ABRAXAS2 Antibody

What is ABRAXAS2 and why is it important in cellular research?

ABRAXAS2 is a component of the BRISC complex, a multiprotein complex that specifically cleaves 'Lys-63'-linked polyubiquitin chains, leaving the last ubiquitin chain attached to substrates. In humans, the canonical protein is 415 amino acids with a molecular weight of approximately 46.9 kDa . It is localized in both the nucleus and cytoplasm and is notably expressed in heart muscle .

This protein plays several critical roles:

• Acts as a central scaffold for the BRISC complex in the cytoplasm

• Regulates apoptosis via modulation of K63-linked ubiquitination

• Required for normal mitotic spindle assembly and microtubule attachment to kinetochores

• Participates in interferon signaling through deubiquitination of the IFNAR1 receptor

• Limits break-induced replication (BIR) to protect genomic stability

• Contributes to p53/TP53 induction in response to DNA damage

What types of applications are suitable for ABRAXAS2 antibodies?

ABRAXAS2 antibodies can be utilized across multiple research applications, with varying validation levels:

When selecting an antibody, always verify which applications it has been validated for, as performance varies significantly between different applications and manufacturers .

What is the difference between ABRAXAS2 and ABRAXAS1, and how does this affect antibody selection?

ABRAXAS2 and ABRAXAS1 are paralogous proteins that function in distinct cellular complexes:

For antibody selection:

• Choose antibodies targeting unique regions not conserved between the paralogs

• Validate specificity using appropriate controls (ideally ABRAXAS2 knockout cells)

• Consider using antibodies that have been explicitly tested for cross-reactivity

How can I optimize Western blotting protocols for ABRAXAS2 detection?

Successful detection of ABRAXAS2 by Western blotting requires specific optimization:

Sample Preparation:

• Use RIPA buffer supplemented with protease and phosphatase inhibitors

• Include deubiquitinase inhibitors (N-ethylmaleimide) to preserve ubiquitinated forms

• Heat samples at 95°C for 5 minutes in reducing Laemmli buffer

Gel Electrophoresis and Transfer:

• 10-12% SDS-PAGE gels are optimal for resolving the ~47 kDa ABRAXAS2 protein

• Load 20-50 μg of total protein per lane for endogenous detection

• PVDF membranes generally yield better results than nitrocellulose

• Verify transfer efficiency with reversible staining (Ponceau S)

Antibody Incubation and Detection:

• Block with 5% non-fat dry milk in TBST for 1 hour at room temperature

• Primary antibody dilutions typically range from 1:500 to 1:2000

• Incubate with primary antibody overnight at 4°C

• Expected band size: ~47 kDa (canonical form)

Validation Controls:

• Include positive control lysates from cells with known ABRAXAS2 expression

• Use ABRAXAS2 knockdown/knockout samples as negative controls

• Consider antibodies validated in publications with proper controls

How should I approach studying ABRAXAS2's role in limiting break-induced replication (BIR)?

ABRAXAS2 plays a crucial role in limiting single-ended double-strand breaks (seDSBs) from undergoing BIR-dependent mitotic DNA synthesis . To effectively study this function:

Experimental Design Strategy:

• Camptothecin (CPT) Treatment Paradigm:

  • Use CPT to induce TOP1-DNA cleavage complexes that transform into seDSBs upon replication

  • Monitor ABRAXAS2 recruitment to damage sites using immunofluorescence

  • Compare wild-type and ABRAXAS2-deficient cells for differences in response

• Mitotic DNA Synthesis Quantification:

  • Use EdU labeling in mitotic cells to detect BIR events

  • Quantify EdU incorporation in ABRAXAS2-knockdown versus control cells

  • Co-stain with phospho-histone H3 to identify mitotic cells

• Analysis of SLX4/MUS81 Recruitment:

  • ABRAXAS2 restricts SLX4/MUS81 recruitment to CPT damage sites

  • Use co-immunofluorescence to assess colocalization patterns

  • Perform chromatin fractionation followed by Western blotting to quantify recruitment

• K63-Ubiquitin Modification Analysis:

  • ABRAXAS2 counteracts K63-linked ubiquitin modification

  • Use K63-specific ubiquitin antibodies to detect modification status of targets

  • Compare ubiquitination patterns in wild-type versus ABRAXAS2-knockout cells

The key methodological insight is that ABRAXAS2 deficiency leads to increased mitotic DNA synthesis via RAD52- and POLD3-dependent, RAD51-independent BIR and extensive chromosome aberrations .

What controls are essential when investigating ABRAXAS2's role in interferon signaling?

When studying ABRAXAS2's role in interferon signaling through IFNAR1 deubiquitination, include these critical controls:

Genetic and Molecular Controls:

• ABRAXAS2 Knockout/Knockdown Validation:

  • Verify knockout/knockdown efficiency by Western blot

  • Include both protein and mRNA level confirmation

  • Use multiple siRNA sequences to rule out off-target effects

• Pathway Component Controls:

  • IFNAR1 receptor knockout cells (primary target of ABRAXAS2-mediated deubiquitination)

  • BRCC36 inhibition/depletion (catalytic component of BRISC)

  • SHMT2 knockdown (regulates BRISC-SHMT2 interaction)

• Functional Readout Controls:

  • Measure multiple interferon-stimulated genes (ISGs) as readouts

  • Include type II interferon (IFN-γ) treatment as specificity control

  • Time-course experiments to capture dynamic changes in ABRAXAS2 localization

Technical Controls for Antibody-Based Detection:

• Monitor both cell surface and total IFNAR1 levels

• Use flow cytometry to quantify IFNAR1 surface expression

• Perform parallel detection with multiple ABRAXAS2 antibodies targeting different epitopes

Research has shown that ABRAXAS2, through the BRISC complex, deubiquitinates IFNAR1, enhancing its stability and cell surface expression, thereby regulating interferon signaling .

How can I investigate ABRAXAS2's involvement in DNA damage response using advanced imaging approaches?

To effectively visualize ABRAXAS2's role in DNA damage response, consider these advanced imaging approaches:

Immunofluorescence Optimization for DNA Damage Studies:

Research indicates ABRAXAS2 restricts SLX4/MUS81 recruitment to camptothecin damage sites for cleavage and subsequent resection processed by MRE11 endonuclease, CtIP, and DNA2/BLM .

What strategies can be employed to validate ABRAXAS2 antibody specificity?

Given the critical importance of antibody specificity in research, employ these validation strategies:

Comprehensive Validation Approach:

• Genetic Controls:

  • CRISPR/Cas9-mediated knockout of ABRAXAS2 as gold-standard negative control

  • siRNA-mediated knockdown with multiple independent sequences

  • Rescue experiments with siRNA-resistant ABRAXAS2 constructs

• Biochemical Validation:

  • Peptide competition assays using the immunizing peptide

  • Pre-absorption tests with recombinant ABRAXAS2 protein

  • Sequential immunoprecipitation to confirm specificity

• Cross-reactivity Assessment:

  • Test reactivity in ABRAXAS1-deficient cells (the closest paralog)

  • Evaluate detection in different species with known sequence variations

  • Perform Western blots under reducing and non-reducing conditions

• Application-Specific Controls:

  • For IF: Include secondary antibody-only controls and autofluorescence controls

  • For WB: Run gradient gels to resolve potential isoforms or cleavage products

  • For IP: Use IgG controls and validate pulled-down protein by mass spectrometry

The most rigorous validation includes demonstrating loss of signal in genetic knockout models across multiple experimental applications .

How do I address non-specific binding issues with ABRAXAS2 antibodies?

Non-specific binding can significantly impact experimental interpretation. Here's a systematic approach to address this issue:

Common Issues and Solutions:

Protocol Optimization Strategies:

• Blocking Optimization:

  • Compare different blocking agents (5% milk, 3-5% BSA, normal serum)

  • Extend blocking time from 1 hour to overnight at 4°C

  • Add 0.1-0.3% Triton X-100 to blocking buffer for IF to improve penetration

• Antibody Dilution Series:

  • Perform titration experiments to determine optimal concentration

  • Test a range of dilutions (e.g., 1:100, 1:500, 1:1000, 1:2000)

  • Optimize incubation time and temperature

• Washing Protocol Enhancement:

  • Increase number and duration of wash steps

  • Try different detergent concentrations in wash buffer

  • Consider using PBS-T (PBS + 0.1% Tween-20) versus TBS-T

Whenever possible, confirm antibody specificity using multiple techniques and directly compare results with ABRAXAS2-deficient samples .

How can I distinguish between ABRAXAS2's BRISC-dependent and independent functions in experimental settings?

ABRAXAS2 functions both within the BRISC complex and independently in DNA damage response . To distinguish these activities:

Experimental Separation Strategy:

• Protein Complex Analysis:

  • Use size exclusion chromatography or glycerol gradient centrifugation to separate BRISC-associated ABRAXAS2 from free ABRAXAS2

  • Western blot fractions with validated ABRAXAS2 antibodies

  • Co-blot for other BRISC components (BRCC36, MERIT40, BRCC45)

• Mutant ABRAXAS2 Constructs:

  • Design mutants that selectively disrupt BRISC complex formation but maintain DNA damage response capabilities

  • Validate expression levels by immunoblotting with ABRAXAS2 antibodies

  • Assess function in relevant assays (interferon signaling vs. DNA damage response)

• Context-Dependent Protein Interactions:

  • Perform co-immunoprecipitation with ABRAXAS2 antibodies under different conditions:

    • Untreated cells (baseline interactions)

    • Interferon-treated cells (BRISC-dependent interactions)

    • DNA damage-induced cells (potential BRISC-independent interactions)

  • Identify interaction partners by mass spectrometry

• Functional Readouts:

  • K63-linked deubiquitination assays reflect BRISC complex activity

  • p53 stabilization assays indicate BRISC-independent functions

  • IFNAR1 surface expression monitors BRISC-dependent effects on interferon signaling

Research has shown that independent of the BRISC complex, ABRAXAS2 promotes interaction between USP7 and p53/TP53, leading to p53 deubiquitination and increased p53-dependent apoptosis in response to DNA damage .

What methodological approaches are most effective for studying ABRAXAS2 molecular glue inhibitors?

Recent research has identified molecular glue inhibitors that specifically target the BRISC complex containing ABRAXAS2 . To effectively study these:

Experimental Approaches:

• Biochemical Deubiquitination Assays:

  • Use K63-linked di-ubiquitin substrates with internally-quenched fluorophores

  • Monitor fluorescence increase after DUB cleavage as continuous activity readout

  • Test dose-dependent inhibition to determine IC50 values

• Structural Characterization:

  • Mass photometry to detect BRISC complex oligomerization states

  • Assess inhibitor-induced conformational changes using negative stain electron microscopy

  • Perform cryo-electron microscopy to determine high-resolution structures of inhibitor-bound BRISC complexes

• Selectivity Profiling:

  • Compare inhibition of BRISC vs. ARISC complexes (which share BRCC36 but contain ABRAXAS1 instead of ABRAXAS2)

  • Test effects on minimal BRCC36-ABRAXAS2 complexes vs. complete BRISC

  • Evaluate activity against other JAMM/MPN DUB family members

• Cellular Validation:

  • Generate structure-guided inhibitor-resistant mutants

  • Monitor interferon-stimulated gene expression changes

  • Assess effects on IFNAR1 ubiquitination and stability

Recent research demonstrates that BRISC inhibitors can stabilize an autoinhibited BRISC dimer conformation, providing a unique approach to selectively target this complex over related complexes with the same catalytic subunit .