Biophysical Society Thematic Meeting| Les Houches 2019

Multiscale Modeling of Chromatin: Bridging Experiment with Theory

Poster Abstracts

24 - POS Board 24 THE BP-SCALE THERMAL DIFFUSION OF NUCLEOSOMES MODULATES BINDING OF TRANSCRIPTION FACTORS Sergei Rudnizky 1 ; Hadeel Khamis 2,3 ; Omri Malik 2,3 ; Philippa Melamed 1,3 ; Ariel Kaplan 1,2,3 ; 1 Technion - Israel Institute of Technology, Biology, Haifa, North, Israel 2 Technion – Israel Institute of Technology, Physics, Haifa, North, Israel 3 Technion – Israel Institute of Technology, Russell Berrie Nanotechnology Institute, Haifa, North, Israel The structure of promoter chromatin determines the ability of transcription factors to bind the DNA and therefore has a profound effect on the expression levels of genes. Yet, the role of spontaneous nucleosome movements in this process is not fully understood. Here, we developed a single-molecule assay capable of simultaneously characterizing the bp-scale diffusion of a nucleosome on DNA, and the binding of a transcription factor (TF). Our results demonstrate that nucleosomes undergo confined diffusion, and that the incorporation of the histone variant H2A.Z serves to partially relieve this confinement, inducing a different type of nucleosome repositioning. The increase in diffusion leads to exposure of a TF’s binding site and facilitates its association with the DNA, which in term biases the subsequent movement of the nucleosome. Our findings suggest the use of mobile nucleosomes as a novel and general transcriptional regulatory mechanism.

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