This is a family of U3 nucleolar RNA-associated proteins which are involved in nucleolar processing of pre-18S ribosomal RNA [1].

1: A large nucleolar U3 ribonucleoprotein required for 18S ribosomal RNA biogenesis. Dragon F, Gallagher JE, Compagnone-Post PA, Mitchell BM, Porwancher KA, Wehner KA, Wormsley S, Settlage RE, Shabanowitz J, Osheim Y, Beyer AL, Hunt DF, Baserga SJ; Nature 2002;0:0-0. PMID:12068309