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). Component of the PELP1 complex involved in the nucleolar steps of 28S rRNA maturation and the subsequent nucleoplasmic transit of the pre-60S ribosomal subunit (PubMed:21326211). May play a role during development (By similarity). {ECO:0000250|UniProtKB:Q68EI0, ECO:0000269|PubMed:21326211, ECO:0000269|PubMed:22872859}. This is the function of WDR18 (WD repeat domain 18, Ensembl gene identifier ENSG00000065268).