Are snRNPs involved in splicing?

@article{Lerner1980AreSI,
  title={Are snRNPs involved in splicing?},
  author={Michael R. Lerner and John T. A. Boyle and Stephen M. Mount and Sandra L. Wolin and Joan A. Steitz},
  journal={Nature},
  year={1980},
  volume={283},
  pages={220-224}
}
Discrete, stable small RNA molecules are found in the nuclei of cells1 from a wide variety of eukaryotic organisms2. Many of these small nuclear RNA (snRNA) species, which range in size from about 90 to 220 nucleotides, have been well-characterised biochemically3–6, and some sequenced7,8. However, their function has remained obscure. The most abundant snRNA species exist as a closely related set of RNA–protein complexes called small nuclear ribonucleoproteins (snRNPs)9. snRNPs are the antigens… 
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Saccharomyces cerevisiae has a U1-like small nuclear RNA with unexpected properties.
TLDR
Several regions of significant homology to U1 have now been found in cloned and sequenced snR19, and ten out of ten matches to the 5' end of U1, the site known to interact with the5' splice site of mammalian introns, are found.
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TLDR
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Small nuclear ribonucleoproteins (snRNPs) are protein–ribonucleic acid (RNA) complexes defined by a core noncoding RNA of approximately 100–600 nucleotides and tightly bound proteins that together
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TLDR
In contrast to procaryotes, eucaryotic cells contain a discrete set of low molecular weight RNA species with a size distribution between 4 S and 7 S and two recent reports point to a possible involvement of small nuclear RNA species in hnRNA metabolism.
Small Nuclear RNAs: RNA Sequences, Structure, and Modifications
TLDR
All eukaryotic cells contain multiple small nuclear RNAs, designated U- SnRNAs, which account for about 1% total mammalian cellular RNA; of these, the U1 to U8 snRNAs have been sively characterized.
Small RNAs in HnRNP fibrils and their possible function in splicing
TLDR
The possibility that U1A RNA might serve for the alignment of the extremities of the intron sequences of premessenger RNA insuring correct condition for cutting and splicing was reexamined and found that only a UCCA sequence at position 8–11 of U 1A RNA was complementary to an AG-GU around a putative splice point for 69 different introns sequenced so far.
Intracellular site of U1 small nuclear RNA processing and ribonucleoprotein assembly
TLDR
The results suggest that the cytoplasm is a site of significant U1 RNA processing and RNP assembly, which raises the possibility that nuclear-transcribed eucaryotic RNAs are always processed in the cell compartment other than that in which they ultimately function, which suggests a set of precise signals regulating RNA and ribonucleoprotein traffic between nucleus and cy toplasm.
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References

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Antibodies to small nuclear RNAs complexed with proteins are produced by patients with systemic lupus erythematosus.
  • M. Lerner, J. Steitz
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1979
TLDR
It is argued that each of the six snRNAs exists in a separate small nuclear ribonucleoprotein (snRNP) complex with a total molecular weight of about 175,000.
In vitro RNA-RNA splicing in adenovirus 2 mRNA formation.
TLDR
"Splicing" of the precursor to an adenovirus mRNA was accomplished in isolated cell-free extracts using a poly(A)-terminated RNA molecule identical in size to the cytoplasmic 72,000 Mr protein mRNA in which the sequences encoded in the 70.7--75.7 region of the viral genome were spliced.
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A number of genes in higher organisms and in their viruses appear to be split. That is, they have "nonsense" stretches of DNA interspersed within the sense DNA. The cell produces a full RNA
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