MRE11 Antibody

What is MRE11 and why is it important in cellular research?

MRE11 (Meiotic Recombination 11) is a central component of the MRN complex, which includes MRE11, RAD50, and NBS1 proteins. This complex plays a critical role in sensing, processing, and repairing DNA double-strand breaks. Defects in MRE11 function lead to genomic instability, telomere shortening, aberrant meiosis, and hypersensitivity to DNA damage . The MRN complex also initiates DNA damage signaling through the activation of the ATM kinase, which serves as a master controller of cellular responses to DSBs . The study of MRE11 is particularly important because hypomorphic mutations in this protein are found in ataxia-telangiectasia-like disease (ATLD), with phenotypes similar to mutations in ATM that cause ataxia-telangiectasia (A-T), including a predisposition to malignancy in humans .

What are the primary applications for MRE11 antibodies in research?

MRE11 antibodies are versatile tools in DNA repair research with multiple validated applications:

These applications enable researchers to investigate MRE11 expression, localization, and interactions in various experimental contexts . For efficient experimental design, it's crucial to verify species cross-reactivity, as many commercially available antibodies react with human, mouse, rat, and monkey MRE11, while some have broader reactivity profiles including dog, rabbit, yeast, guinea pig, cow, horse, and zebrafish .

How should MRE11 antibodies be validated before experimental use?

Proper validation of MRE11 antibodies is essential for reliable experimental results. A comprehensive validation approach should include:

• Specificity verification through Western blotting with positive controls (cell lines known to express MRE11) and negative controls (MRE11-knockout or knockdown cells)

• Cross-reactivity testing if working with non-human models, as antibody affinity may vary between species

• Functional validation through immunofluorescence to confirm nuclear localization and focus formation after DNA damage induction

• Blocking peptide competition assays to confirm the specificity of the antibody for its target epitope

• Comparison of results using different antibodies targeting different regions of MRE11

The validation should confirm detection of the expected 81 kDa band in Western blotting applications and proper nuclear localization in immunocytochemistry or immunohistochemistry . For advanced applications like chromatin immunoprecipitation or proximity ligation assays, additional validation steps may be necessary to ensure antibody performance in these specific contexts.

How can MRE11 antibodies be utilized to study DNA damage response dynamics?

MRE11 antibodies can be instrumental in visualizing and quantifying the recruitment of MRE11 to sites of DNA damage. After DNA damage induction (e.g., by ionizing radiation, radiomimetic drugs, or targeted nucleases), MRE11 forms discrete nuclear foci that can be detected by immunofluorescence microscopy.

A methodological approach for studying this dynamics includes:

• Treat cells with DNA-damaging agents (e.g., 2-10 Gy ionizing radiation or 50-500 ng/ml neocarzinostatin)

• Fix cells at various time points post-treatment (typically 15 min to 24 hours)

• Perform immunofluorescence with anti-MRE11 antibodies (typically at 1:200-1:500 dilution)

• Co-stain with γ-H2AX and 53BP1 antibodies as markers of DNA damage sites

• Quantify MRE11 foci formation, intensity, and co-localization with other repair factors

Research has shown that inhibition of arginine methylation decreases MRE11 focus formation at double-strand breaks in vivo . When designing such experiments, it's important to consider that the glycine-arginine-rich (GAR) domain of MRE11 is sufficient to localize the protein to nuclear foci after DNA damage, suggesting this domain plays a critical role in the recruitment process .

What approaches can be used to study MRE11's interaction with other MRN complex components?

Investigating MRE11's interactions with RAD50 and NBS1 is crucial for understanding MRN complex functionality. Several methodological approaches can be employed:

• Co-immunoprecipitation (Co-IP):

  • Prepare cell lysates in non-denaturing conditions

  • Immunoprecipitate with anti-MRE11 antibody (typically 1:100 dilution)

  • Analyze precipitates by Western blotting for RAD50 and NBS1

  • Include appropriate controls such as IgG control and input samples

• Proximity Ligation Assay (PLA):

  • Fix cells on coverslips

  • Incubate with primary antibodies against MRE11 and its binding partners

  • Apply PLA probes and perform ligation and amplification

  • Visualize interaction signals using fluorescence microscopy

• Sequential Immunoprecipitation:

  • Perform first IP with anti-MRE11 antibody

  • Elute under mild conditions

  • Perform second IP with anti-RAD50 or anti-NBS1

  • Analyze to confirm intact complex formation

Research has shown that PRMT1 (protein arginine methyltransferase 1) interacts with MRE11 alone but not with the complete MRN complex, suggesting that MRE11 arginine methylation occurs prior to its incorporation into the MRN complex . When designing interaction studies, it's important to note that the strength of these interactions can vary, with some being resistant to high salt concentrations (up to 750 mM NaCl) .

How can methylation status of MRE11 be assessed using specialized antibodies?

MRE11 contains a glycine-arginine-rich (GAR) motif that undergoes methylation, which regulates its function. To study this modification:

• Methylation-specific antibodies:

  • Use antibodies specifically recognizing methylated MRE11 (anti-MeMRE11)

  • Verify specificity using unmethylated controls (e.g., MRE11 with arginine to alanine mutations)

  • Apply in Western blotting (typically 1:500-1:1000) or immunoprecipitation (1:50-1:100)

• Methylation inhibition experiments:

  • Treat cells with methyltransferase inhibitors (e.g., MTA/ADOX)

  • Compare methylation status and protein-protein interactions before and after treatment

  • Assess functional consequences on DNA repair capacity

• Mass spectrometry analysis:

  • Immunoprecipitate MRE11 using specific antibodies

  • Digest protein and analyze peptides by mass spectrometry

  • Identify methylated residues and quantify methylation levels

Research has demonstrated that the first six methylated arginines in the GAR domain are essential for regulating MRE11 DNA binding and nuclease activity . When designing methylation studies, consider that inhibition of arginine methylation can disrupt the interaction between MRE11 and PRMT1, as shown in experiments where methyltransferase inhibitors abrogated this interaction .

What are common issues in visualizing MRE11 foci formation and how can they be resolved?

Detecting MRE11 foci formation after DNA damage can be challenging due to several factors:

It's important to note that the GAR domain of MRE11 is sufficient for localization to nuclear foci after DNA damage . Therefore, when troubleshooting foci formation issues, consider using positive controls that specifically target this domain. Additionally, remember that inhibition of arginine methylation can significantly reduce MRE11 focus formation at double-strand breaks in vivo , which may be a confounding factor in some experimental contexts.

How can specificity issues in MRE11 antibody applications be addressed?

Ensuring antibody specificity is crucial for reliable MRE11 research:

• Validation strategies for suspected cross-reactivity:

  • Perform Western blotting on lysates from multiple species

  • Include MRE11 knockout/knockdown samples as negative controls

  • Test multiple antibodies targeting different MRE11 epitopes

  • Consider peptide competition assays to confirm specificity

• Optimization approaches for high background:

  • Titrate primary antibody concentration

  • Extend blocking step duration (1-2 hours at room temperature)

  • Use casein-based blockers instead of traditional BSA/serum

  • Increase wash steps duration and frequency

  • Consider using monoclonal antibodies if polyclonal antibodies show high background

• Addressing nuclear vs. cytoplasmic staining discrepancies:

  • Verify nuclear localization with subcellular fractionation followed by Western blotting

  • Optimize fixation conditions (paraformaldehyde concentration and time)

  • Co-stain with known nuclear markers

  • Compare patterns with multiple anti-MRE11 antibodies

When troubleshooting specificity issues, it's worth noting that different antibodies may preferentially recognize specific forms of MRE11, such as those with particular post-translational modifications. For instance, methylation-specific antibodies have been developed that specifically recognize the methylated GAR domain of MRE11 .

How do MRE11 antibodies help elucidate its nuclease activities in different experimental contexts?

MRE11 possesses multiple nuclease activities that can be studied using specialized approaches with MRE11 antibodies:

• In vitro nuclease assay with immunoprecipitated MRE11:

  • Immunoprecipitate MRE11 from cell extracts using specific antibodies

  • Incubate with labeled DNA substrates (e.g., 5' overhangs, 3' flaps, hairpins)

  • Analyze reaction products to assess exonuclease and endonuclease activities

  • Compare activities of wild-type vs. mutant MRE11 proteins

• Chromatin immunoprecipitation (ChIP) at induced DSB sites:

  • Create site-specific DSBs using nucleases (e.g., I-SceI, CRISPR/Cas9)

  • Perform ChIP using anti-MRE11 antibodies

  • Analyze DNA processing at break sites by sequencing or qPCR

  • Compare with nuclease-dead MRE11 mutants

• Proximity ligation assay (PLA) for MRE11-DNA interactions:

  • Fix cells after DNA damage

  • Use anti-MRE11 antibody and anti-BrdU antibody (after ssDNA exposure)

  • Perform PLA to visualize MRE11 association with processed DNA

Research has shown that MRE11 has 3'-to-5' exonuclease activity and endonuclease activity on various DNA substrates, including 5' overhangs, 3' flaps, 3' branches, and closed hairpins . These activities are critical for processing DNA ends during repair. When designing nuclease activity experiments, it's important to consider that MRE11 functions as a dimer that can bind both sides of a DSB , and this dimerization is important for its activity.

What is the significance of MRE11 post-translational modifications and how can they be studied?

Post-translational modifications (PTMs) of MRE11, particularly arginine methylation, play crucial roles in regulating its function:

• Detecting MRE11 methylation:

  • Use methylation-specific antibodies in Western blotting or immunoprecipitation

  • Compare signal before and after treatment with methylation inhibitors

  • Analyze methylation in different cellular contexts (e.g., before/after DNA damage)

• Studying the functional impact of MRE11 methylation:

  • Generate methylation-deficient mutants (arginine to lysine or alanine substitutions)

  • Compare DNA binding, nuclease activity, and protein interactions

  • Assess cellular phenotypes (e.g., DNA repair efficiency, cell survival)

• Identifying enzymes responsible for MRE11 PTMs:

  • Co-immunoprecipitate MRE11 and analyze associated enzymes

  • Deplete candidate enzymes (e.g., PRMT1) and assess MRE11 modification status

  • Reconstitute in vitro modification systems with purified components

Research has demonstrated that PRMT1 interacts with MRE11 but not with the complete MRN complex, suggesting that MRE11 arginine methylation occurs prior to its incorporation into the MRN complex . The first six methylated arginines in the GAR domain are particularly important for regulating MRE11's DNA binding and nuclease activity . When designing experiments to study these modifications, it's noteworthy that inhibition of arginine methylation leads to a reduction in MRE11 and RAD51 focus formation on DNA double-strand breaks in vivo , highlighting the functional importance of this modification.

How can MRE11 antibodies be used to investigate its role in ATM activation and DNA damage signaling?

MRE11 plays a crucial role in activating the ATM kinase and initiating DNA damage signaling cascades:

• Co-immunoprecipitation studies of MRE11-ATM interactions:

  • Immunoprecipitate MRE11 from cells before and after DNA damage

  • Probe for associated ATM in Western blots

  • Analyze interaction dynamics over time after damage

  • Compare wild-type and nuclease-dead MRE11 variants

• Immunofluorescence analysis of signaling activation:

  • Induce DNA damage in cells

  • Co-stain for MRE11 and activated ATM (phospho-ATM Ser1981)

  • Assess temporal relationships between MRE11 recruitment and ATM activation

  • Quantify co-localization at damage sites

• Biochemical analysis of ATM activation:

  • Immunodeplete MRE11 from cell extracts using specific antibodies

  • Assess residual ATM activation capacity in response to DNA damage

  • Reconstitute with purified MRE11 (wild-type or mutant)

  • Monitor ATM substrate phosphorylation (e.g., p-CHK2, p-SMC1)

Research has established that the MRN complex can directly activate the ATM checkpoint kinase at DNA breaks . This activation involves the conversion of inactive ATM dimers into active monomers, which then phosphorylate numerous downstream factors involved in DNA damage response . When designing such experiments, it's important to consider that cellular consequences of MRE11 dysfunction include chromosomal instability and defects in the intra-S phase and G2/M checkpoints in response to DNA damage .

What are the best approaches for studying MRE11 in heterogeneous tissue samples?

Investigating MRE11 expression and function in complex tissue samples presents unique challenges:

• Immunohistochemistry optimization strategies:

  • Test multiple antigen retrieval methods (heat-induced vs. enzymatic)

  • Optimize antibody concentration (typically starting at 1:500 dilution)

  • Include positive control tissues with known MRE11 expression

  • Use automated staining systems for consistency across samples

  • Validate specificity with blocking peptides

• Tissue-specific Western blotting considerations:

  • Select appropriate tissue lysis buffers to maintain protein integrity

  • Include protease and phosphatase inhibitors to preserve modifications

  • Consider native PAGE for complex integrity assessment

  • Use gradient gels for better separation of high molecular weight proteins

• Single-cell analysis of MRE11 in heterogeneous tissues:

  • Apply multiplexed immunofluorescence with cell type-specific markers

  • Combine with digital pathology approaches for quantitative analysis

  • Consider laser capture microdissection followed by protein analysis

  • Use CyTOF mass cytometry for high-dimensional protein profiling

When analyzing tissue samples, it's important to consider that MRE11 expression and localization may vary between cell types and under different pathological conditions. For instance, dysregulation of the MRN complex has been observed in various cancers, making careful interpretation of staining patterns essential .

How can MRE11 antibodies be used in studies of MRN complex dynamics during the cell cycle?

The MRN complex exhibits dynamic changes throughout the cell cycle, which can be studied using specialized approaches:

• Cell synchronization and time-course analysis:

  • Synchronize cells using thymidine block, nocodazole, or serum starvation

  • Collect samples at defined cell cycle stages

  • Perform Western blotting for MRE11 and other MRN components

  • Assess protein levels, modifications, and complex formation

• Immunofluorescence microscopy through the cell cycle:

  • Fix synchronized cells at different cell cycle phases

  • Co-stain for MRE11 and cell cycle markers (e.g., PCNA, phospho-histone H3)

  • Analyze changes in nuclear distribution and foci formation

  • Quantify co-localization with replication factories in S phase

• Live-cell imaging approaches:

  • Generate cell lines expressing fluorescently tagged MRE11

  • Validate construct functionality with complementary antibody staining

  • Perform time-lapse imaging throughout the cell cycle

  • Track protein dynamics in real-time after DNA damage induction

Research has shown that MRE11 plays distinct roles during different cell cycle phases, including telomere maintenance during replication and double-strand break repair throughout the cell cycle . When designing cell cycle experiments, it's noteworthy that defects in MRE11 function can lead to cell cycle checkpoint defects, particularly in the intra-S phase and G2/M transitions in response to DNA damage .

What are the most effective strategies for studying the evolutionary conservation of MRE11 function across species?

MRE11 is evolutionarily conserved from yeast to humans, providing opportunities for comparative studies:

• Cross-species antibody validation approach:

  • Test antibody reactivity against MRE11 from multiple species

  • Optimize immunoblotting conditions for each species

  • Verify epitope conservation through sequence alignment

  • Consider generating new antibodies against highly conserved regions

• Comparative functional analysis:

  • Immunoprecipitate MRE11 from different species using validated antibodies

  • Compare biochemical activities (e.g., nuclease function, DNA binding)

  • Assess protein-protein interactions and complex formation

  • Correlate functional differences with structural variations

• Complementation studies in model organisms:

  • Deplete endogenous MRE11 in model systems

  • Express MRE11 from different species

  • Use species-specific and cross-reactive antibodies to monitor expression

  • Assess functional rescue through cellular phenotypes

Research has shown that while MRE11 function is broadly conserved, there are species-specific differences. For example, the GAR motif is conserved among multicellular eukaryotic species , and methylation of MRE11 appears to be evolutionarily conserved as well, as demonstrated by studies showing MRE11 methylation in insect cells . When designing cross-species studies, it's important to consider the high sequence conservation of functional domains, which can facilitate the use of the same antibodies across multiple species .