Department of Materials Physics, Nagoya University, Furocho, Chikusa-ku, Nagoya, 464-8603, Japan.
Soft Matter. 2017 Aug 9;13(31):5307-5316. doi: 10.1039/c7sm00239d.
We use a brush of DNA in a solution of transcriptional machinery and histone proteins to theoretically predict that this brush shows phase separation due to the instability arising from the disassembly of nucleosomes during transcription. In the two-phase coexistent state, collapsed chains (with relatively large nucleosome occupancy) lie at the grafting surface and swollen chains (with relatively small nucleosome occupancy) are distributed at the space above the collapsed chains, analogous to the structure of chromatin in differentiated cells. This layer structure is stabilized by the lateral osmotic pressure of swollen chains. For a relatively small grafting density, DNA brushes show tricritical points because the entropic elasticity with respect to the lateral excursion of swollen chains balances with the lateral osmotic pressure of these chains. At the tricritical points, DNA brushes show large fluctuations of local nucleosome concentration, which may be reminiscent of the fluctuations observed in embryonic stem cells.
我们使用 DNA 刷与转录机制和组蛋白蛋白的溶液来理论预测，由于转录过程中核小体的解组装导致的不稳定性，这种刷将发生相分离。在两相共存状态下，塌陷链（具有相对较大的核小体占有率）位于接枝表面，而肿胀链（具有相对较小的核小体占有率）分布在塌陷链上方的空间中，类似于分化细胞中染色质的结构。这种层状结构通过肿胀链的侧向渗透压得到稳定。对于相对较小的接枝密度，DNA 刷表现出三临界点，因为肿胀链的侧向偏移的熵弹性与这些链的侧向渗透压相平衡。在三临界点，DNA 刷表现出局部核小体浓度的大波动，这可能让人联想到在胚胎干细胞中观察到的波动。
