TRIM39 Antibody

What is TRIM39 and why is it important in research?

TRIM39 (Tripartite Motif Containing 39) is a member of the TRIM family of proteins characterized by three zinc-binding domains (RING, B-box type 1, and B-box type 2) and a coiled-coil region. It plays critical roles in cell cycle regulation, DNA damage response, and apoptosis. TRIM39 regulates p21 stability and is involved in cancer progression, particularly in colorectal cancer and hepatocellular carcinoma. Its significance lies in its function as both a regulator of cell fate determination and a potential therapeutic target in cancer research .

What are the known isoforms of TRIM39?

There are two main splice variants of TRIM39:

• TRIM39α: The longer isoform (518 amino acids, ~60 kDa)

• TRIM39β: A shorter isoform (488 amino acids, ~56 kDa) missing amino acids 269-298 within Exon 6

Research indicates TRIM39β is relatively more abundant than TRIM39α in various human cancer cell lines. These isoforms can form protein complexes, with TRIM39β playing a role in maintaining TRIM39α stability .

What applications are TRIM39 antibodies suitable for?

TRIM39 antibodies are validated for multiple applications including:

• Western Blot (WB): Typically used at dilutions of 1:500-1:2000

• Enzyme-Linked Immunosorbent Assay (ELISA)

• Immunohistochemistry (IHC)

• Immunofluorescence (IF)

The specific applications vary by antibody product, with some antibodies showing broader application profiles than others .

What species reactivity should I expect from TRIM39 antibodies?

TRIM39 antibodies demonstrate variable species reactivity. Some are highly specific to human TRIM39, while others show cross-reactivity with mouse and rat TRIM39. Certain antibodies have broader reactivity profiles spanning multiple species including cow, dog, guinea pig, and horse . Always check the product datasheet for specific reactivity information before selecting an antibody for your experimental model.

What is the optimal sample preparation protocol for TRIM39 detection by Western blot?

For optimal TRIM39 detection by Western blot:

• Prepare lysates with complete protease inhibitor cocktail to prevent degradation

• Include N-ethylmaleimide (NEM) to preserve ubiquitination status if studying TRIM39's E3 ligase function

• Use 25-50 µg of protein per lane for cell line samples

• Consider using 3% nonfat dry milk in TBST as blocking buffer

• Primary antibody incubation at 1:1000 dilution (adjust based on specific antibody)

• HRP-conjugated secondary antibody at 1:10,000

• ECL detection with appropriate exposure time (approximately 90 seconds has been reported to be effective)

For tissue samples like brain, skeletal muscle, or kidney, pay special attention to tissue-specific extraction protocols to maintain protein integrity .

How can I validate TRIM39 knockdown efficiency when antibodies have limited sensitivity for endogenous TRIM39?

Since some TRIM39 antibodies may have limited sensitivity for detecting endogenous TRIM39, a multi-approach validation strategy is recommended:

• Quantitative RT-PCR (qRT-PCR) using TaqMan probes specific for TRIM39α and TRIM39β

• Transient transfection of tagged TRIM39 constructs (e.g., TRIM39α-Myc or TRIM39β-Myc) followed by shRNA delivery and detection with tag-specific antibodies

• Functional validation by measuring downstream effects on known TRIM39 targets (e.g., p21 protein levels)

• Use of multiple independent shRNAs targeting different regions of TRIM39 to confirm specificity of observed effects

Researchers have successfully used this approach to validate TRIM39 knockdown despite challenges with antibody detection of endogenous protein .

What controls should I include when studying TRIM39 using antibody-based techniques?

For rigorous TRIM39 research, include these controls:

• Positive controls:

  • Cell lines with known TRIM39 expression (HCT116, HeLa, Saos2, U2OS)

  • Tissue samples with confirmed TRIM39 expression (brain, skeletal muscle, kidney)

  • Overexpression of tagged TRIM39 constructs

• Negative controls:

  • Isotype-matched IgG for immunoprecipitation experiments

  • TRIM39-knockdown samples using validated shRNAs

  • In the case of immunohistochemistry, peptide competition assays

• Specificity controls:

  • Detection of both TRIM39α (~60 kDa) and TRIM39β (~56 kDa) isoforms

  • Isoform-specific knockdown to validate band identity

Why does my TRIM39 antibody detect multiple bands, and how can I identify the specific TRIM39 band?

Multiple bands in TRIM39 detection can occur due to:

• Presence of both TRIM39α (~60 kDa) and TRIM39β (~56 kDa) isoforms

• Post-translational modifications, especially ubiquitination and SUMOylation

• Proteolytic degradation products

To identify specific TRIM39 bands:

• Compare with molecular weight markers (expected: 45-60 kDa depending on isoform)

• Use positive controls with overexpressed tagged TRIM39

• Perform isoform-specific knockdown to identify which bands disappear

• In critical experiments, use multiple antibodies targeting different TRIM39 epitopes

How can I overcome problems with detecting endogenous TRIM39?

Researchers have noted challenges with detecting endogenous TRIM39. To improve detection:

• Optimize protein extraction with appropriate lysis buffers containing protease inhibitors

• Increase protein loading (50-75 μg per lane)

• Use sensitive ECL detection systems with longer exposure times

• Consider concentrating proteins through immunoprecipitation before Western blotting

• Try antibodies targeting different epitopes, as some may have better sensitivity

• Use alternative techniques like qRT-PCR to validate expression patterns

• Consider using cell lines with higher endogenous TRIM39 expression levels

What are the major pitfalls in TRIM39 antibody-based immunoprecipitation experiments?

Common pitfalls in TRIM39 immunoprecipitation include:

• Weak interactions: TRIM39 interactions with targets like p21 may be transient or weak

• Antibody specificity: Some commercial antibodies may lack specificity for immunoprecipitation

• Post-translational modifications: Ubiquitination and SUMOylation can mask epitopes

• Isoform selectivity: Antibodies may preferentially recognize one isoform over another

Methodological solutions:

• Use crosslinking agents to stabilize protein-protein interactions

• Include N-ethylmaleimide (NEM) to preserve ubiquitination status

• For interaction studies, consider using tagged TRIM39 constructs

• Validate interactions through reciprocal immunoprecipitation

• Include appropriate negative controls (IgG, knockdown samples)

How can I study TRIM39's E3 ubiquitin ligase activity using antibodies?

To investigate TRIM39's E3 ubiquitin ligase function:

• In vitro ubiquitination assay:

  • Purify recombinant TRIM39 (both α and β isoforms)

  • Incubate with ubiquitin, E1, E2 enzymes, and potential substrates

  • Detect ubiquitinated products with anti-ubiquitin antibodies

• Cellular ubiquitination assays:

  • Co-express TRIM39 with tagged ubiquitin and potential substrates

  • Treat cells with proteasome inhibitors (e.g., MG-132) to accumulate ubiquitinated proteins

  • Immunoprecipitate the substrate of interest

  • Probe with anti-ubiquitin antibodies to detect ubiquitination

• TRIM39 RING domain mutants:

  • Generate RING domain mutants as negative controls

  • Compare ubiquitination levels between wild-type and mutant TRIM39

In the case of TRIM39's role as a SUMO-targeted ubiquitin ligase (STUbL), include SUMOylated substrates and detect with SUMO-specific antibodies .

What methodological approaches are effective for studying TRIM39's role in cell cycle regulation and DNA damage response?

To investigate TRIM39's functions in cell cycle and DNA damage response:

• Cell cycle analysis:

  • Use TRIM39 knockdown or overexpression systems combined with flow cytometry

  • Monitor markers of cell cycle progression (cyclin proteins, phospho-histone H3)

  • Analyze BrdU incorporation to assess S-phase entry

• DNA damage experiments:

  • Treat cells with genotoxic agents (doxorubicin, etoposide) after TRIM39 manipulation

  • Monitor p21 levels by Western blot as a critical downstream effector

  • Assess checkpoints using markers like phospho-Chk1, phospho-Chk2

  • Quantify apoptosis using Annexin V staining or caspase activation assays

• Checkpoint abrogation studies:

  • Evaluate G2 checkpoint integrity after TRIM39 depletion

  • Monitor mitotic entry using phospho-histone H3 staining

  • Combine with p21 knockdown to demonstrate dependency of phenotypes

These approaches have revealed that TRIM39 regulates p21 stability, with TRIM39 knockdown leading to reduced p21 levels, increased G1/S transition, and abrogation of DNA damage-induced G2 arrest .

How can researchers effectively study the TRIM39-p21 interaction?

To investigate the TRIM39-p21 interaction, consider these methodological approaches:

• Co-immunoprecipitation studies:

  • Exogenous system: Co-express tagged TRIM39 and p21

  • Endogenous system: Immunoprecipitate TRIM39 and blot for p21

  • Perform reciprocal immunoprecipitation

  • Include controls for specificity (IgG, TRIM39 knockdown)

• GST pull-down assays:

  • Use GST-tagged p21 fragments to map interaction domains

  • Generate point mutations in critical residues (K156 of p21 has been identified as crucial)

  • Test both TRIM39α and TRIM39β for differential binding

• Protein stability assays:

  • Cycloheximide chase experiments to assess p21 half-life

  • Compare p21 stability in TRIM39 knockdown vs. control cells

  • Rescue experiments with wild-type vs. interaction-deficient TRIM39 mutants

Research has shown that TRIM39 interacts with p21 through the C-terminal region (amino acids 152–158) of p21, with K156 being a critical residue for this interaction .

How should I interpret discrepancies in TRIM39 function between different cancer types?

When analyzing seemingly contradictory findings about TRIM39 function:

• Consider tissue-specific contexts:

  • TRIM39 is upregulated and promotes tumor progression in colorectal cancer

  • In hepatocellular carcinoma, both up-regulation and down-regulation have been observed

• Evaluate isoform-specific effects:

  • Different cancer types may express varying ratios of TRIM39α and TRIM39β

  • These isoforms might have distinct functions or interact with different partners

• Analyze protein interaction networks:

  • TRIM39 interacts with p21 to promote stability in some contexts

  • In other contexts, it may interact with MOAP-1 to promote apoptosis

  • In colorectal cancer, it interacts with Rab7 to promote autophagosome-lysosome fusion

• Consider genetic background:

  • p53 status can significantly impact TRIM39 function

  • The presence of other mutations may alter TRIM39's role

What are the technical considerations for using TRIM39 antibodies in tumor tissue samples?

When using TRIM39 antibodies for tumor tissue analysis:

• Sample preparation:

  • Use fresh-frozen samples when possible for protein analysis

  • For FFPE samples, optimize antigen retrieval conditions

  • Include normal adjacent tissue as internal control

• Antibody selection:

  • Choose antibodies validated specifically for IHC/IF in human tissues

  • Consider epitope accessibility in fixed tissues

  • Validate with positive and negative controls

• Interpretation challenges:

  • TRIM39 shows both nuclear and cytoplasmic localization

  • Expression levels vary between tumor and normal tissues

  • Both up-regulation and down-regulation have been observed in different cancers

• Correlation with other markers:

  • Analyze correlation with p21 expression levels

  • Consider relationship with p53 status

  • Evaluate association with clinical parameters and outcomes

In human hepatocellular carcinoma samples, researchers found a significant correlation between p21 abundance and TRIM39 expression levels .

What is the most effective experimental design to study TRIM39's function as a SUMO-targeted ubiquitin ligase (STUbL)?

To investigate TRIM39's STUbL activity:

• Identification of SUMO-interacting motifs (SIMs):

  • Generate TRIM39 mutants with altered SIM domains

  • Test these mutants in binding assays with SUMOylated proteins

  • Compare ubiquitination activity against SUMOylated vs. non-SUMOylated substrates

• In vitro STUbL assays:

  • Generate SUMOylated and non-SUMOylated versions of potential substrates

  • Perform in vitro ubiquitination assays with purified components

  • Compare ubiquitination efficiency between SUMOylated and non-SUMOylated substrates

• Cellular assays:

  • Use SUMO inhibitors like ML-792 to block global SUMOylation

  • Generate SUMOylation-deficient mutants of potential substrates

  • Compare stability and ubiquitination levels of wild-type vs. SUMOylation-deficient proteins

  • Use TRIM39 SIM mutants as negative controls

This approach has revealed that TRIM39 preferentially ubiquitinates SUMOylated forms of NFATc3, and mutation of SUMOylation sites in NFATc3 or SUMO-interacting motifs in TRIM39 reduces their interaction and TRIM39-induced ubiquitination of NFATc3 .

Table 1: Commonly Used TRIM39 Antibodies and Their Applications

Data compiled from search results and research publications

Table 2: TRIM39 Knockdown Methods and Validation Strategies