Required for the synthesis of the 60S ribosomal subunit and maturation of the 28S rRNA (PubMed:20647540). Functions as a component of the Five Friends of Methylated CHTOP (5FMC) complex; the 5FMC complex is recruited to ZNF148 by methylated CHTOP, leading to desumoylation of ZNF148 and subsequent transactivation of ZNF148 target genes (PubMed:22872859). Required for the efficient pre-rRNA processing at both ends of internal transcribed spacer 2 (ITS2) (PubMed:22083961).