Format

Send to

Choose Destination
Curr Biol. 1999 Oct 7;9(19):1065-74.

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

Author information

1
Department of Biochemistry University of Dundee Wellcome Trust Building, Dow Street, Dundee, DD1 5EH, UK.

Abstract

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.

PMID:
10531003
[Indexed for MEDLINE]
Free full text

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center