MYST

PF3D7_1118600 (MYST) is an essential histone acetyltransferase that couples chromatin acetylation to transcriptional control, DNA replication, DNA-damage repair, and drug-response phenotypes in the P. falciparum intraerythrocytic cycle (PMID:20807207, PMID:38564734). Recombinant MYST purified from parasites acetylates histone H4 at K5, K8, K12, and K16 in vitro, and its catalytic activity is required in vivo: gene-disruption attempts fail while overexpression of active versus catalytically inactive isoforms alters global H4 acetylation and cell-cycle progression (PMID:20807207). MYST is expressed as long (~72 kDa) and short (~45 kDa) isoforms distributed between cytoplasm and nucleus, the short isoform being predominantly nuclear (PMID:20807207, PMID:36228701). Functional homology to human TIP60 was established by yeast complementation, and the TIP60 inhibitor NU9056 blocks MYST catalytic activity and arrests parasites at the trophozoite-to-schizont transition (PMID:33046499). Chromatin-level roles include occupancy of active var promoters and the subtelomeric TARE region linked to monoallelic var regulation, and stronger association than PfGCN5 with putative autonomously replicating sequences (PfARS) alongside enriched H4 acetylation and the replication factor PfORC1 (PMID:20807207, PMID:36228701, PMID:35640888). MYST assembles into a divergent NuA4-like complex (PfNuA4) containing 11 of 13 conserved subunits and interacts with PfRUVBL proteins and core histones H3/H4; upon DNA damage it translocates from cytoplasm to nucleus and colocalizes with γ-PfH2A at double-strand breaks, where its abundance controls repair kinetics and resistance to genotoxic agents and artemisinin (PMID:30026605, PMID:35640888, PMID:38564734). MYST expression level modulates artemisinin ring-stage survival, and among all P. falciparum HATs only MYST showed full association with the ring-stage survival phenotype across field isolates, with its target genes intersecting PfK13 biology (PMID:35510853, PMID:40877256).

1. 2010 High

   Establishing whether PF3D7_1118600 is a bona fide histone acetyltransferase and defining its substrate specificity was the foundational question; the in vitro assay showed it acetylates H4 at specific lysines, defining its molecular activity.

   Evidence In vitro HAT assay with recombinant protein purified from parasites versus prokaryotic/insect-cell systems

   PMID:20807207

   Open questions at the time

   • Why activity requires parasite-derived protein (post-translational modification or bound cofactor) unresolved
   • No structure of the catalytic domain
2. 2010 Medium

   Localization and isoform analysis addressed where the enzyme acts; GFP tagging showed dual nucleo-cytoplasmic distribution and two isoforms, hinting at multiple functional pools.

   Evidence C-terminal GFP tagging with live imaging and Western blot

   PMID:20807207

   Open questions at the time

   • Origin and independent function of long versus short isoforms not defined at this stage
   • No functional rescue of the tag
3. 2010 Medium

   Linking the enzyme to gene regulation, ChIP placed MYST at the active var promoter, connecting its H4 acetylation activity to active transcription.

   Evidence ChIP at active var promoter

   PMID:20807207

   Open questions at the time

   • Single method, single promoter
   • Causality between occupancy and var activation not tested
4. 2010 Medium

   Genetic essentiality and cellular consequence were tested; disruption failed while active/inactive overexpression altered H4 acetylation, cell cycle, and DNA-damage sensitivity, establishing MYST as essential and functionally coupled to genome maintenance.

   Evidence Stable overexpression, gene-disruption attempts, flow cytometry, isoform HAT comparison

   PMID:20807207

   Open questions at the time

   • Essentiality inferred from failed disruption rather than conditional knockout
   • Direct DNA-repair role not yet demonstrated
5. 2013 Medium

   Whether MYST acts beyond histones was probed; acetylome profiling with transgenic lines and inhibitors implicated it in the dynamics of cytoplasmic protein acetylation.

   Evidence Transgenic overexpression lines plus inhibitors with LC-MS/MS acetylome profiling

   PMID:23796209

   Open questions at the time

   • Direct non-histone substrates of MYST not individually validated
   • Contribution of deacetylases versus MYST not fully separated
6. 2018 Medium

   Identifying protein partners, Co-IP revealed PfRUVBL3 as a physical interactor colocalizing with H3K9me1, pointing to a chromatin-remodeling context.

   Evidence Co-immunoprecipitation and co-immunofluorescence with H3K9me1

   PMID:30026605

   Open questions at the time

   • Single Co-IP without functional reconstitution
   • Functional consequence of the MYST-RUVBL3 interaction untested
7. 2020 High

   Cross-species functional identity and druggability were established; yeast complementation defined MYST as a TIP60 homolog and the TIP60 inhibitor NU9056 blocked its activity and arrested parasites, validating it as a target.

   Evidence Yeast complementation, in vitro catalytic inhibition with NU9056, stage-specific growth assays

   PMID:33046499

   Open questions at the time

   • NU9056 selectivity for MYST over other parasite HATs not fully resolved
   • Molecular basis of trophozoite-stage arrest not defined
8. 2022 Medium

   The link to genome replication was tested; isoform-resolved ChIP showed the nuclear short isoform binds PfARS more strongly than PfGCN5 with enriched H4ac correlating with PfORC1, implicating MYST in DNA replication.

   Evidence Western blot isoform characterization and ChIP-qPCR at PfARS for MYST, GCN5, H4ac and PfORC1

   PMID:36228701

   Open questions at the time

   • Direct requirement of MYST for origin firing not demonstrated
   • Mechanism connecting H4 acetylation to PfORC1 recruitment unknown
9. 2022 Medium

   The role in antigenic variation was extended; ChIP and Co-IP showed MYST and PfRUVBL co-occupy TARE and var promoters and bind core histones H3/H4, implicating the complex in monoallelic var regulation.

   Evidence ChIP at TARE and var promoters and Co-IP with histones H3 and H4

   PMID:35640888

   Open questions at the time

   • Causal control of var monoallelic expression not perturbed genetically
   • Limited functional follow-up
10. 2022 Medium

    Whether MYST dosage modulates drug response was addressed; inducible CRISPRi/a tuning of MYST expression altered artemisinin sensitivity, linking its level to drug response.

    Evidence Inducible DiCre/loxP-controlled dCas9-GCN5/-Sir2a CRISPRi/a and artemisinin sensitivity assays

    PMID:35510853

    Open questions at the time

    • Downstream mediators of altered sensitivity not identified
    • Limited mechanistic depth
11. 2024 High

    The complex identity and DNA-repair mechanism were resolved; reciprocal pulldowns defined a NuA4-like complex (PfNuA4), and overexpression/knockdown with genotoxic challenge plus damage-induced nuclear translocation to γ-PfH2A foci established MYST as a repair-promoting, dose-dependent protective factor.

    Evidence Reciprocal Co-IP/MS via PfEAF2, overexpression and knockdown, γ-H2A immunofluorescence, live imaging, MMS/X-ray/artemisinin growth assays

    PMID:38564734

    Open questions at the time

    • Signal driving cytoplasm-to-nucleus translocation upon damage unknown
    • Which repair pathway (HR vs NHEJ) MYST acetylation promotes not defined
12. 2025 High

    Clinical relevance was established; across field isolates only MYST fully associated with ring-stage survival, and ChIP-seq/scRNA-seq/CRISPR defined its RS-related target genes and intersection with PfK13, positioning MYST in artemisinin resistance biology.

    Evidence Systematic evaluation of 30 culture-adapted and 43 subcloned field isolates, knockdown, ChIP-seq, single-cell RNA-seq, CRISPR/Cas9 validation, ring-stage survival assays

    PMID:40877256

    Open questions at the time

    • Direct molecular interplay between MYST and PfK13 not mechanistically resolved
    • Whether MYST-driven RS is causal or correlative across all isolates not fully separated

• How MYST's distinct roles in var regulation, replication-origin function, and DNA-damage repair are coordinated by isoform choice, complex composition, and damage signaling remains the central open question.
• No structure of MYST or PfNuA4
• Mechanism partitioning long versus short isoforms between functions unknown
• Direct causal link between MYST activity and artemisinin resistance mechanism unresolved