Chambers S A, Cognetti G, Shaw B R
Exp Cell Res. 1984 Sep;154(1):213-23. doi: 10.1016/0014-4827(84)90681-5.
We have examined the kinetics of nuclease digestion of chromatin from committed and uncommitted cells in experiments where the nuclei are mixed and co-digested. Cultures of the sea urchin, Arbacia punctulata, were grown to the 16-cell stage in either [3H]thymidine or [14C]thymidine and the macromere, mesomere, and micromere cell types separated. After isolation, sets of nuclei with two different blastomere types (each having different radionucleotide tagging) were mixed and co-digested with micrococcal nuclease or DNase. I. The extent of digestion was monitored by solubility in 5% perchloric acid (PCA). We find no significant differences in initial digestion rates or limit digests among the different cell types when co-digested with either nuclease. Differences in nuclease sensitivity observed when nuclei are digested separately are abolished when nuclei are probed in a mixing experiment. The results support the hypothesis that phenotypic differences in digestibility among different cell types in vitro reflect differences in chromatin-condensing factors which can diffuse between nuclei.
在细胞核混合并共同消化的实验中，我们研究了已分化细胞和未分化细胞的染色质核酸酶消化动力学。将海胆（Arbacia punctulata）培养至16细胞期，分别用[³H]胸腺嘧啶核苷或[¹⁴C]胸腺嘧啶核苷标记，然后分离出大分裂球、中分裂球和小分裂球细胞类型。分离后，将两组具有不同卵裂球类型（每种类型都有不同的放射性核苷酸标记）的细胞核混合，并用微球菌核酸酶或DNA酶I共同消化。通过在5%高氯酸（PCA）中的溶解度监测消化程度。当与任何一种核酸酶共同消化时，我们发现不同细胞类型之间的初始消化速率或极限消化没有显著差异。在混合实验中检测细胞核时，单独消化细胞核时观察到的核酸酶敏感性差异消失了。结果支持这样的假设，即体外不同细胞类型之间消化率的表型差异反映了可在细胞核之间扩散的染色质凝聚因子的差异。
