confirmed by independent methods and shown to be evolutionarily conserved and important for MLE function in both sexes.\",\n      \"method\": \"Co-immunoprecipitation, independent binding confirmation assays, genetic analysis\",\n      \"journal\": \"Doklady. Biochemistry and biophysics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, interaction confirmed by independent methods but limited mechanistic detail in abstract\",\n      \"pmids\": [\"32130612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Drosophila Paip2 directly binds ENY2 in vitro and associates with the ENY2-containing TREX-2 complex in vivo. Both Paip2 and ENY2 localize to histone locus bodies (HLBs). Paip2 knockdown by RNAi reduces binding of TREX-2 subunits to histone mRNPs, indicating Paip2 participates in TREX-2 binding to histone mRNPs.\",\n      \"method\": \"Yeast two-hybrid, in vitro direct binding assay, co-immunoprecipitation, immunofluorescence (HLB localization), RNAi knockdown with mRNP binding assay\",\n      \"journal\": \"Molekuliarnaia biologiia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Y2H, in vitro binding, Co-IP, localization, RNAi functional readout), single lab\",\n      \"pmids\": [\"39707855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ENY2 is present at the histone locus body (HLB) in Drosophila and associates with histone gene chromatin as part of SAGA, THO, and TREX-2 complexes. ENY2 and subunits of all three complexes interact with FLASH (a structural HLB component). TREX-2 interacts with histone mRNA and participates in its nuclear export.\",\n      \"method\": \"Immunofluorescence (polytene chromosomes), ChIP, co-immunoprecipitation with FLASH and mRNP particles\",\n      \"journal\": \"Doklady. Biochemistry and biophysics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, localization plus co-IP, limited mechanistic detail in abstract\",\n      \"pmids\": [\"41912850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"ENY2 depletion in cancer cells facilitates release of NPM1 into the nucleoplasm, impeding ribosomal subunit export and inducing nucleolar stress. Released NPM1 interacts with MDM2 within the nucleus to stabilize p53 protein levels, inhibiting tumor growth. In p53-mutant cells, ENY2 knockdown enhances RISC binding/silencing efficacy toward target mRNAs (p53-independent pathway).\",\n      \"method\": \"Co-IP, molecular docking, western blotting, ubiquitination assays, immunofluorescence, RNA sequencing, polysome profiling, in vivo/in vitro tumor growth assays\",\n      \"journal\": \"Cellular oncology (Dordrecht, Netherlands)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (co-IP, ubiquitination assay, polysome profiling, in vivo), single lab, novel mechanistic pathway\",\n      \"pmids\": [\"41642454\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ENY2/Sus1 is an evolutionarily conserved multifunctional nuclear protein that acts as a shared subunit of at least three distinct complexes — the SAGA histone acetyltransferase/deubiquitinase co-activator, the TREX-2 (Sac3-Thp1-Sus1-Cdc31) mRNA export complex at the nuclear pore, and the THO transcription elongation complex — where it adopts an articulated helical hairpin fold that wraps around alpha-helical scaffolds in partner proteins (Sac3, Sgf11) in a mutually exclusive manner, thereby coupling histone H2B deubiquitination (via Ubp8/USP22 and, in metazoans, USP27X and USP51 whose activity depends on ENY2 and ATXN7L3), transcription elongation, and mRNA nuclear export; ENY2 also mediates gene gating to the nuclear periphery, modulates telomere length through H2BK123 ubiquitination, and in Drosophila is required for the barrier activity of Su(Hw)- and dCTCF-dependent chromatin insulators.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ENY2 (Sus1) is an evolutionarily conserved nuclear protein that functions as a small shared subunit coupling histone modification, transcription elongation, and mRNA nuclear export by partitioning between distinct multiprotein complexes [#0, #5]. It is a component of both the SAGA histone-modifying co-activator and the nuclear pore-associated Sac3-Thp1 (TREX-2/THSC) mRNA export complex, and its loss impairs mRNA export [#0, #6]. Within SAGA, ENY2 supports H2B deubiquitylation: its incorporation depends on Ubp8 and Sgf11, and in human cells it acts together with ATXN7L3 as a non-enzymatic subunit required for the activity of multiple H2B deubiquitinases — USP22 within SAGA, and USP27X and USP51 acting independently of it [#1, #10]. Structurally, ENY2 adopts an articulated helical hairpin that wraps around extended alpha-helices in Sac3 and in Sgf11 through a hydrophobic-stripe mechanism; because a single ENY2 molecule cannot engage both partners at once, it forms mutually exclusive SAGA and TREX-2 subcomplexes, and engineered mutations that selectively dissociate it from either partner disrupt TREX-2 targeting to nuclear pores and cause mRNA export defects [#2, #3, #4]. ENY2 also associates with elongating Ser5/Ser2-phosphorylated RNA Pol II and with export factors, links transcription to mRNP biogenesis and genome integrity through suppression of R-loops, and mediates the tethering of active genes to the nuclear periphery [#5, #6, #9]. In Drosophila, ENY2 is stably part of the THO complex where it drives recruitment to nascent mRNA and 3' end processing, and is recruited to Su(Hw)- and dCTCF-dependent chromatin insulators where it is required for barrier activity that blocks the spreading of H3K27me3/Polycomb [#7, #8, #11]. ENY2 additionally modulates telomere length through its effect on H2BK123 ubiquitination [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established ENY2/Sus1 as a physical bridge shared between a histone-modifying co-activator and the mRNA export machinery, raising the question of how one protein couples transcription to export.\",\n      \"evidence\": \"Biochemical co-purification with SAGA and the Sac3-Thp1 complex, ChIP, and mRNA export assays in yeast\",\n      \"pmids\": [\"14718168\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether the two associations are simultaneous or mutually exclusive\", \"No structural basis for partner binding\", \"Molecular function within each complex unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined the SAGA-side role of Sus1 in H2B deubiquitylation and showed its incorporation depends on Ubp8 and Sgf11, situating it in a dissociable DUB subcomplex.\",\n      \"evidence\": \"Deletion analysis, co-IP, ChIP at GAL1, histone modification assays, and high-salt subcomplex dissociation in yeast\",\n      \"pmids\": [\"16855026\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic contribution of Sus1 itself versus a purely structural role not separated\", \"Did not address the export complex function\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Connected Sus1 to transcription elongation and to the THSC/TREX-2 export pathway, defining a route linking elongation, mRNP biogenesis, and genome integrity.\",\n      \"evidence\": \"Co-IP with elongating Pol II and export factors, ChIP at coding regions, and R-loop/genetic epistasis assays in yeast\",\n      \"pmids\": [\"18923079\", \"18667528\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which Sus1 promotes elongation not defined\", \"Direct versus indirect association with Pol II CTD unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Provided the structural and mutational basis for ENY2's mutually exclusive partitioning, explaining how a single protein serves two complexes.\",\n      \"evidence\": \"X-ray crystallography of Sus1 with Sac3-CID/Cdc31 and with Sgf11, plus structure-guided and allele-specific mutagenesis with in vivo export and NPC-association assays in yeast\",\n      \"pmids\": [\"19328066\", \"20007317\", \"19269973\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Regulation governing complex choice in vivo not established\", \"Stoichiometric switching dynamics unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed in metazoans that ENY2 is a stable THO subunit driving recruitment to nascent mRNA and 3' end processing, distinguishing this role from SAGA.\",\n      \"evidence\": \"Reciprocal co-IP, ChIP, RNA-IP, and RNAi with 3'-end processing readout in Drosophila\",\n      \"pmids\": [\"20048002\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ENY2 mediates THO loading onto nascent RNA molecularly is unclear\", \"Conservation of the 3'-processing role to yeast/human untested here\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Extended ENY2's chromatin-boundary function to dCTCF insulators, linking it to prevention of Polycomb/H3K27me3 spreading.\",\n      \"evidence\": \"RNAi, ChIP for H3K27me3 and Pc spreading, and transgenic insulator assays in Drosophila\",\n      \"pmids\": [\"25147918\", \"17643381\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether barrier activity uses SAGA DUB or a separate ENY2 function not resolved\", \"Single-lab insulator system\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined ENY2 as a non-enzymatic activator shared across multiple H2B deubiquitinases beyond SAGA, generalizing its DUB-supporting role in human cells.\",\n      \"evidence\": \"siRNA knockdown with H2Bub1 measurement and co-IP identifying USP22/USP27X/USP51 complexes in human cells\",\n      \"pmids\": [\"27132940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for ENY2 activation of USP27X/USP51 not determined\", \"Biological substrates/contexts of the non-SAGA DUBs not mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Linked ENY2-dependent H2B ubiquitination control to telomere length regulation.\",\n      \"evidence\": \"Telomere Southern blots, H2BK123ub1 assays, co-IP, and genetic epistasis with telomere factors in yeast\",\n      \"pmids\": [\"29116388\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal chain from H2Bub1 to telomere length is correlative\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Clarified that the human TREX-2 role of ENY2 is mRNA-specific and not required for nuclear protein export, narrowing its functional scope.\",\n      \"evidence\": \"siRNA knockdown with quantitative nuclear protein export assays in human cells (negative result)\",\n      \"pmids\": [\"24291146\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address mRNA export contribution in human cells\", \"Single-pathway readout\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Attributed a physiological lifespan/growth phenotype specifically to the TREX-2 export function of Sus1 rather than the SAGA DUB module.\",\n      \"evidence\": \"Lifespan epistasis, poly(A)+ RNA imaging, and Mex67/Dbp5 dosage suppression in yeast\",\n      \"pmids\": [\"35771153\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between export defect and aging not detailed\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected ENY2/TREX-2 to histone mRNP biology via a direct Paip2 interaction at histone locus bodies.\",\n      \"evidence\": \"Y2H, in vitro binding, co-IP, HLB immunofluorescence, and RNAi mRNP-binding assays in Drosophila\",\n      \"pmids\": [\"39707855\", \"41912850\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence for histone mRNA export quantitatively limited\", \"HLB recruitment mechanism incompletely defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Proposed a cancer-relevant role in which ENY2 loss perturbs nucleolar/NPM1 dynamics to stabilize p53 and restrain tumor growth.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, polysome profiling, RNA-seq, and in vivo tumor assays in cancer cells\",\n      \"pmids\": [\"41642454\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between TREX-2/SAGA functions and NPM1 release not fully resolved\", \"Single lab, requires independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ENY2's partitioning between SAGA, TREX-2, THO, and chromatin-boundary complexes is regulated in vivo, and how these functions are coordinated within a single cell, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mechanism governing complex-choice switching\", \"Quantitative partitioning across complexes unmeasured\", \"Integration of telomere, insulator, and export roles unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 3, 4]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [10, 1]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 6, 8]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [1, 10, 11]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [5, 0]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [\n      \"SAGA\",\n      \"TREX-2 (THSC)\",\n      \"THO\",\n      \"SAGA DUB module\"\n    ],\n    \"partners\": [\n      \"Sac3\",\n      \"Sgf11\",\n      \"Cdc31\",\n      \"Ubp8\",\n      \"ATXN7L3\",\n      \"Thp1\",\n      \"Su(Hw)\",\n      \"dCTCF\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}