SPBC13E7.11 Antibody

What is SPBC13E7.11 and what are its functional roles in Schizosaccharomyces pombe?

SPBC13E7.11 is a gene in Schizosaccharomyces pombe (fission yeast) annotated as prf1 (or rtf1), encoding a chromatin-associated protein that plays critical roles in epigenetic regulation. The protein functions as a component of the Paf1 complex (Paf1C) and is involved in:

• Histone modifications, particularly facilitating the ubiquitination of histone H2B at lysine 119 (H2Bub1)

• Preventing small RNA-mediated epigenetic gene silencing, thus conferring epigenetic robustness

• Direct binding to phosphorylated Spt5, a component of the transcription elongation factor P-TEFb complex

• Maintaining a feedback loop that stabilizes H2Bub1 levels during transcriptional elongation

Interestingly, there are some inconsistencies in annotation, as SPBC13E7.11 has also been predicted to function as a mitochondrial rhomboid protease in some databases .

What applications are SPBC13E7.11 antibodies most commonly used for?

Based on available research protocols, SPBC13E7.11 antibodies are primarily utilized for:

• Immunoprecipitation: Isolation of Prf1-associated chromatin regions for downstream analysis

• Western Blotting: Detection of Prf1 protein levels in yeast lysates

• ChIP-Seq: Mapping Prf1 binding sites across the genome to study transcriptional regulation

• ELISA: Quantitative detection of the protein in various experimental setups

For Western blot applications, researchers typically use standardized protocols with optimized dilutions determined by each laboratory based on their specific experimental conditions .

How should I validate the specificity of a SPBC13E7.11 antibody?

Proper validation requires multiple approaches:

• Genetic controls: Use of prf1 deletion mutants (prf1Δ) as negative controls

• Western blot analysis: Verification of a single band of appropriate molecular weight (~40-50 kDa for Prf1)

• Competitive binding assays: Pre-incubation with recombinant Prf1 protein should abolish signal

• Cross-reactivity testing: Ensure the antibody doesn't recognize related proteins like other Paf1 complex components (Paf1, Leo1, Cdc73, Tpr1)

• Correlation with known phenotypes: Antibody detection should correlate with expected cellular phenotypes in wild-type vs. mutant strains

How does Prf1/Rtf1 (SPBC13E7.11) contribute to epigenetic regulation through the Paf1 complex?

Prf1/Rtf1, as a component of the Paf1 complex, plays a sophisticated role in epigenetic regulation:

• Protective function: The Paf1 complex (including Prf1) prevents siRNA-mediated formation of heterochromatin at coding genes, thus protecting the genome from illegitimate repression

• Mechanism of action: When Paf1C function is impaired through mutations in components like Prf1, siRNAs can trigger the formation of highly stable heterochromatin

• Epigenetic switching: In prf1 mutants, primary siRNAs can trigger production of secondary siRNAs at target loci, leading to a self-reinforcing silencing loop

• Relationship with RNAi machinery: Maintenance of heterochromatin in prf1 mutants remains dependent on canonical RNAi factors, indicating a complex interplay between Paf1C and the RNAi pathway

The research shows that mutations in Paf1C components (including Prf1) enable both trans- and cis-acting siRNAs to direct methylation of H3K9, a key step in heterochromatin formation .

What technical considerations are important when using SPBC13E7.11 antibody for ChIP-seq experiments?

Successful ChIP-seq with SPBC13E7.11 antibody requires:

• Crosslinking optimization: Since Prf1 interacts with both chromatin and elongation factors, standard 1% formaldehyde fixation may need adjustment to capture all interactions

• Sonication parameters: Chromatin should be sheared to 200-500bp fragments, with careful optimization to maintain protein-DNA complexes

• Antibody selection: Use ChIP-grade antibodies specifically validated for immunoprecipitation applications

• Controls: Include:

  • Input DNA (non-immunoprecipitated)

  • IgG controls

  • Positive controls (antibodies against known interacting proteins like Spt5)

  • Biological replicates to ensure reproducibility

• Data analysis considerations:

  • Expected binding patterns around gene bodies, particularly at transcriptionally active regions

  • Co-localization with H2Bub1 marks

  • Correlation with RNA Polymerase II occupancy

How can SPBC13E7.11 antibody be used to investigate the relationship between the Paf1 complex and heterochromatin assembly?

This advanced application requires careful experimental design:

• ChIP-seq comparative analysis: Compare Prf1 binding profiles in wild-type cells versus cells with mutations in heterochromatin factors (e.g., clr4Δ, swi6Δ, chp2Δ)

• Sequential ChIP (re-ChIP): To determine co-occupancy of Prf1 with other factors:

  • First immunoprecipitate with SPBC13E7.11 antibody

  • Then perform a second immunoprecipitation with antibodies against heterochromatin marks (H3K9me) or RNAi factors

• Integrative analysis with siRNA profiling:

  • Compare Prf1 binding sites with loci that produce siRNAs in Paf1C mutants

  • Correlate with H3K9 methylation data to identify regions protected from heterochromatin formation

• Experimental system using reporter genes:

  • Use the ade6+ reporter system described in the literature

  • Monitor the formation of heterochromatin in the presence/absence of functional Prf1

  • Track silencing phenotypes through color assays (red/white colonies)

What is the relationship between SPBC13E7.11 (Prf1) and small RNA-mediated epigenetic gene silencing?

Research demonstrates a complex relationship:

The data reveals that:

• In wild-type cells, Prf1 (as part of Paf1C) prevents siRNA-directed heterochromatin formation at coding genes

• When Prf1 function is compromised, siRNAs can trigger formation of stable heterochromatin with the following characteristics:

  • Highly efficient silencing (approximately 70% in meiosis)

  • Production of abundant secondary siRNAs

  • Formation of bona fide heterochromatin dependent on histone deacetylases, methyltransferases, and HP1 proteins

• The silencing is dependent on continued RNAi activity, indicating that Prf1 normally functions as a suppressor of RNAi-mediated heterochromatin formation at coding genes

How do mutations in SPBC13E7.11 affect gene silencing through epigenetic mechanisms?

Specific mutations in SPBC13E7.11 (Prf1) have remarkable effects on epigenetic silencing:

• The prf1 point mutation identified in genetic screens enables siRNAs to induce gene silencing in trans

• Different Paf1C mutants (including Prf1) show varying efficiencies of heterochromatin establishment:

  • prf1 mutants allow highly stable inheritance of the silenced state

  • The stability of silencing varies between different mutant alleles

• De novo formation of heterochromatin in Prf1 mutants is most efficient during meiosis (70% efficiency)

• Mechanistically, mutations in Prf1 allow:

  • Primary siRNAs to trigger the production of highly abundant secondary siRNAs

  • Establishment of H3K9 methylation at target loci

  • Recruitment of silencing complexes (SHREC, CLRC) and heterochromatin proteins (Swi6, Chp2)

These findings highlight how mutations in a single component of the transcription machinery can dramatically alter the epigenetic landscape of the cell.

What are the optimal conditions for using SPBC13E7.11 antibody in Western blot applications?

For optimal Western blot results with SPBC13E7.11 antibody:

• Sample preparation:

  • Extract proteins from S. pombe using either TCA precipitation or mechanical disruption

  • Include protease inhibitors and phosphatase inhibitors if studying phosphorylation status

  • Denature samples in standard SDS-PAGE loading buffer at 95°C for 5 minutes

• Gel electrophoresis and transfer:

  • Use 10-12% SDS-PAGE gels for optimal resolution

  • Transfer to PVDF or nitrocellulose membranes at 100V for 1 hour or 30V overnight

• Blocking and antibody incubation:

  • Block with 5% non-fat dry milk or BSA in TBST

  • Primary antibody dilution: Optimal dilutions should be determined by each laboratory

  • Incubate overnight at 4°C with gentle agitation

  • Secondary antibody: HRP-conjugated anti-species IgG at 1:5000-1:10000 dilution

• Controls:

  • Positive control: Wild-type S. pombe extract

  • Negative control: prf1Δ mutant extract

  • Loading control: Anti-actin antibody

• Detection:

  • Use enhanced chemiluminescence (ECL) detection

  • Expected molecular weight of Prf1: ~40-50 kDa

How can SPBC13E7.11 antibody be used to investigate protein-protein interactions within the Paf1 complex?

To study interactions within the Paf1 complex using SPBC13E7.11 antibody:

• Co-immunoprecipitation (Co-IP):

  • Crosslink cells with formaldehyde (1%) to preserve protein complexes

  • Lyse cells under non-denaturing conditions

  • Immunoprecipitate with SPBC13E7.11 antibody

  • Analyze co-precipitated proteins (Paf1, Leo1, Cdc73, Tpr1) by Western blot

• Proximity ligation assay (PLA):

  • Use SPBC13E7.11 antibody in combination with antibodies against other Paf1C components

  • Detect protein-protein interactions in situ with fluorescence microscopy

• ChIP-reChIP:

  • First ChIP with SPBC13E7.11 antibody

  • Second ChIP with antibodies against other Paf1C components

  • Analyze co-occupancy at genomic loci

• Analysis of protein complex integrity in mutants:

  • Compare Co-IP results between wild-type and cells with mutations in Paf1C components

  • Determine if specific mutations disrupt the interaction network

This approach can reveal how the Prf1 protein functions within the larger Paf1 complex and how this relates to its role in preventing RNAi-directed heterochromatin formation.

What approaches can resolve the discrepancy between SPBC13E7.11 being annotated both as a chromatin protein (Prf1) and a potential mitochondrial protease?

To resolve this annotation discrepancy, researchers should employ:

• Subcellular fractionation:

  • Separate nuclear, cytoplasmic, and mitochondrial fractions

  • Use Western blot with SPBC13E7.11 antibody to determine protein localization

  • Include controls for each fraction (histone H3 for nuclear, tubulin for cytoplasmic, cytochrome c for mitochondrial)

• Immunofluorescence microscopy:

  • Use SPBC13E7.11 antibody for immunostaining

  • Co-stain with mitochondrial markers (MitoTracker) and nuclear markers (DAPI)

  • Analyze colocalization patterns

• Protease activity assays:

  • Immunoprecipitate Prf1 using SPBC13E7.11 antibody

  • Test for protease activity using appropriate substrates

  • Include known proteases as positive controls

• Bioinformatic analysis:

  • Reexamine sequence features for mitochondrial targeting signals

  • Compare conserved domains with known chromatin factors and proteases

  • Analyze evolutionary conservation patterns across yeast species

• CRISPR-mediated tagging:

  • Generate fluorescently tagged versions of SPBC13E7.11

  • Perform live-cell imaging to determine localization

  • Correlate with functional studies

This comprehensive approach would determine whether SPBC13E7.11 has dual functions or if one annotation is incorrect.

What are common issues when using SPBC13E7.11 antibody and how can they be resolved?

For all applications, proper controls are essential to distinguish genuine signals from artifacts .

How can I assess if my SPBC13E7.11 antibody is detecting both phosphorylated and non-phosphorylated forms of the protein?

To determine if your antibody detects both forms:

• Phosphatase treatment experiment:

  • Split your sample into two portions

  • Treat one portion with lambda phosphatase

  • Compare band patterns by Western blot

  • Shift in molecular weight indicates detection of phosphorylated forms

• Phos-tag™ SDS-PAGE:

  • Use Phos-tag acrylamide gels to separate phosphorylated from non-phosphorylated proteins

  • Run Western blot with SPBC13E7.11 antibody

  • Compare with phospho-specific controls

• Two-dimensional gel electrophoresis:

  • Separate proteins by isoelectric point and molecular weight

  • Detect with SPBC13E7.11 antibody

  • Identify phosphorylated species as spots shifted toward acidic pH

• Immunoprecipitation followed by phospho-specific staining:

  • Immunoprecipitate with SPBC13E7.11 antibody

  • Probe with general phospho-specific antibodies (anti-phospho-Ser/Thr/Tyr)

  • Alternatively, analyze by mass spectrometry for phosphorylation sites