Dysregulation Of Histone Acetylation Research Articles

Comprehensive analysis of histone acetylation-related genes in glioblastoma and lower-grade gliomas: Insights into drug sensitivity, molecular subtypes, immune infiltration, and prognosis.

The purpose of this research was to study the impact of histone acetylation on glioblastoma multiforme (GBM) and lower-grade gliomas (LGG) and its potential implications for patient prognosis. We aimed to assess the histone acetylation score (HAs) and its relationship with key genes involved in histone acetylation regulation. The TCGA-GBMLGG dataset, which provides comprehensive genomic and clinical information, was utilized for this study. We calculated the HAs by analyzing the expression levels of histone acetylation-related genes, including histone acetyltransferases and histone deacetylases, in GBM and LGG patients. Kaplan-Meier survival analysis was performed to evaluate the prognostic value of the HAs. Furthermore, correlation analysis and differential expression analysis were conducted to assess the relationship between the HAs and key genes involved in histone acetylation regulation, as well as the expression differences of immune checkpoint genes. Our analysis revealed a significant association between the HAs and patient prognosis, with higher HAs correlating to poorer outcomes in GBM and LGG patients. We observed a positive correlation between the HAs and key genes involved in histone acetylation regulation, indicating their potential role in modulating histone acetylation levels. Moreover, we found significant expression differences for immune checkpoint genes between high and low HAs groups, suggesting a potential impact of histone acetylation on the immune response in GBM and LGG. This study highlights the significance of histone acetylation in GBM and LGG. The HAs demonstrated prognostic value, indicating its potential as a clinically relevant biomarker. The correlation between the HAs and key genes involved in histone acetylation regulation provides insights into the underlying mechanisms driving histone acetylation dysregulation in GBM and LGG. Furthermore, the observed expression differences of immune checkpoint genes suggest a potential link between histone acetylation and the immune response. These findings contribute to our understanding of the molecular basis of GBM and LGG and have implications for personalized treatment approaches targeting histone acetylation and the immune microenvironment. Further validation and functional studies are needed to confirm these findings and explore potential therapeutic strategies.

Unlocking the epigenetic symphony: histone acetylation's impact on neurobehavioral change in neurodegenerative disorders.

Recent genomics and epigenetic advances haveempowered the exploration of DNA/RNA methylation and histone modifications crucial for gene expression in response to stress, agingand disease. Interest in understanding neuronal plasticity's epigenetic mechanisms, influencing brain rewiring amid development, agingand neurodegenerative disorders, continues to grow. Histone acetylation dysregulation, a commonality in diverse brain disorders, hasbecomea therapeutic focus. Histone acetyltransferasesand histone deacetylases haveemerged as promising targets for neurodegenerative disorder treatment. This review delves into histone acetylation regulation, potential therapiesand future perspectives for disorders like Alzheimer's, Parkinson'sand Huntington's. Exploring genetic-environmental interplay through models and studies reveals molecular changes, behavioral insightsand early intervention possibilities targeting the epigenome in at-risk individuals.

Histone 3 lysine 9 acetylation-specific reprogramming regulates esophageal squamous cell carcinoma progression and metastasis.

Dysregulation of histone acetylation is widely implicated in tumorigenesis, yet its specific roles in the progression and metastasis of esophageal squamous cell carcinoma (ESCC) remain unclear. Here, we profiled the genome-wide landscapes of H3K9ac for paired adjacent normal (Nor), primary ESCC (EC) and metastatic lymph node (LNC) esophageal tissues from three ESCC patients. Compared to H3K27ac, we identified a distinct epigenetic reprogramming specific to H3K9ac in EC and LNC samples relative to Nor samples. This H3K9ac-related reprogramming contributed to the transcriptomic aberration of targeting genes, which were functionally associated with tumorigenesis and metastasis. Notably, genes with gained H3K9ac signals in both primary and metastatic lymph node samples (common-gained gene) were significantly enriched in oncogenes. Single-cell RNA-seq analysis further revealed that the corresponding top 15 common-gained genes preferred to be enriched in mesenchymal cells with high metastatic potential. Additionally, in vitro experiment demonstrated that the removal of H3K9ac from the common-gained gene MSI1 significantly downregulated its transcription, resulting in deficiencies in ESCC cell proliferation and migration. Together, our findings revealed the distinct characteristics of H3K9ac in esophageal squamous cell carcinogenesis and metastasis, and highlighted the potential therapeutic avenue for intervening ESCC through epigenetic modulation via H3K9ac.

Dysregulated glial genes in Alzheimer's disease are essential for homeostatic plasticity: Evidence from integrative epigenetic and single cell analyses.

Synaptic homeostatic plasticity is a foundational regulatory mechanism that maintains the stability of synaptic and neural functions within the nervous system. Impairment of homeostatic regulation has been linked to synapse destabilization during the progression of Alzheimer's disease (AD). Recent epigenetic and transcriptomic characterizations of the nervous system have revealed intricate molecular details about the aging brain and the pathogenesis of neurodegenerative diseases. Yet, how abnormal epigenetic and transcriptomic alterations in different cell types in AD affect synaptic homeostatic plasticity remains to be elucidated. Various glial cell types play critical roles in modulating synaptic functions both during the aging process and in the context of AD. Here, we investigated the impact of glial dysregulation of histone acetylation and transcriptome in AD on synaptic homeostatic plasticity, using computational analysis combined with electrophysiological methods in Drosophila. By integrating snRNA-seq and H3K9ac ChIP-seq data from the same AD patient cohort, we pinpointed cell type-specific signature genes that were transcriptionally altered by histone acetylation. We subsequently investigated the role of these glial genes in regulating presynaptic homeostatic potentiation in Drosophila. Remarkably, nine glial-specific genes, which were identified through our computational method as targets of H3K9ac and transcriptional dysregulation, were found to be crucial for the regulation of synaptic homeostatic plasticity in Drosophila. Our genetic evidence connects abnormal glial transcriptomic changes in AD with the impairment of homeostatic plasticity in the nervous system. In summary, our integrative computational and genetic studies highlight specific glial genes as potential key players in the homeostatic imbalance observed in AD.

Histone acetylation by HBO1 (KAT7) activates Wnt/β-catenin signaling to promote leukemogenesis in B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive hematological disorder with a dismal prognosis. The dysregulation of histone acetylation is of great significance in the pathogenesis and progression of B-ALL. Regarded as a fundamental acetyltransferase gene, the role of HBO1 (lysine acetyltransferase 7/KAT7) in B-ALL has not been investigated. Herein, we found that HBO1 expression was elevated in human B-ALL cells and associated with poor disease-free survival. Strikingly, HBO1 knockdown inhibited viability, proliferation, and G1-S cycle progression in B-ALL cells, while provoking apoptosis. In contrast, ectopic overexpression of HBO1 enhanced cell viability and proliferation but inhibited apoptotic activation. The results of in vivo experiments also certificated the inhibitory effect of HBO1 knockdown on tumor growth. Mechanistically, HBO1 acetylated histone H3K14, H4K8, and H4K12, followed by upregulating CTNNB1 expression, resulting in activation of the Wnt/β-catenin signaling pathway. Moreover, a novel small molecule inhibitor of HBO1, WM-3835, potently inhibited the progression of B-ALL. Our data identified HBO1 as an efficacious regulator of CTNNB1 with therapeutic potential in B-ALL.

ACSS2-dependent histone acetylation improves cognition in mouse model of Alzheimer’s disease

BackgroundNuclear acetyl-CoA pools govern histone acetylation that controls synaptic plasticity and contributes to cognitive deterioration in patients with Alzheimer’s disease (AD). Nuclear acetyl-CoA pools are generated partially from local acetate that is metabolized by acetyl-CoA synthetase 2 (ACSS2). However, the underlying mechanism of histone acetylation dysregulation in AD remains poorly understood.MethodsWe detected ACSS2 expression and histone acetylation levels in the brains of AD patients and 5 × FAD mice. When we altered ACSS2 expression by injecting adeno-associated virus into the dorsal hippocampus of 5 × FAD mice and replenished ACSS2 substrate (acetate), we observed changes in cognitive function by Morris water maze. We next performed RNA-seq, ChIP-qPCR, and electrophysiology to study molecular mechanism underlying ACSS2-mediated spatial learning and memory in 5 × FAD mice.ResultsWe reported that ACSS2 expression and histone acetylation (H3K9, H4K12) were reduced in the hippocampus and prefrontal cortex of 5 × FAD mice. Reduced ACSS2 levels were also observed in the temporal cortex of AD patients. 5 × FAD mice exhibited a low enrichment of acetylated histones on the promoters of NMDARs and AMPARs, together with impaired basal and activity-dependent synaptic plasticity, all of which were rescued by ACSS2 upregulation. Moreover, acetate replenishment enhanced ac-H3K9 and ac-H4K12 in 5 × FAD mice, leading to an increase of NMDARs and AMPARs and a restoration of synaptic plasticity and cognitive function in an ACSS2-dependent manner.ConclusionACSS2 is a key molecular switch of cognitive impairment and that targeting ACSS2 or acetate administration may serve as a novel therapeutic strategy for the treatment of intermediate or advanced AD.Graphical Nuclear acetyl-CoA pools are generated partly from local acetate that is metabolized by acetyl-CoA synthetase 2 (ACSS2). Model depicts that ACSS2 expression is downregulated in the brains of 5×FAD model mice and AD patients. Of note, ACSS2 downregulation mediates a reduction in ionotropic glutamate receptor expression through histone acetylation, which exacerbates synaptic plasticity impairment in AD. These deficits can be rescued by ACSS2 upregulation or acetate supplementation (GTA, an FDA-approved food additive), which may serve as a promising therapeutic strategy for AD treatment.

Chromatography-Free Synthesis of β-Carboline 1-Hydrazides and an Investigation of the Mechanism of Their Bioactivity: The Discovery of β-Carbolines as Promising Antifungal and Antibacterial Candidates.

Agrochemical science prioritizes the discovery and effective synthesis of innovative and promising lead compounds. Herein, we developed an efficient column chromatography-free synthesis for β-carboline 1-hydrazides via a mild CuBr2-catalyzed oxidation and investigated the antifungal and antibacterial activities and mechanisms for these compounds. In our study, compounds 4de (EC50 = 0.23 μg·mL-1) and 4dq (EC50 = 0.11 μg·mL-1) displayed the best efficacy, demonstrating enhancements in inhibitory activity of more than 20-fold against Ggt compared to silthiopham (EC50 = 2.39 μg·mL-1). Additionally, compound 4de (EC50 = 0.21 μg·mL-1) demonstrated outstanding in vitro antifungal activities as well as in vivo curative activities against Fg. According to preliminary mechanistic studies, β-carboline 1-hydrazides led to the accumulation of reactive oxygen species, destruction of cell membranes, and dysregulation of histone acetylation. Furthermore, several substances exhibited antibacterial activity against Psg and Cms by preventing the development of bacterial biofilms.

Loss of TIP60 (KAT5) abolishes H2AZ lysine 7 acetylation and causes p53, INK4A, and ARF-independent cell cycle arrest

Histone acetylation is essential for initiating and maintaining a permissive chromatin conformation and gene transcription. Dysregulation of histone acetylation can contribute to tumorigenesis and metastasis. Using inducible cre-recombinase and CRISPR/Cas9-mediated deletion, we investigated the roles of the histone lysine acetyltransferase TIP60 (KAT5/HTATIP) in human cells, mouse cells, and mouse embryos. We found that loss of TIP60 caused complete cell growth arrest. In the absence of TIP60, chromosomes failed to align in a metaphase plate during mitosis. In some TIP60 deleted cells, endoreplication occurred instead. In contrast, cell survival was not affected. Remarkably, the cell growth arrest caused by loss of TIP60 was independent of the tumor suppressors p53, INK4A and ARF. TIP60 was found to be essential for the acetylation of H2AZ, specifically at lysine 7. The mRNA levels of 6236 human and 8238 mouse genes, including many metabolism genes, were dependent on TIP60. Among the top 50 differentially expressed genes, over 90% were downregulated in cells lacking TIP60, supporting a role for TIP60 as a key co-activator of transcription. We propose a primary role of TIP60 in H2AZ lysine 7 acetylation and transcriptional activation, and that this fundamental role is essential for cell proliferation. Growth arrest independent of major tumor suppressors suggests TIP60 as a potential anti-cancer drug target.

Manipulating histone acetylation leads to antitumor effects in hemangiosarcoma cells.

Canine hemangiosarcoma (HSA) is a malignant tumour derived from endothelial cells. No effective treatment has yet been developed because of the lack of understanding of its pathogenesis. Histone acetylation, an epigenetic modification, is highly associated with cancer pathogenesis. Manipulating histone acetylation by histone deacetylase inhibitors (HDACi) or bromodomain and extraterminal domain inhibitors (BETi) is one approach to treat various cancers. However, the role of histone acetylation in HSA remains unknown. This study aimed to investigate how histone acetylation functions in HSA pathogenesis using two HDACi, suberanilohydroxamic acid (SAHA) and valproic acid (VPA), and one BETi, JQ1, in vitro and in vivo. Histone acetylation levels were high in cell lines and heterogeneous in clinical cases. SAHA and JQ1 induced apoptosis in HSA cell lines. HSA cell lines treated with SAHA and VPA upregulated inflammatory-related genes and attracted macrophage cell line RAW264 cells, which suggests that SAHA and VPA can affect immune responses. JQ1 stimulated autophagy and inhibited the cell cycle in HSA cell lines. Finally, we demonstrated that JQ1 suppressed HSA tumour cell proliferation in vivo although SAHA and VPA did not affect tumour growth. These results suggest that BETi can be alternative drugs for HSA treatment. Although further research is required, our study indicated that dysregulation of histone acetylation is likely to be involved in HSA malignancy.

Tip60 protects against amyloid-β-induced transcriptomic alterations via different modes of action in early versus late stages of neurodegeneration

Alzheimer's disease (AD) is an age-related neurodegenerative disorder hallmarked by amyloid-β (Aβ) plaque accumulation, neuronal cell death, and cognitive deficits that worsen during disease progression. Histone acetylation dysregulation, caused by an imbalance between reduced histone acetyltransferases (HAT) Tip60 and increased histone deacetylase 2 (HDAC2) levels, can directly contribute to AD pathology. However, whether such AD-associated neuroepigenetic alterations occur in response to Aβ peptide production and can be protected against by increasing Tip60 levels over the course of neurodegenerative progression remains unknown. Here we profile Tip60 HAT/HDAC2 dynamics and transcriptome-wide changes across early and late stage AD pathology in the Drosophila brain produced solely by human amyloid-β42. We show that early Aβ42 induction leads to disruption of Tip60 HAT/HDAC2 balance during early neurodegenerative stages preceding Aβ plaque accumulation that persists into late AD stages. Correlative transcriptome-wide studies reveal alterations in biological processes we classified as transient (early-stage only), late-onset (late-stage only), and constant (both). Increasing Tip60 HAT levels in the Aβ42 fly brain protects against AD functional pathologies that include Aβ plaque accumulation, neural cell death, cognitive deficits, and shorter life-span. Strikingly, Tip60 protects against Aβ42-induced transcriptomic alterations via distinct mechanisms during early and late stages of neurodegeneration. Our findings reveal distinct modes of neuroepigenetic gene changes and Tip60 neuroprotection in early versus late stages in AD that can serve as early biomarkers for AD, and support the therapeutic potential of Tip60 over the course of AD progression.

Histone Deacetylase Inhibitor Alleviates the Neurodegenerative Phenotypes and Histone Dysregulation in Presenilins-Deficient Mice.

Histone acetylation has been shown to play a crucial role in memory formation, and histone deacetylase (HDAC) inhibitor sodium butyrate (NaB) has been demonstrated to improve memory performance and rescue the neurodegeneration of several Alzheimer’s Disease (AD) mouse models. The forebrain presenilin-1 and presenilin-2 conditional double knockout (cDKO) mice showed memory impairment, forebrain degeneration, tau hyperphosphorylation and inflammation that closely mimics AD-like phenotypes. In this article, we have investigated the effects of systemic administration of NaB on neurodegenerative phenotypes in cDKO mice. We found that chronic NaB treatment significantly restored contextual memory but did not alter cued memory in cDKO mice while such an effect was not permanent after treatment withdrawal. We further revealed that NaB treatment did not rescue reduced synaptic numbers and cortical shrinkage in cDKO mice, but significantly increased the neurogenesis in subgranular zone of dentate gyrus (DG). We also observed that tau hyperphosphorylation and inflammation related protein glial fibrillary acidic protein (GFAP) level were decreased in cDKO mice by NaB. Furthermore, GO and pathway analysis for the RNA-Seq data demonstrated that NaB treatment induced enrichment of transcripts associated with inflammation/immune processes and cytokine-cytokine receptor interactions. RT-PCR confirmed that NaB treatment inhibited the expression of inflammation related genes such as S100a9 and Ccl4 found upregulated in the brain of cDKO mice. Surprisingly, the level of brain histone acetylation in cDKO mice was dramatically increased and was decreased by the administration of NaB, which may reflect dysregulation of histone acetylation underlying memory impairment in cDKO mice. These results shed some lights on the possible molecular mechanisms of HDAC inhibitor in alleviating the neurodegenerative phenotypes of cDKO mice and provide a promising target for treating AD.

4-Phenybutyric acid promotes gastric cancer cell migration via histone deacetylase inhibition-mediated HER3/HER4 up-regulation.

Dysregulation of histone acetylation plays an important role in tumor development. Histone acetylation regulates gene transcription and expression, which is reversibly regulated by histone acetyltransferase (HAT) and histone deacetylase (HDAC). As an HDAC inhibitor, 4-phenylbutyric acid (4-PBA) can increase histone acetylation levels by inhibiting HDAC activity. While 4-PBA inhibits proliferation of tumor cells in vitro, clinical trials have failed to show benefits of 4-PBA for refractory solid tumors. Here, we found that 4-PBA could enhance the migration capacity of gastric cancer cells. Upregulation of HER3/HER4 and activation of HER3/HER4-ERK pathway was shown to be involved in 4-PBA-induced gastric cancer cell migration. Knockdown of HER3/HER4 blocked HER3/HER4-ERK activation and partially prevented 4-PBA-induced cell migration. Consistently, the ERK inhibitor PD98059 also partially prevented 4-PBA-induced cell migration. Moreover, enhanced levels of acetyl-histones were detected following 4-PBA-treatment, and histone3 acetylation in promoter regions of HER3 and HER4 were confirmed by ChIP. These results demonstrate that 4-PBA promotes gastric cancer cells migration through upregulation of HER3/HER4 subsequent to increased levels of acetyl-histone and activation of ERK signaling. These novel findings provide important considerations for the use of 4-PBA in cancer therapeutics.

Hypoacetylation of acetyl-histone H3 (H3K9ac) as marker of poor prognosis in oral cancer.

Epigenetics refers to changes in cell characteristics that occur independently of modifications to the DNA sequence. Oral carcinogenesis is influenced by modifications in epigenetic mechanisms, including changes in histones, which are proteins that support chromatin remodelling for the dynamic regulation of gene expression and silencing. The dysregulation of histone acetylation can lead to the uncontrolled activity of different genes, thereby triggering events associated with malignant transformation. The aim of this study was to analyse the expression of acetyl-histone H3 at lys9 (H3K9ac) in oral leucoplakia (OL) and oral squamous cell carcinoma (OSCC) in addition to its association with cell proliferation, epithelial-mesenchymal transition (EMT) and clinical-pathological findings. Samples of normal oral mucosa (NOM), OL and OSCC were submitted to immunohistochemical analysis using anti-H3K9ac, Ki67 and vimentin. Slides were submitted to quantitative analysis regarding the percentage of positive cells. OSCC presented less expression of H3K9ac in comparison to OL (P < 0.01), whereas Ki67 and vimentin levels increased from OL to OSCC (P < 0.001 and P = 0.03, respectively). OSCC patients with poor prognosis had less H3K9ac expression (P = 0.04). The Kaplan-Meier cumulative survival curves also revealed lower survival rates in patients with less H3K9ac expression (P < 0.01). The present findings suggest that changes in H3K9ac occur during the process of oral carcinogenesis along with an increase in cell proliferation and EMT. The results demonstrate that H3K9ac may be a useful novel prognostic marker for OSCC.

A time-series analysis of altered histone H3 acetylation and gene expression during the course of MMAIII-induced malignant transformation of urinary bladder cells.

Our previous studies have shown that chronic exposure to low doses of monomethylarsonous acid (MMAIII) causes global histone acetylation dysregulation in urothelial cells (UROtsa cells) during the course of malignant transformation. To reveal the relationship between altered histone acetylation patterns and aberrant gene expression, more specifically, the carcinogenic relevance of these alterations, we performed a time-course analysis of the binding patterns of histone 3 lysine 18 acetylation (H3K18ac) across the genome and generated global gene-expression profiles from this UROtsa cell malignant transformation model. We showed that H3K18ac, one of the most significantly upregulated histone acetylation sites following MMAIII exposure, was enriched at gene promoter-specific regions across the genome and that MMAIII-induced upregulation of H3K18ac led to an altered binding pattern in a large number of genes that was most significant during the critical window for MMAIII-induced UROtsa cells' malignant transformation. Some genes identified as having a differential binding pattern with H3K18ac, acted as upstream regulators of critical gene networks with known functions in tumor development and progression. The altered H3K18ac binding patterns not only led to changes in expression of these directly affected upstream regulators but also resulted in gene-expression changes in their regulated networks. Collectively, our data suggest that MMAIII-induced alteration of histone acetylation patterns in UROtsa cells led to a time- and malignant stage-dependent aberrant gene-expression pattern, and that some gene regulatory networks were altered in accordance with their roles in carcinogenesis, probably contributing to MMAIII-induced urothelial cell malignant transformation and carcinogenesis.

Histone acetylation in neuronal (dys)function.

Cognitive functions require the expression of an appropriate pattern of genes in response to environmental stimuli. Over the last years, many studies have accumulated knowledge towards the understanding of molecular mechanisms that regulate neuronal gene expression. Epigenetic modifications have been shown to play an important role in numerous neuronal functions, from synaptic plasticity to learning and memory. In particular, histone acetylation is a central player in these processes. In this review, we present the molecular mechanisms of histone acetylation and summarize the data underlying the relevance of histone acetylation in cognitive functions in normal and pathological conditions. In the last part, we discuss the different mechanisms underlying the dysregulation of histone acetylation associated with neurological disorders, with a particular focus on environmental causes (stress, drugs, or infectious agents) that are linked to impaired histone acetylation.

Editorial: Transcriptional Regulation of Memory.

Editorial: Transcriptional Regulation of Memory.

Persistent Memory Deficits and Histone Modification after a Systemic Inflammatory Event

Inflammatory events, including myocardial infarction (MI), illness, or major surgery, commonly lead to cognitive deficits that persist for months or years, far beyond the duration of inflammation. The cognitive deficits correlate with poorer outcomes as well as increased morbidity and mortality. These clinical observations are paralleled in animal models of MI and inflammation. However, the mechanisms mediating such persistent effects remain unknown. Epigenetic modifications induced by cytokine signaling are one potential mechanism. In particular, dysregulation of histone acetylation can be triggered by inflammation and also induce memory deficits. We hypothesized that, although the initial cytokine signaling would be resolved within 8 weeks after MI, changes in histone modifications would persist and mediate lasting cognitive impairments.MethodsWe used a surgical model of MI in male and female mice, with sham‐operated (sham) and non‐operated (non‐op) control groups. Eight weeks after the MI group's surgery, memory was assessed using context fear conditioning (3 min exposure to context followed by a single 0.8mA, 2sec foot shock). In separate animals, hippocampus and blood serum were collected 8 weeks after MI. We used multiplex cytokine analysis to determine levels in the hippocampus. In addition, we conducted western blotting to determine persistent alterations in histone acetylation, phospho‐acetylation and methylation. Finally, we analyzed hearts from MI and sham animals to determine infarct size.Results and DiscussionEight weeks after MI surgery, both male and female mice exhibited impairments in fear conditioning compared with non‐op control animals. In addition, female ‐ but not male ‐ sham mice exhibited deficits in context fear conditioning. This suggests that female mice are more susceptible to persistent memory deficits even after a lower level inflammatory event. There were no differences in peripheral or hippocampal cytokine levels 8 wks post‐MI; therefore, the cognitive deficits were not due to ongoing inflammatory signaling. Future work will determine a causal role for dysregulated histone acetylation in the persistent memory deficits following an inflammatory event. Identifying the mechanisms underlying this process will provide novel targets for prevention and treatment of persistent cognitive deficits after MI, illness or major surgery.Support or Funding InformationThis research was supported by a National Institutes of Health grant (R00 MH093459, NCT)

Inhibition of monomethylarsonous acid (MMAIII)-induced cell malignant transformation through restoring dysregulated histone acetylation

Inorganic arsenic (iAs) and its high toxic metabolite, monomethylarsonous acid (MMAIII), are able to induce malignant transformation of human cells. Chronic exposure to these chemicals is associated with an increased risk of developing multiple cancers in human. However, the mechanisms contributing to iAs/MMAIII-induced cell malignant transformation and carcinogenesis are not fully elucidated. We recently showed that iAs/MMAIII exposure to human cells led to a decreased level of histone acetylation globally, which was associated with an increased sensitivity to arsenic cytotoxicity. In the current study, it demonstrated that prolonged exposure to low-level MMAIII in human urothelial cells significantly increased the expression and activity of histone deacetylases (HDACs) with an associated reduction of histone acetylation levels both globally and lysine specifically. Administration of the HDAC inhibitor, suberoylanilide hydroxamic acid (SAHA), at 4 weeks after the initial MMAIII treatment inhibited the MMAIII-mediated up-regulation of the expression and activities of HDACs, leading to increase histone acetylation and prevention of MMAIII-induced malignant transformation. These new findings suggest that histone acetylation dysregulation may be a key mechanism in MMAIII-induced malignant transformation and carcinogenesis, and that HDAC inhibitors could be targeted to prevent or treat iAs-related cancers.

De Novo Mutations of the Gene Encoding the Histone Acetyltransferase KAT6B Cause Genitopatellar Syndrome

Genitopatellar syndrome (GPS) is a rare disorder in which patellar aplasia or hypoplasia is associated with external genital anomalies and severe intellectual disability. Using an exome-sequencing approach, we identified de novo mutations of KAT6B in five individuals with GPS; a single nonsense variant and three frameshift indels, including a 4 bp deletion observed in two cases. All identified mutations are located within the terminal exon of the gene and are predicted to generate a truncated protein product lacking evolutionarily conserved domains. KAT6B encodes a member of the MYST family of histone acetyltranferases. We demonstrate a reduced level of both histone H3 and H4 acetylation in patient-derived cells suggesting that dysregulation of histone acetylation is a direct functional consequence of GPS alleles. These findings define the genetic basis of GPS and illustrate the complex role of the regulation of histone acetylation during development.

Sodium Butyrate Improves Memory Function in an Alzheimer's Disease Mouse Model When Administered at an Advanced Stage of Disease Progression

Dysregulation of histone acetylation has been implicated in the onset of age-associated memory impairment and the pathogenesis of neurodegenerative diseases. Elevation of histone acetylation via administration of histone deacetylase (HDAC) inhibitors is currently being pursued as a novel therapeutic avenue to treat memory impairment linked to Alzheimer's disease (AD). Here we show that severe amyloid pathology correlates with a pronounced dysregulation of histone acetylation in the forebrain of APPPS1-21 mice. Importantly, prolonged treatment with the pan-HDAC inhibitor sodium butyrate improved associative memory in APPPS1-21 mice even when administered at a very advanced stage of pathology. The recovery of memory function correlated with elevated hippocampal histone acetylation and increased expression of genes implicated in associative learning. These data advance our understanding of the potential applicability of HDAC inhibitors for the treatment of AD and suggest that HDAC inhibitors may have beneficial effects even when administered long after the onset of disease-associated symptoms.