IRC5 Antibody

What is IRC5 and why is it significant in molecular biology research?

IRC5 (Increased Recombination Centers 5) is a putative Snf2-like DNA translocase found in Saccharomyces cerevisiae that plays a crucial role in sister chromatid cohesion. It contributes to cohesin association with chromatin by interacting with the Scc1 cohesin subunit. IRC5's significance lies in its involvement in maintaining genomic stability, as disruption of the IRC5 gene leads to premature sister chromatid separation and instability of rDNA regions. The human homolog of IRC5, known as LSH/HELLS, has been implicated in DNA methylation regulation and double-strand break repair . Understanding IRC5's function provides insights into fundamental chromosome maintenance mechanisms across species.

How do IRC5 antibodies differ from other chromatin-associated protein antibodies?

IRC5 antibodies target a specific DNA translocase that functions in the cohesin pathway, distinguishing them from antibodies targeting other chromatin-associated proteins. When designing experiments, researchers should consider that IRC5 antibodies recognize a protein that interacts with both the cohesin complex (through Scc1) and the cohesin loading complex (through Scc2) . This dual interaction profile differs from antibodies targeting proteins with more limited chromatin associations. For immunoprecipitation experiments, protocols similar to those used for Scc1 can be adapted, using Protein G Dynabeads for antibody capture followed by multiple washes with appropriate IP buffer to maintain specific binding .

What are the recommended applications for IRC5 antibodies in yeast research?

IRC5 antibodies are valuable tools for several experimental applications in yeast research:

• Chromatin immunoprecipitation (ChIP): To map IRC5 binding sites across the genome, particularly at centromeres, chromosome arms, and rDNA regions

• Co-immunoprecipitation: To confirm and characterize interactions with cohesin subunits and the loading complex

• Immunofluorescence: To visualize IRC5 localization during different cell cycle phases

• Western blotting: To quantify IRC5 expression levels or detect post-translational modifications

For optimal results in co-immunoprecipitation experiments, use Protein G Dynabeads for antibody capture, followed by four washes with IP buffer before eluting proteins with Laemmli buffer (2% SDS, 20% glycerol) .

How should I design ChIP experiments to investigate IRC5 binding at specific genomic loci?

When designing ChIP experiments to study IRC5 binding:

• Crosslinking optimization: Start with 1% formaldehyde for 10-15 minutes at room temperature, as IRC5 interacts with both DNA and protein complexes

• Sonication parameters: Adjust to achieve chromatin fragments of 200-500bp

• Antibody selection: Use antibodies validated specifically for ChIP applications

• Controls: Include:

  • Input chromatin control

  • IgG negative control

  • Positive control targeting known IRC5 interactors (Scc1)

  • Chromatin from IRC5-deleted strains as specificity control

• Primer design: For qPCR validation, design primers targeting:

  • Centromeric regions

  • Chromosome arm locations with known cohesin enrichment

  • rDNA repeats

  • Negative control regions with no expected IRC5 binding

Compare IRC5 binding profiles with those of cohesin subunits to identify correlation patterns that may indicate functional cooperation .

What are the optimal methods for detecting the interaction between IRC5 and cohesin complexes?

To optimally detect interactions between IRC5 and cohesin complexes:

• Co-immunoprecipitation: Use anti-IRC5 antibodies to pull down IRC5 and associated proteins, then probe for Scc1 and other cohesin subunits. Alternatively, immunoprecipitate with anti-Scc1 antibodies and probe for IRC5.

• Proximity ligation assay (PLA): For detecting in situ interactions with spatial resolution:

  • Use primary antibodies from different species (e.g., rabbit anti-IRC5 and mouse anti-Scc1)

  • Apply species-specific PLA probes

  • Perform ligation and amplification according to manufacturer protocols

  • Quantify interaction signals relative to appropriate controls

• Yeast two-hybrid screening: For mapping specific interaction domains:

  • Create bait constructs with full-length IRC5 and various truncated versions

  • Screen against prey constructs containing cohesin subunits

  • Validate positive interactions with co-IP experiments

• Size exclusion chromatography: To determine if IRC5 is part of the intact cohesin complex or interacts with subcomplexes

For all approaches, compare wild-type IRC5 with translocase-deficient mutants to assess whether the enzymatic activity is required for the interaction .

How can I validate the specificity of IRC5 antibodies for immunological applications?

To validate IRC5 antibody specificity:

• Western blot validation:

  • Compare signals between wild-type yeast and IRC5 deletion strains

  • Test antibody on recombinant IRC5 protein

  • Perform peptide competition assays using the immunizing peptide

• Immunoprecipitation controls:

  • IP from IRC5-tagged strains (e.g., IRC5-HA or IRC5-FLAG)

  • IP from IRC5 knockout strains as negative control

  • Capture antibodies with Protein G Dynabeads for optimal results

• Cross-reactivity testing:

  • Test against related Snf2-family proteins

  • Assess reactivity in different yeast species

  • For antibodies intended for human LSH/HELLS detection, validate in both yeast and human samples

• Epitope mapping:

  • Use truncated IRC5 constructs to confirm target region

  • Generate dot blots with synthesized peptides covering potential epitopes

Include appropriate positive and negative controls in each experiment to ensure reliable interpretation of results.

How does IRC5 contribute to cohesin loading, and how can antibodies help elucidate this mechanism?

IRC5's contribution to cohesin loading involves multiple mechanisms that can be investigated using antibodies:

• Chromatin remodeling activity: IRC5's Snf2-like DNA translocase activity appears essential for creating appropriate chromatin environments for cohesin loading. Antibodies can help track whether IRC5 mutants lacking translocase activity properly localize to loading sites despite functional deficiency.

• Interaction with cohesin loading complex: Research indicates IRC5 affects both Scc2 chromatin binding and Scc2-Scc1 interaction. Sequential ChIP experiments using IRC5 and Scc2 antibodies can determine whether they co-occupy the same genomic locations.

• Temporal dynamics: Combine IRC5 antibodies with cell synchronization techniques to determine when IRC5 associates with chromatin relative to cohesin loading during the cell cycle.

• Interdependence testing: Through reciprocal ChIP experiments in different genetic backgrounds (wild-type, IRC5Δ, Scc2 mutants), determine whether IRC5 and Scc2 depend on each other for chromatin association.

Research has demonstrated that in the absence of IRC5, both chromatin-bound Scc2 levels and physical interaction between Scc1 and Scc2 are reduced, suggesting IRC5 functions as an auxiliary factor facilitating cohesin association with chromatin .

What strategies can optimize IRC5 antibody performance in difficult experimental conditions?

For optimizing IRC5 antibody performance in challenging conditions:

• Crosslinking antibody to beads:

  • Covalently link antibodies to Protein G Dynabeads using BS3 or DMP crosslinkers

  • This prevents antibody leaching during elution and reduces background

  • Particularly useful when antibody heavy chains may interfere with detection of similarly sized target proteins

• Buffer optimization for low-abundance detection:

  • Add phosphatase inhibitors (10 mM NaF, 1 mM Na3VO4)

  • Include protease inhibitors freshly before each experiment

  • Test buffers with varying ionic strengths (150-500 mM NaCl)

  • Consider adding 0.1% SDS to reduce non-specific binding

• Epitope masking solutions:

  • For formaldehyde-fixed samples, incorporate antigen retrieval steps

  • Test different detergents (Triton X-100, NP-40, Tween-20) at various concentrations

  • Pre-clear lysates with Protein G beads before immunoprecipitation

  • Use specialized extraction buffers for chromatin-bound proteins

• Signal amplification techniques:

  • Employ tyramide signal amplification for immunofluorescence

  • Use polymer-based detection systems for immunohistochemistry

  • Consider biotin-streptavidin systems for enhanced sensitivity

These optimizations can significantly improve results when studying IRC5 in contexts where it may be less abundant or in complex chromatin environments .

How can IRC5 antibodies be used to study its function in DNA damage response pathways?

IRC5 antibodies can be strategically deployed to investigate its role in DNA damage response:

• Damage-induced localization studies:

  • Treat cells with DNA damaging agents (MMS, HU, CPT, phleomycin)

  • Perform ChIP-seq using IRC5 antibodies to map damage-dependent binding sites

  • Compare with γ-H2AX localization to identify direct association with damage sites

  • Monitor kinetics of recruitment using ChIP at different time points after damage

• Interactome changes after damage:

  • Conduct immunoprecipitation with IRC5 antibodies before and after DNA damage

  • Use mass spectrometry to identify damage-specific interaction partners

  • Focus on proteins involved in homologous recombination, as IRC5 deletion increases Rad52 foci

• Post-translational modification analysis:

  • Combine IRC5 immunoprecipitation with phospho-specific antibodies

  • Investigate whether DNA damage triggers modifications of IRC5

  • Determine if modifications alter IRC5's association with chromatin or cohesin

• Functional domain analysis:

  • Generate strains expressing IRC5 with mutations in specific domains

  • Use antibodies to assess how mutations affect localization and interactions

  • Correlate with sensitivity to DNA damaging agents

The resulting data should be interpreted in context with the observation that IRC5 deletion causes increased sensitivity to genotoxins like camptothecin, phleomycin, hydroxyurea, and methyl methanesulfonate .

How should ChIP-seq data for IRC5 be analyzed to identify biologically significant binding patterns?

When analyzing ChIP-seq data for IRC5:

• Quality control metrics:

  Metric	Acceptable threshold	Notes
  Mapping rate	>80%	Lower rates may indicate sample quality issues
  Library complexity	NRF > 0.8	Non-redundant fraction indicates diversity
  Signal-to-noise ratio	>3	Higher ratios indicate more specific enrichment
  Peak number	Compare to cohesin ChIP	IRC5 should have substantial overlap with cohesin peaks

• Genomic distribution analysis:

  • Categorize peaks by genomic features (centromeres, rDNA, chromosome arms)

  • Compare with cohesin (Scc1) binding patterns to identify:

    • Sites with both IRC5 and cohesin

    • Sites with cohesin but no IRC5

    • Sites with IRC5 but no cohesin

  • Correlate with Scc2 loading sites to determine overlap with cohesin loading complex

• Motif discovery:

  • Perform de novo motif analysis on IRC5 binding sites

  • Compare identified motifs with known cohesin and Scc2/Scc4 association sequences

  • Search for enrichment of sequence features associated with nucleosome-depleted regions

• Integration with other datasets:

  • Overlay with nucleosome positioning data

  • Compare with chromatin accessibility (ATAC-seq, DNase-seq)

  • Correlate with histone modification patterns, particularly those associated with active chromatin

• Differential binding analysis:

  • Compare IRC5 binding before and after DNA damage

  • Analyze changes during cell cycle progression

  • Assess binding pattern changes in cohesin mutants

These analyses should reveal whether IRC5 primarily acts at cohesin loading sites, shows independent binding patterns, or functions at specific genomic regions requiring its translocase activity .

What are the best approaches for interpreting conflicting results between IRC5 antibody experiments and genetic models?

When facing discrepancies between antibody-based results and genetic models:

• Characterize antibody limitations systematically:

  • Verify epitope accessibility in different experimental conditions

  • Test multiple antibodies targeting different IRC5 regions

  • Validate antibody specificity in IRC5 knockout controls

  • Consider that antibodies may fail to detect certain post-translational modifications

• Evaluate genetic model caveats:

  • Assess potential adaptive responses in knockout models

  • Check for effects on neighboring genes, particularly RSC8, which shows reduced expression (~70%) in IRC5Δ strains

  • Consider compensation by redundant pathways in long-term deletion models

  • Use inducible/acute depletion systems (e.g., auxin-inducible degron) as alternatives

• Reconciliation strategies:

  • Design experiments that bridge methodologies:

    • ChIP-seq with antibodies versus CUT&RUN with tagged IRC5

    • Use both tag-specific and IRC5-specific antibodies in parallel

    • Compare acute versus chronic loss-of-function models

  • Employ complementary approaches:

    • Supplement IRC5 antibody studies with IRC5-fusion protein visualization

    • Validate key findings with orthogonal technologies (microscopy, genomics)

• Develop explanatory hypotheses:

  • Consider context-dependent functions of IRC5

  • Investigate potential non-canonical roles

  • Examine whether discrepancies relate to specific functional domains

How can researchers distinguish between direct and indirect effects when studying IRC5 function using antibodies?

To differentiate direct from indirect IRC5 effects:

• Temporal resolution experiments:

  • Design time-course studies following IRC5 induction or depletion

  • Use rapid nuclear depletion systems (anchor-away technique) with IRC5 antibodies

  • Track primary (early) versus secondary (late) effects on cohesin loading and chromosome cohesion

  • Compare kinetics with known direct effects of cohesin complex disruption

• Biochemical interaction validation:

  • Perform in vitro reconstitution experiments with purified components

  • Use recombinant IRC5 in DNA binding assays to test direct DNA interactions

  • Assess whether IRC5's translocase activity directly affects cohesin loading in reconstituted systems

• Domain-specific mutant analysis:

  • Generate separation-of-function mutations targeting specific IRC5 domains

  • Use antibodies to track mutant IRC5 localization and interactions

  • Correlate molecular defects with functional outcomes

  • Particularly examine translocase activity mutants, which have been shown to disrupt IRC5's function in the cohesion pathway

• Proximity-based approaches:

  • Employ BioID or APEX2 proximity labeling fused to IRC5

  • Compare labeled proteins with those identified in standard co-IP experiments

  • Identify proteins consistently detected across multiple methodologies

This systematic approach helps establish causality beyond correlation and allows researchers to build more accurate models of IRC5's mechanistic contributions to chromosome cohesion and genome stability.

What are common pitfalls when using IRC5 antibodies for chromatin immunoprecipitation and how can they be addressed?

Common ChIP pitfalls with IRC5 antibodies and their solutions:

• Low signal-to-noise ratio:

  Problem	Potential solution
  High background	Increase wash stringency; use a mixture of low and high salt washes
  Weak signal	Optimize crosslinking time; test different sonication conditions
  Non-specific binding	Pre-clear chromatin with protein G beads; use specific blocking agents

• Inconsistent enrichment:

  • Ensure adequate crosslinking for protein-protein interactions (IRC5 with cohesin)

  • Optimize chromatin fragmentation to 200-500bp

  • Consider dual crosslinking (formaldehyde + protein crosslinkers) for protein complexes

  • Standardize cell synchronization to account for cell cycle-dependent binding

• Poor reproducibility:

  • Standardize growth conditions and harvesting protocols

  • Use spike-in controls for normalization

  • Perform technical replicates with the same chromatin preparation

  • Consider sequential ChIP (ReChIP) to enhance specificity for complexes

• Epitope masking:

  • Test antibodies recognizing different IRC5 epitopes

  • Adjust sonication conditions to improve epitope accessibility

  • Try alternative crosslinking methods or native ChIP approaches

  • Consider using tagged IRC5 strains in parallel with antibody-based ChIP

Following optimization, researchers should validate enrichment at known IRC5 binding sites (such as centromeric regions and chromosome arms) using qPCR before proceeding to genome-wide analyses .

How can researchers ensure reproducibility in co-immunoprecipitation experiments involving IRC5?

To ensure reproducibility in IRC5 co-IP experiments:

• Standardize lysate preparation:

  • Harvest cells at consistent density and growth phase

  • Use precise cell lysis conditions (buffer composition, lysis time, temperature)

  • Quantify protein concentration and standardize input amounts

  • Pre-clear lysates with beads alone to reduce non-specific binding

• Antibody validation protocol:

  • Test antibody specificity with positive controls (wild-type extract) and negative controls (IRC5Δ extract)

  • Determine optimal antibody concentration through titration

  • Validate detection of interaction partners with known standards

  • Use consistent antibody lots or validate new lots against previous results

• Technical considerations:

  • Capture antibodies with Protein G Dynabeads for consistent performance

  • Perform four standardized washes with IP buffer to maintain reproducibility

  • Elute proteins with Laemmli buffer (2% SDS, 20% glycerol) for complete recovery

  • Document all experimental parameters meticulously

• Quantification and normalization:

  • Use internal loading controls for Western blot normalization

  • Implement quantitative image analysis with appropriate software

  • Calculate enrichment ratios relative to input samples

  • Report statistical measures of reproducibility across independent experiments

Implementing these standardization practices will significantly improve consistency in detecting IRC5 interactions with cohesin components and other chromatin-associated factors.

What are the best storage and handling practices for maintaining IRC5 antibody efficacy over time?

For optimal IRC5 antibody preservation:

• Storage conditions:

  Antibody format	Recommended storage	Avoid
  Lyophilized	-20°C or -80°C	Repeated freeze-thaw
  Purified IgG	4°C (short-term) or -20°C with glycerol (long-term)	Temperatures >4°C
  Ascites/serum	-80°C in small aliquots	Multiple freeze-thaw cycles
  Conjugated	Based on fluorophore stability, typically 4°C in dark	Light exposure, temperature fluctuations

• Aliquoting strategy:

  • Prepare single-use aliquots immediately upon receiving antibodies

  • Use low-binding microcentrifuge tubes to prevent adsorption

  • Include carrier protein (BSA) for dilute antibody solutions

  • Document date, concentration, and number of freeze-thaw cycles for each aliquot

• Contamination prevention:

  • Use sterile techniques when handling antibody solutions

  • Include preservatives (0.02% sodium azide) for refrigerated storage

  • Filter solutions if precipitation is observed

  • Avoid introducing bacteria or fungi

• Performance monitoring:

  • Test activity periodically against reference samples

  • Compare current results with historical data

  • Maintain a log of antibody performance over time

  • Consider generating new antibodies if performance deteriorates significantly

These practices will help maintain antibody functionality, ensuring consistent results across experiments conducted over extended research periods.

How can structural studies of IRC5 inform antibody development for specific functional domains?

Structural insights into IRC5 can guide targeted antibody development:

• Domain-specific antibody design:

  • Structure-based epitope prediction for:

    • Snf2-like ATPase domain (targeting catalytic residues)

    • DNA-binding domain (targeting residues that contact DNA)

    • Cohesin-interaction domains (targeting key interaction interfaces)

  • Develop conformation-specific antibodies that distinguish between ATP-bound and unbound states

  • Generate antibodies that specifically recognize translocase-active versus inactive conformations

• Structural considerations for epitope selection:

  Domain	Epitope considerations	Potential applications
  ATPase core	Select surface-exposed loops	Monitor catalytic state
  DNA-binding region	Target accessible regions not obscured by DNA	Study DNA-free populations
  Cohesin-interaction sites	Focus on interfaces identified through structural studies	Block specific interactions

• Structure-guided validation approaches:

  • Use purified domain fragments for specificity testing

  • Develop competitive binding assays based on structural interfaces

  • Employ site-directed mutagenesis of key residues to validate epitope recognition

• Applications of domain-specific antibodies:

  • Distinguish between different functional states of IRC5 in vivo

  • Block specific interactions while preserving others

  • Study conformational changes associated with ATP hydrolysis cycle

The human IRC5 homolog (LSH/HELLS) structural information may provide additional insights for designing antibodies that recognize conserved functional domains across species .

What novel methodologies are emerging for studying IRC5 interactions with chromatin and the cohesin complex?

Emerging methodologies for studying IRC5 interactions include:

• Proximity-based mapping technologies:

  • BioID or TurboID fusion with IRC5 to identify proximal proteins in living cells

  • APEX2-mediated biotinylation for temporal control of proximity labeling

  • Split-BioID systems to detect specific IRC5-cohesin interactions

  • CUT&RUN or CUT&Tag for high-resolution mapping of IRC5 binding sites

• Live-cell imaging approaches:

  • Single-molecule tracking of fluorescently tagged IRC5

  • FRAP (Fluorescence Recovery After Photobleaching) to measure IRC5 dynamics

  • FRET sensors to detect conformational changes during translocase activity

  • Lattice light-sheet microscopy for 3D visualization of IRC5-cohesin interactions

• Genomic technologies:

  • HiChIP to link IRC5 binding with 3D chromatin structure

  • Micro-C for nucleosome-resolution interaction maps at IRC5 binding sites

  • ChIP-SICAP to identify chromatin-bound protein complexes containing IRC5

  • ChEC-seq (Chromatin Endogenous Cleavage) using IRC5-MNase fusions

• Structural methodologies:

  • Cryo-EM of IRC5-cohesin complexes

  • Hydrogen-deuterium exchange mass spectrometry to map interaction interfaces

  • Integration of crosslinking mass spectrometry with molecular modeling

  • Single-particle tracking combined with super-resolution microscopy

These advanced methodologies will provide deeper insights into how IRC5's translocase activity contributes to cohesin loading and chromosome cohesion at a mechanistic level .

How might understanding the relationship between IRC5 and its human homolog (LSH/HELLS) inform translational research?

The relationship between yeast IRC5 and human LSH/HELLS offers translational research opportunities:

• Conserved functional mechanisms:

  • Compare chromatin remodeling activities between IRC5 and LSH/HELLS

  • Determine whether LSH/HELLS also affects cohesin loading in human cells

  • Investigate whether DNA methylation regulation by LSH/HELLS relates to its role in chromosome cohesion

  • Develop antibodies that recognize conserved functional domains across species

• Disease relevance of LSH/HELLS:

  • LSH/HELLS has been implicated in DNA methylation and double-strand break repair

  • Study whether cohesion defects contribute to LSH/HELLS-associated pathologies

  • Investigate potential roles in cancer, where chromosome cohesion is often disrupted

  • Develop diagnostic antibodies recognizing disease-specific LSH/HELLS states

• Therapeutic opportunities:

  • Target the translocase activity that appears critical for IRC5 function

  • Screen for small molecules that modulate LSH/HELLS activity

  • Explore synthetic lethality approaches in cancers with altered LSH/HELLS expression

  • Develop antibody-based detection of LSH/HELLS as diagnostic or prognostic markers

• Model system development:

  • Create humanized yeast models expressing LSH/HELLS instead of IRC5

  • Develop high-throughput screening approaches using IRC5/LSH conservation

  • Generate specialized antibodies to detect post-translational modifications specific to human LSH/HELLS

This comparative approach leverages fundamental discoveries about IRC5 in yeast to inform understanding of human biology and disease, potentially leading to new diagnostic or therapeutic approaches .