irf2bp2a Antibody

What is irf2bp2a and what is its primary function in hematopoiesis?

Irf2bp2a (Interferon regulatory factor 2 binding protein 2a) functions primarily as a ubiquitin E3 ligase that regulates terminal granulopoiesis in zebrafish. Unlike its traditional characterization as a transcription corepressor, mechanistic studies have revealed that irf2bp2a mediates the proteasomal degradation of Gfi1aa, a key transcription repressor governing neutrophil maturation. The deficiency of irf2bp2a significantly impairs neutrophil differentiation, as evidenced by reduced expression of neutrophil markers including myeloperoxidase (mpx), lysozyme C (lyz), and c/ebp1 .

In zebrafish models, irf2bp2a deficiency leads to decreased neutrophil development from 22 hours post-fertilization (hpf) to 5 days post-fertilization (dpf). Importantly, this defect is specific to neutrophils, with other hematopoietic lineages remaining unaffected. The remaining neutrophils in irf2bp2a-deficient embryos show reduced signal intensity for markers like GFP and Sudan Black staining, suggesting incomplete differentiation .

How do irf2bp2a and irf2bp2b differ functionally despite their structural similarities?

Despite having nearly identical functional domains, irf2bp2a and irf2bp2b exhibit distinct roles in myelopoiesis:

This functional divergence explains why irf2bp2a mRNA cannot rescue the defective myelopoiesis in irf2bp2b-deficient zebrafish. While both proteins can degrade Gfi1aa when expressed in HEK293 cells, their in vivo roles remain distinct, with irf2bp2a functioning specifically in neutrophil differentiation and irf2bp2b affecting neutrophil-macrophage progenitor (NMP) cell fate choice .

What critical domains in irf2bp2a enable its E3 ligase function?

Irf2bp2a contains two critical functional domains that contribute to its E3 ligase activity:

• C4 zinc finger domain (N-terminal): Enables homo or hetero-dimerization/multimerization between IRF2BP2 family members. Mutation of critical cysteines (C14/17A) in this domain abolishes multimerization and DNA binding properties .

• C3HC4 ring finger domain (C-terminal): Mediates binding with interacting proteins and is characteristic of E3 ubiquitin ligases. Mutation of key cysteines (C409/413A) disrupts this interaction capability .

Experimental evidence demonstrates that the ring finger domain is essential for irf2bp2a's ability to mediate Gfi1aa degradation. When the ring finger is mutated (RM mutant), irf2bp2a loses its ability to promote Gfi1aa ubiquitination and subsequent proteasomal degradation. This domain-specific functionality is crucial for understanding the mechanism by which irf2bp2a regulates neutrophil development .

What are the optimal conditions for using anti-irf2bp2a antibodies in Western blot applications?

For optimal Western blot detection of irf2bp2a, researchers should consider the following protocol:

• Sample preparation: Based on experimental evidence with IRF2BP2 antibodies, cell lysates from A549, HeLa, or K-562 cells serve as effective positive controls .

• Antibody dilution: A recommended dilution range of 1:5000-1:50000 provides optimal signal-to-noise ratio for Western blot applications . The wide range allows researchers to adjust based on expression levels in their specific system.

• Detection method: Standard chemiluminescence systems are suitable, though enhanced systems may be preferred for detecting endogenous levels in certain cell types.

• Molecular weight verification: The expected molecular weight of full-length irf2bp2a should be confirmed. When analyzing potential mutants, consider that truncated proteins (like the 122 amino acid mutant described in the literature) will appear at lower molecular weights .

• Controls: Include positive controls (cells known to express irf2bp2a) and negative controls (knockdown or knockout samples if available) to validate antibody specificity.

How can researchers effectively optimize immunoprecipitation protocols for irf2bp2a studies?

For successful immunoprecipitation (IP) of irf2bp2a:

• Antibody amount: Use 0.5-4.0 μg of antibody for 1.0-3.0 mg of total protein lysate . Titrating the antibody amount can help determine optimal conditions for your specific cell type.

• Cell model selection: K-562 cells have been validated for successful IP of irf2bp2a/IRF2BP2 . Consider using these cells as positive controls when establishing the protocol in a new system.

• Lysis conditions: Use RIPA buffer supplemented with protease inhibitors and, if studying ubiquitination, add deubiquitinase inhibitors like N-ethylmaleimide.

• Co-IP partners detection: When investigating irf2bp2a interaction with proteins like Gfi1aa, consider including proteasome inhibitor MG132 (10μM for 6-8 hours) in cell culture prior to lysis, as demonstrated in experimental studies .

• Validation strategy: Perform reciprocal IP (e.g., IP with anti-Gfi1aa and blot for irf2bp2a) to confirm protein-protein interactions.

The experimental approach used to demonstrate irf2bp2a-mediated ubiquitination of Gfi1aa involved transfecting HEK293 cells with HA-Gfi1aa, Ubiquitin (Ub), and FLAG-irf2bp2a, followed by IP with anti-HA antibody and western blot detection with anti-Ubiquitin antibody . This methodology can be adapted for studying other potential substrates.

What are the critical parameters for immunohistochemical detection of irf2bp2a in tissue samples?

For optimal immunohistochemical (IHC) detection of irf2bp2a:

• Antibody dilution: A dilution range of 1:500-1:2000 has been validated for IHC applications .

• Antigen retrieval: Two validated methods include:

  • TE buffer pH 9.0 (preferred method)

  • Citrate buffer pH 6.0 (alternative method)

• Positive control tissues: While specific data for irf2bp2a is limited, IRF2BP2 antibodies have been tested on human lung squamous cell carcinoma tissue and human liver cancer tissue . For zebrafish studies, embryonic tissues at 22-48 hpf can be used based on documented expression patterns.

• Detection system: Standard avidin-biotin or polymer-based detection systems are suitable, with DAB as the chromogen.

• Counterstaining: Use hematoxylin for nuclear counterstaining to facilitate assessment of subcellular localization, as irf2bp2a localization can be informative about its function.

• Validation approaches: Perform parallel staining with multiple antibodies targeting different epitopes of irf2bp2a, and include appropriate negative controls (primary antibody omission, isotype controls, and ideally knockout tissue if available).

How can researchers design experiments to investigate the E3 ligase activity of irf2bp2a?

A comprehensive approach to investigating irf2bp2a E3 ligase activity includes:

• In vitro ubiquitination assays:

  • Purify recombinant irf2bp2a and potential substrates (e.g., Gfi1aa)

  • Combine with E1, E2 enzymes, ubiquitin, and ATP

  • Detect ubiquitination by Western blot with anti-ubiquitin antibodies

  • Include controls with mutated irf2bp2a (C409/413A ring finger mutant)

• Cell-based degradation assays:

  • Co-transfect cells with tagged irf2bp2a and substrate proteins

  • Treat cells with cycloheximide to inhibit new protein synthesis

  • Monitor substrate levels over time by Western blot

  • Compare with proteasome inhibitors (MG132) to confirm proteasomal degradation pathway

• Domain mutation studies:

  • Generate irf2bp2a constructs with specific mutations in functional domains:

    • C14/17A (zinc finger mutant)

    • C409/413A (ring finger mutant)

  • Test these mutants in rescue experiments in irf2bp2a-deficient models

  • Complementary approach: fuse tetramerization motifs (e.g., P53 tetramerization domain) to restore multimerization capacity of zinc finger mutants

• In vivo validation:

  • Use morpholino knockdown of potential substrates in irf2bp2a-deficient zebrafish

  • Assess rescue of phenotypes using markers like mpx, lyz, and c/ebp1

  • Implement genetic crosses with substrate knockout lines (e.g., gfi1aa -/- zebrafish) to confirm epistatic relationships

The experimental evidence shows that the ring finger domain mutant of irf2bp2a fails to degrade Gfi1aa, confirming the importance of this domain for E3 ligase activity .

What are the most effective methods for studying the irf2bp2a-Gfi1aa regulatory feedback loop?

The irf2bp2a-Gfi1aa regulatory axis represents a negative feedback loop where Gfi1aa represses irf2bp2a transcription while irf2bp2a promotes Gfi1aa protein degradation. To study this complex relationship:

• Promoter analysis and reporter assays:

  • Clone the irf2bp2a promoter region (e.g., 2.1kb upstream) into luciferase reporter vectors

  • Co-transfect with Gfi1aa expression vectors

  • Measure relative luciferase activity to quantify repression effects

• Chromatin immunoprecipitation (ChIP):

  • Express tagged Gfi1aa in relevant cell types or zebrafish embryos

  • Perform ChIP with antibodies against the tag (e.g., anti-GFP for Gfi1aa-GFP)

  • Include controls like untagged GFP and Gfi1aa with deleted zinc finger domain

  • Use PCR to detect enrichment of irf2bp2a promoter sequences in immunoprecipitated chromatin

• Gene expression analysis in sorted cell populations:

  • Isolate specific cell populations (e.g., mpx+ cells) from wild-type and mutant embryos using FACS

  • Perform RT-qPCR to measure relative expression levels of irf2bp2a and Gfi1aa

  • Compare expression patterns across developmental timepoints

• Mathematical modeling:

  • Develop computational models incorporating the negative feedback loop

  • Simulate perturbations to predict system behavior under various conditions

  • Validate predictions with experimental approaches

Published data shows that Gfi1aa significantly represses luciferase expression driven by the irf2bp2a promoter, and ChIP-PCR confirms direct binding of Gfi1aa to the irf2bp2a promoter in vivo .

How can CRISPR/Cas9 be optimized for generating and characterizing irf2bp2a knockout models?

Based on published approaches to generating irf2bp2a mutant lines:

• Guide RNA design:

  • Target conserved functional domains like the C4 zinc finger or C3HC4 ring finger

  • Design multiple gRNAs targeting different exons to increase knockout efficiency

  • Screen candidates using prediction tools to minimize off-target effects

• Validation of mutant lines:

  • Sequence genomic DNA to confirm mutations (e.g., the 5-nucleotide deletion described in the literature)

  • Verify production of truncated protein through Western blot analysis

  • Confirm altered subcellular localization of mutant protein via immunofluorescence microscopy

• Phenotypic characterization:

  • Examine neutrophil development through multiple complementary approaches:

    • Whole-mount in situ hybridization (WISH) for markers like mpx, lyz, and c/ebp1

    • Sudan Black staining for neutrophil detection

    • Fluorescent reporter line crosses (e.g., Tg(mpx:eGFP))

  • Quantify cell numbers and marker intensity across developmental stages

  • Assess other hematopoietic lineages to confirm specificity of effects

• Rescue experiments:

  • Inject wild-type irf2bp2a mRNA to confirm specificity of phenotype

  • Test domain-specific mutants (ZM, RM) to identify critical functional elements

  • Perform epistasis experiments through combined knockdown/knockout approaches

The literature describes successful generation of an irf2bp2a mutant with a 5-nucleotide deletion creating a truncated 122-amino acid protein with cytoplasmic mislocalization due to loss of the nuclear localization signal .

How should researchers address discrepancies between protein and mRNA expression levels of irf2bp2a?

Post-translational regulation often leads to discrepancies between mRNA and protein levels. When encountering such inconsistencies with irf2bp2a:

• Methodological verification:

  • Confirm antibody specificity through knockout/knockdown controls

  • Validate primer specificity for RT-qPCR through melt curve analysis and sequencing

  • Use multiple primer sets targeting different regions of the transcript

• Analysis of protein stability:

  • Perform cycloheximide chase assays to determine protein half-life

  • Test proteasome inhibitors (MG132) and lysosome inhibitors (chloroquine) to identify degradation pathways

  • Consider post-translational modifications that might affect antibody recognition

• Transcriptional vs. post-transcriptional regulation:

  • Examine mRNA stability through actinomycin D treatment and time-course analysis

  • Investigate potential microRNA-mediated regulation

  • Consider alternative splicing that might affect primer binding sites

• Tissue/cell-specific factors:

  • The negative feedback loop between irf2bp2a and Gfi1aa may create tissue-specific expression patterns

  • In neutrophils, higher Gfi1aa levels might repress irf2bp2a transcription

  • Compare expression across multiple cell types and developmental stages

The literature indicates that GFI1 mRNA levels are high in granulocytes while protein levels remain low due to rapid proteasomal degradation, suggesting similar regulatory mechanisms might apply to irf2bp2a .

What controls are essential when validating antibody specificity for irf2bp2a detection?

To ensure antibody specificity for irf2bp2a:

• Genetic controls:

  • Test antibody in irf2bp2a knockout/knockdown models

  • Compare staining patterns in wild-type vs. mutant samples

  • Use morpholino knockdown as a complementary approach to genetic knockouts

• Overexpression controls:

  • Express tagged irf2bp2a and confirm co-localization with antibody staining

  • Include mutant versions (truncated proteins) to test epitope specificity

• Cross-reactivity assessment:

  • Test in systems expressing only irf2bp2b (zebrafish paralog)

  • Perform peptide competition assays with immunizing peptide

  • Include isotype control antibodies in all experiments

• Application-specific validations:

  • For Western blot: confirm single band of appropriate molecular weight

  • For IHC/IF: verify expected subcellular localization (nuclear for wild-type)

  • For IP: confirm enrichment of target protein in immunoprecipitated fraction

• Multi-antibody approach:

  • Compare results using antibodies targeting different epitopes

  • Validate critical findings with at least two independent antibodies

The literature confirms that wild-type irf2bp2a localizes to the nucleus due to its nuclear localization signal, while mutant forms lacking this signal show cytoplasmic localization . These differences in localization provide useful controls for antibody validation.

How can researchers quantitatively assess the impact of irf2bp2a manipulation on neutrophil development?

For rigorous quantitative assessment of neutrophil development in irf2bp2a studies:

• Cell counting methodologies:

  • Whole-mount fluorescent imaging of reporter lines (e.g., Tg(mpx:eGFP))

  • Flow cytometry analysis of dissociated embryos for precise quantification

  • Automated image analysis for unbiased cell counting

• Expression quantification:

  • RT-qPCR of neutrophil markers (mpx, lyz, c/ebp1) in whole embryos

  • Single-cell RT-qPCR from FACS-sorted neutrophil populations

  • RNA-seq for comprehensive transcriptome analysis

• Functional assays:

  • Neutrophil migration assays in response to inflammatory stimuli

  • Phagocytosis assays to assess neutrophil functionality

  • Respiratory burst assays to measure oxidative responses

• Temporal analysis:

  • Track neutrophil development across multiple timepoints (22 hpf to 5 dpf)

  • Establish developmental trajectories for different genetic backgrounds

  • Determine if defects represent delayed development or terminal impairment

• Statistical approaches:

  • Use appropriate statistical tests based on data distribution

  • Perform power analysis to determine adequate sample sizes

  • Report effect sizes in addition to p-values for meaningful interpretation

Published studies employ multiple complementary techniques including WISH, fluorescent reporter lines, Sudan Black staining, and RT-qPCR to quantitatively assess neutrophil development defects in irf2bp2a-deficient embryos .

What are the potential implications of irf2bp2a research for understanding human hematological disorders?

The irf2bp2a-Gfi1aa regulatory axis has significant implications for human disease research:

• GFI1 dysregulation in hematological malignancies:

  • Different levels of GFI1 can determine its role as either tumor suppressor or oncogene in malignant myelopoiesis

  • Targeting GFI1 for proteasomal degradation through IRF2BP2 might represent a therapeutic strategy for myeloid cancers

• Neutrophil maturation disorders:

  • Defects in neutrophil differentiation contribute to conditions like congenital neutropenia

  • Understanding the irf2bp2a-Gfi1aa axis may provide insights into pathogenesis

  • The zebrafish model offers a platform for drug screening to identify compounds affecting this pathway

• Inflammatory diseases:

  • Neutrophil function and turnover play critical roles in inflammatory conditions

  • Targeting the regulation of neutrophil maturation could provide novel anti-inflammatory approaches

  • The negative feedback loop between irf2bp2a and Gfi1aa may represent a targetable node for modulating neutrophil numbers

• Translational applications:

  • Development of small molecules targeting IRF2BP2-GFI1 interaction

  • Biomarker potential of IRF2BP2 expression in predicting treatment response in myeloid disorders

  • Genetic screening for mutations in this pathway in patients with unexplained neutrophil abnormalities

The literature specifically notes that "discovery of certain drug targets GFI1 for proteasomal degradation by IRF2BP2 might be an effective anti-cancer strategy" , highlighting the translational potential of this research.

How can advanced imaging techniques enhance the study of irf2bp2a function in neutrophil differentiation?

Advanced imaging approaches offer powerful tools for investigating irf2bp2a biology:

• Live imaging in transgenic zebrafish:

  • Generate dual reporter lines (e.g., fluorescent-tagged irf2bp2a and Gfi1aa)

  • Track protein dynamics and interactions in real-time during neutrophil development

  • Correlate protein levels with differentiation stages and migratory behavior

• Super-resolution microscopy:

  • Resolve subcellular localization at nanoscale resolution

  • Investigate co-localization with proteasomal components

  • Study nuclear organization and potential irf2bp2a interaction with chromatin

• FRET/BRET techniques:

  • Directly measure irf2bp2a-Gfi1aa interactions in living cells

  • Monitor ubiquitination dynamics using ubiquitin-based sensors

  • Assess conformational changes upon binding of interaction partners

• Correlative light and electron microscopy (CLEM):

  • Link fluorescent protein localization with ultrastructural features

  • Examine neutrophil granule formation in relation to irf2bp2a activity

  • Visualize structural abnormalities in differentiating neutrophils of mutant models

• Intravital microscopy:

  • Study neutrophil behavior in intact animals under physiological conditions

  • Assess inflammatory responses and neutrophil recruitment in wild-type vs. mutant models

  • Evaluate pharmacological interventions targeting the irf2bp2a-Gfi1aa axis

Immunofluorescence techniques have already been used to demonstrate subcellular localization changes in mutant irf2bp2a proteins, showing cytoplasmic rather than nuclear localization . These approaches can be extended with advanced imaging technologies.