Puvion-Dutilleul F, Mazan S, Nicoloso M, Christensen M E, Bachellerie J P
Laboratoire de Biologie et Ultrastructure du Noyau, CNRS (UPR 272), Villejuif/France.
Eur J Cell Biol. 1991 Dec;56(2):178-86.
We have examined the ultrastructural localization of U3 RNA in the nucleoli of HeLa and mouse 3T3 cells by in situ hybridization with a biotinylated U3 DNA probe and subsequent detection of hybrids with electron microscopy by direct immunogold labeling. The highest levels of signal density for U3 RNA are detected over the dense fibrillar component (DFC) of the nucleolus, including the interfaces between DFC and the enclosed fibrillar center (FC) on the one hand and DFC and the granular component (GC) on the other hand. Lower but significant signals also are observed over GC, which indicate, taking into account the high relative volume of GC in a nucleolus, that a substantial fraction of U3 RNA is present in this compartment where the more mature forms of pre-rRNA accumulate. In parallel, the localization of fibrillarin was analyzed by immunogold detection, demonstrating that fibrillarin and U3 RNA have a roughly similar distribution, although quantitative measurements reveal that the signal ratio for both molecules exhibit significant differences among the major ultrastructural components of the nucleolus.
我们通过用生物素化的U3 DNA探针进行原位杂交，并随后通过直接免疫金标记在电子显微镜下检测杂交体，研究了U3 RNA在HeLa细胞和小鼠3T3细胞细胞核仁中的超微结构定位。在核仁的致密纤维成分（DFC）上检测到U3 RNA的最高信号密度水平，包括DFC与封闭的纤维中心（FC）之间的界面以及DFC与颗粒成分（GC）之间的界面。在GC上也观察到较低但显著的信号，考虑到GC在核仁中的相对体积较大，这表明相当一部分U3 RNA存在于该隔室中，前体rRNA的更成熟形式在此积累。同时，通过免疫金检测分析了纤维蛋白原的定位，表明纤维蛋白原和U3 RNA具有大致相似的分布，尽管定量测量显示这两种分子的信号比在核仁的主要超微结构成分之间存在显著差异。
