According to the current model of pre-mRNA splicing, the five
splicing snRNPs (small nuclear ribonucleoproteins) are thought
to assemble on the pre mRNA, forming a large ribonucleoprotein
complex called a spliceosome (Protein-RNA complex that removes
introns in eukaryotic nuclear RNAs.), named by J. Abelson and E.
Brody. The splicing apparatus in eukaryotic messenger RNAs
consists of several components called small nuclear
ribonucleoproteins (discovered and named by J. Steitz and
colleagues), abbreviated as snRNPs and pronounced “snurps.” Five
of these particles take part in splicing, each composed of one
or more proteins and a small RNA molecule; they are designated
U1, U2, U4, U5, and U6.