{"gene":"AICDA","run_date":"2026-06-09T22:02:42","timeline":{"discoveries":[{"year":2000,"finding":"AID is required for both class switch recombination (CSR) and somatic hypermutation (SHM) in B cells; AID-/- mice show complete defects in both processes, and overexpression of AID in CH12F3-2 cells augments class switching without cytokine stimulation.","method":"Knockout mouse model, transgenic overexpression, in vitro B cell stimulation assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function KO with defined cellular phenotype replicated in two independent papers (PMID:11007474, PMID:11007475)","pmids":["11007474","11007475"],"is_preprint":false},{"year":2000,"finding":"Mutations in the human AICDA gene cause autosomal recessive hyper-IgM syndrome type 2 (HIGM2), characterized by absence of CSR, lack of somatic hypermutation, and lymph node hyperplasia with giant germinal centers.","method":"Genetic sequencing of HIGM2 patients, phenotypic characterization","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetic loss-of-function with defined immunological phenotype, replicated in patient cohort","pmids":["11007475"],"is_preprint":false},{"year":2002,"finding":"AID functions by deaminating dC residues in DNA (not RNA); expression of AID in E. coli produces a mutator phenotype with C/G transitions that is enhanced by UNG deficiency, demonstrating a DNA deamination mechanism.","method":"E. coli mutator assay, UNG-deficient bacteria, context-dependent mutation analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro/bacterial reconstitution with genetic epistasis (UNG deficiency), foundational mechanistic paper","pmids":["12097915"],"is_preprint":false},{"year":2002,"finding":"AID is required for immunoglobulin gene conversion in chicken DT40 B cells; disruption of AID completely blocks Ig gene conversion, and reintroduction of AID cDNA rescues this block.","method":"Gene disruption in DT40 cells, complementation with AID cDNA","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype and genetic rescue in avian model system","pmids":["11847344"],"is_preprint":false},{"year":2002,"finding":"Ectopic expression of AID alone is sufficient to induce somatic hypermutation in an actively transcribed GFP reporter in NIH 3T3 fibroblasts; mutation frequency correlates with transcription level.","method":"Ectopic AID expression in fibroblasts, GFP reporter mutation assay, transcription-level correlation","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — gain-of-function in non-B cells with quantitative mutation readout, single lab but orthogonal controls","pmids":["12065838"],"is_preprint":false},{"year":2003,"finding":"AID deaminates cytidines specifically on single-stranded DNA (ssDNA) but not double-stranded DNA (dsDNA) in vitro; dsDNA can be deaminated when the reaction is coupled to transcription, which generates ssDNA secondary structures, and this transcriptional orientation-dependence matches in vivo CSR requirements.","method":"In vitro cytidine deaminase assay on ssDNA and dsDNA substrates, transcription-coupled deamination assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay with defined substrates, transcription coupling demonstrated, functional correlation with in vivo CSR","pmids":["12692563"],"is_preprint":false},{"year":2003,"finding":"Purified AID catalyzes processive C-to-U deamination on ssDNA preferentially at 5' WRC hotspot sequences; AID introduces multiple deaminations per DNA strand (10–70 per clone) rather than distributively; AID shows 15-fold preference for the non-transcribed strand exposed by RNA polymerase.","method":"In vitro deamination assay with purified AID on ssDNA, mutation spectrum analysis, transcribed dsDNA substrate assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — purified enzyme in vitro assay with quantitative processivity analysis and hotspot characterization","pmids":["12819663"],"is_preprint":false},{"year":2003,"finding":"Constitutive ubiquitous expression of AID in transgenic mice causes T cell lymphomas and epithelial micro-adenomas; point mutations are massively introduced in TCR and c-myc genes, demonstrating AID can mutate non-Ig oncogenes.","method":"AID transgenic mouse model, tumor sequencing, mutation analysis of TCR and c-myc genes","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic model with defined tumor phenotype and molecular mutation characterization","pmids":["12732658"],"is_preprint":false},{"year":2005,"finding":"AID is phosphorylated on Ser38 by protein kinase A (PKA) in B cells; phosphorylation enables AID to associate with replication protein A (RPA) and promotes deamination of transcribed dsDNA; mutation of the PKA site preserves ssDNA deamination but markedly reduces RPA-dependent dsDNA deamination and severely impairs CSR in vivo.","method":"Biochemical phosphorylation assay with recombinant PKA, AID-RPA co-immunoprecipitation, site-directed mutagenesis, in vivo CSR assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of phosphorylation and protein interaction, mutagenesis, and in vivo functional validation","pmids":["16251902"],"is_preprint":false},{"year":2005,"finding":"DNA double-strand breaks (DSBs) in Ig switch regions during CSR are AID-dependent and UNG-dependent, occur preferentially at WRC/GYW AID hotspot motifs, and AID attacks cytosines on both DNA strands.","method":"Ligation-mediated PCR detection of DSBs in splenic B cells, AID-/- and UNG-/- genetic ablation","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct detection of DSBs with genetic epistasis using two independent KO mouse lines","pmids":["16103411"],"is_preprint":false},{"year":2005,"finding":"5-methylcytosine (methylated CpG) is protected from AID-mediated deamination in vitro; unmethylated cytidines adjacent to CpGs are not protected, indicating methylation does not provide broader protection.","method":"In vitro deamination assay on methylated and unmethylated plasmid substrates with purified AID","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro assay, single lab, single method","pmids":["15607819"],"is_preprint":false},{"year":2007,"finding":"AID deficiency prevents Bcl6-dependent germinal center-derived B cell lymphoma in mouse models, but has no impact on pre-GC Myc-driven lymphomas, demonstrating AID is required specifically for GC-derived lymphomagenesis through CSR/SHM-mediated genetic alterations.","method":"Genetic cross of AID-/- mice with Bcl6-, Myc-, and Myc/Bcl6-transgenic lymphoma models","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in multiple mouse lymphoma models with defined molecular pathway","pmids":["18066064"],"is_preprint":false},{"year":2007,"finding":"AID is required for c-myc to IgH variable-region (V-JH) chromosomal translocations in IL-6 transgenic mice; these translocations are absent in AID-/- IL-6 transgenic mice.","method":"Genetic cross of AID-/- mice with IL-6 transgenic model, translocation detection by PCR","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic ablation with specific molecular translocation readout","pmids":["17724134"],"is_preprint":false},{"year":2008,"finding":"AID is phosphorylated at both Ser38 and Thr140; mutation of either site does not affect catalytic activity but impairs CSR and somatic hypermutation in vivo, with T140 phosphorylation preferentially affecting somatic mutation.","method":"Mass spectrometry identification of phosphorylation sites, alanine substitution mutagenesis, in vivo CSR and SHM assays in haploinsufficient mice","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mass spectrometry identification plus mutagenesis and in vivo functional assays, single lab with orthogonal methods","pmids":["18838546"],"is_preprint":false},{"year":2008,"finding":"BCR engagement inhibits AID gene expression through Ca2+/calmodulin-dependent inhibition of the E2A transcription factor; calmodulin overexpression inhibits AID expression, and calmodulin-binding-site-mutated E2A renders AID expression resistant to BCR-mediated inhibition.","method":"BCR stimulation assays, calmodulin overexpression, E2A mutagenesis, AID expression analysis","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional genetic experiments with mutagenesis, single lab","pmids":["18203819"],"is_preprint":false},{"year":2009,"finding":"The estrogen-estrogen receptor complex binds directly to the AID promoter, enhancing AID mRNA and protein expression, leading to increases in SHM and CSR at the Ig locus, and enhanced c-myc translocations.","method":"Promoter binding assay (ChIP/reporter), AID mRNA/protein expression analysis, functional CSR and SHM assays, translocation analysis","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct promoter binding demonstrated, functional consequences in multiple orthogonal assays, single lab","pmids":["19139166"],"is_preprint":false},{"year":2009,"finding":"B cell-specific and stimulation-responsive enhancer elements in the Aicda first intron overcome silencer elements to derepress AID expression; the intron contains binding sites for ubiquitous silencers c-Myb and E2f and B cell-specific activators Pax5 and E-box-binding proteins.","method":"Reporter assay, phylogenetic footprinting, histone acetylation mapping, mutagenesis of regulatory elements in CH12F3-2 cells","journal":"Nature immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional regulatory element mapping with mutagenesis, single lab, multiple methods","pmids":["19966806"],"is_preprint":false},{"year":2010,"finding":"AID (AICDA) is required for active DNA demethylation at OCT4 and NANOG promoters during reprogramming toward pluripotency; AID protein binds methylated silent promoters in fibroblasts but not active demethylated promoters in ES cells; siRNA knockdown of AID prevents promoter demethylation and induction of OCT4 and NANOG.","method":"siRNA knockdown in human-mouse heterokaryons, promoter methylation analysis, AID protein binding assay, gene expression analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined molecular phenotype (DNA demethylation), protein binding assay, single lab with multiple orthogonal methods","pmids":["20027182"],"is_preprint":false},{"year":2010,"finding":"Uracil residues generated by AID deamination are physically present in immunoglobulin variable and switch region DNA of stimulated B cells; they are present on both strands, replace mainly cytosine, appear within 24 hours of stimulation, and are AID-dependent.","method":"Uracil-DNA glycosylase sensitivity assay, abasic endonuclease assay, multiple detection methods in AID-/- and wild-type B cells","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct physical detection of AID-generated uracil in DNA with multiple orthogonal methods and genetic controls","pmids":["21151102"],"is_preprint":false},{"year":2011,"finding":"A knock-in AID(G23S) mutation selectively impairs somatic hypermutation while preserving normal immunoglobulin levels; AID(G23S) mice develop germinal center hyperplasia and defective mucosal defense, demonstrating SHM has a distinct function from CSR in intestinal homeostasis.","method":"Knock-in point mutation mouse model, Ig quantification, germinal center analysis, bacterial challenge assays","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — precise knock-in mutation separating SHM from CSR functions with in vivo phenotypic readouts","pmids":["21258321"],"is_preprint":false},{"year":2014,"finding":"RNA exosome regulation of noncoding RNA (xTSS-RNAs) recruits AID to single-stranded DNA-forming sites of antisense and divergent transcription; Exosc3-deficient B cells have impaired CSR and SHM; divergently transcribed ncRNA-associated genomic loci accumulate AID-mediated mutations and translocations.","method":"Conditional Exosc3 KO mouse model, transcriptome analysis, AID recruitment assay, ChIP, SSB structure analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with defined molecular phenotype, AID recruitment demonstrated, multiple orthogonal genomic methods","pmids":["25119026"],"is_preprint":false},{"year":2015,"finding":"Intronic switch RNA (generated after lariat debranching) acts in trans to target AID to switch region DNA via G-quadruplex structures formed by the RNA; AID binds directly to switch RNA; mutation of a key residue in AID's putative RNA-binding domain impairs AID recruitment to S regions and abolishes CSR; inhibition of RNA lariat processing similarly disrupts AID localization and CSR.","method":"RNA-AID binding assay, G-quadruplex biochemical analysis, AID mutagenesis, RNA lariat processing inhibition, AID ChIP, CSR functional assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct RNA-protein binding, mutagenesis, and in vivo functional rescue experiments in single rigorous study","pmids":["25957684"],"is_preprint":false},{"year":2015,"finding":"AID undergoes nuclear degradation more slowly in G1 phase than in S or G2-M phase; enforced nuclear localization of AID in G1 accelerates SHM and CSR and is well-tolerated, while nuclear AID in S-G2/M phase compromises cell viability; regulatory phosphorylation and catalytic activity mutations alter AID nuclear stability.","method":"High content screening microscopy, cell cycle-specific degradation tag fusions, CSR and SHM functional assays, AID stability measurements","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cell-cycle-regulated localization with functional consequences, single lab with multiple methods","pmids":["26355458"],"is_preprint":false},{"year":2015,"finding":"AID binds to transcribed dsDNA and translocates unidirectionally in concert with RNA polymerase on moving transcription bubbles, while increasing the fraction of stalled bubbles; when constrained in a model bubble, AID scans randomly; on unconstrained ssDNA, AID moves bidirectionally in short slides/hops.","method":"Single-molecule FRET analysis of AID on transcribed dsDNA and ssDNA substrates","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-molecule FRET providing direct mechanistic resolution of AID movement, single lab","pmids":["26681117"],"is_preprint":false},{"year":2016,"finding":"The AID C terminus is required for stable dimer formation; AID monomers associate with DNA cleavage cofactor hnRNP K, whereas AID dimers associate with recombination cofactors hnRNP L, hnRNP U, and Serpine mRNA-binding protein 1; all AID/ribonucleoprotein associations are RNA-dependent.","method":"Bimolecular fluorescence complementation (BiFC), glycerol gradient fractionation, co-immunoprecipitation","journal":"Proceedings of the National Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — BiFC and fractionation with co-IP, single lab, multiple methods","pmids":["26929374"],"is_preprint":false},{"year":2017,"finding":"Crystal structures of human AID (MBP-fused) alone and in complex with deoxycytidine monophosphate reveal a bifurcated substrate-binding surface that captures two adjacent single-stranded overhangs simultaneously; G-quadruplex substrates mimicking Ig switch regions are preferred AID substrates; G4 substrates induce cooperative AID oligomerization; structure-based mutations disrupting bifurcated substrate recognition or oligomerization both compromise CSR in splenic B cells.","method":"X-ray crystallography, in vitro deamination assays, site-directed mutagenesis, in vivo CSR assay in splenic B cells","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and in vivo CSR, multiple orthogonal methods in single study","pmids":["28757211"],"is_preprint":false},{"year":2018,"finding":"EGFR T790M resistance mutation is acquired through AICDA-mediated deamination of 5-methylcytosine at position c.2369; EGFR TKI treatment activates NFκB which induces AICDA expression; pharmacologic inhibition of NFκB or AICDA knockout prevents T790M mutation development.","method":"AICDA knockout, NFκB inhibition, 5-methylcytosine deamination assay, mutation frequency analysis in lung cancer cells","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO and pharmacological inhibition with specific mutation readout, single lab, multiple methods","pmids":["30333118"],"is_preprint":false},{"year":2019,"finding":"TET2 and TET3 enhance AID (Aicda) expression in B cells by depositing 5-hydroxymethylcytosine (5hmC) and maintaining chromatin accessibility at two superenhancer elements (TetE1, TetE2) in the Aicda locus; BATF facilitates TET recruitment to TetE1; TET-dependent Aicda expression regulates CSR.","method":"Conditional Tet2/Tet3 KO in B cells, 5hmC mapping (ChIP-seq), ATAC-seq, BATF-deficient B cells, Aicda expression and CSR assays","journal":"Science immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with epigenomic mapping and functional CSR readout, multiple orthogonal methods","pmids":["31028100"],"is_preprint":false},{"year":2004,"finding":"AID protein is predominantly localized in the cytoplasm of normal germinal center centroblasts and malignant B cells (Burkitt lymphoma), as detected using specific antibodies; cytoplasmic localization suggests additional regulatory mechanisms for its nuclear function.","method":"Immunohistochemistry and immunofluorescence with specific anti-AID antibodies in normal and neoplastic B cells","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct protein localization by IHC/IF in multiple cell types, single lab, replicated in subsequent paper (PMID:16439679)","pmids":["15304391"],"is_preprint":false},{"year":2006,"finding":"Nuclear AID is detected in ~2.5% of germinal center cells specifically in the dark zone and outer zone (but not light zone); AID is relocalized to the nucleus in cycling CDKN1B-/CCNB1- GC blasts and in extrafollicular large B cells (14% with nuclear AID); nuclear/cytoplasmic distribution is consistent with the topography of SHM and CSR.","method":"Immunohistochemistry, immunofluorescence, co-staining with cell cycle markers in human tonsil GC sections","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct subcellular localization tied to functional context (SHM/CSR zones), single lab","pmids":["16439679"],"is_preprint":false},{"year":2012,"finding":"APOBEC3B nuclear import requires an N-terminal motif analogous to AID's nuclear localization determinant, and A3B interacts with the same subset of importin proteins as AID, suggesting mechanistic conservation of nuclear import between AID and A3B.","method":"Mutagenesis of nuclear localization determinant, importin co-immunoprecipitation, nuclear localization assays","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis and co-IP for importin interaction, single lab","pmids":["22446380"],"is_preprint":false},{"year":2015,"finding":"Chronic Plasmodium infection prolongs germinal center expansion and AID expression, leading to widespread DNA damage in GC B cells and chromosome translocations; AID-dependent mature B cell lymphomas with translocations are favored by malaria infection.","method":"Mouse Plasmodium chabaudi chronic infection model, GC analysis, DNA damage assays, AID-/- genetic ablation, lymphoma characterization","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic ablation (AID-/-) with molecular translocation readout in defined in vivo infectious model","pmids":["26276629"],"is_preprint":false},{"year":2018,"finding":"AICDA overexpression drives increased cytosine methylation heterogeneity in BCL2-driven murine lymphomas without increasing somatic mutation burden; AICDA depletion in normal GC B cells reduces cytosine methylation heterogeneity, identifying AICDA as a driver of epigenetic heterogeneity.","method":"AICDA transgenic overexpression and shRNA depletion in mouse lymphoma models, whole-genome bisulfite sequencing for methylation heterogeneity analysis","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with genome-wide epigenetic readout, single lab","pmids":["29335468"],"is_preprint":false},{"year":2022,"finding":"SETD2 haploinsufficiency enhances AICDA-induced somatic hypermutation selectively on the nontemplate DNA strand; H3K36me3 loss (from SETD2 deficiency) is associated with greater RNA polymerase II processivity and increased mutational burden; SETD2-mediated H3K36me3 is required for proper sensing of AID-induced cytosine deamination.","method":"Heterozygous Setd2 KO mouse model, ChIP-seq for H3K36me3, RNAPII ChIP-seq, whole genome sequencing for mutation analysis, AICDA-dependent SHM strand analysis","journal":"Cancer discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic model with chromatin and mutational genomic analysis, single lab with multiple orthogonal methods","pmids":["35443279"],"is_preprint":false}],"current_model":"AICDA (AID) is a B cell-specific ssDNA cytidine deaminase that converts cytosine to uracil at WRC hotspot motifs on single-stranded DNA exposed during transcription; it requires PKA-mediated phosphorylation at Ser38 (enabling RPA association for dsDNA access) and Thr140, forms dimers via its C-terminus to interact with hnRNP cofactors, is targeted to Ig switch regions through G-quadruplex-containing switch RNA and RNA exosome-regulated antisense noncoding RNA, acts processively while tracking with RNA polymerase II on transcription bubbles, and initiates both somatic hypermutation and class switch recombination—as well as active DNA demethylation at developmental loci—while its expression is tightly regulated at the transcriptional level (by NF-κB, Pax5, E2A, BATF/TET-mediated superenhancer activity, and BCR-calmodulin signaling) and post-translationally through nuclear-cytoplasmic shuttling that is cell-cycle regulated."},"narrative":{"mechanistic_narrative":"AICDA (AID) is a B cell single-stranded DNA cytidine deaminase that initiates antibody diversification, serving as the obligate trigger for both class switch recombination (CSR) and somatic hypermutation (SHM) — processes that are completely abolished in its absence and underlie autosomal recessive hyper-IgM syndrome type 2 in humans [PMID:11007474, PMID:11007475]. Mechanistically, AID converts deoxycytidine to deoxyuridine in DNA, not RNA, producing a mutator phenotype that is amplified by loss of uracil excision; this generates uracil lesions physically detectable on both strands of Ig variable and switch DNA, whose processing yields the AID-dependent, UNG-dependent double-strand breaks at WRC/GYW hotspots that drive recombination [PMID:12097915, PMID:16103411, PMID:21151102]. Catalysis is restricted to single-stranded DNA and is coupled to transcription, which exposes ssDNA; the enzyme acts processively, tracking unidirectionally with RNA polymerase on transcription bubbles and preferentially deaminating the exposed non-transcribed strand at 5'-WRC motifs [PMID:12692563, PMID:12819663, PMID:26681117]. Crystallographic analysis reveals a bifurcated substrate-binding surface that engages two adjacent ssDNA overhangs and favors G-quadruplex substrates mimicking switch regions, with G4-induced cooperative oligomerization required for CSR [PMID:28757211]. Substrate access to double-stranded DNA additionally requires PKA phosphorylation at Ser38, which enables RPA association, and phosphorylation at Thr140 contributes preferentially to SHM, allowing the two arms of antibody diversification to be genetically separated [PMID:16251902, PMID:18838546, PMID:21258321]. AID is targeted to its genomic substrates by noncoding RNA: intronic switch RNA acting in trans via G-quadruplex structures, and RNA-exosome-regulated antisense/divergent transcripts that mark ssDNA-forming loci [PMID:25119026, PMID:25957684]. Because AID is a promiscuous mutagen, its activity is constrained by transcriptional control (Pax5/E-box activators, c-Myb/E2f silencers in the first intron, BCR-calmodulin inhibition of E2A, estrogen-receptor and NF-κB induction, and BATF/TET-dependent superenhancer activity) and by cell-cycle-regulated nuclear-cytoplasmic shuttling that limits genotoxic nuclear exposure to G1 [PMID:18203819, PMID:19139166, PMID:19966806, PMID:26355458, PMID:31028100, PMID:16439679]. Beyond immunity, AID mediates active DNA demethylation at OCT4 and NANOG during reprogramming and shapes epigenetic methylation heterogeneity in lymphomas [PMID:20027182, PMID:29335468]. Its off-target activity causes c-myc/IgH translocations and germinal-center-derived lymphomas, and deamination of 5-methylcytosine can generate oncogenic mutations such as EGFR T790M [PMID:12732658, PMID:18066064, PMID:17724134, PMID:30333118, PMID:26276629].","teleology":[{"year":2000,"claim":"Establishing that a single factor controls antibody diversification, AID was shown to be required for both CSR and SHM and causally linked to a human immunodeficiency, defining the gene's central physiological role.","evidence":"AID-/- mouse knockout with CSR/SHM defects, transgenic overexpression in CH12F3-2 cells, and genetic sequencing of HIGM2 patients","pmids":["11007474","11007475"],"confidence":"High","gaps":["Did not define the biochemical substrate (DNA vs RNA)","Did not establish enzymatic mechanism or targeting"]},{"year":2002,"claim":"Resolving the long-debated substrate question, AID was shown to act as a DNA cytidine deaminase rather than an RNA-editing enzyme, and to be sufficient to drive hypermutation of a transcribed reporter in non-lymphoid cells.","evidence":"E. coli mutator assay with UNG-deficiency epistasis, Ig gene conversion rescue in DT40 cells, and ectopic AID expression with a GFP reporter in fibroblasts","pmids":["12097915","11847344","12065838"],"confidence":"High","gaps":["Did not show strand or sequence preference of purified enzyme","Did not address how transcription exposes substrate in vivo"]},{"year":2003,"claim":"Defining the enzyme's intrinsic biochemistry, purified AID was shown to deaminate ssDNA processively at WRC hotspots and to access dsDNA only when coupled to transcription, explaining its transcription dependence in vivo.","evidence":"In vitro deamination assays on ssDNA/dsDNA, transcription-coupled deamination, mutation spectrum and processivity analysis with purified AID","pmids":["12692563","12819663"],"confidence":"High","gaps":["Did not explain genomic targeting specificity to Ig loci","Did not identify cofactors or post-translational regulation"]},{"year":2005,"claim":"Connecting signaling to enzymatic access, PKA phosphorylation at Ser38 was shown to enable RPA association and dsDNA deamination, providing a regulatable switch for CSR distinct from intrinsic ssDNA catalysis.","evidence":"Recombinant PKA phosphorylation assay, AID-RPA co-IP, site-directed mutagenesis, and in vivo CSR assays; complemented by LM-PCR detection of AID/UNG-dependent switch-region DSBs","pmids":["16251902","16103411","15607819"],"confidence":"High","gaps":["Did not map all phosphosites or their division of labor between CSR and SHM","Did not resolve how phosphorylation is spatially restricted"]},{"year":2008,"claim":"Refining the regulatory code, a second phosphosite (Thr140) was identified that preferentially supports SHM, and BCR-calmodulin-E2A signaling was shown to repress AID transcription, revealing layered control of a dangerous mutator.","evidence":"Mass spectrometry phosphosite mapping with alanine-substitution mice, plus BCR stimulation, calmodulin overexpression, and E2A mutagenesis","pmids":["18838546","18203819"],"confidence":"Medium","gaps":["Did not establish kinase identity for T140","Mechanistic separation of CSR vs SHM functions remained partial"]},{"year":2010,"claim":"Extending function beyond immunity, AID was shown to be required for active DNA demethylation at pluripotency promoters during reprogramming, and AID-generated uracil was directly detected in Ig DNA, confirming the deamination-then-repair model in vivo.","evidence":"siRNA knockdown in heterokaryons with promoter methylation/binding analysis, and direct uracil detection by UDG/abasic-endonuclease assays in stimulated B cells","pmids":["20027182","21151102"],"confidence":"High","gaps":["Direct demethylation mechanism (5mC deamination vs indirect) not fully resolved","Did not define how AID is targeted to non-Ig developmental loci"]},{"year":2015,"claim":"Solving the genomic targeting problem, noncoding RNAs were shown to recruit AID to ssDNA-forming sites — intronic switch RNA via G-quadruplexes in trans, and RNA-exosome-regulated antisense/divergent transcripts — while single-molecule and cell-cycle studies defined how AID moves with RNAPII and is spatially restricted.","evidence":"RNA-AID binding and G4 biochemistry with mutagenesis and CSR rescue; conditional Exosc3 KO with AID recruitment/ChIP; smFRET of AID on transcription bubbles; cell-cycle degradation-tag and localization studies","pmids":["25957684","25119026","26681117","26355458"],"confidence":"High","gaps":["RNA-binding interface on AID not fully mapped structurally","How ncRNA and phosphorylation cues are integrated remains unresolved"]},{"year":2016,"claim":"Linking oligomeric state to cofactor selection, the AID C-terminus was shown to control dimerization, with monomers and dimers engaging distinct hnRNP cofactors in an RNA-dependent manner, partitioning DNA cleavage from recombination functions.","evidence":"BiFC, glycerol gradient fractionation, and co-immunoprecipitation","pmids":["26929374"],"confidence":"Medium","gaps":["Co-IP without reciprocal/structural validation of individual hnRNP contacts","Functional consequences of each cofactor association not dissected in vivo"]},{"year":2017,"claim":"Providing atomic-resolution mechanism, crystal structures revealed a bifurcated substrate-binding surface capturing two adjacent ssDNA overhangs and a preference for G-quadruplex switch substrates that drives cooperative oligomerization required for CSR.","evidence":"X-ray crystallography of MBP-AID alone and with dCMP, in vitro deamination, structure-guided mutagenesis, and in vivo splenic-B-cell CSR assays","pmids":["28757211"],"confidence":"High","gaps":["No structure of full-length AID bound to physiological RNA/DNA complexes","Structural basis of phosphoregulation and RPA contact not resolved"]},{"year":2022,"claim":"Connecting chromatin state to mutational targeting, SETD2/H3K36me3 was shown to constrain AID-induced SHM on the nontemplate strand, demonstrating that chromatin modifications tune the genomic consequences of AID activity, alongside roles in oncogenic mutation and translocation.","evidence":"Heterozygous Setd2 KO mice with H3K36me3 and RNAPII ChIP-seq, whole-genome mutation analysis; complemented by lymphoma models linking AID to c-myc/IgH translocations, GC-derived lymphomagenesis, methylation heterogeneity, and EGFR T790M","pmids":["35443279","18066064","17724134","12732658","29335468","30333118","26276629","19139166","19966806","31028100"],"confidence":"Medium","gaps":["How chromatin marks are mechanistically read by the AID/repair machinery is unclear","Determinants of on- vs off-target genomic specificity remain incompletely defined"]},{"year":null,"claim":"It remains unresolved how the structural, phosphoregulatory, ncRNA-targeting, cofactor, and chromatin inputs are integrated into a single coherent rule that directs AID to physiological Ig loci while limiting genome-wide off-target mutagenesis.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking RNA targeting, phosphorylation, and chromatin state","Structure of full-length AID engaged with in vivo targeting RNA/protein partners lacking","Mechanism distinguishing Ig-locus from genome-wide deamination undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[2,5,6,18,25]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[2,5,6]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[5,6,23,25]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[21,24]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[28,29]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[22,29,30]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,9,18]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[9,18]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[17,27,32,33]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7,11,12,26,31]}],"complexes":[],"partners":["RPA","HNRNP K","HNRNP L","HNRNP U","SERBP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9GZX7","full_name":"Single-stranded DNA cytosine deaminase","aliases":["Activation-induced cytidine deaminase","AID","Cytidine aminohydrolase"],"length_aa":198,"mass_kda":24.0,"function":"Single-stranded DNA-specific cytidine deaminase. 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to Drive B-cell Lymphomagenesis.","date":"2022","source":"Cancer discovery","url":"https://pubmed.ncbi.nlm.nih.gov/35443279","citation_count":27,"is_preprint":false},{"pmid":"27697833","id":"PMC_27697833","title":"UNG protects B cells from AID-induced telomere loss.","date":"2016","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27697833","citation_count":27,"is_preprint":false},{"pmid":"18296364","id":"PMC_18296364","title":"Effects of L-carnitine on obesity, diabetes, and as an ergogenic aid.","date":"2008","source":"Asia Pacific journal of clinical nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/18296364","citation_count":27,"is_preprint":false},{"pmid":"24851241","id":"PMC_24851241","title":"AID-induced remodeling of immunoglobulin genes and B cell fate.","date":"2014","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/24851241","citation_count":26,"is_preprint":false},{"pmid":"26355458","id":"PMC_26355458","title":"Cell Cycle Regulates Nuclear Stability of AID and Determines the Cellular Response to AID.","date":"2015","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26355458","citation_count":26,"is_preprint":false},{"pmid":"34411701","id":"PMC_34411701","title":"Helicase-AID: A novel molecular device for base editing at random genomic loci.","date":"2021","source":"Metabolic engineering","url":"https://pubmed.ncbi.nlm.nih.gov/34411701","citation_count":26,"is_preprint":false},{"pmid":"38059475","id":"PMC_38059475","title":"Challenges and advances in serological and molecular tests to aid leprosy diagnosis.","date":"2023","source":"Experimental biology and medicine (Maywood, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/38059475","citation_count":25,"is_preprint":false},{"pmid":"25333851","id":"PMC_25333851","title":"AID and APOBEC deaminases: balancing DNA damage in epigenetics and immunity.","date":"2014","source":"Epigenomics","url":"https://pubmed.ncbi.nlm.nih.gov/25333851","citation_count":25,"is_preprint":false},{"pmid":"22429851","id":"PMC_22429851","title":"The AID dilemma: infection, or cancer?","date":"2012","source":"Advances in cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/22429851","citation_count":25,"is_preprint":false},{"pmid":"34299629","id":"PMC_34299629","title":"A Review on Microfluidics: An Aid to Assisted Reproductive Technology.","date":"2021","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/34299629","citation_count":25,"is_preprint":false},{"pmid":"35975606","id":"PMC_35975606","title":"AID function in somatic hypermutation and class switch recombination.","date":"2022","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/35975606","citation_count":24,"is_preprint":false},{"pmid":"32265934","id":"PMC_32265934","title":"Estrogen Reverses HDAC Inhibitor-Mediated Repression of Aicda and Class-Switching in Antibody and Autoantibody Responses by Downregulation of miR-26a.","date":"2020","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32265934","citation_count":23,"is_preprint":false},{"pmid":"15003109","id":"PMC_15003109","title":"Transcription-coupled mutagenesis by the DNA deaminase AID.","date":"2004","source":"Genome biology","url":"https://pubmed.ncbi.nlm.nih.gov/15003109","citation_count":23,"is_preprint":false},{"pmid":"25381386","id":"PMC_25381386","title":"IL-10 regulates Aicda expression through miR-155.","date":"2014","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/25381386","citation_count":21,"is_preprint":false},{"pmid":"30701532","id":"PMC_30701532","title":"HIV-1 Tat protein induces aberrant activation of AICDA in human B-lymphocytes from peripheral blood.","date":"2019","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/30701532","citation_count":21,"is_preprint":false},{"pmid":"27142677","id":"PMC_27142677","title":"Enrichment of rare variants in population isolates: single AICDA mutation responsible for hyper-IgM syndrome type 2 in Finland.","date":"2016","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/27142677","citation_count":21,"is_preprint":false},{"pmid":"29370398","id":"PMC_29370398","title":"Heterologous expression, characterization and possible functions of the chitin deacetylases, Cda1 and Cda2, from mushroom Coprinopsis cinerea.","date":"2018","source":"Glycobiology","url":"https://pubmed.ncbi.nlm.nih.gov/29370398","citation_count":20,"is_preprint":false},{"pmid":"23178850","id":"PMC_23178850","title":"AID and Apobec3G haphazard deamination and mutational diversity.","date":"2012","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/23178850","citation_count":20,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":41923,"output_tokens":7400,"usd":0.118385,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16761,"output_tokens":4579,"usd":0.09914,"stage2_stop_reason":"end_turn"},"total_usd":0.217525,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"AID is required for both class switch recombination (CSR) and somatic hypermutation (SHM) in B cells; AID-/- mice show complete defects in both processes, and overexpression of AID in CH12F3-2 cells augments class switching without cytokine stimulation.\",\n      \"method\": \"Knockout mouse model, transgenic overexpression, in vitro B cell stimulation assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function KO with defined cellular phenotype replicated in two independent papers (PMID:11007474, PMID:11007475)\",\n      \"pmids\": [\"11007474\", \"11007475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Mutations in the human AICDA gene cause autosomal recessive hyper-IgM syndrome type 2 (HIGM2), characterized by absence of CSR, lack of somatic hypermutation, and lymph node hyperplasia with giant germinal centers.\",\n      \"method\": \"Genetic sequencing of HIGM2 patients, phenotypic characterization\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetic loss-of-function with defined immunological phenotype, replicated in patient cohort\",\n      \"pmids\": [\"11007475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"AID functions by deaminating dC residues in DNA (not RNA); expression of AID in E. coli produces a mutator phenotype with C/G transitions that is enhanced by UNG deficiency, demonstrating a DNA deamination mechanism.\",\n      \"method\": \"E. coli mutator assay, UNG-deficient bacteria, context-dependent mutation analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro/bacterial reconstitution with genetic epistasis (UNG deficiency), foundational mechanistic paper\",\n      \"pmids\": [\"12097915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"AID is required for immunoglobulin gene conversion in chicken DT40 B cells; disruption of AID completely blocks Ig gene conversion, and reintroduction of AID cDNA rescues this block.\",\n      \"method\": \"Gene disruption in DT40 cells, complementation with AID cDNA\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype and genetic rescue in avian model system\",\n      \"pmids\": [\"11847344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Ectopic expression of AID alone is sufficient to induce somatic hypermutation in an actively transcribed GFP reporter in NIH 3T3 fibroblasts; mutation frequency correlates with transcription level.\",\n      \"method\": \"Ectopic AID expression in fibroblasts, GFP reporter mutation assay, transcription-level correlation\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function in non-B cells with quantitative mutation readout, single lab but orthogonal controls\",\n      \"pmids\": [\"12065838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"AID deaminates cytidines specifically on single-stranded DNA (ssDNA) but not double-stranded DNA (dsDNA) in vitro; dsDNA can be deaminated when the reaction is coupled to transcription, which generates ssDNA secondary structures, and this transcriptional orientation-dependence matches in vivo CSR requirements.\",\n      \"method\": \"In vitro cytidine deaminase assay on ssDNA and dsDNA substrates, transcription-coupled deamination assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay with defined substrates, transcription coupling demonstrated, functional correlation with in vivo CSR\",\n      \"pmids\": [\"12692563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Purified AID catalyzes processive C-to-U deamination on ssDNA preferentially at 5' WRC hotspot sequences; AID introduces multiple deaminations per DNA strand (10–70 per clone) rather than distributively; AID shows 15-fold preference for the non-transcribed strand exposed by RNA polymerase.\",\n      \"method\": \"In vitro deamination assay with purified AID on ssDNA, mutation spectrum analysis, transcribed dsDNA substrate assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purified enzyme in vitro assay with quantitative processivity analysis and hotspot characterization\",\n      \"pmids\": [\"12819663\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Constitutive ubiquitous expression of AID in transgenic mice causes T cell lymphomas and epithelial micro-adenomas; point mutations are massively introduced in TCR and c-myc genes, demonstrating AID can mutate non-Ig oncogenes.\",\n      \"method\": \"AID transgenic mouse model, tumor sequencing, mutation analysis of TCR and c-myc genes\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic model with defined tumor phenotype and molecular mutation characterization\",\n      \"pmids\": [\"12732658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"AID is phosphorylated on Ser38 by protein kinase A (PKA) in B cells; phosphorylation enables AID to associate with replication protein A (RPA) and promotes deamination of transcribed dsDNA; mutation of the PKA site preserves ssDNA deamination but markedly reduces RPA-dependent dsDNA deamination and severely impairs CSR in vivo.\",\n      \"method\": \"Biochemical phosphorylation assay with recombinant PKA, AID-RPA co-immunoprecipitation, site-directed mutagenesis, in vivo CSR assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of phosphorylation and protein interaction, mutagenesis, and in vivo functional validation\",\n      \"pmids\": [\"16251902\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"DNA double-strand breaks (DSBs) in Ig switch regions during CSR are AID-dependent and UNG-dependent, occur preferentially at WRC/GYW AID hotspot motifs, and AID attacks cytosines on both DNA strands.\",\n      \"method\": \"Ligation-mediated PCR detection of DSBs in splenic B cells, AID-/- and UNG-/- genetic ablation\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct detection of DSBs with genetic epistasis using two independent KO mouse lines\",\n      \"pmids\": [\"16103411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"5-methylcytosine (methylated CpG) is protected from AID-mediated deamination in vitro; unmethylated cytidines adjacent to CpGs are not protected, indicating methylation does not provide broader protection.\",\n      \"method\": \"In vitro deamination assay on methylated and unmethylated plasmid substrates with purified AID\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro assay, single lab, single method\",\n      \"pmids\": [\"15607819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AID deficiency prevents Bcl6-dependent germinal center-derived B cell lymphoma in mouse models, but has no impact on pre-GC Myc-driven lymphomas, demonstrating AID is required specifically for GC-derived lymphomagenesis through CSR/SHM-mediated genetic alterations.\",\n      \"method\": \"Genetic cross of AID-/- mice with Bcl6-, Myc-, and Myc/Bcl6-transgenic lymphoma models\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in multiple mouse lymphoma models with defined molecular pathway\",\n      \"pmids\": [\"18066064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"AID is required for c-myc to IgH variable-region (V-JH) chromosomal translocations in IL-6 transgenic mice; these translocations are absent in AID-/- IL-6 transgenic mice.\",\n      \"method\": \"Genetic cross of AID-/- mice with IL-6 transgenic model, translocation detection by PCR\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic ablation with specific molecular translocation readout\",\n      \"pmids\": [\"17724134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"AID is phosphorylated at both Ser38 and Thr140; mutation of either site does not affect catalytic activity but impairs CSR and somatic hypermutation in vivo, with T140 phosphorylation preferentially affecting somatic mutation.\",\n      \"method\": \"Mass spectrometry identification of phosphorylation sites, alanine substitution mutagenesis, in vivo CSR and SHM assays in haploinsufficient mice\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mass spectrometry identification plus mutagenesis and in vivo functional assays, single lab with orthogonal methods\",\n      \"pmids\": [\"18838546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"BCR engagement inhibits AID gene expression through Ca2+/calmodulin-dependent inhibition of the E2A transcription factor; calmodulin overexpression inhibits AID expression, and calmodulin-binding-site-mutated E2A renders AID expression resistant to BCR-mediated inhibition.\",\n      \"method\": \"BCR stimulation assays, calmodulin overexpression, E2A mutagenesis, AID expression analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional genetic experiments with mutagenesis, single lab\",\n      \"pmids\": [\"18203819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The estrogen-estrogen receptor complex binds directly to the AID promoter, enhancing AID mRNA and protein expression, leading to increases in SHM and CSR at the Ig locus, and enhanced c-myc translocations.\",\n      \"method\": \"Promoter binding assay (ChIP/reporter), AID mRNA/protein expression analysis, functional CSR and SHM assays, translocation analysis\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct promoter binding demonstrated, functional consequences in multiple orthogonal assays, single lab\",\n      \"pmids\": [\"19139166\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"B cell-specific and stimulation-responsive enhancer elements in the Aicda first intron overcome silencer elements to derepress AID expression; the intron contains binding sites for ubiquitous silencers c-Myb and E2f and B cell-specific activators Pax5 and E-box-binding proteins.\",\n      \"method\": \"Reporter assay, phylogenetic footprinting, histone acetylation mapping, mutagenesis of regulatory elements in CH12F3-2 cells\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional regulatory element mapping with mutagenesis, single lab, multiple methods\",\n      \"pmids\": [\"19966806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"AID (AICDA) is required for active DNA demethylation at OCT4 and NANOG promoters during reprogramming toward pluripotency; AID protein binds methylated silent promoters in fibroblasts but not active demethylated promoters in ES cells; siRNA knockdown of AID prevents promoter demethylation and induction of OCT4 and NANOG.\",\n      \"method\": \"siRNA knockdown in human-mouse heterokaryons, promoter methylation analysis, AID protein binding assay, gene expression analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined molecular phenotype (DNA demethylation), protein binding assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"20027182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Uracil residues generated by AID deamination are physically present in immunoglobulin variable and switch region DNA of stimulated B cells; they are present on both strands, replace mainly cytosine, appear within 24 hours of stimulation, and are AID-dependent.\",\n      \"method\": \"Uracil-DNA glycosylase sensitivity assay, abasic endonuclease assay, multiple detection methods in AID-/- and wild-type B cells\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct physical detection of AID-generated uracil in DNA with multiple orthogonal methods and genetic controls\",\n      \"pmids\": [\"21151102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A knock-in AID(G23S) mutation selectively impairs somatic hypermutation while preserving normal immunoglobulin levels; AID(G23S) mice develop germinal center hyperplasia and defective mucosal defense, demonstrating SHM has a distinct function from CSR in intestinal homeostasis.\",\n      \"method\": \"Knock-in point mutation mouse model, Ig quantification, germinal center analysis, bacterial challenge assays\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — precise knock-in mutation separating SHM from CSR functions with in vivo phenotypic readouts\",\n      \"pmids\": [\"21258321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"RNA exosome regulation of noncoding RNA (xTSS-RNAs) recruits AID to single-stranded DNA-forming sites of antisense and divergent transcription; Exosc3-deficient B cells have impaired CSR and SHM; divergently transcribed ncRNA-associated genomic loci accumulate AID-mediated mutations and translocations.\",\n      \"method\": \"Conditional Exosc3 KO mouse model, transcriptome analysis, AID recruitment assay, ChIP, SSB structure analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with defined molecular phenotype, AID recruitment demonstrated, multiple orthogonal genomic methods\",\n      \"pmids\": [\"25119026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Intronic switch RNA (generated after lariat debranching) acts in trans to target AID to switch region DNA via G-quadruplex structures formed by the RNA; AID binds directly to switch RNA; mutation of a key residue in AID's putative RNA-binding domain impairs AID recruitment to S regions and abolishes CSR; inhibition of RNA lariat processing similarly disrupts AID localization and CSR.\",\n      \"method\": \"RNA-AID binding assay, G-quadruplex biochemical analysis, AID mutagenesis, RNA lariat processing inhibition, AID ChIP, CSR functional assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct RNA-protein binding, mutagenesis, and in vivo functional rescue experiments in single rigorous study\",\n      \"pmids\": [\"25957684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"AID undergoes nuclear degradation more slowly in G1 phase than in S or G2-M phase; enforced nuclear localization of AID in G1 accelerates SHM and CSR and is well-tolerated, while nuclear AID in S-G2/M phase compromises cell viability; regulatory phosphorylation and catalytic activity mutations alter AID nuclear stability.\",\n      \"method\": \"High content screening microscopy, cell cycle-specific degradation tag fusions, CSR and SHM functional assays, AID stability measurements\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cell-cycle-regulated localization with functional consequences, single lab with multiple methods\",\n      \"pmids\": [\"26355458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"AID binds to transcribed dsDNA and translocates unidirectionally in concert with RNA polymerase on moving transcription bubbles, while increasing the fraction of stalled bubbles; when constrained in a model bubble, AID scans randomly; on unconstrained ssDNA, AID moves bidirectionally in short slides/hops.\",\n      \"method\": \"Single-molecule FRET analysis of AID on transcribed dsDNA and ssDNA substrates\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule FRET providing direct mechanistic resolution of AID movement, single lab\",\n      \"pmids\": [\"26681117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The AID C terminus is required for stable dimer formation; AID monomers associate with DNA cleavage cofactor hnRNP K, whereas AID dimers associate with recombination cofactors hnRNP L, hnRNP U, and Serpine mRNA-binding protein 1; all AID/ribonucleoprotein associations are RNA-dependent.\",\n      \"method\": \"Bimolecular fluorescence complementation (BiFC), glycerol gradient fractionation, co-immunoprecipitation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — BiFC and fractionation with co-IP, single lab, multiple methods\",\n      \"pmids\": [\"26929374\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structures of human AID (MBP-fused) alone and in complex with deoxycytidine monophosphate reveal a bifurcated substrate-binding surface that captures two adjacent single-stranded overhangs simultaneously; G-quadruplex substrates mimicking Ig switch regions are preferred AID substrates; G4 substrates induce cooperative AID oligomerization; structure-based mutations disrupting bifurcated substrate recognition or oligomerization both compromise CSR in splenic B cells.\",\n      \"method\": \"X-ray crystallography, in vitro deamination assays, site-directed mutagenesis, in vivo CSR assay in splenic B cells\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation by mutagenesis and in vivo CSR, multiple orthogonal methods in single study\",\n      \"pmids\": [\"28757211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"EGFR T790M resistance mutation is acquired through AICDA-mediated deamination of 5-methylcytosine at position c.2369; EGFR TKI treatment activates NFκB which induces AICDA expression; pharmacologic inhibition of NFκB or AICDA knockout prevents T790M mutation development.\",\n      \"method\": \"AICDA knockout, NFκB inhibition, 5-methylcytosine deamination assay, mutation frequency analysis in lung cancer cells\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO and pharmacological inhibition with specific mutation readout, single lab, multiple methods\",\n      \"pmids\": [\"30333118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TET2 and TET3 enhance AID (Aicda) expression in B cells by depositing 5-hydroxymethylcytosine (5hmC) and maintaining chromatin accessibility at two superenhancer elements (TetE1, TetE2) in the Aicda locus; BATF facilitates TET recruitment to TetE1; TET-dependent Aicda expression regulates CSR.\",\n      \"method\": \"Conditional Tet2/Tet3 KO in B cells, 5hmC mapping (ChIP-seq), ATAC-seq, BATF-deficient B cells, Aicda expression and CSR assays\",\n      \"journal\": \"Science immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with epigenomic mapping and functional CSR readout, multiple orthogonal methods\",\n      \"pmids\": [\"31028100\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"AID protein is predominantly localized in the cytoplasm of normal germinal center centroblasts and malignant B cells (Burkitt lymphoma), as detected using specific antibodies; cytoplasmic localization suggests additional regulatory mechanisms for its nuclear function.\",\n      \"method\": \"Immunohistochemistry and immunofluorescence with specific anti-AID antibodies in normal and neoplastic B cells\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct protein localization by IHC/IF in multiple cell types, single lab, replicated in subsequent paper (PMID:16439679)\",\n      \"pmids\": [\"15304391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Nuclear AID is detected in ~2.5% of germinal center cells specifically in the dark zone and outer zone (but not light zone); AID is relocalized to the nucleus in cycling CDKN1B-/CCNB1- GC blasts and in extrafollicular large B cells (14% with nuclear AID); nuclear/cytoplasmic distribution is consistent with the topography of SHM and CSR.\",\n      \"method\": \"Immunohistochemistry, immunofluorescence, co-staining with cell cycle markers in human tonsil GC sections\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct subcellular localization tied to functional context (SHM/CSR zones), single lab\",\n      \"pmids\": [\"16439679\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"APOBEC3B nuclear import requires an N-terminal motif analogous to AID's nuclear localization determinant, and A3B interacts with the same subset of importin proteins as AID, suggesting mechanistic conservation of nuclear import between AID and A3B.\",\n      \"method\": \"Mutagenesis of nuclear localization determinant, importin co-immunoprecipitation, nuclear localization assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis and co-IP for importin interaction, single lab\",\n      \"pmids\": [\"22446380\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Chronic Plasmodium infection prolongs germinal center expansion and AID expression, leading to widespread DNA damage in GC B cells and chromosome translocations; AID-dependent mature B cell lymphomas with translocations are favored by malaria infection.\",\n      \"method\": \"Mouse Plasmodium chabaudi chronic infection model, GC analysis, DNA damage assays, AID-/- genetic ablation, lymphoma characterization\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic ablation (AID-/-) with molecular translocation readout in defined in vivo infectious model\",\n      \"pmids\": [\"26276629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"AICDA overexpression drives increased cytosine methylation heterogeneity in BCL2-driven murine lymphomas without increasing somatic mutation burden; AICDA depletion in normal GC B cells reduces cytosine methylation heterogeneity, identifying AICDA as a driver of epigenetic heterogeneity.\",\n      \"method\": \"AICDA transgenic overexpression and shRNA depletion in mouse lymphoma models, whole-genome bisulfite sequencing for methylation heterogeneity analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with genome-wide epigenetic readout, single lab\",\n      \"pmids\": [\"29335468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SETD2 haploinsufficiency enhances AICDA-induced somatic hypermutation selectively on the nontemplate DNA strand; H3K36me3 loss (from SETD2 deficiency) is associated with greater RNA polymerase II processivity and increased mutational burden; SETD2-mediated H3K36me3 is required for proper sensing of AID-induced cytosine deamination.\",\n      \"method\": \"Heterozygous Setd2 KO mouse model, ChIP-seq for H3K36me3, RNAPII ChIP-seq, whole genome sequencing for mutation analysis, AICDA-dependent SHM strand analysis\",\n      \"journal\": \"Cancer discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic model with chromatin and mutational genomic analysis, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"35443279\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"AICDA (AID) is a B cell-specific ssDNA cytidine deaminase that converts cytosine to uracil at WRC hotspot motifs on single-stranded DNA exposed during transcription; it requires PKA-mediated phosphorylation at Ser38 (enabling RPA association for dsDNA access) and Thr140, forms dimers via its C-terminus to interact with hnRNP cofactors, is targeted to Ig switch regions through G-quadruplex-containing switch RNA and RNA exosome-regulated antisense noncoding RNA, acts processively while tracking with RNA polymerase II on transcription bubbles, and initiates both somatic hypermutation and class switch recombination—as well as active DNA demethylation at developmental loci—while its expression is tightly regulated at the transcriptional level (by NF-κB, Pax5, E2A, BATF/TET-mediated superenhancer activity, and BCR-calmodulin signaling) and post-translationally through nuclear-cytoplasmic shuttling that is cell-cycle regulated.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"AICDA (AID) is a B cell single-stranded DNA cytidine deaminase that initiates antibody diversification, serving as the obligate trigger for both class switch recombination (CSR) and somatic hypermutation (SHM) — processes that are completely abolished in its absence and underlie autosomal recessive hyper-IgM syndrome type 2 in humans [#0, #1]. Mechanistically, AID converts deoxycytidine to deoxyuridine in DNA, not RNA, producing a mutator phenotype that is amplified by loss of uracil excision; this generates uracil lesions physically detectable on both strands of Ig variable and switch DNA, whose processing yields the AID-dependent, UNG-dependent double-strand breaks at WRC/GYW hotspots that drive recombination [#2, #9, #18]. Catalysis is restricted to single-stranded DNA and is coupled to transcription, which exposes ssDNA; the enzyme acts processively, tracking unidirectionally with RNA polymerase on transcription bubbles and preferentially deaminating the exposed non-transcribed strand at 5'-WRC motifs [#5, #6, #23]. Crystallographic analysis reveals a bifurcated substrate-binding surface that engages two adjacent ssDNA overhangs and favors G-quadruplex substrates mimicking switch regions, with G4-induced cooperative oligomerization required for CSR [#25]. Substrate access to double-stranded DNA additionally requires PKA phosphorylation at Ser38, which enables RPA association, and phosphorylation at Thr140 contributes preferentially to SHM, allowing the two arms of antibody diversification to be genetically separated [#8, #13, #19]. AID is targeted to its genomic substrates by noncoding RNA: intronic switch RNA acting in trans via G-quadruplex structures, and RNA-exosome-regulated antisense/divergent transcripts that mark ssDNA-forming loci [#20, #21]. Because AID is a promiscuous mutagen, its activity is constrained by transcriptional control (Pax5/E-box activators, c-Myb/E2f silencers in the first intron, BCR-calmodulin inhibition of E2A, estrogen-receptor and NF-\\u03baB induction, and BATF/TET-dependent superenhancer activity) and by cell-cycle-regulated nuclear-cytoplasmic shuttling that limits genotoxic nuclear exposure to G1 [#14, #15, #16, #22, #27, #29]. Beyond immunity, AID mediates active DNA demethylation at OCT4 and NANOG during reprogramming and shapes epigenetic methylation heterogeneity in lymphomas [#17, #32]. Its off-target activity causes c-myc/IgH translocations and germinal-center-derived lymphomas, and deamination of 5-methylcytosine can generate oncogenic mutations such as EGFR T790M [#7, #11, #12, #26, #31].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that a single factor controls antibody diversification, AID was shown to be required for both CSR and SHM and causally linked to a human immunodeficiency, defining the gene's central physiological role.\",\n      \"evidence\": \"AID-/- mouse knockout with CSR/SHM defects, transgenic overexpression in CH12F3-2 cells, and genetic sequencing of HIGM2 patients\",\n      \"pmids\": [\"11007474\", \"11007475\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the biochemical substrate (DNA vs RNA)\", \"Did not establish enzymatic mechanism or targeting\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Resolving the long-debated substrate question, AID was shown to act as a DNA cytidine deaminase rather than an RNA-editing enzyme, and to be sufficient to drive hypermutation of a transcribed reporter in non-lymphoid cells.\",\n      \"evidence\": \"E. coli mutator assay with UNG-deficiency epistasis, Ig gene conversion rescue in DT40 cells, and ectopic AID expression with a GFP reporter in fibroblasts\",\n      \"pmids\": [\"12097915\", \"11847344\", \"12065838\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not show strand or sequence preference of purified enzyme\", \"Did not address how transcription exposes substrate in vivo\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defining the enzyme's intrinsic biochemistry, purified AID was shown to deaminate ssDNA processively at WRC hotspots and to access dsDNA only when coupled to transcription, explaining its transcription dependence in vivo.\",\n      \"evidence\": \"In vitro deamination assays on ssDNA/dsDNA, transcription-coupled deamination, mutation spectrum and processivity analysis with purified AID\",\n      \"pmids\": [\"12692563\", \"12819663\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not explain genomic targeting specificity to Ig loci\", \"Did not identify cofactors or post-translational regulation\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Connecting signaling to enzymatic access, PKA phosphorylation at Ser38 was shown to enable RPA association and dsDNA deamination, providing a regulatable switch for CSR distinct from intrinsic ssDNA catalysis.\",\n      \"evidence\": \"Recombinant PKA phosphorylation assay, AID-RPA co-IP, site-directed mutagenesis, and in vivo CSR assays; complemented by LM-PCR detection of AID/UNG-dependent switch-region DSBs\",\n      \"pmids\": [\"16251902\", \"16103411\", \"15607819\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map all phosphosites or their division of labor between CSR and SHM\", \"Did not resolve how phosphorylation is spatially restricted\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Refining the regulatory code, a second phosphosite (Thr140) was identified that preferentially supports SHM, and BCR-calmodulin-E2A signaling was shown to repress AID transcription, revealing layered control of a dangerous mutator.\",\n      \"evidence\": \"Mass spectrometry phosphosite mapping with alanine-substitution mice, plus BCR stimulation, calmodulin overexpression, and E2A mutagenesis\",\n      \"pmids\": [\"18838546\", \"18203819\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not establish kinase identity for T140\", \"Mechanistic separation of CSR vs SHM functions remained partial\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Extending function beyond immunity, AID was shown to be required for active DNA demethylation at pluripotency promoters during reprogramming, and AID-generated uracil was directly detected in Ig DNA, confirming the deamination-then-repair model in vivo.\",\n      \"evidence\": \"siRNA knockdown in heterokaryons with promoter methylation/binding analysis, and direct uracil detection by UDG/abasic-endonuclease assays in stimulated B cells\",\n      \"pmids\": [\"20027182\", \"21151102\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demethylation mechanism (5mC deamination vs indirect) not fully resolved\", \"Did not define how AID is targeted to non-Ig developmental loci\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Solving the genomic targeting problem, noncoding RNAs were shown to recruit AID to ssDNA-forming sites — intronic switch RNA via G-quadruplexes in trans, and RNA-exosome-regulated antisense/divergent transcripts — while single-molecule and cell-cycle studies defined how AID moves with RNAPII and is spatially restricted.\",\n      \"evidence\": \"RNA-AID binding and G4 biochemistry with mutagenesis and CSR rescue; conditional Exosc3 KO with AID recruitment/ChIP; smFRET of AID on transcription bubbles; cell-cycle degradation-tag and localization studies\",\n      \"pmids\": [\"25957684\", \"25119026\", \"26681117\", \"26355458\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"RNA-binding interface on AID not fully mapped structurally\", \"How ncRNA and phosphorylation cues are integrated remains unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linking oligomeric state to cofactor selection, the AID C-terminus was shown to control dimerization, with monomers and dimers engaging distinct hnRNP cofactors in an RNA-dependent manner, partitioning DNA cleavage from recombination functions.\",\n      \"evidence\": \"BiFC, glycerol gradient fractionation, and co-immunoprecipitation\",\n      \"pmids\": [\"26929374\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-IP without reciprocal/structural validation of individual hnRNP contacts\", \"Functional consequences of each cofactor association not dissected in vivo\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Providing atomic-resolution mechanism, crystal structures revealed a bifurcated substrate-binding surface capturing two adjacent ssDNA overhangs and a preference for G-quadruplex switch substrates that drives cooperative oligomerization required for CSR.\",\n      \"evidence\": \"X-ray crystallography of MBP-AID alone and with dCMP, in vitro deamination, structure-guided mutagenesis, and in vivo splenic-B-cell CSR assays\",\n      \"pmids\": [\"28757211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of full-length AID bound to physiological RNA/DNA complexes\", \"Structural basis of phosphoregulation and RPA contact not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connecting chromatin state to mutational targeting, SETD2/H3K36me3 was shown to constrain AID-induced SHM on the nontemplate strand, demonstrating that chromatin modifications tune the genomic consequences of AID activity, alongside roles in oncogenic mutation and translocation.\",\n      \"evidence\": \"Heterozygous Setd2 KO mice with H3K36me3 and RNAPII ChIP-seq, whole-genome mutation analysis; complemented by lymphoma models linking AID to c-myc/IgH translocations, GC-derived lymphomagenesis, methylation heterogeneity, and EGFR T790M\",\n      \"pmids\": [\"35443279\", \"18066064\", \"17724134\", \"12732658\", \"29335468\", \"30333118\", \"26276629\", \"19139166\", \"19966806\", \"31028100\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How chromatin marks are mechanistically read by the AID/repair machinery is unclear\", \"Determinants of on- vs off-target genomic specificity remain incompletely defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how the structural, phosphoregulatory, ncRNA-targeting, cofactor, and chromatin inputs are integrated into a single coherent rule that directs AID to physiological Ig loci while limiting genome-wide off-target mutagenesis.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking RNA targeting, phosphorylation, and chromatin state\", \"Structure of full-length AID engaged with in vivo targeting RNA/protein partners lacking\", \"Mechanism distinguishing Ig-locus from genome-wide deamination undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [2, 5, 6, 18, 25]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [2, 5, 6]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [5, 6, 23, 25]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [21, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [28, 29]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [22, 29, 30]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 9, 18]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [9, 18]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [17, 27, 32, 33]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 11, 12, 26, 31]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RPA\", \"hnRNP K\", \"hnRNP L\", \"hnRNP U\", \"SERBP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}