GTPases from the MMR1/HSR1 GTP-binding protein subfamily are circularly rearranged G-motifs that play a critical role in maintaining normal cell growth. Deletion of these genes results in severe growth defects with a marked reduction in mature rRNA species and a concomitant accumulation of the 35S pre-rRNA transcript. Deletion also causes the ribosomal protein Rpl25a to fail exportation from the nucleolus. Deletion of any of the G-domain motifs will result in a null phenotype and nuclear/nucleolar localization that lacks the nucleolar export of preribosomes and is accompanied by a distortion of the nucleolar structure. GNL3L (guanine nucleotide binding protein-like 3 (nucleolar)-like) is a 582 amino acid nuclear protein that belongs to the MMR1/HSR1 GTP-binding protein family. Containing one G (guanine nucleotide-binding) domain, GNL3L is required for normal processing of ribosomal pre-rRNA and for cell proliferation.