RNA in cytoplasmic and nuclear fractions of cellular slime mold amebas.
RNA in cytoplasmic and nuclear fractions of cellular slime mold amebas.
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DOI：
10.1083/jcb.45.2.399
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发表时间：
1970-05
影响因子：
7.8
通讯作者：
Sussman, M
中科院分区：
文献类型：
--
作者：
Cocucci, S M;Sussman, M
描述了一种将细胞粘霉菌（盘基网柄菌）细胞快速分离成核和细胞质部分的方法。在 uridine-3H 存在下长期或短期生长的细胞的放射性蔗糖密度沉降曲线表明，各组分之间的交叉污染水平非常低。核部分含有很少（如果有的话）核糖体。在呈指数增长的细胞中，至少 80% 的核糖体与多核糖体复合物相关。在对数生长的 2 代（24 小时）期间，未观察到预标记 rRNA 的计数损失，并且在多核糖体复合物内，预制材料和在 2 代期间合成的 rRNA 的分布是相同的。在已进入导致子实体构建的发育程序的稳定期细胞中，rRNA 迅速翻转，因此到发育结束时，指数生长期间制造的至少 75% 的核糖体已经消失，并被形态发生序列期间合成的新核糖体所取代。预先形成的核糖体优先从单体中消失；新合成的核糖体仅出现在多核糖体中，并且在至少 6 小时内没有以可观数量出现单体。讨论了这种核糖体大规模替换的可能意义。
A method is described for the rapid separation of cellular slime mold (Dictyostelium discoideum) cells into nuclear and cytoplasmic fractions. Sucrose density sedimentation profiles of radioactivity from cells that had been grown for long or short periods in the presence of uridine-3H indicate very low levels of cross-contamination between the fractions. The nuclear fraction contains few, if any, ribosomes. In exponentially growing cells, at least 80% of the ribosomes were associated in polysomal complexes. No loss of counts from pre-labeled rRNA was observed during 2 generations (24 hr) of logarithmic growth and, within the polysomal complexes, the distributions of the preformed material and of rRNA synthesized during the 2 generations were identical. In stationary phase cells that had entered the developmental program leading to fruiting body construction, the rRNA turned over rapidly so that by the end of development at least 75% of the ribosomes fabricated during exponential growth had disappeared and had been replaced by new ones synthesized during the morphogenetic sequence. The preformed ribosomes disappeared preferentially from the monosomal contingent; the newly synthesized ribosomes appeared exclusively in the polysomal contingent and did not appear as monosomes in appreciable numbers for at least 6 hr. The possible significance of this wholesale replacement of ribosomes is discussed.