UBC35 Antibody

What is UBC35 and why is it relevant to study in research settings?

UBC35 (also known as UBC13-type E2) is an ubiquitin-conjugating enzyme that plays a crucial role in the K63 polyubiquitination process. In plants such as Arabidopsis, UBC35 along with UBC36 functions in various biological processes including DNA damage response, iron metabolism, and root development . The study of UBC35 is particularly relevant because the ubiquitination system regulates numerous cellular processes, and dysregulation of this system is associated with various diseases. Using UBC35 antibodies allows researchers to monitor UBC35 protein expression, localization, and interaction with other proteins, providing insights into ubiquitin-mediated signaling pathways .

How do I select the appropriate UBC35 antibody for Western blot applications?

When selecting a UBC35 antibody for Western blot applications, consider the following factors:

• Specificity: Ensure the antibody specifically recognizes UBC35 without cross-reactivity to similar proteins like UBC36. Review validation data provided by manufacturers.

• Species reactivity: Confirm the antibody recognizes UBC35 from your species of interest (plant, human, etc.).

• Application validation: Verify the antibody has been validated for Western blot analysis.

• Epitope information: Choose antibodies targeting well-conserved regions if working across species.

• Clonality: Monoclonal antibodies offer high specificity for a single epitope, while polyclonal antibodies provide more robust detection.

For Western blotting, typical dilutions range from 1:500 to 1:5000, as seen in research protocols using similar antibodies . Always optimize conditions by testing different dilutions with positive controls expressing UBC35.

What controls should I include when using UBC35 antibody in immunoprecipitation experiments?

For immunoprecipitation experiments with UBC35 antibody, include these essential controls:

• Input control: Save a small aliquot of the pre-IP lysate to confirm target protein presence.

• Negative control antibody: Use an isotype-matched irrelevant antibody to identify non-specific binding.

• No-antibody control: Process samples without primary antibody to detect non-specific protein binding to beads.

• Positive control protein: Include a known interacting partner of UBC35 (like UEV1A-D in plant systems ).

• Knockdown/knockout validation: If available, use UBC35-depleted samples (like the ubc35-1 null mutant described in plant studies ) as a negative control.

For UBC35 immunoprecipitation specifically, researchers typically use 3-5 μg of antibody with 20 μl Protein A/G PLUS-Agarose beads, similar to protocols described for other ubiquitination-related proteins .

How can I optimize Co-IP protocols to detect transient UBC35 interactions with E3 ligases?

Detecting transient interactions between UBC35 and E3 ligases requires optimized Co-IP protocols:

• Chemical crosslinking: Apply membrane-permeable crosslinkers (like DSP or formaldehyde) at 0.5-2% for 10-15 minutes to stabilize transient interactions before cell lysis.

• Modified lysis conditions: Use gentler detergents like 0.5% NP-40 or 1% Digitonin instead of stronger detergents like Triton X-100 to preserve protein complexes.

• Proteasome inhibitors: Include MG132 (10 μM) in your lysis buffer to prevent degradation of ubiquitinated substrates.

• DUB inhibitors: Add N-ethylmaleimide (10 mM) or PR-619 to prevent deubiquitination during sample preparation.

• Immobilized antibody approach: Pre-couple UBC35 antibodies to beads before adding lysate to reduce washing steps and preserve weak interactions.

Research on ubiquitin-specific proteases has shown that Co-IP can successfully detect interactions between enzymes and their substrates when properly optimized, as demonstrated in the PKM2-USP35 interaction studies . For UBC35 specifically, protocols using protein A/G PLUS-Agarose beads have successfully identified interactions with multiple E3 ligases .

What strategies can I use to study UBC35's role in K63 polyubiquitination networks?

To investigate UBC35's role in K63 polyubiquitination networks:

• Protein-protein interaction mapping: Use yeast two-hybrid (Y2H) screening to identify UBC35-interacting proteins. This approach has successfully identified 24 protein-protein interactions for UBC35/36 and their UEV partners in Arabidopsis .

• K63-linkage specific antibody co-staining: Perform co-immunofluorescence with UBC35 antibody and K63-linkage specific antibodies to visualize co-localization of UBC35 with K63 polyubiquitin chains.

• Proximity-based labeling: Employ BioID or APEX2 fused to UBC35 to identify proximal proteins in living cells.

• Mass spectrometry analysis: Use antibody-based pulldowns of UBC35 followed by mass spectrometry to identify interacting partners and potential substrates.

• Genetic approaches: Utilize CRISPR-Cas9 to create UBC35 knockout or knockdown lines (similar to the ubc35-1 null mutant ), then perform global proteomics to identify affected ubiquitination substrates.

Research has shown that UBC35 interacts with various E3 ligases, primarily from the RING/U-box family, which are involved in substrate selection for K63 polyubiquitination .

How does UBC35 antibody specificity impact results when studying closely related isoforms like UBC36?

UBC35 and UBC36 are closely related isoforms with high sequence similarity, making antibody specificity a critical consideration:

• Epitope selection: Antibodies targeting highly conserved regions will likely cross-react with both UBC35 and UBC36. In research studies, antibodies like anti-UBC13 have been used to detect both proteins collectively .

• Western blot analysis: When interpreting Western blot results:

  • Look for subtle differences in molecular weight (if any exist between isoforms)

  • Use knockout/knockdown controls (e.g., ubc35-1 and ubc36-1 mutants ) to confirm band identity

  • Consider running higher resolution gels (12-15% acrylamide) to better separate similar-sized proteins

• Validation strategies:

  • Peptide competition assays using isoform-specific peptides

  • Testing antibody reactivity against recombinant UBC35 and UBC36 proteins

  • Immunoprecipitation followed by mass spectrometry to confirm target identity

• Data interpretation considerations:

  • Acknowledge potential cross-reactivity in publications

  • When possible, complement antibody-based detection with transcript-level analysis

  • Consider using epitope-tagged versions of UBC35/UBC36 for cleaner detection

Research has shown that determining the specific functions of UBC35 versus UBC36 often requires genetic approaches (e.g., individual and double mutants) rather than relying solely on antibody-based detection .

What are the optimal fixation and antigen retrieval methods for UBC35 immunohistochemistry?

For optimal UBC35 detection in immunohistochemistry:

Fixation protocols:

• FFPE tissues: Fix in 10% neutral-buffered formalin for 24-48 hours, followed by standard paraffin embedding.

• Frozen sections: Fix with 4% paraformaldehyde for 10-15 minutes post-sectioning.

• Cell preparations: Fix cells in 4% paraformaldehyde for 15 minutes at room temperature.

Antigen retrieval methods:

• Heat-induced epitope retrieval (HIER): Use citrate buffer (pH 6.0) or EDTA buffer (pH 9.0) at 95-98°C for 20 minutes.

• Enzymatic retrieval: Treatment with proteinase K (10-20 μg/ml) for 10-15 minutes at 37°C can be effective for some ubiquitination-related antibodies.

Optimization suggestions:

• Test both HIER methods as the optimal pH depends on the antibody's epitope recognition

• Include permeabilization step (0.1-0.3% Triton X-100) for better antibody penetration

• Block with 5-10% normal serum from the same species as the secondary antibody

Scoring systems similar to those used for other ubiquitination-related proteins can be applied, using both staining intensity (0-3 scale) and percentage of positive cells (0-4 scale) to create a total score, with high expression typically defined as a total score ≥4 .

How can I design experiments to distinguish between UBC35's enzymatic activity and scaffold function?

Distinguishing between UBC35's enzymatic activity and scaffold function requires thoughtful experimental design:

• Catalytic mutant approach:

  • Generate catalytic-dead UBC35 mutants (typically by mutating the active site cysteine)

  • Perform complementation studies in UBC35-null backgrounds (e.g., ubc35-1 )

  • Compare phenotypic rescue between wild-type and catalytic mutants

• Domain-specific mutations:

  • Target regions involved in E3 binding without affecting catalytic activity

  • Generate chimeric proteins swapping domains between UBC35 and other E2 enzymes

  • Assess protein interaction profiles using Co-IP or Y2H assays

• In vitro ubiquitination assays:

  • Reconstitute ubiquitination reactions using purified components

  • Compare reactions with active vs. inactivated UBC35

  • Assess K63 chain formation using K63-linkage specific antibodies

• Temporal separation:

  • Use rapid inducible systems (e.g., auxin-inducible degrons) to acutely deplete UBC35

  • Monitor immediate vs. delayed effects to distinguish between enzymatic and structural roles

• Quantitative proteomics:

  • Compare changes in K63-polyubiquitinated substrates vs. total protein interactome

  • Use SILAC or TMT labeling for precise quantification of changes

This approach is similar to methods used to study other ubiquitination enzymes like USP35, where both enzymatic activity and protein-protein interactions contribute to biological function .

What are the critical parameters for quantifying UBC35 expression levels accurately?

Accurate quantification of UBC35 expression requires attention to several critical parameters:

For Western blot quantification:

• Protein extraction: Use standardized lysis buffers containing deubiquitinase inhibitors (10mM N-ethylmaleimide) and protease inhibitors to prevent protein degradation.

• Loading controls: Select appropriate loading controls (β-actin, GAPDH, or total protein staining) based on your experimental conditions.

• Linear detection range: Perform dilution series to ensure signal falls within the linear range of detection.

• Normalization method: Use total protein normalization (e.g., stain-free gels) instead of single housekeeping proteins for more reliable quantification.

• Replication: Include at least three biological replicates and technical duplicates.

For immunohistochemistry quantification:

• Standardized scoring: Implement a consistent scoring system combining staining intensity and percentage of positive cells, as described for USP35 .

• Automated analysis: Use digital image analysis software with consistent thresholding parameters.

• Blinded assessment: Have multiple observers score samples blindly to reduce bias.

For RT-qPCR of UBC35 mRNA:

• Primer specificity: Design primers that specifically amplify UBC35 without cross-amplifying UBC36 or other related genes.

• Reference gene selection: Validate stability of reference genes under your experimental conditions.

• Efficiency correction: Determine and account for PCR amplification efficiency.

Research on ubiquitination-related proteins demonstrates that standardized quantification methods are essential for reliable assessment of expression levels across different experimental conditions .

How should I interpret conflicting data between UBC35 antibody signals and genetic knockout phenotypes?

When faced with discrepancies between antibody signals and genetic knockout phenotypes:

• Validate antibody specificity:

  • Confirm antibody specificity using knockout controls (e.g., ubc35-1 null mutant )

  • Perform epitope mapping to understand what region the antibody recognizes

  • Test multiple antibodies targeting different UBC35 epitopes

• Consider genetic compensation:

  • Examine expression of related genes (e.g., UBC36) in knockout models

  • Look for upregulation of alternative pathways that might compensate for UBC35 loss

  • Evaluate acute vs. chronic loss-of-function models (e.g., RNAi vs. genetic knockout)

• Assess technical aspects:

  • Examine sensitivity thresholds of antibody detection vs. phenotypic manifestation

  • Consider post-transcriptional regulation that might explain discrepancies

  • Evaluate tissue/cell type-specific effects that might be diluted in whole-organism studies

• Experimental approaches to resolve conflicts:

  • Use complementary techniques (RNA-seq, proteomics) to validate findings

  • Perform rescue experiments with controlled expression levels

  • Develop more sensitive assays for subtle phenotypes

• Interpretation framework:

  • Consider that different phenotypes may have different thresholds of UBC35 requirement

  • Acknowledge that antibody signals provide information on protein levels but not necessarily function

  • Evaluate context-dependency of UBC35 function across different tissues or conditions

Research on ubiquitination pathway components has shown that functional redundancy and context-specific roles can lead to discrepancies between protein detection and phenotypic outcomes .

What approaches can I use to map the UBC35 interactome in different physiological conditions?

To map the UBC35 interactome across different physiological conditions:

• Affinity purification-mass spectrometry (AP-MS):

  • Use UBC35 antibodies for immunoprecipitation followed by MS analysis

  • Compare interactomes under different conditions (stress, development, disease)

  • Apply SILAC or TMT labeling for quantitative comparison between conditions

• Proximity-based labeling:

  • Generate UBC35-BioID or UBC35-APEX2 fusion proteins

  • Induce labeling under different physiological conditions

  • Identify neighboring proteins through streptavidin pulldown and MS

• Yeast two-hybrid (Y2H) screening:

  • Use UBC35 as bait against normalized cDNA libraries from different conditions

  • Apply the Y2H mapping liquid pipeline approach against ORF collections as demonstrated for UBC35/36

  • Create interaction networks using Cytoscape with different datasets

• In situ protein interaction analysis:

  • Employ proximity ligation assays (PLA) to visualize UBC35 interactions in intact cells

  • Compare interaction patterns across different tissues or treatments

  • Combine with high-content imaging for quantitative analysis

• Computational network analysis:

  • Integrate experimental data with existing protein interaction databases

  • Apply network analysis algorithms to identify condition-specific modules

  • Use biophysics-informed models to predict interaction dynamics under different conditions

Research has successfully identified 24 protein-protein interactions for UBC35/36 and their UEV partners in Arabidopsis using Y2H screening approaches , providing a foundation for condition-specific interactome mapping.

How can I use UBC35 antibodies to study the dynamics of K63 polyubiquitination during stress responses?

To study K63 polyubiquitination dynamics during stress responses using UBC35 antibodies:

• Time-course immunoprecipitation:

  • Expose cells/organisms to stress conditions (e.g., DNA damage, oxidative stress)

  • Collect samples at multiple time points (0, 15, 30, 60, 120 min post-treatment)

  • Perform UBC35 immunoprecipitation followed by Western blotting with K63-linkage specific antibodies

  • Quantify changes in UBC35-associated K63 polyubiquitin chains over time

• Co-localization analysis:

  • Perform immunofluorescence with UBC35 antibody and K63-linkage specific antibodies

  • Track changes in co-localization patterns during stress response

  • Use high-resolution microscopy (SIM, STORM) for detailed localization analysis

• Substrate identification:

  • Combine UBC35 antibody pulldowns with K63-ubiquitin enrichment

  • Identify substrates by mass spectrometry

  • Compare substrate profiles across different stress conditions and time points

• Functional assays:

  • Correlate UBC35 activity with stress-responsive phenotypes

  • Use genetic approaches (e.g., UBC35 mutants like ubc35-1 ) to validate findings

  • Employ UBC35 catalytic mutants to distinguish between enzymatic and scaffold functions

• Quantitative proteomics:

  • Apply SILAC or TMT labeling for precise quantification of K63-polyubiquitinated substrates

  • Integrate with transcriptomics data to identify post-translational vs. transcriptional regulation

  • Analyze pathway enrichment to identify stress-specific UBC35 targets

Research has shown that UBC35/36 mutants exhibit hypersensitivity to DNA-damaging agents , suggesting a crucial role in stress response that can be further characterized using these approaches.

How can structural insights from UBC35 antibody epitope mapping inform the design of specific inhibitors of K63 polyubiquitination?

Structural insights from UBC35 antibody epitope mapping can guide inhibitor design through:

• Epitope-based structural analysis:

  • Identify antibody epitopes that interfere with UBC35's catalytic activity or protein interactions

  • Map these epitopes onto the three-dimensional structure of UBC35

  • Focus on functional regions (e.g., catalytic site, E3-binding interface, UEV-binding surface)

• Structure-guided inhibitor design:

  • Develop peptide mimetics based on antibody complementarity-determining regions (CDRs)

  • Design small molecules targeting critical interfaces identified through epitope mapping

  • Apply biophysics-informed computational models to predict binding specificity of potential inhibitors

• Specificity engineering:

  • Exploit structural differences between UBC35 and related E2 enzymes

  • Target unique interfaces involved in K63-specific chain formation

  • Design allosteric inhibitors that selectively affect K63 chain assembly without disrupting catalytic activity

• Validation strategies:

  • Use competition assays between antibodies and candidate inhibitors

  • Employ in vitro ubiquitination assays with purified components

  • Verify cellular efficacy and specificity through proteomics approaches

• Application to disease models:

  • Test inhibitors in models where K63 polyubiquitination is dysregulated

  • Compare effects with genetic manipulation of UBC35 (e.g., CRISPR knockout)

  • Optimize candidates for drug-like properties while maintaining specificity

This approach leverages methodologies similar to those used in antibody design studies that successfully generated antibodies with customized specificity profiles .

What are the methodological challenges in using UBC35 antibodies to study spatiotemporal dynamics of ubiquitination in live cells?

Studying spatiotemporal dynamics of UBC35-mediated ubiquitination in live cells presents several methodological challenges:

• Limitations of conventional antibodies:

  • Traditional antibodies cannot penetrate intact cell membranes

  • Chemical fixation required for antibody staining prevents live-cell imaging

  • Temporal resolution is limited to discrete timepoints

• Alternative approaches:

  • Develop cell-permeable nanobodies against UBC35

  • Create fluorescent fusion proteins (UBC35-GFP) for live imaging

  • Use fluorescently-labeled ubiquitin sensors to track K63 chain formation

  • Employ split-GFP complementation systems to visualize UBC35-substrate interactions

• Technical considerations:

  • Ensure fusion tags don't interfere with UBC35 function

  • Validate physiological expression levels to avoid artifacts

  • Optimize imaging parameters to reduce phototoxicity while maintaining signal

• Advanced imaging strategies:

  • Apply FRET-based sensors to detect conformational changes during ubiquitination

  • Use fluorescence recovery after photobleaching (FRAP) to measure UBC35 dynamics

  • Implement optogenetic tools to spatially and temporally control UBC35 activity

• Data analysis challenges:

  • Develop computational methods to track individual ubiquitination events

  • Apply machine learning algorithms to identify patterns in spatiotemporal data

  • Integrate imaging data with biochemical measurements for comprehensive analysis

These approaches build upon established techniques in protein dynamics research while addressing the specific challenges of studying ubiquitination enzymes like UBC35.

How can we integrate UBC35 antibody-based proteomics with systems biology approaches to model the impact of ubiquitination on cellular networks?

Integrating UBC35 antibody-based proteomics with systems biology requires sophisticated methodological approaches:

• Multi-omics data generation:

  • Perform UBC35 antibody-based immunoprecipitation coupled with mass spectrometry

  • Combine with global proteomics, ubiquitinomics, transcriptomics, and metabolomics

  • Generate time-course data following UBC35 perturbation (knockout, inhibition, overexpression)

• Network construction:

  • Build protein-protein interaction networks centered on UBC35 and its interactors

  • Integrate K63-polyubiquitinated substrates identified through proteomics

  • Incorporate temporal dynamics and feedback mechanisms

• Computational modeling:

  • Develop ordinary differential equation (ODE) models of core UBC35-dependent pathways

  • Apply constraint-based modeling to predict system-wide effects of UBC35 perturbation

  • Use machine learning approaches to identify patterns in complex multi-omics datasets

  • Employ biophysics-informed models to predict binding specificity and interaction dynamics

• Experimental validation:

  • Test model predictions through targeted experiments

  • Use CRISPR-Cas9 to generate precise genetic perturbations

  • Apply synthetic biology approaches to rewire ubiquitination networks

• Biological insights:

  • Identify emergent properties and network motifs in UBC35-dependent systems

  • Predict cellular responses to environmental changes or stressors

  • Discover potential therapeutic targets for diseases involving dysregulated ubiquitination

This integrated approach has been successfully applied to study complex biological systems and can reveal novel insights into UBC35 function beyond what traditional reductionist approaches can achieve .