Stabilizes TERF1 telomeric association by preventing TERF1 recruitment by PML. Stabilizes TERF1 protein by preventing its ubiquitination and hence proteasomal degradation. Does so by interfering with TERF1-binding to FBXO4 E3 ubiquitin-protein ligase. Required for cell proliferation. By stabilizing TRF1 protein during mitosis, promotes metaphase-to-anaphase transition. Stabilizes MDM2 protein by preventing its ubiquitination, and hence proteasomal degradation. By acting on MDM2, may affect TP53 activity. Required for normal processing of ribosomal pre-rRNA. Binds GTP (By similarity). Interacts with MDM2; this interaction, which occurs in the nucleoplasm, stabilizes MDM2. Indirectly interacts with TP53, via MDM2-binding. Interacts with TERF1; this interaction probably occurs in the nucleoplasm and is increased during mitosis, when the nucleolus is disassembled. This binding may promote TERF1 homodimerization. Interacts with TERT. In contrast to other GTP-binding proteins, this family is characterized by a circular permutation of the GTPase motifs described by a G4-G1-G3 pattern. Belongs to the TRAFAC class YlqF/YawG GTPase family.