Size of the cell nucleus and its effect on the chromatin structure in living cells

DNA-architectural proteins play a major role in organization of chromosomal DNA in living cells by packaging it into chromatin, whose spatial conformation is determined by an intricate interplay between the DNA-binding properties of architectural proteins and physical constraints applied to the DNA by a tight nuclear space. Yet, the exact effects of the cell nucleus size on DNA-protein interactions and chromatin structure currently remain obscure. Furthermore, there is even no clear understanding of molecular mechanisms responsible for the nucleus size regulation in living cells. To find answers to these questions, we developed a general theoretical framework based on a combination of polymer field theory and transfer-matrix calculations, which showed that the nucleus size is mainly determined by the difference between the surface tensions of the nuclear envelope and the endoplasmic reticulum membrane, as well as the osmotic pressure created by cytosolic macromolecules on the cell nucleus. In addition, the model predicted the existence of a previously unknown link between the cell nucleus size and stability of nucleosomes, providing new insights into the potential role of nuclear organization in shaping the cell response to environmental cues. ### Competing Interest Statement The authors have declared no competing interest.