Elsevier established a free COVID-19 resource center in January 2020, offering English and Mandarin information on the virus. The center is hosted on Elsevier Connect, and the company grants permission for free access to its research in PubMed Central and other repositories for unrestricted use. The nucleolus is a key organelle involved in stress responses, particularly in regulating p53. Under stress, the nucleolus undergoes structural and compositional changes, including reorganization of its three main compartments: fibrillar center (FC), dense fibrillar component (DFC), and granular component (GC). Stress can lead to nucleolar segregation, fragmentation, or changes in nucleolar size and shape, affecting ribosome subunit production and cell growth. Stress responses involve complex signaling pathways that regulate ribosome subunit biogenesis, including the mTOR pathway, which controls RNA polymerase I activity and ribosomal protein (RP) translation. Stress can also influence the nucleolar proteome, with changes in protein localization and function affecting nucleolar integrity and function. The nucleolus plays a central role in the stress response by coordinating the activation of p53, which is crucial for cell-cycle arrest and apoptosis. p53 stability is regulated by interactions with proteins such as Hdm2, and stress can alter these interactions through mechanisms like p14ARF upregulation, RPL11 de-NEDDylation, and changes in protein-protein interactions. The nucleolus and Cajal bodies (CBs) are closely linked in stress responses. CBs are involved in RNA processing and are affected by stress, with changes in coilin localization and CB structure. Stress can lead to CB disruption, which may be linked to snRNP biogenesis and cell-cycle progression. The nucleolus and CBs are involved in various cellular functions beyond ribosome biogenesis, including DNA repair, viral infection, and cell-cycle control. Stress-induced changes in these organelles are regulated by posttranslational modifications (PTMs) and signaling pathways, highlighting the nucleolus's role as a central hub in the stress response. Understanding the molecular mechanisms underlying nucleolar and CB responses to stress is essential for elucidating the cellular stress response and its implications in diseases such as cancer and neurodegenerative disorders. Further research into these mechanisms may provide insights into the development of therapeutic strategies for these conditions.Elsevier established a free COVID-19 resource center in January 2020, offering English and Mandarin information on the virus. The center is hosted on Elsevier Connect, and the company grants permission for free access to its research in PubMed Central and other repositories for unrestricted use. The nucleolus is a key organelle involved in stress responses, particularly in regulating p53. Under stress, the nucleolus undergoes structural and compositional changes, including reorganization of its three main compartments: fibrillar center (FC), dense fibrillar component (DFC), and granular component (GC). Stress can lead to nucleolar segregation, fragmentation, or changes in nucleolar size and shape, affecting ribosome subunit production and cell growth. Stress responses involve complex signaling pathways that regulate ribosome subunit biogenesis, including the mTOR pathway, which controls RNA polymerase I activity and ribosomal protein (RP) translation. Stress can also influence the nucleolar proteome, with changes in protein localization and function affecting nucleolar integrity and function. The nucleolus plays a central role in the stress response by coordinating the activation of p53, which is crucial for cell-cycle arrest and apoptosis. p53 stability is regulated by interactions with proteins such as Hdm2, and stress can alter these interactions through mechanisms like p14ARF upregulation, RPL11 de-NEDDylation, and changes in protein-protein interactions. The nucleolus and Cajal bodies (CBs) are closely linked in stress responses. CBs are involved in RNA processing and are affected by stress, with changes in coilin localization and CB structure. Stress can lead to CB disruption, which may be linked to snRNP biogenesis and cell-cycle progression. The nucleolus and CBs are involved in various cellular functions beyond ribosome biogenesis, including DNA repair, viral infection, and cell-cycle control. Stress-induced changes in these organelles are regulated by posttranslational modifications (PTMs) and signaling pathways, highlighting the nucleolus's role as a central hub in the stress response. Understanding the molecular mechanisms underlying nucleolar and CB responses to stress is essential for elucidating the cellular stress response and its implications in diseases such as cancer and neurodegenerative disorders. Further research into these mechanisms may provide insights into the development of therapeutic strategies for these conditions.