Alteration in nucleosome structure induced by thermal denaturation.

Area of Science:

• Biochemistry
• Molecular Biology
• Chromatin Structure

Background:

• Mononucleosomes are fundamental units of chromatin, influencing DNA accessibility and gene regulation.
• Goose erythrocyte nuclei provide a model system for studying chromatin organization.

Purpose of the Study:

• To characterize the structural heterogeneity and thermal stability of goose erythrocyte mononucleosomes.
• To investigate the unfolding pathways and morphological changes of mononucleosomes during thermal denaturation.

Main Methods:

• Electrophoresis for component separation.
• Thermal denaturation to assess stability.
• Urea and trypsin treatments for lability studies.
• Electron microscopy for morphological analysis.

Main Results:

• Mononucleosomes exhibited limited heterogeneity in electrophoretic components, histones, and DNA.
• Thermal denaturation yielded two distinct, cooperative melting transitions (T" and T").
• Mononucleosomes began to disrupt in the latter half of T" and fully unfolded after T", forming larger toroids.

Conclusions:

• Goose erythrocyte mononucleosomes possess a stable core structure with defined thermal unfolding transitions.
• Morphological changes correlate with thermal denaturation, revealing distinct intermediate and final states.
• Glutaraldehyde fixation stabilizes the unfolded toroidal structures.