SPAC2C4.05 Antibody

What is SPAC2C4.05 and what cellular function does the encoded protein serve?

SPAC2C4.05 is a gene in the fission yeast Schizosaccharomyces pombe that encodes Smd2p, a 13 kDa protein containing the Sm domain. Smd2p is one of the seven Sm proteins (Smb1p, Smd1p, Smd2p, Smd3p, Sme1p, Smf1p, and Smg1p) that form the core of the U1 small nuclear ribonucleoprotein (snRNP) complex, which is essential for pre-mRNA splicing .

The U1 snRNP in S. pombe contains a total of 16 proteins:

• 7 Sm core proteins (including Smd2p)

• 9 U1-specific proteins

This composition differs significantly from both budding yeast and mammalian U1 snRNPs:

• S. cerevisiae has 10 U1-specific proteins

• Mammals have only 3 U1-specific proteins

Smd2p plays a critical role in spliceosome formation and function, participating in the recognition and removal of introns from pre-mRNA. The protein is part of spliceosomal particles that sediment in the range of 12-60S in glycerol gradients .

What experimental applications is the SPAC2C4.05 antibody suitable for?

SPAC2C4.05 antibodies are typically validated for several key applications:

• Western blot (immunoblot): The primary application for detecting the Smd2p protein in cell lysates

• Immunoprecipitation (IP): For isolating Smd2p and associated complexes

• Immunofluorescence (IF): For visualizing cellular localization of Smd2p

• Mass spectrometry analysis: Following IP to identify interacting partners

For optimal results with any of these applications, antibody validation using appropriate controls is critical. The current gold standard involves comparing signal between parental and knockout cell lines .

When selecting a cell line for antibody testing, it's recommended to identify one with sufficient expression levels of Smd2p (typically 2.5 log units in RNA expression databases) to ensure detection by antibodies with binding affinities in the 1-50 nM range .

How should I validate the specificity of a SPAC2C4.05 antibody?

The consensus superior method for antibody validation is the parental versus knockout (KO) comparison approach . For SPAC2C4.05 antibody, implement the following validation protocol:

• Cell line selection: Identify cell lines with high expression of SPAC2C4.05 using proteomics databases (such as the Cancer Dependency Map Portal)

• Generate knockout lines: Use CRISPR/Cas9 to knockout the SPAC2C4.05 gene in the selected cell line

• Primary validation by Western blot:

  • Compare antibody signal between parental and KO lines

  • A specific antibody will show bands of the correct molecular weight (~13 kDa for Smd2p) in parental cells that are absent in KO cells

• Secondary validation:

  • Immunoprecipitation followed by Western blot

  • Immunofluorescence showing expected nuclear localization pattern

  • Mass spectrometry confirmation of pulled-down protein

According to comprehensive validation studies, the parental-KO comparison method is superior to other methods (such as peptide blocking or overexpression) and justifies the additional cost and effort . For commercially available antibodies, about 44% are successful in Western blot applications when tested rigorously .

What are the best fixation and permeabilization methods when using SPAC2C4.05 antibody for immunofluorescence?

For nuclear proteins like Smd2p that function as part of the spliceosome, the following protocol is recommended:

For mammalian cells:

• Fix with 4% paraformaldehyde for 10-15 minutes at room temperature

• Permeabilize with 0.5% Triton X-100 for 5-10 minutes (more stringent permeabilization is often needed for nuclear proteins)

• Block with 5% BSA or normal serum in PBS for 1 hour

For yeast cells (especially important for S. pombe):

• Digest cell wall with zymolyase (1-2 mg/ml) or lyticase in sorbitol buffer

• Fix with 3.7% formaldehyde

• Apply more vigorous permeabilization (1% Triton X-100) due to remaining cell wall components

• Mount using antifade reagent with DAPI to visualize nuclei

For studying U1 snRNP components specifically, research groups have successfully used TAP-tagged versions of the proteins to visualize localization patterns in S. pombe . This approach may provide more reliable results than antibody-based detection in yeast cells.

How can I use SPAC2C4.05 antibody to study the assembly of the U1 snRNP complex in S. pombe?

Based on established methodologies , a comprehensive approach to studying U1 snRNP assembly using SPAC2C4.05 antibody includes:

• Glycerol gradient sedimentation analysis:

  • Separate cell extracts on 10-30% glycerol gradients containing 150 mM sodium chloride

  • Collect fractions and analyze by immunoblotting with SPAC2C4.05 antibody

  • Complete U1 snRNP complexes typically sediment in the 30-60S range

• Immunoprecipitation with dual verification:

  • Perform IP with SPAC2C4.05 antibody

  • Analyze protein components by immunoblotting

  • Extract RNA from immunoprecipitated material

  • Verify U1 snRNA presence by Northern blotting using labeled oligonucleotides complementary to U1 snRNA

• Co-immunoprecipitation studies:

  • Create strains expressing epitope-tagged versions of multiple U1 snRNP components

  • Use SPAC2C4.05 antibody for IP and detect co-precipitating proteins

  • Alternatively, perform reverse IPs with antibodies against other components

  • This approach successfully detected interactions between different tagged versions of U1-70K (U1-70K-HA and U1-70K-Myc), suggesting multimerization of U1 particles

• Salt sensitivity analysis:

  • Perform IPs under increasing salt concentrations to assess complex stability

  • Smd2p associations with U1-70K and U1H remain stable at up to 500 mM sodium chloride

Table: U1 snRNP components in S. pombe, with homologs in budding yeast and humans. Adapted from search result .

What are the recommended controls when using SPAC2C4.05 antibody for quantitative proteomics studies?

For rigorous quantitative proteomics studies involving SPAC2C4.05 antibody immunoprecipitation:

• Negative controls:

  • CRISPR knockout or knockdown samples of SPAC2C4.05

  • IgG isotype control antibody IP processed identically

  • IP from a cell type not expressing the target (if available)

• Specificity controls:

  • Competitive peptide blocking using the immunizing peptide

  • Comparison of IPs with multiple antibodies recognizing different epitopes of Smd2p

• Validation of interactions:

  • Reciprocal IPs with antibodies against putative interacting partners

  • For U1 snRNP studies, validate by detecting specific U1 snRNA in the immunoprecipitated material using Northern blotting

• Technical controls for quantitative MS:

  • Include spike-in standards for normalization

  • For isotope labeling experiments (SILAC, TMT), perform label-swap replicates

  • Analyze inputs at different dilutions to establish linearity

• Computational filtering:

  • Apply stringent statistical thresholds (typically p < 0.01 and fold-change > 2)

  • Filter against common contaminant databases

  • Compare against previous U1 snRNP proteomics studies in S. pombe

When analyzing the proteomic data, consider that the U1 snRNP in S. pombe contains species-specific proteins (U1H, U1J, and U1L) that may not have direct homologs in other organisms but play critical roles in intron recognition .

How do post-translational modifications affect SPAC2C4.05 antibody recognition of Smd2p?

Post-translational modifications (PTMs) can significantly impact antibody recognition of Smd2p:

• Common PTMs affecting Sm proteins:

  • Symmetrical dimethylation of arginine residues

  • Phosphorylation of serine/threonine residues

  • Ubiquitination at lysine residues

• Epitope accessibility issues:

  • Antibodies raised against linear epitopes may fail to recognize Smd2p if the epitope is modified

  • Conformation-specific antibodies may be affected by modifications that alter protein structure

• Strategies to address PTM interference:

  • Use multiple antibodies recognizing different epitopes

  • Employ phosphatase treatment before immunoblotting to remove phosphorylation

  • Apply targeted mass spectrometry to characterize PTMs of Smd2p in your experimental system

• Documentation review:

  • Check antibody documentation for information about the immunogen sequence

  • Some manufacturers specify whether an antibody recognizes "unmodified" forms of the target

  • Review available literature on modification sites in Smd2p

For comprehensive studies of Smd2p and its modifications, consider combining immunoprecipitation with mass spectrometry to identify and map PTMs, which may provide insight into the regulation of U1 snRNP assembly and function.

How can I use cross-linking approaches with SPAC2C4.05 antibody to capture dynamic interactions?

To capture dynamic protein-protein and protein-RNA interactions involving Smd2p:

• Chemical cross-linking strategies:

  • Formaldehyde (1-3%) for brief periods (5-10 minutes) for general protein-protein cross-linking

  • DSP (dithiobis[succinimidyl propionate]) for reversible cross-linking (reducible with DTT)

  • UV cross-linking (254 nm) for direct protein-RNA interactions

• CLIP-seq protocol (Cross-linking immunoprecipitation followed by sequencing):

  • UV cross-link cells to capture direct protein-RNA interactions

  • Lyse cells and perform immunoprecipitation with SPAC2C4.05 antibody

  • Partially digest RNA, radiolabel, and visualize by autoradiography

  • Extract and sequence bound RNA fragments

• BioID or APEX2 proximity labeling:

  • Generate fusion proteins of Smd2p with BioID or APEX2

  • Induce biotinylation of proximal proteins

  • Isolate biotinylated proteins using streptavidin

  • Identify by mass spectrometry

• Sequential immunoprecipitation:

  • First IP with SPAC2C4.05 antibody

  • Elute under mild conditions

  • Second IP with antibody against suspected interacting partner

  • This stringent approach can validate direct interactions

For analyzing U1 snRNP dynamics specifically, the glycerol gradient sedimentation approach revealed that U1 particles might exist as aggregates sedimenting in the 30-60S range, which can partially fall apart during purification to monomeric U1 snRNP particles sedimenting around 20S . Cross-linking prior to purification can help preserve these native interactions.

How can SPAC2C4.05 antibody be used to investigate the relationship between splicing and other cellular processes?

The U1 snRNP plays roles beyond canonical splicing, and SPAC2C4.05 antibody can help investigate these connections:

• Co-immunoprecipitation coupled with mass spectrometry:

  • Immunoprecipitate Smd2p complexes from cells under different conditions

  • Identify co-purifying proteins by mass spectrometry

  • Look for components of other cellular machineries (transcription, export, translation)

  • Research has revealed connections between splicing factors and translation factors (e.g., relationships between Aim29 and Zpr1, involved in eEF1A folding)

• Functional genomics approaches:

  • Combine SPAC2C4.05 antibody ChIP with RNA-seq or proteomics

  • Map Smd2p binding sites across the genome

  • Correlate with splicing patterns and other cellular processes

  • Investigate changes in response to stress conditions

• Subcellular localization:

  • Use immunofluorescence with SPAC2C4.05 antibody alongside markers for:

    • P-bodies (RNA degradation)

    • Stress granules (translation inhibition)

    • Nuclear speckles (splicing factories)

  • Track localization changes in response to treatments affecting different cellular processes

• Analysis of physical interactions:

  • According to research, some S. pombe-specific U1 snRNP components (U1H, U1J, U1L) may be involved in intron recognition

  • These proteins can be co-immunoprecipitated with Smd2p antibody to study their role in connecting splicing to other processes

These approaches have revealed, for example, that the essential Aim29 gene (SPAC2C4.04c in S. pombe) functions in a pathway with Zpr1 to mediate proper folding of translation elongation factor eEF1A, demonstrating connections between RNA processing and translation machinery .

What are the key considerations when using SPAC2C4.05 antibody in cross-species studies?

When applying SPAC2C4.05 antibody across different species:

• Sequence homology analysis:

  • Sm proteins are highly conserved across eukaryotes

  • Smd2p shows high sequence conservation between species:

    • S. pombe Smd2p shares significant homology with human SmD2

    • Compare the antibody epitope sequence specifically across species

• Species validation hierarchy:

  • Primary validation in S. pombe as the native target

  • Secondary validation in S. cerevisiae (high homology)

  • Tertiary validation in mammalian cells (may require higher antibody concentrations)

• Specialized protocols for different model systems:

  • For yeast: Cell wall removal is critical (enzymatic digestion with zymolyase)

  • For mammalian cells: Standard fixation and permeabilization

  • For tissue sections: Antigen retrieval may be necessary

• Control experiments:

  • Overexpression of S. pombe Smd2p in heterologous systems

  • CRISPR knockout of the homologous gene

  • Side-by-side comparison with species-specific antibodies

How can I optimize Western blot conditions for SPAC2C4.05 antibody?

For optimal Western blot results with SPAC2C4.05 antibody:

• Sample preparation:

  • For yeast cells: Efficient lysis is critical

    • Use glass bead disruption in the presence of protease inhibitors

    • Include phosphatase inhibitors to preserve phosphorylation states

  • For mammalian cells: Standard RIPA or NP-40 lysis buffers

  • Load 20-50 μg of total protein per lane initially, then optimize

• Gel electrophoresis parameters:

  • Use higher percentage gels (15-18%) for small proteins like Smd2p (~13 kDa)

  • Consider gradient gels (4-20%) when analyzing complexes

  • Include molecular weight markers that cover low range (5-25 kDa)

• Transfer conditions:

  • For small proteins:

    • Use PVDF membrane with 0.2 μm pore size (not 0.45 μm)

    • Transfer at lower voltage (25V) for longer time (2h) or use semi-dry transfer

    • Include methanol (10-20%) in transfer buffer

• Antibody incubation:

  • Primary antibody:

    • Starting dilution: 1:1000, then optimize

    • Incubate overnight at 4°C in 5% BSA or milk

  • Secondary antibody:

    • Anti-rabbit or anti-mouse HRP conjugates (depending on primary)

    • Optimize dilution (typically 1:5000-1:10000)

    • Consider using secondary antibodies with reduced cross-reactivity to other species

• Detection:

  • Use enhanced chemiluminescence (ECL) substrates

  • For weak signals, consider super-signal substrates

  • Alternative: Fluorescent secondary antibodies with infrared imaging systems

For particularly challenging samples, consider enriching the target protein by immunoprecipitation prior to Western blotting to increase sensitivity.

What are the critical factors affecting SPAC2C4.05 antibody immunoprecipitation efficiency?

To maximize immunoprecipitation efficiency with SPAC2C4.05 antibody:

• Lysis conditions:

  • Use non-denaturing buffers to preserve protein-protein interactions:

    • Standard IP buffer: 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 1% NP-40

    • For nuclear proteins like Smd2p, include 0.1-0.5% NP-40 and sonicate briefly

  • Add protease inhibitors freshly before lysis

  • For RNA-associated proteins, add RNase inhibitors (40 U/mL)

• Antibody-to-sample ratio optimization:

  • Start with 2-5 μg antibody per 500 μg protein lysate

  • Perform titration experiments to determine the optimal ratio

  • Pre-clear lysates with protein A/G beads to reduce background

• Binding conditions:

  • Incubate antibody with lysate overnight at 4°C under gentle rotation

  • For weaker interactions, reduce salt concentration to 100 mM

  • For RNA-dependent interactions, consider cross-linking before lysis

• Bead selection and handling:

  • Match beads to antibody isotype (Protein A for rabbit, Protein G for mouse)

  • Magnetic beads offer gentler handling than agarose

  • Optimize wash stringency (3-5 washes with decreasing salt concentration)

• Elution strategies:

  • For Western blot: Boil in SDS sample buffer

  • For mass spectrometry: Use mild elution (peptide competition or low pH)

  • For RNA analysis: TRIzol extraction directly from beads

Based on research with U1 snRNP components, the fission yeast complexes can be efficiently purified using tandem affinity purification (TAP) tags, which might be more effective than antibody-based methods in some cases .

What quality control metrics should I apply when evaluating SPAC2C4.05 antibody performance?

Apply these critical quality control metrics when evaluating SPAC2C4.05 antibody:

• Specificity metrics:

  • Single band of correct molecular weight (~13 kDa for Smd2p) in Western blot

  • Absence of signal in knockout/knockdown controls

  • Correct subcellular localization pattern (nuclear for Smd2p)

  • Enrichment of known interacting partners in IP-MS

• Sensitivity assessment:

  • Determine limit of detection using dilution series

  • Compare signal-to-noise ratio across different conditions

  • Assess consistency across biological replicates (CV < 20%)

• Reproducibility measurements:

  • Intra-assay variation (multiple technical replicates)

  • Inter-assay variation (experiments performed on different days)

  • Lot-to-lot consistency if using commercial antibodies

• Validation across applications:

  • Performance correlation between Western blot, IP, and IF

  • According to comprehensive studies, only 44% of antibodies recommended for Western blot are successful when rigorously tested

  • For IP applications, success rates are typically lower at around 58%

• Functional validation:

  • For Smd2p specifically, verify that immunoprecipitated material contains U1 snRNA

  • Confirm co-immunoprecipitation of known U1 snRNP components

  • Validate that antibody can detect changes in expression levels when experimentally induced

Research indicates that the gold standard method of comparing parental and knockout cell lines provides the most reliable validation of antibody specificity , and this approach should be implemented whenever possible.

How should I approach experimental design when using SPAC2C4.05 antibody to study stress responses in splicing?

For investigating stress-induced changes in splicing using SPAC2C4.05 antibody:

• Experimental design considerations:

  • Include appropriate time course (early and late responses)

  • Apply physiologically relevant stress conditions:

    • Heat shock (temperature shift to 37-42°C)

    • Oxidative stress (0.5-1 mM H₂O₂)

    • Nutrient deprivation (carbon or nitrogen starvation)

  • Use multiple stress types to distinguish general from stress-specific responses

• Controls and normalization:

  • Include non-stressed controls at each time point

  • Use multiple housekeeping proteins for normalization

  • Consider spike-in controls for quantitative proteomics

• Multiparametric analysis:

  • Monitor Smd2p levels by Western blot

  • Track subcellular localization by immunofluorescence

  • Analyze complex formation by immunoprecipitation followed by mass spectrometry

  • Assess RNA association changes by CLIP-seq or RNA-IP

• Molecular mechanisms assessment:

  • Investigate post-translational modifications of Smd2p under stress

  • Examine changes in interactions with other U1 snRNP components

  • Analyze sedimentation patterns of U1 snRNP complexes in glycerol gradients

• Functional validation:

  • Correlate molecular changes with splicing efficiency (RT-PCR of known introns)

  • Compare results across stress conditions to identify common mechanisms

  • Validate findings in knockout/knockdown systems

Research with U1 snRNP components has shown that stress conditions can affect both the composition and the activity of splicing complexes. For example, heat shock can lead to changes in protein-protein interactions within the spliceosome, potentially through stress-induced post-translational modifications.

How can SPAC2C4.05 antibody be combined with emerging technologies for single-cell analysis?

Integrating SPAC2C4.05 antibody with single-cell technologies:

• Single-cell proteomics approaches:

  • Antibody-based single-cell Western blot

  • Mass cytometry (CyTOF) with metal-conjugated antibodies

  • Microfluidic antibody capture for protein quantification

• Spatial analysis in tissues:

  • Multiplex immunofluorescence with SPAC2C4.05 antibody

  • Imaging mass cytometry for tissue sections

  • Spatial transcriptomics combined with protein detection

• Single-cell multi-omics integration:

  • CITE-seq approach: Use oligonucleotide-labeled SPAC2C4.05 antibody

  • Similar to TotalSeq™ technology shown in search result

  • Simultaneously measure protein levels and transcriptome in single cells

  • Correlate Smd2p protein levels with splicing patterns

• High-throughput screening applications:

  • Miniaturized immunoassays in 1536-well format

  • Cell painting with SPAC2C4.05 antibody as one parameter

  • Droplet microfluidics with antibody readouts

For effective implementation, the SPAC2C4.05 antibody must meet stringent specificity and sensitivity requirements. Consider adapting validation approaches from the SLISY (Sequencing-Linked ImmunoSorbent assaY) methodology, which can assess binding specificity of millions of clones in a single experiment .

What strategies can improve reproducibility when working with SPAC2C4.05 antibody across different laboratories?

To enhance reproducibility of SPAC2C4.05 antibody experiments:

• Standardized validation protocol:

  • Implement the parental vs. knockout validation approach

  • Document antibody performance across multiple applications

  • Share validation data in public repositories

• Detailed antibody reporting:

  • Use Research Resource Identifiers (RRIDs) for antibodies

  • Document lot numbers, concentration, and storage conditions

  • Specify exact epitope when known

• Protocol standardization:

  • Develop and share detailed standard operating procedures (SOPs)

  • Include all buffer compositions and incubation times

  • Specify equipment settings (microscope parameters, gel running conditions)

• Reference samples exchange:

  • Create standard positive control samples

  • Distribute reference cell lysates for calibration

  • Consider developing a recombinant protein standard

• Collaborative validation networks:

  • Participate in multi-laboratory validation studies

  • Use consistent validation metrics across sites

  • Share raw data for meta-analysis

According to comprehensive antibody validation studies, approximately 20-30% of protein studies may use ineffective antibodies, indicating a substantial need for independent assessment of commercial antibodies . For SPAC2C4.05 specifically, a centralized validation effort could help establish reliable reagents for the research community.

How can computational approaches enhance the interpretation of SPAC2C4.05 antibody-based experiments?

Advanced computational methods can maximize insights from SPAC2C4.05 antibody experiments:

• Image analysis for immunofluorescence:

  • Machine learning for automated segmentation

  • Quantitative colocalization with other spliceosome components

  • Tracking dynamic changes in localization over time

• Network analysis for interaction studies:

  • Integrate IP-MS data with existing protein interaction databases

  • Generate spliceosome interaction networks

  • Identify functional modules within complexes

  • Map interactions to structural models of the U1 snRNP

• Multi-omics data integration:

  • Correlate Smd2p binding (ChIP-seq) with:

    • Transcriptome changes (RNA-seq)

    • Splicing patterns (splice junction analysis)

    • Epigenetic modifications (e.g., histone marks)

• Structural biology integration:

  • Map antibody epitopes onto protein structures

  • Use AlphaFold2 predictions for structural analysis

  • Molecular docking to predict antibody-antigen interactions (similar to approach in )

• Predictive modeling:

  • Develop machine learning models to predict antibody specificity

  • Create algorithms to identify optimal epitopes for new antibody development

  • Model the impact of post-translational modifications on antibody binding

These computational approaches not only enhance data interpretation but can guide experimental design and antibody selection. For example, epitope mapping combined with structural analysis can help identify antibodies likely to recognize native versus denatured forms of Smd2p.

What are the emerging applications of SPAC2C4.05 antibody in disease research?

While SPAC2C4.05 encodes an essential splicing factor in yeast, studying its homologs has implications for human disease research:

• Neurological disorders:

  • Human SmD2 (homolog of Smd2p) is involved in splicing regulation

  • Mis-splicing contributes to neurodegenerative diseases

  • SPAC2C4.05 antibody tools in model organisms can elucidate conserved mechanisms

• Cancer biology:

  • Splicing factor mutations are common in various cancers

  • Understanding fundamental splicing mechanisms using yeast models

  • Compare splicing complex composition between normal and cancer cells

• Genetic diseases with splicing defects:

  • Many genetic disorders involve splicing mutations

  • Study model splicing mutations in yeast

  • Translate findings to human cell systems using homologous antibodies

• Drug discovery applications:

  • Screen for compounds that modulate spliceosome function

  • Use antibody-based assays to measure effects on splicing complexes

  • Validate hits in disease-relevant models

• Biomarker development:

  • Investigate splicing factors as potential disease biomarkers

  • Develop quantitative assays for splicing factors and their modifications

  • Correlate with disease progression or treatment response