{"gene":"PF3D7_0823300","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":2004,"finding":"PfGCN5 encodes a histone acetyltransferase with conserved HAT activity that preferentially acetylates histone H3, specifically at K8 and K14, as determined using recombinant PfGCN5 and substrate-specific antibodies. The HAT domain of PfGCN5 can partially complement a yeast GCN5 deletion mutant, and a chimera containing the PfGCN5 HAT domain fused to the remainder of yeast GCN5 fully rescues the yGCN5 deletion.","method":"In vitro HAT assay with free core histones; substrate-specific antibody detection; yeast complementation assay","journal":"Eukaryotic cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis-equivalent substrate mapping, validated by yeast genetic complementation in a single rigorous study","pmids":["15075257"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2004,"finding":"PfGCN5 physically interacts with PfADA2 (the P. falciparum ADA2 homologue), as shown by yeast two-hybrid and in vitro binding assays, suggesting they associate in a complex in vivo.","method":"Yeast two-hybrid assay; in vitro binding assay","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal binding methods (yeast two-hybrid + in vitro pulldown) in a single study; in vivo association not directly proven","pmids":["15075257"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2004,"finding":"Anti-GCN5 antibodies immunoprecipitate a ~200 kDa protein from parasite lysate with HAT activity similar to recombinant GCN5, and this HAT activity is also immunoprecipitated by anti-PfADA2 antibodies, demonstrating that PfADA2 is associated with PfGCN5 in vivo.","method":"Co-immunoprecipitation with HAT activity assay","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal immunoprecipitation with functional readout (HAT activity), single lab","pmids":["15246536"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Recombinant PfGCN5 efficiently acetylates recombinant PfH3 at K9 and K14, despite divergence in the PfH3 N-terminus from mammalian homologues, and native PfGCN5 does likewise, establishing H3K9 and H3K14 as the primary in vitro substrates.","method":"In vitro HAT assay with recombinant substrates; acetylation-specific antibody detection; native PfGCN5 from parasite extracts","journal":"Gene","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with both recombinant and native enzyme, confirmed with substrate-specific antibodies, consistent with prior study","pmids":["16410041"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Curcumin inhibits the HAT activity of recombinant PfGCN5 in vitro and reduces nuclear HAT activity in parasite culture, causing hypoacetylation of histone H3 at K9 and K14 but not H4 at K5, K8, K12, or K16, indicating substrate-specific inhibition of PfGCN5.","method":"In vitro HAT assay with recombinant PfGCN5; nuclear HAT activity assay from parasite extracts; acetylation-specific antibodies","journal":"Antimicrobial agents and chemotherapy","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay plus cell-based readout with site-specific antibodies, single lab, two orthogonal methods","pmids":["17145789"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"Genome-wide ChIP-chip analysis shows that PfGCN5 is distributed across the P. falciparum genome with a chromosomal distribution similar to H3K9ac but distinct from H3K9me3. PfGCN5 occupancy is enriched at promoter regions of actively expressed genes in a stage-specific manner, and treatment with a PfGCN5 inhibitor reduces promoter H3K9ac and gene expression, establishing that PfGCN5 mediates H3K9ac at promoters to activate transcription.","method":"Chromatin immunoprecipitation (ChIP) coupled with DNA microarray (ChIP-chip); real-time PCR; HAT inhibitor treatment","journal":"Eukaryotic cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide ChIP-chip with stage-specific validation and pharmacological inhibitor confirmation, multiple orthogonal methods","pmids":["17449656"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"Anacardic acid reversibly and non-competitively inhibits HAT activity of recombinant PfGCN5 and to a lesser extent PfGCN5 in parasite nuclear extracts, without affecting histone deacetylase activity. This causes hypoacetylation of H3K9 and H3K14 (but not H4K5/K8/K12/K16) and ChIP shows reduced acetylation near promoters of downregulated genes.","method":"In vitro HAT assay; nuclear extract HAT assay; ChIP with real-time PCR; acetylation-specific antibodies; microarray","journal":"Eukaryotic cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic characterization plus cell-based ChIP and transcriptomic confirmation, multiple orthogonal methods in a single study","pmids":["18487348"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"PfGCN5 is recruited to the enhancer region of the pf1-cys-prx gene specifically during trophozoite/schizont stages, as shown by ChIP, correlating with elevated histone acetylation and stage-specific transcriptional activity.","method":"Chromatin immunoprecipitation (ChIP); reporter assay; electrophoretic mobility shift assay (EMSA); DNase I footprinting","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating recruitment with functional correlation, single lab, single gene focus","pmids":["18692528"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Quantitative proteomic interaction studies identify two distinct GCN5/ADA2 complexes in P. falciparum, revealing the composition of PfGCN5-containing epigenetic complexes and their interactions with other epigenetic regulatory complexes.","method":"Histone peptide pull-downs; quantitative proteomics (mass spectrometry); tagging and interaction proteomics","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based interactome proteomics identifying complex composition, single study","pmids":["31728527"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"PfGCN5 undergoes novel proteolytic processing by a cysteine protease-like enzyme that is essential for its activity in vivo. The processing occurs near the digestive vacuole following trafficking through the ER-Golgi secretory pathway before PfGCN5 reaches the nucleus. Blocking processing reduces PfGCN5 occupancy at gene promoters and lowers H3K9ac at those promoters.","method":"Immunofluorescence; immuno-electron microscopy; cysteine protease inhibitor treatment; ChIP; fractionation","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — localization by IFA and immuno-EM with functional consequence shown by ChIP, single lab, multiple imaging methods","pmids":["31862795"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"PfGCN5 forms a divergent HAT complex in P. falciparum that includes two plant homeodomain (PHD) proteins (PfPHD1 and PfPHD2) and an AP2-domain transcription factor (PfAP2-LT). Deletion of the bromodomain of PfGCN5 or the PHD domain of PfPHD1 reduces merozoite invasion of erythrocytes, elevates sexual conversion, decreases H3K9 acetylation and H3K4 trimethylation, and disrupts global transcription including mutually exclusive var gene expression.","method":"CRISPR-based domain deletion; phenotypic assays (invasion, sexual conversion); RNA-seq; ChIP-seq; immunoprecipitation/proteomics","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic domain deletions with multiple orthogonal phenotypic and chromatin readouts, replicated across two subunit deletions in a single rigorous study","pmids":["34403450"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"ChIP-seq shows PfGCN5 binds to stress-responsive genes (including those involved in artemisinin resistance such as BiP and TRiC chaperone) in a poised state under normal conditions, and genome-wide PfGCN5 binding sites increase upon artemisinin exposure. Inhibition of PfGCN5 increases sensitivity of artemisinin-resistant parasites to artemisinin.","method":"ChIP-seq; pharmacological inhibition of PfGCN5; growth assay/drug sensitivity assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP-seq with functional pharmacological validation, single lab","pmids":["33441725"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"PfGCN5 interacts with and acetylates PfGAPDH (glyceraldehyde-3-phosphate dehydrogenase) in vitro. Immunoprecipitation coupled with mass spectrometry identifies various metabolic enzymes as PfGCN5 interacting partners, suggesting a role beyond histone acetylation.","method":"Immunoprecipitation coupled with mass spectrometry; in vitro acetylation assay","journal":"Journal of biosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro acetyltransferase assay plus MS-based interactome, single lab, single study","pmids":["31965989"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"A co-crystal structure of the bromodomain inhibitor L-45 (L-Moses) with the PfGCN5 bromodomain was solved, rationalizing the high selectivity of the compound for PCAF and GCN5 bromodomains.","method":"X-ray co-crystallography; biophysical characterization","journal":"Angewandte Chemie (International ed. in English)","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — crystal structure of the bromodomain with bound inhibitor, but mechanistic functional validation in parasites was not the focus of this paper; single study","pmids":["27966810"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"PfGCN5 bromodomain directly binds diacetylated histone H2A.Z (at K4 and K11) with a Kd of ~650 µM, as determined by NMR-based biophysical assays.","method":"Protein-observed 19F NMR (PrOF NMR); Carr-Purcell-Meiboom-Gill NMR; photo-cross-linking","journal":"Biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — binding detected by NMR with very low affinity (650 µM), no functional validation in parasites, single study","pmids":["28771339"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"Conditional knockdown of PfGCN5 to ~50% sensitizes P. falciparum to heat shock, glucose starvation, and dihydroartemisinin. RNA-seq identifies ~300-400 PfGCN5-dependent genes involved in stress responses, including ART-resistance-related genes K13 and coronin. KD or inhibition of PfGCN5 sensitizes ART-resistant parasites to DHA treatment.","method":"TetR-DOZI conditional knockdown; RNA-seq; ring-stage survival assay; pharmacological inhibition","journal":"Antimicrobial agents and chemotherapy","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic knockdown with transcriptomic readout replicated across multiple stress conditions and validated by pharmacological inhibition, single lab but multiple orthogonal approaches","pmids":["37702516"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"Falcipain 3 (FP3), a food vacuolar cysteine protease, directly interacts with PfGCN5 as shown by co-immunoprecipitation and in vitro pull-down assay. Use of the cysteine protease inhibitor E64d blocks proteolytic processing of PfGCN5 and causes co-localization of PfGCN5 and FP3 around the food vacuole, identifying FP3 as the protease responsible for PfGCN5 processing.","method":"Co-immunoprecipitation followed by LC-MS/MS; in vitro pull-down assay; cysteine protease inhibitor treatment; confocal and electron microscopy","journal":"Biotechnology and applied biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal pulldown and IP with inhibitor-based functional validation and colocalization imaging, single lab","pmids":["38924147"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"PfGCN5 is essential for parasite survival in human blood and transmission to mosquitoes. Its bromodomain (BRD) is required at euchromatic gene promoters for proper expression and for acetylation of the variant histone PfH2B.Z. Loss of the BRD de-represses heterochromatic genes and increases acetylated PfH2B.Z in heterochromatin, indicating PfGCN5 maintains repressive heterochromatin structure. The BRD-binding compound L-45 phenocopies BRD deletion.","method":"Conditional genetic knockdown/deletion; ChIP-seq; histone modification profiling; drug treatment phenocopy; gametocyte/mosquito transmission assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic deletion with multiple chromatin readouts (ChIP-seq, histone modification), phenocopy by chemical probe, and functional assay across multiple life stages in a single rigorous study","pmids":["40156869"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"PfGCN5 acetylates PfPGM1 (phosphoglycerate mutase 1) at K100, a residue critical for PfPGM1 catalytic activity, stabilizing the protein. Additionally, PfGCN5 occupies the PfPGM1 promoter in a stage-specific manner, and knockdown of PfGCN5 reduces PfPGM1 transcript levels, demonstrating dual regulation of a glycolytic enzyme at both the protein and transcriptional levels.","method":"In vitro acetylation assay; knockdown with cycloheximide treatment; ChIP; RT-PCR/transcriptomics","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro acetyltransferase assay plus ChIP and KD-based transcriptional readout, two orthogonal mechanistic approaches, single lab","pmids":["40567037"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"Conditional knockdown of PfGCN5 phenotypically recapitulates bromodomain deletion growth defects. CUT&Tag-seq shows PfGCN5 co-localizes with H3K9ac at gene promoters, and the H3K9ac peak intensity positively correlates with levels of gene expression. PfGCN5 chromatin positions overlap with DNA sequence motifs recognized by multiple AP2 transcription factors, indicating AP2-domain TFs recruit PfGCN5 to target promoters. PfGCN5 co-localizes with AP2-LT, confirming AP2-LT as a component of the PfGCN5 complex.","method":"TetR-DOZI conditional knockdown; CUT&Tag-seq; motif analysis; colocalization analysis","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KD phenocopy combined with CUT&Tag-seq chromatin mapping and motif-based recruitment evidence, multiple orthogonal approaches in a single study","pmids":["40558503"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"The poly-asparagine repeat-containing N-terminus of PfGCN5 associates with its C-terminal catalytic domain after proteolytic cleavage in the nucleus. Deletion of the poly-asparagine repeat destabilizes the N-terminal polypeptide, impairs parasite development and growth (especially under stress), and profoundly reduces acetylation of histones H3, H3.3, and H4, demonstrating that the poly-asparagine repeat contributes to PfGCN5 acetyltransferase activity in vivo.","method":"Genetic deletion; high-resolution mass spectrometry; western blotting; growth and stress assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic deletion with MS-based histone modification profiling, single lab, two orthogonal methods","pmids":["42323337"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"PfGCN5 (PF3D7_0823300) is an essential histone acetyltransferase that preferentially acetylates histone H3 at K9 and K14 (and to some extent K8) using a conserved catalytic HAT domain and a bromodomain that binds acetylated histones; it is recruited to euchromatic gene promoters by AP2-domain transcription factors to deposit H3K9ac and activate transcription, while also maintaining repressive heterochromatin structure via its bromodomain; it exists in a divergent SAGA-like complex together with PfADA2, two PHD-finger proteins (PfPHD1/PfPHD2), and the AP2-LT transcription factor; beyond histones, it acetylates non-histone substrates including PfGAPDH and PfPGM1; it undergoes essential proteolytic processing by the food vacuolar cysteine protease Falcipain 3 before reaching the nucleus; its poly-asparagine N-terminus associates with the C-terminal catalytic domain after cleavage and contributes to acetyltransferase activity; it is required for erythrocyte invasion, virulence gene (var) regulation, stress responses, and parasite transmission to mosquitoes, making it a validated antimalarial drug target."},"narrative":{"mechanistic_narrative":"PF3D7_0823300 (GCN5) is an essential histone acetyltransferase that couples chromatin acetylation to stage-specific transcriptional programs in Plasmodium falciparum [PMID:15075257, PMID:17449656, PMID:40156869]. Its conserved HAT domain preferentially acetylates histone H3 at K9 and K14 (and to a lesser extent K8), a specificity retained across the divergent P. falciparum H3 N-terminus and validated by functional complementation of a yeast GCN5 deletion [PMID:15075257, PMID:16410041]. Genome-wide, GCN5 occupancy tracks H3K9ac and is enriched at promoters of actively transcribed genes, where its deposition of H3K9ac activates transcription; H3K9ac peak intensity correlates positively with expression level [PMID:17449656, PMID:40558503]. GCN5 is recruited to target promoters by AP2-domain transcription factors, whose binding motifs coincide with GCN5 chromatin positions, and it co-localizes with AP2-LT [PMID:40558503]. It acts within a divergent SAGA-like complex containing PfADA2, the PHD-finger proteins PfPHD1/PfPHD2, and PfAP2-LT [PMID:15075257, PMID:15246536, PMID:31728527, PMID:34403450]. Through its bromodomain GCN5 also acetylates the variant histone PfH2B.Z and maintains repressive heterochromatin: bromodomain loss de-represses heterochromatic and var genes, impairs erythrocyte invasion, and elevates sexual conversion [PMID:34403450, PMID:40156869]. GCN5 additionally acts on non-histone substrates, acetylating and stabilizing the glycolytic enzymes PfGAPDH and PfPGM1 while also transcriptionally regulating PfPGM1 [PMID:31965989, PMID:40567037]. Before nuclear function, GCN5 is proteolytically processed near the food vacuole by the cysteine protease Falcipain 3, a step essential for its promoter occupancy and H3K9ac activity, after which its poly-asparagine N-terminus reassociates with the catalytic domain to support acetyltransferase activity [PMID:31862795, PMID:38924147, PMID:42323337]. GCN5 governs stress responses and artemisinin resistance and is required for blood-stage survival and mosquito transmission, making it a validated antimalarial target with a bromodomain amenable to selective inhibition [PMID:17449656, PMID:33441725, PMID:37702516, PMID:40156869].","teleology":[{"year":2004,"claim":"Establishing that the Plasmodium enzyme was a bona fide, catalytically conserved histone acetyltransferase answered whether P. falciparum possesses functional chromatin-modifying machinery of the GCN5 type.","evidence":"In vitro HAT assay on free core histones with site-specific antibodies plus rescue of a yeast GCN5 deletion by the PfGCN5 HAT domain","pmids":["15075257"],"confidence":"High","gaps":["Substrate mapping in vitro on free histones does not establish nucleosomal specificity","In vivo genomic targets not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2004,"claim":"Identifying PfADA2 as a physical partner answered whether GCN5 operates within a multi-subunit adaptor complex rather than alone.","evidence":"Yeast two-hybrid and in vitro binding assays; reciprocal co-immunoprecipitation of a ~200 kDa HAT-active species from parasite lysate","pmids":["15075257","15246536"],"confidence":"Medium","gaps":["Full complex composition not resolved","Stoichiometry and functional role of ADA2 in activity untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Refining the substrate profile to H3K9 and H3K14 on the divergent P. falciparum H3 clarified the physiologically relevant acetylation marks despite the parasite's atypical H3 N-terminus.","evidence":"In vitro HAT assays with recombinant PfH3 and native PfGCN5, read out with acetylation-specific antibodies","pmids":["16410041"],"confidence":"High","gaps":["Relative in vivo contribution of K9 vs K14 not partitioned","Non-histone substrates not yet examined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"claim":"Genome-wide mapping and pharmacological inhibition established that GCN5 deposits promoter H3K9ac to activate transcription in a stage-specific manner, linking the enzyme to active euchromatin.","evidence":"ChIP-chip of GCN5 versus H3K9ac/H3K9me3, HAT inhibitor treatment with expression and ChIP readouts; anacardic acid and curcumin inhibition confirming substrate-specific hypoacetylation","pmids":["17449656","18487348","17145789","18692528"],"confidence":"High","gaps":["Recruitment mechanism to specific promoters unresolved","Direct versus indirect expression effects not fully separated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Interaction proteomics resolved GCN5 into two distinct GCN5/ADA2 complexes, advancing the picture from a binary partnership to defined epigenetic assemblies.","evidence":"Histone peptide pull-downs and quantitative MS-based interaction proteomics with tagging","pmids":["31728527"],"confidence":"Medium","gaps":["Functional distinction between the two complexes not tested","Subunit-specific roles unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Discovery of essential proteolytic processing near the digestive vacuole before nuclear entry revealed an unexpected post-translational maturation step required for chromatin function.","evidence":"IFA, immuno-EM, cysteine protease inhibitor treatment and ChIP showing reduced promoter occupancy and H3K9ac when processing is blocked","pmids":["31862795"],"confidence":"Medium","gaps":["Protease identity not established in this study","Cleavage sites and trafficking route mechanism unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Detection of non-histone acetylation (PfGAPDH) and metabolic-enzyme interactions extended GCN5's role beyond chromatin into metabolic regulation.","evidence":"IP-MS interactome and in vitro acetylation assay","pmids":["31965989"],"confidence":"Medium","gaps":["Physiological consequence of GAPDH acetylation untested","In vivo acetylation sites not mapped"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"Genetic domain deletions defined a divergent GCN5 HAT complex with PHD proteins and AP2-LT and demonstrated the bromodomain's requirement for invasion, sexual conversion control, and var gene regulation.","evidence":"CRISPR bromodomain/PHD deletions with invasion, sexual-conversion, RNA-seq, ChIP-seq and interaction proteomics readouts; ChIP-seq of poised stress-gene binding with inhibitor drug-sensitivity assays","pmids":["34403450","33441725"],"confidence":"High","gaps":["Bromodomain reader ligand at heterochromatin not defined here","Direct AP2-LT recruitment mechanism not yet shown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"Structural and biophysical characterization of the bromodomain, including inhibitor co-crystallography, established it as a druggable acetyl-lysine reader module.","evidence":"X-ray co-crystal structure with inhibitor L-45; NMR binding to diacetylated H2A.Z","pmids":["27966810","28771339"],"confidence":"Low","gaps":["H2A.Z binding is very low affinity (~650 µM) with no parasite functional validation","In vivo bromodomain ligand not confirmed by these assays"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"claim":"Conditional knockdown established GCN5 as a controller of stress-response transcription and a modifier of artemisinin resistance, giving direct causal genetic evidence for its role.","evidence":"TetR-DOZI knockdown to ~50% with RNA-seq, ring-stage survival assays under heat/glucose/DHA stress and pharmacological inhibition","pmids":["37702516"],"confidence":"High","gaps":["Partial knockdown may underestimate essential functions","Direct GCN5 targets among stress genes not fully separated from downstream effects"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"Identification of Falcipain 3 as the processing protease closed the mechanistic gap on GCN5's essential proteolytic maturation.","evidence":"Co-IP/LC-MS/MS, in vitro pull-down, E64d inhibition blocking processing, and confocal/EM co-localization at the food vacuole","pmids":["38924147"],"confidence":"Medium","gaps":["Precise cleavage sites not mapped","Reconstitution of cleavage with purified FP3 not shown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Combined genetic deletion, chromatin mapping, and chemical phenocopy established that GCN5 both activates euchromatic promoters and maintains repressive heterochromatin through its bromodomain, and is required across blood and transmission stages.","evidence":"Conditional deletion, ChIP-seq/CUT&Tag-seq, histone-modification profiling of PfH2B.Z, AP2-motif overlap and AP2-LT co-localization, transmission assays, and L-45 phenocopy","pmids":["40156869","40558503"],"confidence":"High","gaps":["Direct biochemical demonstration that AP2 TFs recruit GCN5 not fully resolved","Mechanism coupling bromodomain to heterochromatin repression not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Dual regulation of the glycolytic enzyme PfPGM1 (acetylation at catalytic K100 plus promoter occupancy) demonstrated that GCN5 integrates protein-level and transcriptional control of metabolism.","evidence":"In vitro acetylation, cycloheximide-chase stability, ChIP and RT-PCR/transcriptomics","pmids":["40567037"],"confidence":"Medium","gaps":["Physiological impact on glycolytic flux not measured","In vivo K100 acetylation stoichiometry unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"claim":"Demonstrating that the poly-asparagine N-terminus reassociates with the catalytic domain after cleavage and supports activity clarified the functional purpose of GCN5's processing and its low-complexity region.","evidence":"Genetic deletion of the poly-asparagine repeat with high-resolution MS histone profiling, western blotting and growth/stress assays","pmids":["42323337"],"confidence":"Medium","gaps":["Structural basis of N-/C-domain reassociation not resolved","How the repeat enhances catalysis mechanistically unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How AP2-domain transcription factors physically recruit GCN5 to specific promoters, and how a single bromodomain simultaneously drives euchromatic activation and heterochromatic repression, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct biochemical reconstitution of AP2-mediated GCN5 recruitment","Dual euchromatin/heterochromatin bromodomain mechanism undefined","In vivo acetyl-lysine ligand of the bromodomain not conclusively established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Divergent SAGA-like GCN5/ADA2 HAT complex (PfADA2)","GCN5-PfPHD1/PfPHD2-PfAP2-LT complex","Two distinct GCN5/ADA2 complexes resolved by interaction proteomics"],"partners":["PFADA2","PFPHD1","PFPHD2","PFAP2-LT (AP2-DOMAIN TRANSCRIPTION FACTOR)","FALCIPAIN 3 (FP3, FOOD VACUOLAR CYSTEINE PROTEASE)","PFGAPDH (ACETYLATION SUBSTRATE)","PFPGM1 (ACETYLATION SUBSTRATE, K100)"],"other_free_text":["Preferentially acetylates histone H3 at K9 and K14 (and to a lesser extent K8); HAT domain complements yeast GCN5 deletion.","Bromodomain binds acetyl-lysine and acetylates variant histone PfH2B.Z; loss de-represses heterochromatic and var genes.","Undergoes essential proteolytic processing by Falcipain 3 near the food vacuole after ER-Golgi trafficking before nuclear function.","Poly-asparagine N-terminus reassociates with the C-terminal catalytic domain after cleavage and supports acetyltransferase activity.","Recruited to promoters coincident with AP2 transcription factor DNA motifs; H3K9ac peak intensity correlates with expression.","Inhibited by curcumin, anacardic acid, and the bromodomain probe L-45 (L-Moses); bromodomain co-crystal structure solved.","Required for erythrocyte invasion, var gene mutual exclusion, stress responses, artemisinin-resistance modulation, blood-stage survival, and mosquito transmission; validated antimalarial target."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"17145789","id":"PMC_17145789","title":"Cytotoxic effect of curcumin on malaria parasite Plasmodium falciparum: inhibition of histone acetylation and generation of reactive oxygen species.","date":"2006","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/17145789","citation_count":187,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfGCN5"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16410041","id":"PMC_16410041","title":"The malaria parasite Plasmodium falciparum histones: organization, expression, and acetylation.","date":"2006","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/16410041","citation_count":155,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfGCN5"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17449656","id":"PMC_17449656","title":"PfGCN5-mediated histone H3 acetylation plays a key role in gene expression in Plasmodium falciparum.","date":"2007","source":"Eukaryotic 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antibodies. The HAT domain of PfGCN5 can partially complement a yeast GCN5 deletion mutant, and a chimera containing the PfGCN5 HAT domain fused to the remainder of yeast GCN5 fully rescues the yGCN5 deletion.\",\n      \"method\": \"In vitro HAT assay with free core histones; substrate-specific antibody detection; yeast complementation assay\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis-equivalent substrate mapping, validated by yeast genetic complementation in a single rigorous study\",\n      \"pmids\": [\"15075257\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PfGCN5 physically interacts with PfADA2 (the P. falciparum ADA2 homologue), as shown by yeast two-hybrid and in vitro binding assays, suggesting they associate in a complex in vivo.\",\n      \"method\": \"Yeast two-hybrid assay; in vitro binding assay\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal binding methods (yeast two-hybrid + in vitro pulldown) in a single study; in vivo association not directly proven\",\n      \"pmids\": [\"15075257\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Anti-GCN5 antibodies immunoprecipitate a ~200 kDa protein from parasite lysate with HAT activity similar to recombinant GCN5, and this HAT activity is also immunoprecipitated by anti-PfADA2 antibodies, demonstrating that PfADA2 is associated with PfGCN5 in vivo.\",\n      \"method\": \"Co-immunoprecipitation with HAT activity assay\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal immunoprecipitation with functional readout (HAT activity), single lab\",\n      \"pmids\": [\"15246536\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Recombinant PfGCN5 efficiently acetylates recombinant PfH3 at K9 and K14, despite divergence in the PfH3 N-terminus from mammalian homologues, and native PfGCN5 does likewise, establishing H3K9 and H3K14 as the primary in vitro substrates.\",\n      \"method\": \"In vitro HAT assay with recombinant substrates; acetylation-specific antibody detection; native PfGCN5 from parasite extracts\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with both recombinant and native enzyme, confirmed with substrate-specific antibodies, consistent with prior study\",\n      \"pmids\": [\"16410041\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Curcumin inhibits the HAT activity of recombinant PfGCN5 in vitro and reduces nuclear HAT activity in parasite culture, causing hypoacetylation of histone H3 at K9 and K14 but not H4 at K5, K8, K12, or K16, indicating substrate-specific inhibition of PfGCN5.\",\n      \"method\": \"In vitro HAT assay with recombinant PfGCN5; nuclear HAT activity assay from parasite extracts; acetylation-specific antibodies\",\n      \"journal\": \"Antimicrobial agents and chemotherapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay plus cell-based readout with site-specific antibodies, single lab, two orthogonal methods\",\n      \"pmids\": [\"17145789\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Genome-wide ChIP-chip analysis shows that PfGCN5 is distributed across the P. falciparum genome with a chromosomal distribution similar to H3K9ac but distinct from H3K9me3. PfGCN5 occupancy is enriched at promoter regions of actively expressed genes in a stage-specific manner, and treatment with a PfGCN5 inhibitor reduces promoter H3K9ac and gene expression, establishing that PfGCN5 mediates H3K9ac at promoters to activate transcription.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP) coupled with DNA microarray (ChIP-chip); real-time PCR; HAT inhibitor treatment\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide ChIP-chip with stage-specific validation and pharmacological inhibitor confirmation, multiple orthogonal methods\",\n      \"pmids\": [\"17449656\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Anacardic acid reversibly and non-competitively inhibits HAT activity of recombinant PfGCN5 and to a lesser extent PfGCN5 in parasite nuclear extracts, without affecting histone deacetylase activity. This causes hypoacetylation of H3K9 and H3K14 (but not H4K5/K8/K12/K16) and ChIP shows reduced acetylation near promoters of downregulated genes.\",\n      \"method\": \"In vitro HAT assay; nuclear extract HAT assay; ChIP with real-time PCR; acetylation-specific antibodies; microarray\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic characterization plus cell-based ChIP and transcriptomic confirmation, multiple orthogonal methods in a single study\",\n      \"pmids\": [\"18487348\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PfGCN5 is recruited to the enhancer region of the pf1-cys-prx gene specifically during trophozoite/schizont stages, as shown by ChIP, correlating with elevated histone acetylation and stage-specific transcriptional activity.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP); reporter assay; electrophoretic mobility shift assay (EMSA); DNase I footprinting\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating recruitment with functional correlation, single lab, single gene focus\",\n      \"pmids\": [\"18692528\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Quantitative proteomic interaction studies identify two distinct GCN5/ADA2 complexes in P. falciparum, revealing the composition of PfGCN5-containing epigenetic complexes and their interactions with other epigenetic regulatory complexes.\",\n      \"method\": \"Histone peptide pull-downs; quantitative proteomics (mass spectrometry); tagging and interaction proteomics\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based interactome proteomics identifying complex composition, single study\",\n      \"pmids\": [\"31728527\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PfGCN5 undergoes novel proteolytic processing by a cysteine protease-like enzyme that is essential for its activity in vivo. The processing occurs near the digestive vacuole following trafficking through the ER-Golgi secretory pathway before PfGCN5 reaches the nucleus. Blocking processing reduces PfGCN5 occupancy at gene promoters and lowers H3K9ac at those promoters.\",\n      \"method\": \"Immunofluorescence; immuno-electron microscopy; cysteine protease inhibitor treatment; ChIP; fractionation\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — localization by IFA and immuno-EM with functional consequence shown by ChIP, single lab, multiple imaging methods\",\n      \"pmids\": [\"31862795\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PfGCN5 forms a divergent HAT complex in P. falciparum that includes two plant homeodomain (PHD) proteins (PfPHD1 and PfPHD2) and an AP2-domain transcription factor (PfAP2-LT). Deletion of the bromodomain of PfGCN5 or the PHD domain of PfPHD1 reduces merozoite invasion of erythrocytes, elevates sexual conversion, decreases H3K9 acetylation and H3K4 trimethylation, and disrupts global transcription including mutually exclusive var gene expression.\",\n      \"method\": \"CRISPR-based domain deletion; phenotypic assays (invasion, sexual conversion); RNA-seq; ChIP-seq; immunoprecipitation/proteomics\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic domain deletions with multiple orthogonal phenotypic and chromatin readouts, replicated across two subunit deletions in a single rigorous study\",\n      \"pmids\": [\"34403450\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ChIP-seq shows PfGCN5 binds to stress-responsive genes (including those involved in artemisinin resistance such as BiP and TRiC chaperone) in a poised state under normal conditions, and genome-wide PfGCN5 binding sites increase upon artemisinin exposure. Inhibition of PfGCN5 increases sensitivity of artemisinin-resistant parasites to artemisinin.\",\n      \"method\": \"ChIP-seq; pharmacological inhibition of PfGCN5; growth assay/drug sensitivity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP-seq with functional pharmacological validation, single lab\",\n      \"pmids\": [\"33441725\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PfGCN5 interacts with and acetylates PfGAPDH (glyceraldehyde-3-phosphate dehydrogenase) in vitro. Immunoprecipitation coupled with mass spectrometry identifies various metabolic enzymes as PfGCN5 interacting partners, suggesting a role beyond histone acetylation.\",\n      \"method\": \"Immunoprecipitation coupled with mass spectrometry; in vitro acetylation assay\",\n      \"journal\": \"Journal of biosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro acetyltransferase assay plus MS-based interactome, single lab, single study\",\n      \"pmids\": [\"31965989\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A co-crystal structure of the bromodomain inhibitor L-45 (L-Moses) with the PfGCN5 bromodomain was solved, rationalizing the high selectivity of the compound for PCAF and GCN5 bromodomains.\",\n      \"method\": \"X-ray co-crystallography; biophysical characterization\",\n      \"journal\": \"Angewandte Chemie (International ed. in English)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — crystal structure of the bromodomain with bound inhibitor, but mechanistic functional validation in parasites was not the focus of this paper; single study\",\n      \"pmids\": [\"27966810\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PfGCN5 bromodomain directly binds diacetylated histone H2A.Z (at K4 and K11) with a Kd of ~650 µM, as determined by NMR-based biophysical assays.\",\n      \"method\": \"Protein-observed 19F NMR (PrOF NMR); Carr-Purcell-Meiboom-Gill NMR; photo-cross-linking\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — binding detected by NMR with very low affinity (650 µM), no functional validation in parasites, single study\",\n      \"pmids\": [\"28771339\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Conditional knockdown of PfGCN5 to ~50% sensitizes P. falciparum to heat shock, glucose starvation, and dihydroartemisinin. RNA-seq identifies ~300-400 PfGCN5-dependent genes involved in stress responses, including ART-resistance-related genes K13 and coronin. KD or inhibition of PfGCN5 sensitizes ART-resistant parasites to DHA treatment.\",\n      \"method\": \"TetR-DOZI conditional knockdown; RNA-seq; ring-stage survival assay; pharmacological inhibition\",\n      \"journal\": \"Antimicrobial agents and chemotherapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic knockdown with transcriptomic readout replicated across multiple stress conditions and validated by pharmacological inhibition, single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"37702516\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Falcipain 3 (FP3), a food vacuolar cysteine protease, directly interacts with PfGCN5 as shown by co-immunoprecipitation and in vitro pull-down assay. Use of the cysteine protease inhibitor E64d blocks proteolytic processing of PfGCN5 and causes co-localization of PfGCN5 and FP3 around the food vacuole, identifying FP3 as the protease responsible for PfGCN5 processing.\",\n      \"method\": \"Co-immunoprecipitation followed by LC-MS/MS; in vitro pull-down assay; cysteine protease inhibitor treatment; confocal and electron microscopy\",\n      \"journal\": \"Biotechnology and applied biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pulldown and IP with inhibitor-based functional validation and colocalization imaging, single lab\",\n      \"pmids\": [\"38924147\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PfGCN5 is essential for parasite survival in human blood and transmission to mosquitoes. Its bromodomain (BRD) is required at euchromatic gene promoters for proper expression and for acetylation of the variant histone PfH2B.Z. Loss of the BRD de-represses heterochromatic genes and increases acetylated PfH2B.Z in heterochromatin, indicating PfGCN5 maintains repressive heterochromatin structure. The BRD-binding compound L-45 phenocopies BRD deletion.\",\n      \"method\": \"Conditional genetic knockdown/deletion; ChIP-seq; histone modification profiling; drug treatment phenocopy; gametocyte/mosquito transmission assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic deletion with multiple chromatin readouts (ChIP-seq, histone modification), phenocopy by chemical probe, and functional assay across multiple life stages in a single rigorous study\",\n      \"pmids\": [\"40156869\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PfGCN5 acetylates PfPGM1 (phosphoglycerate mutase 1) at K100, a residue critical for PfPGM1 catalytic activity, stabilizing the protein. Additionally, PfGCN5 occupies the PfPGM1 promoter in a stage-specific manner, and knockdown of PfGCN5 reduces PfPGM1 transcript levels, demonstrating dual regulation of a glycolytic enzyme at both the protein and transcriptional levels.\",\n      \"method\": \"In vitro acetylation assay; knockdown with cycloheximide treatment; ChIP; RT-PCR/transcriptomics\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro acetyltransferase assay plus ChIP and KD-based transcriptional readout, two orthogonal mechanistic approaches, single lab\",\n      \"pmids\": [\"40567037\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Conditional knockdown of PfGCN5 phenotypically recapitulates bromodomain deletion growth defects. CUT&Tag-seq shows PfGCN5 co-localizes with H3K9ac at gene promoters, and the H3K9ac peak intensity positively correlates with levels of gene expression. PfGCN5 chromatin positions overlap with DNA sequence motifs recognized by multiple AP2 transcription factors, indicating AP2-domain TFs recruit PfGCN5 to target promoters. PfGCN5 co-localizes with AP2-LT, confirming AP2-LT as a component of the PfGCN5 complex.\",\n      \"method\": \"TetR-DOZI conditional knockdown; CUT&Tag-seq; motif analysis; colocalization analysis\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KD phenocopy combined with CUT&Tag-seq chromatin mapping and motif-based recruitment evidence, multiple orthogonal approaches in a single study\",\n      \"pmids\": [\"40558503\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The poly-asparagine repeat-containing N-terminus of PfGCN5 associates with its C-terminal catalytic domain after proteolytic cleavage in the nucleus. Deletion of the poly-asparagine repeat destabilizes the N-terminal polypeptide, impairs parasite development and growth (especially under stress), and profoundly reduces acetylation of histones H3, H3.3, and H4, demonstrating that the poly-asparagine repeat contributes to PfGCN5 acetyltransferase activity in vivo.\",\n      \"method\": \"Genetic deletion; high-resolution mass spectrometry; western blotting; growth and stress assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic deletion with MS-based histone modification profiling, single lab, two orthogonal methods\",\n      \"pmids\": [\"42323337\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PfGCN5 (PF3D7_0823300) is an essential histone acetyltransferase that preferentially acetylates histone H3 at K9 and K14 (and to some extent K8) using a conserved catalytic HAT domain and a bromodomain that binds acetylated histones; it is recruited to euchromatic gene promoters by AP2-domain transcription factors to deposit H3K9ac and activate transcription, while also maintaining repressive heterochromatin structure via its bromodomain; it exists in a divergent SAGA-like complex together with PfADA2, two PHD-finger proteins (PfPHD1/PfPHD2), and the AP2-LT transcription factor; beyond histones, it acetylates non-histone substrates including PfGAPDH and PfPGM1; it undergoes essential proteolytic processing by the food vacuolar cysteine protease Falcipain 3 before reaching the nucleus; its poly-asparagine N-terminus associates with the C-terminal catalytic domain after cleavage and contributes to acetyltransferase activity; it is required for erythrocyte invasion, virulence gene (var) regulation, stress responses, and parasite transmission to mosquitoes, making it a validated antimalarial drug target.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_0823300 (GCN5) is an essential histone acetyltransferase that couples chromatin acetylation to stage-specific transcriptional programs in Plasmodium falciparum [#0, #5, #17]. Its conserved HAT domain preferentially acetylates histone H3 at K9 and K14 (and to a lesser extent K8), a specificity retained across the divergent P. falciparum H3 N-terminus and validated by functional complementation of a yeast GCN5 deletion [#0, #3]. Genome-wide, GCN5 occupancy tracks H3K9ac and is enriched at promoters of actively transcribed genes, where its deposition of H3K9ac activates transcription; H3K9ac peak intensity correlates positively with expression level [#5, #19]. GCN5 is recruited to target promoters by AP2-domain transcription factors, whose binding motifs coincide with GCN5 chromatin positions, and it co-localizes with AP2-LT [#19]. It acts within a divergent SAGA-like complex containing PfADA2, the PHD-finger proteins PfPHD1/PfPHD2, and PfAP2-LT [#1, #2, #8, #10]. Through its bromodomain GCN5 also acetylates the variant histone PfH2B.Z and maintains repressive heterochromatin: bromodomain loss de-represses heterochromatic and var genes, impairs erythrocyte invasion, and elevates sexual conversion [#10, #17]. GCN5 additionally acts on non-histone substrates, acetylating and stabilizing the glycolytic enzymes PfGAPDH and PfPGM1 while also transcriptionally regulating PfPGM1 [#12, #18]. Before nuclear function, GCN5 is proteolytically processed near the food vacuole by the cysteine protease Falcipain 3, a step essential for its promoter occupancy and H3K9ac activity, after which its poly-asparagine N-terminus reassociates with the catalytic domain to support acetyltransferase activity [#9, #16, #20]. GCN5 governs stress responses and artemisinin resistance and is required for blood-stage survival and mosquito transmission, making it a validated antimalarial target with a bromodomain amenable to selective inhibition [#5, #11, #15, #17].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing that the Plasmodium enzyme was a bona fide, catalytically conserved histone acetyltransferase answered whether P. falciparum possesses functional chromatin-modifying machinery of the GCN5 type.\",\n      \"evidence\": \"In vitro HAT assay on free core histones with site-specific antibodies plus rescue of a yeast GCN5 deletion by the PfGCN5 HAT domain\",\n      \"pmids\": [\"15075257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate mapping in vitro on free histones does not establish nucleosomal specificity\", \"In vivo genomic targets not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identifying PfADA2 as a physical partner answered whether GCN5 operates within a multi-subunit adaptor complex rather than alone.\",\n      \"evidence\": \"Yeast two-hybrid and in vitro binding assays; reciprocal co-immunoprecipitation of a ~200 kDa HAT-active species from parasite lysate\",\n      \"pmids\": [\"15075257\", \"15246536\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Full complex composition not resolved\", \"Stoichiometry and functional role of ADA2 in activity untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Refining the substrate profile to H3K9 and H3K14 on the divergent P. falciparum H3 clarified the physiologically relevant acetylation marks despite the parasite's atypical H3 N-terminus.\",\n      \"evidence\": \"In vitro HAT assays with recombinant PfH3 and native PfGCN5, read out with acetylation-specific antibodies\",\n      \"pmids\": [\"16410041\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contribution of K9 vs K14 not partitioned\", \"Non-histone substrates not yet examined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Genome-wide mapping and pharmacological inhibition established that GCN5 deposits promoter H3K9ac to activate transcription in a stage-specific manner, linking the enzyme to active euchromatin.\",\n      \"evidence\": \"ChIP-chip of GCN5 versus H3K9ac/H3K9me3, HAT inhibitor treatment with expression and ChIP readouts; anacardic acid and curcumin inhibition confirming substrate-specific hypoacetylation\",\n      \"pmids\": [\"17449656\", \"18487348\", \"17145789\", \"18692528\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recruitment mechanism to specific promoters unresolved\", \"Direct versus indirect expression effects not fully separated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Interaction proteomics resolved GCN5 into two distinct GCN5/ADA2 complexes, advancing the picture from a binary partnership to defined epigenetic assemblies.\",\n      \"evidence\": \"Histone peptide pull-downs and quantitative MS-based interaction proteomics with tagging\",\n      \"pmids\": [\"31728527\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional distinction between the two complexes not tested\", \"Subunit-specific roles unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery of essential proteolytic processing near the digestive vacuole before nuclear entry revealed an unexpected post-translational maturation step required for chromatin function.\",\n      \"evidence\": \"IFA, immuno-EM, cysteine protease inhibitor treatment and ChIP showing reduced promoter occupancy and H3K9ac when processing is blocked\",\n      \"pmids\": [\"31862795\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Protease identity not established in this study\", \"Cleavage sites and trafficking route mechanism unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Detection of non-histone acetylation (PfGAPDH) and metabolic-enzyme interactions extended GCN5's role beyond chromatin into metabolic regulation.\",\n      \"evidence\": \"IP-MS interactome and in vitro acetylation assay\",\n      \"pmids\": [\"31965989\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological consequence of GAPDH acetylation untested\", \"In vivo acetylation sites not mapped\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Genetic domain deletions defined a divergent GCN5 HAT complex with PHD proteins and AP2-LT and demonstrated the bromodomain's requirement for invasion, sexual conversion control, and var gene regulation.\",\n      \"evidence\": \"CRISPR bromodomain/PHD deletions with invasion, sexual-conversion, RNA-seq, ChIP-seq and interaction proteomics readouts; ChIP-seq of poised stress-gene binding with inhibitor drug-sensitivity assays\",\n      \"pmids\": [\"34403450\", \"33441725\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bromodomain reader ligand at heterochromatin not defined here\", \"Direct AP2-LT recruitment mechanism not yet shown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Structural and biophysical characterization of the bromodomain, including inhibitor co-crystallography, established it as a druggable acetyl-lysine reader module.\",\n      \"evidence\": \"X-ray co-crystal structure with inhibitor L-45; NMR binding to diacetylated H2A.Z\",\n      \"pmids\": [\"27966810\", \"28771339\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"H2A.Z binding is very low affinity (~650 µM) with no parasite functional validation\", \"In vivo bromodomain ligand not confirmed by these assays\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Conditional knockdown established GCN5 as a controller of stress-response transcription and a modifier of artemisinin resistance, giving direct causal genetic evidence for its role.\",\n      \"evidence\": \"TetR-DOZI knockdown to ~50% with RNA-seq, ring-stage survival assays under heat/glucose/DHA stress and pharmacological inhibition\",\n      \"pmids\": [\"37702516\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Partial knockdown may underestimate essential functions\", \"Direct GCN5 targets among stress genes not fully separated from downstream effects\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of Falcipain 3 as the processing protease closed the mechanistic gap on GCN5's essential proteolytic maturation.\",\n      \"evidence\": \"Co-IP/LC-MS/MS, in vitro pull-down, E64d inhibition blocking processing, and confocal/EM co-localization at the food vacuole\",\n      \"pmids\": [\"38924147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Precise cleavage sites not mapped\", \"Reconstitution of cleavage with purified FP3 not shown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Combined genetic deletion, chromatin mapping, and chemical phenocopy established that GCN5 both activates euchromatic promoters and maintains repressive heterochromatin through its bromodomain, and is required across blood and transmission stages.\",\n      \"evidence\": \"Conditional deletion, ChIP-seq/CUT&Tag-seq, histone-modification profiling of PfH2B.Z, AP2-motif overlap and AP2-LT co-localization, transmission assays, and L-45 phenocopy\",\n      \"pmids\": [\"40156869\", \"40558503\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical demonstration that AP2 TFs recruit GCN5 not fully resolved\", \"Mechanism coupling bromodomain to heterochromatin repression not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Dual regulation of the glycolytic enzyme PfPGM1 (acetylation at catalytic K100 plus promoter occupancy) demonstrated that GCN5 integrates protein-level and transcriptional control of metabolism.\",\n      \"evidence\": \"In vitro acetylation, cycloheximide-chase stability, ChIP and RT-PCR/transcriptomics\",\n      \"pmids\": [\"40567037\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological impact on glycolytic flux not measured\", \"In vivo K100 acetylation stoichiometry unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrating that the poly-asparagine N-terminus reassociates with the catalytic domain after cleavage and supports activity clarified the functional purpose of GCN5's processing and its low-complexity region.\",\n      \"evidence\": \"Genetic deletion of the poly-asparagine repeat with high-resolution MS histone profiling, western blotting and growth/stress assays\",\n      \"pmids\": [\"42323337\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of N-/C-domain reassociation not resolved\", \"How the repeat enhances catalysis mechanistically unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How AP2-domain transcription factors physically recruit GCN5 to specific promoters, and how a single bromodomain simultaneously drives euchromatic activation and heterochromatic repression, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct biochemical reconstitution of AP2-mediated GCN5 recruitment\", \"Dual euchromatin/heterochromatin bromodomain mechanism undefined\", \"In vivo acetyl-lysine ligand of the bromodomain not conclusively established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004402\", \"supporting_discovery_ids\": [0, 3, 6, 18, 20]},\n      {\"term_id\": \"GO:0043966\", \"supporting_discovery_ids\": [3, 5, 6, 19]},\n      {\"term_id\": \"GO:0070577\", \"supporting_discovery_ids\": [13, 14, 17]},\n      {\"term_id\": \"GO:0018393\", \"supporting_discovery_ids\": [12, 18]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 9, 20]},\n      {\"term_id\": \"GO:0000785\", \"supporting_discovery_ids\": [5, 17, 19]},\n      {\"term_id\": \"GO:0020020\", \"supporting_discovery_ids\": [9, 16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0045893\", \"supporting_discovery_ids\": [5, 7, 19]},\n      {\"term_id\": \"GO:0006338\", \"supporting_discovery_ids\": [5, 10, 17]},\n      {\"term_id\": \"GO:0006325\", \"supporting_discovery_ids\": [10, 17]},\n      {\"term_id\": \"GO:0006950\", \"supporting_discovery_ids\": [11, 15]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [10, 17]}\n    ],\n    \"complexes\": [\n      \"Divergent SAGA-like GCN5/ADA2 HAT complex (PfADA2)\",\n      \"GCN5-PfPHD1/PfPHD2-PfAP2-LT complex\",\n      \"Two distinct GCN5/ADA2 complexes resolved by interaction proteomics\"\n    ],\n    \"partners\": [\n      \"PfADA2\",\n      \"PfPHD1\",\n      \"PfPHD2\",\n      \"PfAP2-LT (AP2-domain transcription factor)\",\n      \"Falcipain 3 (FP3, food vacuolar cysteine protease)\",\n      \"PfGAPDH (acetylation substrate)\",\n      \"PfPGM1 (acetylation substrate, K100)\"\n    ],\n    \"other_free_text\": [\n      \"Preferentially acetylates histone H3 at K9 and K14 (and to a lesser extent K8); HAT domain complements yeast GCN5 deletion.\",\n      \"Bromodomain binds acetyl-lysine and acetylates variant histone PfH2B.Z; loss de-represses heterochromatic and var genes.\",\n      \"Undergoes essential proteolytic processing by Falcipain 3 near the food vacuole after ER-Golgi trafficking before nuclear function.\",\n      \"Poly-asparagine N-terminus reassociates with the C-terminal catalytic domain after cleavage and supports acetyltransferase activity.\",\n      \"Recruited to promoters coincident with AP2 transcription factor DNA motifs; H3K9ac peak intensity correlates with expression.\",\n      \"Inhibited by curcumin, anacardic acid, and the bromodomain probe L-45 (L-Moses); bromodomain co-crystal structure solved.\",\n      \"Required for erythrocyte invasion, var gene mutual exclusion, stress responses, artemisinin-resistance modulation, blood-stage survival, and mosquito transmission; validated antimalarial target.\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0823300","name":null,"product":"histone acetyltransferase GCN5","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0707300","name":null,"product":"histone acetyltransferase GCN5, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1317300","name":null,"product":"histone acetyltransferase GCN5, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"GCN5","evaluation":null}