Abstract
Sister chromatid cohesion denotes the phenomenon that sister chromatids are initially attached to each other in mitosis to guarantee the error-free distribution into the daughter cells. Cohesion is mediated by binding proteins and only resolved after mitotic chromosome condensation is completed. However, the amount of attachement points required to maintain sister chromatid cohesion while still allowing proper chromosome condensation is not known yet. Additionally the impact of cohesion on the mechanical properties of chromosomes also poses an interesting problem. In this work we study the conformational and mechanical properties of sister chromatids by means of computer simulations. We model both protein-mediated cohesion between sister chromatids and chromosome condensation with a dynamic binding mechanisms. We show in a phase diagram that only specific link concentrations lead to connected and fully condensed chromatids that do not intermingle with each other nor separate due to entropic forces. Furthermore we show that dynamic bonding between chromatids decrease the Young's modulus compared to non-bonded chromatids.
Highlights
In the interphase, eukaryote chromosomes are replicated and two identical copies of each chromosome, called sister chromatids, are present in the nucleus
To further ensure that sister chromatids are properly distributed to the two daughter cells, they are connected to each other, a phenomenon called sister chromatid cohesion
Cohesion is resolved in anaphase, after chromosome condensation is completed and all chromatid pairs are aligned at the equator of the mitotic spindle [4]
Summary
Eukaryote chromosomes are replicated and two identical copies of each chromosome, called sister chromatids, are present in the nucleus. Without factors that facilitate cohesion, sister chromatids would quickly segregate due to physical properties. The mitotic condensation process involves the formation of cross-links within the chromatin fibers [7] leading to the presence of a large number of loops. This can even further facilitate the segregation process due to the entropic repulsive forces between loops within sister chromatids [8]. The main question that we target in this work is : How does the combination of attachments between two sister chromatids and intra-chromatid cross-links determine the conformational properties of the sister chromatid system?
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