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). {ECO:0000269|PubMed:20647540, ECO:0000269|PubMed:22083961, ECO:0000269|PubMed:22872859}. This is the function of LAS1L (LAS1 like ribosome biogenesis factor, Ensembl gene identifier ENSG00000001497).