Wigler M H, Axel R
Nucleic Acids Res. 1976 Jun;3(6):1463-71. doi: 10.1093/nar/3.6.1463.
Previous studies of the structure of metaphase chromosomes have relied heavily on electron micrography and have revealed the existence of a 10-nm unit fiber that is thought to generate the native 23-30-nm fiber by higher order folding. The structural relationship of these metaphase fibers to the interphase fiber remains obscure. Recent studies on the digestion of interphase chromatin have revealed the existence of a regularly repeating subunit of DNA and histone, the nucleosome that generates the appearance of 10-nm beads connected by a short fiber of DNA seen on electron micrographs. It was therefore of interest to probe the structure of the metaphase chromosome for the presence of nucleosomal subunits. To this end metaphase chromosomes were prepared from colchicine-arrested cultures of mouse L-cells and were subjected to digestion with stayphylococcal nuclease. Comparison of the early and limit digestion products of metaphase chromosomes with those obtained from interphase nuclei indicates that although significant morphologic changes occur within the chromatin fiber during mitosis, the basic subunit structure of the chromatin fiber is retained by the mitotic chromosome.
以往对中期染色体结构的研究严重依赖电子显微镜，并揭示了一种10纳米单位纤维的存在，人们认为这种纤维通过更高层次的折叠产生天然的23 - 30纳米纤维。这些中期纤维与间期纤维的结构关系仍不清楚。最近对间期染色质消化的研究揭示了DNA和组蛋白的一种规则重复亚基——核小体的存在，在电子显微镜下可以看到核小体产生由短DNA纤维连接的10纳米珠子的外观。因此，探究中期染色体结构中是否存在核小体亚基是很有意义的。为此，从秋水仙素阻滞的小鼠L细胞培养物中制备中期染色体，并用葡萄球菌核酸酶进行消化。将中期染色体的早期和极限消化产物与间期核获得的产物进行比较，结果表明，尽管在有丝分裂过程中染色质纤维内发生了显著的形态变化，但染色质纤维的基本亚基结构在有丝分裂染色体中得以保留。
