SPBC119.12 Antibody

What is SPBC119.12 and what is its primary function in fission yeast?

SPBC119.12 encodes the Rbm10 protein in fission yeast (Schizosaccharomyces pombe), which functions as a splicing factor with critical roles in heterochromatin assembly. Unlike what might be expected from a splicing factor, deletion of the rbm10+ gene has minimal effects on global splicing patterns but significantly disrupts heterochromatin silencing and histone H3 lysine 9 methylation (H3K9me) . The protein serves as a platform that recruits chromatin-modifying complexes to heterochromatic regions, particularly the Clr6 histone deacetylase (HDAC) complex and various chromatin remodelers .

How does Rbm10 contribute to heterochromatin formation?

Rbm10 facilitates heterochromatin assembly through multiple protein-protein interactions. Most significantly, it associates with components of the Clr6 HDAC complexes (both Class I and II), which are essential for heterochromatin silencing . Rbm10 interacts with at least five members of the Clr6 I complex and Alp13 from the Clr6 II complex, as demonstrated through mass spectrometry analysis . The proposed mechanism involves Rbm10 binding to nascent heterochromatic transcripts and serving as a recruitment platform for the Clr6 complex and chromatin remodelers, which then promote heterochromatin assembly .

What is the relationship between fission yeast Rbm10 and human RBM10?

Fission yeast Rbm10 is a homologue of human RBM10, which has been linked to TARP syndrome . The functional conservation extends to their interaction patterns with splicing factors, suggesting evolutionary conservation of certain molecular functions . While human RBM10 is primarily known for its role in alternative splicing regulation, the fission yeast homolog reveals additional functions in chromatin organization that may have implications for understanding human RBM10's complete functional repertoire.

What are the optimal conditions for Chromatin Immunoprecipitation (ChIP) using SPBC119.12 antibodies?

For effective ChIP using SPBC119.12 antibodies, researchers should follow these methodological guidelines:

• Cross-link 50 ml of log-phase yeast culture with 37% formaldehyde for 30 minutes .

• Collect cells and subject them to sonication using an Ultrasonic Processor to fragment chromatin .

• For immunoprecipitation, use 1 μl of H3K9me antibody (Abcam ab1220) when studying heterochromatin regions affected by Rbm10 .

• Purify immunoprecipitated DNA using a PCR clean-up column (Qiagen) and analyze by PCR using appropriate primers .

• Include at least two to three independent biological repeats to ensure reproducibility .

This protocol has been successfully employed to detect changes in heterochromatin formation in rbm10Δ strains compared to wild-type.

How can co-immunoprecipitation be optimized for studying SPBC119.12 protein interactions?

For co-immunoprecipitation studies involving SPBC119.12/Rbm10:

• Create cells expressing both Rbm10-TAP and the potential interacting partner tagged with GFP, preferably expressed under their endogenous promoters to avoid artifacts from overexpression .

• Collect cells and resuspend in lysis buffer containing protease inhibitors before lysis by bead beating .

• Incubate lysates with IgG sepharose (GE Healthcare) at 4°C for 2 hours .

• Wash with lysis buffer three times and elute proteins in SDS loading buffer .

• Analyze eluates by Western blotting using appropriate antibodies (e.g., commercial anti-GFP antibody from Abcam) .

This method successfully demonstrated the interaction between Rbm10 and Alp13, validating results obtained from TAP-tag purification and mass spectrometry .

What experimental controls are essential when using SPBC119.12 antibodies?

When working with SPBC119.12 antibodies, the following controls are critical:

• Negative controls: Include samples from rbm10Δ strains to confirm antibody specificity .

• Input controls: Always process a portion of the pre-immunoprecipitation sample to normalize ChIP or IP data.

• Non-specific antibody controls: Use isotype-matched control antibodies to assess background binding.

• Positive controls: Include immunoprecipitation of known Rbm10 interacting partners like Prw1 or Alp13 .

• Expression controls: When using tagged versions of Rbm10, verify that tagging does not disrupt protein function by complementation assays.

How can tandem affinity purification (TAP) be used to identify novel SPBC119.12 interacting partners?

TAP combined with mass spectrometry offers powerful insights into the Rbm10 interactome:

• Induce cells carrying pREP1-FLAG-HA-rbm10 for 24 hours in minimal media without thiamine .

• Lyse cells in buffer containing Benzonase using bead beating .

• Perform sequential purification:

  • First with Protein G beads coated with anti-FLAG-antibody (1 hour incubation at 4°C)

  • Elute using 3×FLAG peptide (Sigma)

  • Incubate eluate with uMACS HA magnetic beads (30 minutes on ice)

• Load onto a uMACS column and wash thoroughly .

• Perform on-column digestion with trypsin in 2M urea/100mM Tris-HCl buffer .

• Analyze peptides by mass spectrometry .

This approach identified multiple Rbm10 interaction partners, including components of the Clr6 HDAC complex, HIRA, FACT, CHD1, and Spt6 chromatin remodeling complexes .

What is the significance of Rbm10's interaction with the Clr6 HDAC complex?

The interaction between Rbm10 and the Clr6 HDAC complex represents a critical link between RNA processing and heterochromatin formation. Mass spectrometry data revealed that Rbm10 associates with multiple components of this complex, with Prw1 (a component of Clr6 complex I) showing the highest sequence coverage in the analysis . The table below summarizes key Clr6 complex components that interact with Rbm10:

The functional significance of these interactions is demonstrated by the finding that deletion of rbm10+ disrupts the association of the Clr6 complex with heterochromatin, directly linking Rbm10 to the recruitment of histone deacetylase activity to heterochromatic regions .

What RT-PCR protocols are recommended for studying SPBC119.12 expression and splicing effects?

For RT-PCR analysis of SPBC119.12/Rbm10 and assessment of its splicing effects:

• Use 500 ng of total RNA per reaction as starting material .

• Perform first-strand synthesis with Random Primer and Superscript II RT (Invitrogen) using the following temperature profile:

  • 25°C for 10 minutes

  • 42°C for 50 minutes

  • 70°C for 15 minutes

• For subsequent PCR, use 1 μl from the reverse transcriptase reaction .

• Design primers to detect both normal and alternatively spliced transcripts, especially when comparing wild-type and rbm10Δ strains.

• Include appropriate housekeeping genes as controls for normalization.

This method can help detect subtle splicing changes that might be missed by global RNA-seq analysis.

How should RNA-seq data be analyzed to identify differentially spliced transcripts in rbm10Δ strains?

RNA-seq analysis for identifying splicing changes in rbm10Δ strains should follow these methodological guidelines:

• Prepare poly(A) RNA from total RNA using two rounds of oligo(dT)25 Dynabeads (Invitrogen) purification .

• Fragment RNA at 94°C for 3.5 minutes before cDNA synthesis .

• Align RNA-seq reads that pass the Illumina filter to the S. pombe genome reference sequences (version: ASM294v2) using TopHat with default mapping parameters .

• Generate read counts for each exon-exon and/or exon-intron junction using custom Perl scripts .

• Use the DESeq package to identify differentially expressed genes between rbm10Δ cells and wild-type (WT) .

• Apply Fisher's exact test to compare splicing patterns of each exon (for exon skipping) or each intron (for intron retention) between rbm10Δ cells and WT .

• Use adjusted p-value < 0.05 and |ΔPSI| (or |PIR|) > 10% as the threshold for determining significant splicing differences .

Despite Rbm10's annotation as a splicing factor, RNA-seq analysis revealed that deletion of rbm10+ has minimal effects on global splicing patterns, with the primary impact being on heterochromatin formation .

What are common challenges in SPBC119.12 antibody experiments and how can they be addressed?

Researchers commonly encounter these challenges when working with SPBC119.12 antibodies:

• Low signal in ChIP experiments:

  • Optimize crosslinking time (try 15-45 minutes)

  • Increase antibody amount (1-5 μl)

  • Optimize sonication conditions to generate 200-500 bp fragments

  • Increase cell number for starting material

• Non-specific binding in co-immunoprecipitation:

  • Include additional washing steps with increased salt concentration

  • Add competitors like BSA to reduce non-specific interactions

  • Use tagged versions of Rbm10 with highly specific antibodies against the tag

• Inconsistent results between replicates:

  • Standardize growth conditions (OD600 ~0.6-0.8)

  • Maintain consistent lysis and sonication protocols

  • Use the same antibody lot number between experiments

  • Include at least three biological replicates

How can mass spectrometry data processing be optimized for SPBC119.12 interaction studies?

For optimal processing of mass spectrometry data from SPBC119.12/Rbm10 interaction studies:

• Analyze raw data using the MaxQuant proteomics pipeline (v1.4.0.5) and the built-in Andromeda search engine with the PomBase database .

• Configure the following parameters:

  • Select carbamidomethylation of cysteines as fixed modification

  • Choose oxidation of methionine and acetylation of N-terminus as variable modifications

  • Filter search engine peptide assignments at 1% FDR (False Discovery Rate)

  • Leave the feature match between runs disabled

• For protein-protein interaction analysis:

  • Compare against control samples (e.g., untagged strains or tag-only expressions)

  • Consider implementing statistical approaches that account for abundance differences

  • Validate key interactions using orthogonal methods like co-immunoprecipitation

This approach successfully identified multiple biologically relevant Rbm10 interacting partners, including components of the Clr6 HDAC complexes and chromatin remodelers .

How can understanding SPBC119.12/Rbm10 function in fission yeast inform research on human RBM10-related diseases?

Research on SPBC119.12/Rbm10 in fission yeast provides valuable insights for understanding human RBM10-related disorders:

• Human RBM10 mutations are linked to TARP syndrome, and the fission yeast homolog shares functional similarities .

• Both proteins interact with splicing factors in similar patterns, suggesting evolutionary conservation of molecular functions .

• The unexpected role of fission yeast Rbm10 in heterochromatin formation suggests potential epigenetic regulation functions for human RBM10 that may be currently unexplored.

• Methodologies developed for studying Rbm10's role in recruiting chromatin-modifying complexes can be adapted to investigate whether human RBM10 performs similar functions.

• The finding that Rbm10 binds nascent heterochromatic transcripts suggests that investigating RNA-binding properties of human RBM10 may reveal additional disease-relevant functions.

What molecular mimicry phenomena might be relevant to antibody specificity for SPBC119.12?

While not directly addressed in the provided search results for SPBC119.12, molecular mimicry considerations are important for antibody specificity. Search result provides relevant insights about molecular mimicry in antibody cross-reactivity that can be applied to SPBC119.12 antibody research:

• Bacterial peptides can inhibit specific antigen-antibody binding through molecular mimicry, as demonstrated with multiple bacterial proteins .

• This phenomenon could potentially affect SPBC119.12 antibody specificity if bacterial contaminants are present in experimental preparations.

• The observation that bacterial factors can influence specific binding of antibodies to certain antigens suggests that thorough validation of SPBC119.12 antibodies is essential .

• Researchers should test for cross-reactivity with bacterial proteins, especially when working with preparations that may contain bacterial contaminants.

The table below illustrates high prevalence of bacterial antibodies found in one autoimmune condition, highlighting the importance of considering cross-reactivity:

These findings underscore the importance of careful antibody validation and cross-reactivity testing when working with any antibody, including those targeting SPBC119.12 .