SET5 Antibody

What is SETD5 and why are antibodies against it important for research?

SETD5 is a protein containing a SET domain that has been implicated in neurodevelopmental disorders and plays a crucial role in hematopoietic stem cell (HSC) function. While SETD5 contains a SET domain typically associated with histone methyltransferase activity, its enzymatic activity remains somewhat questionable, as studies have not detected obvious changes in histone methylation patterns upon SETD5 deletion .

SETD5 antibodies are essential research tools because they enable the detection, localization, and functional analysis of this protein. Research has shown that SETD5 regulates HSC quiescence by mediating the release of promoter-proximal paused RNA polymerase II on E2F targets in cooperation with HCF-1 and PAF1 complex . Without specific antibodies, investigating these complex molecular interactions would be extremely challenging.

How are SETD5 antibodies typically validated for research applications?

SETD5 antibodies undergo multiple validation methods to ensure specificity and reliability:

• Standard validation - Based on concordance with experimental gene/protein characterization data in databases like UniProtKB/Swiss-Prot, resulting in scores of "Supported," "Approved," or "Uncertain" .

• Enhanced validation - Performed using:

  • siRNA knockdown: Evaluating decreased antibody staining upon target protein downregulation

  • Tagged GFP cell lines: Assessing signal overlap between antibody staining and GFP-tagged protein

  • Independent antibodies: Comparing staining patterns of multiple antibodies targeting different epitopes on the protein

• Application-specific validation - Including immunohistochemistry (IHC), immunocytochemistry (ICC-IF), and Western blotting (WB) .

For research reliability, antibodies that have undergone multiple validation methods, particularly enhanced validation, should be preferred as they demonstrate highest specificity for the target protein.

What are the main applications for SETD5 antibodies in basic research?

SETD5 antibodies are employed across several key research applications:

• Chromatin Immunoprecipitation (ChIP) - Used to investigate genomic binding sites of SETD5, particularly important since SETD5 has been shown to be enriched at promoter regions and gene bodies (introns and exons) .

• Immunoprecipitation (IP) - For identifying protein-protein interactions, such as the association between SETD5 and HCF-1, OGT, and components of the PAF1 complex .

• Immunoblotting/Western Blotting - To detect and quantify SETD5 protein expression levels in different tissues or under various experimental conditions .

• Immunohistochemistry/Immunocytochemistry - For visualizing SETD5 protein localization in tissues and cells, which helps determine subcellular distribution patterns .

These applications provide complementary information about SETD5 expression, localization, and function, allowing researchers to build a comprehensive understanding of this protein's biological roles.

How can SETD5 antibodies be optimized for ChIP-seq experiments investigating its role in transcriptional regulation?

ChIP-seq optimization for SETD5 antibodies requires careful consideration of several factors:

• Antibody selection - Choose ChIP-certified antibodies specifically validated for chromatin immunoprecipitation applications . These antibodies have demonstrated ability to recognize SETD5 in its native chromatin context.

• Chromatin preparation - Since SETD5 binds to promoter regions and gene bodies as revealed by previous ChIP-seq studies , optimal chromatin fragmentation (200-500bp fragments) is critical for resolution.

• Cross-linking conditions - Standard formaldehyde fixation (1%, 10 minutes) works for most transcription factors, but for SETD5, which forms complexes with HCF-1 and PAF1 , dual cross-linking with additional protein-protein cross-linkers (such as DSG) may improve efficiency.

• Controls - Include:

  • Input DNA (pre-immunoprecipitation)

  • IgG negative control

  • Positive control (antibody against a known SETD5-associated protein like HCF-1)

• Sequencing depth - Aim for at least 20 million uniquely mapped reads for sufficient coverage of SETD5 binding sites.

• Data analysis - Focus on motif enrichment analysis for E2F1, E2F3, and GATA2/3 motifs, which have been identified in SETD5 binding sites . Compare SETD5 binding patterns with E2F1/4 and HCF-1 binding to identify cooperative mechanisms.

This approach will help detect SETD5 occupancy at genomic regions and its potential role in transcriptional regulation through association with E2F factors and HCF-1.

What experimental design would best investigate the discrepancy between increased immunophenotypic HSCs but impaired functional HSCs in SETD5-deficient models?

This interesting paradox in SETD5 research requires a comprehensive experimental design:

• Flow cytometry panel design:

  • Include traditional SLAM markers (CD150, CD48) alongside CD34 and Flk2

  • Add cell cycle markers (Ki67, BrdU) and apoptosis markers (Annexin V)

  • Consider adding additional functional markers such as Vwf, Mpl, and Nr4a1 that have been associated with specific HSC properties

• In vitro functional assays:

  • Colony-forming unit (CFU) assays with serial replating to assess self-renewal

  • Long-term culture-initiating cell (LTC-IC) assays to measure primitive HSC activity

  • Compare these results with flow cytometry counts to quantify the discrepancy

• Competitive transplantation experiments:

  • Primary and secondary transplants to assess long-term reconstitution ability

  • Limiting dilution assays to calculate functional HSC frequency

  • Track multiple lineages and use SETD5 antibodies to verify knockout efficiency

• Single-cell approaches:

  • Single-cell RNA-seq of sorted HSPCs from SETD5-deficient and control mice

  • CITE-seq (combining protein and RNA detection) to correlate surface marker expression with transcriptional profiles

  • Trajectory analysis to map differentiation paths and identify where deficiencies occur

• Molecular mechanism investigation:

  • ChIP-seq using SETD5 antibodies to identify direct genomic targets

  • RNA Pol II ChIP-seq to assess pausing release on E2F targets

  • Co-IP with SETD5 antibodies to confirm interactions with HCF-1 and PAF1 complex in HSCs

This experimental design would help resolve the paradox by determining whether increased immunophenotypic HSCs represent dysfunctional HSCs with altered quiescence states, as suggested by previous SETD5 research .

How can contradictory results between antibody-based detection and RNA expression data for SETD5 be reconciled and validated?

Discrepancies between antibody-based protein detection and RNA expression are common challenges in molecular biology research. A methodical approach to reconcile these contradictions includes:

• Multi-level validation strategy:

  • Test multiple independent antibodies against different SETD5 epitopes

  • Perform both standard and enhanced validation protocols

  • Include siRNA/shRNA knockdown controls to confirm antibody specificity

  • Use tagged SETD5 constructs (e.g., FLAG-tagged) for orthogonal validation

• Post-transcriptional regulation assessment:

  • Investigate miRNA-mediated regulation of SETD5 through reporter assays

  • Assess protein stability using cycloheximide chase experiments

  • Examine ubiquitination and other post-translational modifications affecting protein levels

• Technical considerations:

  • Review antigen retrieval methods for IHC, as improper retrieval can mask epitopes

  • Optimize antibody concentration through titration experiments

  • Use phosphatase/deacetylase inhibitors if PTMs affect antibody recognition

• Quantitative comparison:

  • Quantify RNA using RT-qPCR with multiple primer sets

  • Perform absolute protein quantification using recombinant SETD5 standards

  • Calculate protein-to-mRNA ratios across different tissues/conditions

• Consistency evaluation framework:

  • Apply the Human Protein Atlas consistency categories:

    • High consistency

    • Medium consistency

    • Low consistency

    • Very low consistency

    • Cannot be evaluated

This systematic approach helps determine whether discrepancies represent biological regulation or technical artifacts, leading to proper interpretation of SETD5 expression data across experimental contexts.

What is the optimal protocol for co-immunoprecipitation using SETD5 antibodies to identify novel interacting proteins?

The following protocol optimizes co-immunoprecipitation with SETD5 antibodies based on successful approaches from published research:

Materials needed:

• Validated SETD5 antibody (polyclonal or monoclonal)

• Control IgG (same species as SETD5 antibody)

• Protein A/G magnetic beads

• Lysis buffer (50mM Tris-HCl pH 7.4, 150mM NaCl, 1mM EDTA, 1% Triton X-100)

• Protease inhibitor cocktail

• Phosphatase inhibitors

Protocol:

• Cell preparation:

  • Use 1-2×10⁷ cells per condition (based on successful SETD5 Co-IP experiments)

  • For studying hematopoietic contexts, consider MEL cells as used in previous SETD5 studies

• Crosslinking (optional but recommended for SETD5):

  • Treat cells with 1% formaldehyde for 10 minutes at room temperature

  • Quench with 0.125M glycine for 5 minutes

  • This preserves weak or transient interactions with transcriptional complexes

• Lysis procedure:

  • Lyse cells in lysis buffer supplemented with protease and phosphatase inhibitors

  • Include 10mM NEM (N-ethylmaleimide) and 5mM sodium butyrate to preserve PTMs

  • Sonicate briefly (3×10s) to disrupt nuclear membranes without shearing chromatin

  • Centrifuge at 14,000×g for 10 minutes at 4°C

• Pre-clearing:

  • Incubate lysate with protein A/G beads for 1 hour at 4°C

  • Remove beads by centrifugation

• Immunoprecipitation:

  • Add 5μg of SETD5 antibody to pre-cleared lysate

  • Incubate overnight at 4°C with gentle rotation

  • Add pre-washed protein A/G beads and incubate for 2 hours at 4°C

  • Wash beads 5× with wash buffer (lysis buffer with 300mM NaCl)

• Elution and analysis:

  • Elute bound proteins by boiling in SDS sample buffer or using a gentle elution buffer

  • Analyze by mass spectrometry for unbiased identification of interactors

• Validation of novel interactions:

  • Confirm key interactions by reverse Co-IP

  • Verify with SETD5-FLAG constructs as orthogonal approach

This protocol is specifically designed to capture SETD5 interactions with transcriptional complexes like HCF-1 and PAF1 that have been previously identified , while also enabling discovery of novel interactors.

How can researchers generate and validate monoclonal antibodies against SETD5 for advanced applications?

Generating high-quality monoclonal antibodies against SETD5 requires systematic approach:

1. Antigen design and preparation:

• Identify unique, conserved, and accessible epitopes within SETD5

• Consider multiple regions: N-terminal domain, SET domain, and C-terminal region

• Express recombinant SETD5 fragments as fusion proteins with purification tags

• Ensure proper folding through circular dichroism analysis

2. Immunization strategies:

• Use standard mouse immunization with purified SETD5 protein/fragments

• Alternative: Consider STAT5-based B cell immortalization from human donors

  • This approach allows generation of fully human antibodies

  • Particularly useful for therapeutic applications

3. Hybridoma generation and screening:

• Fuse B cells with myeloma cells to create hybridomas

• Primary screening by ELISA against immunizing antigen

• Secondary screening by Western blot against endogenous SETD5

• Tertiary screening through immunoprecipitation efficiency

4. Comprehensive validation framework:

5. Clone selection and antibody characterization:

• Select 3-5 top-performing clones based on validation results

• Determine antibody isotype, affinity (by surface plasmon resonance)

• Epitope mapping through deletion mutants or peptide arrays

• Cross-reactivity testing against related SET domain proteins

6. Production and quality control:

• Establish stable production in serum-free media

• Implement lot-to-lot consistency testing

• Determine optimal storage conditions and shelf-life

For researchers using the STAT5-based approach for human monoclonal antibody generation , the process involves:

• Immortalizing memory B cells using inducible active STAT5 mutant

• Expanding B cell clones while STAT5 is "on" (prevents differentiation)

• Turning off STAT5 to allow antibody production

• Screening supernatants for SETD5-specific antibodies

• Retrieving immunoglobulin genes for recombinant expression

This comprehensive approach ensures generation of highly specific, well-characterized monoclonal antibodies suitable for advanced SETD5 research applications.

What are the critical considerations for using SETD5 antibodies in ChIP-seq experiments investigating transcriptional regulation in hematopoietic stem cells?

When using SETD5 antibodies for ChIP-seq in hematopoietic stem cells (HSCs), several critical factors must be considered to obtain reliable and interpretable results:

1. Antibody selection and validation:

• Use ChIP-certified antibodies specifically validated for this application

• Perform preliminary ChIP-qPCR on known SETD5 targets (E2F targets)

• Validate antibody specificity in relevant hematopoietic cell types

• Consider using FLAG-tagged SETD5 and anti-FLAG antibodies for higher specificity

2. HSC-specific experimental design:

• Cell number optimization: HSCs are rare, requiring protocol optimization for low cell numbers

• Consider using LSK+ or SLAM-HSC populations as defined in SETD5 studies

• Include controls lacking SETD5 (using conditional knockout models if available)

• Use parallel RNA-seq to correlate binding with expression changes

3. Chromatin preparation for HSCs:

• Optimize crosslinking conditions (1% formaldehyde, 10 minutes) for nuclear factors

• Use FACS-sorted populations to ensure homogeneity

• Implement carrier chromatin approaches for low cell numbers

• Monitor sonication efficiency carefully to achieve 200-500bp fragments

4. Data analysis tailored to SETD5 biology:

• Focus analysis on promoter regions and gene bodies where SETD5 preferentially binds

• Perform motif analysis for E2F1, E2F3, and GATA2/3 motifs

• Compare binding patterns with RNA Pol II occupancy to investigate pausing release

• Integrate with published E2F1/4 and HCF-1 ChIP-seq datasets

5. Biological interpretation framework:

• Analyze enrichment of cell cycle and self-renewal genes

• Compare HSC-specific SETD5 targets with those in other cell types

• Correlate SETD5 binding with quiescence/proliferation states of HSCs

• Investigate overlap with targets of SETD5-associated factors (HCF-1, PAF1 complex)

This methodological approach addresses the specific challenges of working with rare hematopoietic stem cells while leveraging the known biology of SETD5 in transcriptional regulation to maximize the value of ChIP-seq experiments.

How does SETD5 interact with the HCF-1 and PAF1 complexes to regulate RNA polymerase II pausing?

SETD5 functions as a key regulator of RNA polymerase II pausing through interactions with HCF-1 and the PAF1 complex. Understanding this mechanism requires sophisticated antibody-based approaches:

• Confirmed protein interactions:

  • Co-immunoprecipitation studies with SETD5 antibodies have identified consistent interactions with HCF-1, OGT, components of HDAC3 complex (HDAC3, NCOR1, TBL1X), and the PAF1 complex (PAF1, CTR9) .

  • These interactions were verified through both forward and reverse co-IP experiments and quantitative mass spectrometry .

• Genomic co-localization:

  • ChIP-seq experiments using SETD5 antibodies revealed that SETD5 genomic distribution is highly enriched at promoter regions and gene bodies .

  • Comparative analysis showed similar distribution patterns between SETD5 and E2F1/4 as well as HCF-1 .

  • Motif enrichment analysis of SETD5 binding sites revealed enrichment of E2F1 and E2F3 motifs, supporting functional interaction .

• Mechanistic model based on antibody studies:

  • SETD5 associates with HCF-1, which is known to interact with both repressive and activating E2Fs .

  • The SETD5-HCF-1 complex regulates RNA Pol II pausing at E2F target genes, particularly those involved in cell cycle regulation.

  • PAF1 complex, which facilitates transcriptional elongation, is recruited by the SETD5-HCF-1 complex to release paused Pol II.

  • This mechanism explains how SETD5 deficiency disrupts HSC quiescence by affecting E2F target gene expression .

• Methodological approaches to investigate this mechanism:

  • Sequential ChIP (ChIP-reChIP) with SETD5 and HCF-1 antibodies to confirm co-occupancy

  • Proximity ligation assays to visualize SETD5-HCF-1 interactions in situ

  • ChIP-seq for Pol II phosphorylation states (Ser5P vs. Ser2P) at SETD5 target genes

This model provides a molecular explanation for how SETD5 regulates hematopoietic stem cell quiescence through control of RNA Pol II pausing dynamics at E2F target genes.

What methodological approaches can distinguish between histone methyltransferase activity versus non-enzymatic functions of SETD5?

Despite containing a SET domain typically associated with histone methyltransferase activity, SETD5's enzymatic function remains questionable . The following methodological approaches can help distinguish between potential enzymatic and non-enzymatic functions:

1. Direct enzymatic activity assessment:

• In vitro methyltransferase assays:

  • Purify recombinant SETD5 protein or immunoprecipitate with SETD5 antibodies

  • Perform methyltransferase assays with radioactive S-adenosyl methionine (SAM)

  • Test multiple substrates: histone peptides, nucleosomes, non-histone proteins

  • Include positive control (known methyltransferase) and negative control (SET domain mutant)

• Mass spectrometry-based approaches:

  • Analyze methylation changes in histones and non-histone proteins upon SETD5 overexpression/depletion

  • Use heavy methyl-SILAC to track newly methylated residues

2. Structural and functional domain analysis:

• Structure-function studies:

  • Generate SET domain mutants targeting catalytic residues

  • Create domain deletion constructs (ΔSET, etc.)

  • Test rescue capacity in SETD5-deficient systems

  • Analyze protein interactions using co-IP with SETD5 antibodies

• Evolutionary analysis:

  • Compare SET domain sequence conservation with enzymatically active SET proteins

  • Identify potentially critical residue substitutions in catalytic sites

3. Chromatin-associated function assessment:

• ChIP-seq correlation analysis:

  • Compare SETD5 binding patterns with histone methylation marks

  • Look for enrichment/depletion of specific methylation states at SETD5-bound regions

  • Analyze changes in histone modifications upon SETD5 depletion

• Protein complex analysis:

  • Identify SETD5-associated proteins using antibody-based purification and mass spectrometry

  • Determine if SETD5 associates with other enzymatic complexes (e.g., HDACs)

  • Analyze co-recruitment patterns of SETD5 and interacting proteins

4. Scaffolding function evaluation:

• Protein interaction domain mapping:

  • Identify domains required for interaction with HCF-1 and PAF1 complex

  • Perform domain-swapping experiments to test scaffolding functions

  • Use competition assays to determine binding interfaces

• Transcriptional complex assembly analysis:

  • Use sequential ChIP to determine temporal assembly of complexes

  • Analyze Pol II pausing index changes upon SETD5 depletion

  • Test recruitment dependencies through depletion of complex components

Based on current research, SETD5 appears to function primarily through protein-protein interactions rather than enzymatic activity, as immunoblot analysis showed no obvious changes in histone methylation upon SETD5 manipulation . Its interaction with HCF-1 and the PAF1 complex suggests a scaffolding role in transcriptional regulation.

How can SETD5 antibodies be utilized to investigate its role in neurodevelopmental disorders?

SETD5 mutations have been identified as genetic causes of neurodevelopmental disorders . Antibody-based approaches offer powerful tools to investigate this connection:

• Patient-derived sample analysis:

  • Immunohistochemistry/Immunofluorescence:

    • Analyze SETD5 expression patterns in post-mortem brain tissues from patients with neurodevelopmental disorders versus controls

    • Examine cellular and subcellular localization using validated SETD5 antibodies

    • Co-stain with neural cell type markers to identify affected populations

  • Patient-derived cell models:

    • Generate induced pluripotent stem cells (iPSCs) from patients with SETD5 mutations

    • Differentiate into neural progenitors and mature neurons

    • Use SETD5 antibodies to track protein expression, localization, and complex formation

• Functional analysis of disease-associated mutations:

  • Protein stability and localization:

    • Introduce disease-associated SETD5 mutations into relevant cell types

    • Use SETD5 antibodies to assess protein levels, degradation rates, and subcellular localization

    • Compare wild-type versus mutant SETD5 protein half-life

  • Protein-protein interaction changes:

    • Perform co-IP with SETD5 antibodies to determine if mutations affect interactions with HCF-1, PAF1 complex, or HDAC3 complex

    • Use proximity ligation assays to visualize interaction changes in situ

    • Identify potential loss or gain of interactions specific to neural contexts

• Transcriptional regulation assessment:

  • ChIP-seq in neural models:

    • Map SETD5 binding sites in neural progenitors and mature neurons

    • Compare wild-type versus mutant SETD5 genomic occupancy

    • Identify neurodevelopmental genes under SETD5 regulation

  • RNA Pol II pausing analysis:

    • Examine if SETD5 regulates RNA Pol II pausing in neural cells as it does in hematopoietic cells

    • Identify neural-specific targets potentially affected by SETD5 mutations

    • Compare E2F target regulation between neural and hematopoietic contexts

• Animal model validation:

  • Conditional knockout models:

    • Generate brain-specific SETD5 knockout or mutation models

    • Use SETD5 antibodies to confirm deletion efficiency

    • Analyze developmental phenotypes and correlate with molecular changes

  • Rescue experiments:

    • Attempt phenotypic rescue with wild-type SETD5

    • Test different SETD5 mutants for rescue capacity

    • Use antibodies to verify expression of rescue constructs

This comprehensive approach leverages SETD5 antibodies to connect molecular mechanisms to neurodevelopmental phenotypes, potentially revealing therapeutic targets for SETD5-associated disorders.