sfr1 Antibody

What is SFR1 and why is it important in research contexts?

SFR1 (SWI5-dependent homologous recombination repair protein 1) is a nuclear protein that forms a complex with SWI5 required for DNA double-strand break repair via homologous recombination . It also functions as a transcriptional modulator for ESR1 (estrogen receptor alpha) . Research into SFR1 is vital for understanding DNA repair mechanisms, genomic stability, and potential connections to diseases associated with DNA repair defects, including atrial septal defects .

What applications are SFR1 antibodies commonly used for in research?

SFR1 antibodies are primarily used for Western blotting (WB), immunoprecipitation (IP), immunohistochemistry (IHC), and immunofluorescence (IF) applications . These applications enable researchers to detect endogenous levels of SFR1 in various tissue and cell samples, examine its subcellular localization, and study its interactions with other proteins in the DNA repair pathway.

What species reactivity should be considered when selecting an SFR1 antibody?

Available SFR1 antibodies show different species reactivity profiles. Some antibodies detect human SFR1 only, while others cross-react with mouse and rat orthologs . When working with animal models, it's essential to confirm the species reactivity of the antibody. For example, the SFR1 polyclonal antibody from St John's Laboratory (STJ194162) shows reactivity to human, mouse, and rat samples , while some other commercial antibodies may have more limited species reactivity.

What is the optimal protocol for detecting SFR1 in nuclear fractions via Western blot?

For optimal detection of SFR1 via Western blot, researchers should:

• Prepare nuclear extracts using a nuclear extraction protocol with protease inhibitors

• Load 20-40 μg of nuclear protein per lane

• Use freshly prepared SDS-PAGE gels (10-12%)

• Transfer to PVDF membrane at low voltage (30V) overnight at 4°C

• Block with 5% non-fat milk in TBST for 1 hour

• Incubate with primary SFR1 antibody at optimal dilution (typically 1:500-1:2000)

• Wash thoroughly with TBST

• Incubate with appropriate HRP-conjugated secondary antibody

• Develop using enhanced chemiluminescence

The expected molecular weight of SFR1 is approximately 35 kDa . Always include positive and negative controls, such as extracts from SFR1-knockout cell lines, to validate specificity .

How should researchers optimize immunofluorescence protocols for SFR1 detection in the nucleus?

For optimal immunofluorescence detection of SFR1:

• Grow cells on glass coverslips to 70-80% confluence

• Fix cells with 4% paraformaldehyde for 15 minutes at room temperature

• Permeabilize with 0.2% Triton X-100 in PBS for 10 minutes

• Block with 5% BSA in PBS for 1 hour

• Incubate with primary SFR1 antibody (1:50-1:500 dilution) overnight at 4°C

• Wash 3× with PBS

• Incubate with fluorophore-conjugated secondary antibody for 1 hour at room temperature

• Counterstain nuclei with DAPI

• Mount using anti-fade mounting medium

Since SFR1 is a nuclear protein that co-localizes with ESR1 in the nucleus , strong nuclear staining should be observed. Including a DNA damage-inducing agent, such as ionizing radiation or etoposide treatment, may enhance nuclear foci formation of SFR1 at double-strand break sites.

What are the key considerations for immunoprecipitation experiments with SFR1 antibodies?

For successful immunoprecipitation of SFR1:

• Prepare cell lysates in a non-denaturing lysis buffer (50 mM Tris-HCl pH 8.0, 150 mM NaCl, 1% NP-40, protease inhibitors)

• Pre-clear lysate with protein A/G beads

• Incubate cleared lysate with SFR1 antibody (1:50 dilution recommended for IP)

• Add protein A/G beads and incubate overnight at 4°C with gentle rotation

• Wash beads extensively (at least 5 times) with wash buffer

• Elute by boiling in SDS sample buffer

• Analyze by Western blot

For co-immunoprecipitation experiments to study SFR1-SWI5 complex formation, researchers should probe the immunoprecipitated material with antibodies against known interaction partners like SWI5 or RAD51 .

How can researchers validate SFR1 antibody specificity for their experimental systems?

Rigorous validation of SFR1 antibody specificity should include:

• Genetic controls: Use SFR1 knockout cell lines compared to isogenic parental controls

• Peptide competition: Pre-incubate antibody with immunizing peptide to confirm signal reduction

• siRNA knockdown: Compare signal between SFR1-depleted and control cells

• Recombinant protein: Use purified SFR1 protein as a positive control

• Multiple antibodies: Confirm results with antibodies recognizing different epitopes

• Expected localization: Verify nuclear localization consistent with SFR1's known function

Recent studies highlight the importance of antibody validation for reproducibility in research. For example, a systematic study of sFRP-1 antibodies showed significant variability in performance across different applications , emphasizing the need for similar validation approaches with SFR1 antibodies.

What are the differences in detecting endogenous versus overexpressed SFR1 in research models?

Detecting endogenous versus overexpressed SFR1 presents several technical considerations:

When studying SFR1's role in homologous recombination, endogenous detection provides more physiologically relevant insights, while overexpression systems may be useful for structure-function analyses of specific domains.

How should researchers design experiments to study the SWI5-SFR1 complex in DNA repair pathways?

To effectively study the SWI5-SFR1 complex in DNA repair:

• Immunoprecipitation approach:

  • Perform reciprocal co-IPs using both SFR1 and SWI5 antibodies

  • Analyze complex formation before and after DNA damage induction

  • Include RAD51 detection to assess recruitment to the complex

• Functional assays:

  • Employ homologous recombination reporter assays

  • Compare wild-type cells with SFR1-depleted or mutant cells

  • Assess sensitivity to DNA-damaging agents (e.g., ionizing radiation, camptothecin)

• Live-cell imaging:

  • Generate fluorescently tagged SFR1 and SWI5 constructs

  • Track complex formation and recruitment to DNA damage sites

  • Use complementary antibody staining to validate observations

Studies have shown that SFR1 contains an intrinsically disordered N-terminus that cooperatively binds RAD51, and deletion of this domain impairs RAD51 stimulation in vitro and renders cells sensitive to DNA damage . Experiments should be designed to dissect these structure-function relationships.

What are common issues in Western blot detection of SFR1 and how can they be resolved?

Several challenges may arise when detecting SFR1 by Western blot:

Since SFR1 is predominantly nuclear, enriching the nuclear fraction can significantly improve detection sensitivity by concentrating the target protein .

How can researchers differentiate between specific and non-specific signals when using SFR1 antibodies?

To distinguish between specific and non-specific signals:

• Use knockout controls: Compare signals between wild-type and SFR1-knockout samples

• Perform peptide competition: Pre-incubate antibody with immunizing peptide

• Compare multiple antibodies: Use antibodies targeting different epitopes of SFR1

• Verify molecular weight: Specific SFR1 signal should appear at ~35 kDa

• Examine subcellular localization: SFR1 should show nuclear localization

• Analyze signal response: SFR1 signal should increase after DNA damage induction in functional studies

• Include positive controls: Use cell lines known to express SFR1

What factors affect the reproducibility of SFR1 antibody experiments across different research settings?

Several factors can impact the reproducibility of SFR1 antibody experiments:

• Antibody lot variation: Different manufacturing lots may show performance differences

• Sample preparation methods: Variations in lysis buffers, fixation protocols, and protein extraction efficiency

• Cell type and state: SFR1 expression levels and localization may vary across cell types and cell cycle phases

• Technical parameters: Differences in incubation times, temperatures, and washing stringency

• Detection systems: Variability in sensitivity of ECL reagents or fluorescent detection systems

• Antibody storage and handling: Freeze-thaw cycles and improper storage can reduce antibody efficacy

• Protocol standardization: Lack of standardized protocols between laboratories

To enhance reproducibility, researchers should thoroughly document all experimental parameters and consider publishing detailed protocols with their findings, as demonstrated in recent antibody characterization studies .

How do monoclonal versus polyclonal SFR1 antibodies compare in research applications?

The choice between monoclonal and polyclonal SFR1 antibodies involves several considerations:

Most commercially available SFR1 antibodies are polyclonal (e.g., STJ194162 from St John's Laboratory , PA5-58861 from Thermo Fisher ), which may be advantageous for detecting low-abundance nuclear proteins like SFR1.

What considerations should guide the selection of SFR1 antibodies for different experimental techniques?

When selecting SFR1 antibodies for specific techniques:

Researchers should carefully review the validation data provided by manufacturers and published studies that have successfully used specific antibodies for their technique of interest.

How do approaches for studying SFR1 differ between cancer research and DNA repair mechanism investigations?

The research focus and methodological approaches differ when studying SFR1 in different contexts:

While SFR1 has been primarily studied in the context of DNA repair mechanisms , its role as a transcriptional modulator for ESR1 suggests potential significance in hormone-responsive cancers that merits further investigation.

How can SFR1 antibodies be utilized in studying the relationship between DNA repair defects and disease phenotypes?

SFR1 antibodies can advance research connecting DNA repair deficiencies to diseases through:

• Clinical sample analysis: Examining SFR1 expression/localization in tissues from patients with DNA repair disorders

• Biomarker development: Assessing SFR1 complex formation as a potential biomarker for DNA repair capacity

• Therapeutic response prediction: Correlating SFR1 status with sensitivity to PARP inhibitors or radiation therapy

• Genetic disorder studies: Investigating SFR1 in atrial septal defects and other conditions linked to DNA repair deficiencies

• Cancer progression analysis: Examining changes in SFR1 localization during tumor evolution

Given SFR1's role in the SWI5-SFR1 complex that cooperatively stimulates RAD51 , antibodies that can detect specific forms of the protein complex may provide insights into disease mechanisms and potential therapeutic approaches.

What methodological advances are needed to better study the dynamics of SFR1 in live-cell systems?

To advance live-cell studies of SFR1 dynamics, several methodological developments are needed:

• Validation of fluorescent protein fusions: Careful validation that tagging doesn't disrupt SFR1 function

• Conformation-specific antibodies: Development of antibodies that recognize specific functional states

• Antibody fragments for live-cell imaging: Creation of cell-permeable antibody fragments or nanobodies

• Proximity labeling approaches: Optimization of BioID or APEX2 fusions to map dynamic interactomes

• Super-resolution microscopy compatibility: Antibodies compatible with STORM, PALM, or other super-resolution techniques

• Multiplexed detection methods: Simultaneous visualization of SFR1, SWI5, RAD51, and DNA damage markers

These advances would enable researchers to track the real-time recruitment and activity of SFR1 during DNA repair processes, providing deeper insights into the temporal dynamics of homologous recombination.

How might spatial transcriptomics and proteomics technologies integrate with SFR1 antibody applications?

The integration of spatial technologies with SFR1 antibody applications presents exciting research opportunities:

• Spatial proteomics: Using SFR1 antibodies in Imaging Mass Cytometry or CODEX to map SFR1 distribution relative to other DNA repair factors in tissue sections

• Chromatin immunoprecipitation sequencing (ChIP-seq): Applying SFR1 antibodies to map genome-wide binding sites, particularly in relation to ESR1-mediated transcription

• Proximity ligation assays: Combining SFR1 antibodies with antibodies against interaction partners to visualize complex formation in situ

• Single-cell proteomics: Employing SFR1 antibodies in single-cell Western blotting to assess cell-to-cell variability in DNA repair capacity

• Spatial transcriptomics correlation: Correlating SFR1 protein localization with local gene expression patterns using matched sections