Ternary complexes in protein-DNA interactions: Kinetics and mechanisms.

Area of Science:

• Molecular Biology
• Biophysics
• Genetics

Background:

• Transcription factors (TFs) regulate gene expression by binding DNA.
• Binary TF·DNA complex mechanisms are well-studied, but ternary complex formation is less understood.
• Ternary complexes involve multiple TFs and DNA, crucial for complex gene regulation.

Purpose of the Study:

• Investigate factors influencing ternary TF·TF·DNA complex formation.
• Analyze the roles of DNA conformation, TF properties, and protein-protein interactions.
• Compare binding mechanisms in Sox2·Oct1·DNA and SRF·SAP1·DNA systems.

Main Methods:

• Coarse-grained molecular dynamics simulations.
• Modeling of two distinct ternary TF·TF·DNA systems.
• Analysis of binding kinetics and molecular mechanisms.

Main Results:

• Nonspecific TF-DNA interactions primarily govern ternary complex formation kinetics.
• DNA conformational changes do not always dominate binding kinetics.
• Binding order depends on TF nonspecific affinities: diffusion-driven for divergent affinities (Sox2·Oct1·DNA) and site-specific for comparable affinities (SRF·SAP1·DNA).

Conclusions:

• Ternary complex formation involves a complex interplay of TF properties, DNA sequence/deformability, and protein-protein interactions.
• Distinct binding mechanisms emerge based on DNA structure and TF affinities.
• Understanding these mechanisms is key to deciphering complex gene regulation.