Phospho-Histone H2A.X (Thr120) Antibody

What is Histone H2A.X and how does phosphorylation at Thr120 differ from other modification sites?

Histone H2A.X is a member of the histone H2A family, one of the four core histones that form the nucleosome core particle. Unlike the well-studied phosphorylation at Ser139 (γH2AX) which is primarily associated with DNA double-strand breaks (DSBs), phosphorylation at Thr120 plays distinct roles in chromatin regulation and cellular processes. Thr120 phosphorylation has been implicated in mitotic regulation and chromosome segregation, whereas Ser139 phosphorylation is predominantly involved in DNA damage response pathways .

What is the biological significance of H2A.X Thr120 phosphorylation?

The phosphorylation of H2A.X at Thr120 is involved in several critical cellular processes. Unlike Ser139 phosphorylation which primarily functions as a DNA damage marker, Thr120 phosphorylation plays roles in:

• Regulating chromatin structure during cell cycle progression

• Mediating protein interactions at the chromatin level

• Contributing to mitotic processes and chromosome segregation

• Potentially interacting with other histone modifications to create specific chromatin states

Which kinases are responsible for phosphorylating H2A.X at Thr120?

While ATM, ATR, and DNA-PK are known to phosphorylate H2A.X at Ser139 in response to DNA damage, different kinases target Thr120. Research indicates that mitotic kinases including Aurora B may be involved in Thr120 phosphorylation, particularly during mitosis. This phosphorylation event appears to be regulated by cell cycle-dependent processes rather than exclusively by DNA damage signaling pathways .

What are the validated applications for Phospho-Histone H2A.X (Thr120) antibodies?

According to the technical specifications, Phospho-Histone H2A.X (Thr120) antibodies have been validated for:

• Western Blotting (WB): Typically at dilutions of 1:1000-2000 or 1:2,500-1:10,000, depending on the antibody source

• Some antibodies may also be validated for immunocytochemistry/immunofluorescence (ICC/IF) applications

Different manufacturers may have additional validated applications, so researchers should consult specific product documentation for the particular antibody they are using .

How should samples be prepared for optimal detection of H2A.X Thr120 phosphorylation?

For optimal detection of phosphorylated H2A.X at Thr120:

• Cell/tissue lysis preparation:

  • Use phosphatase inhibitors in lysis buffers to prevent dephosphorylation

  • Consider chromatin-bound nuclear lysates for enrichment of histone fractions

  • For Western blotting, acid extraction methods for histones may improve signal

• Fixation protocols:

  • For ICC/IF applications, paraformaldehyde (4%) fixation followed by permeabilization

  • For tissue sections, heat-induced epitope retrieval methods may be necessary

• Blocking conditions:

  • 5% BSA is generally recommended over milk-based blocking solutions as milk contains phosphatases that may reduce signal

What controls should be included when working with Phospho-Histone H2A.X (Thr120) antibodies?

Robust experimental design should include the following controls:

• Positive controls:

  • Cell lines known to exhibit Thr120 phosphorylation (e.g., mitotic cells)

  • Cells treated with phosphatase inhibitors to increase phosphorylation levels

• Negative controls:

  • Lambda phosphatase-treated samples to remove phosphorylation

  • Blocking peptide competition assays to confirm specificity

  • Isotype control antibodies

• Comparative controls:

  • Parallel detection with total H2A.X antibody to normalize phosphorylation levels

  • Analysis of synchronized cell populations to account for cell cycle-dependent phosphorylation

How can I distinguish between specific Thr120 phosphorylation and background signal?

To ensure specificity and reduce background when using Phospho-Histone H2A.X (Thr120) antibodies:

• Antibody validation approaches:

  • Peptide competition assays using the specific phosphopeptide immunogen

  • Comparison with phosphatase-treated samples

  • Dual staining with total H2A.X antibodies to confirm localization patterns

• Signal optimization strategies:

  • Titrate antibody concentrations carefully (1:1000-10,000 dilution range)

  • Increase washing steps with appropriate buffers to reduce non-specific binding

  • Use highly specific secondary antibodies with minimal cross-reactivity

Why might I observe different banding patterns in Western blots using Phospho-Histone H2A.X (Thr120) antibodies?

Different banding patterns could result from:

• Post-translational modification combinations:

  • H2A.X may carry multiple modifications simultaneously (phosphorylation, ubiquitination, acetylation)

  • These combinations can alter mobility in SDS-PAGE

• Proteolytic processing:

  • Histone tail cleavage during sample preparation

  • Endogenous proteases activated during cell death processes

• Technical factors:

  • Cross-reactivity with other histone variants

  • Sample preparation differences (use of denaturing agents, reducing conditions)

The expected molecular weight for H2A.X is approximately 15-20 kDa, but modified forms may migrate differently .

How can I quantify Phospho-Histone H2A.X (Thr120) levels reliably?

For accurate quantification:

• Normalization strategies:

  • Normalize phospho-H2A.X (Thr120) to total H2A.X levels

  • Use loading controls appropriate for nuclear/chromatin proteins (e.g., histone H3)

• Quantification methods:

  • For Western blot: densitometry with linear range validation

  • For immunofluorescence: integrated intensity measurements with background subtraction

  • For flow cytometry: mean fluorescence intensity comparisons

• Statistical considerations:

  • Multiple biological replicates (minimum n=3)

  • Appropriate statistical tests based on data distribution

  • Account for cell cycle variations in asynchronous populations

How does H2A.X Thr120 phosphorylation differ functionally from the well-characterized Ser139 phosphorylation (γH2AX)?

While both are phosphorylation events on H2A.X, they serve distinct functions:

These functional differences highlight the diverse roles of H2A.X modifications in maintaining genomic integrity .

Can Phospho-Histone H2A.X (Thr120) antibodies be used for ChIP or ChIP-seq applications?

While not explicitly validated in the provided search results, researchers interested in ChIP applications should consider:

• Protocol adaptations:

  • Cross-linking optimization (1-2% formaldehyde for 10-15 minutes)

  • Sonication conditions that preserve phospho-epitopes

  • Buffer modifications to maintain phosphorylation status

• Quality control approaches:

  • qPCR validation of enrichment at known target loci before sequencing

  • IgG and input controls to assess background

  • Parallel ChIP with total H2A.X antibodies for normalization

• Data analysis considerations:

  • Peak calling algorithms suitable for histone modifications

  • Integration with other genomic datasets to identify functional associations

  • Comparison with publicly available H2A.X ChIP-seq datasets

How can Phospho-Histone H2A.X (Thr120) antibodies be used to investigate cross-talk between different histone modifications?

Advanced experimental approaches include:

• Sequential ChIP (Re-ChIP):

  • First immunoprecipitation with Phospho-H2A.X (Thr120) antibody

  • Second immunoprecipitation with antibodies against other modifications

  • Analysis of co-occurrence at specific genomic loci

• Mass spectrometry-based approaches:

  • Immunoprecipitation followed by MS analysis

  • Identification of co-occurring modifications on the same histone tail

  • Quantitative assessment of modification stoichiometry

• Proximity ligation assays:

  • In situ detection of closely associated histone modifications

  • Visualization of modification cross-talk in different nuclear compartments

  • Quantification of interaction frequencies under different conditions

What experimental approaches can determine the precise timing of H2A.X Thr120 phosphorylation during cell cycle progression?

Researchers can employ the following methods:

• Synchronized cell population analysis:

  • Cell synchronization using thymidine block, nocodazole, or serum starvation

  • Collection of samples at defined timepoints following release

  • Western blot or flow cytometry analysis of Thr120 phosphorylation levels

• Live-cell imaging approaches:

  • FRET-based biosensors for real-time phosphorylation detection

  • Correlation with cell cycle markers (e.g., PCNA, cyclin levels)

  • Single-cell analysis to account for population heterogeneity

• Combinatorial flow cytometry:

  • Co-staining for Phospho-H2A.X (Thr120) and DNA content (PI, DAPI)

  • Additional cell cycle markers (e.g., phospho-H3)

  • Multiparameter analysis to correlate phosphorylation with precise cell cycle phases

How can Phospho-Histone H2A.X (Thr120) antibodies be used to investigate the relationship between mitotic regulation and DNA damage?

Research approaches include:

• Dual-staining protocols:

  • Co-staining for Phospho-H2A.X (Thr120) and Phospho-H2A.X (Ser139/γH2AX)

  • Analysis of spatial and temporal distribution patterns

  • Correlation with cell cycle markers and DNA damage foci

• Experimental induction designs:

  • Mitotic arrest using microtubule inhibitors (nocodazole, taxol)

  • DNA damage induction (etoposide, camptothecin, radiation)

  • Time-course analysis of different H2A.X phosphorylation events

• Quantitative analysis:

  • Ratio measurements of different phosphorylation forms

  • Correlation with known DNA damage markers

  • Assessment of phosphorylation dynamics during DNA damage recovery

What is the relationship between H2A.X Thr120 phosphorylation and cancer research?

Phospho-Histone H2A.X (Thr120) detection has relevance in cancer research:

• Diagnostic/prognostic potential:

  • Analysis of phosphorylation patterns in tumor samples

  • Correlation with mitotic index and genomic instability

  • Potential biomarker for treatment response

• Drug discovery applications:

  • Screening compounds that modulate Thr120 phosphorylation

  • Evaluation of mitotic kinase inhibitors

  • Assessment of mitotic checkpoint targeting therapies

• Cancer cell biology insights:

  • Understanding aberrant mitotic progression in cancer cells

  • Investigation of chromosome segregation defects

  • Correlation with aneuploidy and chromosomal instability

How do various anti-neoplastic agents affect the phosphorylation status of H2A.X at Thr120 compared to Ser139?

Different classes of anti-cancer drugs may differentially impact H2A.X phosphorylation sites:

Comparing these effects experimentally requires careful time-course analysis and quantification methods .

What factors should be considered when using Phospho-Histone H2A.X (Thr120) antibodies for flow cytometry?

For flow cytometry applications:

• Sample preparation considerations:

  • Gentle fixation protocols to preserve nuclear integrity (2-4% paraformaldehyde)

  • Permeabilization optimization (methanol vs. detergent-based methods)

  • Buffer composition to maintain phospho-epitopes (phosphatase inhibitors)

• Staining protocol parameters:

  • Antibody dilution (typically 1:50-1:200 for flow applications)

  • Incubation conditions (temperature, time, agitation)

  • Washing steps to reduce background

• Analytical considerations:

  • Appropriate controls (unstained, secondary-only, isotype, positive/negative)

  • Co-staining with DNA content dyes for cell cycle correlation

  • Gating strategies to identify specific cell populations

How can I design multiplexed immunofluorescence experiments using Phospho-Histone H2A.X (Thr120) antibodies?

For successful multiplexed detection:

• Antibody compatibility planning:

  • Host species considerations to avoid cross-reactivity

  • Sequential staining protocols for antibodies from the same species

  • Selection of non-overlapping fluorophores with appropriate spectral separation

• Optimized staining sequence:

  • Begin with lowest abundance target (often phospho-epitopes)

  • Include blocking steps between primary antibodies when necessary

  • Consider tyramide signal amplification for low-abundance phospho-epitopes

• Image acquisition and analysis strategies:

  • Sequential scanning to minimize bleed-through

  • Proper controls for spectral unmixing

  • Colocalization analysis workflows to assess spatial relationships

What considerations are important when comparing results from different Phospho-Histone H2A.X (Thr120) antibody clones or sources?

When using antibodies from different sources:

• Epitope recognition differences:

  • Examine the exact immunogen sequence used (e.g., peptide sequence around phosphorylation site of threonine 120 K-K-T(p)-S-A)

  • Consider whether flanking modifications might affect recognition

  • Review validation data showing specificity for the phospho-epitope

• Technical validation comparisons:

  • Side-by-side testing with identical samples

  • Assessment of signal-to-noise ratios

  • Determination of optimal working concentrations for each antibody

• Cross-platform standardization:

  • Use of common positive controls across experiments

  • Normalization strategies when comparing datasets

  • Documentation of exact clone/lot information in publications