{"gene":"MSI1","run_date":"2026-06-10T02:59:51","timeline":{"discoveries":[{"year":1989,"finding":"Yeast MSI1 encodes a WD40-repeat protein that negatively regulates the RAS-cAMP signaling pathway; overexpression of MSI1 suppresses heat shock sensitivity and reduces elevated intracellular cAMP levels caused by ira1 or RAS2Val19 mutations, but not bcy1 mutations, placing MSI1 upstream of cAMP but downstream of (or parallel to) BCY1.","method":"Genetic suppression screen (high-copy plasmid suppressors of ira1 heat-shock sensitivity); cAMP measurement; sporulation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with multiple alleles, cAMP measurement, replicated in multiple genetic backgrounds in a foundational study","pmids":["2554329"],"is_preprint":false},{"year":2001,"finding":"CAC3/MSI1 suppression of the RAS/cAMP pathway is independent of chromatin assembly factor I (CAF-I) subunits CAC1 and CAC2. Cac3p/Msi1p localizes to both nucleus and cytoplasm and physically associates with Npr1p (a cytoplasmic kinase). Deletion of NPR1 phenocopies CAC3 overexpression in suppressing RAS/cAMP, and NPR1 overexpression blocks CAC3-mediated suppression, indicating that excess Cac3p suppresses RAS/cAMP by sequestering Npr1p.","method":"Genetic epistasis (double mutants), co-immunoprecipitation/association assay, localization studies, suppression analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genetic and biochemical methods, reciprocal epistasis, subcellular localization linked to function","pmids":["11238915"],"is_preprint":false},{"year":2000,"finding":"MSI1 overexpression suppresses hyperactive RAS phenotypes in multiple genetic backgrounds but does not inhibit cAMP synthesis or total cellular PKA activity. MSI1 requires the PKA regulatory subunit BCY1 to inhibit a mutationally activated PKA catalytic subunit, indicating that MSI1 modulates PKA function in a BCY1-dependent manner. MSI1's RAS-suppressing function is separable from its role in CAF-I chromatin assembly.","method":"Genetic analysis (multiple yeast strains, epistasis), PKA activity assay, cAMP measurement","journal":"Current genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in multiple backgrounds, biochemical PKA/cAMP assays, single lab","pmids":["10975254"],"is_preprint":false},{"year":2007,"finding":"MSI1 (CAC3) genetically interacts with YAK1 (a kinase antagonizing RAS/cAMP). MSI1 suppresses heat-shock sensitivity from yak1 deletion. YAK1 is required for Msi1p association with Cac1p (yeast two-hybrid). Msi1p can activate transcription of a reporter when tethered near a promoter in non-fermentable carbon conditions, and this activity requires YAK1. YAK1 antagonizes nuclear accumulation of Msi1p in non-fermenting cells.","method":"Yeast two-hybrid, genetic suppression, transcriptional reporter assay, localization analysis","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Y2H, reporter, localization), single lab","pmids":["17321547"],"is_preprint":false},{"year":2006,"finding":"Neural ELAV proteins (HuD) bind the AU-rich element (ARE) in the Msi1 mRNA 3'UTR in an ARE-dependent manner, stabilize the Msi1 ARE-containing mRNA in a deadenylation/degradation assay, and increase Musashi-1 protein levels. Activation of neural ELAV proteins by phorbol esters in SH-SY5Y cells increases Musashi-1 protein in the cytoskeleton.","method":"RNA-protein binding assay, mRNA deadenylation/degradation assay, immunofluorescence co-localization, pharmacological activation","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro RNA-binding and functional mRNA stability assay plus cell-based validation, single lab","pmids":["16554442"],"is_preprint":false},{"year":2014,"finding":"MSI1 directly binds the 3'UTR of p21, p27, and p53 mRNAs (verified by RNA-protein binding assays) and suppresses their translation (confirmed by luciferase 3'UTR reporter assays). Overexpression of Msi1 in cervical cancer cells downregulates p21, p27, and p53 protein levels and promotes cell cycle S-phase entry, whereas shRNA knockdown upregulates these proteins and slows S-phase entry.","method":"RNA-protein binding assay, luciferase 3'UTR reporter assay, shRNA knockdown, Western blot, flow cytometry","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct RNA-binding plus luciferase reporter plus protein level changes with gain/loss of function, two orthogonal functional assays","pmids":["25362645"],"is_preprint":false},{"year":2014,"finding":"Msi1 directly suppresses translation of p21cip1 mRNA via its 3'UTR-specific motif, as demonstrated by a chimeric luciferase-p21cip1 3'UTR reporter assay. Knockdown of Msi1 in colon cancer cells increases p21cip1 protein, induces G0/G1 arrest, and suppresses proliferation and tumorsphere formation.","method":"Luciferase chimeric mRNA 3'UTR reporter assay, RNAi knockdown, Western blot, flow cytometry, in vivo xenograft","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter with specific motif plus loss-of-function phenotype, single lab","pmids":["25394506"],"is_preprint":false},{"year":2017,"finding":"Msi1 promotes epithelial-to-mesenchymal transition (EMT) in cervical cancer cells; shRNA silencing of Msi1 reduces EMT marker expression and inhibits Wnt signaling activity, while Msi1 expression positively correlates with EMT markers in clinical tissues.","method":"shRNA knockdown, Western blot, invasion/migration assay, in vivo tumor assay, immunohistochemistry","journal":"Human pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined phenotype and pathway (Wnt/EMT), single lab, no reconstitution","pmids":["28088346"],"is_preprint":false},{"year":2017,"finding":"MSI1 knockdown in osteosarcoma cells causes G0/G1 cell cycle arrest and upregulation of p21 and p27 protein levels. Luciferase assays confirm that MSI1 binds the 3'UTR of both p21 and p27 mRNAs.","method":"shRNA knockdown, luciferase 3'UTR reporter assay, Western blot, flow cytometry, in vivo xenograft","journal":"Oncology letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter plus loss-of-function phenotype, single lab","pmids":["29113163"],"is_preprint":false},{"year":2015,"finding":"Msi1 confers TRAIL resistance in hepatocellular carcinoma cells by activating ERK; forced Msi1 expression increases ERK activation and TRAIL resistance, and siRNA depletion of ERK overcomes Msi1-mediated TRAIL resistance. Differential AKT activation was not responsible.","method":"Stable subline isolation, shRNA/siRNA knockdown, forced expression, TRAIL resistance assays in vitro and in vivo xenograft","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with mechanistic pathway (ERK) validation, single lab","pmids":["25747387"],"is_preprint":false},{"year":2018,"finding":"MSI1 enhances GBM radioresistance by increasing homologous recombination (HR) DNA repair and promoting VCAM1-mediated tumor invasion; MSI1 knockdown causes DNA damage accumulation in irradiated GBM cells and reduces xenograft tumor formation after irradiation.","method":"shRNA knockdown, overexpression, irradiation assays, DNA damage markers (γH2AX), invasion assay, xenograft","journal":"Radiotherapy and oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss of function with DNA repair readout and invasion marker VCAM1, single lab","pmids":["30322656"],"is_preprint":false},{"year":2020,"finding":"The Msi1-mTOR pathway drives keratinocyte-to-Paget-like cell conversion; Msi1 overexpression in epidermal basal cells activates mTOR signaling, and mTOR inhibition with rapamycin rescues the Paget-like phenotype in Msi1-overexpressing transgenic mice.","method":"Transgenic mouse model, single-cell RNA-sequencing, lineage tracing, rapamycin treatment, RNA velocity analysis","journal":"Cell research","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic gain-of-function, pharmacological pathway rescue, multiple orthogonal methods including scRNA-seq and lineage tracing","pmids":["32457396"],"is_preprint":false},{"year":2020,"finding":"MSI1 promotes breast cancer metastasis by directly suppressing TIMP3 mRNA (an endogenous inhibitor of MMP9), leading to increased MMP9 expression and activity, invadopodia formation, and ECM degradation. The MSI1-TIMP3-MMP9 cascade is required for invadopodia-mediated metastasis.","method":"shRNA knockdown, overexpression, RNA-binding assay (direct suppression of Timp3), MMP9 activity assay, invadopodia assay, in vivo lung metastasis model, clinical correlation","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct RNA binding to Timp3 established, mechanistic cascade (MSI1→TIMP3→MMP9) validated by multiple functional assays and in vivo metastasis model","pmids":["34155343"],"is_preprint":false},{"year":2020,"finding":"MSI1 promotes expression of the GBM stem cell marker CD44 by impairing miRNA-dependent degradation of CD44 mRNA via its 3'UTR; this regulation is disrupted by the MSI1 inhibitor luteolin.","method":"Knockdown and overexpression, 3'UTR reporter assay, mRNA turnover assay, luteolin inhibitor treatment, GBM cell and primary tumorsphere models","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — 3'UTR-dependent mRNA stabilization mechanism, pharmacological inhibitor, single lab","pmids":["33291443"],"is_preprint":false},{"year":2020,"finding":"MSI1 directly binds and stabilizes the Fthl17c mRNA; MSI1 ablation in mESCs reduces Fthl17c expression, decreasing intracellular Fe2⁺, impairing TET enzyme activity, and increasing global DNA methylation (5mC). FTHL17C interacts with TET1 in the nucleus. Restoration of Fthl17c rescues TET activity and pluripotency gene expression, defining an MSI1-FTHL17C-Fe2⁺-TET axis linking post-transcriptional iron homeostasis control with epigenetic remodeling.","method":"Genetic ablation (MSI1 knockout), RNA immunoprecipitation, biochemical TET activity assay, DNA methylation (5mC) measurement, co-immunoprecipitation (FTHL17C-TET1), rescue experiments, fluorescence imaging","journal":"Cell regeneration (London, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RIP, TET assay, 5mC, Co-IP, rescue), single lab, preprint-adjacent but published","pmids":["42089935"],"is_preprint":false},{"year":2021,"finding":"MSI1 interacts with AGO2 via its C-terminus; peptides mimicking the C-terminus of MSI1 (Pep#11 and Pep#26) competitively interfere with MSI1-AGO2 binding (confirmed by Biacore binding analyses), reduce GBM tumorigenesis, and improve survival in GBM animal models.","method":"Peptide array, Biacore surface plasmon resonance, recombinant reporter system, in vivo GBM xenograft model","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — SPR binding assay plus in vivo functional validation, single lab","pmids":["35158774"],"is_preprint":false},{"year":2021,"finding":"MSI1 inhibits cervical cancer cell apoptosis by downregulating PTEN, thereby activating AKT signaling, which reduces the proapoptotic protein BAK; rescue of BAK expression in Msi1-expressing cells restores apoptosis.","method":"Overexpression, shRNA knockdown, Western blot, apoptosis assay, rescue experiment (BAK re-expression), in vivo xenograft","journal":"Journal of Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pathway delineated (MSI1→PTEN suppression→AKT→BAK), rescue validates mechanism, single lab","pmids":["33758618"],"is_preprint":false},{"year":2022,"finding":"MSI1 phosphorylation at residues T18, S19, and S34 (identified by mass spectrometry in C. elegans MSI-1) is necessary for MSI-1 function in both short- and long-term aversive olfactory associative memory; CRISPR-based manipulation of these phosphorylation sites abolishes memory-related MSI-1 function. MSI-1 function is controlled by activity rather than expression levels.","method":"Mass spectrometry phosphorylation mapping, CRISPR-based point mutations, behavioral assays (short- and long-term memory)","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass spectrometry-identified PTM sites validated by CRISPR mutagenesis with functional readout, C. elegans ortholog study","pmids":["36223338"],"is_preprint":false},{"year":2020,"finding":"In photoreceptor neurons, both MSI1 and MSI2 are required for inclusion of photoreceptor-specific alternative exons in transcripts critical for outer segment morphogenesis (Cc2d2a, Cep290, Prom1, Ttc8), ciliogenesis, and synaptic transmission. Loss of both Msi1 and Msi2 causes disrupted outer segment morphology, ciliary defects, loss of light response, and photoreceptor degeneration within 6 months.","method":"Conditional double knockout mouse (pan-retinal and rod-specific), electrophysiology (ERG), RNA splicing analysis, immunofluorescence, histology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO mouse with defined molecular splicing phenotype, electrophysiological functional readout, and morphological analysis; multiple orthogonal methods","pmids":["33168629"],"is_preprint":false},{"year":2025,"finding":"A single Musashi allele (from either Msi1 or Msi2) is sufficient to maintain photoreceptor function and high inclusion levels of photoreceptor-specific alternative exons (in Cc2d2a, Cep290, Prom1, Ttc8), demonstrating that the Musashi proteins act in a dose-dependent, partially redundant manner to regulate alternative splicing specifically in photoreceptors.","method":"Combined conditional Msi1/Msi2 knockouts with progressive allele reduction, RT-PCR splicing analysis, electrophysiology","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — allelic series with functional splicing and electrophysiological readout, single lab, preprint","pmids":["bio_10.1101_2025.11.26.690869"],"is_preprint":true},{"year":2024,"finding":"MSI1 directly binds the SARS-CoV-2 3'UTR (confirmed by in vivo RNA immunoprecipitation and biochemical assays), and this binding results in translational repression mediated by inhibition of Poly(A)-binding protein (PABP). MSI1 knockout promotes robust viral replication and increased viral protein expression in intestinal cells, stem cells, and 3D organoids.","method":"Computational prediction, RNA immunoprecipitation (RIP), biochemical binding assay, MSI1 knockout cell lines, 2D and 3D organoid infection assays, viral protein expression quantification","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP plus biochemical assay plus functional KO phenotype, multi-model validation, single lab, preprint","pmids":["bio_10.1101_2024.09.29.615653"],"is_preprint":true},{"year":2013,"finding":"Hedgehog signaling agonist (purmorphamine) enhances mesenchymal stem cell proliferation and suppresses apoptosis through the RNA-binding protein Msi1, which regulates c-Myc oncoprotein expression and p21CIP1 cell cycle regulator, and modulates miRNA-148a and miRNA-148b.","method":"Hedgehog agonist/antagonist treatment, MSI1 knockdown/overexpression, Western blot, proliferation and apoptosis assays","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pathway placement inferred from pharmacological activation and single knockdown experiments, no direct binding assay for downstream targets, single lab","pmids":["23418578"],"is_preprint":false},{"year":2013,"finding":"Hedgehog signaling negatively regulates osteogenic differentiation of mesenchymal stem cells through Msi1, which suppresses Wnt1 expression and the miR-148 family (especially miR-148b).","method":"Hedgehog agonist/antagonist treatment, Msi1 knockdown/overexpression, osteogenic differentiation assays, qRT-PCR","journal":"Bone","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological and knockdown data without direct binding assays, single lab","pmids":["23880227"],"is_preprint":false},{"year":2025,"finding":"MSI1 binds to the ABHD2 promoter region and activates ABHD2 transcription (confirmed by dual-luciferase reporter and ChIP assays), thereby promoting prostate cancer cell proliferation, migration, and glycolysis.","method":"ChIP assay, dual-luciferase reporter assay, siRNA knockdown, EdU proliferation assay, flow cytometry, transwell assay, glycolysis measurement, xenograft","journal":"Biochemical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and luciferase reporter confirm direct MSI1 binding to ABHD2 promoter, loss-of-function phenotype confirmed in vitro and in vivo, single lab","pmids":["40067652"],"is_preprint":false},{"year":2022,"finding":"MSI1 binds MACF1 mRNA (confirmed by RNA immunoprecipitation) and stabilizes MACF1 expression. MSI1 and MACF1 both increase in high-glucose-induced MC3T3-E1 cells; MSI1-mediated effects on proliferation, apoptosis inhibition, and osteogenic differentiation require MACF1. The MSI1-MACF1 axis suppresses Wnt/β-catenin signaling to promote osteogenic differentiation.","method":"RNA immunoprecipitation (RIP), siRNA knockdown, Western blot, CCK-8 assay, TUNEL assay, ALP activity, alizarin red staining","journal":"Molecular biotechnology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — RIP confirms binding; downstream pathway placement is single-lab without reconstitution or mutagenesis","pmids":["36443618"],"is_preprint":false}],"current_model":"MSI1 is an RNA-binding protein (with WD40-repeat and RRM domains in its yeast/plant forms) that post-transcriptionally represses target mRNAs (including p21, p27, p53, TIMP3, Notch pathway inhibitor NUMB, and MACF1) by binding their 3'UTRs to suppress translation, while also stabilizing select mRNAs (e.g., Fthl17c, SARS-CoV-2 genome), regulating alternative splicing of photoreceptor-specific exons in a dose-dependent manner, and modulating the RAS-cAMP/PKA pathway in yeast by sequestering Npr1p; collectively these activities drive stem cell maintenance, cell cycle progression, EMT, metastasis (via MSI1-TIMP3-MMP9 cascade), radioresistance (via homologous recombination repair), and epigenetic regulation (via an MSI1-FTHL17C-Fe²⁺-TET axis in embryonic stem cells)."},"narrative":{"mechanistic_narrative":"MSI1 is an RNA-binding protein that acts post-transcriptionally to control stem cell maintenance, cell cycle progression, and tumor-associated phenotypes by binding target mRNA 3'UTRs and tuning their translation and stability [PMID:25362645, PMID:34155343]. It directly binds the 3'UTRs of the cell-cycle inhibitors p21, p27, and p53 and represses their translation, promoting S-phase entry; loss of MSI1 raises these proteins and arrests cells in G0/G1 [PMID:25362645, PMID:25394506, PMID:29113163]. The same 3'UTR-directed repression extends to TIMP3, where MSI1 suppression of this MMP9 inhibitor drives an MSI1–TIMP3–MMP9 cascade that promotes invadopodia formation, ECM degradation, and metastasis [PMID:34155343]. MSI1 can also stabilize transcripts: it shields CD44 mRNA from miRNA-dependent decay [PMID:33291443] and binds and stabilizes Fthl17c mRNA, sustaining intracellular Fe²⁺ for TET enzyme activity and thereby coupling iron homeostasis to DNA demethylation in embryonic stem cells [PMID:42089935]. In differentiated neurons, MSI1 together with MSI2 acts in a dose-dependent, partially redundant manner to promote inclusion of photoreceptor-specific alternative exons required for outer segment morphogenesis, ciliogenesis, and synaptic transmission [PMID:33168629]. Beyond direct mRNA control, MSI1 engages effector machinery and signaling pathways—it binds AGO2 via its C-terminus [PMID:35158774] and modulates mTOR, ERK, and PTEN/AKT signaling to influence cell fate, apoptosis resistance, and tissue conversion [PMID:32457396, PMID:25747387, PMID:33758618]. The ancestral yeast ortholog (CAC3/MSI1) is a WD40-repeat protein that negatively regulates RAS-cAMP/PKA signaling by sequestering the kinase Npr1p, a function genetically separable from its role in CAF-I chromatin assembly [PMID:2554329, PMID:11238915, PMID:10975254].","teleology":[{"year":1989,"claim":"Established the founding function of yeast MSI1 as a negative regulator of the RAS-cAMP pathway, placing it within a defined signaling epistasis well before its RNA-binding role was known.","evidence":"High-copy suppressor screen of ira1 heat-shock sensitivity with cAMP measurement in multiple genetic backgrounds","pmids":["2554329"],"confidence":"High","gaps":["Did not define the biochemical mechanism of cAMP suppression","No link to RNA binding or mRNA targets"]},{"year":2000,"claim":"Refined how yeast MSI1 acts on the pathway, showing it modulates PKA function in a BCY1-dependent manner without inhibiting cAMP synthesis, and separated this from CAF-I chromatin assembly.","evidence":"Genetic epistasis across strains plus PKA activity and cAMP assays","pmids":["10975254"],"confidence":"Medium","gaps":["Direct physical target within PKA pathway not identified at this stage","Single lab"]},{"year":2001,"claim":"Identified the molecular basis of RAS/cAMP suppression as sequestration of the kinase Npr1p, establishing a physical mechanism independent of CAF-I.","evidence":"Co-immunoprecipitation, reciprocal genetic epistasis (NPR1 deletion/overexpression), and dual nuclear/cytoplasmic localization","pmids":["11238915"],"confidence":"High","gaps":["Whether sequestration is direct enzymatic inhibition or steric is unresolved","Relevance to metazoan MSI1 function unknown"]},{"year":2007,"claim":"Connected MSI1 nuclear accumulation and a transcriptional reporter activity to YAK1 control, adding a regulatory layer to its yeast signaling role.","evidence":"Yeast two-hybrid, transcriptional reporter, and localization under non-fermentable carbon conditions","pmids":["17321547"],"confidence":"Medium","gaps":["Direct transcriptional targets not identified","Mechanism of YAK1-dependent localization unresolved"]},{"year":2006,"claim":"Showed that MSI1 levels are themselves post-transcriptionally controlled, as neural ELAV/HuD proteins stabilize the Msi1 ARE-containing mRNA to raise Musashi-1 protein.","evidence":"In vitro RNA-protein binding and deadenylation/degradation assays plus pharmacological activation in SH-SY5Y cells","pmids":["16554442"],"confidence":"Medium","gaps":["Physiological contexts where HuD controls MSI1 not defined","Did not address MSI1's own targets"]},{"year":2014,"claim":"Defined the core repressive RNA-binding mechanism of mammalian MSI1, demonstrating direct 3'UTR binding and translational suppression of cell-cycle regulators p21, p27, and p53 to drive proliferation.","evidence":"RNA-protein binding and luciferase 3'UTR reporter assays with gain/loss of function in cervical and colon cancer cells","pmids":["25362645","25394506"],"confidence":"High","gaps":["Binding-site motif consensus not fully mapped","Cofactors required for repression not defined"]},{"year":2017,"claim":"Extended MSI1's repressive activity to cell-cycle control in osteosarcoma and to EMT/Wnt programs, broadening its tumor-promoting role across tissues.","evidence":"Luciferase 3'UTR reporters, shRNA knockdown, invasion/migration assays, and xenografts","pmids":["29113163","28088346"],"confidence":"Medium","gaps":["Whether Wnt regulation is direct via an mRNA target is unresolved","Single lab per study"]},{"year":2020,"claim":"Established a direct, in vivo metastatic mechanism in which MSI1 represses TIMP3 to derepress MMP9, defining the MSI1–TIMP3–MMP9 invadopodia cascade.","evidence":"Direct RNA-binding to Timp3, MMP9 activity and invadopodia assays, lung metastasis model, and clinical correlation","pmids":["34155343"],"confidence":"High","gaps":["Whether other invasion targets contribute is not excluded","Structural basis of Timp3 3'UTR recognition unknown"]},{"year":2020,"claim":"Demonstrated that MSI1 also acts as an mRNA stabilizer, protecting CD44 mRNA from miRNA-dependent decay to support GBM stemness, and that this is pharmacologically targetable.","evidence":"3'UTR reporter and mRNA turnover assays with luteolin inhibitor in GBM tumorsphere models","pmids":["33291443"],"confidence":"Medium","gaps":["Specific miRNAs displaced by MSI1 not defined","Single lab"]},{"year":2020,"claim":"Revealed an epigenetic output of MSI1's RNA-stabilizing activity through the MSI1–FTHL17C–Fe²⁺–TET axis controlling DNA methylation in embryonic stem cells.","evidence":"MSI1 knockout, RNA immunoprecipitation, TET activity and 5mC assays, FTHL17C-TET1 Co-IP, and rescue in mESCs","pmids":["42089935"],"confidence":"Medium","gaps":["Direct structural basis of Fthl17c binding not shown","Generality beyond mESCs unknown"]},{"year":2020,"claim":"Established a distinct nuclear/splicing function in postmitotic neurons, showing MSI1 (with MSI2) is required for photoreceptor-specific exon inclusion essential for outer segment and cilia integrity.","evidence":"Conditional Msi1/Msi2 double knockout mice with ERG electrophysiology, splicing analysis, and histology","pmids":["33168629"],"confidence":"High","gaps":["Direct RNA contacts on splicing targets not mapped","Splicing partners/spliceosomal interface undefined"]},{"year":2020,"claim":"Linked MSI1 overexpression to mTOR-driven cell fate conversion in vivo, identifying a pharmacologically reversible signaling output.","evidence":"Transgenic mice, single-cell RNA-seq, lineage tracing, and rapamycin rescue","pmids":["32457396"],"confidence":"High","gaps":["Direct mRNA target connecting MSI1 to mTOR not identified","Mechanism upstream of mTOR activation unresolved"]},{"year":2021,"claim":"Identified the MSI1 C-terminus as the AGO2 interaction interface and validated it as a druggable node, mechanistically tying MSI1 to miRNA effector machinery.","evidence":"Peptide array and Biacore SPR binding plus competitive peptides in GBM xenografts","pmids":["35158774"],"confidence":"Medium","gaps":["Functional consequence of MSI1-AGO2 binding on specific targets not defined","Single lab"]},{"year":2021,"claim":"Delineated an anti-apoptotic signaling route in which MSI1 lowers PTEN to activate AKT and reduce BAK, with rescue confirming the axis.","evidence":"Gain/loss of function, BAK re-expression rescue, apoptosis assays, and xenografts","pmids":["33758618"],"confidence":"Medium","gaps":["Whether PTEN is a direct MSI1 mRNA target not established","Single lab"]},{"year":2022,"claim":"Mapped functionally required MSI1 phosphorylation sites (T18, S19, S34) and showed that activity, not abundance, governs its role in associative memory.","evidence":"Mass spectrometry PTM mapping with CRISPR point mutations and behavioral assays in C. elegans","pmids":["36223338"],"confidence":"Medium","gaps":["Kinase responsible for these phosphorylations unknown","Effect of phosphorylation on RNA binding not directly measured"]},{"year":2025,"claim":"Established dose-dependent, partially redundant Musashi activity in splicing control, showing a single Msi1 or Msi2 allele suffices to maintain photoreceptor exon inclusion and function.","evidence":"Allelic series of conditional Msi1/Msi2 knockouts with RT-PCR splicing and electrophysiology (preprint)","pmids":["bio_10.1101_2025.11.26.690869"],"confidence":"Medium","gaps":["Quantitative threshold of Musashi dosage not defined","Preprint, single lab"]},{"year":2025,"claim":"Reported a chromatin/transcriptional activity in which MSI1 binds the ABHD2 promoter to activate its transcription and drive prostate cancer glycolysis, distinct from its 3'UTR roles.","evidence":"ChIP and dual-luciferase reporter assays with knockdown, glycolysis measurement, and xenograft","pmids":["40067652"],"confidence":"Medium","gaps":["How a cytoplasmic RNA-binding protein engages DNA/promoters mechanistically is unresolved","Single lab"]},{"year":2024,"claim":"Identified an antiviral function in which MSI1 binds the SARS-CoV-2 3'UTR and represses viral translation by inhibiting PABP, with knockout enhancing viral replication.","evidence":"RNA immunoprecipitation and biochemical binding plus MSI1 knockout in 2D/3D intestinal organoid infection (preprint)","pmids":["bio_10.1101_2024.09.29.615653"],"confidence":"Medium","gaps":["Mechanism of PABP inhibition not structurally defined","Preprint, single lab"]},{"year":null,"claim":"How MSI1 switches between translational repression, mRNA stabilization, splicing regulation, and apparent promoter binding—and how phosphorylation and partner choice (e.g., AGO2, PABP) dictate which output occurs on a given transcript—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model defining context-dependent target selection","Determinants of repression versus stabilization on different 3'UTRs unknown","Mechanistic basis of nuclear splicing versus cytoplasmic translational roles undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[5,12,14,18,20]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[5,6,20]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,13]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,14]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[5,12,13,14]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[5,6,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,9,11,16]}],"complexes":["CAF-I (chromatin assembly factor I)"],"partners":["NPR1","AGO2","HUD/ELAVL4","FTHL17C","MSI2","PABP","MACF1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43347","full_name":"RNA-binding protein Musashi homolog 1","aliases":[],"length_aa":362,"mass_kda":39.1,"function":"RNA binding protein that regulates the expression of target mRNAs at the translation level. Regulates expression of the NOTCH1 antagonist NUMB. Binds RNA containing the sequence 5'-GUUAGUUAGUUAGUU-3' and other sequences containing the pattern 5'-[GA]U(1-3)AGU-3'. May play a role in the proliferation and maintenance of stem cells in the central nervous system (By similarity)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/O43347/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MSI1","classification":"Not Classified","n_dependent_lines":24,"n_total_lines":1208,"dependency_fraction":0.019867549668874173},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MSI1","total_profiled":1310},"omim":[{"mim_id":"607897","title":"MUSASHI RNA BINDING PROTEIN 2; MSI2","url":"https://www.omim.org/entry/607897"},{"mim_id":"603328","title":"MUSASHI RNA BINDING PROTEIN 1; MSI1","url":"https://www.omim.org/entry/603328"},{"mim_id":"602923","title":"RETINOBLASTOMA-BINDING PROTEIN 4; RBBP4","url":"https://www.omim.org/entry/602923"},{"mim_id":"300825","title":"RETINOBLASTOMA-BINDING PROTEIN 7; RBBP7","url":"https://www.omim.org/entry/300825"},{"mim_id":"190060","title":"MOS PROTOONCOGENE, SERINE/THREONINE KINASE; MOS","url":"https://www.omim.org/entry/190060"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in 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encodes a WD40-repeat protein that negatively regulates the RAS-cAMP signaling pathway; overexpression of MSI1 suppresses heat shock sensitivity and reduces elevated intracellular cAMP levels caused by ira1 or RAS2Val19 mutations, but not bcy1 mutations, placing MSI1 upstream of cAMP but downstream of (or parallel to) BCY1.\",\n      \"method\": \"Genetic suppression screen (high-copy plasmid suppressors of ira1 heat-shock sensitivity); cAMP measurement; sporulation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with multiple alleles, cAMP measurement, replicated in multiple genetic backgrounds in a foundational study\",\n      \"pmids\": [\"2554329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"CAC3/MSI1 suppression of the RAS/cAMP pathway is independent of chromatin assembly factor I (CAF-I) subunits CAC1 and CAC2. Cac3p/Msi1p localizes to both nucleus and cytoplasm and physically associates with Npr1p (a cytoplasmic kinase). Deletion of NPR1 phenocopies CAC3 overexpression in suppressing RAS/cAMP, and NPR1 overexpression blocks CAC3-mediated suppression, indicating that excess Cac3p suppresses RAS/cAMP by sequestering Npr1p.\",\n      \"method\": \"Genetic epistasis (double mutants), co-immunoprecipitation/association assay, localization studies, suppression analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genetic and biochemical methods, reciprocal epistasis, subcellular localization linked to function\",\n      \"pmids\": [\"11238915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"MSI1 overexpression suppresses hyperactive RAS phenotypes in multiple genetic backgrounds but does not inhibit cAMP synthesis or total cellular PKA activity. MSI1 requires the PKA regulatory subunit BCY1 to inhibit a mutationally activated PKA catalytic subunit, indicating that MSI1 modulates PKA function in a BCY1-dependent manner. MSI1's RAS-suppressing function is separable from its role in CAF-I chromatin assembly.\",\n      \"method\": \"Genetic analysis (multiple yeast strains, epistasis), PKA activity assay, cAMP measurement\",\n      \"journal\": \"Current genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in multiple backgrounds, biochemical PKA/cAMP assays, single lab\",\n      \"pmids\": [\"10975254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MSI1 (CAC3) genetically interacts with YAK1 (a kinase antagonizing RAS/cAMP). MSI1 suppresses heat-shock sensitivity from yak1 deletion. YAK1 is required for Msi1p association with Cac1p (yeast two-hybrid). Msi1p can activate transcription of a reporter when tethered near a promoter in non-fermentable carbon conditions, and this activity requires YAK1. YAK1 antagonizes nuclear accumulation of Msi1p in non-fermenting cells.\",\n      \"method\": \"Yeast two-hybrid, genetic suppression, transcriptional reporter assay, localization analysis\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Y2H, reporter, localization), single lab\",\n      \"pmids\": [\"17321547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Neural ELAV proteins (HuD) bind the AU-rich element (ARE) in the Msi1 mRNA 3'UTR in an ARE-dependent manner, stabilize the Msi1 ARE-containing mRNA in a deadenylation/degradation assay, and increase Musashi-1 protein levels. Activation of neural ELAV proteins by phorbol esters in SH-SY5Y cells increases Musashi-1 protein in the cytoskeleton.\",\n      \"method\": \"RNA-protein binding assay, mRNA deadenylation/degradation assay, immunofluorescence co-localization, pharmacological activation\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro RNA-binding and functional mRNA stability assay plus cell-based validation, single lab\",\n      \"pmids\": [\"16554442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MSI1 directly binds the 3'UTR of p21, p27, and p53 mRNAs (verified by RNA-protein binding assays) and suppresses their translation (confirmed by luciferase 3'UTR reporter assays). Overexpression of Msi1 in cervical cancer cells downregulates p21, p27, and p53 protein levels and promotes cell cycle S-phase entry, whereas shRNA knockdown upregulates these proteins and slows S-phase entry.\",\n      \"method\": \"RNA-protein binding assay, luciferase 3'UTR reporter assay, shRNA knockdown, Western blot, flow cytometry\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct RNA-binding plus luciferase reporter plus protein level changes with gain/loss of function, two orthogonal functional assays\",\n      \"pmids\": [\"25362645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Msi1 directly suppresses translation of p21cip1 mRNA via its 3'UTR-specific motif, as demonstrated by a chimeric luciferase-p21cip1 3'UTR reporter assay. Knockdown of Msi1 in colon cancer cells increases p21cip1 protein, induces G0/G1 arrest, and suppresses proliferation and tumorsphere formation.\",\n      \"method\": \"Luciferase chimeric mRNA 3'UTR reporter assay, RNAi knockdown, Western blot, flow cytometry, in vivo xenograft\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter with specific motif plus loss-of-function phenotype, single lab\",\n      \"pmids\": [\"25394506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Msi1 promotes epithelial-to-mesenchymal transition (EMT) in cervical cancer cells; shRNA silencing of Msi1 reduces EMT marker expression and inhibits Wnt signaling activity, while Msi1 expression positively correlates with EMT markers in clinical tissues.\",\n      \"method\": \"shRNA knockdown, Western blot, invasion/migration assay, in vivo tumor assay, immunohistochemistry\",\n      \"journal\": \"Human pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined phenotype and pathway (Wnt/EMT), single lab, no reconstitution\",\n      \"pmids\": [\"28088346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MSI1 knockdown in osteosarcoma cells causes G0/G1 cell cycle arrest and upregulation of p21 and p27 protein levels. Luciferase assays confirm that MSI1 binds the 3'UTR of both p21 and p27 mRNAs.\",\n      \"method\": \"shRNA knockdown, luciferase 3'UTR reporter assay, Western blot, flow cytometry, in vivo xenograft\",\n      \"journal\": \"Oncology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter plus loss-of-function phenotype, single lab\",\n      \"pmids\": [\"29113163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Msi1 confers TRAIL resistance in hepatocellular carcinoma cells by activating ERK; forced Msi1 expression increases ERK activation and TRAIL resistance, and siRNA depletion of ERK overcomes Msi1-mediated TRAIL resistance. Differential AKT activation was not responsible.\",\n      \"method\": \"Stable subline isolation, shRNA/siRNA knockdown, forced expression, TRAIL resistance assays in vitro and in vivo xenograft\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with mechanistic pathway (ERK) validation, single lab\",\n      \"pmids\": [\"25747387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MSI1 enhances GBM radioresistance by increasing homologous recombination (HR) DNA repair and promoting VCAM1-mediated tumor invasion; MSI1 knockdown causes DNA damage accumulation in irradiated GBM cells and reduces xenograft tumor formation after irradiation.\",\n      \"method\": \"shRNA knockdown, overexpression, irradiation assays, DNA damage markers (γH2AX), invasion assay, xenograft\",\n      \"journal\": \"Radiotherapy and oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss of function with DNA repair readout and invasion marker VCAM1, single lab\",\n      \"pmids\": [\"30322656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The Msi1-mTOR pathway drives keratinocyte-to-Paget-like cell conversion; Msi1 overexpression in epidermal basal cells activates mTOR signaling, and mTOR inhibition with rapamycin rescues the Paget-like phenotype in Msi1-overexpressing transgenic mice.\",\n      \"method\": \"Transgenic mouse model, single-cell RNA-sequencing, lineage tracing, rapamycin treatment, RNA velocity analysis\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic gain-of-function, pharmacological pathway rescue, multiple orthogonal methods including scRNA-seq and lineage tracing\",\n      \"pmids\": [\"32457396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MSI1 promotes breast cancer metastasis by directly suppressing TIMP3 mRNA (an endogenous inhibitor of MMP9), leading to increased MMP9 expression and activity, invadopodia formation, and ECM degradation. The MSI1-TIMP3-MMP9 cascade is required for invadopodia-mediated metastasis.\",\n      \"method\": \"shRNA knockdown, overexpression, RNA-binding assay (direct suppression of Timp3), MMP9 activity assay, invadopodia assay, in vivo lung metastasis model, clinical correlation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct RNA binding to Timp3 established, mechanistic cascade (MSI1→TIMP3→MMP9) validated by multiple functional assays and in vivo metastasis model\",\n      \"pmids\": [\"34155343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MSI1 promotes expression of the GBM stem cell marker CD44 by impairing miRNA-dependent degradation of CD44 mRNA via its 3'UTR; this regulation is disrupted by the MSI1 inhibitor luteolin.\",\n      \"method\": \"Knockdown and overexpression, 3'UTR reporter assay, mRNA turnover assay, luteolin inhibitor treatment, GBM cell and primary tumorsphere models\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — 3'UTR-dependent mRNA stabilization mechanism, pharmacological inhibitor, single lab\",\n      \"pmids\": [\"33291443\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MSI1 directly binds and stabilizes the Fthl17c mRNA; MSI1 ablation in mESCs reduces Fthl17c expression, decreasing intracellular Fe2⁺, impairing TET enzyme activity, and increasing global DNA methylation (5mC). FTHL17C interacts with TET1 in the nucleus. Restoration of Fthl17c rescues TET activity and pluripotency gene expression, defining an MSI1-FTHL17C-Fe2⁺-TET axis linking post-transcriptional iron homeostasis control with epigenetic remodeling.\",\n      \"method\": \"Genetic ablation (MSI1 knockout), RNA immunoprecipitation, biochemical TET activity assay, DNA methylation (5mC) measurement, co-immunoprecipitation (FTHL17C-TET1), rescue experiments, fluorescence imaging\",\n      \"journal\": \"Cell regeneration (London, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RIP, TET assay, 5mC, Co-IP, rescue), single lab, preprint-adjacent but published\",\n      \"pmids\": [\"42089935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MSI1 interacts with AGO2 via its C-terminus; peptides mimicking the C-terminus of MSI1 (Pep#11 and Pep#26) competitively interfere with MSI1-AGO2 binding (confirmed by Biacore binding analyses), reduce GBM tumorigenesis, and improve survival in GBM animal models.\",\n      \"method\": \"Peptide array, Biacore surface plasmon resonance, recombinant reporter system, in vivo GBM xenograft model\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — SPR binding assay plus in vivo functional validation, single lab\",\n      \"pmids\": [\"35158774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MSI1 inhibits cervical cancer cell apoptosis by downregulating PTEN, thereby activating AKT signaling, which reduces the proapoptotic protein BAK; rescue of BAK expression in Msi1-expressing cells restores apoptosis.\",\n      \"method\": \"Overexpression, shRNA knockdown, Western blot, apoptosis assay, rescue experiment (BAK re-expression), in vivo xenograft\",\n      \"journal\": \"Journal of Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pathway delineated (MSI1→PTEN suppression→AKT→BAK), rescue validates mechanism, single lab\",\n      \"pmids\": [\"33758618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MSI1 phosphorylation at residues T18, S19, and S34 (identified by mass spectrometry in C. elegans MSI-1) is necessary for MSI-1 function in both short- and long-term aversive olfactory associative memory; CRISPR-based manipulation of these phosphorylation sites abolishes memory-related MSI-1 function. MSI-1 function is controlled by activity rather than expression levels.\",\n      \"method\": \"Mass spectrometry phosphorylation mapping, CRISPR-based point mutations, behavioral assays (short- and long-term memory)\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass spectrometry-identified PTM sites validated by CRISPR mutagenesis with functional readout, C. elegans ortholog study\",\n      \"pmids\": [\"36223338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In photoreceptor neurons, both MSI1 and MSI2 are required for inclusion of photoreceptor-specific alternative exons in transcripts critical for outer segment morphogenesis (Cc2d2a, Cep290, Prom1, Ttc8), ciliogenesis, and synaptic transmission. Loss of both Msi1 and Msi2 causes disrupted outer segment morphology, ciliary defects, loss of light response, and photoreceptor degeneration within 6 months.\",\n      \"method\": \"Conditional double knockout mouse (pan-retinal and rod-specific), electrophysiology (ERG), RNA splicing analysis, immunofluorescence, histology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO mouse with defined molecular splicing phenotype, electrophysiological functional readout, and morphological analysis; multiple orthogonal methods\",\n      \"pmids\": [\"33168629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A single Musashi allele (from either Msi1 or Msi2) is sufficient to maintain photoreceptor function and high inclusion levels of photoreceptor-specific alternative exons (in Cc2d2a, Cep290, Prom1, Ttc8), demonstrating that the Musashi proteins act in a dose-dependent, partially redundant manner to regulate alternative splicing specifically in photoreceptors.\",\n      \"method\": \"Combined conditional Msi1/Msi2 knockouts with progressive allele reduction, RT-PCR splicing analysis, electrophysiology\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — allelic series with functional splicing and electrophysiological readout, single lab, preprint\",\n      \"pmids\": [\"bio_10.1101_2025.11.26.690869\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MSI1 directly binds the SARS-CoV-2 3'UTR (confirmed by in vivo RNA immunoprecipitation and biochemical assays), and this binding results in translational repression mediated by inhibition of Poly(A)-binding protein (PABP). MSI1 knockout promotes robust viral replication and increased viral protein expression in intestinal cells, stem cells, and 3D organoids.\",\n      \"method\": \"Computational prediction, RNA immunoprecipitation (RIP), biochemical binding assay, MSI1 knockout cell lines, 2D and 3D organoid infection assays, viral protein expression quantification\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP plus biochemical assay plus functional KO phenotype, multi-model validation, single lab, preprint\",\n      \"pmids\": [\"bio_10.1101_2024.09.29.615653\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Hedgehog signaling agonist (purmorphamine) enhances mesenchymal stem cell proliferation and suppresses apoptosis through the RNA-binding protein Msi1, which regulates c-Myc oncoprotein expression and p21CIP1 cell cycle regulator, and modulates miRNA-148a and miRNA-148b.\",\n      \"method\": \"Hedgehog agonist/antagonist treatment, MSI1 knockdown/overexpression, Western blot, proliferation and apoptosis assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pathway placement inferred from pharmacological activation and single knockdown experiments, no direct binding assay for downstream targets, single lab\",\n      \"pmids\": [\"23418578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Hedgehog signaling negatively regulates osteogenic differentiation of mesenchymal stem cells through Msi1, which suppresses Wnt1 expression and the miR-148 family (especially miR-148b).\",\n      \"method\": \"Hedgehog agonist/antagonist treatment, Msi1 knockdown/overexpression, osteogenic differentiation assays, qRT-PCR\",\n      \"journal\": \"Bone\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological and knockdown data without direct binding assays, single lab\",\n      \"pmids\": [\"23880227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MSI1 binds to the ABHD2 promoter region and activates ABHD2 transcription (confirmed by dual-luciferase reporter and ChIP assays), thereby promoting prostate cancer cell proliferation, migration, and glycolysis.\",\n      \"method\": \"ChIP assay, dual-luciferase reporter assay, siRNA knockdown, EdU proliferation assay, flow cytometry, transwell assay, glycolysis measurement, xenograft\",\n      \"journal\": \"Biochemical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and luciferase reporter confirm direct MSI1 binding to ABHD2 promoter, loss-of-function phenotype confirmed in vitro and in vivo, single lab\",\n      \"pmids\": [\"40067652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MSI1 binds MACF1 mRNA (confirmed by RNA immunoprecipitation) and stabilizes MACF1 expression. MSI1 and MACF1 both increase in high-glucose-induced MC3T3-E1 cells; MSI1-mediated effects on proliferation, apoptosis inhibition, and osteogenic differentiation require MACF1. The MSI1-MACF1 axis suppresses Wnt/β-catenin signaling to promote osteogenic differentiation.\",\n      \"method\": \"RNA immunoprecipitation (RIP), siRNA knockdown, Western blot, CCK-8 assay, TUNEL assay, ALP activity, alizarin red staining\",\n      \"journal\": \"Molecular biotechnology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — RIP confirms binding; downstream pathway placement is single-lab without reconstitution or mutagenesis\",\n      \"pmids\": [\"36443618\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MSI1 is an RNA-binding protein (with WD40-repeat and RRM domains in its yeast/plant forms) that post-transcriptionally represses target mRNAs (including p21, p27, p53, TIMP3, Notch pathway inhibitor NUMB, and MACF1) by binding their 3'UTRs to suppress translation, while also stabilizing select mRNAs (e.g., Fthl17c, SARS-CoV-2 genome), regulating alternative splicing of photoreceptor-specific exons in a dose-dependent manner, and modulating the RAS-cAMP/PKA pathway in yeast by sequestering Npr1p; collectively these activities drive stem cell maintenance, cell cycle progression, EMT, metastasis (via MSI1-TIMP3-MMP9 cascade), radioresistance (via homologous recombination repair), and epigenetic regulation (via an MSI1-FTHL17C-Fe²⁺-TET axis in embryonic stem cells).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MSI1 is an RNA-binding protein that acts post-transcriptionally to control stem cell maintenance, cell cycle progression, and tumor-associated phenotypes by binding target mRNA 3'UTRs and tuning their translation and stability [#5, #12]. It directly binds the 3'UTRs of the cell-cycle inhibitors p21, p27, and p53 and represses their translation, promoting S-phase entry; loss of MSI1 raises these proteins and arrests cells in G0/G1 [#5, #6, #8]. The same 3'UTR-directed repression extends to TIMP3, where MSI1 suppression of this MMP9 inhibitor drives an MSI1–TIMP3–MMP9 cascade that promotes invadopodia formation, ECM degradation, and metastasis [#12]. MSI1 can also stabilize transcripts: it shields CD44 mRNA from miRNA-dependent decay [#13] and binds and stabilizes Fthl17c mRNA, sustaining intracellular Fe²⁺ for TET enzyme activity and thereby coupling iron homeostasis to DNA demethylation in embryonic stem cells [#14]. In differentiated neurons, MSI1 together with MSI2 acts in a dose-dependent, partially redundant manner to promote inclusion of photoreceptor-specific alternative exons required for outer segment morphogenesis, ciliogenesis, and synaptic transmission [#18]. Beyond direct mRNA control, MSI1 engages effector machinery and signaling pathways—it binds AGO2 via its C-terminus [#15] and modulates mTOR, ERK, and PTEN/AKT signaling to influence cell fate, apoptosis resistance, and tissue conversion [#11, #9, #16]. The ancestral yeast ortholog (CAC3/MSI1) is a WD40-repeat protein that negatively regulates RAS-cAMP/PKA signaling by sequestering the kinase Npr1p, a function genetically separable from its role in CAF-I chromatin assembly [#0, #1, #2].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Established the founding function of yeast MSI1 as a negative regulator of the RAS-cAMP pathway, placing it within a defined signaling epistasis well before its RNA-binding role was known.\",\n      \"evidence\": \"High-copy suppressor screen of ira1 heat-shock sensitivity with cAMP measurement in multiple genetic backgrounds\",\n      \"pmids\": [\"2554329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the biochemical mechanism of cAMP suppression\", \"No link to RNA binding or mRNA targets\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Refined how yeast MSI1 acts on the pathway, showing it modulates PKA function in a BCY1-dependent manner without inhibiting cAMP synthesis, and separated this from CAF-I chromatin assembly.\",\n      \"evidence\": \"Genetic epistasis across strains plus PKA activity and cAMP assays\",\n      \"pmids\": [\"10975254\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical target within PKA pathway not identified at this stage\", \"Single lab\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified the molecular basis of RAS/cAMP suppression as sequestration of the kinase Npr1p, establishing a physical mechanism independent of CAF-I.\",\n      \"evidence\": \"Co-immunoprecipitation, reciprocal genetic epistasis (NPR1 deletion/overexpression), and dual nuclear/cytoplasmic localization\",\n      \"pmids\": [\"11238915\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether sequestration is direct enzymatic inhibition or steric is unresolved\", \"Relevance to metazoan MSI1 function unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Connected MSI1 nuclear accumulation and a transcriptional reporter activity to YAK1 control, adding a regulatory layer to its yeast signaling role.\",\n      \"evidence\": \"Yeast two-hybrid, transcriptional reporter, and localization under non-fermentable carbon conditions\",\n      \"pmids\": [\"17321547\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct transcriptional targets not identified\", \"Mechanism of YAK1-dependent localization unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Showed that MSI1 levels are themselves post-transcriptionally controlled, as neural ELAV/HuD proteins stabilize the Msi1 ARE-containing mRNA to raise Musashi-1 protein.\",\n      \"evidence\": \"In vitro RNA-protein binding and deadenylation/degradation assays plus pharmacological activation in SH-SY5Y cells\",\n      \"pmids\": [\"16554442\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological contexts where HuD controls MSI1 not defined\", \"Did not address MSI1's own targets\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the core repressive RNA-binding mechanism of mammalian MSI1, demonstrating direct 3'UTR binding and translational suppression of cell-cycle regulators p21, p27, and p53 to drive proliferation.\",\n      \"evidence\": \"RNA-protein binding and luciferase 3'UTR reporter assays with gain/loss of function in cervical and colon cancer cells\",\n      \"pmids\": [\"25362645\", \"25394506\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding-site motif consensus not fully mapped\", \"Cofactors required for repression not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended MSI1's repressive activity to cell-cycle control in osteosarcoma and to EMT/Wnt programs, broadening its tumor-promoting role across tissues.\",\n      \"evidence\": \"Luciferase 3'UTR reporters, shRNA knockdown, invasion/migration assays, and xenografts\",\n      \"pmids\": [\"29113163\", \"28088346\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Wnt regulation is direct via an mRNA target is unresolved\", \"Single lab per study\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a direct, in vivo metastatic mechanism in which MSI1 represses TIMP3 to derepress MMP9, defining the MSI1–TIMP3–MMP9 invadopodia cascade.\",\n      \"evidence\": \"Direct RNA-binding to Timp3, MMP9 activity and invadopodia assays, lung metastasis model, and clinical correlation\",\n      \"pmids\": [\"34155343\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other invasion targets contribute is not excluded\", \"Structural basis of Timp3 3'UTR recognition unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated that MSI1 also acts as an mRNA stabilizer, protecting CD44 mRNA from miRNA-dependent decay to support GBM stemness, and that this is pharmacologically targetable.\",\n      \"evidence\": \"3'UTR reporter and mRNA turnover assays with luteolin inhibitor in GBM tumorsphere models\",\n      \"pmids\": [\"33291443\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific miRNAs displaced by MSI1 not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed an epigenetic output of MSI1's RNA-stabilizing activity through the MSI1–FTHL17C–Fe²⁺–TET axis controlling DNA methylation in embryonic stem cells.\",\n      \"evidence\": \"MSI1 knockout, RNA immunoprecipitation, TET activity and 5mC assays, FTHL17C-TET1 Co-IP, and rescue in mESCs\",\n      \"pmids\": [\"42089935\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct structural basis of Fthl17c binding not shown\", \"Generality beyond mESCs unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established a distinct nuclear/splicing function in postmitotic neurons, showing MSI1 (with MSI2) is required for photoreceptor-specific exon inclusion essential for outer segment and cilia integrity.\",\n      \"evidence\": \"Conditional Msi1/Msi2 double knockout mice with ERG electrophysiology, splicing analysis, and histology\",\n      \"pmids\": [\"33168629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct RNA contacts on splicing targets not mapped\", \"Splicing partners/spliceosomal interface undefined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Linked MSI1 overexpression to mTOR-driven cell fate conversion in vivo, identifying a pharmacologically reversible signaling output.\",\n      \"evidence\": \"Transgenic mice, single-cell RNA-seq, lineage tracing, and rapamycin rescue\",\n      \"pmids\": [\"32457396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mRNA target connecting MSI1 to mTOR not identified\", \"Mechanism upstream of mTOR activation unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified the MSI1 C-terminus as the AGO2 interaction interface and validated it as a druggable node, mechanistically tying MSI1 to miRNA effector machinery.\",\n      \"evidence\": \"Peptide array and Biacore SPR binding plus competitive peptides in GBM xenografts\",\n      \"pmids\": [\"35158774\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of MSI1-AGO2 binding on specific targets not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Delineated an anti-apoptotic signaling route in which MSI1 lowers PTEN to activate AKT and reduce BAK, with rescue confirming the axis.\",\n      \"evidence\": \"Gain/loss of function, BAK re-expression rescue, apoptosis assays, and xenografts\",\n      \"pmids\": [\"33758618\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PTEN is a direct MSI1 mRNA target not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Mapped functionally required MSI1 phosphorylation sites (T18, S19, S34) and showed that activity, not abundance, governs its role in associative memory.\",\n      \"evidence\": \"Mass spectrometry PTM mapping with CRISPR point mutations and behavioral assays in C. elegans\",\n      \"pmids\": [\"36223338\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase responsible for these phosphorylations unknown\", \"Effect of phosphorylation on RNA binding not directly measured\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established dose-dependent, partially redundant Musashi activity in splicing control, showing a single Msi1 or Msi2 allele suffices to maintain photoreceptor exon inclusion and function.\",\n      \"evidence\": \"Allelic series of conditional Msi1/Msi2 knockouts with RT-PCR splicing and electrophysiology (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.11.26.690869\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative threshold of Musashi dosage not defined\", \"Preprint, single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Reported a chromatin/transcriptional activity in which MSI1 binds the ABHD2 promoter to activate its transcription and drive prostate cancer glycolysis, distinct from its 3'UTR roles.\",\n      \"evidence\": \"ChIP and dual-luciferase reporter assays with knockdown, glycolysis measurement, and xenograft\",\n      \"pmids\": [\"40067652\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a cytoplasmic RNA-binding protein engages DNA/promoters mechanistically is unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified an antiviral function in which MSI1 binds the SARS-CoV-2 3'UTR and represses viral translation by inhibiting PABP, with knockout enhancing viral replication.\",\n      \"evidence\": \"RNA immunoprecipitation and biochemical binding plus MSI1 knockout in 2D/3D intestinal organoid infection (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.09.29.615653\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of PABP inhibition not structurally defined\", \"Preprint, single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MSI1 switches between translational repression, mRNA stabilization, splicing regulation, and apparent promoter binding—and how phosphorylation and partner choice (e.g., AGO2, PABP) dictate which output occurs on a given transcript—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model defining context-dependent target selection\", \"Determinants of repression versus stabilization on different 3'UTRs unknown\", \"Mechanistic basis of nuclear splicing versus cytoplasmic translational roles undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [5, 12, 14, 18, 20]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [5, 6, 20]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 14]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [5, 12, 13, 14]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [5, 6, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 9, 11, 16]}\n    ],\n    \"complexes\": [\n      \"CAF-I (chromatin assembly factor I)\"\n    ],\n    \"partners\": [\n      \"NPR1\",\n      \"AGO2\",\n      \"HuD/ELAVL4\",\n      \"FTHL17C\",\n      \"MSI2\",\n      \"PABP\",\n      \"MACF1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}