Armstrong S W, Davidson D
Can J Biochem. 1982 Mar;60(3):371-8. doi: 10.1139/o82-044.
DNA and protein contents of pairs of sister nuclei were determined using a combined Feulgen-dinitrofluorobenzene technique. Sister nuclei were studied in binucleate cells, induced by treatment with 0.1% caffeine, and in sister mononucleate cells of untreated roots. Excised pea roots, grown in culture, were treated with 5-aminouracil to induce mitotic synchrony and with caffeine at the time of peak mitotic index, to provide the maximum number of binucleate cells. The induced binucleate cells form a marked population which was followed through a cell cycle; sister nuclei showed a correlation of volume and protein content, r = 0.79. Protein contents of sister nuclei were rarely identical and at 1 + 2 and 1 + 6 h the difference in protein contents of sister nuclei was significant (p = 0.05). Mean nuclear protein content decreased from 1 + 2 to 1 + 6 h; then, as nuclei entered S phase, their protein content increased. From 1 + 2 to 1 + 14 h the increase in protein content, in absolute amount, was identical in both sister nuclei. This suggests that there was a biphasic pattern of protein uptake; it is differential, in sister nuclei, in the first part of G1 but is identical throughout the rest of interphase. Analysis of sister nuclei from sister mononucleate cells showed a similar pattern of change; this is further evidence, from untreated cells, of a biophasic pattern of protein uptake. Caffeine-treated nuclei had lower protein contents than untreated nuclei, yet they completed a cell cycle and entered mitosis; this suggests that nonessential proteins were no longer present. It is proposed that mitosis is asymmetrical for molecules that regulate rates of macromolecular synthesis, cell growth, and progress through a cell cycle and that once the initial asymmetry has been established, it is maintained throughout interphase, even in binucleate cells in which the two nuclei share a common cytoplasm.
采用Feulgen-二硝基氟苯联合技术测定姐妹细胞核对的DNA和蛋白质含量。在经0.1%咖啡因处理诱导产生的双核细胞以及未处理根的姐妹单核细胞中研究姐妹细胞核。将培养生长的豌豆根切除后，用5-氨基尿嘧啶处理以诱导有丝分裂同步化，并在有丝分裂指数峰值时用咖啡因处理，以获得最大数量的双核细胞。诱导产生的双核细胞形成一个明显的群体，对其进行一个细胞周期的跟踪研究；姐妹细胞核的体积与蛋白质含量呈现相关性，r = 0.79。姐妹细胞核的蛋白质含量很少完全相同，在1 + 2小时和1 + 6小时时，姐妹细胞核蛋白质含量的差异具有显著性（p = 0.05）。平均核蛋白含量从1 + 2小时到1 + 6小时下降；然后，随着细胞核进入S期，其蛋白质含量增加。从1 + 2小时到1 + 14小时，两个姐妹细胞核中蛋白质含量的绝对增加量相同。这表明蛋白质摄取存在双相模式；在G1期的第一部分，姐妹细胞核中的摄取是有差异的，但在整个间期的其余时间是相同的。对姐妹单核细胞中的姐妹细胞核进行分析，显示出类似的变化模式；这从未经处理的细胞中进一步证明了蛋白质摄取的双相模式。经咖啡因处理的细胞核蛋白质含量低于未处理的细胞核，但它们完成了一个细胞周期并进入有丝分裂；这表明非必需蛋白质不再存在。有人提出，对于调节大分子合成速率、细胞生长以及细胞周期进程的分子来说，有丝分裂是不对称的，并且一旦建立了初始的不对称性，它在整个间期都会保持，即使在两个细胞核共享共同细胞质体的双核细胞中也是如此。
