Electrostatic encoding of genome organization principles within single native nucleosomes

Area of Science:

• * Molecular Biology and Biophysics: Investigating the fundamental properties of chromatin organization.

Background:

• * The eukaryotic genome is organized into distinct compartments (A/euchromatin and B/heterochromatin) based on chromatin structure.
• * The role of individual nucleosomes in determining these compartments and their association with transcriptional activity remains unclear.

Purpose of the Study:

• * To determine if individual nucleosomes contain intrinsic biophysical information related to A/B compartment status and gene expression.
• * To investigate the role of nucleosome condensability in genome organization and transcriptional regulation.

Main Methods:

• * Purification of native mononucleosomes to high monodispersity.
• * Assessment of nucleosome condensability using biological polyamines.
• * In silico chromatin polymer simulations.

Main Results:

• * Nucleosome condensability is inversely correlated with A compartment localization and gene expression, particularly near promoters.
• * In silico simulations confirm that nucleosome biophysical properties alone are sufficient for compartment formation.
• * Condensability is an electrostatic phenomenon and its contrast is accentuated upon polyamine depletion.

Conclusions:

• * Individual nucleosomes possess inherent biophysical properties (condensability) that dictate genome organization and gene expression.
• * Nucleosome condensability serves as a key determinant of chromatin state and transcriptional activity.
• * Polyamines are crucial for translating nucleosome biophysical properties into cellular function, with deficiency leading to altered condensability and potential dysfunction.