Facilitated diffusion on mobile DNA: configurational traps and sequence heterogeneity

Area of Science:

• Biophysics
• Molecular Biology
• Genomics

Background:

• Proteins search for specific DNA sequences to regulate gene expression.
• Facilitated diffusion is a key mechanism for this search process.
• Understanding how DNA organization and sequence affect this process is crucial for deciphering gene regulation.

Purpose of the Study:

• To investigate the impact of three-dimensional DNA organization and sequence heterogeneity on protein facilitated diffusion along DNA.
• To explore how DNA looping and sequence-based traps influence the efficiency of protein-DNA interactions.

Main Methods:

• Brownian dynamics simulations were employed to model the facilitated diffusion of a protein along a semiflexible DNA polymer.
• The simulations incorporated DNA organization into loops and sequence heterogeneity.

Main Results:

• The search process is highly sensitive to the target's location within DNA loops, suggesting a role for genome topology in gene regulation.
• Sequence heterogeneity generally creates traps that slow down diffusion, but strategically positioned traps can unexpectedly accelerate the search.
• DNA looping in bacterial systems significantly impacts search efficiency based on target localization.

Conclusions:

• Genome organization and sequence heterogeneity are critical factors modulating protein search dynamics on DNA.
• Local changes in genome topology can influence gene expression by altering protein search efficiency.
• Sequence-dependent interactions, including traps, can be fine-tuned to optimize or impede protein-DNA binding events.