May be required to maintain the proliferative capacity of stem cells. Stabilizes MDM2 by preventing its ubiquitination, and hence proteasomal degradation (By similarity). {ECO:0000250, ECO:0000269|PubMed:12464630, ECO:0000269|PubMed:16012751}. This is the function of GNL3 (G protein nucleolar 3, Ensembl gene identifier ENSG00000163938).