vgl1 Antibody

What is VGLL1/vgl1 and what cellular functions does it perform?

VGLL1 (Vestigial-like 1) is a transcription cofactor that belongs to the vigilin family of proteins containing multiple KH domains, which are known RNA-binding motifs. In humans, VGLL1 functions as a specific coactivator for the mammalian TEFs (Transcription Enhancer Factors) and can bind proteins of the TEA domain family of transcription factors . The VGLL1-TEFs complex upregulates the expression of genes such as IGFBP-5, which promotes cell proliferation .

In fission yeast, the homolog Vgl1 is a multi-KH domain protein that plays a crucial role in heterochromatin-mediated gene silencing . Research indicates that Vgl1 is required for heterochromatin formation and functions by directly interacting with Clr4, the sole H3K9 methyltransferase in fission yeast . Under normal conditions, Vgl1 is primarily cytoplasmic with significant enrichment at the endoplasmic reticulum (ER) .

Interestingly, upon thermal stress, Vgl1 rapidly relocalizes from the ER to cytoplasmic granules that resemble stress granules (SGs) . These granules contain RNA and proteins typically found in mammalian SGs, including Pabp, G3BP, and components of the eIF3 translation initiation complex . This dynamic relocalization suggests that Vgl1 plays an important role in the cellular response to environmental stresses, potentially through regulating RNA metabolism.

What types of vgl1 antibodies are currently available for research?

Several types of vgl1/VGLL1 antibodies are available for research purposes, each with distinct characteristics suitable for different applications:

Rabbit polyclonal antibodies typically target various regions of the VGLL1 protein, such as the 84-134 amino acid region . These antibodies are often affinity-purified using epitope-specific immunogen to enhance specificity.

Different antibodies are optimized for specific applications, with some validated for multiple techniques. For instance, the rabbit polyclonal antibody described in search result #7 has been validated for Western blot, immunohistochemistry, immunofluorescence, immunoprecipitation, RNA immunoprecipitation, and ELISA applications with reactivity across human, mouse, and rat samples.

When selecting a vgl1 antibody, researchers should consider the specific requirements of their experiment, including the application, species reactivity, and target epitope. The observed molecular weight for VGLL1 is typically between 26-29 kDa, which is close to the calculated molecular weight of 29 kDa .

What are the common applications for vgl1 antibodies in laboratory research?

VGLL1/vgl1 antibodies are utilized in a range of laboratory applications for studying the protein's expression, localization, interactions, and function:

Western Blotting (WB): For detecting VGLL1 protein expression in cell and tissue lysates. The typical dilution range is 1:1000-1:6000 . This application has been validated in multiple cell lines including Jurkat cells, PC-3 cells, and various tissue samples including human, mouse, and rat brain and spleen tissues .

Immunohistochemistry (IHC): For visualizing VGLL1 distribution in tissue sections. The recommended dilution is 1:20-1:200 , with antigen retrieval using TE buffer pH 9.0 or citrate buffer pH 6.0. Positive IHC has been detected in human prostate cancer tissue .

Immunofluorescence (IF): For studying the subcellular localization of VGLL1 in cultured cells or tissue sections. This is particularly useful for observing its dynamic relocalization during stress responses .

Immunoprecipitation (IP): For isolating VGLL1 protein complexes to study protein-protein interactions. This technique has been crucial in demonstrating direct interactions between Vgl1 and other proteins such as Clr4 .

RNA Immunoprecipitation (RIP): For investigating RNA-protein interactions involving VGLL1, which is particularly relevant given its multiple KH domains that function as RNA-binding motifs .

Chromatin Immunoprecipitation (ChIP): While not specifically mentioned for VGLL1 in the search results, ChIP is a relevant application for transcription cofactors to study their association with specific genomic regions, especially given Vgl1's role in heterochromatin formation .

These diverse applications enable comprehensive investigation of VGLL1/vgl1's biological functions, including its roles in transcriptional regulation, stress response, and heterochromatin-mediated gene silencing.

What dilutions and protocols are recommended for vgl1 antibodies in different applications?

The recommended dilutions and protocols for vgl1/VGLL1 antibodies vary depending on the specific antibody and application:

Western Blot (WB):

• Dilution range: 1:500-2000 or 1:1000-1:6000

• Sample preparation: For yeast studies, whole-cell protein extracts can be prepared by alkaline extraction with 0.3 M NaOH followed by trichloroacetic acid precipitation

• Detection: Anti-PAP antibody has been used to reveal Vgl1-TAP proteins

Immunohistochemistry (IHC):

• Dilution range: 1:20-1:200

• Antigen retrieval: TE buffer pH 9.0 or alternatively citrate buffer pH 6.0

• Positive control tissues: Human prostate cancer tissue

Immunofluorescence (IF):

• Dilutions should be optimized for each specific antibody

• For studying Vgl1 localization during stress: Time-course experiments capturing relocalization at 2, 5, 10, and 60 minutes after stress induction

Immunoprecipitation (IP):

• For co-IP studies: Anti-Myc antibody has been used for immunoprecipitation followed by Western blotting with anti-HA antibody to detect protein-protein interactions

Storage and Handling:

• Storage temperature: -20°C for up to 1 year from receipt date

• Avoid repeated freeze-thaw cycles

• Formulation: Typically supplied in PBS containing 50% Glycerol, 0.5% BSA, and 0.02% Sodium Azide

These recommendations serve as starting points, and optimal conditions may vary depending on the specific experimental system. Researchers should perform titration experiments to determine the optimal dilution for their specific application and sample type. For reproducible results, maintaining consistent protocols once optimized is advisable.

How does Vgl1 contribute to heterochromatin formation and gene silencing?

Vgl1 plays a crucial role in heterochromatin formation and gene silencing through direct interaction with the H3K9 methyltransferase Clr4 in fission yeast. The molecular mechanism involves several key components:

Clr4 Recruitment: Vgl1 is essential for proper recruitment of Clr4 to pericentromeric heterochromatin. ChIP experiments showed that FLAG-Clr4 association with centromeres was reduced to background levels in vgl1-deleted cells . This indicates that Vgl1 serves as a critical factor for proper localization of the methyltransferase to heterochromatic regions.

Direct Physical Interaction: Multiple experimental approaches have demonstrated that Vgl1 physically interacts with Clr4:

• Coimmunoprecipitation experiments showed that Vgl1 associates with Clr4 in vivo

• Reciprocal immunoprecipitation confirmed this interaction

• GST pulldown assays with recombinant GST-Clr4 and His-tagged Vgl1 demonstrated direct binding in vitro

H3K9 Methylation Regulation: Through its interaction with Clr4, Vgl1 regulates H3K9 methylation, a key epigenetic mark associated with heterochromatin formation and gene silencing. In vgl1-deleted cells, the loss of Clr4 recruitment results in impaired H3K9 methylation .

RNA-Dependent Mechanism: Importantly, the binding of Vgl1 to heterochromatin is RNA-dependent. When cell lysates were treated with RNase before immunoprecipitation, Vgl1 localization to pericentromeric heterochromatin was disrupted . This finding suggests that RNA plays a critical role in recruiting or stabilizing Vgl1 at heterochromatic regions.

This mechanism highlights Vgl1's importance as a connector between the CLRC (Clr4-containing) complex and centromeric heterochromatin, providing insight into how RNA-binding proteins contribute to epigenetic regulation and gene silencing. The dual capacity of Vgl1 to bind both RNA and the H3K9 methyltransferase makes it a key player in the establishment and maintenance of heterochromatin.

What role does Vgl1 play in cellular stress response mechanisms?

Vgl1 performs a significant role in cellular stress response mechanisms, particularly during thermal stress. The protein undergoes a remarkable dynamic relocalization under stress conditions and is involved in the formation of stress granules (SGs). Several key aspects of this process have been elucidated:

Dynamic Relocalization Timeline: Upon thermal stress, Vgl1 undergoes a rapid and precisely timed relocation from the endoplasmic reticulum (ER) to cytoplasmic granules:

• Within 2 minutes: Accumulation of Vgl1 at the ER disappears

• Around 5 minutes: Small patches of granule-like structures begin to appear

• By 10 minutes: Granule structures become clearly evident

• Up to 60 minutes: These structures remain stable

• After stress removal: Granules rapidly disperse, and Vgl1 reaccumulates at the ER

Stress Granule Composition: The cytoplasmic granules formed by Vgl1 under thermal stress appear to be equivalent to mammalian stress granules:

• They can be separate from P-bodies

• They contain RNA, as demonstrated by SYTO nucleic acid stains

• They contain proteins typically found in mammalian SGs, including Pabp, G3BP, and components of the eIF3 translation initiation complex

RNA Trafficking Function: Vgl1 appears to escort RNA from ER-associated polyribosomes to the cytosol under thermal stress. This is supported by:

• Overlap of Vgl1 granules with RNA stains

• Shift of Vgl1 signal to the top of the gradient during sucrose gradient fractionation upon polysome disruption by thermal stress

Cell Survival Promotion: Vgl1 plays a crucial role in promoting cell survival under thermal stress. Vgl1-deletion mutants (vgl1Δ) were more susceptible to thermal stress and lost viability more rapidly than wild-type cells when incubated at high temperatures .

Unique Regulatory Features: Unlike in mammalian cells but similar to trypanosomes and S. cerevisiae, the assembly of Vgl1-containing SGs in S. pombe is independent of eIF2α phosphorylation and is not induced by oxidative stress . Additionally, assembly of these granule-like structures is blocked by trapping mRNAs in polysomes with cycloheximide .

These findings highlight Vgl1's important role in promoting cell survival during stress conditions, likely by regulating RNA metabolism and translation in response to adverse environmental conditions.

What approaches can be used to study Vgl1 protein-protein and protein-RNA interactions?

Several experimental approaches can be employed to study Vgl1 protein-protein and protein-RNA interactions, each with specific advantages for uncovering different aspects of Vgl1's molecular functions:

Protein-Protein Interaction Methods:

• Coimmunoprecipitation (Co-IP): This technique has successfully demonstrated interactions between Vgl1 and other proteins such as Clr4 :

  • Immunoprecipitation with anti-Myc antibody for Myc-tagged Vgl1

  • Western blotting with anti-HA antibody for HA-tagged potential interaction partners

  • Reciprocal immunoprecipitation to confirm specificity

• GST pulldown assays: This in vitro method confirmed direct interaction between Vgl1 and Clr4 :

  • Using recombinant GST-Clr4 and His-tagged Vgl1

  • Pulldown followed by detection of bound proteins

• Mass spectrometry-based approaches:

  • Hydrogen/deuterium exchange mass spectrometry (HDXMS) can be used to study conformational changes upon binding

  • Immunoprecipitation followed by mass spectrometry to identify novel interaction partners

Protein-RNA Interaction Methods:

• RNA Immunoprecipitation (RIP): This technique has been validated for Vgl1 antibodies and involves:

  • Immunoprecipitation of Vgl1 complexes

  • Extraction and analysis of associated RNAs

  • RT-PCR or sequencing to identify bound RNAs

• RNase treatment experiments: Treating cell lysates with RNase before immunoprecipitation demonstrated that Vgl1 binding to heterochromatin is RNA-dependent .

• Sucrose gradient fractionation: This technique was used to monitor Vgl1-containing complexes and their association with polysomes during stress response .

• RNA visualization: SYTO nucleic acid stains were used to show that Vgl1 granules contained RNA during stress response .

Additional Approaches:

• Fluorescence microscopy: To visualize colocalization of Vgl1 with potential interaction partners or RNA during normal conditions and stress response .

• Biochemical fractionation: To separate cellular compartments and determine the distribution of Vgl1 and its interaction partners.

Each method has strengths and limitations, and combining multiple approaches provides more robust evidence for specific interactions. For studying the dynamic nature of Vgl1 interactions, particularly during stress responses, time-course experiments are particularly valuable to capture the rapidly changing interaction landscape.

What controls should be implemented when using vgl1 antibodies for chromatin studies?

When using vgl1 antibodies for chromatin studies such as Chromatin Immunoprecipitation (ChIP), implementing proper controls is essential for ensuring reliable and interpretable results:

Genetic Controls:

• Knockout/Knockdown Controls: The most stringent control for antibody specificity involves comparing ChIP results between wild-type and vgl1Δ (knockout) samples. As shown in search result #11, knockout cell lines provide superior controls for antibody validation, especially for immunofluorescence imaging.

• Overexpression Controls: Cells overexpressing tagged versions of Vgl1 can serve as positive controls to validate antibody performance and optimize ChIP conditions.

Antibody Controls:

• IgG Control: A non-specific IgG from the same species as the vgl1 antibody serves as a negative control to assess background signal. This is particularly important given that result #11 indicates approximately 50% of commercial antibodies fail to meet basic standards for characterization.

• Multiple Antibody Validation: If available, using multiple antibodies targeting different epitopes of Vgl1 can increase confidence in the specificity of observed signals.

• Blocking Peptide: A peptide competition assay, where the antigenic peptide is pre-incubated with the antibody before ChIP, can demonstrate specificity.

Technical Controls:

• Input DNA: Always include input DNA (pre-immunoprecipitation sample) as a reference for normalization and to assess the efficiency of immunoprecipitation.

• Positive and Negative Genomic Regions: Include primers for regions known to be associated with Vgl1 (pericentromeric regions would be appropriate positive controls based on result #5) and regions expected to lack Vgl1 binding.

• RNase Treatment: Since result #5 indicates that Vgl1 binding to heterochromatin is RNA-dependent, comparing ChIP results with and without RNase treatment provides insight into the RNA-dependence of observed interactions.

Cross-validation Approaches:

• Alternative Methods: Validate ChIP results using complementary approaches such as CUT&RUN or CUT&Tag, which may offer improved signal-to-noise ratios.

• Sequential ChIP (Re-ChIP): To confirm co-occupancy of Vgl1 with other factors (like Clr4) at specific genomic loci.

Result #13 highlights that for ChIP applications, an antibody must recognize its target in the context of chromatin, usually formaldehyde-fixed chromatin, and typically requires high-titer antibodies for effective immunoprecipitation, making proper controls even more critical.

How can researchers troubleshoot inconsistent results with vgl1 antibodies?

Inconsistent results with vgl1 antibodies can arise from various sources. Here's a systematic approach to troubleshooting:

Antibody Quality Assessment:

• Validation verification: Search result #11 indicates that ~50% of commercial antibodies fail to meet basic standards. Verify that your antibody has been properly validated for your specific application.

• Lot-to-lot variability: Result #6 discusses inter-laboratory reproducibility of antibody testing. The table below shows the intra-class correlation coefficient (ICC) data from this study, demonstrating that antibody reproducibility can vary:

• Independent validation: Conduct Western blots to confirm specificity before using the antibody in more complex applications. If possible, include a vgl1 knockout/knockdown sample as a negative control.

Technical Optimization:

• Antibody titration: Test a range of dilutions to find the optimal concentration. The recommended ranges include 1:500-2000 for Western blots and 1:20-1:200 for IHC .

• Buffer optimization: For Western blots of yeast samples, result #8 describes a specific extraction protocol using 0.3 M NaOH and trichloroacetic acid precipitation.

• Sample preparation consistency: For applications like ChIP where chromatin fragmentation quality is critical, ensure consistent sample preparation methods.

Application-Specific Troubleshooting:

• Western Blot issues:

  • The observed molecular weight of VGLL1 is 26-29 kDa , so confirm you're analyzing the correct band

  • Try different membrane types and transfer conditions

  • Optimize blocking agents (BSA vs. milk)

• Immunoprecipitation problems:

  • Result #5 demonstrates successful co-IP with epitope-tagged proteins, which may provide more consistent results than antibodies against the native protein

  • Consider that Vgl1 binding to heterochromatin is RNA-dependent , so RNase contamination could affect results

• Immunofluorescence inconsistencies:

  • Result #8 shows that Vgl1 localization changes dramatically under stress conditions, so ensure consistent cell culture conditions

  • Try different fixation methods that may better preserve epitope recognition

Biological Variables:

• Stress response effects: Vgl1 rapidly relocalizes within minutes under thermal stress , potentially affecting antibody accessibility

• Cell type differences: Expression levels and post-translational modifications may vary between cell types

Result #11 emphasizes that recombinant antibodies generally outperform both monoclonal and polyclonal antibodies across different assays. If available, switching to a recombinant anti-vgl1 antibody might provide more consistent results.

What techniques are most reliable for studying Vgl1 localization during stress conditions?

To study Vgl1 localization during stress conditions, particularly its dynamic relocalization from the endoplasmic reticulum to cytoplasmic stress granules under thermal stress, several complementary techniques can be employed:

Live Cell Imaging with Fluorescently Tagged Vgl1:
This approach allows real-time tracking of Vgl1 movement during stress responses. Result #8 used this technique to observe the precise timeline of Vgl1 relocalization:

• Within 2 minutes: Disappearance from ER

• Around 5 minutes: Formation of small granule-like structures

• By 10 minutes: Establishment of stable granules

• After stress removal: Reverse process of granule disassembly

Immunofluorescence with Co-staining:
This technique can reveal the relationship between Vgl1 and other cellular components during stress:

• ER markers to confirm initial localization

• Stress granule markers (Pabp, G3BP, eIF3 components)

• P-body markers to distinguish from these related structures

• RNA staining (SYTO nucleic acid stains) to confirm RNA content of granules

Biochemical Fractionation:
Sucrose gradient fractionation provides quantitative data on Vgl1 association with different cellular complexes:

• Under normal conditions: Vgl1 associates with polysome fractions

• During thermal stress: Vgl1 shifts to the top fractions of the gradient

Pharmacological Manipulations:
These can provide mechanistic insights into Vgl1 granule formation:

• Cycloheximide treatment blocks Vgl1 granule assembly by trapping mRNAs in polysomes

• Unlike in mammalian cells, eIF2α phosphorylation inhibitors do not affect Vgl1 granule formation in yeast

Experimental Design Considerations:

• Time-course experiments: Given the rapid dynamics of Vgl1 relocalization (within minutes), careful time-course experiments are essential.

• Temperature control: Precise control of temperature is critical for reproducible thermal stress experiments.

• Recovery phases: Including recovery phases after stress removal provides insights into the reversibility of granule formation.

• Comparative analysis: Comparing wild-type cells with vgl1Δ mutants reveals the functional significance of relocalization, as these mutants show decreased viability under thermal stress .

The combination of these approaches provides a comprehensive understanding of Vgl1 localization dynamics during stress conditions. The rapid and reversible nature of Vgl1 relocalization makes this protein an excellent model for studying stress granule assembly and disassembly mechanisms.