{"gene":"TG_240060","gene_symbol":"IST","run_date":"2026-09-10T21:09:19","timeline":{"discoveries":[{"year":2016,"finding":"TgIST (T. gondii inhibitor of STAT1 transcriptional activity) is secreted by intracellular parasites, traffics to the host cell nucleus, sequesters STAT1 on IFN-γ-responsive loci, and recruits the NuRD (nucleosome remodeling deacetylase) transcriptional repressor complex to establish non-permissive chromatin and block STAT1-dependent gene expression.","method":"Co-immunoprecipitation, nuclear fractionation, chromatin immunoprecipitation, genetic deletion of TgIST (ΔTgist parasites) with phenotypic rescue, live imaging of nuclear trafficking","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ChIP, subcellular fractionation, and clean KO with defined immune phenotype; independently replicated in a concurrent paper (PMID:27414498)","pmids":["27503074"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2016,"finding":"TgIST translocates to the host cell nucleus and recruits the Mi-2/NuRD (nucleosome remodeling and deacetylase) complex to STAT1-bound promoters, resulting in altered chromatin and blocked IFN-γ-dependent transcription; TgIST is conserved across all three T. gondii strains, and its deletion increases parasite clearance in IFN-γ-activated cells and reduces virulence in mice.","method":"Co-immunoprecipitation, chromatin immunoprecipitation, genetic deletion (ΔTgist), mouse virulence assays, IFN-γ receptor-deficient mouse rescue experiments","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ChIP, KO, in vivo rescue), independently replicated by Gay et al. 2016 (PMID:27503074)","pmids":["27414498"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"Type I"},{"species":"Toxoplasma gondii","strain":"Type II"},{"species":"Toxoplasma gondii","strain":"Type III"}]},{"year":2019,"finding":"TgIST blocks type I IFN (IFN-β) signaling in addition to IFN-γ, inhibiting STAT1/STAT2-mediated transcription in infected cells; ΔTgist parasites show increased susceptibility to IFN-β-activated macrophage killing, and reduced virulence of ΔTgist parasites is restored in Ifnar1-/- mice.","method":"Genetic deletion (ΔTgist), IFN-β stimulation assays, murine infection models with Ifnar1-/- mice, macrophage killing assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean KO with defined phenotype, in vivo genetic rescue with receptor-deficient mice, multiple cell types tested","pmids":["31413201"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"finding":"TgIST is an intrinsically disordered protein; its internal repeat region adopts a helical conformation upon binding to phosphorylated STAT1 dimers at a groove formed by two loops in the STAT1 SH2 domains that become exposed upon dimerization, and this binding prevents recruitment of co-transcriptional activators without displacing STAT1 from DNA.","method":"Structural analysis (X-ray crystallography), biochemical binding assays, site-directed mutagenesis of TgIST repeat region and STAT1 SH2 domain, cellular reporter assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis, biochemical reconstitution, and cellular validation in a single rigorous study","pmids":["35831295"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"finding":"TgIST binds more efficiently to STAT1 tetramers than dimers; binding requires the N-terminal domain of STAT1 (N-terminal deletion abrogates binding) and the ability of STAT1 to form tetramers (STAT1F77A substitution that prevents tetramerization abolishes TgIST binding). TgIST binding increases STAT1 affinity for DNA consensus sequences and enables binding to non-consensus sequences, retaining STAT1 in a phosphorylated, DNA-bound nuclear state.","method":"Co-immunoprecipitation with STAT1 deletion/point mutants, EMSA (electrophoretic mobility shift assay), nuclear retention/fractionation assays","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (Co-IP, EMSA, mutagenesis) in a single lab establishing structural requirements for TgIST-STAT1 interaction","pmids":["29968354"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"finding":"TgIST inhibits IFN-γ-induced IDO1 (indoleamine 2,3-dioxygenase 1) mRNA expression in human cells, thereby antagonizing the tryptophan-degradation-dependent anti-parasitic response; IDO1 but not IDO2 is required for IFN-γ-induced cell-autonomous immunity to T. gondii in human cells.","method":"TgIST-deficient parasite infection, RT-PCR/qPCR for IDO1 mRNA, siRNA knockdown of IDO1/IDO2, parasite growth assays in human cell lines","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean functional readout with KO parasites and siRNA, single lab, limited mechanistic depth on how TgIST suppresses IDO1 transcription","pmids":["30283439"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"TgIST acts together with the bradyzoite-stage effector TgNSM (which targets the NCoR/SMRT repressor complex) to block IFN-driven expression of PKR and MLKL, thereby preventing host cell necroptotic death and protecting the parasite's intracellular niche.","method":"Genetic deletion of TgIST and TgNSM individually and in combination, IFN stimulation assays, necroptosis readouts (MLKL phosphorylation, cell death assays), Co-IP of TgNSM with NCoR/SMRT","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 2 / Moderate — combinatorial KO analysis with defined molecular pathway (PKR/MLKL necroptosis axis), orthogonal cell death and gene expression assays","pmids":["34043960"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"Bradyzoite-stage T. gondii exports IST in a MYR1-dependent manner to suppress IFN-γ signaling in host cells; loss of IST in bradyzoites impairs suppression of IFNγ signaling and reduces protection of host cells from IFNγ-mediated cell death.","method":"Genetic deletion of IST and MYR1 in bradyzoite-stage parasites, transcriptomic analysis, IFN signaling reporter assays, cell death assays","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean stage-specific KO with multiple orthogonal readouts (transcriptomics, cell death), demonstrates functional conservation in bradyzoite stage","pmids":["34921775"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"finding":"T. gondii IST suppresses inflammatory responses to Hammondia hammondi infection when co-infecting cells; the H. hammondi IST ortholog shows reduced functionality compared to T. gondii IST, consistent with the more vigorous host response to H. hammondi infection.","method":"Co-infection experiments, conditioned media transfer, transcriptomic analysis, H. hammondi IST functional comparison with T. gondii IST","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional comparison of orthologs with transcriptomic readout, single lab, limited mechanistic depth on IST domain function differences","pmids":["32574210"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Hammondia hammondi","strain":""}]},{"year":2024,"finding":"TgIST is one of four nuclear-targeted dense granule effectors (along with GRA16, GRA24, GRA28) necessary for a complete block of IFNγ response in human cells; loss of all four leads to parasite premature egress and host cell death specifically in human (not murine) cells stimulated with IFNγ post-infection.","method":"Genome-wide loss-of-function screens in IFNγ-primed human fibroblasts, combinatorial KO parasites, cell death and egress assays in human vs. murine cells","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genome-wide screen validated by combinatorial KOs with defined mechanistic phenotype, species-specific functional distinction established","pmids":["39292011"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"finding":"TgIST suppresses STAT1 expression and downstream signaling (IRF-1, NF-κB, COX2, CIITA, iNOS, chemokines CXCL9/10/11) in hepatocytes stimulated with IFN-γ/TNF-α, and reduces expression of pro-apoptotic markers (Caspase3/8/9, P53, BAX), restoring cell viability.","method":"Stable transfection of hepatocyte cell line (Hepa-1c1c7) with TgIST, western blot, RT-PCR, flow cytometry for apoptosis markers","journal":"Parasites, hosts and diseases","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — heterologous expression system (no parasite), single lab, multiple readouts but no direct mechanistic dissection of how TgIST reduces STAT1 protein levels","pmids":["38443768"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"finding":"T. gondii infection (all three strain types) inhibits STAT1-mediated transcription by preventing STAT1 dissociation from DNA, thereby blocking its recycling for further rounds of transcriptional activation; this leads to increased and sustained STAT1-chromatin association at IFN-γ-responsive promoters. The effector is not derived from rhoptries, as secretion without full invasion is insufficient to block STAT1.","method":"ChIP assay, STAT1-DNA binding assays, rhoptry injection experiments without full parasite invasion, histone deacetylase inhibitor treatment","journal":"Infection and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and binding assays across multiple strain types, mechanistic exclusion of rhoptry origin; predates TgIST identification but establishes the STAT1 retention mechanism later attributed to TgIST","pmids":["24478085"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":"Type I"},{"species":"Toxoplasma gondii","strain":"Type II"},{"species":"Toxoplasma gondii","strain":"Type III"}]},{"year":2011,"finding":"T. gondii-infected macrophages cannot recruit BRG-1 or acetylate histones at IFN-γ-regulated promoters (CIITA pIV), and cannot recruit non-muscle actin to IFN-γ-responsive DNA sequences, leading to global unresponsiveness to IFN-γ; HDAC inhibitors restore IFN-γ responsiveness, implicating chromatin remodeling as the primary mechanism.","method":"Genome-wide transcriptomics, ChIP for BRG-1 and histone acetylation, mass spectrometry of GAS oligonucleotide-bound protein complexes, HDAC inhibitor rescue","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods including MS identification of missing chromatin factors and pharmacological rescue; predates TgIST identification but mechanistically characterizes the chromatin remodeling block","pmids":["22275866"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2026,"finding":"IST is one of eight MYR1-dependent dense granule effectors (IST, NSM, HCE1/TEEGR, GRA16, GRA18, GRA24, GRA28, GRA84) that collectively and additively activate the non-canonical NF-κB pathway (RelB/p52) by driving TRAF3 depletion, NIK stabilization, and p100 processing; no single effector is solely responsible.","method":"Combinatorial KO parasite panel, nuclear fractionation for RelB/p52, western blot for NIK/p100/TRAF3, MYR1-dependent export assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — combinatorial KO with defined molecular pathway readouts, preprint not yet peer-reviewed, single lab","pmids":["41959509"],"is_preprint":true,"attribution":[{"species":"Toxoplasma gondii","strain":"Type I"},{"species":"Toxoplasma gondii","strain":"Type II"}]}],"current_model":"TgIST is a secreted, intrinsically disordered dense granule protein that is exported via the MYR1 translocon into the host cell nucleus, where it binds phosphorylated STAT1 dimers and tetramers at a groove on the STAT1 SH2 domain exposed upon dimerization; this interaction locks STAT1 in a DNA-bound, non-recycling state, recruits the Mi-2/NuRD chromatin repressor complex to STAT1-occupied promoters, blocks co-activator recruitment, and thereby suppresses IFN-γ- and IFN-β-stimulated gene expression (including IDO1, PKR, MLKL, iNOS, and MHC class II genes) in both tachyzoite and bradyzoite stages to evade host immune defenses."},"narrative":{"mechanistic_narrative":"TgIST is a secreted dense granule effector of Toxoplasma gondii that traffics from intracellular parasites into the host cell nucleus, where it functions as a master antagonist of interferon-driven transcription to enable immune evasion [PMID:27503074, PMID:27414498]. Within the nucleus it sequesters phosphorylated STAT1 on IFN-γ-responsive promoters and recruits the Mi-2/NuRD nucleosome-remodeling and deacetylase repressor complex, establishing a non-permissive chromatin state that blocks STAT1-dependent gene expression [PMID:27503074, PMID:27414498]. This activity extends beyond IFN-γ: TgIST also suppresses type I IFN (IFN-β) signaling through STAT1/STAT2, and ΔTgist parasites show heightened susceptibility to both IFN-γ- and IFN-β-activated killing, with virulence restored in Ifnar1-/- mice [PMID:31413201]. Mechanistically, TgIST is an intrinsically disordered protein whose internal repeat region folds into a helix upon engaging a groove on the STAT1 SH2 domain exposed by dimerization; it binds phosphorylated STAT1 dimers and, more avidly, tetramers, locking STAT1 in a DNA-bound, non-recycling state and blocking co-activator recruitment without displacing STAT1 from DNA [PMID:35831295, PMID:29968354]. Functionally, TgIST represses effector genes including IDO1, PKR, MLKL, CIITA, and iNOS, thereby preventing tryptophan-starvation immunity and necroptotic host cell death and preserving the parasite's replicative niche in both tachyzoite and bradyzoite stages [PMID:30283439, PMID:34043960, PMID:34921775]. TgIST operates as one of several nuclear-targeted, MYR1-dependent dense granule effectors that together are required for complete blockade of the human IFN-γ response [PMID:34921775, PMID:39292011].","teleology":[{"year":2011,"claim":"Before the effector was known, the question was how T. gondii silences IFN-γ responses; infection was shown to prevent chromatin remodeling at IFN-γ promoters, establishing that the block operates at the level of chromatin rather than upstream signaling.","evidence":"Transcriptomics, ChIP for BRG-1/histone acetylation, MS of GAS-bound complexes, and HDAC inhibitor rescue in infected macrophages","pmids":["22275866"],"confidence":"Medium","gaps":["Did not identify the parasite effector responsible","Mechanism of NuRD/repressor recruitment not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2013,"claim":"It was unknown how infection sustains STAT1 occupancy; ChIP and binding assays showed infection prevents STAT1 dissociation from DNA, blocking its recycling and establishing the STAT1-retention mechanism, while excluding rhoptries as the source of the effector.","evidence":"ChIP, STAT1-DNA binding assays, rhoptry injection without full invasion, and HDAC inhibitor treatment across three strain types","pmids":["24478085"],"confidence":"Medium","gaps":["Effector identity still unknown","Did not distinguish dense granule origin directly"],"attribution":[{"species":"Toxoplasma gondii","strain":"Type I"},{"species":"Toxoplasma gondii","strain":"Type II"},{"species":"Toxoplasma gondii","strain":"Type III"}]},{"year":2016,"claim":"Two concurrent studies identified TgIST as the secreted, nucleus-trafficking effector that sequesters STAT1 on IFN-γ loci and recruits the Mi-2/NuRD complex, directly linking a defined parasite protein to the chromatin-level block and demonstrating its role in virulence.","evidence":"Co-IP, ChIP, nuclear fractionation, ΔTgist deletion with phenotypic rescue, and mouse virulence/IFN-γ receptor-deficient rescue experiments","pmids":["27503074","27414498"],"confidence":"High","gaps":["Structural basis of STAT1 binding not resolved","Whether other IFN pathways are targeted unaddressed"],"attribution":[{"species":"Toxoplasma gondii","strain":"Type I"},{"species":"Toxoplasma gondii","strain":"Type II"},{"species":"Toxoplasma gondii","strain":"Type III"}]},{"year":2018,"claim":"The structural requirements of the STAT1 interaction were unknown; TgIST was shown to bind STAT1 tetramers more efficiently than dimers, require the STAT1 N-terminal domain and tetramerization, and increase STAT1 DNA affinity, explaining how STAT1 is retained in a phosphorylated DNA-bound state.","evidence":"Co-IP with STAT1 deletion/point mutants (F77A), EMSA, and nuclear retention assays","pmids":["29968354"],"confidence":"High","gaps":["Atomic-resolution binding interface not defined","How binding excludes co-activators unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2018,"claim":"The downstream effector genes controlled were unclear; TgIST was shown to suppress IFN-γ-induced IDO1 in human cells, connecting STAT1 antagonism to blockade of tryptophan-starvation cell-autonomous immunity.","evidence":"ΔTgist infection, qPCR for IDO1, siRNA of IDO1/IDO2, and parasite growth assays in human cells","pmids":["30283439"],"confidence":"Medium","gaps":["Limited mechanistic depth on IDO1 transcriptional suppression","Restricted to human cell context"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2019,"claim":"Whether TgIST acts only on IFN-γ was open; it was shown to also block type I IFN (IFN-β) STAT1/STAT2 signaling, broadening its role to both interferon arms of host defense.","evidence":"ΔTgist deletion, IFN-β stimulation, macrophage killing assays, and Ifnar1-/- mouse rescue","pmids":["31413201"],"confidence":"High","gaps":["Whether STAT2-specific contacts differ from STAT1 not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"claim":"The evolutionary tuning of IST activity was addressed by comparing orthologs; T. gondii IST suppressed inflammatory responses more effectively than the Hammondia hammondi ortholog, correlating effector potency with the divergent host responses to each parasite.","evidence":"Co-infection, conditioned media transfer, transcriptomics, and functional comparison of T. gondii vs H. hammondi IST","pmids":["32574210"],"confidence":"Medium","gaps":["Domain-level basis for functional divergence not mapped","Single-lab comparison"],"attribution":[{"species":"Toxoplasma gondii","strain":""},{"species":"Hammondia hammondi","strain":""}]},{"year":2021,"claim":"How the parasite prevents host cell death was unclear; TgIST was shown to act with the bradyzoite effector TgNSM to block IFN-driven PKR and MLKL expression, preventing necroptosis and protecting the intracellular niche.","evidence":"Individual and combinatorial ΔTgist/ΔTgnsm deletion, MLKL phosphorylation and cell death readouts, and Co-IP of TgNSM with NCoR/SMRT","pmids":["34043960"],"confidence":"High","gaps":["Direct role of TgIST versus TgNSM at PKR/MLKL promoters not separated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"Whether IST functions in the chronic stage was unknown; bradyzoites were shown to export IST in a MYR1-dependent manner to suppress IFN-γ signaling and protect host cells from IFN-γ-mediated death, establishing stage-independent function and defining the export route.","evidence":"Stage-specific ΔIST and ΔMYR1 bradyzoite deletion, transcriptomics, IFN reporter and cell death assays","pmids":["34921775"],"confidence":"High","gaps":["Molecular details of MYR1-dependent translocation of IST not resolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"claim":"The atomic mechanism of STAT1 inhibition was resolved; TgIST is intrinsically disordered and its repeat region folds into a helix upon binding a dimerization-exposed groove on the STAT1 SH2 domain, blocking co-activator recruitment without displacing STAT1 from DNA.","evidence":"X-ray crystallography, biochemical binding assays, mutagenesis of the TgIST repeat and STAT1 SH2 domain, and cellular reporter assays","pmids":["35831295"],"confidence":"High","gaps":["How the DNA-bound complex physically recruits NuRD not structurally defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"claim":"The sufficiency of TgIST alone was tested; genome-wide screens showed it is one of four nuclear-targeted dense granule effectors (with GRA16, GRA24, GRA28) collectively required for complete IFN-γ blockade, with loss of all four causing premature egress specifically in human cells.","evidence":"Genome-wide loss-of-function screens in IFNγ-primed human fibroblasts, combinatorial KOs, and egress/cell death assays in human vs murine cells","pmids":["39292011"],"confidence":"High","gaps":["Individual contribution of TgIST within the four-effector set not quantified","Basis of human- versus murine-cell specificity unresolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2024,"claim":"Whether TgIST reduces STAT1 protein levels was tested in a heterologous system; stable TgIST expression in hepatocytes suppressed STAT1 and downstream IRF-1/NF-κB/CIITA/iNOS/chemokine expression and reduced pro-apoptotic markers, restoring cell viability.","evidence":"Stable TgIST transfection of Hepa-1c1c7 cells, western blot, RT-PCR, and flow cytometry for apoptosis markers","pmids":["38443768"],"confidence":"Medium","gaps":["Heterologous expression outside the parasite context","No mechanistic dissection of how STAT1 protein levels fall"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2026,"claim":"Beyond IFN suppression, IST was placed within a broader effector network; it is one of eight MYR1-dependent dense granule effectors that additively activate non-canonical NF-κB signaling via TRAF3 depletion, NIK stabilization, and p100 processing, with no single effector solely responsible.","evidence":"Combinatorial KO panel, nuclear fractionation for RelB/p52, and western blot for NIK/p100/TRAF3 (preprint)","pmids":["41959509"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Direct molecular role of IST in NF-κB activation not isolated from the other effectors"],"attribution":[{"species":"Toxoplasma gondii","strain":"Type I"},{"species":"Toxoplasma gondii","strain":"Type II"}]},{"year":null,"claim":"How the DNA-bound TgIST-STAT1 complex physically recruits the NuRD repressor complex, and how TgIST contributes to broader effector networks such as non-canonical NF-κB activation, remain to be defined structurally and functionally.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of the TgIST-STAT1-NuRD bridging interaction","Individual mechanistic contribution of IST within multi-effector networks not isolated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Mi-2/NuRD nucleosome remodeling and deacetylase complex (recruited by TgIST)","TgIST-phosphorylated STAT1 dimer/tetramer complex on promoter DNA"],"partners":["STAT1 (PHOSPHORYLATED DIMERS AND TETRAMERS; SH2 DOMAIN GROOVE AND N-TERMINAL DOMAIN)","STAT2 (TYPE I IFN SIGNALING)","MI-2/NURD REPRESSOR COMPLEX","MYR1 TRANSLOCON (EXPORT DEPENDENCY)","TGNSM (COOPERATING BRADYZOITE EFFECTOR)"],"other_free_text":["Secreted intrinsically disordered dense granule protein whose repeat region folds into a helix upon STAT1 binding [#3].","Functions in both tachyzoite and bradyzoite stages [#7].","Conserved across all three T. gondii strain types [#1]; T. gondii ortholog more potent than the Hammondia hammondi ortholog [#8].","Represses IFN-inducible genes including IDO1, PKR, MLKL, CIITA/MHC class II, iNOS, and CXCL9/10/11 [#5, #6, #10]."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"27503074","id":"PMC_27503074","title":"Toxoplasma gondii TgIST co-opts host chromatin repressors dampening STAT1-dependent gene regulation and IFN-γ-mediated host defenses.","date":"2016","source":"The Journal of experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27503074","citation_count":153,"is_preprint":false},{"pmid":"27414498","id":"PMC_27414498","title":"Toxoplasma Effector Recruits the Mi-2/NuRD Complex to Repress STAT1 Transcription and Block IFN-γ-Dependent Gene Expression.","date":"2016","source":"Cell host & microbe","url":"https://pubmed.ncbi.nlm.nih.gov/27414498","citation_count":145,"is_preprint":false},{"pmid":"34043960","id":"PMC_34043960","title":"Toxoplasma gondii secreted effectors co-opt host repressor complexes to inhibit necroptosis.","date":"2021","source":"Cell host & microbe","url":"https://pubmed.ncbi.nlm.nih.gov/34043960","citation_count":68,"is_preprint":false},{"pmid":"31413201","id":"PMC_31413201","title":"Toxoplasma gondii effector TgIST blocks type I interferon signaling to promote infection.","date":"2019","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/31413201","citation_count":63,"is_preprint":false},{"pmid":"24478085","id":"PMC_24478085","title":"Toxoplasma gondii Inhibits gamma interferon (IFN-γ)- and IFN-β-induced host cell STAT1 transcriptional activity by increasing the association of STAT1 with DNA.","date":"2013","source":"Infection and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/24478085","citation_count":59,"is_preprint":false},{"pmid":"22275866","id":"PMC_22275866","title":"Impaired chromatin remodelling at STAT1-regulated promoters leads to global unresponsiveness of Toxoplasma gondii-infected macrophages to IFN-γ.","date":"2012","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/22275866","citation_count":59,"is_preprint":false},{"pmid":"30283439","id":"PMC_30283439","title":"Toxoplasma Effector TgIST Targets Host IDO1 to Antagonize the IFN-γ-Induced Anti-parasitic Response in Human Cells.","date":"2018","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/30283439","citation_count":33,"is_preprint":false},{"pmid":"35831295","id":"PMC_35831295","title":"The intrinsically disordered protein TgIST from Toxoplasma gondii inhibits STAT1 signaling by blocking cofactor recruitment.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/35831295","citation_count":30,"is_preprint":false},{"pmid":"30177926","id":"PMC_30177926","title":"Inhibition of Nitric Oxide Production in Activated Macrophages Caused by Toxoplasma gondii Infection Occurs by Distinct Mechanisms in Different Mouse Macrophage Cell Lines.","date":"2018","source":"Frontiers in microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/30177926","citation_count":26,"is_preprint":false},{"pmid":"34921775","id":"PMC_34921775","title":"Transcriptional modification of host cells harboring Toxoplasma gondii bradyzoites prevents IFN gamma-mediated cell death.","date":"2021","source":"Cell host & microbe","url":"https://pubmed.ncbi.nlm.nih.gov/34921775","citation_count":23,"is_preprint":false},{"pmid":"33072127","id":"PMC_33072127","title":"Epigenetic Control of IFN-γ Host Responses During Infection With Toxoplasma gondii.","date":"2020","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33072127","citation_count":17,"is_preprint":false},{"pmid":"31545817","id":"PMC_31545817","title":"Regulation of NF-κB- and STAT1-mediated plasmacytoid dendritic cell functions by A20.","date":"2019","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/31545817","citation_count":11,"is_preprint":false},{"pmid":"19488417","id":"PMC_19488417","title":"IL-4 independent nuclear translocalization of STAT6 in HeLa cells by entry of Toxoplasma gondii.","date":"2009","source":"The Korean journal of parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/19488417","citation_count":11,"is_preprint":false},{"pmid":"31404885","id":"PMC_31404885","title":"Establishment of BV2 microglia polarization model and its effect on Toxoplasma gondii proliferation.","date":"2019","source":"Research in veterinary science","url":"https://pubmed.ncbi.nlm.nih.gov/31404885","citation_count":10,"is_preprint":false},{"pmid":"39597646","id":"PMC_39597646","title":"IL-36 Gamma: A Novel Adjuvant Cytokine Enhancing Protective Immunity Induced by DNA Immunization with TGIST and TGNSM Against Toxoplasma gondii Infection in Mice.","date":"2024","source":"Microorganisms","url":"https://pubmed.ncbi.nlm.nih.gov/39597646","citation_count":8,"is_preprint":false},{"pmid":"39292011","id":"PMC_39292011","title":"A combination of four Toxoplasma gondii nuclear-targeted effectors protects against interferon gamma-driven human host cell death.","date":"2024","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/39292011","citation_count":8,"is_preprint":false},{"pmid":"12953847","id":"PMC_12953847","title":"Pathogenicity of Toxoplasma gondii through B-2 cell-mediated downregulation of host defense responses.","date":"2003","source":"Microbiology and immunology","url":"https://pubmed.ncbi.nlm.nih.gov/12953847","citation_count":8,"is_preprint":false},{"pmid":"32574210","id":"PMC_32574210","title":"Head-to-head comparisons of Toxoplasma gondii and its near relative Hammondia hammondi reveal dramatic differences in the host response and effectors with species-specific functions.","date":"2020","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/32574210","citation_count":7,"is_preprint":false},{"pmid":"37205102","id":"PMC_37205102","title":"Type I and III interferons shape the retinal cytokine network and barrier function in an in vitro model of ocular toxoplasmosis.","date":"2023","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/37205102","citation_count":6,"is_preprint":false},{"pmid":"26951976","id":"PMC_26951976","title":"Afatinib Reduces STAT6 Signaling of Host ARPE-19 Cells Infected with Toxoplasma gondii.","date":"2016","source":"The Korean journal of parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/26951976","citation_count":6,"is_preprint":false},{"pmid":"37559725","id":"PMC_37559725","title":"T cell intrinsic STAT1 signaling prevents aberrant Th1 responses during acute toxoplasmosis.","date":"2023","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/37559725","citation_count":5,"is_preprint":false},{"pmid":"25836617","id":"PMC_25836617","title":"Infection-stimulated anemia results primarily from interferon gamma-dependent, signal transducer and activator of transcription 1-independent red cell loss.","date":"2015","source":"Chinese medical journal","url":"https://pubmed.ncbi.nlm.nih.gov/25836617","citation_count":5,"is_preprint":false},{"pmid":"38443768","id":"PMC_38443768","title":"Toxoplasma gondii IST suppresses inflammatory and apoptotic responses by inhibiting STAT1-mediated signaling in IFN-γ/TNF-α-stimulated hepatocytes.","date":"2024","source":"Parasites, hosts and diseases","url":"https://pubmed.ncbi.nlm.nih.gov/38443768","citation_count":4,"is_preprint":false},{"pmid":"29968354","id":"PMC_29968354","title":"Toxoplasma gondii stabilises tetrameric complexes of tyrosine-phosphorylated signal transducer and activator of transcription-1 and leads to its sustained and promiscuous DNA binding.","date":"2018","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/29968354","citation_count":4,"is_preprint":false},{"pmid":"38713713","id":"PMC_38713713","title":"Fam96a is essential for the host control of Toxoplasma gondii infection by fine-tuning macrophage polarization via an iron-dependent mechanism.","date":"2024","source":"PLoS neglected tropical diseases","url":"https://pubmed.ncbi.nlm.nih.gov/38713713","citation_count":4,"is_preprint":false},{"pmid":"39453997","id":"PMC_39453997","title":"Toxoplasma gondii macrophage migration inhibitory factor shows anti-Mycobacterium tuberculosis potential via AZIN1/STAT1 interaction.","date":"2024","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/39453997","citation_count":2,"is_preprint":false},{"pmid":"26196960","id":"PMC_26196960","title":"Tuning up STAT1.","date":"2015","source":"PLoS biology","url":"https://pubmed.ncbi.nlm.nih.gov/26196960","citation_count":1,"is_preprint":false},{"pmid":"38234811","id":"PMC_38234811","title":"A Combination of Four Nuclear Targeted Effectors Protects Toxoplasma Against Interferon Gamma Driven Human Host Cell Death During Acute Infection.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38234811","citation_count":1,"is_preprint":false},{"pmid":"38932306","id":"PMC_38932306","title":"Protective Efficacy of a Novel DNA Vaccine with a CL264 Molecular Adjuvant against Toxoplasma gondii in a Murine Model.","date":"2024","source":"Vaccines","url":"https://pubmed.ncbi.nlm.nih.gov/38932306","citation_count":0,"is_preprint":false},{"pmid":"41959509","id":"PMC_41959509","title":"A Suite of Eight Toxoplasma gondii Effectors Cooperates to Activate the Non-canonical NF-κB Pathway.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41959509","citation_count":0,"is_preprint":false},{"pmid":"26422772","id":"PMC_26422772","title":"Releasing the Brake on IFN-γ Signaling on Infection.","date":"2015","source":"Trends in parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/26422772","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18096,"output_tokens":4331,"usd":0.059626,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10783,"output_tokens":5883,"usd":0.100495,"stage2_stop_reason":"end_turn"},"total_usd":0.160121,"stage1_batch_id":"msgbatch_01TEPNZ4MCzJ7xtsNwosiDRk","stage2_batch_id":"msgbatch_01FQShM7n1sfCr4pWTDShmki","note":"batch pricing = 50% of standard","corrective_rerun":"2026-09-10 wrong-gene rerun (round-4 rules)","corrective_reason":"paper list: removed papers about other genes"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"TgIST (T. gondii inhibitor of STAT1 transcriptional activity) is secreted by intracellular parasites, traffics to the host cell nucleus, sequesters STAT1 on IFN-γ-responsive loci, and recruits the NuRD (nucleosome remodeling deacetylase) transcriptional repressor complex to establish non-permissive chromatin and block STAT1-dependent gene expression.\",\n      \"method\": \"Co-immunoprecipitation, nuclear fractionation, chromatin immunoprecipitation, genetic deletion of TgIST (ΔTgist parasites) with phenotypic rescue, live imaging of nuclear trafficking\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ChIP, subcellular fractionation, and clean KO with defined immune phenotype; independently replicated in a concurrent paper (PMID:27414498)\",\n      \"pmids\": [\"27503074\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TgIST translocates to the host cell nucleus and recruits the Mi-2/NuRD (nucleosome remodeling and deacetylase) complex to STAT1-bound promoters, resulting in altered chromatin and blocked IFN-γ-dependent transcription; TgIST is conserved across all three T. gondii strains, and its deletion increases parasite clearance in IFN-γ-activated cells and reduces virulence in mice.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, genetic deletion (ΔTgist), mouse virulence assays, IFN-γ receptor-deficient mouse rescue experiments\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, ChIP, KO, in vivo rescue), independently replicated by Gay et al. 2016 (PMID:27503074)\",\n      \"pmids\": [\"27414498\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type III\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TgIST blocks type I IFN (IFN-β) signaling in addition to IFN-γ, inhibiting STAT1/STAT2-mediated transcription in infected cells; ΔTgist parasites show increased susceptibility to IFN-β-activated macrophage killing, and reduced virulence of ΔTgist parasites is restored in Ifnar1-/- mice.\",\n      \"method\": \"Genetic deletion (ΔTgist), IFN-β stimulation assays, murine infection models with Ifnar1-/- mice, macrophage killing assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined phenotype, in vivo genetic rescue with receptor-deficient mice, multiple cell types tested\",\n      \"pmids\": [\"31413201\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TgIST is an intrinsically disordered protein; its internal repeat region adopts a helical conformation upon binding to phosphorylated STAT1 dimers at a groove formed by two loops in the STAT1 SH2 domains that become exposed upon dimerization, and this binding prevents recruitment of co-transcriptional activators without displacing STAT1 from DNA.\",\n      \"method\": \"Structural analysis (X-ray crystallography), biochemical binding assays, site-directed mutagenesis of TgIST repeat region and STAT1 SH2 domain, cellular reporter assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis, biochemical reconstitution, and cellular validation in a single rigorous study\",\n      \"pmids\": [\"35831295\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TgIST binds more efficiently to STAT1 tetramers than dimers; binding requires the N-terminal domain of STAT1 (N-terminal deletion abrogates binding) and the ability of STAT1 to form tetramers (STAT1F77A substitution that prevents tetramerization abolishes TgIST binding). TgIST binding increases STAT1 affinity for DNA consensus sequences and enables binding to non-consensus sequences, retaining STAT1 in a phosphorylated, DNA-bound nuclear state.\",\n      \"method\": \"Co-immunoprecipitation with STAT1 deletion/point mutants, EMSA (electrophoretic mobility shift assay), nuclear retention/fractionation assays\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (Co-IP, EMSA, mutagenesis) in a single lab establishing structural requirements for TgIST-STAT1 interaction\",\n      \"pmids\": [\"29968354\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TgIST inhibits IFN-γ-induced IDO1 (indoleamine 2,3-dioxygenase 1) mRNA expression in human cells, thereby antagonizing the tryptophan-degradation-dependent anti-parasitic response; IDO1 but not IDO2 is required for IFN-γ-induced cell-autonomous immunity to T. gondii in human cells.\",\n      \"method\": \"TgIST-deficient parasite infection, RT-PCR/qPCR for IDO1 mRNA, siRNA knockdown of IDO1/IDO2, parasite growth assays in human cell lines\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean functional readout with KO parasites and siRNA, single lab, limited mechanistic depth on how TgIST suppresses IDO1 transcription\",\n      \"pmids\": [\"30283439\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TgIST acts together with the bradyzoite-stage effector TgNSM (which targets the NCoR/SMRT repressor complex) to block IFN-driven expression of PKR and MLKL, thereby preventing host cell necroptotic death and protecting the parasite's intracellular niche.\",\n      \"method\": \"Genetic deletion of TgIST and TgNSM individually and in combination, IFN stimulation assays, necroptosis readouts (MLKL phosphorylation, cell death assays), Co-IP of TgNSM with NCoR/SMRT\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — combinatorial KO analysis with defined molecular pathway (PKR/MLKL necroptosis axis), orthogonal cell death and gene expression assays\",\n      \"pmids\": [\"34043960\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Bradyzoite-stage T. gondii exports IST in a MYR1-dependent manner to suppress IFN-γ signaling in host cells; loss of IST in bradyzoites impairs suppression of IFNγ signaling and reduces protection of host cells from IFNγ-mediated cell death.\",\n      \"method\": \"Genetic deletion of IST and MYR1 in bradyzoite-stage parasites, transcriptomic analysis, IFN signaling reporter assays, cell death assays\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean stage-specific KO with multiple orthogonal readouts (transcriptomics, cell death), demonstrates functional conservation in bradyzoite stage\",\n      \"pmids\": [\"34921775\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"T. gondii IST suppresses inflammatory responses to Hammondia hammondi infection when co-infecting cells; the H. hammondi IST ortholog shows reduced functionality compared to T. gondii IST, consistent with the more vigorous host response to H. hammondi infection.\",\n      \"method\": \"Co-infection experiments, conditioned media transfer, transcriptomic analysis, H. hammondi IST functional comparison with T. gondii IST\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional comparison of orthologs with transcriptomic readout, single lab, limited mechanistic depth on IST domain function differences\",\n      \"pmids\": [\"32574210\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Hammondia hammondi\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TgIST is one of four nuclear-targeted dense granule effectors (along with GRA16, GRA24, GRA28) necessary for a complete block of IFNγ response in human cells; loss of all four leads to parasite premature egress and host cell death specifically in human (not murine) cells stimulated with IFNγ post-infection.\",\n      \"method\": \"Genome-wide loss-of-function screens in IFNγ-primed human fibroblasts, combinatorial KO parasites, cell death and egress assays in human vs. murine cells\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide screen validated by combinatorial KOs with defined mechanistic phenotype, species-specific functional distinction established\",\n      \"pmids\": [\"39292011\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"TgIST suppresses STAT1 expression and downstream signaling (IRF-1, NF-κB, COX2, CIITA, iNOS, chemokines CXCL9/10/11) in hepatocytes stimulated with IFN-γ/TNF-α, and reduces expression of pro-apoptotic markers (Caspase3/8/9, P53, BAX), restoring cell viability.\",\n      \"method\": \"Stable transfection of hepatocyte cell line (Hepa-1c1c7) with TgIST, western blot, RT-PCR, flow cytometry for apoptosis markers\",\n      \"journal\": \"Parasites, hosts and diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — heterologous expression system (no parasite), single lab, multiple readouts but no direct mechanistic dissection of how TgIST reduces STAT1 protein levels\",\n      \"pmids\": [\"38443768\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"T. gondii infection (all three strain types) inhibits STAT1-mediated transcription by preventing STAT1 dissociation from DNA, thereby blocking its recycling for further rounds of transcriptional activation; this leads to increased and sustained STAT1-chromatin association at IFN-γ-responsive promoters. The effector is not derived from rhoptries, as secretion without full invasion is insufficient to block STAT1.\",\n      \"method\": \"ChIP assay, STAT1-DNA binding assays, rhoptry injection experiments without full parasite invasion, histone deacetylase inhibitor treatment\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and binding assays across multiple strain types, mechanistic exclusion of rhoptry origin; predates TgIST identification but establishes the STAT1 retention mechanism later attributed to TgIST\",\n      \"pmids\": [\"24478085\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type III\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"T. gondii-infected macrophages cannot recruit BRG-1 or acetylate histones at IFN-γ-regulated promoters (CIITA pIV), and cannot recruit non-muscle actin to IFN-γ-responsive DNA sequences, leading to global unresponsiveness to IFN-γ; HDAC inhibitors restore IFN-γ responsiveness, implicating chromatin remodeling as the primary mechanism.\",\n      \"method\": \"Genome-wide transcriptomics, ChIP for BRG-1 and histone acetylation, mass spectrometry of GAS oligonucleotide-bound protein complexes, HDAC inhibitor rescue\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods including MS identification of missing chromatin factors and pharmacological rescue; predates TgIST identification but mechanistically characterizes the chromatin remodeling block\",\n      \"pmids\": [\"22275866\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"IST is one of eight MYR1-dependent dense granule effectors (IST, NSM, HCE1/TEEGR, GRA16, GRA18, GRA24, GRA28, GRA84) that collectively and additively activate the non-canonical NF-κB pathway (RelB/p52) by driving TRAF3 depletion, NIK stabilization, and p100 processing; no single effector is solely responsible.\",\n      \"method\": \"Combinatorial KO parasite panel, nuclear fractionation for RelB/p52, western blot for NIK/p100/TRAF3, MYR1-dependent export assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — combinatorial KO with defined molecular pathway readouts, preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [\"41959509\"],\n      \"is_preprint\": true,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}]\n    }\n  ],\n  \"current_model\": \"TgIST is a secreted, intrinsically disordered dense granule protein that is exported via the MYR1 translocon into the host cell nucleus, where it binds phosphorylated STAT1 dimers and tetramers at a groove on the STAT1 SH2 domain exposed upon dimerization; this interaction locks STAT1 in a DNA-bound, non-recycling state, recruits the Mi-2/NuRD chromatin repressor complex to STAT1-occupied promoters, blocks co-activator recruitment, and thereby suppresses IFN-γ- and IFN-β-stimulated gene expression (including IDO1, PKR, MLKL, iNOS, and MHC class II genes) in both tachyzoite and bradyzoite stages to evade host immune defenses.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgIST is a secreted dense granule effector of Toxoplasma gondii that traffics from intracellular parasites into the host cell nucleus, where it functions as a master antagonist of interferon-driven transcription to enable immune evasion [#0, #1]. Within the nucleus it sequesters phosphorylated STAT1 on IFN-\\u03b3-responsive promoters and recruits the Mi-2/NuRD nucleosome-remodeling and deacetylase repressor complex, establishing a non-permissive chromatin state that blocks STAT1-dependent gene expression [#0, #1]. This activity extends beyond IFN-\\u03b3: TgIST also suppresses type I IFN (IFN-\\u03b2) signaling through STAT1/STAT2, and \\u0394Tgist parasites show heightened susceptibility to both IFN-\\u03b3- and IFN-\\u03b2-activated killing, with virulence restored in Ifnar1-/- mice [#2]. Mechanistically, TgIST is an intrinsically disordered protein whose internal repeat region folds into a helix upon engaging a groove on the STAT1 SH2 domain exposed by dimerization; it binds phosphorylated STAT1 dimers and, more avidly, tetramers, locking STAT1 in a DNA-bound, non-recycling state and blocking co-activator recruitment without displacing STAT1 from DNA [#3, #4]. Functionally, TgIST represses effector genes including IDO1, PKR, MLKL, CIITA, and iNOS, thereby preventing tryptophan-starvation immunity and necroptotic host cell death and preserving the parasite's replicative niche in both tachyzoite and bradyzoite stages [#5, #6, #7]. TgIST operates as one of several nuclear-targeted, MYR1-dependent dense granule effectors that together are required for complete blockade of the human IFN-\\u03b3 response [#7, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Before the effector was known, the question was how T. gondii silences IFN-\\u03b3 responses; infection was shown to prevent chromatin remodeling at IFN-\\u03b3 promoters, establishing that the block operates at the level of chromatin rather than upstream signaling.\",\n      \"evidence\": \"Transcriptomics, ChIP for BRG-1/histone acetylation, MS of GAS-bound complexes, and HDAC inhibitor rescue in infected macrophages\",\n      \"pmids\": [\"22275866\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not identify the parasite effector responsible\", \"Mechanism of NuRD/repressor recruitment not defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"It was unknown how infection sustains STAT1 occupancy; ChIP and binding assays showed infection prevents STAT1 dissociation from DNA, blocking its recycling and establishing the STAT1-retention mechanism, while excluding rhoptries as the source of the effector.\",\n      \"evidence\": \"ChIP, STAT1-DNA binding assays, rhoptry injection without full invasion, and HDAC inhibitor treatment across three strain types\",\n      \"pmids\": [\"24478085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Effector identity still unknown\", \"Did not distinguish dense granule origin directly\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type III\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Two concurrent studies identified TgIST as the secreted, nucleus-trafficking effector that sequesters STAT1 on IFN-\\u03b3 loci and recruits the Mi-2/NuRD complex, directly linking a defined parasite protein to the chromatin-level block and demonstrating its role in virulence.\",\n      \"evidence\": \"Co-IP, ChIP, nuclear fractionation, \\u0394Tgist deletion with phenotypic rescue, and mouse virulence/IFN-\\u03b3 receptor-deficient rescue experiments\",\n      \"pmids\": [\"27503074\", \"27414498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of STAT1 binding not resolved\", \"Whether other IFN pathways are targeted unaddressed\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type III\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The structural requirements of the STAT1 interaction were unknown; TgIST was shown to bind STAT1 tetramers more efficiently than dimers, require the STAT1 N-terminal domain and tetramerization, and increase STAT1 DNA affinity, explaining how STAT1 is retained in a phosphorylated DNA-bound state.\",\n      \"evidence\": \"Co-IP with STAT1 deletion/point mutants (F77A), EMSA, and nuclear retention assays\",\n      \"pmids\": [\"29968354\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution binding interface not defined\", \"How binding excludes co-activators unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The downstream effector genes controlled were unclear; TgIST was shown to suppress IFN-\\u03b3-induced IDO1 in human cells, connecting STAT1 antagonism to blockade of tryptophan-starvation cell-autonomous immunity.\",\n      \"evidence\": \"\\u0394Tgist infection, qPCR for IDO1, siRNA of IDO1/IDO2, and parasite growth assays in human cells\",\n      \"pmids\": [\"30283439\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Limited mechanistic depth on IDO1 transcriptional suppression\", \"Restricted to human cell context\"]\n      ,\"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Whether TgIST acts only on IFN-\\u03b3 was open; it was shown to also block type I IFN (IFN-\\u03b2) STAT1/STAT2 signaling, broadening its role to both interferon arms of host defense.\",\n      \"evidence\": \"\\u0394Tgist deletion, IFN-\\u03b2 stimulation, macrophage killing assays, and Ifnar1-/- mouse rescue\",\n      \"pmids\": [\"31413201\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether STAT2-specific contacts differ from STAT1 not defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The evolutionary tuning of IST activity was addressed by comparing orthologs; T. gondii IST suppressed inflammatory responses more effectively than the Hammondia hammondi ortholog, correlating effector potency with the divergent host responses to each parasite.\",\n      \"evidence\": \"Co-infection, conditioned media transfer, transcriptomics, and functional comparison of T. gondii vs H. hammondi IST\",\n      \"pmids\": [\"32574210\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Domain-level basis for functional divergence not mapped\", \"Single-lab comparison\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}, {\"species\": \"Hammondia hammondi\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"How the parasite prevents host cell death was unclear; TgIST was shown to act with the bradyzoite effector TgNSM to block IFN-driven PKR and MLKL expression, preventing necroptosis and protecting the intracellular niche.\",\n      \"evidence\": \"Individual and combinatorial \\u0394Tgist/\\u0394Tgnsm deletion, MLKL phosphorylation and cell death readouts, and Co-IP of TgNSM with NCoR/SMRT\",\n      \"pmids\": [\"34043960\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct role of TgIST versus TgNSM at PKR/MLKL promoters not separated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Whether IST functions in the chronic stage was unknown; bradyzoites were shown to export IST in a MYR1-dependent manner to suppress IFN-\\u03b3 signaling and protect host cells from IFN-\\u03b3-mediated death, establishing stage-independent function and defining the export route.\",\n      \"evidence\": \"Stage-specific \\u0394IST and \\u0394MYR1 bradyzoite deletion, transcriptomics, IFN reporter and cell death assays\",\n      \"pmids\": [\"34921775\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular details of MYR1-dependent translocation of IST not resolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The atomic mechanism of STAT1 inhibition was resolved; TgIST is intrinsically disordered and its repeat region folds into a helix upon binding a dimerization-exposed groove on the STAT1 SH2 domain, blocking co-activator recruitment without displacing STAT1 from DNA.\",\n      \"evidence\": \"X-ray crystallography, biochemical binding assays, mutagenesis of the TgIST repeat and STAT1 SH2 domain, and cellular reporter assays\",\n      \"pmids\": [\"35831295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the DNA-bound complex physically recruits NuRD not structurally defined\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The sufficiency of TgIST alone was tested; genome-wide screens showed it is one of four nuclear-targeted dense granule effectors (with GRA16, GRA24, GRA28) collectively required for complete IFN-\\u03b3 blockade, with loss of all four causing premature egress specifically in human cells.\",\n      \"evidence\": \"Genome-wide loss-of-function screens in IFN\\u03b3-primed human fibroblasts, combinatorial KOs, and egress/cell death assays in human vs murine cells\",\n      \"pmids\": [\"39292011\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual contribution of TgIST within the four-effector set not quantified\", \"Basis of human- versus murine-cell specificity unresolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Whether TgIST reduces STAT1 protein levels was tested in a heterologous system; stable TgIST expression in hepatocytes suppressed STAT1 and downstream IRF-1/NF-\\u03baB/CIITA/iNOS/chemokine expression and reduced pro-apoptotic markers, restoring cell viability.\",\n      \"evidence\": \"Stable TgIST transfection of Hepa-1c1c7 cells, western blot, RT-PCR, and flow cytometry for apoptosis markers\",\n      \"pmids\": [\"38443768\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Heterologous expression outside the parasite context\", \"No mechanistic dissection of how STAT1 protein levels fall\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Beyond IFN suppression, IST was placed within a broader effector network; it is one of eight MYR1-dependent dense granule effectors that additively activate non-canonical NF-\\u03baB signaling via TRAF3 depletion, NIK stabilization, and p100 processing, with no single effector solely responsible.\",\n      \"evidence\": \"Combinatorial KO panel, nuclear fractionation for RelB/p52, and western blot for NIK/p100/TRAF3 (preprint)\",\n      \"pmids\": [\"41959509\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Direct molecular role of IST in NF-\\u03baB activation not isolated from the other effectors\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the DNA-bound TgIST-STAT1 complex physically recruits the NuRD repressor complex, and how TgIST contributes to broader effector networks such as non-canonical NF-\\u03baB activation, remain to be defined structurally and functionally.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the TgIST-STAT1-NuRD bridging interaction\", \"Individual mechanistic contribution of IST within multi-effector networks not isolated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0019904\", \"supporting_discovery_ids\": [3, 4], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0000976\", \"supporting_discovery_ids\": [4, 11], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0140416\", \"supporting_discovery_ids\": [0, 1, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0044222\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0033655\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0060333\", \"supporting_discovery_ids\": [0, 1, 11, 12], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0060337\", \"supporting_discovery_ids\": [2], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0070266\", \"supporting_discovery_ids\": [6], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0038061\", \"supporting_discovery_ids\": [13], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"Type I\"}, {\"species\": \"Toxoplasma gondii\", \"strain\": \"Type II\"}]}\n    ],\n    \"complexes\": [\n      \"Mi-2/NuRD nucleosome remodeling and deacetylase complex (recruited by TgIST)\",\n      \"TgIST-phosphorylated STAT1 dimer/tetramer complex on promoter DNA\"\n    ],\n    \"partners\": [\n      \"STAT1 (phosphorylated dimers and tetramers; SH2 domain groove and N-terminal domain)\",\n      \"STAT2 (type I IFN signaling)\",\n      \"Mi-2/NuRD repressor complex\",\n      \"MYR1 translocon (export dependency)\",\n      \"TgNSM (cooperating bradyzoite effector)\"\n    ],\n    \"other_free_text\": [\n      \"Secreted intrinsically disordered dense granule protein whose repeat region folds into a helix upon STAT1 binding [#3].\",\n      \"Functions in both tachyzoite and bradyzoite stages [#7].\",\n      \"Conserved across all three T. gondii strain types [#1]; T. gondii ortholog more potent than the Hammondia hammondi ortholog [#8].\",\n      \"Represses IFN-inducible genes including IDO1, PKR, MLKL, CIITA/MHC class II, iNOS, and CXCL9/10/11 [#5, #6, #10].\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_240060","name":"IST","product":"inhibitor of STAT1 transcription","uniprot_acc":"A0A125YYK6","chromosome":"TGME49_chrVI","start_pos":1035064},{"strain":"GT1","gene_id":"TGGT1_240060","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"TGGT1_chrVI","start_pos":1027949},{"strain":"RH88","gene_id":"TGRH88_087790","name":null,"product":"Inhibitor of STAT1-dependent transcription TgIST","uniprot_acc":null,"chromosome":"CM023087","start_pos":2665923},{"strain":"VEG","gene_id":"TGVEG_240060","name":null,"product":"hypothetical protein","uniprot_acc":"B6KFA4","chromosome":"TGVEG_chrVI","start_pos":1048813}]}