title: Phase Behavior of DNA in the Presence of DNA-Binding Proteins.
abstract: To characterize the thermodynamical equilibrium of DNA chains interacting with a solution of nonspecific binding proteins, we implemented a Flory-Huggins free energy model. We explored the dependence on DNA and protein concentrations of the DNA collapse. For physiologically relevant values of the DNA-protein affinity, this collapse gives rise to a biphasic regime with a dense and a dilute phase; the corresponding phase diagram was computed. Using an approach based on Hamiltonian paths, we show that the dense phase has either a molten globule or a crystalline structure, depending on the DNA bending rigidity, which is influenced by the ionic strength. These results are valid at the thermodynamical equilibrium and therefore should be consistent with many biological processes, whose characteristic timescales range typically from 1 ms to 10 s. Our model may thus be applied to biological phenomena that involve DNA-binding proteins, such as DNA condensation with crystalline order, which occurs in some bacteria to protect their chromosome from detrimental factors; or transcription initiation, which occurs in clusters called transcription factories that are reminiscent of the dense phase characterized in this study.
authors.affiliation: Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, Gif-sur-Yvette, France; Institute of Systems and Synthetic Biology, University of Evry-Val-d'Essonne, CNRS, Genopole Campus 1, Evry, France. Electronic address: guillaume.le-treut@cea.fr.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Le Treut
authors.affiliation: Institute of Systems and Synthetic Biology, University of Evry-Val-d'Essonne, CNRS, Genopole Campus 1, Evry, France.
authors.forename: François
authors.initials: F
authors.lastname: Képès
authors.affiliation: Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, Gif-sur-Yvette, France.
authors.forename: Henri
authors.initials: H
authors.lastname: Orland
mesh_terms: D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019277:Entropy; D056004:Molecular Dynamics Simulation; D009690:Nucleic Acid Conformation
chemical_list: D004268:DNA-Binding Proteins; D004247:DNA