ASF1B Antibody is a research-grade immunoglobulin designed to detect the anti-silencing function 1B (ASF1B) protein, a histone H3-H4 chaperone critical for nucleosome assembly during DNA replication and repair. This antibody enables molecular studies of ASF1B’s role in cell proliferation, cancer progression, and immune regulation. Below is a detailed analysis of its characteristics, applications, and research utility.
ASF1B Antibody is widely used to detect endogenous or overexpressed ASF1B in lysates from cancer cell lines (e.g., MCF7, HeLa, Jurkat) . For example:
Cell Signaling’s antibody enables IP to study ASF1B interactions, such as binding to cyclin-dependent kinase 9 (CDK9) in cervical cancer cells .
Abcam’s antibody visualizes ASF1B in paraffin-embedded tissues (e.g., human testis and tonsil) to assess protein localization .
Technique | Model System | Outcome | Source |
---|---|---|---|
WB | MCF7, Jurkat, HeLa cells | ASF1B detection at 22 kDa | |
IP | Cervical cancer cells | CDK9 co-precipitation | |
IHC | Human testis/tonsil | Nuclear staining |
ASF1B is a histone H3-H4 chaperone involved in DNA replication and repair, as well as transcriptional regulation. It has been identified as a crucial protein for S-phase progression and cellular proliferation, particularly in human β-cells . ASF1B is important to study because it has been implicated in various cellular processes including the cell cycle, DNA replication, base excision repair, mismatch repair, and nucleotide excision repair . Recent research has also demonstrated that ASF1B may serve as a novel proliferation marker for cancer prognosis and potentially as an immunotherapeutic target . Understanding ASF1B function provides valuable insights into both normal cellular proliferation pathways and disease mechanisms.
ASF1B antibodies are utilized in multiple research applications, including:
Immunohistochemistry (IHC) - For detecting ASF1B protein in tissue sections, with nuclear staining patterns indicating positive results. This is especially useful for evaluating expression levels in tumor versus normal tissues .
Western blot analysis - For quantifying ASF1B protein abundance in cell or tissue lysates, allowing comparison of expression levels across different experimental conditions .
Immunofluorescence - For visualizing the subcellular localization of ASF1B in conjunction with other cellular markers.
Chromatin immunoprecipitation (ChIP) - For studying ASF1B interactions with chromatin and associated proteins.
Flow cytometry - For analyzing ASF1B expression in specific cell populations, particularly in studies examining cell cycle progression .
Each application requires specific optimization of antibody dilution, incubation conditions, and detection methods.
Proper validation of ASF1B antibodies is critical for ensuring reliable experimental results. A comprehensive validation approach should include:
Specificity testing - Confirm that the antibody recognizes ASF1B and not its paralog ASF1A or other unrelated proteins. This can be accomplished through western blot analysis comparing wild-type cells with ASF1B-knockdown cells.
Positive and negative controls - Include tissue or cell samples known to express high levels of ASF1B (such as proliferating cancer cells) versus those with minimal expression.
Peptide competition assays - Pre-incubate the antibody with the immunizing peptide to confirm binding specificity.
Cross-reactivity assessment - Test the antibody against samples from multiple species if cross-species reactivity is claimed.
Reproducibility testing - Ensure consistent results across multiple experimental replicates and batches of the antibody.
For immunohistochemistry applications specifically, validation should include comparison of staining patterns with literature reports, and verification that nuclear localization is observed, consistent with ASF1B's known cellular distribution .
For optimal immunohistochemical detection of ASF1B in tissue samples, the following protocol is recommended based on published research methodologies:
Tissue preparation: Fix tissues in 10% neutral buffered formalin and embed in paraffin. Cut sections at 4-5 μm thickness.
Deparaffinization and rehydration: Standard xylene and graded alcohol series.
Antigen retrieval: Heat-induced epitope retrieval using citrate buffer (pH 6.0) is typically effective.
Blocking: Block endogenous peroxidase activity with 3% hydrogen peroxide followed by protein blocking with 5% normal serum.
Primary antibody: Apply ASF1B antibody at a dilution of 1:200 (as documented for ab235358, Abcam) . Incubate overnight at 4°C or for 1-2 hours at room temperature.
Detection system: Use an appropriate secondary antibody and detection system (HRP-polymer based systems work well).
Visualization: Develop with DAB (3,3'-diaminobenzidine) substrate.
Counterstaining: Hematoxylin counterstaining for nuclear detail.
Scoring: Evaluate based on both staining intensity (0-3 scale) and percentage of positive cells (0-3 scale), with the final score calculated as their product. Scores of 0-3 typically represent low expression, while scores >3 indicate high expression .
Nuclear staining is the expected pattern for ASF1B, and proper positive and negative controls should be included in each staining run.
Investigating the relationship between ASF1B and histone H3.3 in β-cell proliferation requires sophisticated methodological approaches using ASF1B antibodies. Based on research findings that ASF1B and histone H3.3A synergistically stimulate human β-cell proliferation , the following experimental design is recommended:
Co-immunoprecipitation (Co-IP) studies:
Use ASF1B antibodies to pull down protein complexes from β-cell lysates
Analyze the immunoprecipitates for the presence of H3.3 using specific H3.3 antibodies
Compare wild-type ASF1B with the histone binding-deficient mutant (V94R) to confirm binding dependency
Proximity ligation assays (PLA):
Apply ASF1B and H3.3 antibodies simultaneously to fixed β-cells
Use PLA probes to visualize and quantify direct protein-protein interactions in situ
Compare interaction frequencies across different cell cycle stages
ChIP-sequencing:
Perform ChIP with ASF1B antibodies followed by next-generation sequencing
Map genomic locations where ASF1B and H3.3 co-localize
Correlate these locations with transcriptionally active regions related to cell cycle regulation
Sequential immunofluorescence:
Use ASF1B antibodies in combination with H3.3, BrdU, and insulin antibodies
Quantify co-localization patterns during different phases of β-cell replication
Compare patterns in control versus ASF1B-overexpressing cells
This multi-faceted approach can elucidate the mechanistic basis for the observation that "histone binding to ASF1B is required for the induction of β-cell proliferation" and why H3.3, but not H3.1 or H3.2, specifically synergizes with ASF1B .
When studying ASF1B's role in cancer progression using antibodies, several methodological considerations must be addressed:
Tumor heterogeneity assessment:
Apply ASF1B antibodies to tissue microarrays (TMAs) containing multiple tumor regions
Evaluate spatial heterogeneity of expression within individual tumors
Compare expression patterns across different tumor grades and stages
Multiplex immunofluorescence:
Combine ASF1B antibodies with markers for proliferation (Ki-67), cell cycle (cyclins), and cancer stem cell markers
Use spectral unmixing to avoid fluorophore bleed-through
Employ digital pathology tools for quantitative multi-parameter analysis
Functional correlation studies:
Correlate ASF1B immunostaining with patient survival data
Apply multivariate analysis to control for confounding factors
Establish cutoff values for high versus low expression using ROC curve analysis
Monitoring treatment response:
Apply ASF1B antibodies to paired pre- and post-treatment samples
Evaluate changes in expression as potential biomarkers of therapeutic efficacy
Correlate with other established response markers
Technical validation for cancer studies:
Verify antibody performance across diverse tumor types
Establish protocol modifications required for tissues with high necrosis or fibrosis
Implement digital image analysis algorithms for standardized quantification
Investigating the correlation between ASF1B expression and immune cell infiltration in tumors requires specialized methodological approaches:
Multiplex immunohistochemistry/immunofluorescence:
Combine ASF1B antibodies with immune cell markers (CD4, CD8, CD20, FOXP3, CD68, etc.)
Use serial sections or multiplex platforms to visualize co-distribution patterns
Quantify spatial relationships between ASF1B+ tumor cells and immune infiltrates
Digital spatial profiling:
Apply ASF1B antibodies alongside a panel of immune markers
Perform region-specific quantification in tumor areas with varying ASF1B expression
Correlate ASF1B levels with immune cell densities and functional states
Single-cell analysis from dissociated tumors:
Use ASF1B antibodies in flow cytometry or mass cytometry (CyTOF) panels
Gate on tumor cell populations with different ASF1B expression levels
Correlate with immune cell frequencies and phenotypes from the same samples
Experimental design considerations:
Include appropriate controls (tumor margins, normal adjacent tissue)
Account for treatment history which may alter immune infiltration patterns
Stratify analyses by tumor molecular subtypes
Distinguishing between ASF1B and its paralog ASF1A requires careful experimental design and highly specific antibodies:
Antibody validation for paralog specificity:
Perform western blots on recombinant ASF1A and ASF1B proteins
Verify absence of cross-reactivity using siRNA knockdowns specific to each paralog
Test antibody specificity on tissues from knockout models if available
Comparative expression analysis:
Apply validated antibodies to tissue panels in parallel experiments
Quantify relative expression levels in different cell types and tissues
Correlate with mRNA expression data for confirmation
Functional knockdown/overexpression studies:
Selectively manipulate ASF1A or ASF1B levels and use antibodies to confirm specificity
Assess phenotypic consequences unique to each paralog
Perform rescue experiments with the non-targeted paralog
Co-immunoprecipitation for interactome comparison:
Use highly specific antibodies against each paralog for immunoprecipitation
Analyze binding partners by mass spectrometry
Identify unique and shared protein interactions
Chromatin association patterns:
Perform ChIP-seq with paralog-specific antibodies
Compare genomic binding profiles
Correlate with histone modification patterns and transcriptional activity
While both ASF1A and ASF1B function as histone chaperones, research suggests they have distinct roles. ASF1B appears more specifically involved in replication-dependent nucleosome assembly and cell proliferation, while ASF1A has broader functions in transcription regulation and cellular senescence. ASF1B overexpression specifically induces β-cell proliferation , suggesting unique proliferation-promoting functions not shared with ASF1A.
Researchers may encounter several technical challenges when working with ASF1B antibodies. Here are common issues and their solutions:
High background in immunohistochemistry:
Increase blocking time and concentration (5-10% normal serum)
Optimize antibody dilution (try 1:200-1:500 range)
Include 0.1-0.3% Triton X-100 in blocking solutions
Perform additional washing steps with 0.1% Tween-20 in buffer
Weak or absent nuclear staining:
Enhance antigen retrieval (extend time or try alternative buffers)
Reduce fixation time for future samples
Try signal amplification systems
Increase primary antibody concentration and incubation time
Non-specific bands in western blots:
Use freshly prepared samples with protease inhibitors
Optimize blocking conditions (5% non-fat milk or BSA)
Include additional washing steps
Try alternative antibody clones or lots
Inconsistent results across experiments:
Standardize tissue processing protocols
Use automated staining platforms when available
Include standard positive controls in each run
Document lot numbers and storage conditions
Cross-reactivity with other proteins:
Perform peptide competition assays
Validate results with orthogonal methods (e.g., RNA expression)
Use knockout or knockdown controls
Consider monoclonal antibodies for higher specificity
When interpreting ASF1B staining, remember that proper nuclear localization is expected, with dark brown nuclear staining under light microscopy indicating positive results .
Quantitative assessment of ASF1B expression requires standardized methods to ensure reproducibility and comparability across studies:
Scoring system for immunohistochemistry:
Implement a composite scoring system incorporating both staining intensity and percentage of positive cells
Use a 0-3 scale for staining intensity: 0 (no staining), 1 (weak), 2 (moderate), 3 (strong)
Score percentage of stained cells: 0 (0%), 1 (<25%), 2 (25-50%), 3 (>50%)
Calculate final score by multiplying intensity and percentage scores (range: 0-9)
Define expression levels: scores 0-3 as "low" and >3 as "high"
Digital image analysis:
Capture standardized digital images of stained sections
Use software algorithms to quantify nuclear staining intensity
Measure optical density values for positive nuclei
Calculate H-score (0-300) = Σ(intensity category × percentage of positive cells)
Western blot quantification:
Include loading controls (β-actin, GAPDH, or total histone H3)
Use densitometry to measure band intensity
Normalize ASF1B signal to loading control
Include calibration standards for absolute quantification
Flow cytometry approach:
Perform intracellular staining for ASF1B
Measure mean fluorescence intensity (MFI)
Compare to isotype controls
Calculate fold-change relative to control populations
The scoring method used in hepatocellular carcinoma studies (with intensity and percentage multiplication) has successfully identified prognostic differences between patient groups , suggesting it has clinical validity. For research applications requiring higher precision, digital image analysis offers more granular and objective quantification.
When using ASF1B antibodies for cell cycle analysis, several specific considerations must be addressed:
Synchronization and flow cytometry:
Synchronize cells using standard methods (serum starvation, thymidine block)
Fix and permeabilize cells with 70% ethanol or commercial fixation buffers
Co-stain with propidium iodide or DAPI for DNA content analysis
Include ASF1B antibody with compatible fluorophore for dual analysis
Gate cell populations in G1, S, and G2/M phases to assess ASF1B levels throughout the cell cycle
Live cell imaging considerations:
For living cells, consider using cell lines expressing fluorescently-tagged ASF1B
If antibody-based detection is necessary, optimize membrane permeabilization to maintain cell viability
Use low phototoxicity imaging approaches for extended time-lapse studies
BrdU incorporation studies:
Pulse cells with BrdU (typically 10-100 μM for 30-60 minutes)
Apply ASF1B antibody and anti-BrdU antibody sequentially
Use species-specific secondary antibodies with distinct fluorophores
Quantify percentage of ASF1B+/BrdU+ double-positive cells
Technical controls:
Include cell cycle phase markers (cyclin D1 for G1, PCNA for S-phase)
Use well-characterized cellular models (e.g., serum-stimulated fibroblasts)
Compare patterns with known cell cycle-regulated proteins
Research has shown that ASF1B overexpression in human islets results in a >20-fold increase in the population of cells in S phase (from ~0.5% to ~13%) with a corresponding decrease in G1 phase cells . This demonstrates ASF1B's significant impact on the G1/S transition, making proper cell cycle analysis crucial for understanding its function.
Co-immunoprecipitation (Co-IP) experiments using ASF1B antibodies require careful optimization to preserve protein-protein interactions while achieving specific pulldown:
Lysis buffer optimization:
Use gentle, non-denaturing buffers (e.g., 20 mM Tris-HCl pH 7.5, 150 mM NaCl, 1 mM EDTA, 1% NP-40)
Include protease and phosphatase inhibitors
Consider adding nuclease (benzonase or DNase I) to release chromatin-bound complexes
Maintain samples at 4°C throughout processing
Antibody selection and validation:
Test multiple antibody clones for immunoprecipitation efficiency
Confirm that the epitope recognized doesn't interfere with protein-protein interactions
Verify successful pulldown by western blot before proceeding to interaction studies
Experimental protocol:
Pre-clear lysates with protein A/G beads to reduce non-specific binding
Optimize antibody-to-lysate ratio (typically 2-5 μg antibody per 500 μg protein)
Include appropriate negative controls (IgG, isotype control)
Consider cross-linking antibody to beads to prevent antibody contamination in eluates
Detecting histone interactions:
For studying ASF1B-histone interactions, include low concentrations of detergent (0.05-0.1% NP-40)
Consider acid extraction for enriching histone fractions
Use specialized buffers for maintaining histone-chaperone interactions
Analysis of interaction partners:
Co-IP experiments have been valuable in demonstrating that histone binding to ASF1B is required for the induction of β-cell proliferation . When interpreting results, consider that some interactions may be transient or cell cycle-dependent, potentially requiring synchronized cell populations or cross-linking approaches.
Discrepancies between ASF1B mRNA and protein expression levels are not uncommon in molecular biology research. Here's a methodological framework for investigating and interpreting such discrepancies:
Technical validation:
Verify antibody specificity using positive and negative controls
Confirm primer specificity for mRNA detection
Test multiple antibody clones and RNA detection methods
Consider housekeeping gene/protein normalization strategies
Post-transcriptional regulation assessment:
Investigate miRNA targeting of ASF1B using prediction tools and functional assays
Examine RNA-binding protein interactions with ASF1B transcripts
Measure ASF1B mRNA stability through actinomycin D chase experiments
Assess translation efficiency using polysome profiling
Post-translational regulation analysis:
Evaluate ASF1B protein stability using cycloheximide chase assays
Investigate potential ubiquitination or other modifications affecting protein turnover
Examine subcellular localization differences that might affect antibody detection
Consider cell cycle-dependent regulation of protein levels
Biological interpretation:
Document the temporal relationship between mRNA and protein changes
Consider tissue-specific regulatory mechanisms
Examine cell cycle phase-specific expression patterns
Compare patterns with other histone chaperones and cell cycle regulators
When interpreting such discrepancies in a research context, consider that ASF1B protein levels may be tightly regulated through post-translational mechanisms to ensure proper coordination with cell cycle progression and histone deposition. This regulation may be particularly important in cancer contexts, where dysregulation of ASF1B has prognostic implications .
Using ASF1B antibodies to evaluate potential therapeutic targets in cancer requires careful experimental design and interpretation:
Target validation approach:
Confirm ASF1B overexpression in tumor versus matched normal tissues
Correlate expression with clinical outcomes (survival, treatment response)
Perform knockdown/knockout studies in relevant cancer models
Assess effects on cancer hallmark phenotypes (proliferation, invasion, etc.)
Patient stratification strategy:
Establish standardized IHC protocols for consistent scoring
Determine clinically relevant cutoff values for "high" versus "low" expression
Correlate with established biomarkers and molecular subtypes
Assess heterogeneity within individual tumors
Therapeutic response monitoring:
Develop protocols for measuring ASF1B changes during treatment
Compare expression in responders versus non-responders
Correlate with pharmacodynamic markers of target engagement
Evaluate in paired pre- and post-treatment samples
Combination therapy rationale:
Assess correlation between ASF1B and immune checkpoint molecules
Measure changes in immune infiltration following ASF1B modulation
Identify synergistic pathways for combination approaches
Develop companion diagnostic strategies
Research has shown that ASF1B expression is positively correlated with immune checkpoint molecules including PD-1, CTLA4, LAG3, TIM-3, and TIGIT in hepatocellular carcinoma . This suggests potential value in combining ASF1B-targeted therapies with immune checkpoint inhibitors. Additionally, the finding that patients with high ASF1B expression had a higher objective response rate to anti-PD-L1 immunotherapy (34% vs. 15%) highlights the potential of ASF1B as a predictive biomarker for immunotherapy efficacy.
Investigating the mechanistic relationship between ASF1B and cell cycle regulation requires sophisticated experimental approaches using validated antibodies:
Synchronization and temporal analysis:
Synchronize cells at different cell cycle phases (double thymidine block, nocodazole)
Collect samples at timed intervals during cell cycle progression
Perform immunoblotting with ASF1B antibodies to track protein levels
Co-stain for cyclins and other cell cycle markers for precise phase determination
Chromatin association dynamics:
Perform chromatin fractionation at different cell cycle stages
Use ASF1B antibodies to quantify chromatin-bound versus soluble fractions
Correlate with DNA replication timing (EdU pulse-labeling)
Compare wild-type ASF1B with binding-deficient mutants
Interactome analysis:
Conduct phase-specific co-immunoprecipitation with ASF1B antibodies
Identify cell cycle-regulated interaction partners
Validate key interactions with proximity ligation assays
Map interaction domains through deletion mutant analysis
Functional impact assessment:
Manipulate ASF1B levels (overexpression, knockdown) in synchronized cells
Measure effects on S-phase entry and progression
Analyze DNA content by flow cytometry
Quantify BrdU incorporation and mitotic index
Research has demonstrated that ASF1B overexpression promotes the G1/S transition, increasing the population of cells in S phase while decreasing G1 phase cells . These findings can be integrated with gene expression data showing that ASF1B overexpression leads to "distinct transcriptional signatures consistent with increased cellular proliferation" . The mechanistic studies should focus on how ASF1B, potentially through its histone chaperone activity, regulates the expression or activity of key cell cycle regulatory factors.
Studying ASF1B's role in immune cell interactions within the tumor microenvironment requires integrative experimental approaches:
Spatial analysis in tumor tissues:
Perform multiplex immunohistochemistry with ASF1B antibodies and immune cell markers
Use digital spatial profiling to quantify distances between ASF1B+ tumor cells and immune cells
Apply neighborhood analysis algorithms to identify spatial relationships
Compare patterns in immunotherapy-responsive versus resistant tumors
Co-culture functional studies:
Establish co-culture systems with ASF1B-modulated tumor cells and immune cells
Use ASF1B antibodies to track expression during co-culture
Measure functional outcomes (T cell activation, cytokine production)
Compare effects of wild-type versus mutant ASF1B
Secretome analysis:
Collect conditioned media from ASF1B-overexpressing versus control tumor cells
Analyze cytokine/chemokine profiles
Test effects on immune cell migration and function
Identify key mediators of ASF1B-dependent immune modulation
In vivo models with immune monitoring:
Establish xenograft or syngeneic models with modulated ASF1B expression
Monitor tumor growth and immune infiltration
Collect samples for immunohistochemistry with ASF1B antibodies
Test combination with immunotherapies
Based on current findings and technological trends, several promising research directions for ASF1B antibody applications include:
Development of companion diagnostics:
Standardization of ASF1B IHC for patient stratification
Creation of validated scoring algorithms with clinical cutoffs
Integration with multi-biomarker panels for enhanced predictive power
Automation of image analysis for reproducible assessment
Single-cell applications:
Adaptation of ASF1B antibodies for single-cell protein analysis
Integration with multi-omics approaches (CITE-seq, cellular indexing)
Spatial single-cell analysis in intact tissues
Tracking ASF1B expression in rare cell populations
Therapeutic targeting strategies:
Development of antibody-drug conjugates targeting ASF1B
Small molecule inhibitors disrupting ASF1B-histone interactions
Combination approaches with cell cycle inhibitors or immunotherapies
Identification of synthetic lethal interactions with ASF1B dependency
Mechanistic studies:
Investigation of post-translational modifications regulating ASF1B
Analysis of chromatin landscape changes driven by ASF1B
Exploration of non-histone interactions in specialized contexts
Comparative studies across different tumor types and normal tissues
The finding that ASF1B and histone H3.3A synergistically stimulate human β-cell proliferation opens possibilities for regenerative medicine applications, while the correlation between ASF1B and immune cell infiltration in tumors suggests potential in immuno-oncology. As molecular and cellular analytical technologies continue to advance, ASF1B antibodies will likely play an increasingly important role in both basic research and translational applications.
For comprehensive understanding of ASF1B biology, researchers should integrate antibody-based data with complementary experimental approaches:
Multi-omics integration:
Correlate protein-level data from ASF1B antibody studies with transcriptomic profiles
Integrate with chromatin accessibility data (ATAC-seq, DNase-seq)
Map ASF1B binding sites via ChIP-seq and compare with gene expression
Incorporate post-translational modification data from proteomics
Functional genomics correlation:
Combine antibody-based expression data with CRISPR/Cas9 screening results
Correlate phenotypic outcomes with ASF1B expression levels
Identify genetic dependencies associated with ASF1B status
Perform epistasis analysis with related pathway components
Structural biology integration:
Use antibody epitope mapping to inform structural studies
Correlate functional domains with antibody-detected expression patterns
Design structure-guided mutations for functional validation
Integrate with protein-protein interaction networks
Translational research integration:
Correlate antibody-based biomarker data with clinical outcomes
Integrate with pharmacodynamic biomarkers in therapeutic studies
Combine with liquid biopsy approaches for longitudinal monitoring
Incorporate with radiomics and other imaging biomarkers
ASF1B is the substrate of the tousled-like kinase family of cell cycle-regulated kinases. It cooperates with Chromatin Assembly Factor 1 (CAF-1) to stimulate replication-dependent chromatin assembly . This cooperation is essential for the proper assembly and disassembly of nucleosomes, which are the fundamental units of chromatin structure.
The anti-human ASF1B monoclonal antibody, clone PAT1D4AT, is derived from the hybridization of mouse F0 myeloma cells with spleen cells from BALB/c mice immunized with a recombinant human ASF1B protein (1-202 amino acids) purified from E. coli . The antibody is of the IgG 2b subclass with a kappa light chain .