DNA Internal Motion Likely Accelerates Protein Target Search in a Packed Nucleoid

Area of Science:

• Molecular Biology
• Biophysics
• Computational Biology

Background:

• Transcription factors, like lac repressor (LacI), navigate dense, coiled DNA to locate binding sites.
• Understanding protein diffusion within the crowded bacterial nucleoid is crucial for gene regulation insights.

Purpose of the Study:

• To investigate the diffusion dynamics of lac repressor (LacI) within the confined and dynamic environment of the Escherichia coli nucleoid.
• To challenge the canonical view of free diffusion and propose a more accurate model for LacI motion.

Main Methods:

• Utilized a coarse-grained computational model of DNA and LacI within the E. coli nucleoid.
• Performed simulations to analyze LacI diffusion patterns and interactions with DNA.

Main Results:

• LacI diffusion is significantly influenced by the dense packing and high mobility of DNA, not free diffusion.
• Introduced the concept of 'gated diffusion' where LacI moves between DNA-defined cages.
• Simulated 3D diffusion constants for unbound LacI align with experimental in vivo data.

Conclusions:

• The motion of DNA, driven by internal forces from nucleoid crowding, dictates LacI movement.
• This dynamic DNA environment may accelerate the protein target search process for transcription factors.