Enhanced sensitivity of nucleoli in human proliferating cells to inhibition of protein synthesis with anisomycin.

We describe the reaction of nuclei in cultured human cells from different tissues to inhibition of total protein synthesis with anisomycin - ribotoxin, which is now considered as a potential antitumor drug. It was shown that nucleoli in sensitive cells demonstrate typical reaction: under the action of the inhibitor, labile nucleolar protein, a component of RNA polymerase I transcription complex (previously called A3 antigen), rapidly migrates from the nucleolus to numerous discrete foci in the nucleoplasm. These changes are specific for translation suppression and are not induced by other influences on the cells. Migration of A3 antigen into the nucleoplasm manifests primarily in cells at the stage of DNA replication and is absent in resting cells. These results suggest that localization of A3 antigen can be a marker of artificial suppression of translation in proliferating human cells in vitro.

Changes in the status of nucleolus during long-term culturing of human HeLa cells.

Changes in the immunocytochemical status of the nucleoli during long-term (6-8 months) in vitro culturing of HeLa (carcinoma of the cervix uteri) cells were described using new A3 monoclonal antibodies selectively reacting with human cell nucleoli. The appearance of cells with abnormal location of A3 antigen was paralleled by a significant increase of culture sensitivity to some external factors (protein synthesis inhibition and oxidative stress). The data indicate that location of one of the nucleolar antigens is an indicator of the qualitative status of HeLa cells in the culture.