The spliceosome is a ribonucleoprotein complex responsible for the removal of introns and the splicing (joining) of exons, one of the postranscriptional modifications experienced by RNA in eukaryotes. It is composed of several RNA molecules (of the small nuclear type, snRNA) associated to several protein molecules.
Here we can see two molecules of one of those components, the U1A protein, bound to a polyribonucleotide (RNA, with 48 nucleotides) corresponding to the 3' end of a messenger RNA precursor (pre-mRNA or hnRNA).
Spacefilling model.
show/hide RNA U1A U1A