GO:0043996 histone H4K8 acetyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0043996 (histone H4K8 acetyltransferase activity) is a molecular function that catalyzes acetyl transfer from acetyl-CoA to lysine 8 of histone H4, producing CoA and H4K8ac.
• H4K8 acetylation is a chromatin mark associated with transcriptional activation and is dynamically regulated by acetyltransferases and deacetylases.
• Enzymes with H4K8 acetyltransferase activity include hnRNPA2, which was shown to acetylate H4K8 in response to mitochondrial stress.
• Dysregulation of H4K8 acetylation is implicated in metabolic liver disease, viral hepatitis, and neurobehavioral disorders.
• Small molecules and metabolic intermediates can modulate H4K8 acetyltransferase activity, offering therapeutic entry points.
• CRISPR-based knockout, knock-in, and overexpression models enable causal dissection of H4K8 acetyltransferase function in disease.
Description
Histone H4 lysine 8 acetylation (H4K8ac) is a well-characterized chromatin modification that influences gene expression, DNA repair, and replication. The enzyme activity responsible for depositing this mark is classified under the Gene Ontology term GO:0043996, histone H4K8 acetyltransferase activity, which specifically catalyzes the transfer of an acetyl group from acetyl-CoA to histone H4 at lysine 8. This activity is distinct from other histone acetyltransferase activities due to its substrate specificity for H4K8. Understanding GO:0043996 is critical because H4K8 acetylation has been linked to diverse physiological and pathological processes, including lipid metabolism, viral replication, and neuronal function. Researchers studying chromatin regulation, epigenetic drugs, and disease mechanisms require precise tools to measure and manipulate this activity. This article synthesizes authoritative GO annotations and verified PubMed literature to provide a research-grade overview of GO:0043996, its mechanisms, key genes, disease relevance, and experimental strategies.
histone H4K8 acetyltransferase activity At A Glance
| GO ID | GO:0043996 |
|---|---|
| GO term | histone H4K8 acetyltransferase activity |
| Ontology | molecular_function |
| Synonym | histone acetylase activity (H4-K8 specific); histone acetyltransferase activity (H4-K8 specific); histone lysine N-acetyltransferase activity (H4-K8 specific) |
| Major function | Catalyzes acetylation of histone H4 at lysine 8 using acetyl-CoA as acetyl donor |
| Reaction | acetyl-CoA + histone H4 L-lysine (position 8) = CoA + histone H4 N6-acetyl-L-lysine (position 8) |
| Substrate | Histone H4 (lysine 8) and acetyl-CoA |
| Product | H4K8-acetylated histone H4 and CoA |
| Cellular context | Nuclear chromatin; associated with transcriptional regulation |
What Is GO:0043996?
GO:0043996, histone H4K8 acetyltransferase activity, is defined as the catalysis of the reaction: acetyl-CoA + histone H4 L-lysine (position 8) = CoA + histone H4 N6-acetyl-L-lysine (position 8). In other words, it is an enzymatic activity that transfers an acetyl group from acetyl-CoA to the epsilon-amino group of lysine 8 on histone H4, resulting in H4K8 acetylation and release of coenzyme A. This activity is a molecular function and is specific for histone H4 at position 8, distinguishing it from other lysine acetyltransferases that target different histone residues or non-histone proteins.
Why Is histone H4K8 acetyltransferase activity Important in Cell Biology?
GO:0043996 is important because H4K8 acetylation is a key epigenetic mark that regulates chromatin accessibility and gene expression programs. Dysregulation of this activity has been observed in metabolic disorders such as nonalcoholic fatty liver disease, where free fatty acids enhance histone acetyltransferase activity and lipid accumulation. In viral infections, H4K8 acetylation on HBV cccDNA is modulated by interferon-alpha, affecting viral transcription. In the nervous system, ethanol exposure increases CB1R Exon1 H4K8 acetylation, contributing to neurobehavioral abnormalities. Furthermore, hnRNPA2, an enzyme with H4K8 acetyltransferase activity, mediates mitochondrial stress-induced nuclear gene expression and telomere length regulation. Thus, understanding GO:0043996 provides insights into fundamental chromatin biology and multiple human diseases.
• Regulates transcriptional activation through chromatin remodeling.
• Implicated in metabolic liver disease and lipid accumulation.
• Modulates hepatitis B virus transcription and replication.
• Linked to neurobehavioral abnormalities after ethanol exposure.
• Involved in mitochondrial stress responses and telomere maintenance.
• Target for small-molecule modulators of acetyltransferase activity.
• Serves as a biomarker for epigenetic changes in addiction and neurodegeneration.
• Provides a mechanistic link between metabolism and gene expression.
• Enables CRISPR-based functional studies of chromatin regulators.
• Potential therapeutic target for fatty liver disease and viral hepatitis.
What Happens During histone H4K8 acetyltransferase activity?
Substrate recognition and binding
In simple terms: The enzyme finds and grabs onto histone H4 and acetyl-CoA.
The first step in H4K8 acetylation involves specific recognition of histone H4 by the acetyltransferase enzyme. The enzyme binds to the histone H4 tail, positioning lysine 8 near the catalytic site. This binding is often facilitated by other chromatin-associated proteins and depends on the local chromatin context. For example, hnRNPA2 was shown to interact with histone H4 and acetylate it at K8 in response to mitochondrial stress. The specificity for H4K8 is determined by the enzyme's active site architecture and surrounding residues, which discriminate against other lysine residues.
Acetyl transfer from acetyl-CoA
In simple terms: The enzyme transfers an acetyl group from acetyl-CoA onto lysine 8 of histone H4.
Once bound, the enzyme catalyzes the transfer of an acetyl group from the cofactor acetyl-CoA to the epsilon-amino group of histone H4 lysine 8. This reaction proceeds via a ternary complex mechanism, resulting in the formation of H4K8-acetylated histone and coenzyme A. The activity is dependent on acetyl-CoA availability, which reflects cellular metabolic status. In HepG2 cells, free fatty acids increase histone acetyltransferase activity, likely by elevating acetyl-CoA levels and promoting H4K8 acetylation.
Chromatin remodeling and transcriptional consequences
In simple terms: The added acetyl mark loosens chromatin and helps turn genes on.
Acetylation of H4K8 neutralizes the positive charge of lysine, weakening histone-DNA interactions and promoting an open chromatin conformation. This facilitates access for transcription factors and RNA polymerase II, leading to transcriptional activation. H4K8 acetylation is often found at promoters and enhancers of active genes. In the context of HBV cccDNA, interferon-alpha promotes HDAC3-mediated de-2-hydroxyisobutyrylation of H4K8, which is linked to transcriptional repression of viral genes. Thus, the balance between acetylation and deacetylation at H4K8 directly impacts gene expression programs.
Regulation by deacetylases and metabolic signals
In simple terms: Other enzymes can remove the acetyl mark, and cellular signals can change the balance.
The H4K8 acetylation mark is reversible and is removed by histone deacetylases (HDACs). For instance, HDAC3 can deacetylate H4K8, and its activity is modulated by interferon-alpha in liver cells. Additionally, metabolic signals such as free fatty acids can enhance H4K8 acetyltransferase activity, while small molecules like 3,4-dihydroxytoluene inhibit p300 histone acetyltransferase activity, reducing H4K8 acetylation and ameliorating fatty liver disease in mice. This dynamic regulation ensures that H4K8 acetylation responds to cellular and environmental cues.
Key Genes Involved in GO:0043996 histone H4K8 acetyltransferase activity
The following genes and proteins are directly or indirectly associated with histone H4K8 acetyltransferase activity (GO:0043996) based on verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| HNRNPA2 | Novel histone acetyltransferase that acetylates H4K8 in response to mitochondrial stress | Mediates mitochondrial stress-induced nuclear gene expression and telomere length regulation |
| EP300 | Histone acetyltransferase p300; can acetylate H4K8 and is inhibited by 3,4-dihydroxytoluene | Target for nonalcoholic fatty liver disease therapy |
| HDAC3 | Histone deacetylase that removes acetylation marks, including H4K8 | Modulates HBV transcription via de-2-hydroxyisobutyrylation of H4K8 |
| CB1R | Cannabinoid receptor 1; its Exon1 histone H4K8 acetylation is increased by ethanol | Linked to neurobehavioral abnormalities in adult mice |
| H4C1 | Histone H4 cluster 1; substrate for H4K8 acetylation | Core chromatin component; mutations affect acetylation |
| H4C2 | Histone H4 cluster 2; substrate for H4K8 acetylation | Core chromatin component |
| H4C3 | Histone H4 cluster 3; substrate for H4K8 acetylation | Core chromatin component |
| H4C4 | Histone H4 cluster 4; substrate for H4K8 acetylation | Core chromatin component |
| H4C5 | Histone H4 cluster 5; substrate for H4K8 acetylation | Core chromatin component |
| H4C6 | Histone H4 cluster 6; substrate for H4K8 acetylation | Core chromatin component |
| H4C7 | Histone H4 cluster 7; substrate for H4K8 acetylation | Core chromatin component |
| H4C8 | Histone H4 cluster 8; substrate for H4K8 acetylation | Core chromatin component |
| H4C9 | Histone H4 cluster 9; substrate for H4K8 acetylation | Core chromatin component |
| H4C10 | Histone H4 cluster 10; substrate for H4K8 acetylation | Core chromatin component |
| H4C11 | Histone H4 cluster 11; substrate for H4K8 acetylation | Core chromatin component |
| H4C12 | Histone H4 cluster 12; substrate for H4K8 acetylation | Core chromatin component |
| H4C13 | Histone H4 cluster 13; substrate for H4K8 acetylation | Core chromatin component |
| H4C14 | Histone H4 cluster 14; substrate for H4K8 acetylation | Core chromatin component |
How Is histone H4K8 acetyltransferase activity Regulated?
Histone H4K8 acetyltransferase activity is regulated at multiple levels. Metabolically, acetyl-CoA availability directly influences the reaction rate, as seen in HepG2 cells where free fatty acids enhance histone acetyltransferase activity and lipid accumulation. Small molecules can modulate activity; for example, 3,4-dihydroxytoluene inhibits p300 histone acetyltransferase activity, reducing H4K8 acetylation and suppressing nonalcoholic fatty liver disease progression in mice. Viral infections and immune signaling also play a role: interferon-alpha promotes HDAC3-mediated de-2-hydroxyisobutyrylation of H4K8 on HBV cccDNA, altering viral transcription. In the brain, ethanol exposure increases CB1R Exon1 H4K8 acetylation, contributing to neurobehavioral abnormalities. Additionally, mitochondrial dysfunction induces hnRNPA2-mediated H4K8 acetylation, linking cellular stress to nuclear gene expression. These diverse regulatory inputs underscore the integration of H4K8 acetylation with cellular metabolism, stress responses, and immune signaling.
histone H4K8 acetyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| EP300 | Nonalcoholic fatty liver disease | HepG2 cells treated with free fatty acids; p300 inhibitor |
| HDAC3 | Hepatitis B virus infection | HBV-infected hepatocytes treated with IFN-alpha |
| CB1R | Ethanol-induced neurobehavioral abnormalities | Neonatal mice exposed to ethanol |
| HNRNPA2 | Mitochondrial dysfunction and telomere shortening | Cells with induced mitochondrial stress |
| H4C1 | Chromatin regulation in metabolic disease | CRISPR knockout of H4K8 acetyltransferase in HepG2 |
Nonalcoholic fatty liver disease (NAFLD)
Histone H4K8 acetyltransferase activity is implicated in NAFLD pathogenesis. Free fatty acids induce histone acetyltransferase activity in HepG2 cells, accelerating lipid accumulation. Inhibition of p300 histone acetyltransferase activity by 3,4-dihydroxytoluene reduces H4K8 acetylation and suppresses NAFLD progression in mice. These findings suggest that targeting H4K8 acetylation may be therapeutic for fatty liver disease.
Hepatitis B virus infection
H4K8 acetylation on HBV cccDNA minichromosome is regulated by interferon-alpha. IFN-alpha promotes HDAC3-mediated de-2-hydroxyisobutyrylation of H4K8, which inhibits HBV transcription and replication in liver cells. This highlights the role of H4K8 acetylation in host-virus interactions and antiviral defense.
Neurobehavioral disorders and addiction
Ethanol exposure during neonatal development enhances CB1R Exon1 histone H4K8 acetylation, up-regulating CB1R function and causing neurobehavioral abnormalities in adult mice. Additionally, the epigenetic landscape of amphetamine and methamphetamine addiction involves changes in histone acetylation, including H4K8, in rodent models. These studies link H4K8 acetylation to addiction and neurodevelopmental disorders.
Mitochondrial dysfunction and telomere regulation
hnRNPA2, a novel histone acetyltransferase, mediates mitochondrial stress-induced nuclear gene expression by acetylating H4K8. This activity also reduces telomere length in response to mitochondrial dysfunction. Thus, H4K8 acetylation connects mitochondrial health to nuclear gene regulation and telomere maintenance, with implications for aging and degenerative diseases.
From histone H4K8 acetyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of H4K8 acetyltransferase reduce lipid accumulation? | Knockout of EP300 or HNRNPA2 in HepG2 cells |
| Does a specific point mutation in the catalytic domain abolish H4K8 acetylation? | Point mutation knock-in of catalytic residues in HNRNPA2 |
| Can H4K8 acetylation be monitored in live cells? | Knock-in of fluorescent reporter at H4K8 locus |
| Does overexpression of hnRNPA2 enhance mitochondrial stress response? | Overexpression of HNRNPA2 in cell lines |
| Does HDAC3-mediated deacetylation affect HBV replication? | Knockout of HDAC3 in HBV-infected hepatocytes |
| Can small molecules modulate H4K8 acetylation? | Overexpression of p300 with inhibitor treatment |
How to Study the histone H4K8 acetyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| ChIP-qPCR | Enrichment of H4K8ac at specific loci | Promoter acetylation after drug treatment |
| ChIP-seq | Genome-wide H4K8ac distribution | Epigenomic profiling |
| In vitro acetyltransferase assay | Catalytic activity of candidate enzymes | Enzyme kinetics and inhibitor testing |
| Western blot | Global H4K8ac levels | Validation of acetylation changes |
| Immunofluorescence | Subcellular localization of H4K8ac | Visualization of chromatin marks |
| Mass spectrometry | Identification of acetylation sites | Confirmation of H4K8 specificity |
| CRISPR screen | Genes regulating H4K8ac | Discovery of novel regulators |
| Co-immunoprecipitation | Protein-protein interactions | Identification of acetyltransferase complexes |
Chromatin immunoprecipitation (ChIP)
ChIP with anti-H4K8ac antibodies is used to map the genomic distribution of H4K8 acetylation. This method reveals whether H4K8 acetylation is enriched at specific promoters or enhancers, as shown for CB1R Exon1 after ethanol exposure and HBV cccDNA. ChIP-qPCR or ChIP-seq provides quantitative and genome-wide profiles.
Histone acetyltransferase activity assays
In vitro acetyltransferase assays using recombinant histone H4 and acetyl-CoA measure the catalytic activity of candidate enzymes. These assays can be coupled with mass spectrometry to confirm H4K8-specific acetylation. Free fatty acid-induced histone acetyltransferase activity was measured in HepG2 cells using such assays. Inhibitor studies with 3,4-dihydroxytoluene also employed activity assays.
Western blotting and immunofluorescence
Western blotting with anti-H4K8ac antibodies quantifies global changes in H4K8 acetylation. Immunofluorescence can visualize H4K8ac foci in situ. These methods were used to detect changes in H4K8 acetylation after IFN-alpha treatment and in oocyte ageing.
CRISPR-based genetic screens
Genome-wide CRISPR knockout or activation screens can identify genes that regulate H4K8 acetylation. By coupling H4K8ac staining with flow cytometry or sequencing, researchers can discover novel acetyltransferases and deacetylases. This approach is powerful for unbiased discovery of regulators of GO:0043996.
How CRISPR Can Be Used to Study GO:0043996 histone H4K8 acetyltransferase activity
Knockout
CRISPR knockout of genes encoding H4K8 acetyltransferases (e.g., HNRNPA2, EP300) can abolish or reduce H4K8 acetylation. This approach is used to study loss-of-function phenotypes in metabolic liver disease and mitochondrial stress responses. Knockout cell models enable downstream analysis of gene expression, lipid accumulation, and telomere length.
Point Mutation
Introducing point mutations in the catalytic domain of H4K8 acetyltransferases can dissect the enzymatic activity from scaffolding functions. For example, mutating key residues in hnRNPA2 can test whether its acetyltransferase activity is required for mitochondrial stress-induced nuclear gene expression. Point mutation knock-in models provide precise mechanistic insights.
Knock-in
Knock-in of epitope tags or fluorescent reporters at the endogenous H4K8 acetyltransferase locus allows real-time tracking of enzyme expression and localization. Additionally, knock-in of histone H4 with a K8R mutation can prevent acetylation at this site, serving as a dominant-negative model to study the specific role of H4K8ac.
Overexpression
Overexpression of H4K8 acetyltransferases such as hnRNPA2 or p300 can enhance H4K8 acetylation and drive downstream transcriptional programs. This is useful for gain-of-function studies, including lipid accumulation in HepG2 cells and mitochondrial stress responses. Overexpression models also facilitate drug screening for inhibitors of H4K8 acetylation.
How EDITGENE Supports histone H4K8 acetyltransferase activity Research
Researchers studying histone H4K8 acetyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in H4K8 acetylation and its downstream phenotypes. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of genes associated with GO:0043996.
Contact EDITGENE today to design your custom CRISPR model for histone H4K8 acetyltransferase activity research.
Frequently Asked Questions About histone H4K8 acetyltransferase activity
What is histone H4K8 acetyltransferase activity?
It is an enzymatic activity (GO:0043996) that transfers an acetyl group from acetyl-CoA to lysine 8 of histone H4, resulting in H4K8 acetylation and CoA release.
What genes are involved in histone H4K8 acetyltransferase activity?
Key genes include HNRNPA2, EP300, and HDAC3, as well as histone H4 genes (H4C1-H4C14) that serve as substrates.
How is H4K8 acetylation regulated?
It is regulated by acetyl-CoA availability, opposing deacetylases (e.g., HDAC3), and signaling pathways such as interferon-alpha and mitochondrial stress.
What diseases are associated with H4K8 acetylation?
Nonalcoholic fatty liver disease, hepatitis B virus infection, neurobehavioral disorders, and mitochondrial dysfunction-related conditions.
How can I measure histone H4K8 acetyltransferase activity?
In vitro acetyltransferase assays, ChIP, Western blot, and mass spectrometry are commonly used to measure activity and acetylation levels.
Can CRISPR be used to study H4K8 acetylation?
Yes, CRISPR knockout, knock-in, and overexpression models enable functional studies of genes regulating H4K8 acetylation.
What is the role of hnRNPA2 in H4K8 acetylation?
hnRNPA2 is a novel histone acetyltransferase that acetylates H4K8 in response to mitochondrial stress, mediating nuclear gene expression and telomere length regulation.
How does ethanol affect H4K8 acetylation?
Ethanol exposure increases CB1R Exon1 H4K8 acetylation, up-regulating CB1R function and causing neurobehavioral abnormalities in adult mice.
What small molecules inhibit H4K8 acetyltransferase activity?
3,4-dihydroxytoluene inhibits p300 histone acetyltransferase activity, reducing H4K8 acetylation and suppressing NAFLD progression in mice.
How does interferon-alpha affect H4K8 acetylation in HBV?
IFN-alpha promotes HDAC3-mediated de-2-hydroxyisobutyrylation of H4K8 on HBV cccDNA, inhibiting viral transcription and replication.
Conclusion
Histone H4K8 acetyltransferase activity (GO:0043996) is a fundamental chromatin-modifying function that regulates gene expression in health and disease. Its dysregulation contributes to metabolic liver disease, viral hepatitis, neurobehavioral disorders, and mitochondrial stress responses. The reversibility of H4K8 acetylation and its sensitivity to metabolic and pharmacological cues make it an attractive therapeutic target. Advances in CRISPR-based models and epigenomic profiling will continue to elucidate the precise roles of H4K8 acetyltransferases, paving the way for novel interventions. EDITGENE's comprehensive services support researchers in dissecting this activity with precision and scale.
References
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- 5. Zhao LN et al.. 2022. IFN-α inhibits HBV transcription and replication by promoting HDAC3-mediated de-2-hydroxyisobutyrylation of histone H4K8 on HBV cccDNA minichromosome in liver.. Acta Pharmacol Sin 43(6):1484-1494 PMID: 34497374
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