ORC4 Antibody

What is ORC4 and what role does it play in cellular processes?

ORC4 is a vital component of the Origin Recognition Complex (ORC), which is essential for the initiation of DNA replication in eukaryotic cells. ORC4 plays a critical role in forming pre-replication complexes necessary for accurate and timely genome replication .

ORC4, along with other ORC subunits, binds to specific origins of replication, serving as a scaffold for assembling additional initiation factors. This interaction ensures DNA replication occurs at the right time during the cell cycle, particularly at the G1/S transition .

Beyond DNA replication, ORC4 has several other functions:

• Binds histone H3 and H4 trimethylation marks (H3K9me3, H3K27me3, and H4K20me3)

• Plays a role in maintaining genomic stability

• Has consistent expression throughout the cell cycle

• Participates in cell enucleation processes

Research on ORC4 provides insights into fundamental processes of cell division, genome replication, and cell cycle regulation, making it a significant target for cell biology research.

What types of ORC4 antibodies are available for different research applications?

Multiple types of ORC4 antibodies are available for research with different properties to suit various experimental needs:

When selecting an ORC4 antibody, consider:

• Target species compatibility for your experimental model

• Application requirements (WB, IP, IF, IHC, ChIP)

• Monoclonal antibodies offer greater specificity and reproducibility

• Polyclonal antibodies may provide stronger signals and recognize multiple epitopes

The diverse range of available antibodies allows selection of the most appropriate reagent for specific experimental needs.

How should ORC4 antibodies be validated for experimental use?

Proper validation of ORC4 antibodies is essential for experimental reliability. An orthogonal validation strategy is recommended, which cross-references antibody-based results with data from non-antibody methods :

Recommended Validation Methods:

• Genomic/Transcriptomic Correlation

  • Compare antibody staining patterns with ORC4 mRNA expression data from public databases

  • Verify cell lines with high ORC4 mRNA expression show stronger antibody signals than low-expressing lines

• Genetic Manipulation Controls

  • Use siRNA knockdown of ORC4 to confirm signal reduction (as demonstrated in MEL cells)

  • Consider CRISPR-Cas9 knockout of ORC4 as negative controls where feasible

  • Include overexpression systems to verify increased signal intensity

• Multiple Antibody Approach

  • Use different antibodies targeting distinct epitopes of ORC4

  • Compare staining patterns across applications (WB, IHC, IF)

  • Consistent results across different antibodies increase confidence in specificity

• Orthogonal Detection Methods

  • Compare antibody staining with in situ hybridization for ORC4 mRNA

  • Consider mass spectrometry validation of immunoprecipitated material

  • Use peptide competition assays with neutralizing peptides (e.g., "ORC4 (D-8) Neutralizing Peptide")

• Biological Context Verification

  • Verify observed patterns match known ORC4 biology (nuclear localization, cell cycle dynamics)

  • As noted in search results: "The defining criterion of success for an orthogonal strategy is consistency between the known or predicted biological role and localization of a gene/protein of interest and the resultant antibody staining"

The most robust validation combines multiple approaches to ensure the antibody specifically detects ORC4 in your experimental system.

What are the optimal conditions for using ORC4 antibodies in Western blotting?

Achieving optimal results with ORC4 antibodies in Western blotting requires attention to several technical parameters:

Recommended Dilutions by Antibody Type:

• ORC4 Polyclonal Antibody (ABIN6263904): 1:1000-1:3000

• ORC4 Polyclonal Antibody (E-AB-18803): 1:500-1:2000

• Anti-ORC4L antibody (ab9641): 0.5 µg/mL

• Anti-Orc4 (S. pombe) antibody: 1:2000

Sample Preparation Guidelines:

• Cell/Tissue Lysis: Use RIPA buffer or similar lysis buffers appropriate for nuclear proteins

• Protein Loading: 8-35 µg total protein per lane, depending on expression levels

• Molecular Weight Expectation: Human ORC4 calculated MW is approximately 50 kDa

Important Technical Considerations:

• Band Size Variation: The actual ORC4 band may not match the predicted size due to post-translational modifications, splice variants, or other factors affecting protein mobility

• Secondary Antibody Selection: Use species-appropriate HRP-conjugated secondary antibodies (e.g., goat anti-rabbit IgG for rabbit primary antibodies)

• Detection Method: ECL (Enhanced Chemiluminescence) is an effective visualization technique

• Controls: Include positive controls (cell lines with known ORC4 expression) and negative controls when possible

Verified Cell Line Samples:

• Human cell lines: HepG2, HeLa

• Mouse tissues: Heart

• S. pombe extracts

Note that different ORC4 antibodies may detect different isoforms or modified forms of the protein, which should be considered when interpreting results.

How can ORC4 antibodies be effectively used in Chromatin Immunoprecipitation (ChIP) studies?

Chromatin Immunoprecipitation (ChIP) with ORC4 antibodies requires specific optimization to study ORC4-DNA interactions at replication origins:

Antibody Selection for ChIP:

• Choose antibodies specifically validated for ChIP applications

• Anti-Orc4 (S. pombe) antibody has been documented for ChIP applications

• Polyclonal antibodies often perform well in ChIP due to recognition of multiple epitopes

Experimental Optimization:

• Crosslinking Conditions

  • Optimize formaldehyde crosslinking time (typically 10-15 minutes)

  • Consider dual crosslinking with DSG for better capture of protein-protein interactions within the ORC complex

• Chromatin Fragmentation

  • Optimize sonication to generate 200-500 bp fragments

  • Verify fragmentation efficiency by gel electrophoresis

• Cell Cycle Considerations

  • ORC4 binding to chromatin varies throughout the cell cycle

  • For maximum binding, consider synchronizing cells in G1 phase

  • Compare binding profiles across different cell cycle stages for dynamic studies

Critical Controls:

• Input Control: Crucial for normalization of enrichment

• Negative Control: IgG from the same species as the ORC4 antibody

• Positive Control Regions: Known replication origins where ORC4 binding is expected

• Validation: Confirm findings using alternative methods or multiple ORC4 antibodies

Notable Applications:

The Takahashi et al. study used anti-Orc4 antibody in ChIP experiments to demonstrate that "multiple ORC-binding sites are required for efficient MCM loading and origin firing in fission yeast" , highlighting the utility of this approach for studying replication origin biology.

What is the relationship between ORC4 expression and immune cell infiltration in cancer research?

Recent research has revealed unexpected correlations between ORC4 expression and immune cell infiltration in cancer contexts, particularly in Lung Adenocarcinoma (LUAD) :

ORC4 Correlations with Immune Cell Populations:

These correlations suggest ORC4 may influence the tumor immune microenvironment beyond its canonical role in DNA replication .

Comparative Analysis with Other ORC Subunits:

• ORC5 showed significant correlations with B cells, CD8+ T cells, CD4+ T cells, and neutrophils

• ORC6 correlated with B cells, CD4+ T cells, macrophages, and dendritic cells

• Different ORC subunits appear to have distinct relationships with immune cell populations

Research Implications:

• Prognostic Potential: ORC4 expression patterns might serve as biomarkers for immune infiltration status

• Therapeutic Relevance: Understanding ORC4-immune relationships could inform immunotherapy approaches

• Mechanistic Questions: Further research is needed to determine whether these relationships are causal or merely associative

This finding opens new avenues for investigating how DNA replication proteins may interact with or influence immune response in cancer contexts.

What role does ORC4 play in cellular enucleation and how can antibodies help study this process?

Beyond its canonical role in DNA replication, ORC4 has been identified as a key player in cellular enucleation processes, particularly in erythrocyte development :

ORC4's Novel Role in Enucleation:

Research on Murine Erythroleukemia (MEL) cells has revealed that:

• ORC4 forms a structure around the nuclei of MEL cells during Vacuolin-1-induced enucleation

• This ORC4 layer gradually increases in thickness before nuclear expulsion

• Downregulation of ORC4 with siRNA prevented MEL enucleation, demonstrating its functional requirement

Similar Function in Other Systems:

• ORC4 plays a vital role in polar body extrusion (PBE) during oogenesis

• In both contexts, ORC4 appears to form structures around nuclear material being extruded

• This represents a conserved mechanism for nuclear material elimination across different cell types

Antibody-Based Research Approaches:

• Immunofluorescence Studies

  • Track ORC4 localization during enucleation using specific antibodies

  • Time-course experiments to establish the temporal relationship between ORC4 accumulation and nuclear expulsion

  • Co-localization with cytoskeletal markers to understand mechanical aspects

• Functional Studies

  • Combine siRNA knockdown with ORC4 antibody staining to correlate protein levels with enucleation efficiency

  • Compare ORC4 dynamics in different enucleating cell types using standardized protocols

• Molecular Interactions

  • Immunoprecipitation with ORC4 antibodies during enucleation to identify novel interaction partners

  • Western blotting to quantify ORC4 protein levels throughout the process

This non-canonical role represents an exciting area for ORC4 antibody-based research, potentially revealing new therapeutic targets for diseases involving aberrant nuclear retention or elimination.

How should researchers approach multiplexing ORC4 antibodies with other replication complex antibodies?

Effective multiplexing of ORC4 antibodies with antibodies against other replication factors requires careful planning:

Antibody Selection Strategies:

• Host Species Diversity

  • Select primary antibodies from different host species (e.g., rabbit anti-ORC4 with mouse anti-MCM2)

  • Available options include mouse monoclonal , rabbit polyclonal , and goat polyclonal ORC4 antibodies

• Isotype Consideration

  • When using antibodies from the same host, use different isotypes (e.g., IgG vs. IgM)

  • Search results mention an IgM κ mouse monoclonal ORC4 antibody that could be paired with IgG antibodies

• Fluorophore Selection

  • Choose fluorophores with minimal spectral overlap

  • Consider brightness matching for balanced visualization

Critical Controls:

• Single-Staining Controls

  • Perform single-antibody staining to establish baseline signals

  • Include secondary-only controls for each channel

  • Use isotype controls matched to each primary antibody

• Validation Controls

  • Confirm specificity using neutralizing peptides where available (e.g., "ORC4 (D-8) Neutralizing Peptide")

  • Use orthogonal validation approaches for each antibody in the multiplex panel

Recommended Antibody Combinations:

• ORC4 + MCM Proteins

  • Study pre-replication complex assembly

  • Example: Combine rabbit anti-ORC4 with mouse anti-MCM2

• ORC4 + Other ORC Subunits

  • Analyze complete ORC complex formation

  • Example: Combine rabbit anti-ORC4 with mouse antibodies against other ORC subunits

• ORC4 + Cell Cycle Markers

  • Correlate with specific cell cycle phases

  • Example: ORC4 + cyclins or phospho-specific markers

This methodical approach ensures reliable and reproducible co-localization data when studying ORC4 in context with other replication machinery components.

How do ORC4 antibodies compare in detection sensitivity across different applications?

Different ORC4 antibodies show varying performance characteristics across applications:

Comparative Performance by Application:

Sensitivity Considerations:

• Western Blotting

  • Most ORC4 antibodies perform well in Western blotting

  • Predicted band size is 50 kDa, but actual band may vary due to post-translational modifications

  • Some antibodies show cleaner background than others

• Immunofluorescence/Immunohistochemistry

  • ORC4 (D-8) antibody has been validated for IF

  • E-AB-18803 has been validated for IHC with human tissue samples

  • Optimal dilutions for IF/IHC typically range from 1:50-1:300

• Immunoprecipitation

  • ORC4 (D-8) and S. pombe anti-Orc4 antibodies have demonstrated IP capability

  • IP efficiency may vary depending on cell type and lysis conditions

• ChIP Applications

  • Anti-Orc4 (S. pombe) antibody has been successfully used in ChIP studies

  • Other antibodies may require additional validation for ChIP applications

When selecting an ORC4 antibody, researchers should prioritize those with validation data for their specific application and experimental system.

What are the methodological considerations for studying ORC4 mutations in human diseases?

ORC4 mutations have been implicated in various human diseases, requiring specific methodological approaches:

Disease Associations:

Current research has linked ORC mutations (including ORC4) to several diseases:

• Meier-Gorlin syndrome

• Potential connections to AML and MDS (though specific ORC4 mutations were not detected)

• Possible involvement in testicular disorders (ORCA/LRWD1, which interacts with ORC components)

Methodological Approaches:

• Mutation Detection Strategies

  • Targeted Sequencing: For known ORC4 mutations in patient cohorts

  • Whole Exome/Genome Sequencing: To identify novel ORC4 variants

  • RNA-Seq: To detect altered splicing or expression patterns

• Functional Validation

  • Cell-Based Assays: Reconstitute mutant ORC4 in appropriate cell systems

  • DNA Replication Assays: Measure impact on replication origin licensing

  • Protein Interaction Studies: Determine effects on ORC complex assembly

• Antibody-Based Applications

  • Mutation-Specific Antibodies: Consider developing antibodies against common ORC4 mutations

  • Expression Analysis: Use existing ORC4 antibodies to study expression patterns in disease tissues

  • Localization Studies: Analyze subcellular distribution of mutant ORC4 proteins

• Disease Modeling

  • CRISPR-Edited Cell Lines: Create isogenic models with specific ORC4 mutations

  • Patient-Derived Cells: Study primary cells from affected individuals

  • Animal Models: Develop models with orthologous ORC4 mutations

Clinical Research Considerations:

• Tissue-Specific Effects: ORC4 mutations may affect certain tissues differently

• Genotype-Phenotype Correlations: Different mutations may cause distinct clinical manifestations

• Therapeutic Implications: Understanding mechanisms may reveal targeted therapeutic approaches

As noted in the literature: "These reports clearly suggest that individual mutations in ORC subunits and related factors are involved, directly or indirectly, in many human diseases. Further functional demonstrations on these correlations will be highly desired" .