. . . . . . . . . "Binds to the C'/D and B/C motifs in U3 snoRNA. Component of the 25S U4/U6.U5 tri-snRNP particle, a subcomplex of the spliceosome. Binds to the 5'-stem-loop of U4 snRNA. Component of the ribosomal small subunit (SSU) processome composed of at least 40 protein subunits and snoRNA U3." .