U12 snRNP GO:0005693 A ribonucleoprotein complex that contains small nuclear RNA U12, a heptameric ring of Sm proteins, as well as several proteins that are unique to the U12 snRNP, most of which remain associated with the U12 snRNA both while the U12 snRNP is free or assembled into a series of spliceosomal complexes. cellular_component snRNP U12 spliceosomal snRNP complex