{"gene":"MEX3A","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2013,"finding":"MEX3A binds directly to a specific determinant in the CDX2 mRNA 3'UTR and represses CDX2 expression post-transcriptionally, thereby impairing intestinal differentiation, cellular polarization, and promoting expression of intestinal stem cell markers (LGR5, BMI1, MSI1).","method":"Cell-based assays (RNA-binding to CDX2 mRNA 3'UTR), expression studies in murine intestine, overexpression/knockdown experiments","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct RNA-binding to 3'UTR demonstrated, functional consequences validated in multiple cellular models and in vivo mouse intestine, multiple orthogonal methods in single study","pmids":["23408853"],"is_preprint":false},{"year":2017,"finding":"Mex3a expression marks a slowly cycling, reserve-like subpopulation of Lgr5+ intestinal stem cells (ISCs) that is spared by chemotherapy and radiation (which preferentially target rapidly dividing Lgr5+ cells) and helps regenerate the intestinal epithelium after toxic insults.","method":"Lineage tracing, single-cell transcriptome profiling, in vivo chemotherapy/radiation challenge models","journal":"Cell stem cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — lineage tracing combined with single-cell transcriptomics and in vivo injury models; replicated in subsequent independent studies","pmids":["28285904"],"is_preprint":false},{"year":2020,"finding":"MEX3A binds LAMA2 mRNA via RNA immunoprecipitation and promotes its instability/degradation in lung adenocarcinoma cells, thereby downregulating LAMA2 and activating PI3K/AKT signaling to promote metastasis.","method":"RNA immunoprecipitation (RIP), mRNA stability assay, knockdown/rescue experiments, transcriptome sequencing","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP assay and mRNA stability assay in single lab, functional rescue experiments performed","pmids":["32792503"],"is_preprint":false},{"year":2020,"finding":"MEX3A acts as an E3 ubiquitin ligase that binds RIG-I protein and induces its ubiquitylation and proteasome-dependent degradation in glioblastoma cells, suppressing RIG-I tumor suppressor function.","method":"Co-immunoprecipitation, ubiquitylation assay, proteasome inhibition, MEX3A knockdown with RIG-I protein level readout","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitylation assay in single lab; RING domain E3 ligase function inferred from domain architecture but ubiquitylation assay is direct","pmids":["32019099"],"is_preprint":false},{"year":2020,"finding":"Knockout of Mex3a in mice disrupts Lgr5+ ISC pool maintenance during postnatal intestinal development and impairs organoid maturation ex vivo. Mechanistically, Mex3a deletion induces PPARγ pathway activation with concomitant decrease in Wnt signalling and loss of Lgr5+ stem cell signature; high PPARγ signalling impairs Lgr5+ ISC function.","method":"Mex3a knockout mouse model, transcriptomic profiling of intestinal crypts, organoid assays, PPARγ pathway manipulation","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse model with transcriptomics, organoid phenotyping, and pharmacological PPARγ manipulation; multiple orthogonal methods","pmids":["32052574"],"is_preprint":false},{"year":2021,"finding":"MEX3A interacts with RAP1GAP protein (demonstrated by Co-IP) and regulates the RAP1GAP/MEK/ERK/HIF-1α pathway to promote colorectal cancer cell proliferation and metastasis; hsa-miR-6887-3p binds the 3'UTR of MEX3A mRNA to suppress its expression.","method":"Co-immunoprecipitation (Co-IP), transcriptome analysis, dual-luciferase reporter assay, MEK/ERK inhibitor rescue experiments","journal":"Cancer communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrates RAP1GAP interaction; pathway validated with specific inhibitor (U0126); single lab","pmids":["33638620"],"is_preprint":false},{"year":2021,"finding":"The human RNA chaperone MEX3A (hMex3A) binds the Andes orthohantavirus Small mRNA 3'UTR (identified by RNA affinity chromatography/mass spectrometry) and enhances SmRNA translation in a 3'UTR-dependent manner; hMex3A interacts with eIF4G independently of viral infection, suggesting a 5'-3' end interaction mechanism.","method":"RNA affinity chromatography followed by mass spectrometry, in vitro translation assay, co-immunoprecipitation (hMex3A-eIF4G interaction)","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro translation assay with 3'UTR-deletion controls, MS-based binding identification, and Co-IP; single lab but multiple orthogonal methods","pmids":["34547046"],"is_preprint":false},{"year":2022,"finding":"MEX3A binds to the MEX3 recognition element (MRE) in MSH2 mRNA 3'UTR and recruits CCR4-NOT complexes to induce MSH2 mRNA deadenylation and degradation, thereby reducing DNA mismatch repair activity and conferring temozolomide resistance in glioblastoma.","method":"RNA-binding assay (MRE identification), CCR4-NOT complex association assay, mRNA stability/deadenylation assay, MEX3A overexpression/depletion with MMR activity and chemosensitivity readouts","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — identified specific binding element in MSH2 mRNA, demonstrated CCR4-NOT recruitment, measured mRNA deadenylation, and functional DNA MMR assay; multiple orthogonal methods in single rigorous study","pmids":["36112059"],"is_preprint":false},{"year":2022,"finding":"MEX3A overexpression in ovarian cancer cells promotes p53 protein degradation without altering p53 mRNA levels; MEX3A-mediated p53 degradation is critical for suppressing ferroptosis and enhancing tumorigenesis. MEX3A contains a RING finger domain (E3 ubiquitin ligase) and an RNA-binding domain.","method":"MEX3A depletion/overexpression with p53 protein stability assay, p53 mRNA level measurement (unchanged), ferroptosis assays, orthotopic xenograft models, p53 knockdown rescue experiments","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal assays (protein stability, mRNA unchanged, ferroptosis rescue, in vivo model), mechanistic rescue by p53 knockdown; single rigorous study","pmids":["36354374"],"is_preprint":false},{"year":2022,"finding":"MEX3A promotes ovarian cancer progression by regulating alternative splicing of TIMELESS mRNA: MEX3A knockdown causes retention of intron 23 of TIMELESS mRNA and decreases TIMELESS mRNA through stimulation of nonsense-mediated RNA decay (NMD).","method":"RNA-seq alternative splicing analysis, MEX3A knockdown with TIMELESS mRNA splicing readout, NMD pathway analysis, TIMELESS overexpression rescue","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNA-seq splicing analysis and NMD mechanism in single lab; rescue experiment confirms pathway placement","pmids":["35715407"],"is_preprint":false},{"year":2022,"finding":"MEX3A interacts with DVL3 (a positive Wnt/β-catenin pathway regulator) via co-immunoprecipitation, stabilizes β-catenin, and upregulates downstream Wnt target genes to promote EMT and endometrial carcinoma progression.","method":"Co-immunoprecipitation (Co-IP), immunofluorescence, GSEA pathway analysis, knockdown/overexpression with β-catenin readout","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single Co-IP combined with functional readouts; single lab but multiple methods","pmids":["36614043"],"is_preprint":false},{"year":2022,"finding":"E2F3 transcription factor induces MEX3A expression, which in turn directly suppresses KLF4 (a pro-differentiation transcription factor) mRNA expression via RNA crosslinking immunoprecipitation (CLIP), thereby activating WNT pathway and maintaining cancer cells in undifferentiated/proliferative state with enhanced radioresistance.","method":"RNA CLIP, luciferase reporter assay, Mex3a KO and intestinal epithelium cKO mouse models, AOM-DSS and Apc-floxed tumor models, organoid cultures, RNA-seq","journal":"Theranostics","confidence":"High","confidence_rationale":"Tier 2 / Strong — CLIP demonstrates direct MEX3A-KLF4 mRNA interaction, validated in multiple in vivo mouse models and organoids, with RNA-seq; multiple orthogonal methods","pmids":["36276637"],"is_preprint":false},{"year":2022,"finding":"Mex3a+ cells in colorectal cancer are chemoresistant persister cells that downregulate the WNT/stem cell gene program after chemotherapy and adopt a YAP+ fetal intestinal progenitor-like state; Mex3a-deficient cells differentiate toward goblet cell-like phenotype and cannot resist chemotherapy.","method":"Lineage-tracing analysis in CRC mouse models, patient-derived organoids with chemotherapy, Mex3a-deficient cell characterization","journal":"Nature cancer","confidence":"High","confidence_rationale":"Tier 2 / Strong — lineage tracing in mouse models combined with patient-derived organoids and genetic Mex3a loss-of-function; independently replicates findings from PMID:28285904","pmids":["35773527"],"is_preprint":false},{"year":2023,"finding":"MEX3A acts as a post-transcriptional regulator in adult murine neural stem cells (NSCs), controlling a quiescence-related RNA signature at critical neurogenic lineage transitions. MEX3A is required for activated NSCs to return to quiescence and for repression of the same stemness program at onset of neuronal differentiation, functioning as a translational remodeller.","method":"In vivo mouse subependymal zone neurogenesis analysis, MEX3A loss-of-function, transcriptomic profiling, stemness-associated transcript analysis","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vivo loss-of-function in adult murine NSCs with transcriptomic readout; single lab","pmids":["36690670"],"is_preprint":false},{"year":2023,"finding":"MEX3A binds IGFBP4 mRNA (via RNA pull-down and RIP assay) and decreases IGFBP4 mRNA levels in breast cancer cells, thereby activating PI3K/AKT and downstream cell cycle/migration pathways.","method":"RNA pull-down assay, RNA immunoprecipitation (RIP), MEX3A knockdown with IGFBP4 mRNA level readout, PI3K/AKT pathway analysis","journal":"Breast cancer research and treatment","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two RNA-binding assays (pull-down + RIP) confirm direct interaction; single lab","pmids":["37433992"],"is_preprint":false},{"year":2023,"finding":"BMAL1 directly activates transcription of Mex3a; MEX3A in turn binds to and stabilizes Lgr5 mRNA to maintain LGR5+ crypt base columnar cell numbers. Bmal1 depletion reduced Mex3a and Lgr5 expression and increased ferroptosis, decreasing LGR5+ CBC numbers.","method":"Chromatin binding/transcription assays for BMAL1-Mex3a, RNA-binding assay for MEX3A-Lgr5 mRNA, Bmal1 depletion with ferroptosis and cell-number readouts","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct transcriptional activation and RNA-binding to Lgr5 mRNA demonstrated; single lab but multiple mechanistic steps validated","pmids":["37845346"],"is_preprint":false},{"year":2023,"finding":"Activated IGF-1R phosphorylates β-arrestin-2 (βarr2) on Tyr64 and Tyr250, inducing conformational changes that open the middle loop (Leu130-Cys141) of βarr2 to interact with the RING domain of MEX3A, thereby triggering MEX3A-mediated ubiquitination and degradation of RIG-I, suppressing IFN-I antiviral immunity in the tumor microenvironment.","method":"Structural modeling, mutant analysis (βarr2Y64A, βarr2Y250A), truncated-βarr2 and peptide competition assays, RIG-I degradation assay, Co-IP/complex formation assays","journal":"Acta pharmaceutica Sinica. B","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple mutant validations and peptide competition confirm mechanism; single lab but detailed mechanistic dissection","pmids":["37521868"],"is_preprint":false},{"year":2021,"finding":"MEX3A knockdown in clear cell renal cell carcinoma induces G1/S cell cycle arrest. Systematic eCLIP-seq and RIP-seq identified CDKN2B mRNA as a direct MEX3A target: MEX3A binds CDKN2B 3'UTR and promotes its mRNA degradation, leading to decreased CDKN2B and uncontrolled cell cycle progression. MEX3A transcription is activated by ETS1.","method":"Enhanced cross-linking immunoprecipitation sequencing (eCLIP-seq), RNA-immunoprecipitation sequencing (RIP-seq), G1/S arrest assay, CDKN2B rescue experiments, ETS1 transcriptional activation assay","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 1 / Moderate — eCLIP-seq + RIP-seq identify direct RNA target; mRNA degradation assay + rescue experiment confirm mechanism; multiple orthogonal methods in single study","pmids":["34976441"],"is_preprint":false},{"year":2024,"finding":"MEX3A undergoes intrinsically disordered region (IDR)-dependent liquid-liquid phase separation (LLPS) in the cytoplasm. In complex with circMPP6 (which acts as a scaffold), MEX3A interacts with processing body (PB) proteins to modulate PB dynamics and promote UPF-mediated degradation of PDE5A mRNA, inhibiting autophagy and promoting CRC progression.","method":"LLPS assay (IDR-dependent), RNA-protein interaction assays (circMPP6-MEX3A), Co-IP with PB proteins, PDE5A mRNA decay assay, autophagy readouts","journal":"Signal transduction and targeted therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — LLPS assay, circRNA-protein interaction, and PB assembly demonstrated; single lab with multiple methods","pmids":["38565536"],"is_preprint":false},{"year":2022,"finding":"SMYD2 epigenetically activates MEX3A expression by promoting H3K36me2 modification on the MEX3A promoter (validated by ChIP-qPCR); MEX3A in turn suppresses CDX2 expression to promote colorectal cancer cell growth.","method":"Chromatin immunoprecipitation (ChIP)-qPCR, MEX3A overexpression/knockdown with CDX2 readout, rescue experiments","journal":"Clinical and experimental pharmacology & physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-qPCR directly demonstrates H3K36me2 at MEX3A promoter; downstream CDX2 suppression confirmed by rescue; single lab","pmids":["35637161"],"is_preprint":false},{"year":2023,"finding":"MEX3A interacts with CREB1 protein (co-immunoprecipitation implied by 'directly targeting CREB1') in thyroid cancer cells; the MEX3A-CREB1 interaction contributes to tumor-promoting effects, as CREB1 silencing alleviates MEX3A-mediated malignant phenotypes.","method":"MEX3A depletion with CREB1 interaction assay, CREB1 silencing rescue experiment","journal":"Cell biology international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — interaction method not explicitly described as Co-IP in abstract; single lab, single cancer type","pmids":["37529875"],"is_preprint":false},{"year":2025,"finding":"Mex3a post-transcriptionally silences olfactory receptor (OR) protein expression during the polygenic stage of OR transcription in developing olfactory sensory neurons (OSNs), decoupling OR transcription from OR protein-induced ER stress. Conditional Mex3a deletion causes premature ER stress during polygenic OR transcription, biases OR choice toward first-transcribed OR alleles, and perturbs OR-regulated axon targeting, disrupting the glomerular map in the olfactory bulb.","method":"Conditional Mex3a deletion in OSNs, ER stress measurement, OR choice analysis, axon targeting/glomerular map analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with multiple functional readouts (ER stress, OR choice, axon guidance, glomerular mapping); mechanistic pathway established through genetic epistasis","pmids":["40668674"],"is_preprint":false},{"year":2026,"finding":"MEX3A directly interacts with PPARG transcripts (identified by HyperTRIBE) and represses PPARγ pathway signaling in intestinal/colorectal cancer cells. Mex3a heterozygous knockout in Apc+/fl and Apc+/fl;Kras+/G12D mouse models reduces tumor burden; MEX3A-depleted patient-derived CRC tumoroids show increased PPARγ, reduced LGR5, and increased sensitivity to FOLFOX chemotherapy.","method":"HyperTRIBE (RNA target identification), Mex3a heterozygous KO in CRC mouse models, CRISPR/Cas9 MEX3A KO in patient-derived tumoroids, PPARγ pathway and chemotherapy sensitivity assays","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"High","confidence_rationale":"Tier 2 / Strong — HyperTRIBE directly identifies PPARG transcript binding, validated in multiple in vivo mouse models and patient-derived tumoroids; replicates PMID:32052574 findings with additional mechanistic depth","pmids":["41881339"],"is_preprint":false},{"year":2025,"finding":"MEX3A depletion in ovarian clear cell carcinoma (OCCC) cells causes chronic mitochondrial fragmentation, decreased mitochondrial membrane potential, increased superoxide, decreased NAD+/NADH ratio, inhibition of OXPHOS, and decreased ATP levels. In mitophagy-stressor-rich environments (e.g., liver), MEX3A-depleted OCCC cells fail to recover from mitophagy, greatly reducing liver metastasis. This mitochondrial fitness control by MEX3A is independent of p53.","method":"MEX3A knockdown with mitochondrial morphology imaging, mitochondrial membrane potential assay, superoxide measurement, NAD+/NADH ratio, OXPHOS/ATP assays, mitophagy stress survival assay, in vivo liver metastasis model","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal mitochondrial assays in single lab; preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.11.05.686880"],"is_preprint":true},{"year":2026,"finding":"MEX3A promotes seRNA m6A methylation in breast cancer by interacting with RBM15B (demonstrated by co-immunoprecipitation), forming a MEX3A/RBM15B/IGF2BP3 complex that maintains KMT2C mRNA expression and stability; IGF2BP3 reads seRNA m6A, and KMT2C promotes H3K4me1 formation to drive super-enhancer activity.","method":"Co-immunoprecipitation (MEX3A-RBM15B), methylated RNA immunoprecipitation (MeRIP) assay, FISH for co-localization, functional proliferation/metastasis assays, in vivo xenograft","journal":"Translational oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and MeRIP assays demonstrate direct interaction and m6A modification; single lab with multiple methods","pmids":["41161249"],"is_preprint":false},{"year":2026,"finding":"Loss of Mex3a in immature olfactory sensory neurons leads to defects in cilia structure, cell surface protein expression, and planar cell polarity in mature OSNs. Proteomics reveal Mex3a-dependent decrease in proteins related to vesicle transport, lipid metabolism, and ribosome biogenesis. Mex3a may confer K27 ubiquitin linkage on substrates including Serbp1 and Rps7. Mex3a levels regulate recruitment of translation factors Serbp1 and p-eEF2 to ribosomes.","method":"Mex3a loss-of-function in OSNs, proteomics, ubiquitin linkage assay (K27), ribosome recruitment assay for Serbp1 and p-eEF2","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics and ubiquitin linkage assays provide mechanistic detail; preprint not yet peer-reviewed","pmids":["41726993"],"is_preprint":true},{"year":2022,"finding":"Grass carp Mex3A (ortholog) interacts physically with RIG-I in the endoplasmic reticulum; RING domain deletion mutant retains RIG-I binding but fails to degrade it, establishing that Mex3A acts as a RING-type E3 ubiquitin ligase to ubiquitinate and degrade RIG-I and inhibit IRF3-mediated antiviral innate immune response.","method":"Co-localization analysis, Co-IP, RING domain truncation/deletion mutant analysis, ubiquitination assay, IRF3 phosphorylation assay","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutant analysis dissects binding from degradation; ortholog study (grass carp) with direct mechanistic validation consistent with mammalian MEX3A findings","pmids":["35865536"],"is_preprint":false}],"current_model":"MEX3A is a dual-function RNA-binding protein (via two KH domains) and E3 ubiquitin ligase (via its C-terminal RING domain) that post-transcriptionally regulates mRNA stability/translation by binding 3'UTRs (targets include CDX2, LAMA2, MSH2, CDKN2B, IGFBP4, KLF4, Lgr5, PPARG transcripts) and mediates proteasomal degradation of specific proteins (RIG-I, p53) through RING-dependent ubiquitination; in intestinal and cancer stem cell contexts it maintains Lgr5+ stem cell identity partly by repressing PPARγ signaling and sustaining Wnt pathway activity, while in glioblastoma and other cancers it promotes chemoresistance by degrading RIG-I and MSH2 (via CCR4-NOT-mediated mRNA deadenylation), and in olfactory neurons it decouples olfactory receptor transcription from ER stress to ensure correct OR choice and axon targeting."},"narrative":{"mechanistic_narrative":"MEX3A is a dual-function post-transcriptional regulator that combines sequence-specific RNA binding through tandem KH domains with E3 ubiquitin ligase activity from a C-terminal RING domain, acting at the intersection of stem-cell maintenance, mRNA fate control, and tumor progression [PMID:23408853, PMID:36354374]. As an RNA-binding protein it recognizes defined 3'UTR elements in target transcripts and destabilizes or represses them: it binds the CDX2 3'UTR to block intestinal differentiation [PMID:23408853], binds an MRE in MSH2 mRNA to recruit the CCR4-NOT deadenylase complex and degrade it, lowering mismatch-repair activity and conferring temozolomide resistance in glioblastoma [PMID:36112059], and degrades CDKN2B [PMID:34976441], KLF4 [PMID:36276637], LAMA2 [PMID:32792503], and IGFBP4 [PMID:37433992] transcripts to drive cell-cycle progression, Wnt activation, and PI3K/AKT signaling across diverse cancers. Conversely, it stabilizes Lgr5 mRNA and binds PPARG transcripts to repress PPARγ signaling, thereby sustaining the Lgr5+ intestinal/colorectal stem-cell program, Wnt activity, and chemoresistance [PMID:37845346, PMID:41881339]. Through its RING domain, MEX3A ubiquitinates and triggers proteasomal degradation of substrate proteins including RIG-I—suppressing type-I interferon antiviral immunity—and p53, the latter blocking ferroptosis to enhance tumorigenesis [PMID:32019099, PMID:36354374, PMID:37521868]. In vivo, Mex3a marks slowly cycling reserve Lgr5+ intestinal stem cells and chemoresistant persister cells that adopt a fetal progenitor-like state, and Mex3a loss reduces tumor burden and restores chemosensitivity [PMID:28285904, PMID:35773527, PMID:41881339]. Beyond cancer it functions as a translational remodeller controlling neural-stem-cell quiescence transitions [PMID:36690670] and decouples olfactory receptor transcription from ER stress to ensure correct receptor choice and axon targeting [PMID:40668674]. MEX3A also undergoes IDR-dependent liquid-liquid phase separation to modulate processing-body dynamics and mRNA decay [PMID:38565536].","teleology":[{"year":2013,"claim":"Established MEX3A as a sequence-specific 3'UTR-binding repressor by showing it binds the CDX2 transcript to block intestinal differentiation and promote a stem-cell marker program.","evidence":"RNA-binding to CDX2 3'UTR with overexpression/knockdown in cells and murine intestine","pmids":["23408853"],"confidence":"High","gaps":["Did not define the RING domain's catalytic role","Mechanism of repression (decay vs. translation) not resolved"]},{"year":2017,"claim":"Defined the physiological cell population: Mex3a marks a slowly cycling reserve subset of Lgr5+ intestinal stem cells spared by chemotherapy and capable of regenerating epithelium.","evidence":"Lineage tracing, single-cell transcriptomics, and in vivo injury models in mouse intestine","pmids":["28285904"],"confidence":"High","gaps":["Molecular targets sustaining the reserve state not identified here","Did not address cancer relevance directly"]},{"year":2020,"claim":"Demonstrated MEX3A's RING-dependent E3 ligase function and broadened RNA-target repertoire, linking it to immune evasion and metastatic signaling.","evidence":"Co-IP/ubiquitylation assays for RIG-I in glioblastoma; RIP and mRNA-stability assays for LAMA2 in lung adenocarcinoma; Mex3a KO mouse with PPARγ manipulation in intestine","pmids":["32019099","32792503","32052574"],"confidence":"High","gaps":["Direct ubiquitin-chain linkage on RIG-I not characterized","Whether RNA-binding and ligase activities are coupled unclear"]},{"year":2021,"claim":"Systematic transcriptome-wide target mapping identified direct mRNA targets and placed MEX3A under specific transcriptional control.","evidence":"eCLIP-seq + RIP-seq identifying CDKN2B in ccRCC with ETS1 activation; Co-IP of RAP1GAP and miR-6887-3p regulation in CRC","pmids":["34976441","33638620"],"confidence":"High","gaps":["RAP1GAP interaction is a single Co-IP without reciprocal validation","Functional hierarchy among many targets unresolved"]},{"year":2022,"claim":"Resolved a deadenylation mechanism and expanded protein-substrate degradation, unifying RNA decay and ubiquitin functions across multiple cancers.","evidence":"MRE identification + CCR4-NOT recruitment for MSH2 (glioblastoma); p53 protein-stability/ferroptosis assays (ovarian); CLIP for KLF4 with in vivo mouse models; Co-IP of DVL3; TIMELESS splicing/NMD analysis; SMYD2 ChIP-qPCR upstream regulation","pmids":["36112059","36354374","36276637","36614043","35715407","35773527","35637161"],"confidence":"High","gaps":["Whether p53 degradation is direct RING-dependent ubiquitination not fully dissected","Splicing/NMD role mechanistically distinct from decay and unintegrated"]},{"year":2023,"claim":"Extended MEX3A to translational remodeling in neural stem cells and integrated it into a circadian-Wnt-stemness circuit, plus defined the IGF-1R/β-arrestin-2 input that activates RIG-I degradation.","evidence":"In vivo NSC loss-of-function with transcriptomics; BMAL1-driven transcription and Lgr5 mRNA stabilization; IGFBP4 RNA pull-down/RIP; structural/mutant dissection of β-arrestin-2–RING interaction","pmids":["36690670","37845346","37433992","37521868","37529875"],"confidence":"Medium","gaps":["NSC target transcripts only profiled at signature level","CREB1 interaction (#20) low-confidence, method not explicitly Co-IP"]},{"year":2024,"claim":"Revealed a biophysical mode of action: MEX3A phase-separates and acts within processing bodies to direct mRNA decay.","evidence":"IDR-dependent LLPS assay, circMPP6 scaffold interaction, PB-protein Co-IP, and PDE5A decay/autophagy readouts in CRC","pmids":["38565536"],"confidence":"Medium","gaps":["Generality of LLPS to other targets untested","circRNA scaffold requirement not validated outside CRC"]},{"year":2025,"claim":"Defined a developmental neuronal role decoupling olfactory receptor transcription from ER stress to ensure correct receptor choice and axon targeting.","evidence":"Conditional Mex3a deletion in olfactory sensory neurons with ER-stress, OR-choice, and glomerular-mapping readouts","pmids":["40668674"],"confidence":"High","gaps":["Direct OR mRNA targets not enumerated","Link between OR silencing and ER-stress timing mechanistic detail incomplete"]},{"year":2026,"claim":"Confirmed PPARG transcripts as direct targets controlling the intestinal/CRC stem program and defined MEX3A in an m6A super-enhancer complex.","evidence":"HyperTRIBE target identification, heterozygous Mex3a KO CRC mouse models, and patient-derived tumoroids; Co-IP/MeRIP of MEX3A/RBM15B/IGF2BP3 on KMT2C in breast cancer","pmids":["41881339","41161249"],"confidence":"High","gaps":["m6A-writer complex mechanism in single lab without reciprocal genetics","How PPARG repression integrates with Wnt and Lgr5 stabilization not fully mapped"]},{"year":null,"claim":"How MEX3A coordinates its RNA-binding, RING ligase, and phase-separation activities into a unified regulatory logic, and what determines target selection across stem-cell, neuronal, and tumor contexts, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model coupling KH and RING activities","Mitochondrial fitness role only in preprint (#23)","K27 ubiquitin linkage on Serbp1/Rps7 only in preprint (#25)"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,2,7,11,14,15,17,22]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[3,8,16,26]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3,8,16,26]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[7,18]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[6,13,25]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[18]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[26]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[7,9,18]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,8,16]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,15,22]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[17]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,16,26]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[13,21]}],"complexes":["CCR4-NOT","processing body","MEX3A/RBM15B/IGF2BP3 m6A complex"],"partners":["RIG-I","EIF4G","RAP1GAP","DVL3","CREB1","RBM15B","CIRCMPP6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"A1L020","full_name":"RNA-binding protein MEX3A","aliases":["RING finger and KH domain-containing protein 4"],"length_aa":520,"mass_kda":54.2,"function":"RNA binding protein, may be involved in post-transcriptional regulatory mechanisms","subcellular_location":"Cytoplasm; Nucleus; Cytoplasm, P-body","url":"https://www.uniprot.org/uniprotkb/A1L020/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MEX3A","classification":"Not Classified","n_dependent_lines":220,"n_total_lines":1208,"dependency_fraction":0.18211920529801323},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MEX3A","total_profiled":1310},"omim":[{"mim_id":"611008","title":"MEX3 RNA-BINDING FAMILY MEMBER B; MEX3B","url":"https://www.omim.org/entry/611008"},{"mim_id":"611007","title":"MEX3 RNA-BINDING FAMILY MEMBER A; MEX3A","url":"https://www.omim.org/entry/611007"},{"mim_id":"611005","title":"MEX3 RNA-BINDING FAMILY MEMBER C; MEX3C","url":"https://www.omim.org/entry/611005"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in 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specific determinant in the CDX2 mRNA 3'UTR and represses CDX2 expression post-transcriptionally, thereby impairing intestinal differentiation, cellular polarization, and promoting expression of intestinal stem cell markers (LGR5, BMI1, MSI1).\",\n      \"method\": \"Cell-based assays (RNA-binding to CDX2 mRNA 3'UTR), expression studies in murine intestine, overexpression/knockdown experiments\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct RNA-binding to 3'UTR demonstrated, functional consequences validated in multiple cellular models and in vivo mouse intestine, multiple orthogonal methods in single study\",\n      \"pmids\": [\"23408853\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mex3a expression marks a slowly cycling, reserve-like subpopulation of Lgr5+ intestinal stem cells (ISCs) that is spared by chemotherapy and radiation (which preferentially target rapidly dividing Lgr5+ cells) and helps regenerate the intestinal epithelium after toxic insults.\",\n      \"method\": \"Lineage tracing, single-cell transcriptome profiling, in vivo chemotherapy/radiation challenge models\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — lineage tracing combined with single-cell transcriptomics and in vivo injury models; replicated in subsequent independent studies\",\n      \"pmids\": [\"28285904\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MEX3A binds LAMA2 mRNA via RNA immunoprecipitation and promotes its instability/degradation in lung adenocarcinoma cells, thereby downregulating LAMA2 and activating PI3K/AKT signaling to promote metastasis.\",\n      \"method\": \"RNA immunoprecipitation (RIP), mRNA stability assay, knockdown/rescue experiments, transcriptome sequencing\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP assay and mRNA stability assay in single lab, functional rescue experiments performed\",\n      \"pmids\": [\"32792503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MEX3A acts as an E3 ubiquitin ligase that binds RIG-I protein and induces its ubiquitylation and proteasome-dependent degradation in glioblastoma cells, suppressing RIG-I tumor suppressor function.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitylation assay, proteasome inhibition, MEX3A knockdown with RIG-I protein level readout\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitylation assay in single lab; RING domain E3 ligase function inferred from domain architecture but ubiquitylation assay is direct\",\n      \"pmids\": [\"32019099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Knockout of Mex3a in mice disrupts Lgr5+ ISC pool maintenance during postnatal intestinal development and impairs organoid maturation ex vivo. Mechanistically, Mex3a deletion induces PPARγ pathway activation with concomitant decrease in Wnt signalling and loss of Lgr5+ stem cell signature; high PPARγ signalling impairs Lgr5+ ISC function.\",\n      \"method\": \"Mex3a knockout mouse model, transcriptomic profiling of intestinal crypts, organoid assays, PPARγ pathway manipulation\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse model with transcriptomics, organoid phenotyping, and pharmacological PPARγ manipulation; multiple orthogonal methods\",\n      \"pmids\": [\"32052574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MEX3A interacts with RAP1GAP protein (demonstrated by Co-IP) and regulates the RAP1GAP/MEK/ERK/HIF-1α pathway to promote colorectal cancer cell proliferation and metastasis; hsa-miR-6887-3p binds the 3'UTR of MEX3A mRNA to suppress its expression.\",\n      \"method\": \"Co-immunoprecipitation (Co-IP), transcriptome analysis, dual-luciferase reporter assay, MEK/ERK inhibitor rescue experiments\",\n      \"journal\": \"Cancer communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrates RAP1GAP interaction; pathway validated with specific inhibitor (U0126); single lab\",\n      \"pmids\": [\"33638620\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The human RNA chaperone MEX3A (hMex3A) binds the Andes orthohantavirus Small mRNA 3'UTR (identified by RNA affinity chromatography/mass spectrometry) and enhances SmRNA translation in a 3'UTR-dependent manner; hMex3A interacts with eIF4G independently of viral infection, suggesting a 5'-3' end interaction mechanism.\",\n      \"method\": \"RNA affinity chromatography followed by mass spectrometry, in vitro translation assay, co-immunoprecipitation (hMex3A-eIF4G interaction)\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro translation assay with 3'UTR-deletion controls, MS-based binding identification, and Co-IP; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"34547046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MEX3A binds to the MEX3 recognition element (MRE) in MSH2 mRNA 3'UTR and recruits CCR4-NOT complexes to induce MSH2 mRNA deadenylation and degradation, thereby reducing DNA mismatch repair activity and conferring temozolomide resistance in glioblastoma.\",\n      \"method\": \"RNA-binding assay (MRE identification), CCR4-NOT complex association assay, mRNA stability/deadenylation assay, MEX3A overexpression/depletion with MMR activity and chemosensitivity readouts\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — identified specific binding element in MSH2 mRNA, demonstrated CCR4-NOT recruitment, measured mRNA deadenylation, and functional DNA MMR assay; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"36112059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MEX3A overexpression in ovarian cancer cells promotes p53 protein degradation without altering p53 mRNA levels; MEX3A-mediated p53 degradation is critical for suppressing ferroptosis and enhancing tumorigenesis. MEX3A contains a RING finger domain (E3 ubiquitin ligase) and an RNA-binding domain.\",\n      \"method\": \"MEX3A depletion/overexpression with p53 protein stability assay, p53 mRNA level measurement (unchanged), ferroptosis assays, orthotopic xenograft models, p53 knockdown rescue experiments\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal assays (protein stability, mRNA unchanged, ferroptosis rescue, in vivo model), mechanistic rescue by p53 knockdown; single rigorous study\",\n      \"pmids\": [\"36354374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MEX3A promotes ovarian cancer progression by regulating alternative splicing of TIMELESS mRNA: MEX3A knockdown causes retention of intron 23 of TIMELESS mRNA and decreases TIMELESS mRNA through stimulation of nonsense-mediated RNA decay (NMD).\",\n      \"method\": \"RNA-seq alternative splicing analysis, MEX3A knockdown with TIMELESS mRNA splicing readout, NMD pathway analysis, TIMELESS overexpression rescue\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNA-seq splicing analysis and NMD mechanism in single lab; rescue experiment confirms pathway placement\",\n      \"pmids\": [\"35715407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MEX3A interacts with DVL3 (a positive Wnt/β-catenin pathway regulator) via co-immunoprecipitation, stabilizes β-catenin, and upregulates downstream Wnt target genes to promote EMT and endometrial carcinoma progression.\",\n      \"method\": \"Co-immunoprecipitation (Co-IP), immunofluorescence, GSEA pathway analysis, knockdown/overexpression with β-catenin readout\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single Co-IP combined with functional readouts; single lab but multiple methods\",\n      \"pmids\": [\"36614043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"E2F3 transcription factor induces MEX3A expression, which in turn directly suppresses KLF4 (a pro-differentiation transcription factor) mRNA expression via RNA crosslinking immunoprecipitation (CLIP), thereby activating WNT pathway and maintaining cancer cells in undifferentiated/proliferative state with enhanced radioresistance.\",\n      \"method\": \"RNA CLIP, luciferase reporter assay, Mex3a KO and intestinal epithelium cKO mouse models, AOM-DSS and Apc-floxed tumor models, organoid cultures, RNA-seq\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CLIP demonstrates direct MEX3A-KLF4 mRNA interaction, validated in multiple in vivo mouse models and organoids, with RNA-seq; multiple orthogonal methods\",\n      \"pmids\": [\"36276637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Mex3a+ cells in colorectal cancer are chemoresistant persister cells that downregulate the WNT/stem cell gene program after chemotherapy and adopt a YAP+ fetal intestinal progenitor-like state; Mex3a-deficient cells differentiate toward goblet cell-like phenotype and cannot resist chemotherapy.\",\n      \"method\": \"Lineage-tracing analysis in CRC mouse models, patient-derived organoids with chemotherapy, Mex3a-deficient cell characterization\",\n      \"journal\": \"Nature cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — lineage tracing in mouse models combined with patient-derived organoids and genetic Mex3a loss-of-function; independently replicates findings from PMID:28285904\",\n      \"pmids\": [\"35773527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEX3A acts as a post-transcriptional regulator in adult murine neural stem cells (NSCs), controlling a quiescence-related RNA signature at critical neurogenic lineage transitions. MEX3A is required for activated NSCs to return to quiescence and for repression of the same stemness program at onset of neuronal differentiation, functioning as a translational remodeller.\",\n      \"method\": \"In vivo mouse subependymal zone neurogenesis analysis, MEX3A loss-of-function, transcriptomic profiling, stemness-associated transcript analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vivo loss-of-function in adult murine NSCs with transcriptomic readout; single lab\",\n      \"pmids\": [\"36690670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEX3A binds IGFBP4 mRNA (via RNA pull-down and RIP assay) and decreases IGFBP4 mRNA levels in breast cancer cells, thereby activating PI3K/AKT and downstream cell cycle/migration pathways.\",\n      \"method\": \"RNA pull-down assay, RNA immunoprecipitation (RIP), MEX3A knockdown with IGFBP4 mRNA level readout, PI3K/AKT pathway analysis\",\n      \"journal\": \"Breast cancer research and treatment\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two RNA-binding assays (pull-down + RIP) confirm direct interaction; single lab\",\n      \"pmids\": [\"37433992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BMAL1 directly activates transcription of Mex3a; MEX3A in turn binds to and stabilizes Lgr5 mRNA to maintain LGR5+ crypt base columnar cell numbers. Bmal1 depletion reduced Mex3a and Lgr5 expression and increased ferroptosis, decreasing LGR5+ CBC numbers.\",\n      \"method\": \"Chromatin binding/transcription assays for BMAL1-Mex3a, RNA-binding assay for MEX3A-Lgr5 mRNA, Bmal1 depletion with ferroptosis and cell-number readouts\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct transcriptional activation and RNA-binding to Lgr5 mRNA demonstrated; single lab but multiple mechanistic steps validated\",\n      \"pmids\": [\"37845346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Activated IGF-1R phosphorylates β-arrestin-2 (βarr2) on Tyr64 and Tyr250, inducing conformational changes that open the middle loop (Leu130-Cys141) of βarr2 to interact with the RING domain of MEX3A, thereby triggering MEX3A-mediated ubiquitination and degradation of RIG-I, suppressing IFN-I antiviral immunity in the tumor microenvironment.\",\n      \"method\": \"Structural modeling, mutant analysis (βarr2Y64A, βarr2Y250A), truncated-βarr2 and peptide competition assays, RIG-I degradation assay, Co-IP/complex formation assays\",\n      \"journal\": \"Acta pharmaceutica Sinica. B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mutant validations and peptide competition confirm mechanism; single lab but detailed mechanistic dissection\",\n      \"pmids\": [\"37521868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MEX3A knockdown in clear cell renal cell carcinoma induces G1/S cell cycle arrest. Systematic eCLIP-seq and RIP-seq identified CDKN2B mRNA as a direct MEX3A target: MEX3A binds CDKN2B 3'UTR and promotes its mRNA degradation, leading to decreased CDKN2B and uncontrolled cell cycle progression. MEX3A transcription is activated by ETS1.\",\n      \"method\": \"Enhanced cross-linking immunoprecipitation sequencing (eCLIP-seq), RNA-immunoprecipitation sequencing (RIP-seq), G1/S arrest assay, CDKN2B rescue experiments, ETS1 transcriptional activation assay\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — eCLIP-seq + RIP-seq identify direct RNA target; mRNA degradation assay + rescue experiment confirm mechanism; multiple orthogonal methods in single study\",\n      \"pmids\": [\"34976441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MEX3A undergoes intrinsically disordered region (IDR)-dependent liquid-liquid phase separation (LLPS) in the cytoplasm. In complex with circMPP6 (which acts as a scaffold), MEX3A interacts with processing body (PB) proteins to modulate PB dynamics and promote UPF-mediated degradation of PDE5A mRNA, inhibiting autophagy and promoting CRC progression.\",\n      \"method\": \"LLPS assay (IDR-dependent), RNA-protein interaction assays (circMPP6-MEX3A), Co-IP with PB proteins, PDE5A mRNA decay assay, autophagy readouts\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — LLPS assay, circRNA-protein interaction, and PB assembly demonstrated; single lab with multiple methods\",\n      \"pmids\": [\"38565536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SMYD2 epigenetically activates MEX3A expression by promoting H3K36me2 modification on the MEX3A promoter (validated by ChIP-qPCR); MEX3A in turn suppresses CDX2 expression to promote colorectal cancer cell growth.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP)-qPCR, MEX3A overexpression/knockdown with CDX2 readout, rescue experiments\",\n      \"journal\": \"Clinical and experimental pharmacology & physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-qPCR directly demonstrates H3K36me2 at MEX3A promoter; downstream CDX2 suppression confirmed by rescue; single lab\",\n      \"pmids\": [\"35637161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEX3A interacts with CREB1 protein (co-immunoprecipitation implied by 'directly targeting CREB1') in thyroid cancer cells; the MEX3A-CREB1 interaction contributes to tumor-promoting effects, as CREB1 silencing alleviates MEX3A-mediated malignant phenotypes.\",\n      \"method\": \"MEX3A depletion with CREB1 interaction assay, CREB1 silencing rescue experiment\",\n      \"journal\": \"Cell biology international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — interaction method not explicitly described as Co-IP in abstract; single lab, single cancer type\",\n      \"pmids\": [\"37529875\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mex3a post-transcriptionally silences olfactory receptor (OR) protein expression during the polygenic stage of OR transcription in developing olfactory sensory neurons (OSNs), decoupling OR transcription from OR protein-induced ER stress. Conditional Mex3a deletion causes premature ER stress during polygenic OR transcription, biases OR choice toward first-transcribed OR alleles, and perturbs OR-regulated axon targeting, disrupting the glomerular map in the olfactory bulb.\",\n      \"method\": \"Conditional Mex3a deletion in OSNs, ER stress measurement, OR choice analysis, axon targeting/glomerular map analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with multiple functional readouts (ER stress, OR choice, axon guidance, glomerular mapping); mechanistic pathway established through genetic epistasis\",\n      \"pmids\": [\"40668674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"MEX3A directly interacts with PPARG transcripts (identified by HyperTRIBE) and represses PPARγ pathway signaling in intestinal/colorectal cancer cells. Mex3a heterozygous knockout in Apc+/fl and Apc+/fl;Kras+/G12D mouse models reduces tumor burden; MEX3A-depleted patient-derived CRC tumoroids show increased PPARγ, reduced LGR5, and increased sensitivity to FOLFOX chemotherapy.\",\n      \"method\": \"HyperTRIBE (RNA target identification), Mex3a heterozygous KO in CRC mouse models, CRISPR/Cas9 MEX3A KO in patient-derived tumoroids, PPARγ pathway and chemotherapy sensitivity assays\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — HyperTRIBE directly identifies PPARG transcript binding, validated in multiple in vivo mouse models and patient-derived tumoroids; replicates PMID:32052574 findings with additional mechanistic depth\",\n      \"pmids\": [\"41881339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MEX3A depletion in ovarian clear cell carcinoma (OCCC) cells causes chronic mitochondrial fragmentation, decreased mitochondrial membrane potential, increased superoxide, decreased NAD+/NADH ratio, inhibition of OXPHOS, and decreased ATP levels. In mitophagy-stressor-rich environments (e.g., liver), MEX3A-depleted OCCC cells fail to recover from mitophagy, greatly reducing liver metastasis. This mitochondrial fitness control by MEX3A is independent of p53.\",\n      \"method\": \"MEX3A knockdown with mitochondrial morphology imaging, mitochondrial membrane potential assay, superoxide measurement, NAD+/NADH ratio, OXPHOS/ATP assays, mitophagy stress survival assay, in vivo liver metastasis model\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal mitochondrial assays in single lab; preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.11.05.686880\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"MEX3A promotes seRNA m6A methylation in breast cancer by interacting with RBM15B (demonstrated by co-immunoprecipitation), forming a MEX3A/RBM15B/IGF2BP3 complex that maintains KMT2C mRNA expression and stability; IGF2BP3 reads seRNA m6A, and KMT2C promotes H3K4me1 formation to drive super-enhancer activity.\",\n      \"method\": \"Co-immunoprecipitation (MEX3A-RBM15B), methylated RNA immunoprecipitation (MeRIP) assay, FISH for co-localization, functional proliferation/metastasis assays, in vivo xenograft\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and MeRIP assays demonstrate direct interaction and m6A modification; single lab with multiple methods\",\n      \"pmids\": [\"41161249\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Loss of Mex3a in immature olfactory sensory neurons leads to defects in cilia structure, cell surface protein expression, and planar cell polarity in mature OSNs. Proteomics reveal Mex3a-dependent decrease in proteins related to vesicle transport, lipid metabolism, and ribosome biogenesis. Mex3a may confer K27 ubiquitin linkage on substrates including Serbp1 and Rps7. Mex3a levels regulate recruitment of translation factors Serbp1 and p-eEF2 to ribosomes.\",\n      \"method\": \"Mex3a loss-of-function in OSNs, proteomics, ubiquitin linkage assay (K27), ribosome recruitment assay for Serbp1 and p-eEF2\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics and ubiquitin linkage assays provide mechanistic detail; preprint not yet peer-reviewed\",\n      \"pmids\": [\"41726993\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Grass carp Mex3A (ortholog) interacts physically with RIG-I in the endoplasmic reticulum; RING domain deletion mutant retains RIG-I binding but fails to degrade it, establishing that Mex3A acts as a RING-type E3 ubiquitin ligase to ubiquitinate and degrade RIG-I and inhibit IRF3-mediated antiviral innate immune response.\",\n      \"method\": \"Co-localization analysis, Co-IP, RING domain truncation/deletion mutant analysis, ubiquitination assay, IRF3 phosphorylation assay\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutant analysis dissects binding from degradation; ortholog study (grass carp) with direct mechanistic validation consistent with mammalian MEX3A findings\",\n      \"pmids\": [\"35865536\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MEX3A is a dual-function RNA-binding protein (via two KH domains) and E3 ubiquitin ligase (via its C-terminal RING domain) that post-transcriptionally regulates mRNA stability/translation by binding 3'UTRs (targets include CDX2, LAMA2, MSH2, CDKN2B, IGFBP4, KLF4, Lgr5, PPARG transcripts) and mediates proteasomal degradation of specific proteins (RIG-I, p53) through RING-dependent ubiquitination; in intestinal and cancer stem cell contexts it maintains Lgr5+ stem cell identity partly by repressing PPARγ signaling and sustaining Wnt pathway activity, while in glioblastoma and other cancers it promotes chemoresistance by degrading RIG-I and MSH2 (via CCR4-NOT-mediated mRNA deadenylation), and in olfactory neurons it decouples olfactory receptor transcription from ER stress to ensure correct OR choice and axon targeting.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MEX3A is a dual-function post-transcriptional regulator that combines sequence-specific RNA binding through tandem KH domains with E3 ubiquitin ligase activity from a C-terminal RING domain, acting at the intersection of stem-cell maintenance, mRNA fate control, and tumor progression [#0, #8]. As an RNA-binding protein it recognizes defined 3'UTR elements in target transcripts and destabilizes or represses them: it binds the CDX2 3'UTR to block intestinal differentiation [#0], binds an MRE in MSH2 mRNA to recruit the CCR4-NOT deadenylase complex and degrade it, lowering mismatch-repair activity and conferring temozolomide resistance in glioblastoma [#7], and degrades CDKN2B [#17], KLF4 [#11], LAMA2 [#2], and IGFBP4 [#14] transcripts to drive cell-cycle progression, Wnt activation, and PI3K/AKT signaling across diverse cancers. Conversely, it stabilizes Lgr5 mRNA and binds PPARG transcripts to repress PPARγ signaling, thereby sustaining the Lgr5+ intestinal/colorectal stem-cell program, Wnt activity, and chemoresistance [#15, #22]. Through its RING domain, MEX3A ubiquitinates and triggers proteasomal degradation of substrate proteins including RIG-I—suppressing type-I interferon antiviral immunity—and p53, the latter blocking ferroptosis to enhance tumorigenesis [#3, #8, #16]. In vivo, Mex3a marks slowly cycling reserve Lgr5+ intestinal stem cells and chemoresistant persister cells that adopt a fetal progenitor-like state, and Mex3a loss reduces tumor burden and restores chemosensitivity [#1, #12, #22]. Beyond cancer it functions as a translational remodeller controlling neural-stem-cell quiescence transitions [#13] and decouples olfactory receptor transcription from ER stress to ensure correct receptor choice and axon targeting [#21]. MEX3A also undergoes IDR-dependent liquid-liquid phase separation to modulate processing-body dynamics and mRNA decay [#18].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Established MEX3A as a sequence-specific 3'UTR-binding repressor by showing it binds the CDX2 transcript to block intestinal differentiation and promote a stem-cell marker program.\",\n      \"evidence\": \"RNA-binding to CDX2 3'UTR with overexpression/knockdown in cells and murine intestine\",\n      \"pmids\": [\"23408853\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the RING domain's catalytic role\", \"Mechanism of repression (decay vs. translation) not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the physiological cell population: Mex3a marks a slowly cycling reserve subset of Lgr5+ intestinal stem cells spared by chemotherapy and capable of regenerating epithelium.\",\n      \"evidence\": \"Lineage tracing, single-cell transcriptomics, and in vivo injury models in mouse intestine\",\n      \"pmids\": [\"28285904\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular targets sustaining the reserve state not identified here\", \"Did not address cancer relevance directly\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated MEX3A's RING-dependent E3 ligase function and broadened RNA-target repertoire, linking it to immune evasion and metastatic signaling.\",\n      \"evidence\": \"Co-IP/ubiquitylation assays for RIG-I in glioblastoma; RIP and mRNA-stability assays for LAMA2 in lung adenocarcinoma; Mex3a KO mouse with PPARγ manipulation in intestine\",\n      \"pmids\": [\"32019099\", \"32792503\", \"32052574\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ubiquitin-chain linkage on RIG-I not characterized\", \"Whether RNA-binding and ligase activities are coupled unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Systematic transcriptome-wide target mapping identified direct mRNA targets and placed MEX3A under specific transcriptional control.\",\n      \"evidence\": \"eCLIP-seq + RIP-seq identifying CDKN2B in ccRCC with ETS1 activation; Co-IP of RAP1GAP and miR-6887-3p regulation in CRC\",\n      \"pmids\": [\"34976441\", \"33638620\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RAP1GAP interaction is a single Co-IP without reciprocal validation\", \"Functional hierarchy among many targets unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved a deadenylation mechanism and expanded protein-substrate degradation, unifying RNA decay and ubiquitin functions across multiple cancers.\",\n      \"evidence\": \"MRE identification + CCR4-NOT recruitment for MSH2 (glioblastoma); p53 protein-stability/ferroptosis assays (ovarian); CLIP for KLF4 with in vivo mouse models; Co-IP of DVL3; TIMELESS splicing/NMD analysis; SMYD2 ChIP-qPCR upstream regulation\",\n      \"pmids\": [\"36112059\", \"36354374\", \"36276637\", \"36614043\", \"35715407\", \"35773527\", \"35637161\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether p53 degradation is direct RING-dependent ubiquitination not fully dissected\", \"Splicing/NMD role mechanistically distinct from decay and unintegrated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended MEX3A to translational remodeling in neural stem cells and integrated it into a circadian-Wnt-stemness circuit, plus defined the IGF-1R/β-arrestin-2 input that activates RIG-I degradation.\",\n      \"evidence\": \"In vivo NSC loss-of-function with transcriptomics; BMAL1-driven transcription and Lgr5 mRNA stabilization; IGFBP4 RNA pull-down/RIP; structural/mutant dissection of β-arrestin-2–RING interaction\",\n      \"pmids\": [\"36690670\", \"37845346\", \"37433992\", \"37521868\", \"37529875\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"NSC target transcripts only profiled at signature level\", \"CREB1 interaction (#20) low-confidence, method not explicitly Co-IP\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a biophysical mode of action: MEX3A phase-separates and acts within processing bodies to direct mRNA decay.\",\n      \"evidence\": \"IDR-dependent LLPS assay, circMPP6 scaffold interaction, PB-protein Co-IP, and PDE5A decay/autophagy readouts in CRC\",\n      \"pmids\": [\"38565536\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Generality of LLPS to other targets untested\", \"circRNA scaffold requirement not validated outside CRC\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined a developmental neuronal role decoupling olfactory receptor transcription from ER stress to ensure correct receptor choice and axon targeting.\",\n      \"evidence\": \"Conditional Mex3a deletion in olfactory sensory neurons with ER-stress, OR-choice, and glomerular-mapping readouts\",\n      \"pmids\": [\"40668674\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct OR mRNA targets not enumerated\", \"Link between OR silencing and ER-stress timing mechanistic detail incomplete\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Confirmed PPARG transcripts as direct targets controlling the intestinal/CRC stem program and defined MEX3A in an m6A super-enhancer complex.\",\n      \"evidence\": \"HyperTRIBE target identification, heterozygous Mex3a KO CRC mouse models, and patient-derived tumoroids; Co-IP/MeRIP of MEX3A/RBM15B/IGF2BP3 on KMT2C in breast cancer\",\n      \"pmids\": [\"41881339\", \"41161249\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"m6A-writer complex mechanism in single lab without reciprocal genetics\", \"How PPARG repression integrates with Wnt and Lgr5 stabilization not fully mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MEX3A coordinates its RNA-binding, RING ligase, and phase-separation activities into a unified regulatory logic, and what determines target selection across stem-cell, neuronal, and tumor contexts, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model coupling KH and RING activities\", \"Mitochondrial fitness role only in preprint (#23)\", \"K27 ubiquitin linkage on Serbp1/Rps7 only in preprint (#25)\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 2, 7, 11, 14, 15, 17, 22]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [3, 8, 16, 26]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3, 8, 16, 26]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [7, 18]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [6, 13, 25]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [26]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [7, 9, 18]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 8, 16]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 15, 22]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 16, 26]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [13, 21]}\n    ],\n    \"complexes\": [\"CCR4-NOT\", \"processing body\", \"MEX3A/RBM15B/IGF2BP3 m6A complex\"],\n    \"partners\": [\"RIG-I\", \"eIF4G\", \"RAP1GAP\", \"DVL3\", \"CREB1\", \"RBM15B\", \"circMPP6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}