Chromatin dynamics is the study of the spatial conformations of chromatin chains. In eukaryotic organisms, the spatial arrangement of chromatin is a key component in the regulation of processes such as gene expression and DNA repair. The SMC complex condensin regulates chromatin chain rigidity by functioning as intramolecular crosslinkers, stochastically binding and releasing to distinct chromatin segments of the same chain. Condensins function at a specific bind-and-release (BAR) rate, which is influenced by cell cycle regulators and other nuclear proteins. The exact BAR rate and its effects on the motion of chromatin, however, are unknown. To answer that question, I am using computational models of the S. cerevisiae nucleus to observe the motion of chromatin chains of varying length in the event of a double-stranded break and with varying condensin BAR rates, then quantify the motion using mean-square displacement analysis (MSD). I show that, while different BAR rates constrain the motion of short chains only, there is at least one BAR rate at which both short and long chromatin chains behave most similarly to in-vivo yeast models described in literature. This behavior results from the additional clustering forces created by condensins, which increase chromatin chain rigidity to a varying extent depending on BAR rate. These findings help increase our understanding of the biological mechanisms regulating chromatin dynamics, while also presenting a versatile computational model that can aid in future research.
Andrew Atanasiu (Sat,) studied this question.