Recombinant Human ATXN7L3 Protein: Handling & Usage Protocol

Recombinant Human ATXN7L3 Protein is a key regulatory subunit of the SAGA deubiquitinase (DUB) module that stimulates USP22-mediated removal of monoubiquitin from histone H2B, making it an essential tool for chromatin biology and epigenetic research.

Product Name

Recombinant Human ATXN7L3 Protein

SKU

rp366613

Protein Function

Regulatory subunit of the SAGA DUB module; activates USP22 deubiquitinase activity toward histone H2B

Species Origin

Human (Homo sapiens)

Primary Research Application

Chromatin biology, epigenetics, deubiquitinase complex reconstitution assays

Storage Recommendation

Avoid repeated freeze-thaw cycles; store aliquots at -80°C for long-term stability

Background and Biological Significance of ATXN7L3

Ataxin-7-like protein 3 (ATXN7L3) is a non-catalytic but functionally indispensable subunit of the deubiquitinase (DUB) module within the Spt-Ada-Gcn5 acetyltransferase (SAGA) transcriptional coactivator complex. The SAGA DUB module, conserved from yeast to humans, is responsible for removing the monoubiquitin mark from histone H2B at lysine 120 (H2Bub1), a modification closely linked to transcriptional elongation, DNA damage response, and gene regulation.

ATXN7L3 functions as an activating scaffold that bridges USP22 (the catalytic deubiquitinase) and ENY2 within the DUB module, dramatically stimulating USP22 enzymatic activity. Loss of ATXN7L3 leads to global accumulation of H2Bub1, underscoring its central role in maintaining proper histone ubiquitination homeostasis. Beyond the canonical SAGA complex, ATXN7L3 has been found to participate in additional DUB complexes, broadening its regulatory significance in transcription and chromatin remodeling.

Recombinant Human ATXN7L3 Protein (rp366613) provides researchers with a well-defined, ready-to-use tool to study these molecular mechanisms in vitro, enabling biochemical reconstitution of the DUB module and functional dissection of ATXN7L3 interactions.

Reconstitution and Storage Protocol

Materials Required: Sterile ultrapure water or an appropriate aqueous buffer (e.g., 20–50 mM Tris-HCl, pH 7.4–8.0, with 150 mM NaCl and 10% glycerol), low-protein-binding microcentrifuge tubes, dry ice or liquid nitrogen for snap-freezing.

Reconstitution Steps:

1. Briefly centrifuge the lyophilized vial (if applicable) at low speed before opening to collect any powder at the bottom of the tube.
2. Add the recommended volume of sterile reconstitution buffer slowly along the wall of the vial to avoid foaming. Gently swirl or pipette to dissolve; do not vortex vigorously.
3. Allow the solution to equilibrate at room temperature for 5–10 minutes with occasional gentle mixing until fully dissolved.
4. Centrifuge the reconstituted solution briefly at 10,000 × g for 1 minute to remove any insoluble aggregates.
5. Verify solubilization visually; the solution should be clear to slightly opalescent.

Storage Instructions:

• For short-term use (up to 1 week): store at 4°C in a suitable stabilizing buffer containing a carrier protein (e.g., 0.1% BSA) and a protease inhibitor cocktail.
• For long-term storage: prepare single-use aliquots to avoid repeated freeze-thaw cycles and store at -80°C. Each freeze-thaw cycle can result in partial loss of protein activity and integrity.
• Do not store at -20°C as frost-free freezers with cycling temperatures can be detrimental to protein stability.

Note: Specific reconstitution buffer composition, concentration, and storage conditions provided in the product datasheet (absea#PP-2190) take precedence over general guidelines. Consult the datasheet before use.

Quality Control and Purity Verification

Prior to use in sensitive biochemical assays, it is recommended to verify the quality and integrity of the Recombinant Human ATXN7L3 Protein using the following standard procedures:

SDS-PAGE Analysis: Run a small aliquot (1–2 µg) on a denaturing polyacrylamide gel under reducing conditions. The protein band should appear at the expected molecular weight corresponding to ATXN7L3. Staining with Coomassie Brilliant Blue or silver stain allows assessment of purity and the presence of any degradation products or contaminants.

Western Blot Confirmation: Transfer resolved protein to a PVDF or nitrocellulose membrane and probe with a validated anti-ATXN7L3 antibody to confirm protein identity. This step is particularly important if batch-to-batch consistency needs to be documented.

Protein Concentration Determination: Measure protein concentration using a BCA or Bradford assay. Use BSA standards prepared in the same buffer as the protein sample to minimize matrix effects. Spectrophotometric A280 measurement may also be used if the extinction coefficient for ATXN7L3 is known.

Functional Activity Assessment: Where activity data are critical, incorporate ATXN7L3 into an in vitro DUB module reconstitution assay with USP22 and ENY2, then measure deubiquitinase activity against a fluorogenic ubiquitin substrate or H2Bub1-containing nucleosome substrate. Comparison to a reference standard ensures lot-to-lot consistency.

Consult the Certificate of Analysis (CoA) supplied with the product (absea#PP-2190) for lot-specific purity and QC data.

Experimental Applications

Recombinant Human ATXN7L3 Protein (rp366613) is suited for a range of biochemical and cell-free research applications:

1. In Vitro DUB Module Reconstitution: ATXN7L3 is an essential activating component for assembling a functional SAGA DUB sub-complex in vitro. When combined with recombinant USP22 and ENY2, the reconstituted trimeric complex demonstrates robust deubiquitinase activity, enabling mechanistic studies of H2Bub1 removal and the regulatory role of ATXN7L3.

2. Protein–Protein Interaction Studies: Use ATXN7L3 as bait or prey in pull-down assays, co-immunoprecipitation (co-IP) experiments, or surface plasmon resonance (SPR) measurements to map its interactions with USP22, ENY2, and other potential binding partners. GST- or His-tagged versions may facilitate affinity capture.

3. Structural Biology: Recombinant ATXN7L3 can serve as a component in cryo-electron microscopy (cryo-EM) or X-ray crystallography studies aimed at elucidating the architecture of the SAGA DUB module and the molecular basis of its activation mechanism.

4. Biochemical Inhibitor Screening: The protein can be incorporated into high-throughput or targeted screening platforms designed to identify small-molecule inhibitors or modulators of the ATXN7L3–USP22 interaction, with potential relevance to cancer biology given the oncogenic roles associated with SAGA complex dysregulation.

5. Antibody Validation: Recombinant ATXN7L3 serves as a positive control antigen for validating anti-ATXN7L3 antibodies in Western blot, ELISA, or immunofluorescence applications.

Troubleshooting Common Issues

The following troubleshooting guidance addresses issues commonly encountered when working with recombinant proteins such as ATXN7L3:

Problem: Protein precipitation or aggregation upon reconstitution
Possible causes: reconstitution buffer ionic strength or pH is inappropriate; protein was reconstituted too quickly or at too high a concentration.
Solutions: ensure the buffer composition matches the recommended formulation in the datasheet; reconstitute at a lower concentration and dilute as needed; add a mild detergent (e.g., 0.01–0.05% Tween-20) or glycerol (5–10%) to the buffer to improve solubility; reconstitute on ice.

Problem: Low or absent deubiquitinase activity in DUB reconstitution assays
Possible causes: protein has undergone multiple freeze-thaw cycles; assay buffer is incompatible; ATXN7L3 alone is not catalytic and requires USP22 and ENY2 for activity.
Solutions: use freshly thawed, single-use aliquots; verify that recombinant USP22 and ENY2 are also present and active; confirm assay buffer pH and salt concentration are within optimal range; include a positive control with validated active complex.

Problem: Multiple or unexpected bands on SDS-PAGE
Possible causes: partial proteolytic degradation due to freeze-thaw damage or protease contamination; post-translational modifications.
Solutions: always use protease inhibitor cocktail in working buffers; work on ice; verify the expected molecular weight with the product datasheet and CoA; contact Aladdin Scientific technical support if unexpected bands persist.

Problem: Inconsistent results between experiments
Possible causes: protein concentration measured inaccurately; pipetting errors during dilution; different aliquot storage times.
Solutions: standardize protein quantification method across experiments; prepare a fresh working dilution from a single aliquot for each experiment; record lot number and aliquot thaw date for traceability.

Frequently asked questions

What is the biological role of ATXN7L3 in the SAGA complex?

ATXN7L3 is a non-catalytic regulatory subunit of the SAGA DUB module that directly activates USP22, the catalytic deubiquitinase responsible for removing monoubiquitin from histone H2B at K120. By acting as an activating scaffold that bridges USP22 and ENY2, ATXN7L3 is essential for proper H2Bub1 regulation, transcriptional control, and DNA damage response. Without ATXN7L3, H2Bub1 levels accumulate globally across the genome.

How should Recombinant Human ATXN7L3 Protein be stored to maintain stability?

For optimal stability, prepare single-use aliquots of the reconstituted protein and store them at -80°C for long-term preservation. Avoid repeated freeze-thaw cycles, as each cycle can progressively degrade protein activity and integrity. For short-term use within one week, aliquots can be kept at 4°C in a stabilizing buffer containing a carrier protein such as 0.1% BSA. Always consult the product datasheet (absea#PP-2190) for lot-specific storage recommendations.

Can Recombinant Human ATXN7L3 Protein be used alone to measure deubiquitinase activity?

No. ATXN7L3 itself lacks intrinsic deubiquitinase catalytic activity. It functions as an activating regulatory subunit that dramatically stimulates the deubiquitinase activity of USP22. To measure DUB activity in vitro, ATXN7L3 must be combined with recombinant USP22 (the catalytic subunit) and ENY2 to reconstitute the functional trimeric DUB module. Ensure all three components are present, active, and at appropriate stoichiometric ratios for reliable activity measurements.

What are typical quality control criteria for this recombinant protein?

Quality control typically includes SDS-PAGE to confirm the apparent molecular weight and assess purity, Western blot with a validated anti-ATXN7L3 antibody to confirm protein identity, and protein concentration determination by BCA or Bradford assay. Lot-specific purity values and QC data are provided in the Certificate of Analysis (CoA) accompanying each product unit. For functional applications, activity confirmation in a reconstituted DUB assay system is also recommended.

Is Recombinant Human ATXN7L3 Protein suitable for structural biology studies such as cryo-EM?

Recombinant Human ATXN7L3 Protein can serve as a component in structural biology investigations, including cryo-EM and X-ray crystallography, particularly when assembled with USP22 and ENY2 into the trimeric DUB module. The suitability for structural studies depends on protein purity, homogeneity, and the absence of aggregation. Researchers undertaking structural work should verify these parameters by dynamic light scattering (DLS) or size-exclusion chromatography (SEC) in addition to standard SDS-PAGE QC.

References

1. Zhao Y et al. A TFTC/STAGA module mediates histone H2A and H2B deubiquitination, coactivates nuclear receptors, and counteracts heterochromatin silencing. Molecular Cell, 2008.
2. Lang G et al. Role of the chromatin-associated factor Sgf73/ATXN7 in DUB complex assembly and regulation. EMBO Journal, 2011.
3. Samara NL et al. Structural insights into the assembly and function of the SAGA deubiquitinating module. Science, 2010.
4. Atanassov BS et al. ATXN7L3 and ENY2 coordinate activity of multiple H2B deubiquitinases important for cellular proliferation and tumor growth. Molecular Cell, 2016.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.