Modeling H3 histone N-terminal tail and linker DNA interactions

Area of Science:

• Structural biology
• Computational biophysics
• Molecular modeling

Background:

• Chromatin, the complex of DNA and proteins that forms chromosomes, plays a crucial role in gene regulation.
• Histone proteins, particularly their N-terminal tails, are known to interact with DNA and influence chromatin structure.
• Understanding these interactions at a molecular level is key to deciphering gene expression and cellular processes.

Purpose of the Study:

• To investigate the molecular dynamics of the H3 histone N-terminal tail interacting with linker DNA.
• To model the behavior of histone-DNA interactions in a simplified chromatin environment.
• To elucidate the structural and dynamic changes occurring upon binding.

Main Methods:

• Utilized molecular dynamics (MD) computer simulations.
• Simulated a 25-residue N-terminal tail of the H3 histone protein.
• Modeled interactions with a 10 base pair (bp) DNA segment, representing linker DNA.

Main Results:

• DNA presence enhanced the protein's secondary structure content, though motif locations varied with DNA orientation.
• Electrostatic attraction between DNA and protein was screened by water and counteracted by protein hydrophobic compaction.
• Protein secondary structure limited DNA coverage to 4-5 bp, indicating specific binding constraints.

Conclusions:

• The H3 tail's compaction and charge density suggest a role in nonspecific DNA bending and plasticity.
• These properties are relevant for linker DNA behavior in the crowded environment of dense chromatin.
• The findings contribute to understanding the fundamental mechanisms of chromatin organization and regulation.