Progressive Phosphorylation Modulates the Self-Association of a Variably Modified Histone H3 Peptide

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Protein phosphorylation is a critical regulatory mechanism in eukaryotic cells.
• Histone tail phosphorylation is integral to the "histone code" regulating gene expression.
• Intrinsically disordered proteins, like histone tails, undergo complex post-translational modifications.

Purpose of the Study:

• To investigate the association between histone H3 tail peptides with varying phosphorylation states.
• To elucidate the role of phosphorylation levels in modulating peptide interactions and chromatin structure.
• To understand the dynamics of intrinsically disordered proteins in response to phosphorylation.

Main Methods:

• Fully atomistic molecular dynamics simulations of histone H3 tail peptides.
• Comparison of peptide association propensity under different phosphorylation conditions (unmodified, partially modified, fully modified).
• Analysis of inter- and intramolecular interactions using computational methods and experimental validation (Circular Dichroism, NMR spectroscopy).

Main Results:

• Progressive phosphorylation induces specific intermolecular interactions between histone H3 tail peptides.
• Phosphorylation modulates peptide charge, driving specific associations without aggregation.
• Complete phosphorylation reverses this effect, favoring intramolecular interactions and reducing dimerization.

Conclusions:

• A phosphorylation rheostat finely tunes peptide association dynamics in histone tails.
• Phosphorylation thresholds play a crucial role in the behavior of intrinsically disordered proteins.
• These findings offer insights into how histone modifications modulate chromatin structure.