The snRNAs (U1, U2, U4, U5, and the less abundant U11, U12 and U4atac) quickly interact with the SMN (survival of motor neuron protein); encoded by SMN1 gene) and Gemins 2-8 (Gem-associated proteins: GEMIN2, GEMIN3, GEMIN4, GEMIN5, GEMIN6, GEMIN7, GEMIN8) forming the SMN complex.  It is here that the snRNA binds to the SmD1-SmD2-SmF-SmE-SmG pentamer, followed by addition of the SmD3-SmB dimer to complete the Sm ring around the so-called Sm site of the snRNA.  This Sm site is a conserved sequence of nucleotides in these snRNAs, typically AUUUGUGG (where A, U and G represent the nucleosides adenosine, uridine and guanosine, respectively).  After assembly of the Sm ring around the snRNA, the 5 terminal nucleoside (already modified to a 7-methylguanosine cap) is hyper-methylated to 2,2,7-trimethylguanosine and the other (3) end of the snRNA is trimmed.  This modification, and the presence of a complete Sm ring, is recognized by the snurportin 1 protein.