Functional compartmentalization of the nucleus in the budding yeast Saccharomyces cerevisiae
Functional compartmentalization of the nucleus in the budding yeast Saccharomyces cerevisiae
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DOI：
10.1007/s004120050357
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发表时间：
1999-05-01
期刊：
影响因子：
1.6
通讯作者：
Gas, N
中科院分区：
文献类型：
--
作者：
Léger-Silvestre, I;Trumtel, S;Gas, N
通过结合冷冻固定和冷冻替代对酿酒酵母细胞核进行结构和功能分析，我们确定了核仁中的形态亚室。这些与高级真核生物的核仁类似，如纤维中心（FC）、致密纤维成分（DFC）和颗粒成分（GC）。原位杂交和免疫细胞化学显示，RNA聚合酶I和蛋白质参与了核糖体沿DFC成熟的早期步骤，而核糖体基因则在FCs处检测到。我们的结果还表明，核糖体转录本沿核仁网络分布，可能包括DFC和GC。我们还表明，核糖体前亚基可能沿着轨道输出到细胞质。输出通过核膜的所有孔进行，而不仅仅是那些与核仁接触的孔。此外，对酿酒酵母和pombe Schizosaccharomyces核仁组织的比较表明，5S基因相对于35S转录单元的分布不会改变核仁的组织。我们也首次报道了酵母中RNA聚合酶II的超微结构定位。RNA聚合酶II的分布和在冷冻细胞核仁外区观察到的形态学细节提供了细胞学证据，证明沿核膜延伸的外周区域可能与高等真核生物的异染色质相对应。
By combining cryofixation and cryosubstitution in a structural and functional analysis of the nucleus of Saccharomyces cerevisiae, we identified morphological subcompartments in the nucleolus. These were similar to those of nucleoli of higher eukaryotes, such as the fibrillar centre (FC), the dense fibrillar component (DFC) and the granular component (GC). In situ hybridization and immunocytochemistry revealed RNA polymerase I and proteins involved in early steps of ribosomal maturation along the DFC, while the ribosomal genes were detected at the FCs. Our results also suggest that ribosomal transcripts are distributed along a nucleolar network that might include both DFC and GC. We also show that preribosomal subunits may be exported along tracks to the cytoplasm. Export takes place through all the pores of the nuclear envelope, not just those in contact with the nucleolus. Moreover, comparison of the nucleolar organization in S. cerevisiae and in Schizosaccharomyces pombe demonstrated than the distribution of the 5S genes with respect to the 35S transcription unit does not modify the organization of the nucleolus. We also report, for the first time, the ultrastructural localization of RNA polymerase II in yeast. The distribution of RNA polymerase II and morphological details that could be observed in the extra-nucleolar region of cryofixed cells provided cytological evidence of a peripheral region extending along the nuclear envelope that could correspond to heterochromatin in higher eukaryotes.