The completed core snRNP-snurportin 1 complex is transported into the nucleus via the protein importin β.  Inside the nucleus, the core snRNPs appear in the Cajal bodies, where final assembly of the snRNPs take place.  This consists of additional proteins and other modifications specific to the particular snRNP (U1, U2, U4, U5).  The biogenesis of the U6 snRNP occurs in the nucleus, although large amounts of free U6 are found in the cytoplasm.  The LSm ring may assemble first, and then associate with the U6 snRNA.