Mangenot S, Leforestier A, Durand D, Livolant F
Laboratoire de Physique des Solides, CNRS UMR 8502, Bât 510, Université Paris-Sud, 91405 Orsay Cedex, France.
J Mol Biol. 2003 Nov 7;333(5):907-16. doi: 10.1016/j.jmb.2003.09.015.
We present a phase diagram of the nucleosome core particle (NCP) as a function of the monovalent salt concentration and applied osmotic pressure. Above a critical pressure, NCPs stack on top of each other to form columns that further organize into multiple columnar phases. An isotropic (and in some cases a nematic) phase of columns is observed in the moderate pressure range. Under higher pressure conditions, a lamello-columnar phase and an inverse hexagonal phase form under low salt conditions, whereas a 2D hexagonal phase or a 3D orthorhombic phase is found at higher salt concentration. For intermediate salt concentrations, microphase separation occurs. The richness of the phase diagram originates from the heterogeneous distribution of charges at the surface of the NCP, which makes the particles extremely sensitive to small ionic variations of their environment, with consequences on their interactions and supramolecular organization. We discuss how the polymorphism of NCP supramolecular organization may be involved in chromatin changes in the cellular context.
我们展示了核小体核心颗粒（NCP）的相图，该相图是单价盐浓度和外加渗透压的函数。在临界压力以上，NCP相互堆叠形成柱体，这些柱体进一步组织成多个柱状相。在中等压力范围内观察到柱体的各向同性（在某些情况下为向列相）相。在更高的压力条件下，低盐条件下形成层状柱状相和反六边形相，而在高盐浓度下发现二维六边形相或三维正交相。对于中等盐浓度，会发生微相分离。相图的丰富性源于NCP表面电荷的不均匀分布，这使得颗粒对其环境中的小离子变化极其敏感，从而影响它们的相互作用和超分子组织。我们讨论了NCP超分子组织的多态性如何可能参与细胞环境中的染色质变化。
