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Updated: Jun 16, 2025

High-Pressure NMR Experiments for Detecting Protein Low-Lying Conformational States
Published on: June 29, 2021
Solution conformational differences between conventional and CENP-A nucleosomes are accentuated by reversible
Kushol Gupta1, Nikolina Sekulić2,3,4, Praveen Kumar Allu5
1Department of Biochemistry & Biophysics, Perelman School of Medicine, University of Pennsylvania, 422 Curie Boulevard, Philadelphia, PA, 19104-6059, USA. kgupta@pennmedicine.upenn.edu.
We compared standard nucleosomes with centromeric nucleosomes using scattering techniques. Histone and DNA sequences impact nucleosome stability under pressure, with centromeric nucleosomes showing greater resilience.
Area of Science:
- Structural Biology
- Biophysics
- Chromatin Biology
Background:
- Nucleosomes, the basic units of DNA packaging, are crucial for genome organization.
- Understanding nucleosome structure and stability is key to deciphering chromosome function.
- Centromeric nucleosomes, containing CENP-A, differ structurally and functionally from canonical nucleosomes.
Purpose of the Study:
- To compare the solution properties and stability of canonical and centromeric nucleosomes.
- To investigate the impact of histone and DNA sequence on nucleosome stability under pressure.
- To establish high-pressure small-angle X-ray scattering (HP-SAXS) as a method for studying nucleosome dynamics.
Main Methods:
- Analytical ultracentrifugation (AUC) for native solution properties.
- Small-angle X-ray scattering (SAXS) and contrast variation small-angle neutron scattering (CV-SANS).
- High-pressure SAXS (HP-SAXS) to assess stability under pressure (300 MPa).
Main Results:
- Established native solution properties of H3 and CENP-A nucleosome core particles (NCPs).
- Demonstrated that histone and DNA sequences influence nucleosome stability under high pressure.
- Observed reversible DNA unwrapping from nucleosomes at high pressure.
- Found centromeric nucleosomes exhibit less increase in radius of gyration than canonical nucleosomes under pressure.
Conclusions:
- Histone and DNA composition significantly affects nucleosome stability in solution.
- Centromeric nucleosomes (with CENP-A) are more stable under pressure than canonical nucleosomes.
- HP-SAXS is a powerful tool for studying nucleosome and chromatin complex dynamics in solution.
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