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Showing H2AJ — H2AFJ is a alias.

H2AJ

Histone H2A.J · UniProt Q9BTM1

Length
129 aa
Mass
14.0 kDa
Annotated
2026-06-10
16 papers in source corpus 6 papers cited in narrative 6 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

H2AJ (H2AFJ) encodes a replication-independent histone H2A variant whose transcript lacks the canonical histone 3'-UTR stem-loop and instead carries a poly(A) signal, distinguishing it from replication-dependent H2A genes (PMID:15720718). The variant is enriched in luminal epithelial cells across multiple glandular tissues, and its loss reduces expression of hormone-responsive genes, linking H2A.J to hormone-driven transcriptional programs (PMID:34828271). In prostate cancer it is a direct androgen receptor target—AR binds the H2AJ locus and supraphysiological androgen induces its expression—and H2AJ in turn drives proliferation, regulates androgen-induced cellular senescence and senescence-associated heterochromatin foci (SAHF) formation, and suppresses mesenchymal marker expression (PMID:40075640). A pro-proliferative role in prostate cancer cells downstream of androgen signaling is further supported by knockdown phenotypes (PMID:41120564). Beyond hormone-responsive epithelia, H2AJ promotes glioblastoma temozolomide resistance and modulates NF-κB and STAT3 transcriptional activity (PMID:31906036), and hepatocyte-derived exosomal H2AJ protein activates MAPK/c-jun/STMN1 signaling in hepatic stellate cells to drive liver fibrosis (PMID:36608439). How H2A.J nucleosome incorporation mechanistically governs these transcriptional and chromatin outputs has not been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 5 steps
  1. 2005 Medium

    Established that H2AFJ is structurally distinct from canonical replication-dependent histones, defining it as a replication-independent H2A variant rather than a cell-cycle-coupled histone.

    Evidence Quantitative RT-PCR plus bioinformatic analysis of promoter and 3'-UTR structure

    PMID:15720718

    Open questions at the time
    • No chromatin incorporation or nucleosome-level characterization
    • No functional consequence of variant identity defined
  2. 2019 Medium

    Connected H2AFJ to cancer cell survival by showing it modulates inflammatory transcription factor activity, placing it within NF-κB and STAT3 signaling outputs.

    Evidence Knockdown/overexpression in GBM cell lines with luciferase promoter reporters and GSEA

    PMID:31906036

    Open questions at the time
    • Mechanism by which a histone variant alters NF-κB/STAT3 activity not resolved
    • No direct chromatin occupancy data at target loci
  3. 2021 Medium

    Localized H2A.J to luminal epithelial cells of multiple glands and linked it to hormone-responsive gene expression, framing it as an epithelial- and hormone-associated variant.

    Evidence IHC across human and mouse tissues plus H2AFJ knockout in T47D breast cancer cells with expression analysis

    PMID:34828271

    Open questions at the time
    • Mechanism linking H2A.J to estrogen-responsive gene regulation unknown
    • No genome-wide mapping of H2A.J deposition sites
  4. 2023 Medium

    Revealed a non-canonical extracellular role: hepatocyte exosomes deliver H2AJ protein to stellate cells to drive fibrosis via MAPK/c-jun/STMN1, expanding H2AJ function beyond intracellular chromatin.

    Evidence Exosome co-culture, siRNA knockdown, MAPK inhibition, STMN1 rescue, and CCl4-induced mouse fibrosis model

    PMID:36608439

    Open questions at the time
    • How a histone is selectively packaged into exosomes is unknown
    • Whether extracellular H2AJ acts via chromatin in recipient cells is unresolved
  5. 2025 High

    Defined H2AJ as a direct androgen receptor target gene and showed it governs prostate cancer proliferation, androgen-induced senescence/SAHF, and mesenchymal marker suppression, integrating it into AR-driven epithelial chromatin programs.

    Evidence ChIP-seq, RNA-seq, ChIP-qPCR, siRNA knockdown, overexpression, and in situ histochemistry in prostate cancer cells

    PMID:40075640 PMID:41120564

    Open questions at the time
    • Whether H2AJ deposition into nucleosomes directly drives SAHF formation is not mechanistically shown
    • The PACT/androgen-to-H2AFJ regulatory link rests on a secondary low-confidence finding

Open questions

Synthesis pass · forward-looking unresolved questions
  • How H2A.J nucleosome incorporation at specific genomic loci mechanistically links to its transcriptional, senescence, and fibrotic phenotypes remains unresolved.
  • No structure of H2A.J-containing nucleosomes
  • No identified chaperone or deposition machinery
  • Genome-wide H2A.J occupancy relative to active/heterochromatin not mapped

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 2 GO:0140110 transcription regulator activity 2
Localization
GO:0005634 nucleus 2 GO:0000228 nuclear chromosome 1
Pathway
GO:0140110 transcription regulator activity 2
Partners
ARSTMN1
Complex memberships
nucleosome

Evidence

Reading pass · 6 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 H2AFJ (H2A.J) encodes a replication-independent histone H2A variant; its transcript lacks the canonical stem-loop structure at the 3'-UTR but contains a poly(A) signal, and its promoter region differs structurally from replication-dependent histone H2A genes. Quantitative RT-PCR confirmed replication-independent expression. Quantitative RT-PCR, bioinformatics (promoter and 3'-UTR analysis) BMC genetics Medium 15720718
2019 H2AFJ knockdown in GBM cell lines diminished temozolomide (TMZ) resistance, while H2AFJ overexpression promoted TMZ resistance. Luciferase-based promoter activity assays showed that H2AFJ expression causally affects NF-κB and STAT3 transcriptional activities in GBM cells, and gene set enrichment analysis linked H2AFJ upregulation to activation of TNF-α/NF-κB and IL-6/STAT3 pathways. Knockdown/overexpression in GBM cell lines, luciferase-based promoter activity assay, GSEA Cancers Medium 31906036
2021 H2A.J is enriched in luminal epithelial cells of multiple glands (breast, prostate, pancreas, thyroid, stomach, salivary glands) as determined by immunohistochemistry. Knockout of the H2AFJ gene in T47D luminal breast cancer cells reduced the expression of several estrogen-responsive genes. Immunohistochemistry (IHC) across human and mouse tissues; H2AFJ gene knockout in T47D cells with gene expression analysis Genes Medium 34828271
2023 Hepatocyte-derived exosomes deliver H2AFJ protein to hepatic stellate cells (HSCs). Exosomal H2AFJ promoted HSC migration and invasion by upregulating c-jun-mediated STMN1 through activation of the MAPK signaling pathway. In vivo silencing of H2AFJ attenuated liver fibrosis in mice, and restoration of STMN1 negated this protective effect. Exosome isolation and co-culture, siRNA knockdown, MAPK pathway inhibitor, in vivo mouse model (CCl4-induced fibrosis), migration/invasion assays International immunopharmacology Medium 36608439
2025 H2AJ is a direct androgen receptor (AR) target gene: ChIP-seq demonstrated AR binding at the H2AJ locus, and RNA-seq showed H2AJ upregulation in response to supraphysiological androgen levels (SALs). H2AJ knockdown inhibited prostate cancer cell growth, whereas H2AJ overexpression promoted growth. H2AJ regulates androgen-induced cellular senescence and formation of senescence-associated heterochromatin foci (SAHF), and inhibits expression of mesenchymal markers in prostate cancer cells. ChIP-seq, RNA-seq, ChIP-qPCR, siRNA knockdown, overexpression, qRT-PCR, immunodetection, in situ histochemistry Cancers High 40075640
2025 H2AFJ is downregulated in PACT-knockout LNCaP prostate cancer cells (as identified by RNA-seq), and siRNA-mediated knockdown of H2AFJ alone reduced cell growth and proliferation in LNCaP cells, supporting a pro-proliferative role for H2AFJ downstream of PACT/androgen signaling. RNA-seq of PACT KO cells, siRNA knockdown of H2AFJ, cell growth/proliferation assay Scientific reports Low 41120564

Source papers

Stage 0 corpus · 16 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2017 Molecular investigation of the direct anti-tumour effects of nonsteroidal anti-inflammatory drugs in a panel of canine cancer cell lines. Veterinary journal (London, England : 1997) 41 28283079
2020 MHC-II alleles shape the CDR3 repertoires of conventional and regulatory naïve CD4+ T cells. Proceedings of the National Academy of Sciences of the United States of America 39 32482872
2019 Histone 2A Family Member J Drives Mesenchymal Transition and Temozolomide Resistance in Glioblastoma Multiforme. Cancers 29 31906036
2019 Stromal Cell Signature Associated with Response to Neoadjuvant Chemotherapy in Locally Advanced Breast Cancer. Cells 27 31817155
2015 The QTL within the H2 Complex Involved in the Control of Tuberculosis Infection in Mice Is the Classical Class II H2-Ab1 Gene. PLoS genetics 23 26618355
2023 Hepatocyte-derived exosomes deliver H2AFJ to hepatic stellate cells and promote liver fibrosis via the MAPK/STMN1 axis activation. International immunopharmacology 13 36608439
2005 A novel replication-independent histone H2a gene in mouse. BMC genetics 12 15720718
2021 Histone Variant H2A.J Is Enriched in Luminal Epithelial Gland Cells. Genes 9 34828271
2015 Dual effects of human adipose tissue-derived mesenchymal stem cells in human lung adenocarcinoma A549 xenografts and colorectal adenocarcinoma HT-29 xenografts in mice. Oncology reports 9 26252638
2023 High-throughput proteomic characterization of seminal plasma from bulls with contrasting semen quality. 3 Biotech 8 36714547
2022 Development and validation of a 13-gene signature associated with immune function for the detection of Alzheimer's disease. Neurobiology of aging 8 36842362
2021 Prioritising breast cancer theranostics: A current medical longing in oncology. Cancer treatment and research communications 8 34598060
2023 Upregulation of the Oct3/4 Network in Basal Breast Cancer Is Associated with Its Metastatic Potential and Shows Tissue Dependent Variability. International journal of molecular sciences 4 37298091
2025 H2AJ Is a Direct Androgen Receptor Target Gene That Regulates Androgen-Induced Cellular Senescence and Inhibits Mesenchymal Markers in Prostate Cancer Cells. Cancers 3 40075640
2025 Competitive Endogenous RNA Network Involving Immune Subgroups, Infiltration, and lncRNAs in Prostate Cancer. Genes 0 40428349
2025 PACT is requisite for prostate cancer cell proliferation. Scientific reports 0 41120564

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