CYTOPATHOLOGICAL EFFECTS OF A TRANSLATION INHIBITOR, EMETINE, ON HeLa CELLS AND THEIR NUCLEOLI
O. Yu. Smirnova, V. A. Mishina, O. V. Zatsepina 1
A. N. Belozersky Institute of Physical and Chemical Biology, Moscow State University, Russia;
1 e-mail: zatsepin@genebee.msu.su
Eukaryotic cell nucleolus is a highly dynamic structure, which is sensitive to all changes within or outside
cell borders. Numerous data are available on changes of the nucleolar structure and functions under different
treatments. However, almost nothing is known about the action of translation inhibitors on the nucleolus, although
these substances, together with TNF-α, are commonly used for apoptosis induction, both for scientific and
therapeutic purposes. Emetine is one of such inhibitors. We have shown that emetine suppresses cell viability,
decreases mitotic index, and induces apoptosis in HeLa cells. Emetine action is irreversible, and it sensitizes
cells to unfavourable external conditions. The emetine action causes redistribution of UBF, one of RNA-polymerase I
factor, from the nucleolus to nucleoplasm even after a short exposure, i. e. when the morphology of the nucleus and
chromatin still keeps its native pattern. It is important that other nucleolar proteins, such as fibrillarin and
B23, are not recognized in the nucleoplasm until the very late stages of apoptotic process. A suggestion is made
that changes in UBF localization may be associated with the onset of ribosomal repeat cleavage and migration of
rDNA-"free" fragments from the nucleolus to nucleoplasm. It looks likely that these changes can serve as an
initial morphological indication of apoptosis.
Key words: nucleolus, emetine, apoptosis, cell cycle
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