Newly assembled snRNPs associate with coiled bodies before speckles, suggesting a nuclear snRNP maturation pathway

被引:210
作者
Sleeman, JE [1 ]
Lamond, AI [1 ]
机构
[1] Univ Dundee, Dept Biochem, Dundee DD1 5EH, Scotland
基金
英国惠康基金;
关键词
D O I
10.1016/S0960-9822(99)80475-8
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Background: Small nuclear ribonucleoproteins (snRNPs), which are essential components of the mRNA splicing machinery, comprise small nuclear RNAs, each complexed with a set of proteins. An early event in the maturation of snRNPs is the binding of the core proteins - the Sm proteins - to snRNAs in the cytoplasm followed by nuclear import. Immunolabelling with antibodies against Sm proteins shows that splicing snRNPs have a complex steady-state localisation within the nucleus, the result of the association of snRNPs with several distinct subnuclear structures. These include speckles, coiled bodies and nucleoli, in addition to a diffuse nucleoplasmic compartment. The reasons for snRNP accumulation in these different structures are unclear. Results: When mammalian cells were microinjected with plasmids encoding the Sm proteins B, D1 and E, each tagged with either the green fluorescent protein (GFP) or yellow-shifted GFP (YFP), a pulse of expression of the tagged proteins was observed. In each case, the newly synthesised GFP/YFP-labelled snRNPs accumulated first in coiled bodies and nucleoli, and later in nuclear speckles. Mature snRNPs localised immediately to speckles upon entering the nucleus after cell division. Conclusions: The complex nuclear localisation of splicing snRNPs results, at least in part, from a specific pathway for newly assembled snRNPs. The data demonstrate that the distribution of snRNPs between coiled bodies and speckles is directed and not random.
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页码:1065 / 1074
页数:10
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