Acetyl-E2F4 (K96) Antibody

What is E2F4 and why is the K96 acetylation site significant?

E2F4 is a transcription factor that belongs to the E2F family, known for regulating diverse cellular processes including cell cycle progression, DNA repair, RNA processing, stress response, apoptosis, ubiquitination, protein transport, and I-κB kinase/NF-κB cascade regulation. The K96 residue is located within the dimerization domain (DD) of E2F4 and represents one of the major acetylation sites that has been demonstrated in both human and mouse E2F4 . This site-specific post-translational modification is particularly significant because acetylation at K96 may compromise the DP heterodimerization capacity of E2F4, potentially facilitating its cytoplasmic functions as a multifactorial protein rather than its canonical nuclear role as a transcription factor .

How is acetylated E2F4 distributed in neural tissues?

Using Acetyl-E2F4 (K96)-specific antibodies, researchers have verified that K96-acetylated E2F4 can be detected in specific structures of the adult mouse brain in vivo. This acetylated form is particularly present in:

• NeuN-positive cells (neurons) within the hippocampal dentate gyrus

• Neurons in the cerebellum

• NeuN-negative cells located in the rostral migratory stream (RMS), which likely represent neural progenitors

• Some NeuN-negative cells in the cerebellum

This specific distribution pattern suggests that acetylated E2F4 may play unique roles in different neural cell populations.

What are the key structural and functional domains of E2F4 relevant to K96 acetylation?

E2F4 contains several important functional domains, including:

• DNA Binding Domain (DBD): Contains acetylation site K37

• Dimerization Domain (DD): Contains the critical K96 acetylation site

• Transactivation domain

• Pocket protein binding domain

The K96 site within the dimerization domain is particularly important because its acetylation may regulate E2F4's ability to form heterodimers with DP proteins, which is essential for its DNA-binding capacity and transcriptional activities . When K96 is acetylated, this modification may redirect E2F4 toward non-transcriptional functions, potentially explaining its observed cytoplasmic localization in specific neural tissues.

What are the optimal protocols for detecting acetylated E2F4 (K96) in brain tissue samples?

When designing experiments to detect acetylated E2F4 (K96) in brain tissues, researchers should consider the following methodological approach:

Immunohistochemistry (IHC) Protocol:

• Fix brain tissue with 4% paraformaldehyde

• Section tissue at appropriate thickness (10-30 μm)

• Perform antigen retrieval using TE buffer (pH 9.0) or alternatively citrate buffer (pH 6.0)

• Block with serum-containing buffer to reduce non-specific binding

• Incubate with Acetyl-E2F4 (K96) antibody at 1:20-1:200 dilution

• For co-localization studies, pair with neuronal markers like NeuN

• Use appropriate secondary antibodies and visualization methods

Western Blot Protocol:

• Extract proteins from brain tissue using appropriate lysis buffer

• Separate proteins by SDS-PAGE

• Transfer to membrane

• Block and incubate with Acetyl-E2F4 (K96) antibody at 1:500-1:2000 dilution

• Expected molecular weight may appear at approximately 60-70 kDa rather than the calculated 44 kDa

The specificity of detection can be validated using E2F4 knockout tissues or cells as negative controls.

How can researchers optimize immunoprecipitation experiments to study E2F4 acetylation and protein interactions?

For successful immunoprecipitation (IP) experiments investigating E2F4 acetylation and protein interactions:

• Sample preparation:

  • For brain tissue: Use 1.0-3.0 mg of total protein lysate

  • Maintain protein stability by including protease and deacetylase inhibitors

• Antibody amounts:

  • Use 0.5-4.0 μg of E2F4 antibody per IP reaction

  • For acetylation-specific studies, the Acetyl-E2F4 (K96) antibody can be used

• Controls to include:

  • IgG control IP to identify non-specific binding

  • Input samples (5-10% of lysate)

  • Reverse IP (e.g., immunoprecipitate with antibodies against interacting partners like SAS6)

• Detection strategy:

  • Western blot using antibodies against potential interacting proteins

  • Mass spectrometry for unbiased identification of interaction partners

Studies have successfully demonstrated interactions between E2F4 and proteins like SAS6 using similar approaches, where endogenous E2F4 and SAS6 were shown to interact in 293FT cell lysates through IP with anti-E2F4 antibodies followed by Western blotting for SAS6 .

What dilutions and applications are recommended for Acetyl-E2F4 (K96) antibodies?

The following applications and dilutions are recommended for optimal results with Acetyl-E2F4 (K96) antibodies:

How can Acetyl-E2F4 (K96) antibodies be utilized in studying neurodegenerative diseases?

Acetyl-E2F4 (K96) antibodies offer valuable tools for investigating neurodegenerative conditions, particularly Alzheimer's disease (AD), through several advanced research approaches:

• Comparative expression analysis: Researchers can examine differential expression and localization of acetylated E2F4 in brain tissues from AD models (such as 5xFAD mice) versus control samples. E2F4DN transgenic mice, which express a dominant-negative form of E2F4, have shown reduced microgliosis and astrogliosis even at advanced ages (1 year), suggesting E2F4's involvement in neuroinflammatory processes relevant to AD .

• Mechanistic studies: Investigating how acetylation of E2F4 at K96 might alter its function from a transcriptional regulator to a cytoplasmic factor that influences neuroinflammation and synaptic maintenance. This could reveal novel therapeutic approaches targeting E2F4 post-translational modifications.

• Biomarker development: Evaluating whether altered patterns of E2F4 acetylation correlate with disease progression, potentially establishing acetylated E2F4 as a diagnostic or prognostic biomarker for neurodegenerative conditions.

• Drug screening platforms: Using acetylation-state specific antibodies to identify compounds that modulate E2F4 acetylation as potential therapeutic agents for maintaining brain homeostasis and reducing age-associated neuroinflammation.

The E2F4DN transgenic mouse model presents a particularly promising tool for evaluating E2F4 as a therapeutic target in neuropathology and brain aging, as these mice demonstrate maintenance of reduced neuroinflammatory responses even at advanced ages .

What is the relationship between E2F4 acetylation and multiciliogenesis?

Research has uncovered an intriguing connection between E2F4 acetylation and the process of multiciliogenesis, particularly through E2F4's non-transcriptional functions:

• Protein interaction network: Acetylated E2F4 shows specific interactions with key ciliogenesis proteins. Studies have identified direct interactions between E2F4 and SAS6, a critical protein for centriole formation and multiciliogenesis . This interaction was validated through co-immunoprecipitation experiments in 293FT cells, where endogenous E2F4 and SAS6 were found to interact .

• Domain-specific interactions: The interaction between E2F4 and SAS6 involves the amino-terminal region of SAS6 (residues 1-175), which encompasses the pisa motif (residues 39-91) and motif II (residues 123-140) . These domains are critical for SAS6 multimerization during centriole formation.

• Functional implications: E2F4's acetylation status, particularly at K96 within the dimerization domain, may regulate its ability to interact with ciliogenesis factors like SAS6 and Deup1. E2F4 has been shown to interact specifically with the N-terminal region of Deup1 (residues 1-129), which includes its first coiled-coil domain .

• Disease relevance: Mutations in the SAS6 region that interacts with E2F4 have been identified in ciliopathies, including a point mutation (I62T) found in a family with autosomal recessive primary microcephaly . This suggests that disruption of the E2F4-SAS6 interaction may contribute to ciliopathy phenotypes.

These findings highlight a novel, non-transcriptional role for E2F4 in multiciliogenesis that may be regulated by its acetylation status, particularly at sites like K96 that affect protein-protein interactions.

How should researchers address discrepancies between calculated and observed molecular weights of E2F4?

When working with E2F4 antibodies, researchers often encounter a significant discrepancy between the calculated molecular weight (44 kDa) and the observed molecular weight on Western blots (60-70 kDa) . This discrepancy can be addressed and interpreted in several ways:

• Post-translational modifications: E2F4 undergoes multiple post-translational modifications, including acetylation at numerous lysine residues (K20, K28, K37, K44, K73, K82, K96, K101, K177, K197, K230, and K347 in human E2F4) . These modifications can significantly alter the protein's migration pattern on SDS-PAGE.

• Validation approaches:

  • Use E2F4 knockout or knockdown samples as negative controls

  • Compare multiple antibodies targeting different E2F4 epitopes

  • Pre-treat samples with phosphatases or deacetylases to assess the contribution of modifications

• Technical considerations:

  • Ensure proper sample preparation (complete denaturation)

  • Optimize gel percentage for the appropriate molecular weight range

  • Consider using gradient gels for better resolution

• Interpretation guidelines:

  • The 60-70 kDa band is the validated size for E2F4 detection in multiple cell lines, including A431, Jurkat, HL-60, Raji, HeLa, and NIH/3T3 cells

  • Different acetylation states may result in subtle mobility shifts that can be detected with acetylation-specific antibodies

  • When detecting acetylated forms, compare with total E2F4 levels to normalize for expression differences

What are the critical controls for validating the specificity of Acetyl-E2F4 (K96) antibody staining in immunohistochemistry?

To ensure specificity of Acetyl-E2F4 (K96) antibody staining in immunohistochemistry, researchers should implement these critical controls:

• Negative controls:

  • Omission of primary antibody while maintaining all other steps

  • Substitution with isotype-matched IgG at equivalent concentration

  • E2F4 knockout tissue (gold standard negative control)

  • Peptide competition assay using the non-acetylated K96-containing peptide

• Specificity controls:

  • Peptide competition with the acetylated K96 peptide (should abolish specific staining)

  • Comparison with staining pattern of total E2F4 antibody (should show overlap but not identical patterns)

  • Treatment of samples with deacetylases prior to staining (should reduce acetyl-specific signal)

• Positive controls:

  • Known positive tissues: dentate gyrus of hippocampus, cerebellum, and rostral migratory stream for mouse samples

  • Co-staining with neuronal markers (NeuN) to confirm cell type-specific expression patterns as previously documented

• Cross-validation:

  • Confirmation of results using alternative detection methods (Western blot, IF)

  • Use of multiple antibodies targeting the same modification from different vendors or clones

By implementing these controls, researchers can confidently interpret their immunohistochemistry results and avoid false positives or negatives when studying acetylated E2F4.

How can researchers differentiate between nuclear and cytoplasmic functions of acetylated E2F4?

Differentiating between the nuclear and cytoplasmic functions of acetylated E2F4 requires specialized experimental approaches:

• Subcellular fractionation and Western blotting:

  • Prepare pure nuclear and cytoplasmic fractions

  • Use the Acetyl-E2F4 (K96) antibody to detect distribution in each fraction

  • Include controls for fraction purity (e.g., HDAC1 for nucleus, GAPDH for cytoplasm)

  • Compare acetylated E2F4 distribution to total E2F4 distribution

• Immunofluorescence co-localization:

  • Perform dual staining with Acetyl-E2F4 (K96) antibody and markers for specific subcellular compartments

  • Use confocal microscopy for precise localization

  • Quantify nuclear vs. cytoplasmic signal ratios

  • Compare with distribution of total E2F4

• Functional assays:

  • ChIP assays to assess DNA binding capacity of acetylated E2F4

  • Co-IP experiments to identify differential protein interactions in nuclear vs. cytoplasmic fractions

  • Compare interaction profiles of acetylated E2F4 with ciliogenesis factors like SAS6 (cytoplasmic function) vs. transcriptional partners (nuclear function)

• Mutation-based approaches:

  • Use K96R mutants (preventing acetylation) to assess nuclear retention

  • Use K96Q mutants (mimicking acetylation) to evaluate cytoplasmic relocalization

  • Compare functional outcomes in each compartment

Research has shown that acetylation of K96, located in the dimerization domain, may compromise E2F4's capacity for DP heterodimerization, potentially facilitating its cytoplasmic functions as a multifactorial protein rather than its canonical nuclear role as a transcription factor . The demonstrated interaction of E2F4 with ciliogenesis factors like SAS6 further supports its non-transcriptional cytoplasmic functions .

What is the therapeutic potential of targeting E2F4 acetylation in neurological disorders?

Recent research suggests that targeting E2F4 acetylation holds promising therapeutic potential for neurological disorders, particularly Alzheimer's disease and age-related neuroinflammation:

• Evidence from transgenic models: Studies with E2F4DN transgenic mice have demonstrated that modulating E2F4 function reduces microgliosis and astrogliosis in both Alzheimer's disease models (5xFAD/E2F4DN mice) and in normal aging. Importantly, this reduced neuroinflammation is maintained even at late stages (1 year of age), highlighting E2F4's role as a brain homeostatic agent .

• Acetylation-specific targeting strategies:

  • Development of small molecules that specifically modulate K96 acetylation

  • Targeted protein degradation approaches specific to acetylated E2F4

  • Gene therapy approaches delivering acetylation-resistant E2F4 variants

• Biomarker applications: Changes in E2F4 acetylation patterns could serve as biomarkers for disease progression or treatment response in neurodegenerative conditions.

• Dual-targeting approaches: Since E2F4 functions in both transcriptional regulation and cytoplasmic processes like multiciliogenesis, therapeutic strategies could target both pathways:

  • Modulating neuroinflammatory gene expression through E2F4's transcriptional function

  • Enhancing multicilia function through E2F4's interaction with ciliogenesis factors like SAS6

These findings position E2F4DN transgenic mice as a valuable tool for evaluating E2F4 as a therapeutic target in neuropathology and brain aging, with acetylation-specific modulation offering a potential mechanism for intervention .

How do the various acetylation sites on E2F4 differentially regulate its multiple cellular functions?

E2F4 undergoes acetylation at multiple lysine residues, with differential effects on its diverse cellular functions:

• Major acetylation sites and their locations:

  • K37: Located within the DNA Binding Domain (DBD)

  • K96: Located within the Dimerization Domain (DD)

  • Additional acetylation has been detected at K20, K28, K44, K73, K82, K101, K177, K197, K230, and K347 in human E2F4

• Functional consequences by domain:

  • DBD acetylation (e.g., K37): May compromise DNA binding capacity, affecting E2F4's ability to regulate transcription

  • DD acetylation (e.g., K96): May affect DP heterodimerization, potentially facilitating cytoplasmic functions

  • Combined acetylation patterns likely create a "code" that directs E2F4 toward specific functions

• Cell type-specific patterns:

  • Acetylated K96 has been detected in specific neural populations, including neurons in the hippocampal dentate gyrus and cerebellum, as well as in NeuN-negative cells in the rostral migratory stream

  • These patterns suggest cell type-specific regulation of E2F4 acetylation

• Regulatory mechanisms:

  • The acetyltransferases and deacetylases controlling E2F4 acetylation state represent potential therapeutic targets

  • Cross-talk between different acetylation sites may create complex regulatory networks

Understanding the differential effects of acetylation at various sites will require systematic studies comparing the functional consequences of site-specific mutations (e.g., K→R to prevent acetylation or K→Q to mimic acetylation) on E2F4's diverse cellular roles, from transcriptional regulation to cytoplasmic functions in processes like multiciliogenesis .

What emerging techniques are advancing the study of site-specific protein acetylation in neuroscience?

Several cutting-edge techniques are revolutionizing the study of site-specific protein acetylation, including E2F4 K96 acetylation, in neuroscience:

• Acetylome profiling with mass spectrometry:

  • Targeted parallel reaction monitoring (PRM) for quantitative analysis of specific acetylation sites

  • SILAC-based approaches for comparing acetylation states across experimental conditions

  • Development of improved enrichment methods for acetylated peptides from brain tissue

• Site-specific acetylation sensors:

  • FRET-based biosensors that report on real-time acetylation status of specific sites

  • Split-GFP complementation systems sensitive to acetylation-dependent protein interactions

  • These approaches could monitor E2F4 K96 acetylation dynamics in living cells

• Genetic code expansion for acetylation studies:

  • Incorporation of acetyl-lysine directly during protein synthesis using modified tRNA synthetases

  • Generation of homogeneously acetylated E2F4 for structural and functional studies

  • Production of acetylation-state specific E2F4 variants for in vivo studies

• Single-cell acetylation analysis:

  • Combining single-cell proteomics with acetylation-specific antibodies

  • Spatial transcriptomics correlated with acetylation patterns in brain tissue sections

  • These approaches could reveal cell type-specific regulation of E2F4 acetylation in complex neural tissues

• CRISPR-based acetylation modulation:

  • Targeted acetylation using dCas9-acetyltransferase fusions

  • Precise deacetylation using dCas9-deacetylase systems

  • These tools could allow manipulation of E2F4 acetylation state at specific sites to dissect functional consequences

These emerging technologies offer unprecedented opportunities to understand the complex regulation and functional significance of site-specific acetylation of proteins like E2F4 in neural development, function, and disease.