RNF149 Antibody

What is the molecular structure of RNF149 and how does it influence antibody selection?

RNF149 is a 400-amino acid protein with a calculated molecular weight of 43kDa and several distinct domains that influence antibody selection. Its structure includes an N-terminal signal peptide, a protease-associated (PA) domain, a transmembrane domain in the middle region (approximately 20 amino acid helical membrane stretch), and a cytosolic RING finger domain near its C-terminus that confers E3 ubiquitin ligase activity .

When selecting antibodies, researchers should consider which domain they wish to target based on their experimental goals. Antibodies targeting the cytoplasmic RING domain may be better suited for applications studying ubiquitination activity, while those targeting extracellular regions might be preferred for detecting intact protein on cell surfaces. The amino acid sequence between 221-400 of human RNF149 has been used as an immunogen for polyclonal antibody production, making antibodies raised against this region particularly useful for detection of the functional domains .

For cross-species studies, the high conservation of the RING domain makes it an ideal target for antibodies intended to work across human, mouse, and rat samples .

Which cellular functions of RNF149 are most relevant to antibody-based studies?

RNF149 functions primarily as an E3 ubiquitin ligase that mediates protein ubiquitination and subsequent degradation, playing crucial roles in maintaining cellular homeostasis. Several key functions make it an important target for antibody-based research:

First, RNF149 selectively degrades wild-type BRAF but notably not mutant BRAF (V600E), suggesting its role in regulating normal BRAF signaling . This selective degradation attenuates cell growth induced by wild-type BRAF, potentially functioning as a tumor suppressor mechanism in cells with normal BRAF .

Second, recent studies have identified RNF149's promotion of hepatocellular carcinoma (HCC) progression through its E3 ubiquitin ligase activity . Researchers investigating cancer mechanisms can use RNF149 antibodies to study this oncogenic function in tissue samples and cell lines.

Third, RNF149 associates with pre-emptive quality control (pEQC) factors like Bag6 and interacts with AIRAPL in a ubiquitin-dependent manner, suggesting involvement in protein quality control pathways . Antibodies are essential tools for studying these interactions through co-immunoprecipitation experiments.

Fourth, bioinformatics analyses reveal that RNF149 expression correlates with immunosuppressive tumor microenvironment and immune cell infiltration patterns, indicating potential roles in immune regulation . Immunohistochemistry with RNF149 antibodies can help characterize these associations in patient samples.

How should researchers validate the specificity of RNF149 antibodies?

Validating RNF149 antibody specificity requires a multi-faceted approach to ensure experimental reliability. Several methodological strategies are recommended:

First, perform Western blot validation to confirm detection of a single band at the expected molecular weight of 43kDa . Multiple or unexpected bands may indicate cross-reactivity with other RING finger proteins, which share structural similarities with RNF149.

Second, implement genetic controls through RNF149 knockdown or knockout experiments. Reduced signal intensity following siRNA/shRNA knockdown or CRISPR/Cas9 knockout provides strong evidence for antibody specificity. This is particularly important when studying RNF149 in cancer contexts where its expression may be altered .

Third, include positive control samples known to express RNF149. Mouse stomach tissue has been identified as a reliable positive control . For HCC studies, tumor samples showing RNF149 upregulation compared to adjacent normal tissue provide excellent validation opportunities .

Fourth, conduct peptide competition assays where pre-incubation of the antibody with the immunizing peptide (amino acids 221-400 of human RNF149) should abolish specific staining. This test directly confirms epitope specificity .

Fifth, perform orthogonal validation by correlating protein detection with mRNA expression data. The concordance between protein levels detected by antibodies and transcript levels measured by RT-PCR strengthens confidence in antibody specificity.

Finally, compare results across multiple applications. An antibody that demonstrates consistent results in Western blot, immunohistochemistry, and immunoprecipitation experiments is more likely to be truly specific for RNF149 .

What are the optimal conditions for using RNF149 antibodies in different experimental applications?

The optimal conditions for RNF149 antibody usage vary significantly across experimental applications, requiring specific optimization for each technique:

For Western Blot (WB) applications, the recommended dilution range is 1:500 to 1:2000 . Optimal protein loading typically ranges from 20-50μg per lane, with PVDF membranes often yielding better results than nitrocellulose for transmembrane proteins like RNF149. When probing for RNF149, inclusion of protease inhibitors in lysis buffers is critical to prevent degradation.

In Immunohistochemistry-Paraffin (IHC-P) protocols, a dilution range of 1:50 to 1:200 is recommended . Antigen retrieval is typically necessary, with citrate buffer (pH 6.0) or EDTA buffer (pH 9.0) being common choices. Overnight primary antibody incubation at 4°C often yields stronger specific signal than shorter incubations at room temperature.

For Immunofluorescence/Immunocytochemistry (IF/ICC), the optimal dilution also ranges from 1:50 to 1:200 . When studying RNF149 localization, co-staining with markers for cytoplasmic compartments is advisable given its predominantly cytoplasmic localization. Fixation with 4% paraformaldehyde typically preserves RNF149 epitopes better than methanol fixation.

For Immunoprecipitation (IP) applications, approximately 2μg of antibody per 500μg of protein lysate is recommended. Pre-clearing with Protein A/G PLUS agarose beads and control IgG (1μg) for 2 hours at 4°C is crucial to reduce non-specific binding . Washing buffers should contain detergents at concentrations that maintain specific interactions while removing background.

For all applications, experimental conditions should be systematically optimized by testing multiple parameters including antibody concentration, incubation time/temperature, and blocking reagents to achieve the best signal-to-noise ratio for each specific experimental system.

How can researchers effectively design experiments to study RNF149's E3 ligase activity?

Designing experiments to study RNF149's E3 ligase activity requires careful planning and appropriate controls. Several methodological approaches are recommended:

First, implement in vitro ubiquitination assays using immunopurified RNF149. This requires immunoprecipitating RNF149 from cell lysates using specific antibodies and incubating the purified protein with E1 enzyme, appropriate E2 enzymes, ubiquitin, ATP, and potential substrates such as wild-type BRAF . Detection of ubiquitinated products by Western blot provides direct evidence of E3 ligase activity.

Second, include appropriate domain mutation controls. Generate RING domain mutants of RNF149 as negative controls, as these mutants lack E3 ligase activity . Comparing ubiquitination activity between wild-type and mutant RNF149 establishes which molecular functions depend on its catalytic activity versus potential scaffold functions.

Third, perform substrate degradation kinetics using cycloheximide chase experiments. Treat cells with cycloheximide to inhibit new protein synthesis, then track degradation rates of known RNF149 substrates (such as wild-type BRAF) over time in the presence and absence of RNF149 . This reveals the impact of RNF149 on substrate stability.

Fourth, incorporate proteasome inhibitor controls. Treatment with MG132 or other proteasome inhibitors should stabilize RNF149-ubiquitinated substrates, confirming the proteasome-dependent degradation mechanism . The research demonstrates that MG132 increases the levels of RNF149-ubiquitinated wild-type BRAF.

Fifth, analyze ubiquitin chain topology using ubiquitin mutants or linkage-specific antibodies to determine the types of ubiquitin chains generated by RNF149. Different chain types (K48, K63, etc.) generally direct substrates to different fates, providing insight into the biological consequences of RNF149-mediated ubiquitination.

These approaches collectively provide robust assessment of RNF149's E3 ligase activity, substrate specificity, and biological function.

What are the critical considerations for optimizing immunoprecipitation of RNF149?

Immunoprecipitation (IP) of RNF149 requires specific optimizations to overcome challenges associated with membrane-associated E3 ligases. Several critical considerations should guide protocol development:

First, implement a rigorous pre-clearing step to reduce non-specific binding. This involves adding 20μL Protein A/G PLUS agarose beads and 1μg control IgG to cell lysates, followed by slow mixing at 4°C for 2 hours . This step is particularly important for RNF149 IPs due to the promiscuous binding tendencies of RING domain proteins.

Second, optimize lysis buffer composition to maintain protein-protein interactions while effectively solubilizing membrane-associated RNF149. Buffers containing 1% NP-40 or Triton X-100 typically work well, though CHAPS may better preserve certain protein interactions. Include protease inhibitors to prevent degradation and phosphatase inhibitors if studying phosphorylation-dependent interactions .

Third, when studying RNF149's ubiquitination activity, incorporate ubiquitination-preserving reagents. Add proteasome inhibitors (e.g., MG132) to cell treatments before lysis to stabilize ubiquitinated proteins, and include deubiquitinase inhibitors (e.g., N-ethylmaleimide or ubiquitin aldehyde) in lysis buffers to prevent removal of ubiquitin during sample processing .

Fourth, optimize antibody amounts and incubation conditions. Use 2μg of RNF149 antibody per reaction, incubating with pre-cleared lysate overnight at 4°C with gentle rotation . For weaker interactions or less abundant proteins, longer incubation times may improve IP efficiency.

Fifth, implement stringent washing procedures. After adding 20μL Protein A/G PLUS agarose beads and incubating for 4 hours at 4°C, wash beads 4-5 times with cold lysis buffer of decreasing detergent concentration to remove non-specific proteins while preserving specific interactions .

Finally, include appropriate controls with each experiment: IgG control immunoprecipitations to identify non-specific binding, and where possible, RNF149 knockdown/knockout samples to confirm specificity of immunoprecipitated bands.

How can researchers investigate RNF149's role in cancer progression mechanisms?

Investigating RNF149's role in cancer progression requires multifaceted approaches that examine both molecular mechanisms and cellular phenotypes. Several methodological strategies are recommended:

First, perform comprehensive expression analysis in clinical samples. Use immunohistochemistry with validated RNF149 antibodies to compare expression in paired tumor-normal tissues across cancer stages. Research has demonstrated that RNF149 is upregulated in hepatocellular carcinoma (HCC) tissues and correlates with poor prognosis, providing a foundation for further investigation .

Second, establish cause-effect relationships through functional studies in cancer cell lines. Generate RNF149 overexpression and knockdown models to assess effects on hallmark cancer phenotypes including proliferation, migration, and invasion. Experimental evidence shows that overexpression of RNF149 significantly promotes these cancer-associated behaviors in HCC cells .

Third, determine mechanism dependency through domain mutation analysis. Compare the effects of wild-type RNF149 versus RING domain mutants on cancer phenotypes. Research demonstrates that RNF149 promotes HCC progression through its E3 ubiquitin ligase activity, highlighting the importance of this catalytic function .

Fourth, identify novel substrates through immunoprecipitation-mass spectrometry approaches. Pull down RNF149 from cancer cells and identify associated proteins, then validate potential substrates using co-IP and ubiquitination assays. DNAJC25 has been identified as a novel RNF149 substrate in HCC, exemplifying this approach .

Fifth, investigate connections to the tumor immune microenvironment. Correlate RNF149 expression with immune cell infiltration patterns using multiplex immunohistochemistry and computational analyses such as single-sample gene set enrichment analysis (ssGSEA). Bioinformatics analyses reveal that high RNF149 expression correlates with immunosuppressive tumor microenvironment features, including specific immune cell infiltration patterns like M2 macrophages and exhausted T cells .

These approaches collectively provide comprehensive insights into how RNF149 contributes to cancer progression through both cell-autonomous mechanisms and broader effects on the tumor microenvironment.

What techniques should be employed to study the interaction between RNF149 and BRAF?

Studying the interaction between RNF149 and BRAF requires multiple complementary techniques that address different aspects of their relationship. Several sophisticated approaches should be considered:

First, employ co-immunoprecipitation (Co-IP) with domain mapping. Immunoprecipitate RNF149 and probe for BRAF in the precipitate, or vice versa, comparing interactions with wild-type BRAF versus mutant BRAF (V600E). Research has demonstrated that RNF149 interacts with wild-type BRAF but not mutant BRAF . For detailed mapping, create truncation mutants of BRAF (e.g., constructs lacking the kinase domain, or containing only the kinase domain) to identify interaction domains. Evidence indicates that RNF149 binds specifically to the C-terminal kinase-containing domain of wild-type BRAF .

Second, perform ubiquitination assays to assess functional consequences. After co-transfecting cells with RNF149 and BRAF constructs (both wild-type and mutant), immunoprecipitate BRAF and probe for ubiquitin to detect RNF149-mediated ubiquitination. Include proteasome inhibitors (MG132) to stabilize ubiquitinated species. Research shows RNF149 induces ubiquitination of wild-type BRAF but not V600E BRAF .

Third, conduct protein stability assays using cycloheximide chase experiments. Treat cells expressing wild-type or mutant BRAF with cycloheximide in the presence or absence of RNF149, then monitor BRAF levels over time by Western blot. This approach reveals how RNF149 affects BRAF protein turnover rates. Studies demonstrate that RNF149 accelerates wild-type BRAF turnover but not mutant BRAF turnover .

Fourth, analyze downstream signaling consequences through phosphorylation studies. Measure MEK/ERK phosphorylation levels in cells with varying levels of RNF149 to determine how RNF149-mediated degradation of BRAF affects downstream signaling. Research indicates RNF149 attenuates cell growth induced by wild-type BRAF, suggesting effects on proliferative signaling pathways .

These techniques together provide a comprehensive understanding of the physical interaction, enzymatic modification, and functional consequences of the RNF149-BRAF relationship.

How can researchers leverage RNF149 antibodies to study its role in immune regulation?

Leveraging RNF149 antibodies to study its role in immune regulation requires integrating multiple experimental approaches that connect molecular mechanisms to cellular phenotypes. Several methodological strategies are recommended:

First, implement multiplex immunohistochemistry/immunofluorescence techniques. Combine RNF149 antibodies with markers for various immune cell populations (CD8+ T cells, M2 macrophages, etc.) in tumor tissue sections. This approach reveals spatial relationships between RNF149-expressing cells and immune infiltrates, providing clues about potential cell-cell interactions. Bioinformatics analyses indicate that RNF149 expression correlates with specific immune cell infiltration patterns including activated CD8+ T cells and exhausted T cells .

Second, conduct correlation analyses between RNF149 expression and immune signatures. Use RNF149 antibodies for protein quantification via IHC or Western blot, then correlate expression levels with immune-related gene signatures measured by RNA-sequencing. Research has employed single-sample gene set enrichment analysis (ssGSEA) to assess immune enrichment scores and immune cell infiltration patterns in relation to RNF149 expression .

Third, perform Pearson correlation analyses between RNF149 protein expression and specific immune cell populations. This statistical approach reveals which immune cell types show significant associations with RNF149 levels, providing direction for mechanistic studies. For example, correlations with M2 macrophages might suggest immunosuppressive functions, while correlations with activated T cells might indicate immune activation .

Fourth, investigate RNF149's potential substrates in immune cells through co-immunoprecipitation experiments. Use RNF149 antibodies to pull down associated proteins from immune cell lysates, then identify potential targets by mass spectrometry or Western blot. This approach can reveal previously unknown mechanisms through which RNF149 might regulate immune cell function.

Fifth, examine how modulating RNF149 levels affects immune cell phenotypes and functions. Overexpress or knock down RNF149 in relevant cells, then assess changes in immune cell activation, cytokine production, or cytotoxic capacity. These functional studies connect RNF149 expression patterns with immunological consequences.

These approaches collectively provide mechanistic insights into how RNF149 may influence immune regulation, particularly in cancer contexts where immune dysfunction is common.

What are the common technical challenges when using RNF149 antibodies and how can they be resolved?

Researchers face several common technical challenges when working with RNF149 antibodies, each requiring specific troubleshooting approaches:

First, weak or absent Western blot signals frequently occur when detecting RNF149. To resolve this, optimize protein extraction using detergent-containing buffers appropriate for membrane-associated proteins like RNF149. Include protease inhibitors to prevent degradation and consider enriching membrane fractions if working with whole cell lysates. Increase protein loading (up to 50-100μg) and optimize transfer conditions for the 43kDa RNF149 protein .

Second, non-specific binding in immunoprecipitation experiments presents significant challenges. Implement a thorough pre-clearing step as described in published protocols: add 20μL Protein A/G PLUS agarose beads and 1μg control IgG to cell lysates, mixing slowly at 4°C for 2 hours before adding RNF149 antibody . This reduced background in RNF149 IPs significantly in published studies.

Third, inconsistent immunohistochemistry results may arise due to RNF149's membrane association. Optimize antigen retrieval methods, testing both heat-induced epitope retrieval with citrate buffer (pH 6.0) and EDTA buffer (pH 9.0). For RNF149's transmembrane nature, detergent-containing solutions during permeabilization steps improve antibody access to epitopes .

Fourth, cross-reactivity with other RING finger proteins can confound results. Validate antibody specificity using RNF149 knockdown or knockout controls. Include peptide competition assays, particularly with the immunizing peptide (amino acids 221-400) . When studying RNF149 in cancer contexts, compare antibody staining patterns with mRNA expression data for further validation .

Fifth, detecting ubiquitination activity presents technical hurdles. When studying RNF149's E3 ligase function, include proteasome inhibitors (MG132) in cell treatments to stabilize ubiquitinated species. Add deubiquitinating enzyme inhibitors to lysis buffers to preserve ubiquitin modifications during sample processing .

Addressing these challenges through systematic optimization improves the reliability and reproducibility of experiments using RNF149 antibodies.

How should conflicting results between RNF149 expression and functional studies be interpreted?

Interpreting conflicting results between RNF149 expression and functional studies requires careful consideration of several biological and technical factors:

First, recognize context-dependent activities as a common source of apparent contradictions. RNF149 exhibits different functions in different cellular contexts - it degrades wild-type BRAF but not mutant BRAF , acts as a tumor suppressor in some contexts by attenuating wild-type BRAF-induced cell growth , yet promotes cancer progression in hepatocellular carcinoma . These seemingly conflicting roles may reflect genuine biological complexity rather than experimental error.

Second, consider substrate availability as a critical determinant of RNF149 function. If key substrates (e.g., wild-type BRAF) are absent or mutated in certain experimental systems, RNF149 may not exhibit expected functions despite normal expression. Verify the status of known RNF149 substrates in your experimental system, particularly the BRAF mutation status, as RNF149 selectively targets wild-type BRAF but not mutant BRAF .

Third, examine post-translational modifications that may affect RNF149 activity without changing expression levels. As an E3 ligase, RNF149 itself may undergo regulatory modifications that alter its function. Assess whether RNF149 is subject to phosphorylation, ubiquitination, or other modifications in your experimental context.

Fourth, analyze protein-protein interaction differences across experimental systems. RNF149 function depends on interactions with proteins like AIRAPL (in a ubiquitin-dependent manner) and quality control factors like Bag6 . Variations in the expression or activity of these cofactors could explain functional differences despite similar RNF149 expression.

Fifth, evaluate experimental timeframes carefully. Some functions of RNF149 may be transient or cell cycle-dependent. Design time-course experiments to capture dynamic activities, considering that ubiquitination is often a rapid and dynamic process.

Finally, implement multi-method validation approaches. When expression and function appear discordant, verify results using orthogonal methods. For example, complement Western blot protein quantification with RT-PCR for mRNA levels, or validate functional assays using both gain- and loss-of-function approaches.

What experimental controls are essential when studying RNF149's ubiquitination activity?

When studying RNF149's ubiquitination activity, several essential controls must be included to ensure experimental rigor and accurate interpretation:

First, incorporate RING domain mutant controls. Generate and include a RING domain mutant of RNF149 that lacks E3 ligase activity as a catalytically inactive control . This mutant helps distinguish effects dependent on E3 ligase activity from potential scaffold functions of RNF149, establishing whether observed phenotypes require catalytic activity.

Second, include substrate specificity controls. Test both wild-type and mutant versions of known substrates, particularly wild-type and V600E BRAF . Research demonstrates that RNF149 selectively ubiquitinates wild-type BRAF but not mutant BRAF, providing an excellent internal control system. This comparison verifies the specificity of RNF149-mediated ubiquitination.

Third, implement proteasome inhibition controls. Include experimental conditions with proteasome inhibitors (e.g., MG132) to stabilize ubiquitinated proteins destined for degradation . Research shows MG132 increases the levels of RNF149-ubiquitinated wild-type BRAF, confirming the proteasome-dependent nature of the degradation mechanism.

Fourth, perform genetic knockdown/knockout controls. Use siRNA, shRNA, or CRISPR approaches to reduce or eliminate RNF149, establishing the dependency of observed ubiquitination on RNF149 specifically. These controls should show reduced ubiquitination of RNF149 substrates compared to control cells.

Fifth, include immunoprecipitation controls. For co-immunoprecipitation experiments, add control IgG immunoprecipitations and pre-clear lysates with Protein A/G beads and control IgG . These steps reduce non-specific binding in ubiquitination assays and have been explicitly validated in RNF149 studies.

Sixth, for in vitro ubiquitination assays, include reactions missing individual components. No-ATP, no-E1, no-E2, and no-RNF149 controls establish the requirement for each component in the ubiquitination cascade . This verifies that observed ubiquitination requires the complete enzymatic pathway.

These controls collectively establish the specificity, mechanism, and functional significance of RNF149-mediated ubiquitination, ensuring robust and reproducible results.

What are emerging applications of RNF149 antibodies in cancer research?

Emerging applications of RNF149 antibodies in cancer research are opening new avenues for understanding tumor biology and developing therapeutic strategies. Several promising directions are apparent:

First, RNF149 antibodies are increasingly valuable for patient stratification and prognostic assessment. Given that RNF149 upregulation correlates with poor prognosis in hepatocellular carcinoma patients , antibody-based detection of RNF149 in tumor samples could help identify patients likely to experience aggressive disease progression. Standardized immunohistochemical scoring of RNF149 expression could be incorporated into clinical assessment protocols.

Second, these antibodies enable investigation of RNF149's relationship with immunotherapy response. The correlation between high RNF149 expression and immunosuppressive tumor microenvironment features suggests potential influence on immunotherapy efficacy. RNF149 antibodies can be used in multiplex immunohistochemistry panels to simultaneously assess RNF149 expression and immune cell infiltration patterns in patient samples before and during immunotherapy.

Third, RNF149 antibodies facilitate substrate discovery through proximity-based labeling approaches. By coupling RNF149 antibodies with techniques like BioID or APEX2, researchers can identify proteins in close proximity to RNF149 in living cells, potentially revealing novel substrates beyond the known targets of wild-type BRAF and DNAJC25 .

Fourth, these antibodies support investigation of RNF149's role in cancer subtypes beyond hepatocellular carcinoma. While RNF149 gene mutations have been reported in breast, ovarian, and colorectal cancers , protein-level studies across cancer types remain limited. Systematic application of RNF149 antibodies across cancer tissue arrays could reveal previously unrecognized associations.

Finally, RNF149 antibodies enable pharmacodynamic monitoring for emerging therapies targeting E3 ligases. As interest grows in developing inhibitors of specific E3 ligases, RNF149 antibodies can serve as tools to monitor target engagement and pathway modulation in response to therapeutic interventions.

These emerging applications highlight the expanding utility of RNF149 antibodies beyond basic research into translational and clinical cancer research domains.

How might RNF149 antibodies contribute to understanding the intersection of ubiquitination and immune regulation?

RNF149 antibodies offer unique opportunities to elucidate the intersection between ubiquitination pathways and immune regulation, an emerging area of significant research interest. Several promising research directions can be pursued:

First, RNF149 antibodies enable detailed mapping of expression patterns across immune cell subpopulations. By combining flow cytometry with RNF149 antibodies, researchers can determine which immune cell types express RNF149 and at what levels during different activation states. This foundational information is currently lacking but essential for understanding RNF149's immunoregulatory potential.

Second, these antibodies facilitate investigation of RNF149's substrates in immune cells. Immunoprecipitation with RNF149 antibodies followed by mass spectrometry can identify immune-specific substrates that may differ from those in cancer cells. Given that bioinformatics analyses have revealed correlations between RNF149 expression and immune cell functions , identifying the molecular mechanisms underlying these associations is a critical next step.

Third, RNF149 antibodies support the characterization of dynamic changes in RNF149's interactions during immune responses. Time-course immunoprecipitation studies during immune cell activation can reveal how RNF149's interactome changes over time, potentially identifying regulatory switches in immune signaling pathways.

Fourth, these antibodies enable investigation of how RNF149-mediated ubiquitination affects antigen presentation. Given RNF149's role in protein quality control pathways , it may influence MHC class I loading and presentation of tumor antigens. Immunofluorescence studies using RNF149 antibodies alongside markers for antigen processing compartments can reveal potential co-localization and functional interactions.

Finally, RNF149 antibodies allow researchers to examine connections between metabolic regulation and immune function. E3 ubiquitin ligases increasingly appear to regulate metabolic enzymes, and immune cell metabolism profoundly influences function. Co-immunoprecipitation studies with RNF149 antibodies may identify metabolic enzymes as substrates, potentially explaining how RNF149 influences immune cell behavior.

These approaches collectively promise to reveal previously unrecognized mechanisms through which ubiquitination pathways, particularly those mediated by RNF149, regulate immune function in both normal and disease states.