In vivo, U2 snRNA along with its associated polypeptides assemble to produce the U2 small nuclear ribonucleoprotein (snRNP), an essential component of the major spliceosomal complex.

[1] The major spliceosomal-splicing pathway is occasionally referred to as U2 dependent, based on a class of Sm intron—found in mRNA primary transcripts—that are recognized exclusively by the U2 snRNP during early stages of spliceosomal assembly.

[11] These non-specific structural proteins associate with Sm snRNAs through a highly conserved recognition sequence (AUnG,n = 4-6) located within the RNA called Sm-binding sites.

[16] Moreover, several secondary structural elements are also conserved including stem loops I, II, III, IV, and some of the single stranded regions linking these domains.

Although many of the biochemical details surrounding spliceosomal rearrangements remains unclear, recent studies have visualized the formation of a critical folding complex between U2 and U6 snRNAs immediately proceeding the first step of the splicing reaction.

[19] Finally, it is likely the spliceosome utilizes the same two-metal ion mechanism as group II introns given the structural conservation of metal binding sites found within the U2-U6 fold.