Affinage · Plasmodium

PF3D7_0320900

histone H2A.Z

Annotated
2026-09-07
18 papers in source corpus 13 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

In Plasmodium falciparum, H2A.Z is a variant histone that serves as a constitutive scaffold marking euchromatic intergenic and promoter regions throughout the intraerythrocytic cycle, where it almost perfectly colocalizes with the active marks H3K9ac and H3K4me3 and provides a platform for assembly of transcription-related complexes (PMID:21187892, PMID:21379342). Within these nucleosomes H2A.Z dimerizes with the apicomplexan-specific variant H2B.Z to form double-variant nucleosomes that carry euchromatic acetylation and H3K4me3 and are enriched at promoters, with occupancy correlating with promoter strength (PMID:23373537, PMID:23320541). Deposition of the H2A.Z/H2B.Z pair at activated promoters is carried out by the PfSWR1 chromatin remodeling complex, and PfArp4 is required for H2A.Z deposition and the associated H3K9ac at euchromatic gene upstream regions (PMID:38564734, PMID:32552779). The acetylation state of H2A.Z is dynamically linked to promoter activity genome-wide and is antagonized by PfSir2 deacetylases at boundaries between active and silent chromatin (PMID:37882786, PMID:21379342), and its multi-acetylated form is recognized by the PfBDP1 bromodomain (PMID:36328269, PMID:33225957). At var gene promoters, H2A.Z/H2B.Z enrichment at the transcription start site occurs specifically at the single active copy in a developmentally regulated manner, linking histone variant exchange to mutually exclusive var gene expression (PMID:21379342, PMID:23373537, PMID:23320541). Beyond euchromatin, H2A.Z co-occupies centromeric chromatin alongside PfCENH3 (PMID:22507744), modulates PfHP1 phase separation in vitro (PMID:41871101), and in female gametocytes adopts an unusual heterochromatic state enriched in H3K9me3-associated regions (PMID:37013531).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2006 Medium

    Establishing that P. falciparum encodes and expresses H2A.Z with a distinctive PTM pattern was the first step in defining it as a functional variant histone distinct from canonical histones.

    Evidence Mass spectrometry, RT-PCR, and immunoblotting mapping H2A.Z modifications and stage-specific expression

    PMID:16410041

    Open questions at the time
    • Functional consequence of the identified lysine modifications not determined
    • No genome-wide localization at this stage
  2. 2010 High

    Genome-wide mapping resolved where H2A.Z acts, showing it constitutively marks euchromatic intergenic regions and colocalizes with active histone marks, establishing it as a stable epigenetic platform rather than a dynamic mark itself.

    Evidence ChIP-seq across intraerythrocytic development combined with RNA-seq at eight time-points

    PMID:21187892

    Open questions at the time
    • Whether H2A.Z deposition is cause or consequence of active marks not resolved
    • Depositing machinery not identified
  3. 2011 High

    Correlating H2A.Z occupancy with var gene activity connected histone variant exchange to mutually exclusive var expression and identified PfSir2A as an antagonist, linking a chromatin variant to antigenic variation.

    Evidence ChIP-seq, reciprocal ChIP with H3K4me3, and Sir2A/Sir2B knockout analysis

    PMID:21379342

    Open questions at the time
    • Mechanism of stage-specific H2A.Z exchange at var promoters not defined
    • Direct role in switching versus maintenance not distinguished
  4. 2012 Medium

    Mapping H2A.Z within PfCENH3-occupied centromeres extended its role beyond gene regulation into genome organization.

    Evidence ChIP-seq co-localization of H2A.Z and PfCENH3 across all chromosomes

    PMID:22507744

    Open questions at the time
    • Mechanistic consequence of centromeric H2A.Z not established
    • Whether H2A.Z contributes to kinetochore function unknown
  5. 2013 High

    Demonstrating that H2A.Z physically dimerizes with the apicomplexan-specific H2B.Z defined a novel double-variant nucleosome as the functional unit marking euchromatic promoters.

    Evidence Co-immunoprecipitation showing H2A.Z–H2B.Z dimerization plus genome-wide ChIP-seq, independently replicated across two studies

    PMID:23320541 PMID:23373537

    Open questions at the time
    • Structural basis of the double-variant nucleosome not resolved
    • Why occupancy correlates with promoter strength but not temporal activity unexplained
  6. 2020 Medium

    Integrating H2A.Z with additional acetyl marks, PfAP2-I, and PfBDP1, and testing regulatory activity, positioned H2A.Z-marked sites as functional promoters read by defined factors.

    Evidence ChIP-seq colocalization with H3K18ac/H3K27ac, PfAP2-I and PfBDP1, plus transient transfection promoter assays

    PMID:33225957

    Open questions at the time
    • Distinction from enhancer function not fully explained
    • Causal requirement of H2A.Z for reader recruitment not tested
  7. 2020 Medium

    Conditional depletion of PfArp4 identified an upstream regulator required for H2A.Z deposition, providing the first genetic handle on the machinery that places H2A.Z.

    Evidence glmS ribozyme knockdown with ChIP-seq, RNA-seq, co-IFA and co-IP

    PMID:32552779

    Open questions at the time
    • Whether PfArp4 acts directly or via a remodeler complex not resolved at the time
    • Full deposition complex composition unknown
  8. 2022 Medium

    In vitro binding assays established that multi-acetylated H2A.Z is directly recognized by the PfBDP1 bromodomain, defining a molecular reader interaction.

    Evidence Solution NMR and ITC binding assays with the PfBDP1 bromodomain crystal structure

    PMID:36328269

    Open questions at the time
    • Interaction weaker than with acetylated H4/H3, cellular relevance not quantified
    • Functional outcome of PfBDP1–H2A.Z binding in vivo not tested
  9. 2023 Medium

    Genome-wide mapping in Sir2 mutants showed H2A.Z acetylation tracks promoter activity and is antagonized by PfSir2 at active/silent boundaries, establishing acetylation of the variant as a regulatory switch.

    Evidence ChIP-seq in Sir2 knockout/knockdown parasites mapping acetylated alternative histones

    PMID:37882786

    Open questions at the time
    • Direct enzyme–substrate relationship of PfSir2 on H2A.Z not shown biochemically
    • Acetyltransferase responsible not identified
  10. 2023 Medium

    Discovering that H2A.Z/H2B.Z become heterochromatic in female gametocytes revealed a life-stage- and sex-specific reprogramming of the variant's chromatin context.

    Evidence ChIP-seq and RNA-seq on flow-sorted male and female gametocytes

    PMID:37013531

    Open questions at the time
    • Mechanism driving the euchromatin-to-heterochromatin switch unknown
    • Functional consequence for gametocyte gene expression not defined
  11. 2024 Medium

    Reciprocal pulldowns identified the PfSWR1 complex as the machinery associating with and depositing the H2A.Z/H2B.Z pair at activated promoters, completing the deposition pathway.

    Evidence Reciprocal co-IP/pulldown using PfEAF2 as bait with mass spectrometry of complex components

    PMID:38564734

    Open questions at the time
    • In vitro reconstitution of PfSWR1-mediated H2A.Z deposition not shown
    • How PfSWR1 is targeted to specific promoters not defined
  12. 2026 Medium

    In vitro reconstitution showed H2A.Z modulates PfHP1 phase separation, linking the variant to heterochromatin compartmentalization and var gene silencing beyond its euchromatic role.

    Evidence In vitro phase separation and single-molecule DNA compaction assays, Hi-C, FRAP of GFP-PfHP1, and PfHP1 point mutagenesis

    PMID:41871101

    Open questions at the time
    • Effect demonstrated in vitro; in vivo requirement of H2A.Z for PfHP1 condensation not established
    • H2A.Z is a modulator, not the primary subject, in this assay

Open questions

Synthesis pass · forward-looking unresolved questions
  • How H2A.Z occupancy and acetylation are dynamically read out to enforce a single active var gene, and how the same variant is redirected to heterochromatin in female gametocytes, remain the central open mechanistic questions.
  • No structural model of the P. falciparum H2A.Z/H2B.Z nucleosome
  • Direct causal test of H2A.Z removal on var switching lacking
  • Signals controlling stage- and sex-specific chromatin context of H2A.Z unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
H2B.Z (DIMERIZATION PARTNER)PFAP2-I (CO-LOCALIZING TRANSCRIPTION FACTOR)PFARP4 (DEPOSITION REGULATOR)PFBDP1 BROMODOMAIN (READER OF ACETYLATED H2A.Z)PFCENH3 (CENTROMERIC CO-OCCUPANCY)PFHP1 (PHASE SEPARATION MODULATION)PFSIR2 / PFSIR2A (DEACETYLASE ANTAGONIST)PFSWR1 / PFEAF2 (DEPOSITION COMPLEX)
Complex memberships
H2A.Z/H2B.Z double-variant nucleosomePfSWR1 chromatin remodeling complex (association)

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2010 H2A.Z is a constant, ubiquitous feature of euchromatic intergenic regions throughout the intraerythrocytic cycle in P. falciparum, and almost perfectly colocalizes with H3K9ac and H3K4me3, suggesting these marks are preferentially deposited on H2A.Z-containing nucleosomes. H2A.Z stably defines intergenic regions and provides a platform for dynamic assembly of epigenetic and transcription-related complexes. Genome-wide ChIP-seq (next-generation sequencing with linear amplification method) across intraerythrocytic development, combined with RNA-seq at 8 time-points PLoS pathogens High 21187892
2006 Mass spectrometry identified a novel pattern of lysine modifications on H2A.Z in P. falciparum. The variant histone H2A.Z is encoded in the P. falciparum genome and its expression decreases in mid- or late trophozoite stages, in contrast to canonical histones which peak at late trophozoite. Mass spectrometry, real-time RT-PCR, immunoblotting Gene Medium 16410041
2011 H2A.Z colocalizes with histone modifications characteristic of transcriptionally permissive euchromatin (H3K4me3) but not heterochromatin markers. H2A.Z is enriched at transcription start sites (TSS) of both active and silent stage-specific genes, but at var gene promoters H2A.Z enrichment at the TSS occurs only during active transcription in ring stage, indicating that temporal var gene regulation involves histone variant exchange at promoter nucleosomes. PfSir2A antagonizes H2A.Z occupancy at active var promoters during intraerythrocytic development. ChIP-seq, ChIP (co-precipitating H3K4me3 with H2A.Z antibodies), Sir2A/Sir2B knockout parasite analysis PLoS pathogens High 21379342
2013 Within nucleosomes, H2A.Z dimerizes with the apicomplexan-specific histone variant H2B.Z, forming double-variant nucleosomes. These H2A.Z/H2B.Z double-variant nucleosomes are enriched in intergenic (promoter) regions across the genome and carry euchromatin markers (H3K4me3 and histone acetylation). At var genes, H2A.Z/H2B.Z double-variant nucleosomes are enriched only at the promoter of the single active var copy in a developmentally regulated manner. ChIP-seq, co-immunoprecipitation (demonstrating H2A.Z–H2B.Z dimerization within nucleosomes) Molecular microbiology High 23320541 23373537
2013 H2A.Z and H2B.Z together form a double-variant nucleosome subtype that localizes to euchromatic intergenic (promoter) regions throughout intraerythrocytic development. H2A.Z/H2B.Z occupancy is enriched in promoters over 3' intergenic regions and generally correlates with promoter strength but not with its temporal activity. H2B.Z occupancy exhibits a clear correlation with the AT content of the underlying DNA sequence. ChIP-seq genome-wide analysis, co-localization analysis Molecular microbiology High 23320541
2012 H2A.Z is present within centromeric regions (4–4.5 kb) of all P. falciparum chromosomes that are occupied by the centromeric histone PfCENH3, indicating that H2A.Z co-occupies centromeric chromatin alongside PfCENH3. ChIP-seq mapping of PfCENH3 and H2A.Z genome-wide Cellular microbiology Medium 22507744
2020 H2A.Z colocalizes with H3K18ac and H3K27ac at regulatory sites upstream of genes and co-localizes with transcription factor PfAP2-I and bromodomain protein PfBDP1 at stably positioned nucleosomes within regions of exposed DNA at active transcriptional start sites in schizont stages. Sequences enriched with colocalized H3K18ac, H3K27ac, and H2A.Z possess promoter activity in schizont stages but no enhancer-like activity, as demonstrated by transient transfection assays. ChIP-seq, transient transfection promoter assays, integration with existing ChIP-seq datasets Epigenetics & chromatin Medium 33225957
2020 PfArp4, an actin-related protein, co-localizes with H2A.Z and the euchromatic marker H3K9ac in intergenic regions. Inducible knockdown of PfArp4 results in depletion of H2A.Z and reduced H3K9ac levels at upstream regions of euchromatic genes, repressing the transcriptional abundance of H2A.Z-dependent genes. This implicates PfArp4 as a regulator of H2A.Z deposition. Conditional glmS ribozyme knockdown, ChIP-seq, RNA-seq, co-IFA, co-IP Parasites & vectors Medium 32552779
2022 The PfBDP1 bromodomain interacts with multi-acetylated H2A.Z (detected by solution NMR spectroscopy and ITC binding assays), though this interaction is weaker than with tetra-acetylated H4 or acetylated H3. Solution NMR spectroscopy, isothermal titration calorimetry (ITC), crystal structure of PfBDP1 bromodomain International journal of biological macromolecules Medium 36328269
2023 PfSir2 histone deacetylases antagonize acetylated H2A.Z at boundaries between active and silent DNA. Acetylation of H2A.Z at promoters is dynamically associated with promoter activity across the genome, implicating acetylation of H2A.Z in genome-wide gene regulation. ChIP-seq with Sir2 knockout/knockdown parasites, genome-wide mapping of acetylated alternative histones mBio Medium 37882786
2023 In female gametocytes, H2A.Z and H2B.Z are highly enriched in H3K9me3-associated heterochromatin, representing a sex-specific chromatin state distinct from asexual parasites where H2A.Z/H2B.Z are euchromatic. ChIP-seq after flow-cytometry separation of male and female gametocytes, RNAseq BMC biology Medium 37013531
2024 H2A.Z and H2B.Z were found associated with the PfSWR1 complex by reciprocal pulldown experiments, indicating that the PfSWR1 chromatin remodeling complex is responsible for the deposition of the H2A.Z/H2B.Z variant histone pair at activated promoters. Reciprocal co-immunoprecipitation/pulldown (using PfEAF2 as bait), mass spectrometry identification of complex components mSphere Medium 38564734
2026 PfH2A.Z modulates PfHP1 phase separation in vitro; specifically, PfH2A.Z tunes the phase separation behavior of PfHP1 (P. falciparum heterochromatin protein 1), which compartmentalizes DNA and mediates var gene silencing. In vitro phase separation assays, single-molecule DNA compaction assays, Hi-C, FRAP of GFP-PfHP1 parasites, point mutagenesis of PfHP1 Cell reports Medium 41871101

Source papers

Stage 0 corpus · 18 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 H2A.Z demarcates intergenic regions of the plasmodium falciparum epigenome that are dynamically marked by H3K9ac and H3K4me3. PLoS pathogens 180 21187892
2006 The malaria parasite Plasmodium falciparum histones: organization, expression, and acetylation. Gene 155 16410041
2011 Expression of P. falciparum var genes involves exchange of the histone variant H2A.Z at the promoter. PLoS pathogens 87 21379342
2013 H2A.Z and H2B.Z double-variant nucleosomes define intergenic regions and dynamically occupy var gene promoters in the malaria parasite Plasmodium falciparum. Molecular microbiology 67 23373537
2012 Plasmodium falciparum centromeres display a unique epigenetic makeup and cluster prior to and during schizogony. Cellular microbiology 61 22507744
2013 H2A.Z/H2B.Z double-variant nucleosomes inhabit the AT-rich promoter regions of the Plasmodium falciparum genome. Molecular microbiology 58 23320541
2020 Histone modifications associated with gene expression and genome accessibility are dynamically enriched at Plasmodium falciparum regulatory sequences. Epigenetics & chromatin 34 33225957
2023 Plasmodium falciparum gametocytes display global chromatin remodelling during sexual differentiation. BMC biology 18 37013531
2010 Plasmodium falciparum Tudor Staphylococcal Nuclease interacting proteins suggest its role in nuclear as well as splicing processes. Gene 15 20713134
2021 Phosphorylation of the Canonical Histone H2A Marks Foci of Damaged DNA in Malaria Parasites. mSphere 12 33441412
2022 Structural insights into acetylated histone ligand recognition by the BDP1 bromodomain of Plasmodium falciparum. International journal of biological macromolecules 10 36328269
2020 Actin-related protein Arp4 regulates euchromatic gene expression and development through H2A.Z deposition in blood-stage Plasmodium falciparum. Parasites & vectors 10 32552779
1999 Differential transcription of histone genes in asexual and sexual stages of Plasmodium falciparum. International journal for parasitology 10 10579431
2023 The P. falciparum alternative histones Pf H2A.Z and Pf H2B.Z are dynamically acetylated and antagonized by PfSir2 histone deacetylases at heterochromatin boundaries. mBio 8 37882786
2003 The histone H4 gene of Plasmodium falciparum is developmentally transcribed in asexual parasites. Parasitology research 7 12739134
2024 MYST regulates DNA repair and forms a NuA4-like complex in the malaria parasite Plasmodium falciparum. mSphere 4 38564734
2026 Phase separation of heterochromatin protein 1 regulates virulence gene expression in Plasmodium falciparum. Cell reports 0 41871101
2025 Structure-function studies of a nucleoplasmin isoform from Plasmodium falciparum. The Journal of biological chemistry 0 40049416