ATF4 (Ab-219) Antibody

What is the ATF4 (Ab-219) Antibody and what epitope does it recognize?

ATF4 (Ab-219) Antibody is a rabbit polyclonal antibody that specifically recognizes the C-terminal region of human ATF4 (Activating transcription factor 4). It is affinity-purified from rabbit antiserum using epitope-specific immunogen chromatography . This antibody detects endogenous levels of total ATF4 protein, which has a molecular weight of approximately 39kDa as determined by SDS-PAGE .

Methodologically, when using this antibody, researchers should be aware that it's designed to recognize the native protein configuration rather than denatured fragments, making it particularly suitable for Western blot applications where protein integrity is maintained through proper sample preparation.

What species reactivity does the ATF4 (Ab-219) Antibody demonstrate?

When planning experiments with non-validated species, researchers should perform preliminary Western blot analysis using positive control samples to confirm antibody specificity and determine optimal working dilutions.

What is the recommended storage and handling protocol for ATF4 (Ab-219) Antibody?

The antibody should be stored at -20°C in its formulation of rabbit IgG in phosphate-buffered saline (without Mg²⁺ and Ca²⁺), pH 7.4, containing 150mM NaCl, 0.02% sodium azide, and 50% glycerol . For optimal performance:

• Avoid repeated freeze-thaw cycles by aliquoting the antibody upon first thaw

• Working dilutions should be prepared fresh before use

• Allow the antibody to reach room temperature before opening the vial

• Centrifuge briefly before use to collect contents at the bottom of the tube

How should I validate ATF4 antibody specificity in my experimental system?

Validating antibody specificity is crucial for reliable results. A comprehensive validation approach includes:

• Positive controls: Using cell lines or tissues with known ATF4 expression

• Knockdown/knockout validation: Compare staining in ATF4-expressing vs. ATF4-knockout or knockdown samples

• Peptide competition assay: Pre-incubating the antibody with the immunizing peptide should abolish specific signals

• Multiple antibody comparison: Comparing results with other validated ATF4 antibodies targeting different epitopes

In published research, specificity of anti-ATF4 antibodies has been demonstrated through both immunoprecipitation and Western blot experiments with cells transfected by HA-ATF4, comparing results with those obtained by Western blotting with untransfected 293T cells .

What are the optimal conditions for using ATF4 (Ab-219) Antibody in Western blotting?

For optimal Western blot results with ATF4 (Ab-219) Antibody:

• Sample preparation:

  • Extract proteins in a buffer containing protease inhibitors

  • Include phosphatase inhibitors if studying phosphorylated ATF4

  • Denature samples at 95°C for 5 minutes in Laemmli buffer

• Gel electrophoresis:

  • Use SDS-12% PAGE for optimal separation

  • Include positive controls and molecular weight markers

• Transfer and detection:

  • Transfer proteins to PVDF or nitrocellulose membranes

  • Block with 5% non-fat milk or BSA in TBST

  • Dilute primary antibody appropriately (optimal dilution should be determined experimentally)

  • Use appropriate HRP-conjugated secondary antibody

  • Develop using chemiluminescence detection

For quantitative analysis, chemiluminescent signals can be quantified using image analysis software such as NIH Image .

How can I study ATF4 phosphorylation at Ser-219 in the context of neuronal plasticity?

ATF4 phosphorylation at Ser-219 is particularly important in long-term potentiation (LTP). To study this:

• Experimental model setup:

  • Use chemically induced LTP (cLTP) in hippocampal slices as a model system

  • This model facilitates molecular studies by modifying the bulk of synapses simultaneously

• Time course analysis:

  • Collect time-matched samples at regular intervals (every 5 minutes) following cLTP induction

  • Research indicates that phosphorylated ATF4 levels peak approximately 20-25 minutes post-induction

• Detection methods:

  • Use specific anti-pSer219-ATF4 antibodies for immunohistochemistry

  • Perform confocal microscopy with nuclear counterstaining (e.g., TO-PRO-3)

  • Quantify immunofluorescence intensity relative to controls

• Validation approaches:

  • Use PKA inhibitors to confirm the role of cAMP-dependent protein kinase in ATF4 phosphorylation

  • Apply proteasome inhibitors (e.g., β-lactone) to prevent ATF4 degradation and confirm ubiquitin-proteasome pathway involvement

Research has shown that ATF4 phosphorylation remains low during early stages (0-10 min) after cLTP induction but increases significantly around 15-20 minutes post-induction (173.9% ± 5.9% compared to control levels of 99.2% ± 7.6%) .

What role does the ubiquitin-proteasome pathway play in ATF4 degradation and how can I study this?

The ubiquitin-proteasome pathway plays a crucial role in ATF4 degradation, particularly in neuronal plasticity contexts. To investigate this mechanism:

• Experimental design:

  • Use proteasome inhibitors (e.g., β-lactone) to prevent ATF4 degradation

  • Apply neddylation inhibitors like MLN4924 (pevonedistat) to block cullin-RING ligase activity

• Key mechanistic components to analyze:

  • Focus on SCF (Skp1-Cullin-F-box) ubiquitin ligases, particularly SCFβTRCP

  • Study the relationship between ATF4 phosphorylation at Ser-219 and subsequent ubiquitination

  • Examine the DSGXXXS motif around Ser-219 (similar to the β-TrCP recognition motif)

• Technical approaches:

  • Co-immunoprecipitation experiments to detect ATF4-βTrCP interactions

  • Western blotting to monitor ATF4 levels and ubiquitination

  • Site-directed mutagenesis of key residues (D218N, S219N, G220A, S224N) to confirm functional importance

Research has shown that inhibition of neddylation with MLN4924 significantly prevents ATF4 degradation during LTP, providing evidence that SCFβTRCP is likely responsible for attaching polyubiquitin to ATF4 .

How can I investigate ATF4 dimerization partners and their functional significance?

ATF4 functions through heterodimerization with various partners. To study these interactions:

• Experimental approaches:

  • Yeast two-hybrid screening to identify potential interaction partners

  • Co-immunoprecipitation coupled with mass spectrometry

  • Chromatin immunoprecipitation (ChIP) to identify co-bound regions

• Analysis of dimerization specificity:

  • Focus on bZIP family members as primary dimerization partners

  • Examine the 14 validated ATF4 dimerization partners identified in systematic reviews

  • Pay particular attention to C/EBP and AP-1 family members that show high binding profile similarity to ATF4

• Functional validation:

  • Use electrophoretic mobility shift assays (EMSA) to study binding to different DNA motifs

  • Apply reporter gene assays to assess transcriptional activity of different ATF4 dimers

  • Perform ChIP-seq with different stress conditions to map genome-wide binding profiles

Research has shown that ATF4 binding profiles are most similar to C/EBP and AP-1 family members, and ATF4 can bind various motifs including C/EBP-ATF, CRE, and BATF-ATF motifs depending on its dimerization partner .

How does ATF4 contribute to hematopoiesis and how can I study this using ATF4 antibodies?

ATF4 plays a crucial role in hematopoietic stem cell maintenance and erythropoiesis:

• Experimental models:

  • Use conditional knockout mouse models with cell-type-specific Cre lines (e.g., Mx1-Cre for hematopoietic cells)

  • Apply 5-fluorouracil-induced stress to study recovery of hematopoietic lineages

• Phenotypic analysis:

  • Assess erythroid differentiation using flow cytometry

  • Examine hematopoietic stem cell function through competitive transplantation assays

  • Monitor development of hypoplastic anemia in Atf4-deficient models

• Molecular mechanism investigation:

  • Use ChIP with ATF4 antibodies to confirm direct regulation of Rps19bp1

  • Analyze ribosome biogenesis through polysome profiling

  • Perform rescue experiments by expressing Rps19bp1 in Atf4-deficient cells

Research has demonstrated that ATF4 directly regulates Rps19bp1 transcription, which is involved in 40S ribosomal subunit assembly, coordinating ribosome biogenesis to promote erythropoiesis .

What post-translational modifications (PTMs) of ATF4 can be studied and what is their functional significance?

ATF4 undergoes numerous post-translational modifications that regulate its stability and function:

• PTM landscape:

  • Systematic reviews have identified 33 distinct PTMs on ATF4

  • Focus on phosphorylation, ubiquitination, and neddylation as key regulatory modifications

• Analytical approaches:

  • Use phospho-specific antibodies (e.g., anti-pSer219-ATF4) for detecting specific phosphorylation sites

  • Apply mass spectrometry for comprehensive PTM profiling

  • Conduct site-directed mutagenesis of key residues to determine functional significance

• Functional correlations:

  • Correlate Ser-219 phosphorylation with subsequent degradation during synaptic plasticity

  • Examine how PTMs affect dimerization partnerships and DNA binding specificity

  • Investigate PTM changes under different stress conditions (ER stress, amino acid deprivation)

The phosphorylation of ATF4 on Ser-219 creates a recognition site for SCF ubiquitin ligases, particularly in the context of a DSGXXXS motif (amino acids 218-224), marking the protein for degradation via the ubiquitin-proteasome pathway .

How can I optimize ChIP-seq experiments with ATF4 antibodies to identify genome-wide binding profiles?

ChIP-seq with ATF4 antibodies requires careful optimization:

• Technical considerations:

  • Control cross-linking time carefully (10 minutes with 1% formaldehyde is recommended to reduce non-specific binding)

  • Use stress induction (e.g., bortezomib for ER stress) to increase ATF4 levels for better signal-to-noise ratio

  • Consider multiple antibodies targeting different epitopes to validate findings

• Data analysis approaches:

  • Perform de novo motif analysis to identify enriched binding motifs

  • Compare peak sets between different conditions to identify condition-specific binding

  • Use Jaccard statistics to measure binding profile similarity with other transcription factors

• Validation strategies:

  • Validate key binding sites with conventional ChIP-qPCR

  • Combine ChIP-seq with RNA-seq to correlate binding with gene expression changes

  • Use reporter assays to confirm functionality of identified binding sites

Research has shown that the strongest ATF4 ChIP-seq peaks tend to be conserved across different conditions, with the preferred binding motif remaining largely unchanged despite treatment-induced changes in protein abundance .

How can I resolve discrepancies in ATF4 target gene identification across different studies?

Resolving discrepancies in ATF4 target gene identification requires systematic approaches:

• Critical assessment of methodologies:

  • Compare ChIP protocols: crosslinking conditions can significantly impact results

  • Evaluate antibody specificity: use multiple validated antibodies

  • Consider cellular context: different cell types may show different target gene profiles

• Integrative analysis approaches:

  • Combine ChIP-seq with RNA-seq or transcriptome microarray data

  • Apply stringent criteria requiring both ATF4 occupancy and ATF4-dependent differential expression

  • Consider the role of ATF4 heterodimers with different partners (e.g., CEBPG-ATF4 heterodimers)

• Resolution strategies:

  • Focus on consistently identified targets across multiple studies

  • Apply functional classification to identify pathway-specific regulation

  • Consider the possibility that ATF4 regulates different gene sets in different contexts

Research has highlighted significant variation in identified ATF4 binding sites, with one study finding 87,725 genome-wide binding sites corresponding to 16,164 genes, while others identified much smaller target sets . The discrepancy may relate to methodology differences and the context-specific nature of ATF4 function.