set8 Antibody

What is SET8 and why is it important in epigenetic research?

SET8 (also known as PR-SET7, SETD8, KMT5A) is a SET domain-containing histone methyltransferase that specifically monomethylates histone H4 at Lysine 20 (H4K20me1) . This 393-amino acid protein functions primarily in euchromatic regions, playing critical roles in gene silencing, cell cycle progression, and DNA damage repair . SET8 knockout studies have demonstrated that this enzyme is essential for proper chromosome condensation during interphase and chromosome segregation during mitosis . Its significance in epigenetic research stems from its unique ability to establish H4K20 monomethylation marks, which are enriched during mitosis and associated with transcriptional repression .

How do I select the appropriate SET8 antibody for my specific application?

When selecting a SET8 antibody, consider these key factors for optimal experimental outcomes:

• Validated applications: Verify the antibody has been validated for your intended application (Western blot, immunofluorescence, etc.)

• Species reactivity: Commercial SET8 antibodies show varied cross-reactivity with human, mouse, rat, and monkey SET8 proteins

• Epitope location: Some antibodies target the N-terminal region (like the Active Motif pAb) , while others may target different regions

• Sensitivity: Check published sensitivity data (many can detect endogenous levels)

• Specificity: Review supporting data showing specificity for SET8 versus other methyltransferases

The table above represents typical working dilutions for SET8 antibodies in common applications .

What is the optimal protocol for detecting SET8 by Western blot?

For optimal SET8 detection by Western blot, follow this research-validated protocol:

• Sample preparation: Extract total protein or fractionate cellular components (nuclear extracts are often preferred as SET8 is nuclear)

• Protein resolution: Use 10-12% SDS-PAGE gels for optimal separation near the 43 kDa range where SET8 migrates

• Transfer: Transfer to PVDF or nitrocellulose membranes using standard methods

• Blocking: Block membranes in 5% non-fat milk or BSA in TBST for 1 hour at room temperature

• Primary antibody: Incubate with anti-SET8 antibody at 1:1000 dilution overnight at 4°C

• Secondary antibody: Use appropriate HRP-conjugated secondary antibody (typically anti-rabbit IgG)

• Detection: Develop using ECL reagents

• Controls: Include positive controls and consider using SET8 knockout/knockdown samples as negative controls

For enhanced detection of poly ADP-ribosylated SET8 forms, consider treating cells with MG132 prior to lysis to reduce protein degradation . This will help visualize the higher molecular weight smears representative of modified SET8.

How can I optimize immunoprecipitation of SET8 for studying its post-translational modifications?

To optimize SET8 immunoprecipitation for studying post-translational modifications:

• Cell preparation: Crosslink cells with 1% formaldehyde for 10 minutes to preserve protein-protein interactions

• Lysis conditions: Use TD buffer (50 mM HEPES, pH 7.5, 250 mM NaCl, and 1% Triton X-100) supplemented with protease inhibitors

• Antibody selection: Use validated antibodies like Cell Signaling Technology #2996 or Santa Cruz Biotechnology #sc-515433

• Immunoprecipitation: Incubate 200 μg of total cell extract with 5 μg of anti-SET8 antibody overnight with end-over-end mixing at 4°C

• Protein capture: Add 50 μl of protein G magnetic beads and incubate for 1-2 hours

• Washing: Perform stringent washes to remove non-specific interactions

• Elution: Elute proteins under denaturing conditions

• Analysis: Probe Western blots with antibodies against specific modifications (e.g., anti-ADPribose antibody for poly ADP-ribosylation)

For cell cycle-specific studies, synchronize cells in G1, S, or G2/M phases before immunoprecipitation to analyze cell cycle-dependent modifications of SET8 .

Why do I observe multiple bands or high molecular weight smears when detecting SET8 by Western blot?

The observation of multiple bands or high molecular weight smears when detecting SET8 by Western blot is often due to post-translational modifications rather than non-specific binding. Research has demonstrated that SET8 undergoes extensive modification:

• Poly ADP-ribosylation: PARP1 poly ADP-ribosylates SET8 on lysine residues, resulting in high molecular weight species

• Ubiquitination: SET8 is ubiquitinated, contributing to additional higher molecular weight forms

• Cell cycle dependency: The extent of these modifications varies throughout the cell cycle, with increased levels observed during S phase

To confirm these are modified forms of SET8:

• Use MG132 (proteasome inhibitor) treatment to stabilize modified forms

• Perform immunoprecipitation followed by Western blotting with antibodies against specific modifications

• Compare band patterns across synchronized cell populations

Research by Dutta et al. demonstrated that immunoprecipitated samples display strong high molecular weight smears of SET8, with approximately 40% more signal intensity observed in the presence of MG132 .

How can I validate the specificity of my SET8 antibody?

To validate the specificity of your SET8 antibody, implement these research-grade validation approaches:

• Genetic validation:

  • Use SET8 knockdown (siRNA/shRNA) or knockout (CRISPR-Cas9) samples as negative controls

  • Perform rescue experiments by re-expressing SET8 in knockout backgrounds

• Peptide competition:

  • Pre-incubate the antibody with immunizing peptide before application

  • Signal should be significantly reduced or eliminated if antibody is specific

• Recombinant protein analysis:

  • Test reactivity against purified recombinant SET8 protein

  • Include related methyltransferases as negative controls

• Multiple antibody confirmation:

  • Compare signal patterns using antibodies targeting different SET8 epitopes

  • Use antibodies from different vendors (e.g., Cell Signaling Technology #2996, ABCAM #ab3798, Santa Cruz Biotechnology #sc-515433)

• Cell cycle analysis:

  • SET8 protein levels fluctuate during the cell cycle, peaking at G2/M

  • Validate antibody by confirming expected cell cycle-dependent expression patterns

How does poly ADP-ribosylation affect SET8 function and histone H4K20 methylation patterns?

Poly ADP-ribosylation significantly impacts SET8 function and consequent H4K20 methylation patterns through multiple mechanisms:

• Enzymatic activity modulation: Poly ADP-ribosylation by PARP1 reduces SET8's catalytic activity toward histone H4K20

• DNA/nucleosome binding disruption: SET8 binds to double-stranded DNA (Kd values of 1.6 +/− 0.6 μM) and nucleosomes through amino acids 157-175 . Poly ADP-ribosylation disrupts this interaction, preventing SET8 from accessing its substrate.

• Cell cycle-dependent regulation: The PARP1/SET8 interaction ratio is highest during S phase compared to G2/M , aligning with the pattern of ADP-ribosylated SET8. This suggests cell cycle-dependent regulation of SET8 activity through PARP1-mediated modification.

• Protein stability impact: Poly ADP-ribosylation affects SET8 stability and degradation, with studies showing ~40% higher SET8 levels in cells treated with MG132 (proteasome inhibitor) .

• Cross-communication with other modifications: Evidence suggests poly ADP-ribosylation and ubiquitination of SET8 work in concert to maintain appropriate SET8 levels in cells .

Researchers investigating this mechanism should consider monitoring both total SET8 levels and their post-translational modifications across different cell cycle stages to fully understand the regulatory dynamics.

What are the best approaches for studying SET8 interactions with chromatin and other nuclear proteins?

For studying SET8 interactions with chromatin and nuclear proteins, employ these advanced methodologies:

• Chromatin fractionation:

  • Separate chromatin-bound from soluble nuclear proteins using CSK buffer (10 mM PIPES pH 6.8, 100 mM NaCl, 300 mM sucrose, 3 mM MgCl2, and 0.5% Triton X-100)

  • Analyze SET8 distribution between fractions by Western blot

• Co-immunoprecipitation for protein interactions:

  • Use crosslinking with 1% formaldehyde (10 minutes) to preserve weak or transient interactions

  • Perform reciprocal co-IPs targeting both SET8 and suspected interaction partners

  • Published studies have successfully co-immunoprecipitated PARP1 with SET8 using this approach

• ChIP-seq for genome-wide binding:

  • Use validated ChIP-grade SET8 antibodies to map genomic binding sites

  • Correlate with H4K20me1 distribution and other epigenetic marks

• Proximity ligation assays:

  • Visualize interactions between SET8 and partner proteins in situ

  • Particularly useful for studying cell cycle-dependent interactions

• DNA binding assays:

  • Employ gel shift assays using purified SET8 protein with fluorescent-labeled double-stranded DNA

  • Research has established Kd values of 1.6 +/− 0.6 μM for SET8-DNA interactions

These approaches should be combined for a comprehensive understanding of SET8's role in chromatin biology.

How can I use SET8 antibodies to investigate cell cycle-dependent H4K20 methylation dynamics?

To investigate cell cycle-dependent H4K20 methylation dynamics using SET8 antibodies:

• Cell synchronization strategies:

  • Use double thymidine block for G1/S boundary

  • Nocodazole treatment for G2/M enrichment

  • Release from synchronization and collect time points spanning the cell cycle

• Multi-parameter analysis:

  • Combine flow cytometry for cell cycle staging with immunostaining for SET8 and H4K20me1

  • Correlate SET8 protein levels, modification status, and H4K20me1 abundance

• Chromatin immunoprecipitation (ChIP):

  • Perform ChIP-seq for SET8 and H4K20me1/2/3 across synchronized cell populations

  • Analyze locus-specific changes in SET8 binding and methylation states

• Sequential immunoprecipitation:

  • First IP with cell cycle marker antibodies

  • Second IP with SET8 or H4K20me1 antibodies

  • Reveals cell cycle stage-specific SET8 complexes

• Quantitative image analysis:

  • Immunofluorescence staining of synchronized cells

  • Measure SET8 and H4K20me1 nuclear intensity across cell cycle phases

Research has established that SET8 levels and H4K20me1 increase during S phase and peak at G2/M phase . The ratio of PARP1/SET8 interaction is highest during S phase and lowest in G2/M, mirroring the pattern of ADP-ribosylated SET8 .

How can SET8 antibodies be used to investigate the role of SET8 in DNA damage response pathways?

For investigating SET8's role in DNA damage response pathways:

• Damage-induced dynamics:

  • Monitor SET8 levels before and after DNA damage induction (e.g., UV irradiation, radiomimetic drugs)

  • Research has shown SET8 expression levels decrease in response to DNA damage, enabling p53 activation of checkpoints and/or apoptosis

• Multi-antibody approach:

  • Combine SET8 antibodies with antibodies against DNA damage markers (γH2AX, 53BP1)

  • Correlate SET8 localization with damage sites by immunofluorescence

• p53 methylation analysis:

  • SET8 methylates p53 on Lys382, down-regulating its pro-apoptotic and checkpoint activation functions

  • Use antibodies against p53-K382me1 alongside SET8 antibodies

• ChIP-sequencing at damage sites:

  • Perform ChIP-seq for SET8 and H4K20me1 before and after damage induction

  • Map SET8 recruitment to DNA break sites

• Chromatin fractionation analysis:

  • Assess redistribution of SET8 between soluble and chromatin-bound fractions following damage

  • Correlate with changes in H4K20 methylation status

• Genetic perturbation studies:

  • Use SET8 inhibition (shRNA or siRNA) to confirm its role in DNA repair

  • Research has shown SET8 inhibition results in replication fork arrest, double-stranded DNA breaks, and Chk1-mediated cell cycle arrest

What methodological considerations are important when studying SET8 post-translational modifications by mass spectrometry?

When studying SET8 post-translational modifications by mass spectrometry, consider these critical methodological factors:

• Sample preparation optimization:

  • Scale up immunoprecipitation to obtain sufficient protein for MS analysis

  • Treat cells with MG132 to stabilize modified forms of SET8

  • Consider crosslinking to preserve transient modifications

• Enrichment strategies for specific modifications:

  • For poly ADP-ribosylation: Use anti-ADPribose antibody (Cell Signaling Technology #83732S)

  • For ubiquitination: Use tandem ubiquitin binding entities (TUBEs) or anti-ubiquitin antibodies

• Peptide digestion considerations:

  • Use multiple proteases (not just trypsin) to generate overlapping peptides

  • Some modifications may affect protease efficiency

• Mass spectrometry approach:

  • Employ electron transfer dissociation (ETD) or electron capture dissociation (ECD) for labile modifications

  • Consider top-down MS approaches for intact protein analysis

• Quantitative analysis:

  • Use SILAC or TMT labeling to quantify modification changes across conditions

  • Compare modification levels across cell cycle phases

• Validation of MS findings:

  • Confirm key modifications using site-specific antibodies or mutation studies

  • Research has identified specific lysine residues that are targets for PARP1-mediated poly ADP-ribosylation