SPAC1687.14c Antibody

What is the SPAC1687.14c gene product in Schizosaccharomyces pombe?

SPAC1687.14c encodes the Srs2 protein in fission yeast (Schizosaccharomyces pombe), which functions as a DNA helicase. This protein shares approximately 27% amino acid identity and 40% similarity over a 698 amino acid region with its ortholog in Saccharomyces cerevisiae (budding yeast) . The S. pombe Srs2 protein consists of 887 amino acid residues with a calculated molecular weight of 101,061 Da. Unlike some other helicases, the C-terminal regions of Srs2 proteins in both yeasts lack significant homology either to each other or to other known proteins . Functionally, Srs2 is involved in multiple DNA maintenance processes including DNA repair, recombination, and checkpoint signaling following DNA damage.

What are the available formats of SPAC1687.14c/Srs2 antibodies?

Research-grade antibodies targeting S. pombe Srs2 are typically available as:

• Monoclonal antibodies derived from mouse hybridomas

• Polyclonal antibodies raised in rabbits

• Antibodies recognizing epitope-tagged versions of the protein (e.g., HA-tagged Srs2)

For Western blotting applications, the HA-tagged version of Srs2 has been successfully detected using anti-HA monoclonal antibodies (such as HA-11 from BAbCO) at a concentration of 1 μg/ml in conjunction with horseradish peroxidase-conjugated anti-mouse secondary antibodies . The epitope-tagging approach allows for reliable detection of the approximately 100 kDa protein on immunoblots.

How can I validate the specificity of a SPAC1687.14c/Srs2 antibody?

Validating antibody specificity for Srs2 should involve multiple complementary approaches:

Primary Validation Methods:

• Western blot comparison between wild-type and srs2Δ strains: The antibody should detect a band at ~100 kDa in wild-type samples that is absent in the deletion strain .

• Epitope-tagged controls: Compare detection between untagged and epitope-tagged versions of Srs2 (the band should shift according to the tag size).

• Immunoprecipitation followed by mass spectrometry: This confirms that the antibody is pulling down the correct protein and allows assessment of cross-reactivity.

Additional Validation Approaches:

• Immunofluorescence microscopy: Compare staining patterns between wild-type and srs2Δ strains.

• ChIP-seq validation: If using the antibody for chromatin immunoprecipitation, verify enrichment at expected genomic locations based on known Srs2 functions.

Since Srs2 abundance does not appear to change significantly after treatment with DNA damaging agents or replication inhibitors , both treated and untreated samples can serve as positive controls with similar band intensities.

What methods are most effective for analyzing Srs2 recruitment to chromatin during DNA repair?

For studying Srs2 recruitment to chromatin during DNA repair processes, consider these methodological approaches:

Chromatin Immunoprecipitation (ChIP) Approaches:

• ChIP-qPCR: For targeted analysis of specific loci of interest.

• ChIP-seq: For genome-wide analysis of Srs2 binding sites.

• ChIP-on-chip: As used in previous studies of chromatin-bound proteins in S. pombe .

Optimization Considerations:

• Crosslinking conditions: Typically 1% formaldehyde for 10-15 minutes at room temperature.

• Sonication parameters: Optimize to generate DNA fragments of 200-500 bp.

• Antibody specificity: Use validated antibodies against either native Srs2 or epitope-tagged versions.

• Controls: Include no-antibody controls, isotype controls, and srs2Δ samples.

Analytical Approaches:

• Time-course experiments: Following UV irradiation or HU treatment to track temporal recruitment patterns.

• Co-localization studies: Combined with ChIP for recombination proteins like Rhp51 (Rad51 homolog).

• Quantitative proteomics: Can be used in conjunction with ChIP to identify proteins co-localizing with Srs2 at sites of DNA damage .

How do I troubleshoot weak or inconsistent signals when using anti-Srs2 antibodies?

When encountering weak or inconsistent signals with anti-Srs2 antibodies, consider these troubleshooting steps:

For Western Blotting:

• Protein extraction method: Use robust extraction methods optimized for nuclear proteins, such as TCA precipitation or specialized nuclear extraction buffers.

• Protein degradation: Add protease inhibitors freshly to all buffers and keep samples cold.

• Transfer conditions: Optimize transfer time and buffer composition for high molecular weight proteins (~100 kDa).

• Blocking conditions: Test different blocking agents (BSA vs. milk) and concentrations.

• Antibody concentration: Titrate primary antibody; consider overnight incubation at 4°C.

• Detection method: Enhanced chemiluminescence (ECL) provides good sensitivity, as used in previous studies .

For Immunoprecipitation:

• Lysis conditions: Test different detergents and salt concentrations.

• Antibody binding: Extend incubation time with the antibody.

• Bead choice: Compare protein A vs. protein G beads for optimal capture.

• Elution conditions: Optimize to ensure complete elution of the target protein.

For Immunofluorescence:

• Fixation method: Compare formaldehyde vs. methanol fixation.

• Permeabilization: Adjust detergent concentration for optimal antibody access.

• Signal amplification: Consider tyramide signal amplification for weak signals.

How can I investigate the functional relationship between Srs2 and the homologous recombination pathway?

To investigate the relationship between Srs2 and homologous recombination in S. pombe:

Genetic Approaches:

• Epistasis analysis: Generate double and triple mutants combining srs2Δ with mutations in homologous recombination genes (rhp51Δ, rhp54Δ, rad22Δ) and measure phenotypes such as growth rate, DNA damage sensitivity, and recombination frequency .

Quantitative Analysis:
Compare the following parameters between wild-type, single, and double mutants:

This data shows that deletion of both Srs2 and Rhp51 (the Rad51 homolog involved in homologous recombination) causes a synthetic growth defect, with increased doubling time and decreased plating efficiency compared to either single mutant .

Biochemical Approaches:

• Co-immunoprecipitation: Determine if Srs2 physically interacts with recombination proteins like Rhp51.

• In vitro helicase assays: Test the ability of purified Srs2 to dismantle Rhp51 nucleoprotein filaments.

• Sister chromatid recombination assays: Measure recombination rates using heteroalleles (e.g., ade6-M26 and ade6-L469) in wild-type and mutant backgrounds .

What approaches should I use to study the differential roles of Srs2 and Rqh1 helicases in maintaining genome stability?

To investigate the distinct and overlapping functions of Srs2 and Rqh1 helicases:

Comparative Phenotypic Analysis:

• DNA damage sensitivity: Compare the sensitivity profiles of srs2Δ, rqh1Δ, and double mutants to different DNA damaging agents (UV, MMS, bleomycin) and replication inhibitors (HU) .

• Cell cycle analysis: Examine checkpoint responses and cell cycle progression after DNA damage using flow cytometry and microscopy .

• Recombination rates: Measure spontaneous and damage-induced recombination frequencies in different genetic backgrounds .

Key findings from previous studies show that:

• srs2Δ cells are moderately sensitive to UV radiation (~90% loss of viability at 200 J/m²), while rqh1Δ cells show much higher sensitivity .

• srs2Δ cells show mild sensitivity to hydroxyurea (HU) but don't lose significant viability during short-term exposure, unlike rqh1Δ cells .

• Both helicases contribute to resistance against alkylating agents (MMS) and radiomimetic drugs (bleomycin) .

Molecular Approaches:

• ChIP-seq: Compare the genomic binding profiles of Srs2 and Rqh1.

• Synthetic genetic arrays: Perform genome-wide screens to identify genes that interact differently with SRS2 and RQH1.

• Structure-function analysis: Create chimeric proteins or domain deletions to identify the regions responsible for unique functions.

• Proteomics: Identify differential protein interaction partners through quantitative proteomic analysis of immunoprecipitates .

How do I design experiments to resolve contradictory findings regarding Srs2 function in different yeast models?

When facing contradictory findings between S. pombe and S. cerevisiae Srs2 functions:

Experimental Design Strategies:

• Direct comparative studies: Perform identical experiments in both yeast species under standardized conditions.

• Heterologous expression: Express S. cerevisiae Srs2 in S. pombe srs2Δ strains (and vice versa) to test for functional complementation.

• Domain swap experiments: Create chimeric proteins containing domains from both species to identify regions responsible for species-specific functions.

Resolving Specific Contradictions:
For the contradiction regarding recombination suppression in srs2Δ rqh1Δ/sgs1Δ double mutants :

• Detailed recombination assays: Measure recombination at identical genomic loci in both species.

• Analyze different recombination pathways: Test involvement in synthesis-dependent strand annealing vs. double-strand break repair.

• Cell cycle-specific analyses: Determine if differences are cell cycle phase-dependent.

• Proteomic identification of interactors: Compare Srs2 interaction partners between species to identify differential regulatory mechanisms .

Controls and Validation:

• Multiple strain backgrounds: Test in different genetic backgrounds to ensure observations aren't strain-specific.

• Multiple methodological approaches: Confirm findings using independent techniques.

• Quantitative measurements: Use precise quantitative methods rather than qualitative assessments.

What are the optimal conditions for detecting post-translational modifications of Srs2?

For studying post-translational modifications (PTMs) of Srs2:

Sample Preparation:

• Rapid extraction: Harvest cells quickly and use TCA precipitation to preserve labile modifications.

• Phosphatase inhibitors: Include sodium orthovanadate, sodium fluoride, and β-glycerophosphate in all buffers when studying phosphorylation.

• Deubiquitinase inhibitors: Add N-ethylmaleimide when investigating ubiquitination.

• SUMO protease inhibitors: Include N-ethylmaleimide and iodoacetamide when studying SUMOylation.

Detection Methods:

• Phosphorylation-specific detection: Use Phos-tag™ SDS-PAGE for mobility shift detection or phospho-specific antibodies if available.

• Mass spectrometry approaches:

  • Enrichment of phosphopeptides using TiO₂ or IMAC

  • Multiple reaction monitoring (MRM) for targeted quantification

  • Parallel reaction monitoring (PRM) for improved specificity

Biological Induction:
Based on knowledge from related helicases, consider these conditions to induce PTMs:

• DNA damage: UV irradiation, MMS treatment, or bleomycin exposure

• Replication stress: Hydroxyurea treatment

• Cell cycle synchronization: To identify cell cycle-regulated modifications

How can I optimize ChIP-seq protocols specifically for Srs2 in fission yeast?

For optimizing ChIP-seq specifically for Srs2 in S. pombe:

Chromatin Preparation:

• Crosslinking optimization: Test various formaldehyde concentrations (0.5-3%) and times (5-20 minutes).

• Cell wall digestion: Use Zymolyase treatment optimized for S. pombe to improve antibody accessibility.

• Sonication parameters: Adjust sonication to achieve optimal chromatin fragmentation (200-500 bp), checking by agarose gel electrophoresis.

Immunoprecipitation:

• Antibody selection: Use ChIP-grade antibodies or epitope-tagged strains (HA-tagged Srs2 has been successfully used in S. pombe) .

• Pre-clearing: Include a pre-clearing step with protein A/G beads to reduce background.

• Washing stringency: Optimize salt concentrations in wash buffers to maintain specific interactions while reducing background.

Controls and Validation:

• Input controls: Include appropriate input chromatin controls.

• Negative controls: Use srs2Δ strains as negative controls.

• Positive controls: Include regions known to be enriched for recombination or DNA repair factors.

• Spike-in normalization: Consider using S. cerevisiae chromatin as a spike-in control for normalization.

Data Analysis Considerations:

• Peak calling algorithms: Test multiple algorithms (MACS2, HOMER) optimized for transcription factors or DNA repair proteins.

• Enrichment analysis: Compare with datasets for recombination proteins (Rhp51) to identify functional relationships.

• Integration with other genomic data: Correlate with replication origin mapping, DNA damage markers, or chromatin structure data.

What are the critical factors to consider when designing an in vitro system to study Srs2 helicase activity?

When designing an in vitro system to study Srs2 helicase activity:

Protein Purification:

• Expression system: Consider both E. coli and S. pombe expression systems.

• Purification tags: Compare His₆, GST, or MBP tags for optimal solubility and activity.

• Buffer optimization: Test various buffers, pH conditions, and salt concentrations to maintain enzyme stability and activity.

• Storage conditions: Determine optimal storage conditions (glycerol percentage, temperature) to preserve activity.

Activity Assay Design:

• Substrate design: Create DNA substrates that mimic biologically relevant structures:

  • Replication forks

  • D-loops

  • Holliday junctions

  • Rad51-coated ssDNA filaments

• Detection methods:

  • Fluorescence-based real-time assays with labeled oligonucleotides

  • Gel-based resolution of substrate and product

  • FRET-based systems for conformational changes

Reaction Conditions:

• Essential components: ATP (or ATP analogs), Mg²⁺, and appropriate buffers

• Temperature: S. pombe proteins typically show optimal activity at 30°C

• pH range: Test pH 7.0-8.5 for optimal activity

• Competing proteins: Include Rhp51 (Rad51 homolog) to test displacement activity

Functional Analysis:

• Kinetic parameters: Determine Km, Vmax, and kcat values

• Directionality: Establish 5'→3' or 3'→5' directionality

• ATP dependence: Compare activity with different nucleotides (ATP, dATP, non-hydrolyzable analogs)

• Structure-function relationships: Test truncated or mutated versions of Srs2

What are the emerging research areas involving Srs2 in S. pombe?

Emerging research areas involving Srs2 in S. pombe include:

Integration with DNA Repair Pathways:

• Synthetic lethality relationships: Further exploration of genetic interactions between srs2Δ and other DNA repair pathways beyond homologous recombination.

• Pathway choice regulation: Investigation of how Srs2 influences the choice between different DNA repair pathways (NHEJ vs. HR).

• Cell cycle-specific functions: Determination of how Srs2 functions change throughout the cell cycle.

Comparative Genomics and Evolution:

• Evolutionary conservation: Comparison of Srs2 function across different fungal species and potential human orthologs.

• Structural biology: Determination of the three-dimensional structure of S. pombe Srs2 and comparison with related helicases.

• Functional divergence: Investigation of how and why the functional relationship between Srs2 and homologous recombination differs between S. pombe and S. cerevisiae .

Technological Applications:

• Genome editing regulation: Exploration of Srs2's potential role in regulating homology-directed repair during CRISPR-Cas9 applications.

• Synthetic biology: Design of engineered Srs2 variants with modified activities for biotechnology applications.

• Quantitative chromatin proteomics: Development of improved methods for studying chromatin-bound proteins including Srs2 .

How can I integrate quantitative proteomics with functional genomics to better understand Srs2 roles?

To integrate quantitative proteomics with functional genomics for Srs2 research:

Experimental Integration Approaches:

• Chromatin proteomics: Apply quantitative proteomic analysis to chromatin fractions under different conditions (normal, DNA damage, replication stress) .

• Proximity labeling: Use BioID or APEX2 fusions with Srs2 to identify proteins in close proximity to Srs2 in living cells.

• Parallel genetic and proteomic screens: Combine synthetic genetic arrays with protein interaction mapping.

• ChIP-SICAP (Selective Isolation of Chromatin-Associated Proteins): Identify proteins co-occupying specific genomic regions with Srs2.

Data Integration Strategies:

• Multi-omics data integration: Combine proteomics data with transcriptomics, genomics, and metabolomics data.

• Network analysis: Build protein-protein interaction networks centered on Srs2.

• Machine learning approaches: Develop predictive models of Srs2 function based on integrated datasets.

• Visualization tools: Implement advanced visualization tools to represent complex multi-omics datasets.

Validation Methods:

• Targeted proteomics: Use parallel reaction monitoring (PRM) or multiple reaction monitoring (MRM) to validate key findings.

• CRISPR-based functional screens: Validate functional relationships using CRISPR technology in higher eukaryotes.

• Reconstitution experiments: Reconstitute key interactions or pathways in vitro to validate mechanism.

How do findings about S. pombe Srs2 relate to understanding human disease-associated helicases?

The connection between S. pombe Srs2 research and human disease-associated helicases:

Homology and Functional Conservation:
While S. pombe Srs2 lacks a direct ortholog in humans, it shares functional similarities with several human DNA helicases implicated in disease:

• BLM and WRN helicases: Defective in Bloom's and Werner's syndromes respectively, which cause cancer predisposition and premature aging .

• FANCJ/BACH1: Involved in Fanconi anemia and breast cancer susceptibility.

• RECQ5: Functions in suppressing inappropriate recombination, similar to Srs2.

Translational Research Applications:

• Disease modeling: Use S. pombe as a simplified system to understand basic mechanisms perturbed in human diseases.

• Drug screening: Develop high-throughput screens in yeast to identify compounds that modulate helicase activity.

• Synthetic lethality: Identify genetic interactions in yeast that could translate to potential therapeutic targets in human cancers with helicase deficiencies.

• Biomarker development: Identify patterns of genomic instability that could serve as biomarkers for helicase dysfunction in human cells.

Methodological Transfer:

• Assay development: Adapt biochemical and cellular assays developed for S. pombe Srs2 to study human helicases.

• Structural insights: Use structural information from yeast helicases to inform studies of human counterparts.

• Quantitative approaches: Apply quantitative proteomic techniques developed for yeast studies to human disease models .