IRC20 Antibody

What is IRC20 and what functional domains should researchers target with antibodies?

IRC20 is a multifunctional protein containing several important domains that researchers should consider when developing or selecting antibodies. Based on structural and functional analyses, IRC20 contains a RING finger domain at its C-terminus (around amino acid position 1239) that confers ubiquitin ligase activity, with the cysteine residue (C1239) being critical for this function . The protein also possesses an ATPase domain with key residues at positions D534 and E535 .

Research has shown that IRC20 interacts with various proteins including CDC48 and can undergo SUMOylation, suggesting its involvement in multiple cellular pathways . Understanding these domains is essential when designing experiments using IRC20 antibodies.

How can researchers validate the specificity of IRC20 antibodies?

Validating antibody specificity is crucial for reliable experimental results. Multiple complementary approaches should be employed:

First, perform Western blot analysis with positive controls (extracts containing IRC20) and negative controls (IRC20 deletion strains). IRC20 migrates slightly above 180 kDa in SDS-PAGE gels, providing a size reference for validation . Additionally, use IRC20 deletion derivatives of different sizes to confirm antibody specificity - the signal should shift according to the expected molecular weight .

For tagged versions of IRC20, compare results between IRC20-specific antibodies and tag-specific antibodies (anti-HA for HA-tagged IRC20, PAP for TAP-tagged IRC20) . Immunodepletion experiments provide further validation - sequential immunoprecipitations should progressively reduce the signal if binding is specific.

Finally, when studying post-translational modifications like SUMOylation, confirm that modifications are detectable with both IRC20 antibodies and modification-specific antibodies (e.g., anti-SUMO) .

What expression systems are suitable for generating recombinant IRC20 for antibody production?

The selection of an appropriate expression system is critical for generating functional IRC20 protein for antibody production. Based on experimental evidence, E. coli strain BL21(DE3)-RIPL has been successfully used to express GST-IRC20-RING fusion proteins . This bacterial expression system is particularly suitable for producing discrete domains of IRC20 (such as the RING domain) rather than the full-length protein.

For immunization purposes, researchers should consider:

• Expressing different domains of IRC20 separately, as the full protein is large (>180 kDa) and may be challenging to express in bacteria

• Using fusion tags like GST to enhance solubility and facilitate purification

• Optimizing expression conditions by testing different temperatures, IPTG concentrations, and induction times

For full-length IRC20, eukaryotic expression systems may be preferable. Yeast systems have successfully expressed various versions of IRC20, including full-length and truncated forms with different tags (HA, TAP) . These constructs could serve as both immunogens and positive controls in antibody validation.

What is the optimal protocol for using IRC20 antibodies in immunoprecipitation experiments?

Successful immunoprecipitation of IRC20 requires careful optimization of experimental conditions. Based on protocols that have yielded reliable results, the following methodology is recommended:

First, prepare cell lysates under conditions that preserve protein interactions. For yeast cells expressing IRC20, grow cultures to an A600 of 1.0, harvest by centrifugation, and resuspend in RNP lysis buffer (0.1 M HEPES pH 7.4, 100 mM NaCl, 0.1% NP-40, 0.1 mM PMSF, 1 mg/ml each of leupeptin, pepstatin, and aprotinin) . When studying SUMOylation, it's critical to add 10 mM N-Ethylmaleimide (NEM) to the lysis buffer to inhibit SUMO proteases .

For the immunoprecipitation procedure:

• Add 1 μg crude cell extract to 40 μl antibody-conjugated beads (e.g., anti-HA agarose for HA-tagged IRC20)

• Incubate with rotation at 4°C for 90 minutes

• Wash beads thoroughly (3 times with 500 μl RNP buffer)

• Elute proteins by boiling in SDS sample buffer for 2 minutes

For detecting IRC20 and interacting partners after immunoprecipitation, Western blot using appropriate antibodies is recommended: anti-HA for HA-tagged IRC20, PAP antibody for TAP-tagged IRC20, and anti-SUMO for detecting SUMOylated forms .

Always include proper controls, such as immunoprecipitation from cells not expressing IRC20 or expressing mutant versions.

How should researchers design experiments to study IRC20 SUMOylation?

Studying IRC20 SUMOylation requires specialized experimental approaches to preserve and detect this modification. Based on successful methodologies, the following comprehensive approach is recommended:

First, prevent deSUMOylation during sample preparation by adding 10 mM N-Ethylmaleimide (NEM) to all lysis buffers . This irreversibly inhibits SUMO proteases that could otherwise remove SUMO modifications during extract preparation.

For detection of SUMOylated IRC20:

• Immunoprecipitate IRC20 under native conditions using specific antibodies or anti-tag antibodies for tagged versions

• Separate by SDS-PAGE and perform Western blotting

• Probe with both IRC20 antibodies and anti-SUMO antibodies on parallel blots or after membrane stripping

To confirm specificity of SUMOylation signals, multiple controls are essential:

• Compare SUMOylation patterns between wild-type and different-sized IRC20 deletion derivatives - the SUMOylated bands should shift according to the size of the IRC20 derivative

• Enhance detection by overexpressing SUMO - the intensity of SUMOylated bands should increase

• Compare samples prepared with and without NEM to demonstrate the importance of preventing deSUMOylation

For more quantitative analysis, consider using quantitative mass spectrometry to identify specific SUMOylation sites within IRC20, which would enable the creation of non-SUMOylatable mutants for functional studies.

What controls are necessary when studying IRC20's ubiquitin ligase activity?

When investigating IRC20's ubiquitin ligase activity, rigorous controls are essential to ensure reliable and interpretable results. Based on established methodologies, the following experimental design is recommended:

For in vitro ubiquitylation assays, include these critical controls:

• Catalytically inactive mutant: The IRC20-C1239A RING domain mutant serves as a negative control as it lacks ubiquitin ligase activity

• No E1 or E2 enzyme controls: Omitting either Uba1 (E1) or UbcH5a (E2) from the reaction confirms that ubiquitylation is occurring through the canonical ubiquitylation cascade

• No ATP control: Ubiquitylation is ATP-dependent, so reactions without ATP should show no activity

• Time course analysis: To demonstrate enzyme kinetics rather than non-specific reactions

For a standard in vitro ubiquitylation reaction, use:

• 100 ng purified Uba1 (E1)

• 200 ng purified UbcH5a (E2)

• 10 μg bacterial lysate containing GST-IRC20-RING

• 50 mM Tris-Cl (pH 7.3), 2.5 mM MgCl2, 500 μM DTT, and 2 mM ATP

Incubate reactions at 30°C for 90 minutes, then analyze by SDS-PAGE and Western blotting with both anti-ubiquitin and anti-GST antibodies to detect ubiquitylated products and confirm the presence of IRC20-RING .

For in vivo studies of IRC20's ubiquitin ligase activity, compare ubiquitylation patterns in cells expressing wild-type IRC20 versus the C1239A mutant, focusing on potential substrate proteins identified through interaction studies.

How can researchers use IRC20 antibodies to identify and characterize protein-protein interactions?

Identifying IRC20's interaction partners provides crucial insights into its cellular functions. A multi-faceted approach using antibodies is recommended for comprehensive characterization:

Co-immunoprecipitation represents the foundation of interaction studies. Immunoprecipitate IRC20 using specific antibodies or anti-tag antibodies for tagged versions, then analyze co-precipitated proteins by Western blotting or mass spectrometry . When studying interactions with specific candidates like CDC48, use reciprocal co-immunoprecipitation (i.e., immunoprecipitate CDC48 and probe for IRC20) to strengthen evidence for direct interaction .

To map interaction domains, use the collection of IRC20 truncation constructs described in research (pAR58-pAR62, pAR67-pAR71) . By determining which IRC20 fragments retain binding to specific partners, you can identify critical interaction surfaces.

For investigating the role of specific IRC20 domains in protein interactions, test how mutations in key domains (C1239A in the RING finger, D534A/E535A in the ATPase domain) affect binding to partners . This approach reveals whether enzymatic activities of IRC20 are required for specific interactions.

For capturing transient or weak interactions, consider in vivo cross-linking prior to immunoprecipitation or proximity labeling approaches (though not specifically mentioned in the search results, these are valuable complementary methods).

What methods can be used to study the subcellular localization of IRC20 using antibodies?

Understanding IRC20's subcellular localization is essential for elucidating its functions in different cellular compartments. While the search results don't explicitly describe localization studies, the following methodological approaches would be appropriate based on IRC20's known functions:

Immunofluorescence microscopy represents the primary approach. Fix cells under conditions that preserve nuclear and chromatin structures (particularly important if IRC20 is involved in chromatin regulation as suggested by search result ). Use IRC20-specific antibodies or tag-specific antibodies for tagged versions, followed by fluorophore-conjugated secondary antibodies. Counter-stain with DAPI to visualize nuclei and markers for specific compartments (e.g., mitochondria, endoplasmic reticulum) to determine co-localization.

For higher resolution, employ super-resolution microscopy techniques such as STORM or STED, which can provide nanometer-scale localization information, potentially revealing IRC20's association with specific nuclear substructures.

Biochemical fractionation offers complementary evidence. Separate cellular components (cytoplasm, nucleus, chromatin) through differential centrifugation and analyze IRC20 distribution by Western blotting. This approach can confirm microscopy results and provide quantitative data on IRC20's distribution.

To study dynamic localization, generate fluorescently-tagged IRC20 constructs for live-cell imaging, though validation with antibody-based approaches is essential to ensure the tag doesn't alter localization.

How can IRC20 antibodies be utilized in chromatin immunoprecipitation (ChIP) experiments?

Based on the potential role of IRC20 in chromatin regulation suggested in search result , ChIP experiments would be valuable for identifying genomic regions associated with IRC20. The following methodology is recommended:

Start with cross-linking to preserve protein-DNA interactions. Treat cells with formaldehyde (typically 1% for 10-15 minutes) to cross-link proteins to DNA. After quenching with glycine, lyse cells and sonicate chromatin to fragments of approximately 200-500 bp.

For immunoprecipitation, incubate sonicated chromatin with IRC20 antibodies or tag-specific antibodies for tagged versions. Include appropriate controls: IgG from the same species as the primary antibody (negative control) and antibodies against known chromatin-associated factors (positive control).

After washing to remove non-specific binding, reverse cross-links and purify DNA. Analyze by quantitative PCR for specific candidate regions or by next-generation sequencing (ChIP-seq) for genome-wide binding profiles.

To confirm specificity, perform ChIP in cells where IRC20 is depleted or deleted, which should show significantly reduced signal. Additionally, compare ChIP results between wild-type IRC20 and mutant versions (particularly the ATPase mutant, as ATPase activity is often important for chromatin remodeling functions).

For investigating potential cooperation with other chromatin-associated factors, consider sequential ChIP (Re-ChIP) where chromatin is first immunoprecipitated with IRC20 antibodies, then with antibodies against potential partners.

What are common challenges in detecting IRC20 by Western blotting and how can they be overcome?

Detecting IRC20 by Western blotting presents several technical challenges that require specific strategies to overcome:

The high molecular weight of IRC20 (>180 kDa) creates the primary difficulty . To address this:

• Use low percentage SDS-PAGE gels (6-8%) to better resolve high molecular weight proteins

• Extend transfer times (overnight at low voltage) or use specialized transfer systems designed for large proteins

• Include molecular weight markers >180 kDa to accurately identify IRC20 bands

Low abundance of IRC20 or modified forms (such as SUMOylated IRC20) can limit detection. To enhance sensitivity:

• Enrich IRC20 by immunoprecipitation before Western blotting

• Use high-sensitivity detection reagents (enhanced chemiluminescence or fluorescent secondary antibodies)

• For SUMOylated forms, preserve modifications by adding 10 mM NEM to lysis buffers

• Consider overexpressing IRC20 or the modifier (e.g., SUMO) to increase abundance

Non-specific antibody binding often complicates interpretation. To improve specificity:

• Optimize blocking conditions (test different blocking agents and concentrations)

• Increase antibody dilution to reduce background

• Include controls like IRC20 deletion strains or knockdowns

• Use multiple antibodies targeting different IRC20 epitopes or tag-specific antibodies for tagged versions

Degradation during sample preparation can lead to multiple bands or weak signals. To minimize this:

• Keep samples cold throughout preparation

• Add protease inhibitors to all buffers

• Use freshly prepared samples when possible

• Add denaturing agents like urea to lysis buffers for difficult samples

How should researchers address inconsistent results in IRC20 immunoprecipitation experiments?

Inconsistent immunoprecipitation results can stem from multiple sources. Based on established protocols and general immunoprecipitation principles, the following troubleshooting strategies are recommended:

Antibody quality and binding conditions are frequent sources of variability. To address these:

• Test different antibody lots or sources

• Optimize antibody concentration - both too much and too little can be problematic

• Adjust binding conditions (time, temperature, buffer composition)

• For tagged IRC20, compare different tags (HA, TAP) and corresponding antibodies

Cell lysis and protein extraction efficiency significantly impact results. Improve these by:

• Testing different lysis methods (mechanical disruption via glass beads for yeast as described in search result , various detergents for mammalian cells)

• Adjusting lysis buffer composition (salt concentration, detergent type and percentage)

• Ensuring complete lysis by microscopic examination of cell debris

• Optimizing protein concentration in the input material

Non-specific binding to beads or antibodies creates background and variability. Reduce this by:

• Pre-clearing lysates with beads alone before adding antibody

• Adding competitors like BSA to reduce non-specific interactions

• Increasing wash stringency, but not so much that specific interactions are disrupted

• Using more selective affinity tags when possible

Post-translational modifications can affect antibody recognition. Account for this by:

• Using antibodies that recognize IRC20 regardless of modification status

• Including modification-preserving reagents (like NEM for SUMOylation)

• Testing different fixation or lysis conditions that may preserve or disrupt modifications

What strategies can resolve difficulties in detecting IRC20 protein-protein interactions?

Detecting protein-protein interactions involving IRC20 can be challenging due to various factors. Based on the methodologies described in search result and general principles in protein interaction studies, the following strategies are recommended:

Weak or transient interactions are often difficult to capture. Enhance detection by:

• Using chemical cross-linking prior to immunoprecipitation to stabilize interactions

• Testing different cross-linkers with various spacer arm lengths

• Optimizing cross-linking conditions (time, temperature, pH)

• Employing proximity labeling approaches (BioID, TurboID) as complementary methods

Buffer conditions significantly impact interaction stability. Optimize by systematically testing:

• Salt concentration (typically 100-300 mM)

• Detergent type and concentration (start with mild detergents like 0.1% NP-40)

• pH variations (typically pH 7.0-8.0)

• Addition of stabilizing agents (glycerol, specific ions)

Competition from endogenous proteins can mask interactions. Address by:

• Using overexpression systems for both IRC20 and interaction partners

• Creating systems where endogenous competitors are depleted or deleted

• Using in vitro binding assays with purified components

Domain-specific interactions may be missed when using full-length proteins. Investigate by:

• Testing the extensive collection of IRC20 truncation constructs described in search result

• Creating additional domain-specific constructs as needed

• Using peptide arrays to identify specific interaction motifs

Post-translational modifications may be required for certain interactions. Preserve these by:

• Including phosphatase inhibitors for phosphorylation-dependent interactions

• Adding NEM to preserve SUMOylation-dependent interactions

• Testing interaction under conditions that promote or inhibit specific modifications

What recent discoveries have emerged regarding IRC20's cellular functions?

Recent research has revealed several important aspects of IRC20's cellular functions through antibody-based approaches:

IRC20 possesses ubiquitin ligase activity through its RING finger domain, with the cysteine residue at position 1239 being critical for this function . In vitro ubiquitylation assays with the purified RING domain have demonstrated this activity, while the C1239A mutant lacks this function, providing important insights into IRC20's enzymatic capabilities .

Post-translational modification of IRC20 itself has been discovered, particularly SUMOylation . This modification has been confirmed through multiple approaches, including immunoprecipitation followed by Western blotting with anti-SUMO antibodies, size shift analysis with deletion derivatives, and enhanced modification when SUMO is overexpressed . This SUMOylation likely plays a regulatory role in IRC20 function.

Protein interaction studies have identified CDC48 as an IRC20 interaction partner . CDC48 is an AAA-ATPase involved in various cellular processes including protein quality control and chromatin-associated degradation. This interaction suggests IRC20 may function in similar pathways, potentially linking its ubiquitin ligase activity to specific cellular processes.

Additionally, there are indications of IRC20's involvement in chromatin regulation . The connection between IRC20 and "silent chromatin" mentioned in search result suggests roles in gene silencing or heterochromatin maintenance, potentially linking IRC20's enzymatic activities to epigenetic regulation.

How might IRC20 be involved in human disease processes based on current research?

While the search results don't directly address IRC20's role in human diseases, the protein's functional characteristics suggest several potential connections that merit investigation:

Given IRC20's ubiquitin ligase activity , dysregulation could potentially contribute to diseases associated with protein homeostasis disruption. Many human E3 ubiquitin ligases have been implicated in neurodegenerative disorders (Parkinson's, Alzheimer's) and cancer when their activity is altered. IRC20's human homologs should be investigated in these contexts.

The interaction between IRC20 and CDC48 provides another potential disease connection. Human homologs of CDC48 (like p97/VCP) are associated with inclusion body myopathy, Paget's disease, and frontotemporal dementia when mutated. If IRC20's human homologs function in the same pathway, they might contribute to similar disorders.

IRC20's apparent involvement in chromatin regulation suggests potential roles in epigenetic disorders or cancers characterized by aberrant gene silencing. Many chromatin regulators are known oncogenes or tumor suppressors, warranting investigation of IRC20 homologs in cancer contexts.

It's important to note that directly translating findings from yeast to human disease requires identifying and characterizing the corresponding human homologs. Antibodies specifically targeting these human proteins would be essential for such translational research.

What are promising new technologies for studying IRC20 that researchers should consider?

Emerging technologies offer exciting new possibilities for studying IRC20's functions and interactions beyond traditional antibody-based approaches:

Proximity labeling methods represent a powerful approach for identifying protein interactions in living cells. By fusing IRC20 to enzymes like BioID or TurboID, researchers can label proteins in close proximity to IRC20 in vivo. This approach captures weak or transient interactions that might be missed by traditional co-immunoprecipitation and complements the interaction studies described in search result .

CRISPR/Cas9 genome editing enables sophisticated genetic manipulation of IRC20. Researchers can generate endogenously tagged versions of IRC20 or its homologs, create precise mutations targeting key residues like C1239 in the RING domain , or develop conditional knockouts. This approach ensures that IRC20 is studied at physiological expression levels, avoiding artifacts from overexpression.

Advanced chromatin profiling techniques such as CUT&RUN or CUT&Tag offer heightened sensitivity for mapping IRC20's genomic associations if it indeed functions in chromatin regulation as suggested by search result . These methods require less starting material than traditional ChIP and provide higher signal-to-noise ratios, making them ideal for factors with more subtle chromatin associations.

Single-molecule imaging techniques could reveal dynamic aspects of IRC20 function. Super-resolution microscopy combined with IRC20-specific antibodies or fluorescently tagged IRC20 would allow visualization of its localization at near-molecular resolution. Single-molecule tracking could elucidate IRC20's movement and residence time at specific cellular structures.

Integrative structural biology approaches (cryo-EM, cross-linking mass spectrometry) used in conjunction with highly specific antibodies could help determine IRC20's structure and how it changes upon interaction with partners or post-translational modification, providing mechanistic insights into its function.