Fluidification of entanglements by a DNA bending protein

TL;DR

This study reveals that the DNA-bending protein IHF significantly reduces the viscosity of entangled DNA, acting as a 'genomic fluidiser' and potentially regulating DNA dynamics within the cell.

Contribution

It demonstrates, through combined microrheology and simulations, that IHF lowers DNA entanglement viscosity, a novel insight into its role in genome organization.

Findings

IHF reduces DNA solution viscosity 20-fold at physiological levels.

IHF may decrease nucleoid viscosity by approximately 200-fold.

IHF acts as a 'genomic fluidiser' influencing DNA reorganization.

Abstract

In spite of the nanoscale and single-molecule insights into how nucleoid associated proteins (NAPs) interact with DNA, their role in modulating the mesoscale viscoelasticity of the entangled genome in vivo has been overlooked so far. By combining microrheology and molecular dynamics simulation we find that the important NAP called Integration Host Factor (IHF) lowers the viscosity of entangled $\lambda$DNA 20-fold at physiological concentrations and stoichiometries. We argue that IHF may act as a "genomic fluidiser", reducing the effective viscosity of the nucleoid $\sim$200-fold. Our results suggest a previously unappreciated key role of IHF in regulating DNA dynamics and re-organisation in vivo