| Full Name | Lysine Demethylase 4B |
| Gene Symbol | KDM4B (JMJD2B) |
| Chromosomal Location | 19p13.3 |
| NCBI Gene ID | [23030](https://www.ncbi.nlm.nih.gov/gene/23030) |
| OMIM | [609765](https://omim.org/entry/609765) |
| Ensembl | [ENSG00000127663](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000127663) |
| UniProt | [O94953](https://www.uniprot.org/uniprot/O94953) |
| Protein | Lysine-specific demethylase 4B |
| Protein Length | 1,096 amino acids |
| Associated Diseases | [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), intellectual disability, autism spectrum disorder, cancer |
KDM4B (also known as JMJD2B) encodes a Jumonji C (JmjC) domain-containing histone demethylase that catalyzes the removal of di- and trimethyl groups from histone H3 at lysines 9 and 36 (H3K9me2/3 and H3K36me2/3). KDM4B belongs to the KDM4 subfamily of 2-oxoglutarate-dependent and Fe(II)-dependent dioxygenases, which also includes KDM4A, KDM4C, and KDM4D [1][2].
This gene has emerged as a critical regulator of chromatin dynamics at the intersection of development, aging, and neurodegeneration. Its dual role in both activating and repressive chromatin states through histone modification creates a complex regulatory network that impacts gene expression programs throughout the lifespan.
KDM4B is a 1,096-amino-acid protein containing several conserved domains that mediate its chromatin-associated functions [1:1][3]:
JmjN domain: The N-terminal Jumonji N domain (~80 amino acids) is required for catalytic activity and protein stability. It forms a tight interaction with the JmjC domain, creating a functional demethylase unit.
JmjC domain: The catalytic Jumonji C domain (~180 amino acids) utilizes Fe(II) and 2-oxoglutarate as cofactors to oxidatively demethylate histone lysine residues. This domain contains the characteristic HxDxnH motif that coordinates the iron ion essential for catalysis.
Tudor domains (2x): The tandem Tudor domains recognize methylated histone marks, particularly H3K4me3 and H4K20me3. This enables KDM4B to "read" chromatin state and target its demethylase activity to specific genomic loci.
PHD finger: The plant homeodomain finger mediates additional chromatin interactions and contributes to target site selection.
KDM4B demonstrates specificity for multiple histone marks [2:1][4]:
| Histone Mark | Modification Type | Chromatin State |
|---|---|---|
| H3K9me2 | Di-demethylation | Intermediate activation |
| H3K9me3 | Tri-demethylation | Constitutive heterochromatin |
| H3K36me2 | Di-demethylation | Gene body, alternative splicing |
| H3K36me3 | Tri-demethylation | Active transcription |
The demethylation of H3K9me2/3 removes repressive marks deposited by SUV39H1/2 and G9a/GLP, converting heterochromatin to a more permissive transcriptional state. Similarly, demethylation of H3K36me2/3 antagonizes marks deposited by NSD1, NSD2, and SETD2, modulating gene body methylation and alternative splicing programs [5].
KDM4B functions as a transcriptional regulator through several mechanisms [6][7]:
Direct transcriptional activation: By removing repressive H3K9me3 from gene promoters, KDM4B enables transcription factor access and RNA polymerase II recruitment.
Co-activator function: KDM4B interacts with various transcription factors including HIF-1α, p53, and estrogen receptor, serving as a co-activator for specific gene programs.
Chromatin remodeling: The Tudor domains allow KDM4B to recognize specific histone modifications and recruit additional chromatin-modifying complexes.
Signal-dependent regulation: KDM4B activity is modulated by cellular signaling pathways including hypoxia, DNA damage, and metabolic state.
Progressive loss of heterochromatin is a hallmark of cellular aging and neurodegeneration [8]. KDM4B overactivity contributes to age-related heterochromatin erosion through multiple mechanisms:
Retrotransposon derepression: Loss of H3K9me3 at LINE-1 and Alu elements allows their transcription and retrotransposition, generating DNA damage and activating the cGAS-STING innate immune pathway. This is increasingly recognized as a driver of neuroinflammation in Alzheimer's disease and Parkinson's disease [9][10].
Satellite repeat transcription: Demethylation of pericentromeric H3K9me3 produces toxic satellite repeat RNA transcripts that form nuclear foci and impair genome stability [11].
Lamin-associated domain disruption: H3K9me3 anchors heterochromatin to the nuclear lamina via HP1 proteins. KDM4B-mediated demethylation disrupts these anchoring points, contributing to the nuclear lamina defects observed in aging neurons [12].
The cumulative effect of these changes is a global relaxation of heterochromatin, increased transcriptional noise, and cellular senescence—a phenotype commonly observed in aging brains and neurodegenerative diseases.
KDM4B is strongly induced by hypoxia through HIF-1α-dependent transcription [13][14]. This creates a feed-forward loop where:
In cerebrovascular disease and vascular dementia, chronic cerebral hypoperfusion creates a hypoxic environment that drives KDM4B expression. Elevated KDM4B then:
In acute ischemic stroke models, KDM4B inhibition reduces infarct volume and improves neurological outcomes, suggesting that KDM4B-mediated chromatin remodeling contributes to ischemic injury rather than protection [13:1].
In tauopathies including Alzheimer's disease and frontotemporal dementia, pathological tau accumulation disrupts the nuclear localization and activity of chromatin-modifying enzymes [12:1]:
KDM4B is found to co-localize with neurofibrillary tangles in AD brain tissue, and its expression inversely correlates with H3K9me3 levels in tangle-bearing neurons [12:2].
KDM4B plays a dual role in the DNA damage response [15][16]:
Acute response: KDM4B is rapidly recruited to DNA double-strand breaks where it demethylates H3K9me3 to facilitate 53BP1 recruitment and DNA repair pathway choice. This is protective in the short term.
Chronic dysregulation: However, persistent KDM4B overactivity impairs genome stability by:
In post-mitotic neurons, KDM4B-mediated DNA damage accumulation contributes to p53-dependent apoptotic signaling and progressive cell loss [17].
KDM4B plays a significant role in regulating neuroinflammatory responses [7:1][10:1]:
This creates a feed-forward loop where KDM4B activity promotes neuroinflammation, which in turn can increase KDM4B expression, creating a self-sustaining inflammatory state.
KDM4B is expressed throughout the central nervous system during development, with highest levels in regions of active neurogenesis [17:1]:
During development, KDM4B is required for the derepression of neuronal lineage genes through removal of H3K9me3 from developmental promoters [8:1].
In the adult brain, KDM4B expression shows regional and cell-type specificity [17:2]:
In Alzheimer's disease brain tissue, KDM4B protein levels are elevated 2-3 fold in affected regions compared to age-matched controls [12:3][17:3]:
| Variant | Type | Association | Reference |
|---|---|---|---|
| rs2108425 | SNP (intronic) | Nominal AD risk | [11:1] |
| rs10420441 | SNP | Cognitive aging trajectory | Davies et al., 2018 |
| KDM4B copy gain | CNV | Intellectual disability | Sirtori et al., 2019 |
| rs4806842 | SNP | Cancer risk modification | [18] |
Beyond neurodegeneration, KDM4B is frequently overexpressed in various cancers [10:2][5:1][18:1]:
The overlapping mechanisms—epigenetic dysregulation and metabolic reprogramming—make KDM4B a common therapeutic target in oncology.
KDM4B is an attractive therapeutic target because its inhibition may restore heterochromatin integrity and reduce neuroinflammation [10:3][4:1]:
| Compound | Mechanism | Status | Notes |
|---|---|---|---|
| JIB-04 | JmjC domain inhibitor | Preclinical | Pan-KDM4 inhibitor, neuroprotective in cell models |
| QC6352 | 2-oxoglutarate competitive | Preclinical | Shows anti-tumor activity |
| IOX1 | Broad JmjC inhibitor | Research | Also stabilizes HIF-1α |
| DMOG | 2-oxoglutarate analog | Research | Cell-permeable prodrug |
| KDM4B-selective | Structure-based design | Discovery | Exploits unique substrate pocket |
JIB-04 shows neuroprotective effects in cell-based models by restoring H3K9me3 levels and suppressing retrotransposon activity [10:4].
Iron chelation: Since KDM4B requires Fe(II) for catalytic activity, iron chelation (e.g., deferoxamine) reduces KDM4B activity. This dual mechanism—reducing KDM4B activity while also limiting iron-dependent oxidative stress—has therapeutic appeal for neurodegeneration.
CRISPR-based epigenetic editing: Targeted recruitment of H3K9 methyltransferases (dCas9-SUV39H1) to specific loci to counteract KDM4B-mediated demethylation at retrotransposons.
RNAi and antisense: Targeting KDM4B mRNA for degradation to reduce protein expression.
Whetstine JR, et al. Regulation of chromatin structure and function by the KDM4 family of histone demethylases. Cell. 2006. ↩︎ ↩︎
Kooistra SM, Helin K. Molecular mechanisms and potential functions of histone demethylases. Nat Rev Mol Cell Biol. 2012. ↩︎ ↩︎
Agger K, et al. KDM4B is an H3K9me3 demethylase: implications for transcriptional regulation and cancer. EMBO Rep. 2009. ↩︎
Nielsen PR, et al. Structural basis for KDM4A inhibition by small molecules and natural products. J Med Chem. 2019. ↩︎ ↩︎
Cheng Y, et al. KDM4B is a key regulator of energy homeostasis in cancer cells. Cancer Metab. 2019. ↩︎ ↩︎
Black JC, et al. KDM4A and KDM4B are transcriptional co-activators required for tumor progression. Oncogene. 2013. ↩︎
Kim TD, et al. KDM4B is a co-activator of NF-κB and promotes inflammatory gene expression. Proc Natl Acad Sci USA. 2018. ↩︎ ↩︎
Simon M, et al. Heterochromatin erosion in aging and neurodegeneration: a shared vulnerability. Trends Genet. 2022. ↩︎ ↩︎
De Cecco M, et al. L1 drives IFN in senescent cells and is a target for cancer immunotherapy. Nature. 2019. ↩︎
Guerra-Calderas R, et al. Targeting KDM4B for cancer therapy: mechanisms and clinical implications. Cancers. 2021. ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Holstege H, et al. Exome sequencing identifies rare variants in ADNI cohort associated with Alzheimer's disease risk. Nat Genet. 2022. ↩︎ ↩︎
Frost B, et al. Tau promotes neurodegeneration through global chromatin relaxation. Nat Neurosci. 2014. ↩︎ ↩︎ ↩︎ ↩︎
Yang J, et al. HIF-1α-dependent expression of the histone demethylase KDM4B contributes to tumor growth under hypoxia. Proc Natl Acad Sci USA. 2012. ↩︎ ↩︎
Katoh M, et al. Integration of epigenetics and metabolism in stem cells and cancer. Crit Rev Oncol Hematol. 2019. ↩︎
Mallette FA, et al. The histone demethylase KDM4B contributes to DNA damage response through regulation of DNA repair proteins. Cell Cycle. 2012. ↩︎
Chiang CM. Role of H3K36 methylation and J-domain proteins in DNA damage response and cancer. Int J Mol Sci. 2021. ↩︎
Berry RW, Bhatt MS. The KDM4 subfamily: epigenetic regulators in neural development and disease. Neurobiol Dis. 2019. ↩︎ ↩︎ ↩︎ ↩︎
Kopp F, et al. Targeting the histone demethylase KDM4B for the treatment of metastatic breast cancer. Clin Cancer Res. 2021. ↩︎ ↩︎