Tri-Methyl-Histone H3 (Lys79) Antibody

What is Tri-Methyl-Histone H3 (Lys79) and what is its biological significance?

Tri-Methyl-Histone H3 (Lys79) represents a specific post-translational modification where lysine 79 on histone H3 contains three methyl groups. This modification belongs to the broader category of histone methylation, which plays crucial roles in epigenetic regulation.

Biologically, H3K79 methylation occurs primarily on histones H3 and has been implicated in both transcriptional activation and silencing . This modification coordinates the recruitment of chromatin modifying enzymes containing methyl-lysine binding modules such as:

• Chromodomains (HP1, PRC1)

• PHD fingers (BPTF, ING2)

• Tudor domains (53BP1)

• WD-40 domains (WDR5)

H3K79 trimethylation is particularly associated with active gene transcription and serves as a marker for active chromatin regions. Unlike some histone modifications, H3K79 methylation is catalyzed by the methyltransferase DOT1, and research has shown that methylation is a reversible epigenetic marker with the discovery of various histone demethylases .

What are the key differences between mono-, di-, and tri-methylation at Histone H3 Lysine 79?

The different methylation states of H3K79 have distinct functional implications in chromatin regulation:

Research indicates that each methylation state may have unique roles in gene regulation, with tri-methylation particularly showing a preference for active promoters as demonstrated in ChIP experiments with HeLaS3 cells .

What are the primary applications of Tri-Methyl-Histone H3 (Lys79) antibodies in epigenetic research?

Tri-Methyl-Histone H3 (Lys79) antibodies are versatile tools employed in multiple experimental approaches to study epigenetic regulation:

• Western Blotting (WB): For detection of the modification in protein extracts, typically at 17 kDa

• Chromatin Immunoprecipitation (ChIP): To identify genomic regions associated with this modification

• ChIP-sequencing (ChIP-seq): For genome-wide profiling of H3K79me3 distribution

• Immunohistochemistry (IHC): For tissue-specific localization studies

• Immunocytochemistry/Immunofluorescence (ICC/IF): For cellular localization analysis

• Dot Blots: For specificity testing and antibody validation

• Multiplex Immunoassays: For simultaneous detection of multiple histone modifications

For optimal ChIP and ChIP-seq results, technical specifications often recommend using 10 μl of antibody and 10 μg of chromatin (approximately 4 × 10^6 cells) per immunoprecipitation .

How do I determine the specificity of a Tri-Methyl-Histone H3 (Lys79) antibody?

Determining antibody specificity is critical for reliable experimental results. Multiple methods are employed to validate Tri-Methyl-Histone H3 (Lys79) antibody specificity:

Dot Blot Specificity Analysis:

• Use arrays containing peptides representing all key histone modification sites

• Apply antibody at recommended dilution (e.g., 1:5000)

• Visualize using appropriate secondary antibody and detection system

• Evaluate cross-reactivity with other histone modifications

Multiplex Immunoassay:

• Incubate antibody (e.g., at 0.01 mg/ml concentration) with microspheres conjugated to various histone H3 peptides:

  • Monomethyl Lys79

  • Unmethylated Lys79

  • Trimethyl Lys27

  • Trimethyl Lys9

  • Trimethyl Lys79

• Process using standard xMAP protocols

• Analyze binding patterns to confirm specificity

Western Blot Validation:

• Test with recombinant histone proteins and cell extracts (e.g., HeLa acid extracts)

• Verify molecular weight (approximately 17 kDa)

• Compare binding patterns across different cell types

A high-quality Tri-Methyl-Histone H3 (Lys79) antibody should show minimal cross-reactivity with other methylation states at Lys79 or with other methylated lysine residues on histones.

What are the optimal protocols for using Tri-Methyl-Histone H3 (Lys79) antibodies in Western Blotting?

For optimal Western Blotting results with Tri-Methyl-Histone H3 (Lys79) antibodies:

Sample Preparation:

• Use acid-extracted histones from cells or tissues

• Load approximately 10-15 μg of histone extract per lane

• Include recombinant Histone H3 as a positive control when available

Antibody Dilution and Incubation:

• Recommended dilution: 1:1000

• Incubate membrane according to manufacturer's protocol (typically overnight at 4°C)

Detection Considerations:

• Expected molecular weight: 17 kDa

• Use appropriate secondary antibody based on host species (typically rabbit IgG)

• Include controls: unmodified H3 and other methylation states when possible

Validation Evidence:
Western blot analysis at 0.1 μg/ml antibody concentration has been shown to successfully detect Histone H3 on 10 μg of HeLa acid extract lysate , confirming the sensitivity of these antibodies at appropriate dilutions.

How can I use Tri-Methyl-Histone H3 (Lys79) antibodies for effective Chromatin Immunoprecipitation (ChIP)?

Tri-Methyl-Histone H3 (Lys79) antibodies are valuable tools for ChIP experiments investigating the genomic distribution of this modification:

Optimal ChIP Protocol Parameters:

• Recommended antibody amount: 10 μl of antibody per IP

• Chromatin amount: 10 μg (approximately 4 × 10^6 cells)

• Dilution for ChIP applications: 1:50

• Validated with: SimpleChIP® Enzymatic Chromatin IP Kits

Experimental Validation Example:
ChIP analysis of sheared chromatin from 10⁶ HeLaS3 cells using antibody titrations (1, 2, 5, and 10 μg per ChIP experiment) demonstrated that:

• H3K79me3 shows preferential enrichment at active promoters

• Recovery is typically expressed as a percentage of input (the relative amount of immunoprecipitated DNA compared to input DNA after qPCR analysis)

• GAPDH promoter shows significant enrichment compared to inactive genes like myoglobin exon 2

ChIP-seq Considerations:

• Use same antibody concentration as standard ChIP (1:50)

• For library preparation, cluster generation and sequencing, follow manufacturer's instructions for your sequencing platform

• For data analysis, align tags to the reference genome using appropriate algorithms (e.g., ELAND algorithm)

• Visualize peak distribution across chromosomes to identify enriched regions

What controls should I include when working with Tri-Methyl-Histone H3 (Lys79) antibodies?

Proper experimental controls are essential for reliable interpretation of results:

Negative Controls:

• IgG from same species as the primary antibody (e.g., rabbit IgG)

• Use at same concentration as test antibody

• Non-specific binding should be minimal

Positive Controls:

• Known H3K79me3-enriched genes (e.g., GAPDH promoter for active transcription)

• Cell lines with documented H3K79me3 patterns (e.g., HeLa cells)

Specificity Controls:

• Peptide competition assays with tri-methyl-K79 peptides

• Parallel experiments with antibodies recognizing different methylation states (mono-, di-methylation)

• Include samples from DOT1L inhibitor-treated cells (should show reduced H3K79me3 signal)

Quantitative Controls:

• Input chromatin (typically 1-5% of starting material)

• Normalization genes for qPCR analysis

• Standard curves for accurate quantification

In ChIP experiments, quantitative PCR analysis comparing recovery at active genes (GAPDH) versus inactive genes (myoglobin) can serve as an internal validation of antibody specificity and experimental success .

How can I optimize ChIP-seq experiments with Tri-Methyl-Histone H3 (Lys79) antibodies?

ChIP-seq optimization requires attention to multiple experimental parameters:

Antibody Selection and Validation:

• Confirm ChIP-seq grade certification

• Verify batch-to-batch consistency through pilot experiments

• For recombinant antibodies, note the superior lot-to-lot consistency

Experimental Design Considerations:

• Optimal antibody dilution: 1:50 for ChIP-seq applications

• Library preparation: Follow manufacturer's guidelines for your sequencing platform

• Sequencing depth: Minimum 20 million reads recommended for histone modifications

• Include appropriate controls (input DNA, IgG controls)

Data Analysis Pipeline:

• Align 36 bp tags to reference genome using appropriate algorithms

• Analyze peak distribution patterns along complete chromosome sequences

• Compare H3K79me3 distribution to gene expression data

• Focus analysis on:

  • Promoter regions

  • Gene bodies

  • Enhancer elements

Validation Approach:
ChIP-seq analysis of H3K79me3 from HeLaS3 cells demonstrated clear peak distribution patterns visible at multiple genomic scales:

• Complete chromosome sequences

• 600 kb regions of specific chromosomes

• 2 Mb regions showing detailed binding patterns

• 100 kb regions surrounding specific genes like GAPDH

What are the technical considerations for multiplex assays involving Tri-Methyl-Histone H3 (Lys79) and other histone modifications?

Multiplex assays allow simultaneous measurement of multiple histone modifications, requiring specialized approaches:

Fluorescence Polarization (FP) Assay Considerations:

• FP is a homogeneous technology with no washing steps, increasing speed and precision

• Reactions reach equilibrium rapidly (seconds to minutes)

• Stable reagents prepared at one time yield high reproducibility

• Requires only one tracer with no need for fluorophore response to binding events

Critical Parameters for Multiplex Histone Modification Assays:

• Salt concentration and pH significantly affect protein-protein interactions

• Maintain consistency across experiments

• Peptide concentration should be optimized (typically 100-200 nM for instruments with 2 nM fluorescein sensitivity)

• Protein concentration ranges should span approximately 0.1 μM to 1 mM for initial studies

Instrument Calibration:

• Verify G factor determination

• Test instrument sensitivity with calibration dyes

• Determine optimal peptide concentration ranges

Assay Setup for Binding Studies:
Preparation of reaction components requires precise handling:

• Reconstitute lyophilized peptides to 20 μM stock solutions

• Create working dilutions according to experimental design

• Prepare binding buffer with consistent composition

• Perform serial dilutions of test proteins (1:2, 1:3, or 1:4 as appropriate)

How does H3K79 trimethylation distribution relate to gene expression and chromatin states?

H3K79 trimethylation has specific relationships with gene expression and chromatin architecture:

Genomic Distribution Patterns:

• H3K79me3 shows preferential enrichment at active promoters

• ChIP-seq analysis reveals specific distribution patterns along chromosomes

• Active genes (e.g., GAPDH) show significant H3K79me3 enrichment compared to inactive genes

Functional Relationships:

• H3K79 methylation has been implicated in both transcriptional activation and silencing

• Functions in coordination with other histone modifications to regulate gene expression

• Methylation of lysine residues coordinates recruitment of chromatin modifying enzymes containing methyl-lysine binding modules

Chromatin Context:

• Works in concert with other histone modifications in the "histone code"

• Forms part of the epigenetic landscape determining chromatin accessibility

• Unlike some modifications that occur primarily at promoters, H3K79me3 can be found in gene bodies

Regulatory Mechanisms:

• DOT1 is the primary methyltransferase responsible for H3K79 methylation

• The discovery of histone demethylases (PADI4, LSD1, JMJD1, JMJD2, JHDM1) has shown that this methylation is reversible

• Different methylation states (mono-, di-, tri-) may have distinct roles in transcriptional regulation

How do I troubleshoot inconsistent results when using Tri-Methyl-Histone H3 (Lys79) antibodies?

When encountering variability in experimental outcomes, consider these troubleshooting approaches:

Antibody-Related Factors:

• Check antibody specificity through dot blot analysis with peptide arrays

• Verify antibody concentration and storage conditions

• Consider lot-to-lot variability (recombinant antibodies offer superior consistency)

• Test multiple antibody dilutions to determine optimal working concentration

Sample Preparation Issues:

• Ensure proper histone extraction techniques (acid extraction is recommended)

• Verify sample integrity through total H3 detection

• Check for potential interfering modifications or epitope masking

• Consider cell type-specific differences in H3K79me3 patterns

Technical Considerations for ChIP Experiments:

• Optimize chromatin shearing/fragmentation (200-500 bp fragments ideal)

• Adjust antibody:chromatin ratio (recommended: 10 μl antibody to 10 μg chromatin)

• Increase wash stringency to reduce background

• Include appropriate controls (IgG, input chromatin)

Data Analysis Approaches:

• Normalize to appropriate references (input DNA, housekeeping genes)

• Use multiple methods for validation (WB, ChIP-qPCR, ChIP-seq)

• Compare results across multiple cell types or experimental conditions

• Consult literature for expected H3K79me3 distribution patterns in your experimental system

All protein-protein interactions are sensitive to factors including salt concentration and pH, so consistency across experiments is critical for reproducible results .