The Sm proteins are components of the U1, U2, U4/U6 and U5 small ribonucleoproteins (snRNPs). As many as 10 or more proteins may be assembled into these complexes. Some of the Sm proteins are shared between snRNPs while others are specific to particular snRNPs. Among the core ribonucleoproteins are 3 distinct subunits designated D1, D2, and D3.

Small nuclear ribonucleoprotein Sm D2 is a protein belongs to the small nuclear ribonucleoprotein core protein family. It is required for pre-mRNA splicing and small nuclear ribonucleoprotein biogenesis. Alternative splicing occurs at this locus and two transcript variants encoding the same protein have been identified.