四膜虫(Tetrahymena shanghaiensis)大核核仁与去膜大核能诱导非细胞体系核重建  

CELL-FREE NUCLEAR ASSEMBLY INDUCED BY NUC- LEOLI AND DEMEMBRANATED MACRONUCLEI FROM TETRAHYMENA SHANGHAIENSIS

作　　者：陈英[1] 张博[1] 罗文捷[1] 翟中和[1] 

机构地区：[1]北京大学生命科学学院,北京100871

出　　处：《实验生物学报》1996年第3期255-267,共13页Acta Biologiae Experimentalis Sinica

基　　金：国家自然科学基金

摘　　要：外源DNA或染色质在非洲爪蟾卵提取物中可以诱导细胞核样结构的重建。重建核除不具有核仁样结构外,在其它形态结构上与真核细胞核十分相似。前人的工作表明在重建核中具有核仁前体结构。但可能是由于缺少活性核仁组织者的缘故,这些核仁前体不能相互融合形成新生核仁。那么活性核仁组织者在重建核中是否能发挥其功能呢?为了研究这一问题,我们提取纯化了四膜虫的大核与大核的周边核仁。进一步去除大核的核被膜,并将去除核被膜的大核与大核核仁分别加入非洲爪赡卵非细胞体系中。通过电镜超薄切片观察,我们发现无论是与大核染色质相连的周边核仁还是分离纯化的核仁结构在非洲爪赡卵非细胞体系中都不能保持其原有结构特征,而是发生了典型核重建变化,并且在诱导形成的重建核中也看不到核仁样结构。这些结果说明具有活性的核仁组织者在加入非洲爪蟾卵提取物后既不能继续保持其原有的RNA转录功能也不能诱导新的核仁的出现。Nuclei assembled in Xenopus egg extracts from exogenous DNA or chromatin are morphologically similar to normal eukaryotic nuclei except that they do not contain nucleolus- like structure. Previous work show that prenucleolar bodies could be found in these nuclei, but they are unable to fuse with each other, probably due to the absence of a functional nucleolus organizer. It is interesting to know if exogenous functional nuclei could act as functional nucleolus organizer to induce the formation of mature nucleoli. To test this possibility, nucleoli and demembrana-ted macronuclei which contain perinuclear distributed nucleoli were isolated and pu-rified from Tetrahymena shanghaiensis and were introduced into Xenopus cell-free system. By EM observation, we showed that these nucleoli, both individual isolated and perinuclear distributed, could not keep their original morphological characteristic, but undergo a series of structural changes remembling nuclear assembly induced by exogenous chromatin. No nucleo-lus-like structure was found in these nuclear like structure. These results indicate that functional nucleolus organizers could neither keep their original activity of RNA transcription nor induce the formation of new nucleoli in Xenopus egg extracts.

关 键 词：四膜虫 大核 核仁重建 非细胞体系 

分 类 号：Q959.117.3[生物学—动物学]