ELF1 Antibody

What is ELF1 and why is it significant in biological research?

ELF1 (E74-like factor 1) is a member of the ETS family of transcription factors that plays critical roles in gene regulation. In humans, it is a 619 amino acid protein with a molecular weight of approximately 67.5 kDa that localizes to the nucleus . ELF1 is widely expressed across many tissue types and has gained significant research interest due to its roles in regulating gene expression during T cell activation and its recently discovered broad antiviral activity . ELF1 activates the LYN and BLK promoters and is also involved in HIV-2 gene expression regulation through the T-cell receptor pathway .

What are the most commonly used applications for ELF1 antibodies?

ELF1 antibodies are primarily used in Western Blotting (WB), which is the most widely reported application across commercial sources . Other common applications include ELISA, Immunofluorescence (IF), Immunocytochemistry (ICC), and Immunohistochemistry (IHC) . For specific experimental designs, some ELF1 antibodies have been validated for Immunoprecipitation (IP), particularly those targeting specific domains or epitopes within the protein . When selecting an antibody, researchers should verify the validation data for their specific application of interest.

How many isoforms of ELF1 exist and how do antibodies recognize them?

Up to two different isoforms of the ELF1 protein have been reported in humans . When selecting an antibody, researchers should consider whether the antibody will recognize both isoforms, which depends on the epitope targeted by the antibody. For example, antibodies targeting the C-terminal region, such as those directed against the peptide sequence AMKQNELLEPNSF, are expected to recognize both reported isoforms . For experiments requiring isoform specificity, researchers should carefully select antibodies that target unique regions present in only one isoform.

How does ELF1 contribute to the antiviral response and how is this measured experimentally?

ELF1 exhibits a broad antiviral activity against diverse RNA and DNA viruses, but uniquely, it inhibits viruses only after multi-cycle replication rather than during the first round of viral replication . This delayed antiviral activity is distinct from other immediate interferon-stimulated genes (ISGs) like IRF1.

To measure this experimentally, researchers have used:

• High-content microscopy assays that compare viral infection at early (12 hours post-infection) versus late (48 hours post-infection) timepoints

• ELF1 knockdown using morpholino oligomers followed by viral titer quantification

• In vivo mouse models with reduced Elf1 expression to determine susceptibility to viral infection

• Expression of ELF1 mutants lacking crucial domains (TF domain, ETS domain, or R8A mutation) to verify the transcription factor activity requirement

These methodologies have revealed that ELF1 triggers a second wave of antiviral gene expression distinct from the immediate interferon response, providing an additional layer of innate host defense .

What is the relationship between ELF1 and MEIS1 expression, and how has this been experimentally validated?

ELF1 has been identified as a transcriptional regulator of MEIS1, a homeobox gene implicated in leukemia and Restless Leg Syndrome . This relationship was experimentally validated through multiple complementary approaches:

• Chromatin status analysis revealing a correlation between MEIS1 promoter accessibility and expression

• Truncation and mutation studies identifying a conserved ETS binding site 289bp upstream of the MEIS1 transcription start site

• Electrophoretic mobility shift assays (EMSA) demonstrating ELF1 binding to this site

• Chromatin immunoprecipitation (ChIP) experiments confirming ELF1 enrichment on the MEIS1 promoter in K562 cells and primary human samples

• siRNA-mediated knockdown of ELF1 resulting in decreased MEIS1 expression

These findings establish ELF1 as an important positive regulator of MEIS1 expression, which has implications for understanding both normal development and disease states where MEIS1 is implicated.

How does ELF1's transcriptional regulatory activity differ from other interferon-responsive transcription factors?

ELF1's transcriptional regulatory activity differs from other interferon-responsive transcription factors like IRF1 in several key aspects:

• Temporal dynamics: ELF1 initiates a second wave of gene expression following the immediate interferon response, extending the antiviral program temporally

• Target gene specificity: ELF1 regulates a distinct set of genes compared to the ISGF3-regulated immediate interferon response genes

• Mechanism of viral inhibition: Unlike IRF1 which inhibits viruses in the first round of replication, ELF1 exclusively inhibits multi-cycle replication, suggesting different mechanistic targets

• Independence from interferon signaling: ELF1's antiviral effect persists in the absence of STAT1 or with inhibition of JAK phosphorylation, demonstrating independence from canonical interferon signaling

This unique regulatory profile positions ELF1 as a component of an additional layer of innate host response that amplifies and extends the immediate interferon response through a distinct transcriptional program .

What considerations should guide the selection of an appropriate ELF1 antibody for a specific experimental application?

When selecting an ELF1 antibody, researchers should consider:

• Target epitope location: Antibodies targeting different regions (N-terminal, C-terminal, or specific amino acid sequences) may have different specificities and applications. For example, C-terminal antibodies (targeting AMKQNELLEPNSF) recognize both reported isoforms

• Host species: Available in goat, rabbit, and mouse hosts, which affects secondary antibody selection and potential cross-reactivity issues

• Clonality: Both monoclonal (e.g., mouse monoclonal C-4) and polyclonal antibodies are available, with trade-offs between specificity and epitope recognition

• Validated applications: Verify that the antibody has been validated for your specific application (WB, IF, IHC, IP, ELISA)

• Species reactivity: Confirm reactivity with your experimental species; many ELF1 antibodies react with human samples, while some cross-react with mouse, rat, and other species

• Conjugation status: Available unconjugated or conjugated to agarose, HRP, fluorescent tags, which affects detection strategy

For critical experiments, validation with multiple antibodies targeting different epitopes is recommended to confirm specificity of observed signals.

What methods can be used to validate the specificity of an ELF1 antibody?

To validate ELF1 antibody specificity, researchers should employ multiple complementary approaches:

• Knockdown/knockout controls: Use siRNA, shRNA, CRISPR/Cas9, or morpholino oligomers to reduce ELF1 expression and confirm corresponding reduction in antibody signal

• Rescue experiments: After ELF1 knockdown, express exogenous ELF1 (resistant to the knockdown method) and verify restoration of antibody signal

• Multiple antibodies comparison: Use antibodies targeting different ELF1 epitopes and confirm consistent detection patterns

• Expression pattern consistency: Verify that detected expression patterns match expected tissue distribution (widely expressed but enriched in pancreas, spleen, thymus, and peripheral blood leukocytes)

• Molecular weight confirmation: Ensure detected bands match expected molecular weight (67.5 kDa) and isoform patterns

• Peptide competition: Pre-incubate antibody with the immunizing peptide to demonstrate signal reduction from specific blocking

These validation steps are critical for ensuring experimental reproducibility and accurate interpretation of results involving ELF1 detection.

What are the optimal protocols for detecting ELF1 in Western blot applications?

For optimal detection of ELF1 by Western blot, researchers should consider the following protocol elements:

• Sample preparation:

  • Extract nuclear proteins, as ELF1 is primarily localized in the nucleus

  • Use appropriate protease inhibitors to prevent degradation

  • For cell lysates or mouse lung homogenates, protocols using anti-ELF1 antibody at 1:5000 dilution have been successful

• Electrophoresis conditions:

  • Use 8-10% SDS-PAGE gels appropriate for resolving the 67.5 kDa ELF1 protein

  • Include positive controls such as K562 cell lysates, which express ELF1

• Transfer and detection:

  • Standard PVDF or nitrocellulose membranes are suitable

  • Blocking with 5% non-fat milk or BSA in TBST is generally effective

  • Primary antibody incubation times of 1-2 hours at room temperature or overnight at 4°C

  • Anti-mouse or anti-rabbit HRP-conjugated secondary antibodies depending on the primary antibody host species

• Verification strategies:

  • Run parallel blots with different ELF1 antibodies targeting distinct epitopes

  • Include knockdown samples as negative controls

  • Expected band size of approximately 67.5 kDa

This methodological approach has been validated in studies examining ELF1's role in antiviral responses .

How can ChIP assays be optimized for studying ELF1 binding to target promoters?

For optimizing Chromatin Immunoprecipitation (ChIP) assays to study ELF1 binding to target promoters:

• Crosslinking and chromatin preparation:

  • Standard 1% formaldehyde crosslinking for 10 minutes at room temperature is typically sufficient

  • Sonication conditions should be optimized to generate 200-500 bp DNA fragments

• Antibody selection and immunoprecipitation:

  • Use ChIP-validated ELF1 antibodies; for example, ELF1 antibody (C-20 X) from Santa Cruz Biotechnology has been successfully used in published ChIP experiments

  • Include appropriate negative controls (IgG from the same species as the primary antibody)

  • Include positive controls (antibodies against general transcription factors or histones)

• Target analysis:

  • Design primers for known ELF1 binding sites, such as the conserved ETS binding site located 289bp upstream of the MEIS1 transcription start site

  • Both conventional PCR and qPCR can be used for analyzing immunoprecipitated DNA

  • Consider including analysis of known ELF1 targets like LYN and BLK promoters as positive controls

• Data validation:

  • Confirm enrichment relative to IgG control and input chromatin

  • Validate findings with electrophoretic mobility shift assays (EMSA) as complementary approach

  • Consider comparing results in cells with and without ELF1 knockdown

This approach has successfully identified ELF1 as a regulator of MEIS1 expression through direct promoter binding .

What experimental design is recommended for assessing ELF1's role in antiviral responses?

Based on published research, an optimal experimental design for assessing ELF1's role in antiviral responses includes:

• In vitro assessment of viral replication kinetics:

  • Exogenous expression of ELF1 vs. controls (empty vector and ELF1 mutants like R8A)

  • Low MOI infection for multi-cycle replication studies

  • Time-course analysis at both early (12h) and late (36-48h) timepoints

  • High-content microscopy to quantify infected cells

• Mechanistic investigation:

  • Comparison with known antiviral factors (e.g., IRF1) as positive controls

  • Parallel analysis in STAT1-deficient cells or with JAK inhibitors to assess interferon independence

  • RNA-seq to identify ELF1-regulated genes distinct from immediate interferon signatures

• Loss-of-function studies:

  • Knockdown of endogenous ELF1 using morpholino oligomers targeting 5'UTR

  • Rescue experiments with exogenous ELF1 expression that is not targeted by the knockdown approach

  • Western blot verification of knockdown efficiency

• In vivo validation:

  • Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) for in vivo knockdown in mice

  • Viral challenge (e.g., influenza A virus)

  • Measurements of weight loss, mortality, and viral titers in lungs

This comprehensive approach allows for establishing ELF1's antiviral function at multiple levels from molecular mechanisms to physiological relevance.

What are common challenges when working with ELF1 antibodies and how can they be addressed?

Researchers may encounter several challenges when working with ELF1 antibodies:

• Multiple bands in Western blot:

  • Cause: Could indicate detection of both isoforms, post-translational modifications, or non-specific binding

  • Solution: Use antibodies targeting different epitopes to confirm specific bands; include knockdown controls; optimize blocking conditions; consider using monoclonal antibodies for higher specificity

• Weak or absent signal:

  • Cause: Low ELF1 expression in sample, epitope masking, or antibody sensitivity issues

  • Solution: Enrich nuclear fractions since ELF1 is nuclear-localized; optimize extraction protocols; consider alternative antibodies targeting different epitopes

• High background in immunostaining:

  • Cause: Non-specific binding, excessive antibody concentration, inadequate blocking

  • Solution: Titrate antibody concentrations; extend blocking times; use alternative blocking reagents; include appropriate controls

• Inconsistent ChIP results:

  • Cause: Variable crosslinking efficiency, inefficient sonication, antibody-epitope accessibility issues

  • Solution: Optimize crosslinking time; verify chromatin fragmentation; test multiple ELF1 antibodies; include known ELF1 target regions as positive controls

• Discrepancies between transcript and protein levels:

  • Cause: Post-transcriptional regulation, protein stability differences

  • Solution: Parallel analysis of mRNA and protein; pulse-chase experiments to assess protein stability; consider analysis of ELF1 post-translational modifications

These troubleshooting approaches have been effective in published studies involving ELF1 characterization .

How can researchers distinguish between direct and indirect effects of ELF1 on gene expression?

Distinguishing direct from indirect effects of ELF1 on gene expression requires a multi-faceted experimental approach:

• Integrated genomic analysis:

  • Combine ChIP-seq to identify genome-wide ELF1 binding sites with RNA-seq to identify ELF1-dependent genes

  • Direct targets should show both ELF1 binding and expression changes upon ELF1 manipulation

  • Analyze enrichment of ETS binding motifs in promoters of ELF1-regulated genes

• Temporal analysis:

  • Use inducible ELF1 expression systems with time-course RNA-seq

  • Direct targets typically show more rapid expression changes than indirect targets

  • ELF1 has been shown to trigger a second wave of gene expression following interferon stimulation

• Reporter assays:

  • Test promoter regions of potential target genes with and without the ELF1 binding site

  • Mutation analysis of ETS binding sites, as demonstrated for the MEIS1 promoter (289bp upstream of TSS)

  • Co-expression of ELF1 or ELF1 mutants (e.g., R8A DNA-binding mutant) with reporters

• Domain mutation approaches:

  • Compare effects of wild-type ELF1 with DNA-binding deficient mutants (R8A) or transcription activation domain mutants

  • Direct targets should be more sensitive to DNA-binding domain mutations

This integrated approach has been successfully applied to distinguish ELF1's direct regulation of MEIS1 and to characterize its direct antiviral transcriptional program .

What considerations are important when analyzing ELF1 in different cell types and tissues?

When analyzing ELF1 across different cell types and tissues, researchers should consider:

• Expression level variations:

  • ELF1 is widely expressed but with tissue-specific patterns

  • Highly expressed in pancreas, spleen, thymus, and peripheral blood leukocytes

  • Moderately expressed in heart, placenta, lung, liver, skeletal muscle, kidney, prostate, ovary, small intestine, and colon

  • Weakly expressed in brain and testis

  • Adjust antibody concentrations and detection methods accordingly

• Developmental context:

  • In fetal tissues, ELF1 is highly expressed in heart, lung, liver, and kidney, with weaker expression in brain

  • Consider developmental stage when analyzing ELF1 function or expression

• Species differences:

  • ELF1 orthologs have been reported in mouse, rat, bovine, frog, chimpanzee, and chicken species

  • Verify antibody cross-reactivity for the specific species being studied

  • Consider potential functional differences between species orthologs

• Cell type-specific cofactors:

  • ELF1 function may depend on interaction with cell type-specific cofactors

  • Different cell types may express different ELF1 isoforms or post-translationally modified forms

  • In lymphoid cells, ELF1 functions as a lymphoid-specific ETS family member regulating gene expression during T cell activation

• Subcellular localization:

  • Confirm nuclear localization in all cell types under study

  • Consider whether stimulation or stress conditions affect localization

These considerations are important for accurately interpreting ELF1's function across different biological contexts and for designing appropriate experimental controls.

What are the recommended techniques for studying ELF1 post-translational modifications?

For studying post-translational modifications (PTMs) of ELF1, researchers should consider these techniques:

• PTM-specific antibodies:

  • Use antibodies specifically recognizing phosphorylated, acetylated, or other modified forms of ELF1

  • Validate specificity using phosphatase treatment, deacetylase treatment, or other relevant enzymes

• Mass spectrometry-based approaches:

  • Immunoprecipitate ELF1 using validated antibodies like the mouse monoclonal C-4 antibody

  • Analyze by LC-MS/MS to identify and map PTMs

  • Compare PTM profiles under different cellular conditions (e.g., viral infection, interferon stimulation)

• Gel mobility shift assays:

  • Analyze mobility shifts associated with phosphorylation or other PTMs

  • Combine with phosphatase treatment to confirm phosphorylation-dependent shifts

  • Western blotting with standard ELF1 antibodies can detect mobility shifts indicative of PTMs

• Functional studies of PTM sites:

  • Generate site-directed mutants of potential PTM sites (e.g., S→A for phosphorylation sites)

  • Assess functional consequences on ELF1's transcriptional activity and antiviral function

  • Compare wild-type and mutant ELF1 activity in reporter assays or viral inhibition assays as described in published studies

• Temporal analysis of modifications:

  • Analyze PTM dynamics during viral infection or interferon stimulation

  • This may be particularly relevant given ELF1's delayed antiviral activity, which could be regulated by post-translational mechanisms

These approaches can help elucidate how PTMs contribute to the regulation of ELF1's transcriptional and antiviral activities.

What are promising areas for future research on ELF1 function and regulation?

Based on current knowledge, several promising research directions for ELF1 include:

• Comprehensive mapping of the ELF1-regulated transcriptome:

  • Characterize the complete set of genes directly regulated by ELF1 across different cell types

  • Identify tissue-specific targets and context-dependent regulation

  • Compare ELF1-regulated genes with those regulated by other ETS family members

• ELF1 in viral immunity beyond acute infection:

  • Investigate ELF1's role in persistent viral infections and viral latency

  • Explore therapeutic potential of enhancing ELF1 activity for broad-spectrum antiviral applications

  • Further characterize the mechanism of ELF1's delayed antiviral activity

• ELF1 in disease states:

  • Expand understanding of ELF1's role in leukemia through its regulation of MEIS1

  • Investigate potential roles in other cancers and immune-related disorders

  • Explore connections between ELF1 and diseases where its target genes are implicated

• Structural biology of ELF1:

  • Determine crystal structures of ELF1 bound to DNA targets

  • Characterize structural changes associated with post-translational modifications

  • Use structural information to design specific modulators of ELF1 activity

• Integration with other cellular pathways:

  • Further characterize the relationship between ELF1 and interferon signaling

  • Explore cross-talk with other transcriptional networks in immune responses

  • Investigate potential regulation by non-coding RNAs