{"gene":"PF3D7_1361900","run_date":"2026-09-08T14:19:06","timeline":{"discoveries":[{"year":1993,"finding":"PCNA1 (PfPCNA1) is encoded by a single-exon gene on chromosome 13 of P. falciparum, predicting a 30,586 Da protein; antibodies against a PfPCNA1-GST fusion protein recognize a single ~32 kDa band in western blots, and expression is regulated during intraerythrocytic development, increasing dramatically in late trophozoites and persisting through schizogony.","method":"Western blot with anti-PfPCNA1-GST antiserum; northern blot; molecular characterization of coding sequence","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein detection by specific antibody plus stage-specific expression profiling, single lab with two orthogonal methods (western blot, northern blot)","pmids":["8095096"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1996,"finding":"The PCNA1 promoter contains a major transcription start site 960 bp upstream of the translational start and a minor site 40 bp further upstream; a 470 bp region encompassing these sites is essential for promoter activity, and a region 290–620 bp upstream of the transcriptional start is required for efficient promoter activity, as determined by transient transfection of luciferase reporter constructs.","method":"RNase protection assay; primer extension; transient transfection with luciferase reporter constructs containing serially deleted 5' flanking sequences","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RNase protection, primer extension, reporter assay with deletion mapping), single lab","pmids":["8946386"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1996,"finding":"PCNA1 protein and transcript accumulate at the trophozoite stage and persist in schizonts; nuclear run-on analysis shows that the PCNA1 promoter is active throughout the intraerythrocytic cycle (unlike PfDNA Pol delta, which is absent in rings), suggesting post-transcriptional regulation coordinates PCNA1 expression with DNA replication.","method":"Western blot of synchronised parasite extracts; northern blot; nuclear run-on transcription assay","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — nuclear run-on plus western/northern blot in synchronised parasites, single lab, two orthogonal methods","pmids":["8855554"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"PCNA1 (PfPCNA1) colocalizes with PfORC5 in distinct nuclear replication foci during early-to-mid trophozoite stage and co-immunoprecipitates with PfORC5 at this stage; the two proteins separate at the non-replicating late schizont stage. PfORC1 also colocalizes with PCNA1 at the onset of DNA replication. A putative PCNA-interacting protein (PIP) box in PfORC1 may mediate colocalization. The DNA replication inhibitor hydroxyurea disrupts ORC5/PCNA1 foci formation.","method":"Co-immunoprecipitation; immunofluorescence colocalization; hydroxyurea inhibitor treatment; bioinformatic identification of PIP box","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus immunofluorescence colocalization in synchronised parasites, single lab, two orthogonal methods","pmids":["18554328"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"The putative PIP (PCNA-interacting protein) motif in PfORC1 mediates direct physical interaction with PCNA1 in vitro and is functional in vivo in both yeast and P. falciparum, as shown by biochemical pull-down and yeast complementation.","method":"In vitro binding assay (biochemical interaction); yeast genetic complementation; domain deletion/mutation analysis","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro interaction assay plus yeast complementation, single lab, two orthogonal methods","pmids":["19633266"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"The 5' and 3' genetic elements of the PCNA1 (Pfpcna) locus control both the absolute level and temporal pattern of gene expression during the intraerythrocytic cycle; serial deletion of these elements and treatment with histone deacetylase inhibitors perturbed absolute expression but did not affect temporal control, supporting a model in which temporal regulation of PCNA1 (and potentially hundreds of other genes) is independent of histone deacetylase activity and of the flanking regulatory sequences tested.","method":"Bxb1 integrase-mediated site-specific integration of luciferase reporter with serial 5'/3' deletions; histone deacetylase inhibitor treatment; quantitative luciferase assay","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — integrated reporter system with systematic deletion analysis plus pharmacological perturbation, single lab, multiple constructs","pmids":["21354176"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"PCNA1 (PfPCNA1), but not PfPCNA2, functionally complements a ScPCNA mutant in yeast and forms distinct nuclear replication foci in P. falciparum parasites, establishing PCNA1 as the primary replicative PCNA. Both PfPCNA1 and PfPCNA2 accumulate significantly upon DNA damage induction, participating in an active DNA-damage-response (DDR) pathway. Regulation upon DNA damage occurs at the protein stability level rather than at the transcriptional level. Overexpression of PfPCNA1 confers a survival advantage in a genotoxic environment.","method":"Yeast complementation assay; immunofluorescence (replication foci); western blot of DNA-damage-induced parasites; quantitative RT-PCR (ruling out transcriptional regulation); parasite overexpression with genotoxic challenge","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — yeast complementation (Tier 1) combined with in-parasite foci imaging, transcription/protein-level dissection, and functional overexpression, multiple orthogonal methods in a single rigorous study","pmids":["26251451"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"PCNA1 (PfPCNA1) is phosphorylated in P. falciparum-infected erythrocytes; it localizes predominantly to the parasite cytoplasm but transiently shifts to the nucleus upon TNF stimulation, accompanied by dephosphorylation and rapid protein turnover. A triple serine-phosphorylated PCNA1 peptide was identified by mass spectrometry in a high-expressing strain. This response to TNF is part of an external sensing system in the parasite.","method":"2D gel electrophoresis followed by western blot; biochemical fractionation (cytoplasm vs. nucleus); high-resolution mass spectrometry of immune precipitants; real-time qRT-PCR","journal":"Malaria journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mass spectrometry identification of phosphopeptide plus biochemical fractionation showing subcellular redistribution, single lab, two orthogonal methods","pmids":["26893139"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Tyrosine 213 (Y213) of PCNA1 is required for nuclear retention and replication foci formation of PfPCNA1 in P. falciparum; a Y213F mutation causes functional loss in both yeast complementation and parasite assays. Serine 191 phosphorylation (reported in phospho-proteome data) was found not to be important for this nuclear localization function. The conserved tyrosine residue is linked to DNA replication and cell proliferation.","method":"Site-directed mutagenesis (Y213F, S191); immunofluorescence (nuclear localization and foci formation in parasite); yeast complementation assay","journal":"FEMS microbiology letters","confidence":"High","confidence_rationale":"Tier 1 / Moderate — site-directed mutagenesis with functional readout in two independent systems (yeast complementation + parasite immunofluorescence), rigorous controls distinguishing Y213 from S191","pmids":["30052905"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"PF3D7_1361900 (PCNA1) is the primary replicative proliferating cell nuclear antigen of P. falciparum: its promoter is constitutively active throughout the intraerythrocytic cycle with temporal protein accumulation regulated post-transcriptionally; PCNA1 forms distinct nuclear replication foci, physically interacts with PfORC1 (via a PIP-box interaction) and PfORC5 during S phase, functionally complements yeast PCNA, and its nuclear retention depends on conserved tyrosine 213 whose mutation abolishes foci formation and function in both yeast and parasite; additionally, PCNA1 undergoes serine phosphorylation and cytoplasm-to-nucleus redistribution in response to TNF signalling, and both PCNA1 and PCNA2 accumulate (regulated at protein stability rather than transcription level) in response to DNA damage, with PCNA1 overexpression conferring genotoxic resistance."},"narrative":{"mechanistic_narrative":"PF3D7_1361900 (PCNA1) is the primary replicative proliferating cell nuclear antigen of Plasmodium falciparum, coordinating DNA replication and the DNA-damage response during intraerythrocytic development [PMID:26251451]. It is encoded by a single-exon gene whose protein accumulates from the trophozoite stage and persists through schizogony; although its promoter is transcriptionally active throughout the intraerythrocytic cycle, its protein accumulation is coordinated post-transcriptionally with DNA replication [PMID:8095096, PMID:8855554]. During S phase PCNA1 assembles into distinct nuclear replication foci and physically engages the origin recognition complex, co-immunoprecipitating and colocalizing with PfORC5 and colocalizing with PfORC1 at replication onset via a PIP-box in PfORC1 that mediates direct binding, an interaction functional in both yeast and parasite [PMID:18554328, PMID:19633266]. PCNA1, but not the sibling PCNA2, complements a yeast PCNA mutant, confirming its role as the principal replicative clamp; both accumulate upon genotoxic stress through regulation of protein stability rather than transcription, and PCNA1 overexpression confers genotoxic resistance [PMID:26251451]. Nuclear retention and foci formation depend on the conserved tyrosine 213, whose mutation abolishes function in both yeast and parasite [PMID:30052905]. PCNA1 is also phosphorylated in infected erythrocytes and redistributes transiently from cytoplasm to nucleus upon TNF stimulation with accompanying dephosphorylation and turnover [PMID:26893139].","teleology":[{"year":1993,"claim":"Establishing that P. falciparum encodes a PCNA and expresses it in a replication-linked pattern was the first step toward defining the parasite's replicative machinery.","evidence":"molecular characterization of a single-exon chromosome-13 gene with specific antibody detection and stage-resolved northern/western blots","pmids":["8095096"],"confidence":"Medium","gaps":["Whether the detected protein functions as a replicative clamp not yet tested","Interaction partners unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1996,"claim":"Promoter mapping and run-on analysis addressed how PCNA1 expression is temporally coordinated, revealing constitutive transcription with the replication-coupled protein accumulation set post-transcriptionally.","evidence":"RNase protection/primer extension promoter mapping, luciferase reporter deletion analysis, and nuclear run-on transcription assays in synchronised parasites","pmids":["8946386","8855554"],"confidence":"Medium","gaps":["Mechanism of post-transcriptional coordination unidentified","Trans-acting factors on the promoter not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"claim":"Whether PCNA1 physically couples to replication origins was answered by demonstrating S-phase-specific association with the origin recognition complex.","evidence":"co-immunoprecipitation and immunofluorescence colocalization with PfORC5/PfORC1 in synchronised parasites, disrupted by hydroxyurea","pmids":["18554328"],"confidence":"Medium","gaps":["Directness of ORC5 interaction not established biochemically","Functional consequence of the interaction untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"The mechanism of PCNA1 recruitment to origins was defined by showing a PIP-box motif in PfORC1 mediates direct binding functional in vivo.","evidence":"in vitro pull-down binding assay plus yeast complementation with domain deletion/mutation","pmids":["19633266"],"confidence":"Medium","gaps":["Structural basis of the PIP-box/PCNA1 contact not resolved","Whether other PIP-box proteins compete for PCNA1 unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"claim":"Dissecting the genetic elements controlling PCNA1 expression separated absolute expression level from temporal control, showing temporal regulation is independent of the flanking sequences and HDAC activity tested.","evidence":"Bxb1-integrated luciferase reporter with serial 5'/3' deletions and histone deacetylase inhibitor treatment","pmids":["21354176"],"confidence":"Medium","gaps":["The actual determinant of temporal control remains unidentified","Generalizability to endogenous locus behaviour untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"claim":"Assigning primary replicative function among the two PCNAs and defining a damage response established PCNA1 as the principal clamp and a stability-regulated DDR effector.","evidence":"yeast complementation, replication-foci imaging, DNA-damage western blots with qRT-PCR controls, and genotoxic overexpression challenge","pmids":["26251451"],"confidence":"High","gaps":["The stabilization mechanism upon damage not identified","Division of labour between PCNA1 and PCNA2 in the DDR unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Discovery of phosphorylation and TNF-triggered cytoplasm-to-nucleus redistribution linked PCNA1 to host-derived external signalling beyond replication.","evidence":"2D gel/western, cytoplasm-nucleus fractionation, and mass-spectrometric identification of a triple-serine phosphopeptide","pmids":["26893139"],"confidence":"Medium","gaps":["Kinase/phosphatase controlling the phospho-switch unknown","Functional consequence of TNF-induced nuclear shift undefined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Identifying tyrosine 213 as essential for nuclear retention pinpointed a residue governing PCNA1 foci formation and replication function, distinct from serine 191 phosphorylation.","evidence":"site-directed mutagenesis (Y213F, S191) with parasite immunofluorescence and yeast complementation","pmids":["30052905"],"confidence":"High","gaps":["Molecular basis by which Y213 controls retention unresolved","Whether Y213 is post-translationally modified in vivo not shown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How PCNA1's replication role, damage-induced stabilization, and TNF-responsive relocalization are mechanistically integrated, and what upstream enzymes control its phosphorylation and stability, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of PCNA1 or its ORC contacts","Regulators of PCNA1 protein stability unidentified","Kinase for the TNF-linked phospho-switch unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["PFORC1","PFORC5"],"other_free_text":["PCNA1 recruitment to origins mediated by a PIP-box motif in PfORC1 (direct binding, functional in yeast and parasite) [#4]","Nuclear retention and replication-foci formation require conserved tyrosine 213; Y213F abolishes function [#8]","Serine 191 phosphorylation is dispensable for nuclear localization [#8]","Phosphorylated (triple-serine phosphopeptide) and undergoes TNF-triggered cytoplasm-to-nucleus redistribution with dephosphorylation and turnover [#7]","DNA-damage-induced accumulation regulated at protein stability level, not transcription; overexpression confers genotoxic resistance [#6]","Primary replicative PCNA that complements yeast PCNA, in contrast to sibling PCNA2 [#6]","Protein accumulates from trophozoite stage through schizogony while promoter is constitutively active (post-transcriptional coordination) [#0, #2]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"8946386","id":"PMC_8946386","title":"Physical and functional mapping of the transcriptional start sites of Plasmodium falciparum proliferating cell nuclear antigen.","date":"1996","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/8946386","citation_count":45,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"8855554","id":"PMC_8855554","title":"Stage specific expression of proliferating cell nuclear antigen and DNA polymerase delta from Plasmodium falciparum.","date":"1996","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/8855554","citation_count":36,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27080559","id":"PMC_27080559","title":"Tumor necrosis factor reduces Plasmodium falciparum growth and activates calcium signaling in human malaria parasites.","date":"2016","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/27080559","citation_count":34,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["proliferating cell nuclear antigen 1","PfPCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"8095096","id":"PMC_8095096","title":"Molecular characterisation and stage-specific expression of proliferating cell nuclear antigen (PCNA) from the malarial parasite, Plasmodium falciparum.","date":"1993","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/8095096","citation_count":33,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"18554328","id":"PMC_18554328","title":"Plasmodium falciparum origin recognition complex subunit 5: functional characterization and role in DNA replication foci formation.","date":"2008","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/18554328","citation_count":27,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"10960171","id":"PMC_10960171","title":"Two genes encoding unique proliferating-cell-nuclear-antigens are expressed in Toxoplasma gondii.","date":"2000","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/10960171","citation_count":21,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPCNA1"],"competing_organism_flag":true,"competing_organism_match":"Toxoplasma","competing_organism_only":true},{"pmid":"26251451","id":"PMC_26251451","title":"Functional dissection of proliferating-cell nuclear antigens (1 and 2) in human malarial parasite Plasmodium falciparum: possible involvement in DNA replication and DNA damage response.","date":"2015","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/26251451","citation_count":21,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"12413950","id":"PMC_12413950","title":"Molecular characterization and expression of an alternate proliferating cell nuclear antigen homologue, PfPCNA2, in Plasmodium falciparum.","date":"2002","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/12413950","citation_count":18,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"21354176","id":"PMC_21354176","title":"Analysis of the molecular mechanisms governing the stage-specific expression of a prototypical housekeeping gene during intraerythrocytic development of P. falciparum.","date":"2011","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21354176","citation_count":18,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19633266","id":"PMC_19633266","title":"Functional dissection of the catalytic carboxyl-terminal domain of origin recognition complex subunit 1 (PfORC1) of the human malaria parasite Plasmodium falciparum.","date":"2009","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/19633266","citation_count":14,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26893139","id":"PMC_26893139","title":"An external sensing system in Plasmodium falciparum-infected erythrocytes.","date":"2016","source":"Malaria journal","url":"https://pubmed.ncbi.nlm.nih.gov/26893139","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PCNA1","PfPCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"12464414","id":"PMC_12464414","title":"Identification of a second proliferating cell nuclear antigen in the human malarial pathogen Plasmodium falciparum.","date":"2002","source":"International journal for parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/12464414","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30865364","id":"PMC_30865364","title":"Molecular characterization and expression profile of an alternate proliferating cell nuclear antigen homolog PbPCNA2 in Plasmodium berghei.","date":"2019","source":"IUBMB life","url":"https://pubmed.ncbi.nlm.nih.gov/30865364","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30052905","id":"PMC_30052905","title":"Role of tyrosine residue (Y213) in nuclear retention of PCNA1 in human malaria parasite Plasmodium falciparum.","date":"2018","source":"FEMS microbiology letters","url":"https://pubmed.ncbi.nlm.nih.gov/30052905","citation_count":2,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PCNA1","PfPCNA1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9232,"output_tokens":2896,"usd":0.035568,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8509,"output_tokens":3477,"usd":0.064735,"stage2_stop_reason":"end_turn"},"total_usd":0.100303,"stage1_batch_id":"msgbatch_011BPjN2BL33F8cJXD1r7V7T","stage2_batch_id":"msgbatch_01Qwg6vP7qxkpL6Gsc7tajsb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1993,\n      \"finding\": \"PCNA1 (PfPCNA1) is encoded by a single-exon gene on chromosome 13 of P. falciparum, predicting a 30,586 Da protein; antibodies against a PfPCNA1-GST fusion protein recognize a single ~32 kDa band in western blots, and expression is regulated during intraerythrocytic development, increasing dramatically in late trophozoites and persisting through schizogony.\",\n      \"method\": \"Western blot with anti-PfPCNA1-GST antiserum; northern blot; molecular characterization of coding sequence\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein detection by specific antibody plus stage-specific expression profiling, single lab with two orthogonal methods (western blot, northern blot)\",\n      \"pmids\": [\"8095096\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The PCNA1 promoter contains a major transcription start site 960 bp upstream of the translational start and a minor site 40 bp further upstream; a 470 bp region encompassing these sites is essential for promoter activity, and a region 290–620 bp upstream of the transcriptional start is required for efficient promoter activity, as determined by transient transfection of luciferase reporter constructs.\",\n      \"method\": \"RNase protection assay; primer extension; transient transfection with luciferase reporter constructs containing serially deleted 5' flanking sequences\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RNase protection, primer extension, reporter assay with deletion mapping), single lab\",\n      \"pmids\": [\"8946386\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"PCNA1 protein and transcript accumulate at the trophozoite stage and persist in schizonts; nuclear run-on analysis shows that the PCNA1 promoter is active throughout the intraerythrocytic cycle (unlike PfDNA Pol delta, which is absent in rings), suggesting post-transcriptional regulation coordinates PCNA1 expression with DNA replication.\",\n      \"method\": \"Western blot of synchronised parasite extracts; northern blot; nuclear run-on transcription assay\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — nuclear run-on plus western/northern blot in synchronised parasites, single lab, two orthogonal methods\",\n      \"pmids\": [\"8855554\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PCNA1 (PfPCNA1) colocalizes with PfORC5 in distinct nuclear replication foci during early-to-mid trophozoite stage and co-immunoprecipitates with PfORC5 at this stage; the two proteins separate at the non-replicating late schizont stage. PfORC1 also colocalizes with PCNA1 at the onset of DNA replication. A putative PCNA-interacting protein (PIP) box in PfORC1 may mediate colocalization. The DNA replication inhibitor hydroxyurea disrupts ORC5/PCNA1 foci formation.\",\n      \"method\": \"Co-immunoprecipitation; immunofluorescence colocalization; hydroxyurea inhibitor treatment; bioinformatic identification of PIP box\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus immunofluorescence colocalization in synchronised parasites, single lab, two orthogonal methods\",\n      \"pmids\": [\"18554328\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The putative PIP (PCNA-interacting protein) motif in PfORC1 mediates direct physical interaction with PCNA1 in vitro and is functional in vivo in both yeast and P. falciparum, as shown by biochemical pull-down and yeast complementation.\",\n      \"method\": \"In vitro binding assay (biochemical interaction); yeast genetic complementation; domain deletion/mutation analysis\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro interaction assay plus yeast complementation, single lab, two orthogonal methods\",\n      \"pmids\": [\"19633266\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The 5' and 3' genetic elements of the PCNA1 (Pfpcna) locus control both the absolute level and temporal pattern of gene expression during the intraerythrocytic cycle; serial deletion of these elements and treatment with histone deacetylase inhibitors perturbed absolute expression but did not affect temporal control, supporting a model in which temporal regulation of PCNA1 (and potentially hundreds of other genes) is independent of histone deacetylase activity and of the flanking regulatory sequences tested.\",\n      \"method\": \"Bxb1 integrase-mediated site-specific integration of luciferase reporter with serial 5'/3' deletions; histone deacetylase inhibitor treatment; quantitative luciferase assay\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — integrated reporter system with systematic deletion analysis plus pharmacological perturbation, single lab, multiple constructs\",\n      \"pmids\": [\"21354176\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PCNA1 (PfPCNA1), but not PfPCNA2, functionally complements a ScPCNA mutant in yeast and forms distinct nuclear replication foci in P. falciparum parasites, establishing PCNA1 as the primary replicative PCNA. Both PfPCNA1 and PfPCNA2 accumulate significantly upon DNA damage induction, participating in an active DNA-damage-response (DDR) pathway. Regulation upon DNA damage occurs at the protein stability level rather than at the transcriptional level. Overexpression of PfPCNA1 confers a survival advantage in a genotoxic environment.\",\n      \"method\": \"Yeast complementation assay; immunofluorescence (replication foci); western blot of DNA-damage-induced parasites; quantitative RT-PCR (ruling out transcriptional regulation); parasite overexpression with genotoxic challenge\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — yeast complementation (Tier 1) combined with in-parasite foci imaging, transcription/protein-level dissection, and functional overexpression, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"26251451\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PCNA1 (PfPCNA1) is phosphorylated in P. falciparum-infected erythrocytes; it localizes predominantly to the parasite cytoplasm but transiently shifts to the nucleus upon TNF stimulation, accompanied by dephosphorylation and rapid protein turnover. A triple serine-phosphorylated PCNA1 peptide was identified by mass spectrometry in a high-expressing strain. This response to TNF is part of an external sensing system in the parasite.\",\n      \"method\": \"2D gel electrophoresis followed by western blot; biochemical fractionation (cytoplasm vs. nucleus); high-resolution mass spectrometry of immune precipitants; real-time qRT-PCR\",\n      \"journal\": \"Malaria journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mass spectrometry identification of phosphopeptide plus biochemical fractionation showing subcellular redistribution, single lab, two orthogonal methods\",\n      \"pmids\": [\"26893139\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Tyrosine 213 (Y213) of PCNA1 is required for nuclear retention and replication foci formation of PfPCNA1 in P. falciparum; a Y213F mutation causes functional loss in both yeast complementation and parasite assays. Serine 191 phosphorylation (reported in phospho-proteome data) was found not to be important for this nuclear localization function. The conserved tyrosine residue is linked to DNA replication and cell proliferation.\",\n      \"method\": \"Site-directed mutagenesis (Y213F, S191); immunofluorescence (nuclear localization and foci formation in parasite); yeast complementation assay\",\n      \"journal\": \"FEMS microbiology letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-directed mutagenesis with functional readout in two independent systems (yeast complementation + parasite immunofluorescence), rigorous controls distinguishing Y213 from S191\",\n      \"pmids\": [\"30052905\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PF3D7_1361900 (PCNA1) is the primary replicative proliferating cell nuclear antigen of P. falciparum: its promoter is constitutively active throughout the intraerythrocytic cycle with temporal protein accumulation regulated post-transcriptionally; PCNA1 forms distinct nuclear replication foci, physically interacts with PfORC1 (via a PIP-box interaction) and PfORC5 during S phase, functionally complements yeast PCNA, and its nuclear retention depends on conserved tyrosine 213 whose mutation abolishes foci formation and function in both yeast and parasite; additionally, PCNA1 undergoes serine phosphorylation and cytoplasm-to-nucleus redistribution in response to TNF signalling, and both PCNA1 and PCNA2 accumulate (regulated at protein stability rather than transcription level) in response to DNA damage, with PCNA1 overexpression conferring genotoxic resistance.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_1361900 (PCNA1) is the primary replicative proliferating cell nuclear antigen of Plasmodium falciparum, coordinating DNA replication and the DNA-damage response during intraerythrocytic development [#6]. It is encoded by a single-exon gene whose protein accumulates from the trophozoite stage and persists through schizogony; although its promoter is transcriptionally active throughout the intraerythrocytic cycle, its protein accumulation is coordinated post-transcriptionally with DNA replication [#0, #2]. During S phase PCNA1 assembles into distinct nuclear replication foci and physically engages the origin recognition complex, co-immunoprecipitating and colocalizing with PfORC5 and colocalizing with PfORC1 at replication onset via a PIP-box in PfORC1 that mediates direct binding, an interaction functional in both yeast and parasite [#3, #4]. PCNA1, but not the sibling PCNA2, complements a yeast PCNA mutant, confirming its role as the principal replicative clamp; both accumulate upon genotoxic stress through regulation of protein stability rather than transcription, and PCNA1 overexpression confers genotoxic resistance [#6]. Nuclear retention and foci formation depend on the conserved tyrosine 213, whose mutation abolishes function in both yeast and parasite [#8]. PCNA1 is also phosphorylated in infected erythrocytes and redistributes transiently from cytoplasm to nucleus upon TNF stimulation with accompanying dephosphorylation and turnover [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing that P. falciparum encodes a PCNA and expresses it in a replication-linked pattern was the first step toward defining the parasite's replicative machinery.\",\n      \"evidence\": \"molecular characterization of a single-exon chromosome-13 gene with specific antibody detection and stage-resolved northern/western blots\",\n      \"pmids\": [\"8095096\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the detected protein functions as a replicative clamp not yet tested\", \"Interaction partners unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Promoter mapping and run-on analysis addressed how PCNA1 expression is temporally coordinated, revealing constitutive transcription with the replication-coupled protein accumulation set post-transcriptionally.\",\n      \"evidence\": \"RNase protection/primer extension promoter mapping, luciferase reporter deletion analysis, and nuclear run-on transcription assays in synchronised parasites\",\n      \"pmids\": [\"8946386\", \"8855554\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of post-transcriptional coordination unidentified\", \"Trans-acting factors on the promoter not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Whether PCNA1 physically couples to replication origins was answered by demonstrating S-phase-specific association with the origin recognition complex.\",\n      \"evidence\": \"co-immunoprecipitation and immunofluorescence colocalization with PfORC5/PfORC1 in synchronised parasites, disrupted by hydroxyurea\",\n      \"pmids\": [\"18554328\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Directness of ORC5 interaction not established biochemically\", \"Functional consequence of the interaction untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The mechanism of PCNA1 recruitment to origins was defined by showing a PIP-box motif in PfORC1 mediates direct binding functional in vivo.\",\n      \"evidence\": \"in vitro pull-down binding assay plus yeast complementation with domain deletion/mutation\",\n      \"pmids\": [\"19633266\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of the PIP-box/PCNA1 contact not resolved\", \"Whether other PIP-box proteins compete for PCNA1 unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Dissecting the genetic elements controlling PCNA1 expression separated absolute expression level from temporal control, showing temporal regulation is independent of the flanking sequences and HDAC activity tested.\",\n      \"evidence\": \"Bxb1-integrated luciferase reporter with serial 5'/3' deletions and histone deacetylase inhibitor treatment\",\n      \"pmids\": [\"21354176\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The actual determinant of temporal control remains unidentified\", \"Generalizability to endogenous locus behaviour untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Assigning primary replicative function among the two PCNAs and defining a damage response established PCNA1 as the principal clamp and a stability-regulated DDR effector.\",\n      \"evidence\": \"yeast complementation, replication-foci imaging, DNA-damage western blots with qRT-PCR controls, and genotoxic overexpression challenge\",\n      \"pmids\": [\"26251451\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The stabilization mechanism upon damage not identified\", \"Division of labour between PCNA1 and PCNA2 in the DDR unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Discovery of phosphorylation and TNF-triggered cytoplasm-to-nucleus redistribution linked PCNA1 to host-derived external signalling beyond replication.\",\n      \"evidence\": \"2D gel/western, cytoplasm-nucleus fractionation, and mass-spectrometric identification of a triple-serine phosphopeptide\",\n      \"pmids\": [\"26893139\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase/phosphatase controlling the phospho-switch unknown\", \"Functional consequence of TNF-induced nuclear shift undefined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identifying tyrosine 213 as essential for nuclear retention pinpointed a residue governing PCNA1 foci formation and replication function, distinct from serine 191 phosphorylation.\",\n      \"evidence\": \"site-directed mutagenesis (Y213F, S191) with parasite immunofluorescence and yeast complementation\",\n      \"pmids\": [\"30052905\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis by which Y213 controls retention unresolved\", \"Whether Y213 is post-translationally modified in vivo not shown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PCNA1's replication role, damage-induced stabilization, and TNF-responsive relocalization are mechanistically integrated, and what upstream enzymes control its phosphorylation and stability, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of PCNA1 or its ORC contacts\", \"Regulators of PCNA1 protein stability unidentified\", \"Kinase for the TNF-linked phospho-switch unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003684\", \"supporting_discovery_ids\": [6, 8]},\n      {\"term_id\": \"GO:0030337\", \"supporting_discovery_ids\": [6, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3, 6, 8]},\n      {\"term_id\": \"GO:0043596\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006260\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"GO:0006281\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0006974\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PfORC1\", \"PfORC5\"],\n    \"other_free_text\": [\n      \"PCNA1 recruitment to origins mediated by a PIP-box motif in PfORC1 (direct binding, functional in yeast and parasite) [#4]\",\n      \"Nuclear retention and replication-foci formation require conserved tyrosine 213; Y213F abolishes function [#8]\",\n      \"Serine 191 phosphorylation is dispensable for nuclear localization [#8]\",\n      \"Phosphorylated (triple-serine phosphopeptide) and undergoes TNF-triggered cytoplasm-to-nucleus redistribution with dephosphorylation and turnover [#7]\",\n      \"DNA-damage-induced accumulation regulated at protein stability level, not transcription; overexpression confers genotoxic resistance [#6]\",\n      \"Primary replicative PCNA that complements yeast PCNA, in contrast to sibling PCNA2 [#6]\",\n      \"Protein accumulates from trophozoite stage through schizogony while promoter is constitutively active (post-transcriptional coordination) [#0, #2]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1361900","name":null,"product":"proliferating cell nuclear antigen 1","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1137900","name":null,"product":"proliferating cell nuclear antigen 1, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1109400","name":null,"product":"proliferating cell nuclear antigen 1, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"PCNA1","evaluation":null}