Downsizing the Histone H3-H4 Quaternary Structure Into Foldamer Mimetics Yields High-Affinity and Cell-Permeable...

Area of Science:

• Chemical Biology
• Structural Biology
• Biochemistry

Background:

• Mimicking complex protein-protein interactions with small molecules is a significant challenge.
• The histone chaperone Anti-Silencing Function 1 (ASF1) plays a crucial role in DNA replication and repair.
• Understanding the H3-H4 dimer interaction with ASF1 is key for developing targeted therapeutics.

Purpose of the Study:

• To design small, stable, and cell-permeable peptide-oligourea foldamers that mimic the histone H3-H4 dimer interface.
• To create high-affinity ligands for the histone chaperone ASF1.
• To validate the intracellular target engagement of these foldamer mimetics.

Main Methods:

• Utilized a foldamer-based downsizing strategy to compress the H3-H4 dimer architecture.
• Employed high-resolution co-crystal structures for rational design of foldamer mimetics.
• Performed systematic optimization of linker geometry, epitope mimicry, charge, and N-methylation.
• Assessed ligand affinity, stability, proteolytic resistance, and cytosolic penetration.

Main Results:

• Developed peptide-oligourea hybrids that accurately reproduce H3 α-helix and H4 β-strand epitopes.
• Achieved nanomolar affinities and enhanced stability and proteolytic resistance.
• Demonstrated robust cytosolic penetration and effective intracellular recognition of endogenous ASF1.
• Optimized constructs recapitulated the native H3-H4 dimer binding mode on ASF1 with high fidelity.

Conclusions:

• Peptide-oligourea foldamers can successfully mimic protein quaternary structure surfaces.
• This strategy yields high-affinity, stable, and cell-permeable ligands for protein targets.
• The developed foldamers represent promising tools for chemical biology and potential therapeutic agents.