Changing chromatin fiber conformation by nucleosome repositioning

Area of Science:

• Molecular Biology
• Biophysics
• Computational Biology

Background:

• Chromatin conformation is dynamic and heterogeneous, influenced by nucleosome positioning.
• Chromatin remodeling complexes alter nucleosome spacing, creating varied chromatin structures.
• The impact of nucleosome repositioning on 3D chromatin structure remains poorly understood.

Purpose of the Study:

• To investigate the effect of nucleosome repositioning on chromatin fiber folding and properties.
• To model the influence of linker DNA length and nucleosome spacing on chromatin conformation.

Main Methods:

• Utilized a coarse-grained computer model of 101 nucleosomes.
• Simulated various chromatin fiber models, with and without linker histones.
• Investigated changes in linker DNA length (in base pair steps) to alter nucleosome positions.

Main Results:

• Nucleosome translocations significantly increased fiber curvature and flexibility, promoting long-range contacts.
• A two-base pair shift from regular spacing caused the highest fiber destabilization.
• Regular nucleosome spacing can stabilize chromatin by facilitating favorable stacking interactions, increasing remodeling energy costs.

Conclusions:

• Nucleosome positioning is a critical determinant of chromatin fiber conformation and properties.
• Computational modeling provides insights into chromatin heterogeneity and regulation of genome compaction.
• Findings advance theoretical models for understanding genome accessibility and regulation.