Zatsepina O V, Poliakov V Iu, Chentsov Iu S
Tsitologiia. 1985 Aug;27(8):865-71.
The ultrastructure of G- and R-bands in differentially decondensed chromosomes of Chinese hamster was studied with a gradual decrease in CaCl2 concentration in the medium. The gradual reduction of CaCl2 concentration leads to the decondensation of compact G-bands into chromonemes, chromomeres and further into DNP-fibrils. In the complete local decondensation zones (R-bands), the DNP-fibril orientation is parallel to the chromosome longitudinal axis. These zones have no lateral loops or chromomeres. Thus, different chromosome regions corresponding to G- and R-bands possess different sensibility to the decondensing action. Following the complete decondensation in the calcium-free medium chromosomes can be "reconstructed" by adding Ca2+. The data obtained permit to suggest a "fastener" model of the mitotic chromosome organization in which the chromosome represents an hierarchy of discrete structures--G-bands, chromomeres, nucleomeres (superbeads) and nucleosomes. The structural integrity of these levels is supported by specific protein "fasteners".
采用逐步降低培养基中氯化钙浓度的方法，研究了中国仓鼠差异解聚染色体中G带和R带的超微结构。氯化钙浓度的逐步降低导致紧密的G带解聚为染色线、染色粒，进而解聚为脱氧核蛋白纤维。在完全局部解聚区（R带），脱氧核蛋白纤维的方向与染色体纵轴平行。这些区域没有侧环或染色粒。因此，对应于G带和R带的不同染色体区域对解聚作用具有不同的敏感性。在无钙培养基中完全解聚后，通过添加Ca2+可以“重建”染色体。所获得的数据提示有丝分裂染色体组织的“紧固件”模型，其中染色体代表离散结构的层次体系——G带、染色粒、核粒（超珠）和核小体。这些层次的结构完整性由特定的蛋白质“紧固件”支持。
