Involved in spliceosome assembly (By similarity). Associates with spliceosomes. Associates with U4/U5/U6 tri-snRNP and with U2 snRNP (By similarity). Detected in nuclear speckles containing snRNP and in Cajal (coiled) bodies. The Tudor domain mediates association with dimethylarginines, which are common in snRNP proteins. Belongs to the SMN family.