Stabilization of intramolecular triple/single-strand structure by cationic peptides

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Triple-helical DNA (H-DNA) structures are important in cellular processes.
• Protein interactions, particularly with cationic residues, may stabilize H-DNA.
• Understanding stabilization mechanisms is key to elucidating H-DNA's physiological roles.

Purpose of the Study:

• To investigate the stabilizing effect of cationic protein domains on H-DNA formation.
• To examine the influence of lysine- and arginine-rich oligopeptides on the B-DNA to H-DNA transition.
• To elucidate the role of electrostatic interactions in H-DNA stabilization.

Main Methods:

• Studied the B-DNA to H-DNA transition in the presence of lysine-rich and arginine-rich oligopeptides.
• Assessed the impact of polycations (oligopeptides, spermine) on DNA superhelicity.
• Analyzed electrostatic interactions by comparing polycation and monovalent cation effects.

Main Results:

• Lysine- and arginine-rich oligopeptides, along with spermine, shifted the equilibrium towards H-DNA formation.
• Polycations minimally affected DNA superhelicity, indicating stabilization is not due to torsional stress.
• Arginine-rich peptides demonstrated greater H-DNA stabilization compared to lysine-rich peptides.

Conclusions:

• Electrostatic interactions play a significant role in H-DNA stabilization.
• Arginine-rich peptides may stabilize H-DNA by interacting with and stabilizing unpaired single-stranded regions.
• The findings provide insights into protein-mediated stabilization of triple-helical DNA structures.