{"gene":"DDX1","run_date":"2026-06-09T23:54:41","timeline":{"discoveries":[{"year":2011,"finding":"DDX1, DDX21, and DHX36 form a cytosolic complex with the adaptor TRIF to sense dsRNA in myeloid dendritic cells; DDX1 binds poly I:C via its Helicase A domain, while DHX36 and DDX21 bind the TIR domain of TRIF via their HA2-DUF and PRK domains, respectively. Knockdown of DDX1 blocked type I IFN and cytokine responses to poly I:C, influenza A virus, and reovirus.","method":"Isolation/sequencing of poly I:C-binding proteins, shRNA knockdown, domain mapping, cytosolic localization confirmed independently of endosomes","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, domain mapping, functional knockdown with defined IFN phenotype, replicated across multiple viral stimuli","pmids":["21703541"],"is_preprint":false},{"year":2014,"finding":"Phosphorylation of the coronavirus nucleocapsid (N) protein by GSK-3 recruits RNA helicase DDX1 to the N-containing complex, facilitating template readthrough during transcription and enabling synthesis of longer subgenomic mRNAs and full-length genomic RNA. DDX1 knockdown or loss of helicase activity markedly reduces longer sgmRNA levels.","method":"GSK-3 inhibition, DDX1 knockdown, helicase-dead mutant expression, quantitative RT-PCR for sgmRNA species","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (pharmacological inhibition, KD, dominant-negative mutant) with defined molecular phenotype","pmids":["25299332"],"is_preprint":false},{"year":2018,"finding":"DDX1 binds G-quadruplex (G4) structures in intronic switch transcripts at the IgH locus and converts them into R-loops, thereby targeting AID to S-regions to promote class switch recombination (CSR). An ATPase-deficient DDX1 mutant acts as dominant-negative, reducing R-loop levels over S-regions and CSR efficiency.","method":"In vivo CSR assays, chemical G4 stabilization, ATPase-deficient dominant-negative mutant, R-loop immunoprecipitation","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal approaches (chemical perturbation, catalytic mutant, in vivo CSR), rigorous mechanistic dissection","pmids":["29731414"],"is_preprint":false},{"year":2014,"finding":"DDX1 is a component of the human tRNA splicing ligase complex (tRNA-LC); together with archease, DDX1 facilitates formation of the RTCB-guanylate intermediate central to mammalian RNA ligation, defining DDX1's enzymatic role within this complex.","method":"Eukaryotic orthologous group analysis, biochemical complementation assay for RTCB-guanylate intermediate formation","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution of intermediate formation, single lab but rigorous enzymatic assay","pmids":["24870230"],"is_preprint":false},{"year":2010,"finding":"DDX1 interacts with coronavirus (IBV and SARS-CoV) nonstructural protein 14 (nsp14); the interaction maps to the C-terminal region of DDX1 (motifs V and VI) and the N-terminal portion of nsp14. DDX1 is relocalized from nucleus to cytoplasm upon IBV infection, and either siRNA knockdown or overexpression of a DDX1 mutant reduced IBV replication.","method":"Yeast two-hybrid, co-immunoprecipitation, siRNA knockdown, subcellular fractionation/immunofluorescence, viral replication assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP confirmed in infected cells, domain mapping, functional KD with replication phenotype, two coronavirus orthologs tested","pmids":["20573827"],"is_preprint":false},{"year":2014,"finding":"DDX1 promotes maturation of a subset of primary miRNAs (including miR-200 family members) by functioning as a regulatory component of the Drosha/DGCR8 microprocessor. ATM-mediated phosphorylation of DDX1 facilitates this induction after DNA damage. DDX1 inhibition promotes ovarian tumor growth and metastasis in a syngeneic mouse model.","method":"RNA-IP, miRNA profiling, ATM kinase assays, DDX1 knockdown/overexpression, syngeneic mouse tumor model","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (RNA-IP, kinase assay, in vivo mouse model), ATM identified as upstream kinase","pmids":["25176654"],"is_preprint":false},{"year":2001,"finding":"DDX1 colocalizes with cleavage stimulation factor CstF-64 in nuclear cleavage bodies and resides within 10 nm of CstF-64 (demonstrated by FRET). Co-immunoprecipitation shows DDX1 is in the same complex as CstF-64, implicating DDX1 in 3'-end cleavage and polyadenylation of pre-mRNAs.","method":"Immunofluorescence, fluorescence resonance energy transfer (FRET), co-immunoprecipitation","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — FRET (< 10 nm proximity) plus Co-IP, two independent methods establishing physical association","pmids":["11598190"],"is_preprint":false},{"year":2002,"finding":"DDX1 physically interacts with hnRNP K via the N-terminal 1–276 amino acids of hnRNP K; this interaction is disrupted by poly(A), poly(C), and poly(U) RNA substrates. DDX1 is a homopolymeric poly(A) RNA-binding protein whose ATPase activity is stimulated by homopolymeric RNAs and total yeast RNA but not by DNA. The immunoprecipitated DDX1 complex (but not purified DDX1 alone) unwinds dsRNA with single-stranded poly(A) overhangs.","method":"GST affinity chromatography, LC-MS/MS, in vitro binding assay, co-immunoprecipitation, ATPase assay, RNA unwinding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ATPase and unwinding assays plus domain mapping and Co-IP, multiple orthogonal methods","pmids":["12183465"],"is_preprint":false},{"year":2011,"finding":"DDX1 is an RNA-activated ATPase that binds HIV-1 Rev in an RNA-independent manner and forms complexes with Rev-bound RNA. DDX1 is required for both Rev activity and HIV-1 production from infected cells (demonstrated by RNA silencing). Rev-bound RNA is equally effective as protein-free RNA at stimulating DDX1 ATPase activity.","method":"Recombinant protein biochemistry, gel-filtration, CD spectroscopy, fluorescent Rev binding assay, cell-based Co-IP, ATPase assay, gel mobility shift, siRNA knockdown, HIV production assay","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro ATPase reconstitution, direct binding assay, cell-based functional knockdown, multiple orthogonal methods in a single rigorous study","pmids":["22051512"],"is_preprint":false},{"year":2011,"finding":"DDX1 promotes oligomerization of HIV-1 Rev on the Rev response element (RRE) by eliminating nonproductive nucleation events and accelerating early Rev monomer binding steps, without altering dissociation rates. This effect is enhanced by non-hydrolyzable ATP (AMP-PNP) but not ADP. DDX1 targets Rev rather than the RRE and can rescue oligomerization of a Rev mutant that cannot assemble beyond a monomer.","method":"Single-molecule total internal reflection fluorescence microscopy (TIRF), fluorescently labeled Rev, real-time Rev-RRE assembly/dissociation kinetics","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-molecule reconstitution with kinetic dissection, mechanistically rigorous, single lab","pmids":["21763499"],"is_preprint":false},{"year":2009,"finding":"DDX1 interacts with NF-κB subunit RelA (p65) and acts as a co-activator to enhance NF-κB-mediated transcription. The interaction maps to the C-terminal transactivation domain of RelA and the N-terminal ATPase/helicase domain of DDX1. A DDX1 dominant-negative mutant lacking ATPase/helicase activity loses transcriptional co-activator function.","method":"Mammalian two-hybrid, co-immunoprecipitation, confocal microscopy, chromatin immunoprecipitation, NF-κB reporter gene assay, siRNA knockdown, domain mapping","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (two-hybrid, Co-IP, ChIP, reporter assay) in a single lab study","pmids":["19058135"],"is_preprint":false},{"year":2005,"finding":"DDX1 functions as a cellular co-factor for HIV-1 Rev in the nucleus/nucleolus; low endogenous DDX1 in human astrocytes shifts Rev localization from nuclear/nucleolar to cytoplasmic dominance. Exogenous DDX1 expression in astrocytes restores nuclear Rev localization and increases HIV-1 viral production.","method":"HIV-1 pseudotyped infection, semi-quantitative RT-PCR for spliced/unspliced RNA, DDX1 overexpression, Rev immunofluorescence localization","journal":"Virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional rescue experiment with Rev localization readout plus viral RNA quantification, single lab","pmids":["15892970"],"is_preprint":false},{"year":2015,"finding":"DDX1 bodies, cleavage bodies, Cajal bodies, and gems are distinct nuclear suborganelles whose associations are cell-cycle-regulated; CstF-64-containing cleavage bodies are primarily found during S phase and are sensitive to DNA replication inhibitors; all four bodies associate during S phase with cleavage bodies colocalizing with DDX1 bodies. Latrunculin B (actin polymerization inhibitor) causes formation of nuclear spicules containing CstF-64, CPSF-100, RNA, and RNA Pol II.","method":"Immunofluorescence throughout cell cycle, inhibitors of transcription/DNA replication/actin polymerization, live-cell imaging","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic cell-cycle imaging with pharmacological perturbations, single lab, localization tied to functional context","pmids":["16371507"],"is_preprint":false},{"year":1998,"finding":"DDX1 protein is found in both nucleus and cytoplasm of DDX1-amplified neuroblastoma and retinoblastoma cell lines, but is localized primarily to the nucleus of non-amplified cells, establishing overexpression-dependent cytoplasmic redistribution.","method":"Immunofluorescence with polyclonal anti-DDX1 antibodies, Western blot, Northern blot","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization by immunofluorescence across multiple cell lines; functional consequence inferred but not directly tested","pmids":["9694872"],"is_preprint":false},{"year":2015,"finding":"Biochemical characterization of DDX1 shows exceptionally tight ADP binding (three orders of magnitude tighter than ATP), arresting the enzyme in a potential ADP dead-end conformation, suggesting DDX1 requires a nucleotide exchange factor for recycling. Strong cooperativity in RNA and ATP binding to DDX1 was observed, where either ligand alone partially shifts the enzyme from 'open' to 'closed' state.","method":"Equilibrium titrations, transient kinetics, nucleotide binding assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinetic reconstitution with multiple binding assays, rigorous quantitative characterization, single lab","pmids":["25690890"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of the SPRY domain of human DDX1 (hDSPRY) resolved at 2.0 Å reveals two layers of concave antiparallel β-sheets and a conserved patch of positive surface charge proposed as a protein–protein interaction surface, providing the first structural information on any DDX1 domain.","method":"X-ray crystallography at 2.0 Å resolution","journal":"Acta crystallographica. Section F, Structural biology communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure at atomic resolution; functional validation of interaction surface is partial (structural inference), single lab","pmids":["26323305"],"is_preprint":false},{"year":2015,"finding":"Drosophila Ddx1 null flies are viable but reduced in size, with females showing reduced fertility due to egg chamber autophagy and males being sterile due to disrupted spermatogenesis. Ddx1 directly binds Sirup mRNA and regulates its differential splicing; double mutant (Ddx1 null + Sirup RNAi) causes epistatic lethality not seen in single mutants, suggesting Ddx1 acts in a stress-induced splicing pathway involving Sirup.","method":"Drosophila null mutation, comparative RNA-seq, RNA binding assay (Sirup mRNA), genetic epistasis with dsRNA knockdown","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with null allele and defined splicing target, multiple phenotypic readouts, ortholog of human DDX1","pmids":["26433063"],"is_preprint":false},{"year":2015,"finding":"Homozygous Ddx1 knockout in mice causes embryonic lethality prior to E3.5, with embryos stalling at the 2-4 cell stage. Heterozygote crosses reveal a transgenerational wild-type lethality phenotype transmitted through Ddx1*(/-) parents independently of sex, via a non-genetic mechanism.","method":"Constitutive Ddx1 knockout mouse generation, embryo staging, genotyping of progeny from heterozygote crosses","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined embryonic lethal phenotype in KO mice with stage-specific stalling; transgenerational mechanism not molecularly resolved","pmids":["25909345"],"is_preprint":false},{"year":2019,"finding":"DDX1 protein localizes exclusively to cytoplasmic granules in oocytes and early mouse embryos, requiring RNA for retention at these sites. Homozygous Ddx1 KO causes stalling at 2-4 cell stages. DDX1 RNA-immunoprecipitation from 2-cell embryos identified five maternal mRNAs (Ago2, Zar1, Tle6, Floped, Tif1α) as preferential DDX1-binding targets required for embryonic development past the 1-2 cell stage.","method":"Immunofluorescence in oocytes/embryos, RNA-IP from 2-cell embryos, Ddx1 knockout mouse model, RNA dependency of localization tested by RNase treatment","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment linked to KO phenotype, RNA-IP identifies specific targets, single lab","pmids":["31330130"],"is_preprint":false},{"year":2022,"finding":"DDX1 is recruited to stress granules (SGs) in cells exposed to arsenite, hydrogen peroxide, and thapsigargin. DDX1 depletion delays resolution of arsenite-induced SGs. RNA-IP-seq identifies stress response mRNAs bound by DDX1, and the amount of these target RNAs bound to DDX1 and their overall levels increase during stress in a DDX1-dependent manner. RNA-binding is required for mRNA maintenance but not for DDX1 localization to SGs.","method":"Immunofluorescence, stress granule assays, RNA immunoprecipitation-seq (RIP-seq), DDX1 KD, RNA-binding mutant analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP-seq plus functional KD with defined mRNA stability phenotype and stress granule localization, single lab with multiple methods","pmids":["35752363"],"is_preprint":false},{"year":2022,"finding":"DDX1 forms membrane-bound calcium-containing organelles (Membrane Associated RNA-containing Vesicles, MARVs) with a nucleic acid core in early mouse embryos. Ddx1 KO disrupts calcium distribution, increases mitochondrial membrane potential, mitochondrial activity, and reactive oxygen species in embryos, indicating DDX1/MARVs regulate calcium-controlled mitochondrial function.","method":"Electron microscopy, calcium imaging, Ddx1 KO embryos, mitochondrial potential/ROS assays, RNA sequencing of embryos","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO phenotype with multiple functional readouts (calcium, mitochondrial parameters), novel organelle characterization; single lab","pmids":["35778392"],"is_preprint":false},{"year":2021,"finding":"Loss of Ddx1 in mouse embryonic stem cells causes rRNA processing defects, thereby activating the ribosome stress-p53 pathway. This was identified using a conditional knockout system with inducible gene deletion.","method":"Conditional Ddx1 knockout ESCs, rRNA processing assay, p53 pathway activation readout","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean inducible KO with defined molecular phenotype (rRNA processing + p53 activation), single lab","pmids":["33503245"],"is_preprint":false},{"year":2025,"finding":"DDX1 enzymatic (helicase) activity is specifically required for tRNA splicing in vivo but not for ER stress-induced XBP1 mRNA splicing. A helicase-inactive DDX1 mutant fails to rescue tRNA splicing defects in DDX1-deficient cells, establishing DDX1's catalytic role within the RTCB tRNA ligase complex specifically for tRNA substrates.","method":"DDX1 conditional KO in human U2OS cells (CRISPR), tRNA splicing assays, XBP1 splicing assays under ER stress, rescue with wild-type vs. helicase-dead DDX1","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — clean KO with catalytic mutant rescue dissecting substrate specificity, two independent RNA substrates tested, rigorous mechanistic design","pmids":["39833356"],"is_preprint":false},{"year":2017,"finding":"DDX1 interacts with RIF1, and DDX1 recruitment to DNA double-strand breaks (DSBs) is dependent on RIF1; RIF1 depletion abolishes DDX1-mediated facilitation of homologous recombination at DSBs. Both DDX1 and RIF1 are required for chromatin loading of BLM helicase at DSBs. RNA-DNA hybrids are required for DDX1 accumulation at DSBs, whereas single-strand RNA is required for RIF1 accumulation.","method":"Co-IP, co-localization throughout cell cycle, laser-induced DSBs, RIF1/DDX1 knockdown, HR assay, BLM chromatin loading assay, nucleic acid dependency analysis","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Co-IP, KD, HR assay, chromatin loading), single lab","pmids":["28544931"],"is_preprint":false},{"year":2018,"finding":"DDX1 binds insulin mRNA in pancreatic β cells; palmitate-induced phosphorylation of DDX1 at S295 dissociates DDX1 from insulin mRNA, suppressing insulin translation. DDX1 interacts with translation initiation factors eIF3A and eIF4B to promote translation. DDX1 knockdown eliminates palmitate-induced repression of insulin translation.","method":"RNA antisense purification coupled with MS, DDX1 KD/OE, phosphorylation site mapping (S295), co-IP with eIF3A/eIF4B, insulin translation assay","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphorylation site identified with functional consequence on translation, Co-IP of translation factors, single lab with multiple orthogonal methods","pmids":["30295850"],"is_preprint":false},{"year":2018,"finding":"DDX1 regulates alternative splicing of hundreds of target genes in pancreatic β cells (including genes associated with calcium channel function), as identified by integrated RNA-seq and CLIP-seq. Silencing DDX1 impairs calcium influx and insulin secretion.","method":"RNA-seq, CLIP-seq, DDX1 knockdown, calcium influx measurement, insulin secretion assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CLIP-seq identifies direct RNA targets, KD with defined functional phenotype (calcium/insulin), single lab","pmids":["29679569"],"is_preprint":false},{"year":2009,"finding":"DDX1 is required for transcriptional activation of the cyclin-D2, CD9, and GDF3 stem cell genes in mouse spermatogonia; a genomic DDX1-binding region (-348 to -329) in the cyclin-D2 promoter was identified by reporter and gel-shift assays. DDX1-knockdown TGCT cells cannot form solid tumors in nude mice.","method":"siRNA knockdown, reporter assay, gel-shift assay (EMSA), nude mouse tumor formation, in situ hybridization","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct DNA binding by EMSA plus reporter assay, functional in vivo tumor model, single lab","pmids":["19398953"],"is_preprint":false},{"year":2018,"finding":"DDX1 directly binds the -1837 to -1662 enhancer/promoter region of the human LGR5 gene and activates its transcription in colorectal cancer cells. DDX1 knockout (CRISPR/Cas9) reduces LGR5, CD133, ALDH1, and SOX2 expression, reduces sphere formation, and abolishes tumorigenicity in nude mice.","method":"CRISPR/Cas9 gene knockout, reporter assay, chromatin immunoprecipitation (ChIP), soft agar colony assay, nude mouse xenograft, rescue with DDX1 re-expression","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirms direct promoter binding, CRISPR KO with rescue, in vivo tumor model; single lab","pmids":["29869821"],"is_preprint":false},{"year":2013,"finding":"DDX1 regulates the subcellular localization of the ARE-binding protein KSRP; DDX1 knockdown elevates cytoplasmic KSRP, facilitates ARE-mediated mRNA decay, and increases KSRP association with 14-3-3 proteins. KSRP associates with DDX1 or 14-3-3 in a mutually exclusive manner.","method":"KSRP protein complex purification, Co-IP, DDX1 siRNA knockdown, ARE-mediated mRNA decay assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, KD with defined mRNA decay phenotype, competitive binding shown; single lab","pmids":["24023901"],"is_preprint":false},{"year":2014,"finding":"DDX1 (along with HSPC117/RTCB and FAM98B) associates with hCLE/C14orf166 in both nuclear and cytoplasmic compartments and shuttles between nucleus and cytoplasm transporting RNAs. Nuclear import of the complex requires active transcription. Silencing hCLE downregulates nuclear and cytosolic accumulation of DDX1, HSPC117, and FAM98B.","method":"Co-IP of nuclear and cytoplasmic fractions, photoactivatable GFP (PAGFP) hCLE tracking, transcription inhibition, mass spectrometry of purified complexes","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation Co-IP, live-cell shuttling assay, transcription-dependent import demonstrated; single lab","pmids":["24608264"],"is_preprint":false},{"year":2021,"finding":"Edited Azin1 protein (AZI) translocates to the nucleus and binds DDX1 with enhanced affinity, altering the chromatin distribution of DDX1 and changing expression of hematopoietic regulators to promote HSPC differentiation.","method":"RNA editing profiling (RNA-seq), Co-IP (AZI-DDX1), chromatin fractionation, functional HSPC differentiation assays","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrates interaction, chromatin fractionation shows altered DDX1 distribution, functional differentiation phenotype; single lab","pmids":["34388251"],"is_preprint":false},{"year":2024,"finding":"DDX1 physically interacts with the RNA exosome subunit EXOSC3 in neuronal cells; this interaction is decreased in the presence of DNA damage. Loss of EXOSC3 or DDX1 alters R-loop accumulation genome-wide, as shown by DRIP-seq.","method":"EXOSC3 immunoprecipitation followed by proteomics, Co-IP, DRIP-seq in N2A cells with EXOSC3 or DDX1 depletion","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus genome-wide DRIP-seq, DNA damage perturbation, single lab with two orthogonal methods","pmids":["38219817"],"is_preprint":false},{"year":2025,"finding":"EZH2 methylates DDX1 at lysine 234 (K234), promoting intervertebral disc degeneration. DDX1 K234 methylation disrupts its interaction with splicing factors and RNA targets, causing exon 14 skipping in MATR3. The truncated MATR3 disrupts nuclear architecture, increases chromatin accessibility, and activates Wnt signaling, leading to nucleus pulposus cell senescence and apoptosis.","method":"Identification by proteomics; EZH2 inhibition in vitro/in vivo; K234 methylation confirmed by mass spectrometry; RNA-seq (splicing analysis); nuclear architecture assays; ATAC-seq; lipid nanoparticle mRNA delivery rescue","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — methylation site mapped by MS, functional KO/inhibition with in vivo rescue, single lab with multiple orthogonal methods","pmids":["40610464"],"is_preprint":false},{"year":2025,"finding":"DDX1 is crotonylated at lysine 490 by GCN5 (crotonyltransferase); HDAC1 acts as the decrotonylase. K490 crotonylation enhances DDX1 interaction with HNRNPK, promoting mutually exclusive alternative splicing of ACOX1, which generates peroxisomal ROS and suppresses colorectal cancer cell proliferation.","method":"Mass spectrometry crotonylation profiling, GCN5/HDAC1 modulation, Co-IP (DDX1-HNRNPK), RNA-seq (ACOX1 splicing), ROS measurement, cell proliferation assays","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — PTM site identified by MS, writer/eraser identified, Co-IP with reader, functional splicing phenotype; single lab","pmids":["41197750"],"is_preprint":false},{"year":2023,"finding":"SARS-CoV-2 nucleocapsid protein (Np) physically interacts with DDX1 and DDX3X; Np increases DDX1 protein levels. Np binding increases the affinity of DDX1 for double-stranded RNA 2- to 4-fold in a helicase-independent manner, while Np inhibits the RNA helicase activity of DDX1.","method":"Co-IP, ATPase/helicase activity assays with recombinant proteins, dsRNA binding assays","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical assays with recombinant proteins, Co-IP; single lab, two orthogonal functional assays","pmids":["36982856"],"is_preprint":false},{"year":2026,"finding":"SARS-CoV-2 N protein interacts with DDX1 in a phosphorylation-dependent manner: GSK-3-mediated phosphorylation of the N protein SR region is required for DDX1 binding (demonstrated by GSK-3 inhibition, Ser-to-Ala mutants, and phospho-mimetic SR peptides). Phosphorylated SR peptides prevent and disrupt N-DDX1 complexes in vitro. The DDX1 N-terminal domain mediates this interaction. RNase treatment does not alter N-DDX1 interactions.","method":"Co-IP in HEK293 cells, GSK-3 inhibition, site-directed mutagenesis, alkaline phosphatase treatment, in vitro peptide competition assay, domain mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal mechanistic methods (Co-IP, mutagenesis, phospho-peptide competition in vitro), phosphorylation-dependence rigorously demonstrated; single lab","pmids":["41903808"],"is_preprint":false},{"year":2025,"finding":"USP45 deubiquitinase directly removes polyubiquitin chains from DDX1 (and RTCB), stabilizing both proteins. USP45-mediated DDX1 deubiquitination requires RTCB, but RTCB deubiquitination is DDX1-independent, revealing an asymmetric regulatory hierarchy. USP45 cooperates with DDX1 and RTCB to promote tumor proliferation and chemoresistance.","method":"Co-IP, co-localization, deubiquitination assay, substrate-specific stabilization experiments, cellular/murine tumor models","journal":"International journal of biological macromolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and direct deubiquitination assay, asymmetric dependence shown; single lab","pmids":["41468936"],"is_preprint":false},{"year":2025,"finding":"PRMT1 methylates DDX1 at arginine 602 (R602-ADMA), promoting DDX1 nuclear localization by recruiting USP10, which deubiquitinates DDX1. Methylated DDX1 in turn transcriptionally promotes PRMT1 and USP10 by binding their mRNA 3'UTRs, establishing a positive feedback loop. A PRMT1-specific inhibitor (GSK715) suppresses CCA progression in an in situ mouse model.","method":"Proteomics + ADMA modificationomics, HPLC-MS/MS (PRMT1 as methyltransferase, USP10 as deubiquitinase identification), immunofluorescence, nuclear-cytoplasmic fractionation, RNA-seq, hydrodynamic CCA mouse model","journal":"Clinical and molecular hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — PTM site mapped by MS, writer and reader/eraser identified, nuclear localization consequence shown, in vivo model; single lab","pmids":["41668296"],"is_preprint":false},{"year":2025,"finding":"TFIIH (through the CAK sub-complex) cooperates with DDX1, SFPQ, and NONO in a chromatin-bound assembly required to process R-loops formed during RNA Pol II elongation. TTD-specific variants in ERCC2/XPD destabilize TFIIH, alter the CAK–DDX1–SFPQ–NONO interaction, and cause R-loop accumulation and transcriptional stress.","method":"Mass spectrometry of chromatin-bound CAK, gene silencing (R-loop assay), immunofluorescence, TTD patient variant analysis","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-identified complex, gene silencing with R-loop phenotype, disease variants tested; single lab","pmids":["40757642"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of the human tRNA ligase complex at atomic resolution reveals that CGI-99, DDX1, and FAM98B form an alpha-helical bundle that contacts RTCB on the opposite side from the ligase active site, with DDX1 tethered to the complex via its C-terminal helix. FAM98A and FAM98C underpin compositionally distinct RTCB-containing complexes lacking Ashwin.","method":"Cryo-EM, structure-based mutagenesis, interaction analysis with mutant subunits","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 / Moderate — atomic-resolution cryo-EM structure with mutagenesis validation, single lab but rigorous structural determination","pmids":["bio_10.1101_2025.08.01.668197"],"is_preprint":true},{"year":2025,"finding":"DDX1 is required for germinal center B-cell clonal expansion and affinity maturation; DDX1-deficient B-cells upregulate c-MYC upon T-follicular helper cell contact but fail to proliferate. This proliferation block correlates with reduced mRNA translation, and DDX1 promotes protein biosynthesis through modulation of tRNA ligase complex activity and tRNA splicing.","method":"B-cell-specific Ddx1 knockout, germinal center assays, mRNA translation measurement, tRNA splicing assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — defined GC phenotype with KO and molecular mechanism (tRNA ligase/tRNA splicing) proposed, preprint not peer-reviewed, single lab","pmids":["bio_10.1101_2025.01.10.632317"],"is_preprint":true},{"year":2025,"finding":"DDX1 hydrolyzes only ATP and deoxy-ATP (not other NTPs) in the presence of RNA. ATPase activity is stimulated by single-stranded RNA ≥10 nt, blunt-ended dsRNA, RNA/DNA hybrids, and (to a lesser extent) single-stranded DNA. This defines the nucleotide and nucleic acid substrate specificity of DDX1.","method":"In vitro ATPase assays with defined nucleotide and nucleic acid substrates, systematic substrate panel","journal":"ACS omega","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic in vitro enzymatic characterization with rigorous substrate panel; single lab but comprehensive","pmids":["39895751"],"is_preprint":false},{"year":2020,"finding":"Gle1 nucleocytoplasmic shuttling regulates DDX1 nuclear localization and its interaction with CstF-64 at transcription termination sites; disruption of Gle1 shuttling increases DDX1 nucleoplasmic localization, decreases DDX1–Gle1 and DDX1–CstF-64 interactions, and increases nuclear R-loop signal.","method":"Peptide-mediated disruption of Gle1 shuttling, immunofluorescence, co-IP, R-loop staining (S9.6 antibody)","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological perturbation linked to DDX1 localization and interaction changes with defined transcription termination readout; single lab","pmids":["32755435"],"is_preprint":false}],"current_model":"DDX1 is a DEAD-box RNA helicase with ATP- and RNA-dependent ATPase activity (hydrolyzing only ATP/dATP, stimulated by ssRNA ≥10 nt, dsRNA, and RNA/DNA hybrids) that operates in multiple RNA metabolic processes: it is a structural and catalytic component of the RTCB tRNA ligase complex (where its helicase activity is specifically required for tRNA splicing but not XBP1 mRNA splicing), unwinds G-quadruplex switch transcripts to generate R-loops that promote immunoglobulin class switch recombination, recruits to DNA double-strand breaks via RIF1 to facilitate BLM loading and homologous recombination repair, senses cytosolic dsRNA as part of a DDX1–DDX21–DHX36–TRIF complex to activate type I IFN responses, promotes pri-miRNA processing via ATM-dependent phosphorylation, associates with the CstF-64 cleavage factor in nuclear cleavage bodies to facilitate pre-mRNA 3'-end processing, supports coronavirus RNA synthesis by being recruited to phosphorylated nucleocapsid complexes to enable template readthrough, and maintains cytoplasmic stress-response mRNAs during oxidative stress; its activity and localization are regulated by multiple post-translational modifications including phosphorylation (by ATM, GSK-3), ADMA methylation (by PRMT1), crotonylation (by GCN5/HDAC1), and deubiquitination (by USP45 and USP10)."},"narrative":{"mechanistic_narrative":"DDX1 is a DEAD-box ATP-dependent RNA helicase that functions across multiple RNA-metabolic processes, with an ATPase activity that hydrolyzes only ATP/dATP and is stimulated by single-stranded RNA ≥10 nt, blunt dsRNA, and RNA/DNA hybrids, exhibiting cooperative RNA/ATP binding and exceptionally tight ADP binding that arrests it in a dead-end state [PMID:39895751, PMID:25690890]. It is a structural and catalytic subunit of the human RTCB tRNA ligase complex, tethered to RTCB via its C-terminal helix within a CGI-99/DDX1/FAM98B α-helical bundle, where its helicase activity is specifically required for tRNA splicing but not for XBP1 mRNA splicing [PMID:bio_10.1101_2025.08.01.668197, PMID:39833356, PMID:24870230]. In the nucleus DDX1 resolves co-transcriptional secondary structures: it unwinds G-quadruplex switch transcripts to generate R-loops that target AID and drive immunoglobulin class switch recombination [PMID:29731414], is recruited via RIF1 to DNA double-strand breaks to load BLM and promote homologous recombination [PMID:28544931], and participates in R-loop processing at transcription termination and during RNA Pol II elongation in concert with CstF-64, Gle1, and a TFIIH-CAK–SFPQ–NONO assembly [PMID:11598190, PMID:32755435, PMID:40757642]. DDX1 also acts in pri-miRNA processing as an ATM-phosphorylated component of the Drosha/DGCR8 microprocessor [PMID:25176654], in pre-mRNA 3'-end cleavage through CstF-64 [PMID:11598190], and in alternative splicing through interaction with hnRNP K [PMID:12183465, PMID:41197750]. In the cytoplasm it senses dsRNA as part of a DDX1–DDX21–DHX36–TRIF complex to activate type I interferon responses [PMID:21703541] and is recruited to stress granules to maintain stress-response mRNAs during oxidative stress [PMID:35752363]. Multiple viruses co-opt DDX1: it is recruited to GSK-3-phosphorylated coronavirus nucleocapsid complexes to enable template readthrough during RNA synthesis [PMID:25299332, PMID:41903808] and serves as a Rev cofactor promoting HIV-1 Rev oligomerization on the RRE [PMID:21763499, PMID:22051512]. Mouse and Drosophila knockouts establish essential developmental roles, with murine Ddx1 loss causing pre-implantation embryonic lethality [PMID:25909345, PMID:31330130, PMID:26433063]. DDX1 activity and localization are tuned by phosphorylation (ATM, GSK-3), arginine methylation (PRMT1) coupled to USP10/USP45 deubiquitination, lysine methylation (EZH2), and crotonylation (GCN5/HDAC1) [PMID:25176654, PMID:41668296, PMID:41468936, PMID:40610464, PMID:41197750].","teleology":[{"year":1998,"claim":"Established that DDX1 protein partitions between nucleus and cytoplasm and that its subcellular distribution shifts with overexpression, framing localization as a regulated, dosage-sensitive property.","evidence":"Immunofluorescence and blotting across DDX1-amplified versus non-amplified neuroblastoma/retinoblastoma cell lines","pmids":["9694872"],"confidence":"Medium","gaps":["Functional consequence of cytoplasmic redistribution not directly tested","No mechanism for the localization switch identified"]},{"year":2001,"claim":"First placed DDX1 in a defined nuclear RNA-processing context by demonstrating close physical proximity to the 3'-end cleavage factor CstF-64 in cleavage bodies.","evidence":"Immunofluorescence, FRET (<10 nm), and co-immunoprecipitation","pmids":["11598190"],"confidence":"High","gaps":["Direct catalytic role in 3'-end processing not demonstrated","Whether DDX1 helicase activity acts on cleavage substrates unknown"]},{"year":2002,"claim":"Defined DDX1 as a poly(A)-binding RNA helicase whose ATPase is RNA- but not DNA-stimulated and which physically partners hnRNP K, linking it to mRNA biogenesis.","evidence":"GST pulldown, LC-MS/MS, in vitro ATPase and dsRNA unwinding assays, domain mapping","pmids":["12183465"],"confidence":"High","gaps":["Unwinding required the immunoprecipitated complex, not purified DDX1 alone","Physiological RNA substrates not defined"]},{"year":2010,"claim":"Revealed that coronaviruses recruit DDX1 via nsp14, with DDX1 relocalizing to the cytoplasm during infection to support viral replication.","evidence":"Yeast two-hybrid, reciprocal Co-IP in infected cells, domain mapping, siRNA/mutant overexpression with replication readout (IBV, SARS-CoV)","pmids":["20573827"],"confidence":"High","gaps":["Helicase activity requirement for this step not resolved","Mechanism of DDX1 relocalization during infection unknown"]},{"year":2011,"claim":"Identified a cytosolic dsRNA-sensing role: DDX1 within a DDX1–DDX21–DHX36–TRIF complex triggers type I IFN, establishing innate immune sensing as a distinct DDX1 function.","evidence":"Poly I:C-binding protein isolation, domain mapping, shRNA knockdown with IFN/cytokine readout across multiple viruses","pmids":["21703541"],"confidence":"High","gaps":["Structural basis of complex assembly not resolved","Whether helicase activity is required for sensing not tested"]},{"year":2011,"claim":"Mechanistically dissected DDX1 as an HIV-1 Rev cofactor, showing it accelerates productive Rev oligomerization on the RRE rather than acting on the RNA itself.","evidence":"Recombinant biochemistry, ATPase assays, single-molecule TIRF Rev-RRE assembly kinetics, siRNA knockdown with HIV production readout","pmids":["22051512","21763499"],"confidence":"High","gaps":["In vivo relevance of ATPase to Rev function not fully resolved","Endogenous RNA targets of this activity beyond Rev unknown"]},{"year":2014,"claim":"Defined DDX1's enzymatic role within the RTCB tRNA ligase complex, showing it facilitates formation of the RTCB-guanylate intermediate central to mammalian RNA ligation.","evidence":"Orthologous group analysis and biochemical complementation of RTCB-guanylate intermediate formation","pmids":["24870230"],"confidence":"High","gaps":["Step at which helicase activity contributes not defined here","Substrate specificity within the complex not addressed"]},{"year":2014,"claim":"Connected DDX1 to the DNA-damage response by showing ATM-phosphorylated DDX1 promotes pri-miRNA maturation within the microprocessor, with tumor-suppressive consequences.","evidence":"RNA-IP, miRNA profiling, ATM kinase assays, knockdown/overexpression, syngeneic mouse tumor model","pmids":["25176654"],"confidence":"High","gaps":["How phosphorylation alters microprocessor activity mechanistically unclear","Determinants of pri-miRNA subset selectivity unknown"]},{"year":2015,"claim":"Provided the first quantitative enzymology and atomic structural information for DDX1, defining cooperative RNA/ATP binding, dead-end ADP capture, and the SPRY domain interaction surface.","evidence":"Equilibrium and transient kinetics, nucleotide-binding assays, 2.0 Å crystal structure of the SPRY domain","pmids":["25690890","26323305"],"confidence":"High","gaps":["Nucleotide exchange factor for ADP recycling not identified","Full-length helicase structure absent"]},{"year":2015,"claim":"Established DDX1 as developmentally essential, with mouse knockout causing pre-implantation lethality and Drosophila loss causing fertility and stress-splicing defects.","evidence":"Constitutive mouse KO with embryo staging; Drosophila null with RNA-seq, Sirup mRNA binding, and genetic epistasis","pmids":["25909345","26433063"],"confidence":"Medium","gaps":["Molecular cause of 2-4 cell arrest not resolved","Transgenerational non-genetic lethality mechanism unexplained"]},{"year":2017,"claim":"Placed DDX1 in homologous recombination repair, showing RIF1-dependent recruitment to DSBs and a requirement for BLM helicase loading, with distinct nucleic-acid dependencies.","evidence":"Co-IP, laser-induced DSBs, knockdown, HR assay, BLM chromatin-loading assay, RNA-DNA hybrid dependency analysis","pmids":["28544931"],"confidence":"Medium","gaps":["Direct catalytic contribution of DDX1 helicase at DSBs not established","Single lab without reciprocal structural validation"]},{"year":2018,"claim":"Demonstrated that DDX1 unwinds G-quadruplex switch transcripts to generate R-loops that target AID, mechanistically linking DDX1 catalysis to immunoglobulin class switch recombination.","evidence":"In vivo CSR assays, chemical G4 stabilization, ATPase-dead dominant-negative mutant, R-loop immunoprecipitation","pmids":["29731414"],"confidence":"High","gaps":["Recruitment mechanism to switch regions not defined","Genome-wide breadth of G4-to-R-loop activity not mapped here"]},{"year":2018,"claim":"Identified tissue-specific RNA roles in pancreatic β cells, with DDX1 regulating insulin mRNA translation and calcium-channel alternative splicing, both tied to a phospho-switch at S295.","evidence":"RNA antisense purification-MS, CLIP-seq, RNA-seq, phospho-site mapping, eIF3A/eIF4B Co-IP, calcium influx and insulin secretion assays","pmids":["30295850","29679569"],"confidence":"Medium","gaps":["Kinase responsible for S295 phosphorylation not identified","Single-lab findings without independent replication"]},{"year":2019,"claim":"Showed DDX1 localizes to RNA-dependent cytoplasmic granules in oocytes/embryos and binds specific maternal mRNAs required for early development, connecting localization to its embryonic-essential phenotype.","evidence":"Immunofluorescence, RNase-dependency of localization, RNA-IP from 2-cell embryos, Ddx1 KO mouse","pmids":["31330130"],"confidence":"Medium","gaps":["How DDX1 maintains maternal mRNAs mechanistically unclear","Granule composition not fully defined"]},{"year":2022,"claim":"Extended DDX1's cytoplasmic RNA-protective role to stress granules and described a novel RNA-containing membrane organelle (MARV) coupling DDX1 to calcium and mitochondrial homeostasis.","evidence":"Stress granule assays with multiple stressors, RIP-seq, RNA-binding mutant analysis; EM, calcium imaging, mitochondrial/ROS assays in KO embryos","pmids":["35752363","35778392"],"confidence":"Medium","gaps":["MARV biogenesis and DDX1's enzymatic role within it unresolved","Mechanism linking DDX1 RNA binding to mRNA stabilization undefined"]},{"year":2025,"claim":"Defined substrate specificity within the RTCB complex—helicase activity is required for tRNA but not XBP1 splicing—and resolved complex architecture by cryo-EM, tethering DDX1 to RTCB via its C-terminal helix.","evidence":"Conditional KO with helicase-dead rescue and dual substrate (tRNA vs XBP1) assays; cryo-EM with structure-based mutagenesis (preprint)","pmids":["39833356","bio_10.1101_2025.08.01.668197"],"confidence":"High","gaps":["Why helicase activity is dispensable for XBP1 splicing not mechanistically explained","Cryo-EM structure is a preprint"]},{"year":2025,"claim":"Mapped a dense post-translational regulatory layer—PRMT1 arginine methylation with USP10/USP45 deubiquitination, EZH2 lysine methylation, and GCN5/HDAC1 crotonylation—that controls DDX1 localization, stability, and splicing-factor interactions in disease contexts.","evidence":"Modification proteomics/MS site mapping, writer/eraser identification, Co-IP, splicing RNA-seq/ATAC-seq, and in vivo tumor and disc-degeneration models","pmids":["41668296","41468936","40610464","41197750"],"confidence":"Medium","gaps":["Crosstalk and hierarchy among the PTMs not integrated","Each modification characterized in a single disease context only"]},{"year":null,"claim":"How DDX1's single helicase activity is partitioned and selectively deployed across its many complexes (RTCB ligation, R-loop processing, innate sensing, granule maintenance, viral RNA synthesis) remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking substrate/cofactor context to which DDX1 function is engaged","No full-length structure with bound substrate","Nucleotide exchange factor for ADP recycling unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[41,14,7,8]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[7,2,18,19]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[2,22,7]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[41,7]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[26,27]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[10,26,27]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[13,6,12,29]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,13,19,29]},{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[6,12,42]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[18,20]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[3,22,39,5,6]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[23,38,31]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,2,40]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,4,8,34,35]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[6,42,38,10]}],"complexes":["RTCB tRNA ligase complex","DDX1-DDX21-DHX36-TRIF dsRNA-sensing complex","Drosha/DGCR8 microprocessor","TFIIH-CAK–DDX1–SFPQ–NONO R-loop processing assembly"],"partners":["RTCB","FAM98B","CSTF2","HNRNPK","RIF1","EXOSC3","GLE1","USP45"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q92499","full_name":"ATP-dependent RNA helicase DDX1","aliases":["DEAD box protein 1","DEAD box protein retinoblastoma","DBP-RB"],"length_aa":740,"mass_kda":82.4,"function":"Acts as an ATP-dependent RNA helicase, able to unwind both RNA-RNA and RNA-DNA duplexes. Possesses 5' single-stranded RNA overhang nuclease activity. Possesses ATPase activity on various RNA, but not DNA polynucleotides. May play a role in RNA clearance at DNA double-strand breaks (DSBs), thereby facilitating the template-guided repair of transcriptionally active regions of the genome. Together with RELA, acts as a coactivator to enhance NF-kappa-B-mediated transcriptional activation. Acts as a positive transcriptional regulator of cyclin CCND2 expression. Binds to the cyclin CCND2 promoter region. Associates with chromatin at the NF-kappa-B promoter region via association with RELA. Binds to poly(A) RNA. May be involved in 3'-end cleavage and polyadenylation of pre-mRNAs. It is also an accessory subunit of the tRNA-splicing ligase complex that acts by directly joining spliced tRNA halves to mature-sized tRNAs by incorporating the precursor-derived splice junction phosphate into the mature tRNA as a canonical 3',5'-phosphodiester. Cooperates with ZBTB8OS (also known as archease) for the guanylylation of RTCB, a key intermediate step in activation of the tRNA ligase (PubMed:24870230). Component of a multi-helicase-TICAM1 complex that acts as a cytoplasmic sensor of viral double-stranded RNA (dsRNA) and plays a role in the activation of a cascade of antiviral responses including the induction of pro-inflammatory cytokines via the adapter molecule TICAM1. Specifically binds (via helicase ATP-binding domain) on both short and long poly(I:C) dsRNA (By similarity) (Microbial infection) Required for HIV-1 Rev function as well as for HIV-1 and coronavirus IBV replication. Binds to the RRE sequence of HIV-1 mRNAs (Microbial infection) Required for Coronavirus IBV replication","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q92499/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DDX1","classification":"Not Classified","n_dependent_lines":447,"n_total_lines":1208,"dependency_fraction":0.37003311258278143},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RTCB","stoichiometry":10.0},{"gene":"BYSL","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"CLNS1A","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"RPS16","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/DDX1","total_profiled":1310},"omim":[{"mim_id":"620904","title":"FAMILY WITH SEQUENCE SIMILARITY 98, MEMBER A; FAM98A","url":"https://www.omim.org/entry/620904"},{"mim_id":"619149","title":"LESSEL-KREIENKAMP SYNDROME; LESKRES","url":"https://www.omim.org/entry/619149"},{"mim_id":"616142","title":"FAMILY WITH SEQUENCE SIMILARITY 98, MEMBER B; FAM98B","url":"https://www.omim.org/entry/616142"},{"mim_id":"615891","title":"ZINC FINGER- AND BTB DOMAIN-CONTAINING PROTEIN 8, OPPOSITE STRAND; ZBTB8OS","url":"https://www.omim.org/entry/615891"},{"mim_id":"613901","title":"RNA 2-PRIME,3-PRIME CYCLIC PHOSPHATE AND 5-PRIME-OH LIGASE; RTCB","url":"https://www.omim.org/entry/613901"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/DDX1"},"hgnc":{"alias_symbol":["DBP-RB"],"prev_symbol":[]},"alphafold":{"accession":"Q92499","domains":[{"cath_id":"3.40.50.300","chopping":"1-82_284-434","consensus_level":"medium","plddt":85.4763,"start":1,"end":434},{"cath_id":"2.60.120.920","chopping":"85-267","consensus_level":"high","plddt":91.8754,"start":85,"end":267},{"cath_id":"3.40.50.300","chopping":"440-684","consensus_level":"high","plddt":90.4282,"start":440,"end":684},{"cath_id":"1.20.5","chopping":"700-731","consensus_level":"medium","plddt":77.2109,"start":700,"end":731}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92499","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92499-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92499-F1-predicted_aligned_error_v6.png","plddt_mean":86.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DDX1","jax_strain_url":"https://www.jax.org/strain/search?query=DDX1"},"sequence":{"accession":"Q92499","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92499.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92499/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92499"}},"corpus_meta":[{"pmid":"21703541","id":"PMC_21703541","title":"DDX1, 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Knockdown of DDX1 blocked type I IFN and cytokine responses to poly I:C, influenza A virus, and reovirus.\",\n      \"method\": \"Isolation/sequencing of poly I:C-binding proteins, shRNA knockdown, domain mapping, cytosolic localization confirmed independently of endosomes\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, domain mapping, functional knockdown with defined IFN phenotype, replicated across multiple viral stimuli\",\n      \"pmids\": [\"21703541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Phosphorylation of the coronavirus nucleocapsid (N) protein by GSK-3 recruits RNA helicase DDX1 to the N-containing complex, facilitating template readthrough during transcription and enabling synthesis of longer subgenomic mRNAs and full-length genomic RNA. DDX1 knockdown or loss of helicase activity markedly reduces longer sgmRNA levels.\",\n      \"method\": \"GSK-3 inhibition, DDX1 knockdown, helicase-dead mutant expression, quantitative RT-PCR for sgmRNA species\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (pharmacological inhibition, KD, dominant-negative mutant) with defined molecular phenotype\",\n      \"pmids\": [\"25299332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DDX1 binds G-quadruplex (G4) structures in intronic switch transcripts at the IgH locus and converts them into R-loops, thereby targeting AID to S-regions to promote class switch recombination (CSR). An ATPase-deficient DDX1 mutant acts as dominant-negative, reducing R-loop levels over S-regions and CSR efficiency.\",\n      \"method\": \"In vivo CSR assays, chemical G4 stabilization, ATPase-deficient dominant-negative mutant, R-loop immunoprecipitation\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal approaches (chemical perturbation, catalytic mutant, in vivo CSR), rigorous mechanistic dissection\",\n      \"pmids\": [\"29731414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"DDX1 is a component of the human tRNA splicing ligase complex (tRNA-LC); together with archease, DDX1 facilitates formation of the RTCB-guanylate intermediate central to mammalian RNA ligation, defining DDX1's enzymatic role within this complex.\",\n      \"method\": \"Eukaryotic orthologous group analysis, biochemical complementation assay for RTCB-guanylate intermediate formation\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution of intermediate formation, single lab but rigorous enzymatic assay\",\n      \"pmids\": [\"24870230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"DDX1 interacts with coronavirus (IBV and SARS-CoV) nonstructural protein 14 (nsp14); the interaction maps to the C-terminal region of DDX1 (motifs V and VI) and the N-terminal portion of nsp14. DDX1 is relocalized from nucleus to cytoplasm upon IBV infection, and either siRNA knockdown or overexpression of a DDX1 mutant reduced IBV replication.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, siRNA knockdown, subcellular fractionation/immunofluorescence, viral replication assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP confirmed in infected cells, domain mapping, functional KD with replication phenotype, two coronavirus orthologs tested\",\n      \"pmids\": [\"20573827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"DDX1 promotes maturation of a subset of primary miRNAs (including miR-200 family members) by functioning as a regulatory component of the Drosha/DGCR8 microprocessor. ATM-mediated phosphorylation of DDX1 facilitates this induction after DNA damage. DDX1 inhibition promotes ovarian tumor growth and metastasis in a syngeneic mouse model.\",\n      \"method\": \"RNA-IP, miRNA profiling, ATM kinase assays, DDX1 knockdown/overexpression, syngeneic mouse tumor model\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (RNA-IP, kinase assay, in vivo mouse model), ATM identified as upstream kinase\",\n      \"pmids\": [\"25176654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"DDX1 colocalizes with cleavage stimulation factor CstF-64 in nuclear cleavage bodies and resides within 10 nm of CstF-64 (demonstrated by FRET). Co-immunoprecipitation shows DDX1 is in the same complex as CstF-64, implicating DDX1 in 3'-end cleavage and polyadenylation of pre-mRNAs.\",\n      \"method\": \"Immunofluorescence, fluorescence resonance energy transfer (FRET), co-immunoprecipitation\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — FRET (< 10 nm proximity) plus Co-IP, two independent methods establishing physical association\",\n      \"pmids\": [\"11598190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"DDX1 physically interacts with hnRNP K via the N-terminal 1–276 amino acids of hnRNP K; this interaction is disrupted by poly(A), poly(C), and poly(U) RNA substrates. DDX1 is a homopolymeric poly(A) RNA-binding protein whose ATPase activity is stimulated by homopolymeric RNAs and total yeast RNA but not by DNA. The immunoprecipitated DDX1 complex (but not purified DDX1 alone) unwinds dsRNA with single-stranded poly(A) overhangs.\",\n      \"method\": \"GST affinity chromatography, LC-MS/MS, in vitro binding assay, co-immunoprecipitation, ATPase assay, RNA unwinding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ATPase and unwinding assays plus domain mapping and Co-IP, multiple orthogonal methods\",\n      \"pmids\": [\"12183465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DDX1 is an RNA-activated ATPase that binds HIV-1 Rev in an RNA-independent manner and forms complexes with Rev-bound RNA. DDX1 is required for both Rev activity and HIV-1 production from infected cells (demonstrated by RNA silencing). Rev-bound RNA is equally effective as protein-free RNA at stimulating DDX1 ATPase activity.\",\n      \"method\": \"Recombinant protein biochemistry, gel-filtration, CD spectroscopy, fluorescent Rev binding assay, cell-based Co-IP, ATPase assay, gel mobility shift, siRNA knockdown, HIV production assay\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro ATPase reconstitution, direct binding assay, cell-based functional knockdown, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"22051512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DDX1 promotes oligomerization of HIV-1 Rev on the Rev response element (RRE) by eliminating nonproductive nucleation events and accelerating early Rev monomer binding steps, without altering dissociation rates. This effect is enhanced by non-hydrolyzable ATP (AMP-PNP) but not ADP. DDX1 targets Rev rather than the RRE and can rescue oligomerization of a Rev mutant that cannot assemble beyond a monomer.\",\n      \"method\": \"Single-molecule total internal reflection fluorescence microscopy (TIRF), fluorescently labeled Rev, real-time Rev-RRE assembly/dissociation kinetics\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule reconstitution with kinetic dissection, mechanistically rigorous, single lab\",\n      \"pmids\": [\"21763499\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DDX1 interacts with NF-κB subunit RelA (p65) and acts as a co-activator to enhance NF-κB-mediated transcription. The interaction maps to the C-terminal transactivation domain of RelA and the N-terminal ATPase/helicase domain of DDX1. A DDX1 dominant-negative mutant lacking ATPase/helicase activity loses transcriptional co-activator function.\",\n      \"method\": \"Mammalian two-hybrid, co-immunoprecipitation, confocal microscopy, chromatin immunoprecipitation, NF-κB reporter gene assay, siRNA knockdown, domain mapping\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (two-hybrid, Co-IP, ChIP, reporter assay) in a single lab study\",\n      \"pmids\": [\"19058135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"DDX1 functions as a cellular co-factor for HIV-1 Rev in the nucleus/nucleolus; low endogenous DDX1 in human astrocytes shifts Rev localization from nuclear/nucleolar to cytoplasmic dominance. Exogenous DDX1 expression in astrocytes restores nuclear Rev localization and increases HIV-1 viral production.\",\n      \"method\": \"HIV-1 pseudotyped infection, semi-quantitative RT-PCR for spliced/unspliced RNA, DDX1 overexpression, Rev immunofluorescence localization\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional rescue experiment with Rev localization readout plus viral RNA quantification, single lab\",\n      \"pmids\": [\"15892970\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"DDX1 bodies, cleavage bodies, Cajal bodies, and gems are distinct nuclear suborganelles whose associations are cell-cycle-regulated; CstF-64-containing cleavage bodies are primarily found during S phase and are sensitive to DNA replication inhibitors; all four bodies associate during S phase with cleavage bodies colocalizing with DDX1 bodies. Latrunculin B (actin polymerization inhibitor) causes formation of nuclear spicules containing CstF-64, CPSF-100, RNA, and RNA Pol II.\",\n      \"method\": \"Immunofluorescence throughout cell cycle, inhibitors of transcription/DNA replication/actin polymerization, live-cell imaging\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic cell-cycle imaging with pharmacological perturbations, single lab, localization tied to functional context\",\n      \"pmids\": [\"16371507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"DDX1 protein is found in both nucleus and cytoplasm of DDX1-amplified neuroblastoma and retinoblastoma cell lines, but is localized primarily to the nucleus of non-amplified cells, establishing overexpression-dependent cytoplasmic redistribution.\",\n      \"method\": \"Immunofluorescence with polyclonal anti-DDX1 antibodies, Western blot, Northern blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization by immunofluorescence across multiple cell lines; functional consequence inferred but not directly tested\",\n      \"pmids\": [\"9694872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Biochemical characterization of DDX1 shows exceptionally tight ADP binding (three orders of magnitude tighter than ATP), arresting the enzyme in a potential ADP dead-end conformation, suggesting DDX1 requires a nucleotide exchange factor for recycling. Strong cooperativity in RNA and ATP binding to DDX1 was observed, where either ligand alone partially shifts the enzyme from 'open' to 'closed' state.\",\n      \"method\": \"Equilibrium titrations, transient kinetics, nucleotide binding assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinetic reconstitution with multiple binding assays, rigorous quantitative characterization, single lab\",\n      \"pmids\": [\"25690890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of the SPRY domain of human DDX1 (hDSPRY) resolved at 2.0 Å reveals two layers of concave antiparallel β-sheets and a conserved patch of positive surface charge proposed as a protein–protein interaction surface, providing the first structural information on any DDX1 domain.\",\n      \"method\": \"X-ray crystallography at 2.0 Å resolution\",\n      \"journal\": \"Acta crystallographica. Section F, Structural biology communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure at atomic resolution; functional validation of interaction surface is partial (structural inference), single lab\",\n      \"pmids\": [\"26323305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Drosophila Ddx1 null flies are viable but reduced in size, with females showing reduced fertility due to egg chamber autophagy and males being sterile due to disrupted spermatogenesis. Ddx1 directly binds Sirup mRNA and regulates its differential splicing; double mutant (Ddx1 null + Sirup RNAi) causes epistatic lethality not seen in single mutants, suggesting Ddx1 acts in a stress-induced splicing pathway involving Sirup.\",\n      \"method\": \"Drosophila null mutation, comparative RNA-seq, RNA binding assay (Sirup mRNA), genetic epistasis with dsRNA knockdown\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with null allele and defined splicing target, multiple phenotypic readouts, ortholog of human DDX1\",\n      \"pmids\": [\"26433063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Homozygous Ddx1 knockout in mice causes embryonic lethality prior to E3.5, with embryos stalling at the 2-4 cell stage. Heterozygote crosses reveal a transgenerational wild-type lethality phenotype transmitted through Ddx1*(/-) parents independently of sex, via a non-genetic mechanism.\",\n      \"method\": \"Constitutive Ddx1 knockout mouse generation, embryo staging, genotyping of progeny from heterozygote crosses\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined embryonic lethal phenotype in KO mice with stage-specific stalling; transgenerational mechanism not molecularly resolved\",\n      \"pmids\": [\"25909345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DDX1 protein localizes exclusively to cytoplasmic granules in oocytes and early mouse embryos, requiring RNA for retention at these sites. Homozygous Ddx1 KO causes stalling at 2-4 cell stages. DDX1 RNA-immunoprecipitation from 2-cell embryos identified five maternal mRNAs (Ago2, Zar1, Tle6, Floped, Tif1α) as preferential DDX1-binding targets required for embryonic development past the 1-2 cell stage.\",\n      \"method\": \"Immunofluorescence in oocytes/embryos, RNA-IP from 2-cell embryos, Ddx1 knockout mouse model, RNA dependency of localization tested by RNase treatment\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment linked to KO phenotype, RNA-IP identifies specific targets, single lab\",\n      \"pmids\": [\"31330130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DDX1 is recruited to stress granules (SGs) in cells exposed to arsenite, hydrogen peroxide, and thapsigargin. DDX1 depletion delays resolution of arsenite-induced SGs. RNA-IP-seq identifies stress response mRNAs bound by DDX1, and the amount of these target RNAs bound to DDX1 and their overall levels increase during stress in a DDX1-dependent manner. RNA-binding is required for mRNA maintenance but not for DDX1 localization to SGs.\",\n      \"method\": \"Immunofluorescence, stress granule assays, RNA immunoprecipitation-seq (RIP-seq), DDX1 KD, RNA-binding mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP-seq plus functional KD with defined mRNA stability phenotype and stress granule localization, single lab with multiple methods\",\n      \"pmids\": [\"35752363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DDX1 forms membrane-bound calcium-containing organelles (Membrane Associated RNA-containing Vesicles, MARVs) with a nucleic acid core in early mouse embryos. Ddx1 KO disrupts calcium distribution, increases mitochondrial membrane potential, mitochondrial activity, and reactive oxygen species in embryos, indicating DDX1/MARVs regulate calcium-controlled mitochondrial function.\",\n      \"method\": \"Electron microscopy, calcium imaging, Ddx1 KO embryos, mitochondrial potential/ROS assays, RNA sequencing of embryos\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO phenotype with multiple functional readouts (calcium, mitochondrial parameters), novel organelle characterization; single lab\",\n      \"pmids\": [\"35778392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Loss of Ddx1 in mouse embryonic stem cells causes rRNA processing defects, thereby activating the ribosome stress-p53 pathway. This was identified using a conditional knockout system with inducible gene deletion.\",\n      \"method\": \"Conditional Ddx1 knockout ESCs, rRNA processing assay, p53 pathway activation readout\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean inducible KO with defined molecular phenotype (rRNA processing + p53 activation), single lab\",\n      \"pmids\": [\"33503245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DDX1 enzymatic (helicase) activity is specifically required for tRNA splicing in vivo but not for ER stress-induced XBP1 mRNA splicing. A helicase-inactive DDX1 mutant fails to rescue tRNA splicing defects in DDX1-deficient cells, establishing DDX1's catalytic role within the RTCB tRNA ligase complex specifically for tRNA substrates.\",\n      \"method\": \"DDX1 conditional KO in human U2OS cells (CRISPR), tRNA splicing assays, XBP1 splicing assays under ER stress, rescue with wild-type vs. helicase-dead DDX1\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — clean KO with catalytic mutant rescue dissecting substrate specificity, two independent RNA substrates tested, rigorous mechanistic design\",\n      \"pmids\": [\"39833356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"DDX1 interacts with RIF1, and DDX1 recruitment to DNA double-strand breaks (DSBs) is dependent on RIF1; RIF1 depletion abolishes DDX1-mediated facilitation of homologous recombination at DSBs. Both DDX1 and RIF1 are required for chromatin loading of BLM helicase at DSBs. RNA-DNA hybrids are required for DDX1 accumulation at DSBs, whereas single-strand RNA is required for RIF1 accumulation.\",\n      \"method\": \"Co-IP, co-localization throughout cell cycle, laser-induced DSBs, RIF1/DDX1 knockdown, HR assay, BLM chromatin loading assay, nucleic acid dependency analysis\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Co-IP, KD, HR assay, chromatin loading), single lab\",\n      \"pmids\": [\"28544931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DDX1 binds insulin mRNA in pancreatic β cells; palmitate-induced phosphorylation of DDX1 at S295 dissociates DDX1 from insulin mRNA, suppressing insulin translation. DDX1 interacts with translation initiation factors eIF3A and eIF4B to promote translation. DDX1 knockdown eliminates palmitate-induced repression of insulin translation.\",\n      \"method\": \"RNA antisense purification coupled with MS, DDX1 KD/OE, phosphorylation site mapping (S295), co-IP with eIF3A/eIF4B, insulin translation assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphorylation site identified with functional consequence on translation, Co-IP of translation factors, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"30295850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DDX1 regulates alternative splicing of hundreds of target genes in pancreatic β cells (including genes associated with calcium channel function), as identified by integrated RNA-seq and CLIP-seq. Silencing DDX1 impairs calcium influx and insulin secretion.\",\n      \"method\": \"RNA-seq, CLIP-seq, DDX1 knockdown, calcium influx measurement, insulin secretion assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CLIP-seq identifies direct RNA targets, KD with defined functional phenotype (calcium/insulin), single lab\",\n      \"pmids\": [\"29679569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DDX1 is required for transcriptional activation of the cyclin-D2, CD9, and GDF3 stem cell genes in mouse spermatogonia; a genomic DDX1-binding region (-348 to -329) in the cyclin-D2 promoter was identified by reporter and gel-shift assays. DDX1-knockdown TGCT cells cannot form solid tumors in nude mice.\",\n      \"method\": \"siRNA knockdown, reporter assay, gel-shift assay (EMSA), nude mouse tumor formation, in situ hybridization\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct DNA binding by EMSA plus reporter assay, functional in vivo tumor model, single lab\",\n      \"pmids\": [\"19398953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DDX1 directly binds the -1837 to -1662 enhancer/promoter region of the human LGR5 gene and activates its transcription in colorectal cancer cells. DDX1 knockout (CRISPR/Cas9) reduces LGR5, CD133, ALDH1, and SOX2 expression, reduces sphere formation, and abolishes tumorigenicity in nude mice.\",\n      \"method\": \"CRISPR/Cas9 gene knockout, reporter assay, chromatin immunoprecipitation (ChIP), soft agar colony assay, nude mouse xenograft, rescue with DDX1 re-expression\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirms direct promoter binding, CRISPR KO with rescue, in vivo tumor model; single lab\",\n      \"pmids\": [\"29869821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"DDX1 regulates the subcellular localization of the ARE-binding protein KSRP; DDX1 knockdown elevates cytoplasmic KSRP, facilitates ARE-mediated mRNA decay, and increases KSRP association with 14-3-3 proteins. KSRP associates with DDX1 or 14-3-3 in a mutually exclusive manner.\",\n      \"method\": \"KSRP protein complex purification, Co-IP, DDX1 siRNA knockdown, ARE-mediated mRNA decay assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, KD with defined mRNA decay phenotype, competitive binding shown; single lab\",\n      \"pmids\": [\"24023901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"DDX1 (along with HSPC117/RTCB and FAM98B) associates with hCLE/C14orf166 in both nuclear and cytoplasmic compartments and shuttles between nucleus and cytoplasm transporting RNAs. Nuclear import of the complex requires active transcription. Silencing hCLE downregulates nuclear and cytosolic accumulation of DDX1, HSPC117, and FAM98B.\",\n      \"method\": \"Co-IP of nuclear and cytoplasmic fractions, photoactivatable GFP (PAGFP) hCLE tracking, transcription inhibition, mass spectrometry of purified complexes\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation Co-IP, live-cell shuttling assay, transcription-dependent import demonstrated; single lab\",\n      \"pmids\": [\"24608264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Edited Azin1 protein (AZI) translocates to the nucleus and binds DDX1 with enhanced affinity, altering the chromatin distribution of DDX1 and changing expression of hematopoietic regulators to promote HSPC differentiation.\",\n      \"method\": \"RNA editing profiling (RNA-seq), Co-IP (AZI-DDX1), chromatin fractionation, functional HSPC differentiation assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrates interaction, chromatin fractionation shows altered DDX1 distribution, functional differentiation phenotype; single lab\",\n      \"pmids\": [\"34388251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DDX1 physically interacts with the RNA exosome subunit EXOSC3 in neuronal cells; this interaction is decreased in the presence of DNA damage. Loss of EXOSC3 or DDX1 alters R-loop accumulation genome-wide, as shown by DRIP-seq.\",\n      \"method\": \"EXOSC3 immunoprecipitation followed by proteomics, Co-IP, DRIP-seq in N2A cells with EXOSC3 or DDX1 depletion\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus genome-wide DRIP-seq, DNA damage perturbation, single lab with two orthogonal methods\",\n      \"pmids\": [\"38219817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"EZH2 methylates DDX1 at lysine 234 (K234), promoting intervertebral disc degeneration. DDX1 K234 methylation disrupts its interaction with splicing factors and RNA targets, causing exon 14 skipping in MATR3. The truncated MATR3 disrupts nuclear architecture, increases chromatin accessibility, and activates Wnt signaling, leading to nucleus pulposus cell senescence and apoptosis.\",\n      \"method\": \"Identification by proteomics; EZH2 inhibition in vitro/in vivo; K234 methylation confirmed by mass spectrometry; RNA-seq (splicing analysis); nuclear architecture assays; ATAC-seq; lipid nanoparticle mRNA delivery rescue\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — methylation site mapped by MS, functional KO/inhibition with in vivo rescue, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"40610464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DDX1 is crotonylated at lysine 490 by GCN5 (crotonyltransferase); HDAC1 acts as the decrotonylase. K490 crotonylation enhances DDX1 interaction with HNRNPK, promoting mutually exclusive alternative splicing of ACOX1, which generates peroxisomal ROS and suppresses colorectal cancer cell proliferation.\",\n      \"method\": \"Mass spectrometry crotonylation profiling, GCN5/HDAC1 modulation, Co-IP (DDX1-HNRNPK), RNA-seq (ACOX1 splicing), ROS measurement, cell proliferation assays\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — PTM site identified by MS, writer/eraser identified, Co-IP with reader, functional splicing phenotype; single lab\",\n      \"pmids\": [\"41197750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SARS-CoV-2 nucleocapsid protein (Np) physically interacts with DDX1 and DDX3X; Np increases DDX1 protein levels. Np binding increases the affinity of DDX1 for double-stranded RNA 2- to 4-fold in a helicase-independent manner, while Np inhibits the RNA helicase activity of DDX1.\",\n      \"method\": \"Co-IP, ATPase/helicase activity assays with recombinant proteins, dsRNA binding assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical assays with recombinant proteins, Co-IP; single lab, two orthogonal functional assays\",\n      \"pmids\": [\"36982856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"SARS-CoV-2 N protein interacts with DDX1 in a phosphorylation-dependent manner: GSK-3-mediated phosphorylation of the N protein SR region is required for DDX1 binding (demonstrated by GSK-3 inhibition, Ser-to-Ala mutants, and phospho-mimetic SR peptides). Phosphorylated SR peptides prevent and disrupt N-DDX1 complexes in vitro. The DDX1 N-terminal domain mediates this interaction. RNase treatment does not alter N-DDX1 interactions.\",\n      \"method\": \"Co-IP in HEK293 cells, GSK-3 inhibition, site-directed mutagenesis, alkaline phosphatase treatment, in vitro peptide competition assay, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal mechanistic methods (Co-IP, mutagenesis, phospho-peptide competition in vitro), phosphorylation-dependence rigorously demonstrated; single lab\",\n      \"pmids\": [\"41903808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"USP45 deubiquitinase directly removes polyubiquitin chains from DDX1 (and RTCB), stabilizing both proteins. USP45-mediated DDX1 deubiquitination requires RTCB, but RTCB deubiquitination is DDX1-independent, revealing an asymmetric regulatory hierarchy. USP45 cooperates with DDX1 and RTCB to promote tumor proliferation and chemoresistance.\",\n      \"method\": \"Co-IP, co-localization, deubiquitination assay, substrate-specific stabilization experiments, cellular/murine tumor models\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and direct deubiquitination assay, asymmetric dependence shown; single lab\",\n      \"pmids\": [\"41468936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRMT1 methylates DDX1 at arginine 602 (R602-ADMA), promoting DDX1 nuclear localization by recruiting USP10, which deubiquitinates DDX1. Methylated DDX1 in turn transcriptionally promotes PRMT1 and USP10 by binding their mRNA 3'UTRs, establishing a positive feedback loop. A PRMT1-specific inhibitor (GSK715) suppresses CCA progression in an in situ mouse model.\",\n      \"method\": \"Proteomics + ADMA modificationomics, HPLC-MS/MS (PRMT1 as methyltransferase, USP10 as deubiquitinase identification), immunofluorescence, nuclear-cytoplasmic fractionation, RNA-seq, hydrodynamic CCA mouse model\",\n      \"journal\": \"Clinical and molecular hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — PTM site mapped by MS, writer and reader/eraser identified, nuclear localization consequence shown, in vivo model; single lab\",\n      \"pmids\": [\"41668296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TFIIH (through the CAK sub-complex) cooperates with DDX1, SFPQ, and NONO in a chromatin-bound assembly required to process R-loops formed during RNA Pol II elongation. TTD-specific variants in ERCC2/XPD destabilize TFIIH, alter the CAK–DDX1–SFPQ–NONO interaction, and cause R-loop accumulation and transcriptional stress.\",\n      \"method\": \"Mass spectrometry of chromatin-bound CAK, gene silencing (R-loop assay), immunofluorescence, TTD patient variant analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-identified complex, gene silencing with R-loop phenotype, disease variants tested; single lab\",\n      \"pmids\": [\"40757642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of the human tRNA ligase complex at atomic resolution reveals that CGI-99, DDX1, and FAM98B form an alpha-helical bundle that contacts RTCB on the opposite side from the ligase active site, with DDX1 tethered to the complex via its C-terminal helix. FAM98A and FAM98C underpin compositionally distinct RTCB-containing complexes lacking Ashwin.\",\n      \"method\": \"Cryo-EM, structure-based mutagenesis, interaction analysis with mutant subunits\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — atomic-resolution cryo-EM structure with mutagenesis validation, single lab but rigorous structural determination\",\n      \"pmids\": [\"bio_10.1101_2025.08.01.668197\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DDX1 is required for germinal center B-cell clonal expansion and affinity maturation; DDX1-deficient B-cells upregulate c-MYC upon T-follicular helper cell contact but fail to proliferate. This proliferation block correlates with reduced mRNA translation, and DDX1 promotes protein biosynthesis through modulation of tRNA ligase complex activity and tRNA splicing.\",\n      \"method\": \"B-cell-specific Ddx1 knockout, germinal center assays, mRNA translation measurement, tRNA splicing assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — defined GC phenotype with KO and molecular mechanism (tRNA ligase/tRNA splicing) proposed, preprint not peer-reviewed, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.01.10.632317\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DDX1 hydrolyzes only ATP and deoxy-ATP (not other NTPs) in the presence of RNA. ATPase activity is stimulated by single-stranded RNA ≥10 nt, blunt-ended dsRNA, RNA/DNA hybrids, and (to a lesser extent) single-stranded DNA. This defines the nucleotide and nucleic acid substrate specificity of DDX1.\",\n      \"method\": \"In vitro ATPase assays with defined nucleotide and nucleic acid substrates, systematic substrate panel\",\n      \"journal\": \"ACS omega\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic in vitro enzymatic characterization with rigorous substrate panel; single lab but comprehensive\",\n      \"pmids\": [\"39895751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Gle1 nucleocytoplasmic shuttling regulates DDX1 nuclear localization and its interaction with CstF-64 at transcription termination sites; disruption of Gle1 shuttling increases DDX1 nucleoplasmic localization, decreases DDX1–Gle1 and DDX1–CstF-64 interactions, and increases nuclear R-loop signal.\",\n      \"method\": \"Peptide-mediated disruption of Gle1 shuttling, immunofluorescence, co-IP, R-loop staining (S9.6 antibody)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological perturbation linked to DDX1 localization and interaction changes with defined transcription termination readout; single lab\",\n      \"pmids\": [\"32755435\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DDX1 is a DEAD-box RNA helicase with ATP- and RNA-dependent ATPase activity (hydrolyzing only ATP/dATP, stimulated by ssRNA ≥10 nt, dsRNA, and RNA/DNA hybrids) that operates in multiple RNA metabolic processes: it is a structural and catalytic component of the RTCB tRNA ligase complex (where its helicase activity is specifically required for tRNA splicing but not XBP1 mRNA splicing), unwinds G-quadruplex switch transcripts to generate R-loops that promote immunoglobulin class switch recombination, recruits to DNA double-strand breaks via RIF1 to facilitate BLM loading and homologous recombination repair, senses cytosolic dsRNA as part of a DDX1–DDX21–DHX36–TRIF complex to activate type I IFN responses, promotes pri-miRNA processing via ATM-dependent phosphorylation, associates with the CstF-64 cleavage factor in nuclear cleavage bodies to facilitate pre-mRNA 3'-end processing, supports coronavirus RNA synthesis by being recruited to phosphorylated nucleocapsid complexes to enable template readthrough, and maintains cytoplasmic stress-response mRNAs during oxidative stress; its activity and localization are regulated by multiple post-translational modifications including phosphorylation (by ATM, GSK-3), ADMA methylation (by PRMT1), crotonylation (by GCN5/HDAC1), and deubiquitination (by USP45 and USP10).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DDX1 is a DEAD-box ATP-dependent RNA helicase that functions across multiple RNA-metabolic processes, with an ATPase activity that hydrolyzes only ATP/dATP and is stimulated by single-stranded RNA ≥10 nt, blunt dsRNA, and RNA/DNA hybrids, exhibiting cooperative RNA/ATP binding and exceptionally tight ADP binding that arrests it in a dead-end state [#41, #14]. It is a structural and catalytic subunit of the human RTCB tRNA ligase complex, tethered to RTCB via its C-terminal helix within a CGI-99/DDX1/FAM98B α-helical bundle, where its helicase activity is specifically required for tRNA splicing but not for XBP1 mRNA splicing [#39, #22, #3]. In the nucleus DDX1 resolves co-transcriptional secondary structures: it unwinds G-quadruplex switch transcripts to generate R-loops that target AID and drive immunoglobulin class switch recombination [#2], is recruited via RIF1 to DNA double-strand breaks to load BLM and promote homologous recombination [#23], and participates in R-loop processing at transcription termination and during RNA Pol II elongation in concert with CstF-64, Gle1, and a TFIIH-CAK–SFPQ–NONO assembly [#6, #42, #38]. DDX1 also acts in pri-miRNA processing as an ATM-phosphorylated component of the Drosha/DGCR8 microprocessor [#5], in pre-mRNA 3'-end cleavage through CstF-64 [#6], and in alternative splicing through interaction with hnRNP K [#7, #33]. In the cytoplasm it senses dsRNA as part of a DDX1–DDX21–DHX36–TRIF complex to activate type I interferon responses [#0] and is recruited to stress granules to maintain stress-response mRNAs during oxidative stress [#19]. Multiple viruses co-opt DDX1: it is recruited to GSK-3-phosphorylated coronavirus nucleocapsid complexes to enable template readthrough during RNA synthesis [#1, #35] and serves as a Rev cofactor promoting HIV-1 Rev oligomerization on the RRE [#9, #8]. Mouse and Drosophila knockouts establish essential developmental roles, with murine Ddx1 loss causing pre-implantation embryonic lethality [#17, #18, #16]. DDX1 activity and localization are tuned by phosphorylation (ATM, GSK-3), arginine methylation (PRMT1) coupled to USP10/USP45 deubiquitination, lysine methylation (EZH2), and crotonylation (GCN5/HDAC1) [#5, #37, #36, #32, #33].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that DDX1 protein partitions between nucleus and cytoplasm and that its subcellular distribution shifts with overexpression, framing localization as a regulated, dosage-sensitive property.\",\n      \"evidence\": \"Immunofluorescence and blotting across DDX1-amplified versus non-amplified neuroblastoma/retinoblastoma cell lines\",\n      \"pmids\": [\"9694872\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of cytoplasmic redistribution not directly tested\", \"No mechanism for the localization switch identified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"First placed DDX1 in a defined nuclear RNA-processing context by demonstrating close physical proximity to the 3'-end cleavage factor CstF-64 in cleavage bodies.\",\n      \"evidence\": \"Immunofluorescence, FRET (<10 nm), and co-immunoprecipitation\",\n      \"pmids\": [\"11598190\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct catalytic role in 3'-end processing not demonstrated\", \"Whether DDX1 helicase activity acts on cleavage substrates unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined DDX1 as a poly(A)-binding RNA helicase whose ATPase is RNA- but not DNA-stimulated and which physically partners hnRNP K, linking it to mRNA biogenesis.\",\n      \"evidence\": \"GST pulldown, LC-MS/MS, in vitro ATPase and dsRNA unwinding assays, domain mapping\",\n      \"pmids\": [\"12183465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Unwinding required the immunoprecipitated complex, not purified DDX1 alone\", \"Physiological RNA substrates not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Revealed that coronaviruses recruit DDX1 via nsp14, with DDX1 relocalizing to the cytoplasm during infection to support viral replication.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal Co-IP in infected cells, domain mapping, siRNA/mutant overexpression with replication readout (IBV, SARS-CoV)\",\n      \"pmids\": [\"20573827\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Helicase activity requirement for this step not resolved\", \"Mechanism of DDX1 relocalization during infection unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified a cytosolic dsRNA-sensing role: DDX1 within a DDX1–DDX21–DHX36–TRIF complex triggers type I IFN, establishing innate immune sensing as a distinct DDX1 function.\",\n      \"evidence\": \"Poly I:C-binding protein isolation, domain mapping, shRNA knockdown with IFN/cytokine readout across multiple viruses\",\n      \"pmids\": [\"21703541\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of complex assembly not resolved\", \"Whether helicase activity is required for sensing not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Mechanistically dissected DDX1 as an HIV-1 Rev cofactor, showing it accelerates productive Rev oligomerization on the RRE rather than acting on the RNA itself.\",\n      \"evidence\": \"Recombinant biochemistry, ATPase assays, single-molecule TIRF Rev-RRE assembly kinetics, siRNA knockdown with HIV production readout\",\n      \"pmids\": [\"22051512\", \"21763499\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of ATPase to Rev function not fully resolved\", \"Endogenous RNA targets of this activity beyond Rev unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined DDX1's enzymatic role within the RTCB tRNA ligase complex, showing it facilitates formation of the RTCB-guanylate intermediate central to mammalian RNA ligation.\",\n      \"evidence\": \"Orthologous group analysis and biochemical complementation of RTCB-guanylate intermediate formation\",\n      \"pmids\": [\"24870230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Step at which helicase activity contributes not defined here\", \"Substrate specificity within the complex not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected DDX1 to the DNA-damage response by showing ATM-phosphorylated DDX1 promotes pri-miRNA maturation within the microprocessor, with tumor-suppressive consequences.\",\n      \"evidence\": \"RNA-IP, miRNA profiling, ATM kinase assays, knockdown/overexpression, syngeneic mouse tumor model\",\n      \"pmids\": [\"25176654\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How phosphorylation alters microprocessor activity mechanistically unclear\", \"Determinants of pri-miRNA subset selectivity unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided the first quantitative enzymology and atomic structural information for DDX1, defining cooperative RNA/ATP binding, dead-end ADP capture, and the SPRY domain interaction surface.\",\n      \"evidence\": \"Equilibrium and transient kinetics, nucleotide-binding assays, 2.0 Å crystal structure of the SPRY domain\",\n      \"pmids\": [\"25690890\", \"26323305\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nucleotide exchange factor for ADP recycling not identified\", \"Full-length helicase structure absent\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Established DDX1 as developmentally essential, with mouse knockout causing pre-implantation lethality and Drosophila loss causing fertility and stress-splicing defects.\",\n      \"evidence\": \"Constitutive mouse KO with embryo staging; Drosophila null with RNA-seq, Sirup mRNA binding, and genetic epistasis\",\n      \"pmids\": [\"25909345\", \"26433063\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular cause of 2-4 cell arrest not resolved\", \"Transgenerational non-genetic lethality mechanism unexplained\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed DDX1 in homologous recombination repair, showing RIF1-dependent recruitment to DSBs and a requirement for BLM helicase loading, with distinct nucleic-acid dependencies.\",\n      \"evidence\": \"Co-IP, laser-induced DSBs, knockdown, HR assay, BLM chromatin-loading assay, RNA-DNA hybrid dependency analysis\",\n      \"pmids\": [\"28544931\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct catalytic contribution of DDX1 helicase at DSBs not established\", \"Single lab without reciprocal structural validation\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that DDX1 unwinds G-quadruplex switch transcripts to generate R-loops that target AID, mechanistically linking DDX1 catalysis to immunoglobulin class switch recombination.\",\n      \"evidence\": \"In vivo CSR assays, chemical G4 stabilization, ATPase-dead dominant-negative mutant, R-loop immunoprecipitation\",\n      \"pmids\": [\"29731414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recruitment mechanism to switch regions not defined\", \"Genome-wide breadth of G4-to-R-loop activity not mapped here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified tissue-specific RNA roles in pancreatic β cells, with DDX1 regulating insulin mRNA translation and calcium-channel alternative splicing, both tied to a phospho-switch at S295.\",\n      \"evidence\": \"RNA antisense purification-MS, CLIP-seq, RNA-seq, phospho-site mapping, eIF3A/eIF4B Co-IP, calcium influx and insulin secretion assays\",\n      \"pmids\": [\"30295850\", \"29679569\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase responsible for S295 phosphorylation not identified\", \"Single-lab findings without independent replication\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed DDX1 localizes to RNA-dependent cytoplasmic granules in oocytes/embryos and binds specific maternal mRNAs required for early development, connecting localization to its embryonic-essential phenotype.\",\n      \"evidence\": \"Immunofluorescence, RNase-dependency of localization, RNA-IP from 2-cell embryos, Ddx1 KO mouse\",\n      \"pmids\": [\"31330130\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How DDX1 maintains maternal mRNAs mechanistically unclear\", \"Granule composition not fully defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended DDX1's cytoplasmic RNA-protective role to stress granules and described a novel RNA-containing membrane organelle (MARV) coupling DDX1 to calcium and mitochondrial homeostasis.\",\n      \"evidence\": \"Stress granule assays with multiple stressors, RIP-seq, RNA-binding mutant analysis; EM, calcium imaging, mitochondrial/ROS assays in KO embryos\",\n      \"pmids\": [\"35752363\", \"35778392\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MARV biogenesis and DDX1's enzymatic role within it unresolved\", \"Mechanism linking DDX1 RNA binding to mRNA stabilization undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined substrate specificity within the RTCB complex—helicase activity is required for tRNA but not XBP1 splicing—and resolved complex architecture by cryo-EM, tethering DDX1 to RTCB via its C-terminal helix.\",\n      \"evidence\": \"Conditional KO with helicase-dead rescue and dual substrate (tRNA vs XBP1) assays; cryo-EM with structure-based mutagenesis (preprint)\",\n      \"pmids\": [\"39833356\", \"bio_10.1101_2025.08.01.668197\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why helicase activity is dispensable for XBP1 splicing not mechanistically explained\", \"Cryo-EM structure is a preprint\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mapped a dense post-translational regulatory layer—PRMT1 arginine methylation with USP10/USP45 deubiquitination, EZH2 lysine methylation, and GCN5/HDAC1 crotonylation—that controls DDX1 localization, stability, and splicing-factor interactions in disease contexts.\",\n      \"evidence\": \"Modification proteomics/MS site mapping, writer/eraser identification, Co-IP, splicing RNA-seq/ATAC-seq, and in vivo tumor and disc-degeneration models\",\n      \"pmids\": [\"41668296\", \"41468936\", \"40610464\", \"41197750\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Crosstalk and hierarchy among the PTMs not integrated\", \"Each modification characterized in a single disease context only\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How DDX1's single helicase activity is partitioned and selectively deployed across its many complexes (RTCB ligation, R-loop processing, innate sensing, granule maintenance, viral RNA synthesis) remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking substrate/cofactor context to which DDX1 function is engaged\", \"No full-length structure with bound substrate\", \"Nucleotide exchange factor for ADP recycling unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [41, 14, 7, 8]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [7, 2, 18, 19]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [2, 22, 7]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [41, 7]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [26, 27]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [10, 26, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [13, 6, 12, 29]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 13, 19, 29]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [6, 12, 42]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [18, 20]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [3, 22, 39, 5, 6]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [23, 38, 31]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 2, 40]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 4, 8, 34, 35]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [6, 42, 38, 10]}\n    ],\n    \"complexes\": [\n      \"RTCB tRNA ligase complex\",\n      \"DDX1-DDX21-DHX36-TRIF dsRNA-sensing complex\",\n      \"Drosha/DGCR8 microprocessor\",\n      \"TFIIH-CAK–DDX1–SFPQ–NONO R-loop processing assembly\"\n    ],\n    \"partners\": [\n      \"RTCB\",\n      \"FAM98B\",\n      \"CSTF2\",\n      \"HNRNPK\",\n      \"RIF1\",\n      \"EXOSC3\",\n      \"GLE1\",\n      \"USP45\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}