NOP53 is a multifunctional nucleolar protein essential for ribosome biogenesis and cellular stress response. Primarily, NOP53 integrates the 5S ribosomal ribonucleoprotein (RNP) into the large ribosomal subunit and participates in 5.8S rRNA maturation through interaction with the MTR4 helicase-exosome complex via its arch-interacting motif 12. Beyond ribosome assembly, NOP53 functions as a nucleolar stress sensor: upon DNA damage or ribosome biogenesis perturbation, disrupted NOP53-RPL11 interaction permits RPL11 nuclear translocation, which inhibits MDM2 and activates p53/TP53 1. NOP53 also stabilizes p53 through direct interaction, preventing MDM2-mediated degradation 3. Additional tumor-suppressive functions include positive regulation of PTEN stability, antagonizing PI3K-AKT signaling, and suppression of autophagy through ZKSCAN3-dependent and -independent pathways 45. Clinically, NOP53 dysregulation associates with cancer development: downregulation causes chr19 instability and abnormal nuclear morphology in cervical cancer cells 6, while germline variants may increase familial non-medullary thyroid cancer susceptibility 7. Conversely, viruses exploit cytoplasmic NOP53 translocation to suppress interferon-beta production and enhance replication 89.