Genome packing and fractal globules: some new developments
Mikhail Tamm (Physics department, Moscow State University)
The idea that genome packing in a cell nucleus is to a large extent governed by topological constraints has been around for many years: the corresponding topologically controlled state, known as a fractal globule, was first predicted in the late 1980s. Recently with the development of the new experimental techniques, especially the so-called Hi-C contact maps, a lot of new evidence appeared concerning the statistics of the genome spatial structure. This new data seems to support the fractal globule model, and therefore it caused a significant renewed interest in the physics of the fractal globule state in the recent years. In my talk, I will overview the ideas behind the fractal globule model and the current state of art in the theory of genome packing. After that, I will discuss two more narrow questions we have been trying to develop recently. In particular, first, I will talk about the fine structure of the Hi-C contact maps and possible ways to explain it by combining the hierarchical folding intrinsic to the fractal globule idea and the assumption about quenched block-copolymer structure of the genome. Second, I will discuss the dynamic of self-diffusion in the fractal globule and develop a scaling theory predicting it to be a subdiffusion with a scaling index 0.4. I will also discuss the implications of this result for the search processes in the fractal globule.