Nuclear Protein Extraction (High-Salt/Hypotonic Fractionation)

  • Principle
  • Experimental Materials
  • Experimental Procedure
  • Troubleshooting

Materials Required

• Glycerol (HY-B1659)
• DL-Dithiothreitol (HY-15917)
• Ethylenediaminetetraacetic acid (EDTA) (HY-Y0682)
• Polyethylene glycol mono(4-tert-octylphenyl) ether surfactant (HY-Y1883)

Principle

The high-salt/hypotonic fractionation method for nuclear protein extraction is based on the differential solubility of cellular components. Cytoplasmic proteins are extracted first using a hypotonic buffer that causes cell swelling and membrane rupture, followed by centrifugation to separate the cytoplasmic supernatant from the nuclear pellet. The nuclear pellet is then subjected to high-salt extraction (e.g., 0.4 M (NH4)2SO4 or 1 M NaCl) to solubilize tightly bound nuclear matrix proteins, including transcription factors, histones, and structural proteins associated with chromatin and the nuclear scaffold. This approach allows for the isolation of both soluble cytoplasmic proteins and salt-resistant nuclear proteins while minimizing cross-contamination.

MCE has not independently verified the accuracy of these methods. They are for reference only.

Experimental Materials

• Hypotonic lysis buffer (e.g., 10 mM HEPES, pH 7.9, 10 mM KCl, 1.5 mM MgCl2, 1 mM DTT, protease inhibitors)
• High-salt extraction buffer (e.g., 20 mM HEPES, pH 7.9, 400 mM NaCl, 25% glycerol, 1.5 mM MgCl2, 0.2 mM EDTA, 1 mM DTT, protease inhibitors)
• DNase I (RNase-free)
• Triton X-100 (non-ionic detergent)
• NP-40, BSA, Bradford reagent
• DS-PAGE loading buffer
• Centrifuge tubes
• Ice-cold centrifuge, vortex mixer, microcentrifuge, pipettes, ice buckets
• Appropriate cell culture supplies

Experimental Procedure

• 1.Harvest cells (adherent or suspension) and wash with cold PBS.

• 2. Resuspend cells in cold hypotonic lysis buffer supplemented with protease inhibitors.

• 3. Incubate on ice for 10-15 minutes to allow cell swelling.

• 4. Add 0.1% Triton X-100 and vortex briefly to lyse membranes.

• 5. Centrifuge at 1,000 × g for 5 minutes at 4°C to pellet nuclei;
• Collect the supernatant as cytoplasmic fraction.

• 6. Wash the nuclear pellet twice with cold hypotonic buffer.

• 7. Resuspend the pellet in high-salt extraction buffer (e.g., 0.4 M (NH4)2SO4 or 1 M NaCl).

• 8. Incubate on ice for 30 minutes with occasional vortexing.

• 9. Centrifuge at 15,000 × g for 15 minutes at 4°C; the supernatant contains the nuclear extract.

• 10. Quantify protein concentration using Bradford assay.

• 11. Store aliquots at -80°C for long-term use.

Troubleshooting

Contamination of cytoplasmic fraction with nuclear proteins:

• Ensure complete lysis and avoid over-centrifugation during initial steps.

Low yield of nuclear proteins:

• Increase incubation time or salt concentration in high-salt buffer.

Protein degradation:

• Use fresh protease inhibitor cocktail and keep samples on ice throughout the procedure.

Incomplete cell lysis:

• Optimize hypotonic buffer composition and incubation time.

Nuclear pellet loss:

• Handle tubes gently during washing steps and avoid excessive pipetting.

Share