Histone H3 tail charge patterns govern nucleosome condensate formation and dynamics

Area of Science:

• Molecular Biology
• Biophysics
• Genomics

Background:

• Chromatin organization is crucial for nuclear function.
• Emerging evidence suggests chromatin forms distinct microenvironments via phase separation.
• Histone post-translational modifications are key regulators of chromatin structure.

Purpose of the Study:

• To investigate how histone modifications influence nucleosome phase behavior.
• To understand the role of H3 tail charge distribution in nucleosome phase separation.

Main Methods:

• Systematic alteration of charge distribution in the H3 tail.
• Microscopy-based assays and microrheology to analyze nucleosome condensates.
• Nuclear magnetic resonance (NMR) relaxation experiments and simulations.

Main Results:

• Specific regions of the H3 tail modulate the phase boundary and viscosity of nucleosome condensates.
• H3 tails remain dynamically mobile within condensates, correlating with viscosity.
• The number, identity, and arrangement of basic residues in the H3 tail critically regulate phase separation.

Conclusions:

• Nucleosome intrinsic properties and modifications actively shape local chromatin microenvironments.
• Findings provide insight into the role of histone modifications in chromatin condensate formation.
• This work supports models where nucleosomes actively organize nuclear architecture.