The structure of the chromatin core particle in solution

Area of Science:

• Structural biology
• Biophysics
• Molecular genetics

Background:

• Chromatin is the complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells.
• The nucleosomal core particle is the fundamental repeating unit of chromatin.

Purpose of the Study:

• To determine the three-dimensional shape and size of the nucleosomal core particle.
• To elucidate the spatial arrangement of DNA and proteins within the core particle.

Main Methods:

• Analysis of neutron scattering data from dilute solutions.
• Analysis of X-ray scattering data from dilute solutions.
• Computational modeling and comparison of scattering profiles from various structural models.

Main Results:

• A single structural model accurately explained both X-ray and neutron scattering data.
• The nucleosomal core particle adopts an oblate shape, approximately 50Å in height and 110Å in diameter.
• DNA is localized to two annuli at the top and bottom of the particle.
• A compact protein core, approximately 40Å high and 73Å in diameter, forms the interior of the particle.

Conclusions:

• The study provides a detailed structural model for the nucleosomal core particle.
• The findings clarify the arrangement of DNA and protein within this fundamental chromatin unit.
• This structural information is crucial for understanding chromatin organization and function.