TGF-ß and TNF-α interaction promotes the expression of MMP-9 through H3K36 dimethylation: implications in breast cancer metastasis.

Increased MMP-9 expression in the tumor microenvironment (TME) plays a crucial role in the extracellular matrix remodeling to facilitate cancer invasion and metastasis. However, the mechanism of MMP-9 upregulation in TME remains elusive. Since TGF-ß and TNF-α levels are elevated in TME, we asked whether these two agents interacted to induce/augment MMP-9 expression. Using a well-established MDA-MB-231 breast cancer model, we found that the synergy between TGF-ß and TNF-α led to MMP-9 upregulation at the transcriptional and translational levels, compared to treatments with each agent alone. Our in vitro findings are corroborated by co-expression of elevated MMP-9 with TGF-ß and TNF-α in human breast cancer tissues. Mechanistically, we found that the MMP-9 upregulation driven by TGF-ß/TNF-α cooperativity was attenuated by selective inhibition of the TGF-ßRI/Smad3 pathway. Comparable outcomes were observed upon inhibition of TGF-ß-induced phosphorylation of Smad2/3 and p38. As expected, the cells defective in Smad2/3 or p38-mediated signaling did not exhibit this synergistic induction of MMP-9. Importantly, the inhibition of histone methylation but not acetylation dampened the synergistic MMP-9 expression. Histone modification profiling further identified the H3K36me2 as an epigenetic regulatory mark of this synergy. Moreover, TGF-ß/TNF-α co-stimulation led to increased levels of the transcriptionally permissive dimethylation mark at H3K36 in the MMP-9 promoter. Comparable outcomes were noted in cells deficient in NSD2 histone methyltransferase. In conclusion, our findings support a cooperativity model in which TGF-ß could amplify the TNF-α-mediated MMP-9 production via chromatin remodeling and facilitate breast cancer invasion and metastasis.

KDM4B Histone Demethylase Inhibition Attenuates Tumorigenicity of Malignant Melanoma Cells by Overriding the p53-Mediated Tumor Suppressor Pathway.

Despite significant advances in the treatment of cutaneous melanoma (hereafter melanoma), the prognosis remains less favorable due to therapeutic resistance, which is presumably linked to epigenetic dysregulation. We hypothesized that the histone lysine demethylase KDM4B could play a pivotal role in controlling therapy-resistant melanoma. To validate our hypothesis, we retrieved RNA sequencing data from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) program and observed upregulation of KDM4B in both primary and metastatic melanoma, which was associated with poor survival. To explore its role, we used murine B16, human SK-MEL-5, and G-361 melanoma cells as in vitro models of melanoma. We found that KDM4B inhibition using NCGC00244536 increased global levels of H3K9me3 and downregulated the expressions of cell cycle progression-related genes Cdk1, Cdk4, Ccnb1, and Ccnd1. Moreover, genetic ablation of KDM4B or its chemical inhibition using NCGC00244536 reduced p53 production by upregulating MDM2, which enhances the proteolytic degradation of p53. Interestingly, despite the reduction of p53, these interventions augmented apoptosis and senescence-induced cell death by activating pathways downstream of p53, as evidenced by reduced levels of pro-survival Bcl-2 and Bcl-xL proteins and increased production of pro-apoptotic cleaved caspase-3, caspase-7, Bax, and the senescence inducer Cdkn1a. Compared to the FDA-approved anti-melanoma agent dacarbazine, NCGC00244536 exhibited more pronounced cytotoxic and antiproliferative effects in melanoma cells. Importantly, NCGC00244536 demonstrated minimal cytotoxicity to low Kdm4b-expressing mouse embryonic fibroblasts. In conclusion, our findings suggest that KDM4B inhibition can override the antitumor effect of p53, and potentially serve as a therapeutic strategy for melanoma.

Decreased histone H3K9 dimethylation in synergy with DNA demethylation of Spi-1 binding site contributes to ADAMTS-5 expression in articular cartilage of osteoarthritis mice.

Osteoarthritis (OA) is defined by articular cartilage degeneration, synovial membrane inflammation, and abnormal bone remodeling. Recent study has discovered that OA development is linked to an aberrant epigenetic modification of OA-related genes. Our previous research showed that DNA demethylation in ADAMTS-5 promoter region had a substantial impact on ADAMTS-5 expression in the mouse OA model. This process facilitated the binding of Spi-1 to ADAMTS-5 promoter. While alterations in histone methylation have been documented during embryonic development and cancer development, there is a paucity of data on the change in OA pathogenesis. Even no data have been reported on the role of histone modifications in ADAMTS-5 activation in OA. Following our previous study on the role of DNA methylation, we aimed to examine the contribution of histone H3K9 dimethylation in ADAMTS-5 activation in OA. Additionally, we aimed to elucidate the molecular mechanisms underlying the cooperative interaction between DNA methylation and histone H3K9 dimethylation. The potential for anti-OA intervention therapy which is based on modulating histone H3K9 dimethylation is also explored. We demonstrated that a reduction in histone H3K9 dimethylation, along with DNA demethylation of the Spi-1 binding site, had a role in ADAMTS-5 activation in the articular cartilage of OA mice. Significantly, the conditional deletion of histone demethylase to be identified as lysine-specific demethylase 1 (LSD1) in articular cartilage could alleviate the degenerative features of OA mice. Our study demonstrates the direct impact of histone H3K9 dimethylation on gene expression, which in turn contributes to OA development. This research enhances our understanding of the underlying causes of OA.

Histone H3K9 Methylation Features under Hypoxic Conditions after the HIF1A Knockdown in Mesenchymal Stromal Cells In Vitro.

The effects of HIF1A knockdown by RNA interference on the histone H3K9 methylation in human umbilical cord mesenchymal stromal cells in vitro under conditions of 24-h exposure to hypoxia (1% O2) were studied. Evaluation of transcriptional activity of genes involved in the regulation of H3K9 methylation (KDM3A, KDM4A, and EHMT2) and the cytofluorimetric analysis of the expression of the corresponding antigens and H3K9 methylation level demonstrated a pronounced stimulating effect of hypoxic exposure. Moreover, the expression of KDM4A and EHMT2 was regulated by HIF1A-mediated mechanism, unlike KDM3A; the level of the corresponding proteins depended on HIF1A. In addition, the HIF-1-dependent regulation of KDM3A, KDM4A, and EHMT2/G9a, and directly the H3K9 methylation level in mesenchymal stromal cells also took place under normoxia conditions.

Histone methyltransferase KMT2A: Developmental regulation to oncogenic transformation.

Our current understanding of epigenetic regulation is deeply rooted in the founding contributions of Dr. C. David Allis. In 2002, Allis and colleagues first characterized the lysine methyltransferase activity of the mammalian KMT2A (MLL1), a paradigm shifting discovery that brings epigenetic dysregulation into focus for many human diseases that carry KMT2A mutations. This review will discuss the current understanding of the multifaceted roles of KMT2A in development and disease, which has paved the way for innovative and upcoming approaches to cancer therapy.

Histone modifications and their roles in macrophage-mediated inflammation: a new target for diabetic wound healing.

Impaired wound healing is one of the main clinical complications of type 2 diabetes (T2D) and a major cause of lower limb amputation. Diabetic wounds exhibit a sustained inflammatory state, and reducing inflammation is crucial to diabetic wounds management. Macrophages are key regulators in wound healing, and their dysfunction would cause exacerbated inflammation and poor healing in diabetic wounds. Gene regulation caused by histone modifications can affect macrophage phenotype and function during diabetic wound healing. Recent studies have revealed that targeting histone-modifying enzymes in a local, macrophage-specific manner can reduce inflammatory responses and improve diabetic wound healing. This article will review the significance of macrophage phenotype and function in wound healing, as well as illustrate how histone modifications affect macrophage polarization in diabetic wounds. Targeting macrophage phenotype with histone-modifying enzymes may provide novel therapeutic strategies for the treatment of diabetic wound healing.

Subcellular one carbon metabolism in cancer, aging and epigenetics.

The crosstalk between metabolism and epigenetics is an emerging field that is gaining importance in different areas such as cancer and aging, where changes in metabolism significantly impacts the cellular epigenome, in turn dictating changes in chromatin as an adaptive mechanism to bring back metabolic homeostasis. A key metabolic pathway influencing an organism's epigenetic state is one-carbon metabolism (OCM), which includes the folate and methionine cycles. Together, these cycles generate S-adenosylmethionine (SAM), the universal methyl donor essential for DNA and histone methylation. SAM serves as the sole methyl group donor for DNA and histone methyltransferases, making it a crucial metabolite for chromatin modifications. In this review, we will discuss how SAM and its byproduct, S-adenosylhomocysteine (SAH), along with the enzymes and cofactors involved in OCM, may function in the different cellular compartments, particularly in the nucleus, to directly regulate the epigenome in aging and cancer.

MAT2A is essential for zygotic genome activation by maintaining of histone methylation in porcine embryos.

Methionine adenosyltransferase 2A (MAT2A) is an essential enzyme in the methionine cycle that generates S-adenosylmethionine (SAM) by reacting with methionine and ATP. SAM acts as a methyl donors for histone and DNA methylation, which plays key roles in zygotic genome activation (ZGA). However, the effects of MAT2A on porcine ZGA remain unclear. To investigate the function of MAT2A and its underlying mechanism in porcine ZGA, MAT2A was knocked down by double-stranded RNA injection at the 1-cell stage. MAT2A is highly expressed at every stage of porcine embryo development. The percentages of four-cell-stage embryos and blastocysts were lower in the MAT2A-knockdown (KD) group than in the control group. Notably, depletion of MAT2A decreased the levels of H3K4me2, H3K9me2/3, and H3K27me3 at the four-cell stage, whereas MAT2A KD reduced the transcriptional activity of ZGA genes. MAT2A KD decreased embryonic ectoderm development (EED) and enhancer of zeste homolog 2 (EZH2) expression. Exogenous SAM supplementation rescued histone methylation levels and developmental arrest induced by MAT2A KD. Additionally, MAT2A KD significantly increased DNA damage and apoptosis. In conclusion, MAT2A is involved in regulating transcriptional activity and is essential for regulating histone methylation during porcine ZGA.

Targeting non-histone methylation in gastrointestinal cancers: From biology to clinic.

Gastrointestinal (GI) cancers, encompassing a range of malignancies within the digestive tract, present significant challenges in both diagnosis and treatment, reflecting a dire need for innovative therapeutic strategies. This article delves into the profound influence of non-histone methylation on the pathogenesis and evolution of gastrointestinal (GI) cancers. Non-histone proteins, undergoing methylation by enzymes such as Protein Arginine Methyltransferases (PRMTs) and Lysine Methyltransferases (KMTs), play pivotal roles in cellular signaling, metabolism, chromatin remodeling, and other processes crucial for cancer development. This review illuminates the complex mechanisms by which non-histone methylation affects key aspects of tumor biology, including oncogenesis, growth, proliferation, invasion, migration, metabolic reprogramming, and immune escape in GI malignancies. Highlighting recent discoveries, this work underscores the importance of non-histone methylation in cancer biology and its potential as a target for innovative therapeutic strategies aimed at improving outcomes for patients with GI cancers.

Methylation modification of non-histone proteins in breast cancer: An emerging targeted therapeutic strategy.

Breast cancer is a major public health concern worldwide, being the most commonly diagnosed cancer among women and a leading cause of cancer-related deaths. Recent studies have highlighted the significance of non-histone methylation in breast cancer, which modulates the activity, interaction, localization, and stability of target proteins. This regulation affects critical processes such as oncogenesis, tumor growth, proliferation, invasion, migration, and immune responses. This review delves into the enzymes responsible for non-histone methylation, such as protein arginine methyltransferases (PRMTs), lysine methyltransferases (KMTs), and demethylases, and explores their roles in breast cancer. By elucidating the molecular mechanisms and functional consequences of non-histone methylation, this review aims to provide insights into novel therapeutic strategies targeting these pathways. The therapeutic potential of targeting non-histone methylation to overcome drug resistance and enhance treatment efficacy in breast cancer is also discussed, highlighting promising avenues for future research and clinical applications.

The modification role and tumor association with a methyltransferase: KMT2C.

Histone methylation can affect chromosome structure and binding to other proteins, depending on the type of amino acid being modified and the number of methyl groups added, this modification may promote transcription of genes (H3K4me2, H3K4me3, and H3K79me3) or reduce transcription of genes (H3K9me2, H3K9me3, H3K27me2, H3K27me3, and H4K20me3). In addition, advances in tumor immunotherapy have shown that histone methylation as a type of protein post-translational modification is also involved in the proliferation, activation and metabolic reprogramming of immune cells in the tumor microenvironment. These post-translational modifications of proteins play a crucial role in regulating immune escape from tumors and immunotherapy. Lysine methyltransferases are important components of the post-translational histone methylation modification pathway. Lysine methyltransferase 2C (KMT2C), also known as MLL3, is a member of the lysine methyltransferase family, which mediates the methylation modification of histone 3 lysine 4 (H3K4), participates in the methylation of many histone proteins, and regulates a number of signaling pathways such as EMT, p53, Myc, DNA damage repair and other pathways. Studies of KMT2C have found that it is aberrantly expressed in many diseases, mainly tumors and hematological disorders. It can also inhibit the onset and progression of these diseases. Therefore, KMT2C may serve as a promising target for tumor immunotherapy for certain diseases. Here, we provide an overview of the structure of KMT2C, disease mechanisms, and diseases associated with KMT2C, and discuss related challenges.

PTIP epigenetically regulates DNA damage-induced cell cycle arrest by upregulating PRDM1.

The genome is constantly exposed to DNA damage from endogenous and exogenous sources. Fine modulation of DNA repair, chromatin remodeling, and transcription factors is necessary for protecting genome integrity, but the precise mechanisms are still largely unclear. We found that after ionizing radiation (IR), global trimethylation of histone H3 at lysine 4 (H3K4me3) was decreased at an early (5 min) post-IR phase but increased at an intermediate (180 min) post-IR phase in both human and mouse hematopoietic cells. We demonstrated that PTIP, a component of the MLL histone methyltransferase complex, is required for H3K4me3 upregulation in the intermediate post-IR phase and promotes cell cycle arrest by epigenetically inducing a cell cycle inhibitor, PRDM1. In addition, we found that PTIP expression is specifically downregulated in acute myeloid leukemia patients. These findings collectively suggest that the PTIP-PRDM1 axis plays an essential role in proper DNA damage response and its deregulation contributes to leukemogenesis.

The role of hexokinases in epigenetic regulation: altered hexokinase expression and chromatin stability in yeast.

BACKGROUND: Human hexokinase 2 (HK2) plays an important role in regulating Warburg effect, which metabolizes glucose to lactate acid even in the presence of ample oxygen and provides intermediate metabolites to support cancer cell proliferation and tumor growth. HK2 overexpression has been observed in various types of cancers and targeting HK2-driven Warburg effect has been suggested as a potential cancer therapeutic strategy. Given that epigenetic enzymes utilize metabolic intermediates as substrates or co-factors to carry out post-translational modification of histones and nucleic acids modifications in cells, we hypothesized that altering HK2 expression could impact the epigenome and, consequently, chromatin stability in yeast. To test this hypothesis, we established genetic models with different yeast hexokinase 2 (HXK2) expression in Saccharomyces cerevisiae yeast cells and investigated the effect of HXK2-dependent metabolism on parental nucleosome transfer, a key DNA replication-coupled epigenetic inheritance process, and chromatin stability. RESULTS: By comparing the growth of mutant yeast cells carrying single deletion of hxk1Δ, hxk2Δ, or double-loss of hxk1Δ hxk2Δ to wild-type cells, we firstly confirmed that HXK2 is the dominant HXK in yeast cell growth. Surprisingly, manipulating HXK2 expression in yeast, whether through overexpression or deletion, had only a marginal impact on parental nucleosome assembly, but a noticeable trend with decrease chromatin instability. However, targeting yeast cells with 2-deoxy-D-glucose (2-DG), a clinical glycolysis inhibitor that has been proposed as an anti-cancer treatment, significantly increased chromatin instability. CONCLUSION: Our findings suggest that in yeast cells lacking HXK2, alternative HXKs such as HXK1 or glucokinase 1 (GLK1) play a role in supporting glycolysis at a level that adequately maintains epigenomic stability. While our study demonstrated an increase in epigenetic instability with 2-DG treatment, the observed effect seemed to occur dependent on non-glycolytic function of Hxk2. Thus, additional research is needed to identify the molecular mechanism through which 2-DG influences chromatin stability.

Epigenetic Modifiers in Cancer Metastasis.

Metastasis is the primary cause of cancer-related death, with the dissemination and colonization of primary tumor cells at the metastatic site facilitated by various molecules and complex pathways. Understanding the biological mechanisms underlying the metastatic process is critical for the development of effective interventions. Several epigenetic modifications have been identified that play critical roles in regulating cancer metastasis. This review aims to provide a comprehensive summary of recent advances in understanding the role of epigenetic modifiers, including histone modifications, DNA methylation, non-coding RNAs, enhancer reprogramming, chromatin accessibility, and N6-methyladenosine, in metastasis-associated processes, such as epithelial-mesenchymal transition (EMT), cancer cell migration, and invasion. In particular, this review provides a detailed and in-depth description of the role of crosstalk between epigenetic regulators in tumor metastasis. Additionally, we explored the potential and limitations of epigenetics-related target molecules in the diagnosis, treatment, and prognosis of cancer metastasis.

Fragment-based discovery of small molecule inhibitors of the HDGFRP2 PWWP domain.

The PWWP domain of hepatoma-derived growth factor-related protein 2 (HDGFRP2) recognizes methylated histones to initiate the recruitment of homologous recombination repair proteins to damaged silent genes. The combined depletion of HDGFRP2 and its paralog PSIP1 effectively impedes the onset and progression of diffuse intrinsic pontine glioma (DIPG). Here, we discovered varenicline and 4-(4-bromo-1H-pyrazol-3-yl) pyridine (BPP) as inhibitors of the HDGFRP2 PWWP domain through a fragment-based screening method. The complex crystal structures reveal that both Varenicline and BPP engage with the aromatic cage of the HDGFRP2 PWWP domain, albeit via unique binding mechanisms. Notably, BPP represents the first single-digit micromolar inhibitor of the HDGFRP2 PWWP domain with a high ligand efficiency. As a dual inhibitor targeting both HDGFRP2 and PSIP1 PWWP domains, BPP offers an exceptional foundation for further optimization into a chemical tool to dissect the synergetic function of HDGFRP2 and PSIP1 in DIPG pathogenesis.

Histone H3K18 & H3K23 acetylation directs establishment of MLL-mediated H3K4 methylation.

In an unmodified state, positively charged histone N-terminal tails engage nucleosomal DNA in a manner which restricts access to not only the underlying DNA but also key tail residues subject to binding and/or modification. Charge-neutralizing modifications, such as histone acetylation, serve to disrupt this DNA-tail interaction, facilitating access to such residues. We previously showed that a polyacetylation-mediated chromatin "switch" governs the read-write capability of H3K4me3 by the MLL1 methyltransferase complex. Here, we discern the relative contributions of site-specific acetylation states along the H3 tail and extend our interrogation to other chromatin modifiers. We show that the contributions of H3 tail acetylation to H3K4 methylation by MLL1 are highly variable, with H3K18 and H3K23 acetylation exhibiting robust stimulatory effects and that this extends to the related H3K4 methyltransferase complex, MLL4. We show that H3K4me1 and H3K4me3 are found preferentially co-enriched with H3 N-terminal tail proteoforms bearing dual H3K18 and H3K23 acetylation (H3{K18acK23ac}). We further show that this effect is specific to H3K4 methylation, while methyltransferases targeting other H3 tail residues (H3K9, H3K27, & H3K36), a methyltransferase targeting the nucleosome core (H3K79), and a kinase targeting a residue directly adjacent to H3K4 (H3T3) are insensitive to tail acetylation. Together, these findings indicate a unique and robust stimulation of H3K4 methylation by H3K18 and H3K23 acetylation and provide key insight into why H3K4 methylation is often associated with histone acetylation in the context of active gene expression.

CircARAP2 controls sMICA-induced NK cell desensitization by erasing CTCF/PRC2-induced suppression in early endosome marker RAB5A.

Natural killer cells (NK) are the "professional killer" of tumors and play a crucial role in anti-tumor immunotherapy. NK cell desensitization is a key mechanism of tumor immune escape. Dysregulated NKG2D-NKG2DL signaling is a primary driver of this desensitization process. However, the factors that regulate NK cell desensitization remain largely uncharacterized. Here, we present the first report that circular RNA circARAP2 (hsa_circ_0069396) is involved in the soluble MICA (sMICA)-induced NKG2D endocytosis in the NK cell desensitization model. CircARAP2 was upregulated during NK cell desensitization and the loss of circARAP2 alleviated NKG2D endocytosis and NK cell desensitization. Using Chromatin isolation by RNA purification (ChIRP) and RNA pull-down approaches, we identified that RAB5A, a molecular marker of early endosomes, was its downstream target. Notably, transcription factor CTCF was an intermediate functional partner of circARAP2. Mechanistically, we discovered that circARAP2 interacted with CTCF and inhibited the recruitment of CTCF-Polycomb Repressive Complex 2 (PRC2) to the promoter region of RAB5A, thereby erasing histone H3K27 and H3K9 methylation suppression to enhance RAB5A transcription. These data demonstrate that inhibition of circARAP2 effectively alleviates sMICA-induced NKG2D endocytosis and NK cell desensitization, providing a novel target for therapeutic intervention in tumor immune evasion.

Epigenetic regulation of androgen dependent and independent prostate cancer.

Prostate cancer is one of the most common malignancies among men worldwide. Besides genetic alterations, epigenetic modulations including DNA methylation, histone modifications and miRNA mediated alteration of gene expression are the key driving forces for the prostate tumor development and cancer progression. Aberrant expression and/or the activity of the epigenetic modifiers/enzymes, results in aberrant expression of genes involved in DNA repair, cell cycle regulation, cell adhesion, apoptosis, autophagy, tumor suppression and hormone response and thereby disease progression. Altered epigenome is associated with prostate cancer recurrence, progression, aggressiveness and transition from androgen-dependent to androgen-independent phenotype. These epigenetic modifications are reversible and various compounds/drugs targeting the epigenetic enzymes have been developed that are effective in cancer treatment. This chapter focuses on the epigenetic alterations in prostate cancer initiation and progression, listing different epigenetic biomarkers for diagnosis and prognosis of the disease and their potential as therapeutic targets. This chapter also summarizes different epigenetic drugs approved for prostate cancer therapy and the drugs available for clinical trials.

Molecular Mechanisms in Tumorigenesis of Hepatocellular Carcinoma and in Target Treatments-An Overview.

Hepatocellular carcinoma is the most common primary malignancy of the liver, with hepatocellular differentiation. It is ranked sixth among the most common cancers worldwide and is the third leading cause of cancer-related deaths. The most important etiological factors discussed here are viral infection (HBV, HCV), exposure to aflatoxin B1, metabolic syndrome, and obesity (as an independent factor). Directly or indirectly, they induce chromosomal aberrations, mutations, and epigenetic changes in specific genes involved in intracellular signaling pathways, responsible for synthesis of growth factors, cell proliferation, differentiation, survival, the metastasis process (including the epithelial-mesenchymal transition and the expression of adhesion molecules), and angiogenesis. All these disrupted molecular mechanisms contribute to hepatocarcinogenesis. Furthermore, equally important is the interaction between tumor cells and the components of the tumor microenvironment: inflammatory cells and macrophages-predominantly with a pro-tumoral role-hepatic stellate cells, tumor-associated fibroblasts, cancer stem cells, extracellular vesicles, and the extracellular matrix. In this paper, we reviewed the molecular biology of hepatocellular carcinoma and the intricate mechanisms involved in hepatocarcinogenesis, and we highlighted how certain signaling pathways can be pharmacologically influenced at various levels with specific molecules. Additionally, we mentioned several examples of recent clinical trials and briefly described the current treatment protocol according to the NCCN guidelines.

KDM4B mutations in human cancers.

Homologous recombination (HR) is essential for repair of DNA double-strand breaks (DSBs) and restart of stalled or collapsed replication forks. Most cancers are characterized by mutations in components of the DSB repair pathways. Redundant DSB repair pathways exist in eukaryotes from yeast to humans and recent evidence has shown that complete loss of HR function appears to be lethal. Recent evidence has also shown that cancer cells with mutations in one DSB repair pathway can be killed by inhibiting one or more parallel pathways, a strategy that is currently aggressively explored as a cancer therapy. KDM4B is a histone demethylase with pleiotropic functions, which participates in preparing DSBs for repair by contributing to chromatin remodeling. In this report we carried out a pan-cancer analysis of KDM4B mutations with the goal of understanding their distribution and interaction with other DSB genes. We find that although KDM4B mutations co-occur with DSB repair genes, most KDM4B mutations are not drivers or pathogenic. A sequence conservation analysis from yeast to humans shows that highly conserved residues are resistant to mutation. Finally, all mutations occur in a heterozygous state. A single mutation, R986L, was predicted to significantly affect protein structure using computational modeling. This analysis suggests that KDM4B makes contributions to DSB repair but is not a key player.