Plays a role in pre-mRNA splicing as a core component of the spliceosomal U1, U2, U4 and U5 small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome (    , ). Component of both the pre-catalytic spliceosome B complex and activated spliceosome C complexes (  ). As a component of the minor spliceosome, involved in the splicing of U12-type introns in pre-mRNAs . May act as a charged protein scaffold to promote snRNP assembly or strengthen snRNP-snRNP interactions through non-specific electrostatic contacts with RNA .
Subcellular locations: Cytoplasm, Cytosol, Nucleus
SMN-mediated assembly into core snRNPs occurs in the cytosol before SMN-mediated transport to the nucleus to be included in spliceosomes.