NUCLEOLUS AND ROLLING CIRCLE
NUCLEOLUS AND ROLLING CIRCLE
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DOI：
10.1101/sqb.1974.038.01.058
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发表时间：
1973-01-01
期刊：
影响因子：
--
通讯作者：
WOLFSON, J
中科院分区：
文献类型：
--
作者：
HOURCADE, D;DRESSLER, D;WOLFSON, J
A general feature of the eukaryotic nucleus is the presence of nucleoli. In favorable preparations the nucleoli appear as dense, spherical bodies; they are several times the diameter of a compact chromosome and are located at specific chromosomal sites (McClintock, 1934; Dearing, 1934). The nucleoli can be seen throughout the cell cycle--except for the relatively brief period of mitosis. At this time the nucleoli apparently disperse, and the chromosomal regions which they formerly occupied can be seen only as threadlike constrictions. The determination of the structure and function of the nucleoli has been a task which has extended over many generations of scientists and methodologies. Early investigations began to elucidate a relationship between the nucleolus and the ribosome. Both structures were found to represent the cellular areas in which RNA is concentrated (Brachet, 1940; Casperson and Schultz, 1940; Palade, 1955). A precursor-product relationship between nucleolar RNA and ribosomal RNA arose from the work of MeMaster-Kaye and Taylor (1958) and Woods and Taylor (1958). Their radioautographic experiments traced the flow of tritiated cytidine into RNA and showed that this process begins at the nucleus, predominantly in the nucleolar regions, and ends in the cytoplasm at the ribosomes. The ribosomes were known at this time to be involved in protein synthesis, but their role in the process was not yet well defined. Generally, it was believed that ribosomal RNA consisted of specific informational transcripts derived from the various coding regions of the chromosomes. However, the radioautographic finding that a majority of the rapidly labeled RNA appeared at the nucleolus presented a problem, for it was inconceivable that so much of the informational RNA destined to direct protein synthesis could be produced at a single chromosomal site. Therefore, the idea arose that the nucleolus did not actually code for RNA, but instead was involved in the organization and processing of the many diverse RNA sequences synthesized at other chromosomal regions (see Prescott, 1960).
