A human U2 RNA mutant stalled in 3' end processing is impaired in nuclear import.
AUTOR(ES)
Huang, Q
RESUMO
The biosynthesis of U1, U2, U4 and U5 spliceosomal small nuclear RNAs (snRNAs) involves the nuclear export of precursor molecules extended at their 3' ends, followed by a cytoplasmic phase during which the pre-snRNAs assemble into ribonucleoprotein particles and undergo hypermethylation of their 5' caps and 3' end processing prior to nuclear import. Previous studies have demonstrated that the assembly of pre-snRNAs into ribonucleoprotein particles containing the Sm core proteins is essential for nuclear import in mammalian cells but that 5' cap hypermethylation is not. In the present investigation we have asked whether or not 3' end processing is required for nuclear import of U2 RNA. We designed human pre-U2 RNAs that carried modified 3' tails, and identified one that was stalled (or greatly slowed) in 3' end processing, leading to its accumulation in the cytoplasm of human cells. Nonetheless, this 3' processing arrested pre-U2 RNA molecule was found to undergo cytoplasmic assembly into Sm protein-containing complexes to the same extent as normal pre-U2 RNA. The Sm protein-associated, unprocessed mutant pre-U2 RNA was not observed in the nuclear fraction. Using an assay based on suppression of a genetically blocked SV40 pre-mRNA splicing pathway, we found that the 3' processing deficient U2 RNA was significantly reduced in its ability to rescue splicing, consistent with its impaired nuclear import.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=148282Documentos Relacionados
- U2 small nuclear RNA 3' end formation is directed by a critical internal structure distinct from the processing site.
- Accurate and efficient 3' processing of U2 small nuclear RNA precursor in a fractionated cytoplasmic extract.
- Pseudogenes for human U2 small nuclear RNA do not have a fixed site of 3' truncation.
- Role of the C-Terminal Domain of RNA Polymerase II in U2 snRNA Transcription and 3′ Processing
- Elements required for transcription initiation of the human U2 snRNA gene coincide with elements required for snRNA 3' end formation.