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Fluctuations of DNA‐dependent RNA polymerase and synthesis of macromolecules during the growth cycle of Novikoff rat hepatoma cells in suspension culture
Author(s) -
Ward Gary A.,
Plagemann Peter G. W.
Publication year - 1969
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040730307
Subject(s) - polysome , puromycin , rna , protein biosynthesis , biology , rna polymerase , dna , polymerase , dna synthesis , microbiology and biotechnology , incubation , ribosome , ribosomal rna , biochemistry , cell division , cell , gene
The transition of suspension cultures of Novikoff rat hepatoma cells from the exponential to the stationary phase is accompanied by decreases of over 90% in the rates of synthesis of RNA, DNA and protein, a 90% loss of the apparent DNA‐dependent RNA polymerase activity of the cells, and a disaggregation of the polyribosomes with a concomitant accumulation of 80 S and 110 S ribosomal structures. The cells also attain a minimum content of DNA, RNA and protein and a minimum size. Upon dilution of stationary phase cultures with fresh medium, the rate of protein synthesis begins to increase immediately and this correlates with a rapid reformation of the polyribosomes. The initial re‐formation of polyribosomes is little affected by the presence of actinomycin D. RNA polymerase activity also begins to increase immediately after dilution and an increase in rate of RNA synthesis becomes apparent shortly thereafter. The increase in polymerase activity is inhibited by treating the cells with puromycin or actidione. Cell division commences only 9–13 hours after dilution and the rate of DNA synthesis begins to increase about midway through the lag period. During the lag period the average cellular content of protein increases about 80% and that of RNA and DNA about 30%. These increases are accompanied by a marked increase in the average size of the cells. Upon continued incubation of stationary phase cultures, the cells become irreversibly damaged physiologically before gross morphological damage becomes apparent. The irreversible physiological damage is recognized by the fact that the cells fail to recover when suspended in fresh medium.