{"gene":"TG_224850","gene_symbol":"PABPC","run_date":"2026-09-08T11:06:43","timeline":{"discoveries":[{"year":2020,"finding":"TgPABPC (poly(A) binding protein cytoplasmic) localizes to the cytoplasm of Toxoplasma gondii and colocalizes with mRNA granules (mRNP granules), establishing it as a cellular marker for these structures.","method":"Subcellular localization by direct imaging/fractionation; colocalization with mRNP granule markers","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiment with functional link (mRNP granule marker), single lab, single study","pmids":["33383066"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"finding":"mRNP granule formation (tracked via TgPABPC) occurs in a two-phase process: rapid granule formation in the cytosol prior to host cell lysis, followed by reduction of granule load within 10 min post-egress; formation is independent of polymerized microtubules and granules are distributed stochastically.","method":"Live imaging of TgPABPC-marked granules during Ca2+-ionophore-induced egress; microtubule depolymerization assay","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization and time-course experiment with mechanistic detail, single lab, multiple conditions tested","pmids":["33383066"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"finding":"Salubrinal (an eIF2α phosphatase inhibitor that induces translational repression) induces TgPABPC-positive mRNP granule formation in tachyzoites but not in bradyzoites, indicating that mRNP granule formation is not a universal response to translational repression and is stage-specific; nutrient starvation and pH stress did not induce granule formation.","method":"Pharmacological treatment (salubrinal, nutrient deprivation, pH stress) followed by imaging of TgPABPC-marked granules in tachyzoites and bradyzoites","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — defined cellular response using TgPABPC as readout across multiple conditions and life stages, single lab","pmids":["33383066"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgPABPC is a cytoplasmic poly(A) binding protein in Toxoplasma gondii that localizes to and marks mRNP granules; these granules form rapidly prior to host-cell lysis during egress in a microtubule-independent manner and their formation is induced by salubrinal-driven translational state changes in tachyzoites but not bradyzoites, suggesting TgPABPC-associated granule assembly reflects stage-specific responses to shifts in translational activity rather than a universal stress response."},"narrative":{"mechanistic_narrative":"TgPABPC is a cytoplasmic poly(A) binding protein in Toxoplasma gondii that serves as a marker of mRNP (mRNA) granules, associating with these structures in the parasite cytoplasm [PMID:33383066]. Live imaging of TgPABPC-marked granules shows that granule assembly is a dynamic, two-phase process during egress: granules form rapidly in the cytosol prior to host-cell lysis and are then cleared within 10 minutes post-egress, with granule formation occurring independently of polymerized microtubules and distributed stochastically [PMID:33383066]. Granule assembly is stage-specific and coupled to translational state rather than being a universal stress response: the eIF2α phosphatase inhibitor salubrinal induces TgPABPC-positive granules in tachyzoites but not bradyzoites, while nutrient starvation and pH stress fail to trigger formation [PMID:33383066]. Beyond these localization and granule-dynamics observations, no biochemical characterization of TgPABPC's RNA-binding activity or interaction partners has been established in the available corpus.","teleology":[{"year":2020,"claim":"Establishing where TgPABPC resides addressed whether the protein could serve as a tractable marker for mRNP granules in Toxoplasma; it localized to the cytoplasm and colocalized with mRNP granules, defining it as a cellular marker for these structures.","evidence":"Subcellular localization by imaging/fractionation with colocalization to mRNP granule markers in Toxoplasma gondii","pmids":["33383066"],"confidence":"Medium","gaps":["No biochemical demonstration of poly(A)/RNA binding by TgPABPC","Granule composition and other constituents not defined","No interaction partners identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"claim":"It was unknown when and how mRNP granules assemble during the parasite lytic cycle; time-course live imaging revealed rapid pre-lysis cytosolic granule formation followed by clearance within 10 min post-egress, and depolymerization assays showed assembly does not require microtubules.","evidence":"Live imaging of TgPABPC-marked granules during Ca2+-ionophore-induced egress plus microtubule depolymerization assay","pmids":["33383066"],"confidence":"Medium","gaps":["Molecular trigger linking egress to granule assembly not identified","Functional consequence of granule formation for translation or egress not tested","Mechanism of granule clearance post-egress unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2020,"claim":"Whether granule formation is a generic stress response was unresolved; pharmacological probing showed salubrinal-driven translational repression induces TgPABPC granules in tachyzoites but not bradyzoites, and neither starvation nor pH stress induced them, establishing granule assembly as stage-specific and tied to translational state.","evidence":"Pharmacological treatment (salubrinal, nutrient deprivation, pH stress) with TgPABPC granule imaging across tachyzoites and bradyzoites","pmids":["33383066"],"confidence":"Medium","gaps":["Molecular basis of the tachyzoite-vs-bradyzoite difference not defined","Direct link between eIF2α phosphorylation status and granule assembly not biochemically confirmed","Whether granules represent stress granules, P-bodies, or a distinct compartment not resolved"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The molecular function of TgPABPC — its RNA-binding activity, protein partners, and the mechanistic role of the granules it marks in mRNA fate during egress and stage differentiation — remains uncharacterized.","evidence":"No further mechanistic evidence in the available corpus","pmids":[],"confidence":"Medium","gaps":["No demonstrated biochemical activity or substrate","No interaction partners or complex composition","No genetic loss-of-function phenotype for TgPABPC"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":[],"other_free_text":["Marks mRNP granules that assemble rapidly in the cytosol prior to host-cell lysis during egress and are cleared within ~10 min post-egress, independent of polymerized microtubules [#1].","Granule formation is stage-specific: induced by salubrinal (eIF2α phosphatase inhibitor) in tachyzoites but not bradyzoites, and not induced by nutrient starvation or pH stress [#2]."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"33383066","id":"PMC_33383066","title":"Formation of mRNP granules in Toxoplasma gondii during the lytic cycle.","date":"2020","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/33383066","citation_count":3,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":2939,"output_tokens":909,"usd":0.011226,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5699,"output_tokens":1951,"usd":0.038635,"stage2_stop_reason":"end_turn"},"total_usd":0.049861,"stage1_batch_id":"msgbatch_01WokvBYTB6JLnYrpD4rXnyV","stage2_batch_id":"msgbatch_01M7hsQDvz6AqVC9DLVjQzzc","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2020,\n      \"finding\": \"TgPABPC (poly(A) binding protein cytoplasmic) localizes to the cytoplasm of Toxoplasma gondii and colocalizes with mRNA granules (mRNP granules), establishing it as a cellular marker for these structures.\",\n      \"method\": \"Subcellular localization by direct imaging/fractionation; colocalization with mRNP granule markers\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiment with functional link (mRNP granule marker), single lab, single study\",\n      \"pmids\": [\"33383066\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"mRNP granule formation (tracked via TgPABPC) occurs in a two-phase process: rapid granule formation in the cytosol prior to host cell lysis, followed by reduction of granule load within 10 min post-egress; formation is independent of polymerized microtubules and granules are distributed stochastically.\",\n      \"method\": \"Live imaging of TgPABPC-marked granules during Ca2+-ionophore-induced egress; microtubule depolymerization assay\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization and time-course experiment with mechanistic detail, single lab, multiple conditions tested\",\n      \"pmids\": [\"33383066\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Salubrinal (an eIF2α phosphatase inhibitor that induces translational repression) induces TgPABPC-positive mRNP granule formation in tachyzoites but not in bradyzoites, indicating that mRNP granule formation is not a universal response to translational repression and is stage-specific; nutrient starvation and pH stress did not induce granule formation.\",\n      \"method\": \"Pharmacological treatment (salubrinal, nutrient deprivation, pH stress) followed by imaging of TgPABPC-marked granules in tachyzoites and bradyzoites\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — defined cellular response using TgPABPC as readout across multiple conditions and life stages, single lab\",\n      \"pmids\": [\"33383066\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"TgPABPC is a cytoplasmic poly(A) binding protein in Toxoplasma gondii that localizes to and marks mRNP granules; these granules form rapidly prior to host-cell lysis during egress in a microtubule-independent manner and their formation is induced by salubrinal-driven translational state changes in tachyzoites but not bradyzoites, suggesting TgPABPC-associated granule assembly reflects stage-specific responses to shifts in translational activity rather than a universal stress response.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgPABPC is a cytoplasmic poly(A) binding protein in Toxoplasma gondii that serves as a marker of mRNP (mRNA) granules, associating with these structures in the parasite cytoplasm [#0]. Live imaging of TgPABPC-marked granules shows that granule assembly is a dynamic, two-phase process during egress: granules form rapidly in the cytosol prior to host-cell lysis and are then cleared within 10 minutes post-egress, with granule formation occurring independently of polymerized microtubules and distributed stochastically [#1]. Granule assembly is stage-specific and coupled to translational state rather than being a universal stress response: the eIF2\\u03b1 phosphatase inhibitor salubrinal induces TgPABPC-positive granules in tachyzoites but not bradyzoites, while nutrient starvation and pH stress fail to trigger formation [#2]. Beyond these localization and granule-dynamics observations, no biochemical characterization of TgPABPC's RNA-binding activity or interaction partners has been established in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2020,\n      \"claim\": \"Establishing where TgPABPC resides addressed whether the protein could serve as a tractable marker for mRNP granules in Toxoplasma; it localized to the cytoplasm and colocalized with mRNP granules, defining it as a cellular marker for these structures.\",\n      \"evidence\": \"Subcellular localization by imaging/fractionation with colocalization to mRNP granule markers in Toxoplasma gondii\",\n      \"pmids\": [\"33383066\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No biochemical demonstration of poly(A)/RNA binding by TgPABPC\", \"Granule composition and other constituents not defined\", \"No interaction partners identified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"It was unknown when and how mRNP granules assemble during the parasite lytic cycle; time-course live imaging revealed rapid pre-lysis cytosolic granule formation followed by clearance within 10 min post-egress, and depolymerization assays showed assembly does not require microtubules.\",\n      \"evidence\": \"Live imaging of TgPABPC-marked granules during Ca2+-ionophore-induced egress plus microtubule depolymerization assay\",\n      \"pmids\": [\"33383066\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular trigger linking egress to granule assembly not identified\", \"Functional consequence of granule formation for translation or egress not tested\", \"Mechanism of granule clearance post-egress unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Whether granule formation is a generic stress response was unresolved; pharmacological probing showed salubrinal-driven translational repression induces TgPABPC granules in tachyzoites but not bradyzoites, and neither starvation nor pH stress induced them, establishing granule assembly as stage-specific and tied to translational state.\",\n      \"evidence\": \"Pharmacological treatment (salubrinal, nutrient deprivation, pH stress) with TgPABPC granule imaging across tachyzoites and bradyzoites\",\n      \"pmids\": [\"33383066\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the tachyzoite-vs-bradyzoite difference not defined\", \"Direct link between eIF2\\u03b1 phosphorylation status and granule assembly not biochemically confirmed\", \"Whether granules represent stress granules, P-bodies, or a distinct compartment not resolved\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular function of TgPABPC \\u2014 its RNA-binding activity, protein partners, and the mechanistic role of the granules it marks in mRNA fate during egress and stage differentiation \\u2014 remains uncharacterized.\",\n      \"evidence\": \"No further mechanistic evidence in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No demonstrated biochemical activity or substrate\", \"No interaction partners or complex composition\", \"No genetic loss-of-function phenotype for TgPABPC\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0036464\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": [\n      \"Marks mRNP granules that assemble rapidly in the cytosol prior to host-cell lysis during egress and are cleared within ~10 min post-egress, independent of polymerized microtubules [#1].\",\n      \"Granule formation is stage-specific: induced by salubrinal (eIF2\\u03b1 phosphatase inhibitor) in tachyzoites but not bradyzoites, and not induced by nutrient starvation or pH stress [#2].\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_224850","name":"PABPC","product":"polyadenylate-binding protein PABC","uniprot_acc":"S8GEW7","chromosome":"TGME49_chrX","start_pos":2771766},{"strain":"GT1","gene_id":"TGGT1_224850","name":null,"product":"putative polyadenylate binding protein","uniprot_acc":null,"chromosome":"TGGT1_chrX","start_pos":2687512},{"strain":"RH88","gene_id":"TGRH88_044500","name":null,"product":"putative polyadenylate binding protein","uniprot_acc":null,"chromosome":"CM023091","start_pos":4790482},{"strain":"VEG","gene_id":"TGVEG_224850","name":null,"product":"putative polyadenylate binding protein","uniprot_acc":"A0A125YFB9","chromosome":"TGVEG_chrX","start_pos":2677455}]}