chfr Antibody

What is CHFR and what molecular functions does it perform in cell cycle regulation?

CHFR is a 72-80 kDa protein that functions as a tumor suppressor by regulating the antephase checkpoint, which controls entry into mitosis . As an E3-ubiquitin-ligase, CHFR plays a key role in maintaining genomic stability through several mechanisms:

• Controlling the activity of aurora-kinase A and polo-like kinase 1

• Excluding cyclin B1 from the nucleus, thereby preventing premature mitotic entry

• Regulating PARP-1 levels through ubiquitination

CHFR contains multiple functional domains, with the cysteine-rich (CR) region being essential for its interaction with PARP-1 . Recent research has identified a zinc-finger motif in the C-terminal region that serves as a poly-ADP-ribose-binding site, further establishing CHFR's role in the DNA damage response pathway . CHFR deficient cells show heightened sensitivity to microtubule-damaging agents, demonstrating its importance in managing mitotic stress .

How can researchers effectively detect CHFR protein expression in experimental samples?

Detection of CHFR protein requires careful selection of antibodies and optimization of protocols. Based on current research methodologies:

Western Blotting

Western blotting represents a primary method for CHFR detection in cell and tissue lysates:

• Recommended dilution: 1:1000 for standard western blotting applications

• Expected molecular weight: 80 kDa (human CHFR)

• Positive controls: CHFR-proficient cell lines such as 293T cells

• Negative controls: CHFR-deficient cell lines such as HeLa or HCT116 cells

Immunoprecipitation

For protein interaction studies:

• Recommended dilution: 1:50

• Can be used to study CHFR interactions with binding partners such as PARP-1

Immunohistochemistry (IHC)

For tissue section analysis:

• Use monoclonal-rabbit CHFR antibody (e.g., Clone D40H6) at 1:200 dilution

• Standard antigen retrieval steps are essential for optimal staining

• Both nuclear and cytoplasmic staining should be assessed

• Scoring system: Based on intensity (0=none, 1=weak, 2=strong) and percentage of cells staining (0 < 10%; 1: 10–50%; 2>50%)

What are the challenges in validating CHFR antibody specificity?

Validating antibody specificity is critical due to historical challenges with CHFR detection. Researchers should implement multiple validation strategies:

• Perform parallel testing in CHFR-proficient (e.g., 293T) and CHFR-deficient (e.g., HeLa, HCT116) cell lines

• Include genetic validation through CHFR knockdown/knockout models

• Confirm antibody specificity through reconstitution experiments (e.g., detection of strong nuclear staining in HeLa cells reconstituted with wild-type CHFR)

• Validate correlation between protein detection and mRNA levels through RT-PCR

Research has shown that monoclonal antibodies against CHFR have superior specificity compared to polyclonal alternatives, with several antibodies recognizing endogenous CHFR in appropriate control cells while showing minimal cross-reactivity .

What is the significance of CHFR cross-reactivity across species?

CHFR antibodies demonstrate variable cross-reactivity patterns that researchers should consider when designing experiments:

How does CHFR protein interact with PARP-1, and what methods can be used to study this interaction?

The CHFR-PARP-1 interaction represents a critical regulatory mechanism in the mitotic checkpoint pathway. Research findings indicate:

• CHFR interacts with PARP-1 primarily through its CR (cysteine-rich) region

• The automodification domain (AD) of PARP-1 is required for interaction with CHFR

• PARP-1 mutants lacking both DNA-binding domain (DBD) and AD cannot bind to CHFR

To study this interaction, researchers should consider:

• Co-immunoprecipitation assays with FLAG-tagged CHFR and endogenous PARP-1

• Domain mapping experiments using deletion mutants of both proteins

• Polyubiquitination assays to detect CHFR-mediated ubiquitination of PARP-1

• Functional studies to evaluate how this interaction affects the antephase checkpoint

Notably, when CHFR mutants lacking E3 ubiquitin ligase activity are used, greater amounts of PARP-1 binding are observed, suggesting that CHFR's enzymatic activity affects the stability of this interaction .

What are the appropriate scoring methods for CHFR immunohistochemistry in clinical samples?

For clinical research applications, standardized scoring systems are essential:

• CHFR staining should be evaluated for both nuclear and cytoplasmic localization

• Intensity scoring: 0 (no staining), 1 (weak staining), 2 (strong staining)

• Percentage scoring: 0 (<10% cells), 1 (10–50% cells), 2 (>50% cells)

• Combined score: Sum of intensity and percentage scores (maximum score of 4)

• Cut-off determination: Receiver operator characteristics (ROC) analysis can determine optimal thresholds

• Interpretation: Scores of '4' typically considered "high" expression, while others indicate "reduced" expression

Pathologist blinding to clinical outcomes is essential for unbiased scoring. Digital image analysis can provide supplementary quantitative assessment to reduce inter-observer variability.

How can CHFR expression be correlated with treatment response in cancer research?

CHFR expression has emerged as a potential predictive biomarker for response to taxane-based therapies:

• CHFR deficiency is associated with enhanced sensitivity to taxanes in gastric and cervical cancer models

• CHFR-deficient cells exhibit elevated mitotic stress after exposure to microtubule-damaging agents

• Clinical correlation requires:

  • Standardized CHFR detection methods (IHC or methylation-specific PCR)

  • Comprehensive clinical data collection

  • Statistical analysis using Chi-Square tests and Cox proportional models

  • Determination of appropriate cutoff values for "high" versus "low" expression

In clinical studies, anti-CHFR antibody-positive patients showed significantly different response patterns compared to antibody-negative patients, highlighting the potential prognostic value of CHFR status assessment .

What methods can detect epigenetic silencing of CHFR in cancer samples?

CHFR is frequently silenced through DNA methylation rather than mutations in cancer:

• Methylation-specific PCR (MS-PCR) represents the standard approach:

  • Extract DNA from FFPE (formalin-fixed paraffin-embedded) samples

  • Quantify DNA content using standard photometric methods

  • Perform sodium bisulfite modification on 250 ng of DNA

  • Conduct 2-step MS-PCR using CHFR-specific primers

  • Include appropriate methylated and unmethylated controls

Correlation between CHFR methylation status and protein expression levels can provide comprehensive insight into the mechanism of CHFR dysregulation in specific cancer types.

What are the critical factors in optimizing experimental protocols for CHFR antibody applications?

Optimization considerations include:

Western Blotting

• Sample preparation: Complete cell lysis in the presence of protease inhibitors

• Protein loading: 20-40 μg of total protein per lane

• Antibody concentration: 1:1000 dilution typically provides optimal signal-to-noise ratio

• Secondary antibody selection: HRP-conjugated anti-rabbit IgG at 1:1000-1:5000 dilution

• Controls: Include CHFR-positive and CHFR-negative cell lines

Immunohistochemistry

• Antigen retrieval: Critical for FFPE samples to unmask epitopes

• Blocking: Thorough blocking to minimize non-specific binding

• Antibody incubation: Typically overnight at 4°C

• Detection system: Standard HRP-labeled secondary antibody systems at 1:1000 dilution

• Counterstaining: Light hematoxylin counterstaining to visualize nuclei without obscuring CHFR signal

How does CHFR contribute to the antephase checkpoint in response to taxane-induced mitotic stress?

CHFR mediates the antephase checkpoint through multiple mechanisms:

• As an E3-ubiquitin-ligase, CHFR targets key mitotic regulators for degradation

• CHFR regulates aurora-kinase A and polo-like kinase 1 activity, preventing premature mitotic entry

• CHFR-PARP1 interactions are required for checkpoint function in response to taxane-induced stress

• Cells lacking CHFR bypass this checkpoint, entering mitosis despite microtubular damage

This mechanistic understanding explains preclinical observations that CHFR-deficient cells show enhanced sensitivity to microtubule-targeting agents like taxanes. In mouse models, CHFR deficiency leads to spontaneous malignancies and increased susceptibility to chemical carcinogenesis, emphasizing its tumor suppressor function .