© 1988 Oxford University Press
research-article |
Cell cycle progression of C3H 10T
and 3T3 cells in the absence of an increase in c-myc RNA levels
Department of Cancer Biology, Harvard University School of Public Health 665 Huntington Avenue, Boston, MA 02115, USA
Normally, when confluent cells are stimulated to divide, they show a transient increase in c-myc RNA levels (1–5). This has led many investigators to believe that the rise in c-myc RNA is causally related to the control and regulation of cell proliferation. However, we report here that the rise in c-myc RNA levels is not observed in stimulated cycling C3H 10T
and 3T3 cells that have heen grown to confluence in the presence of the protease inhibitor antipain. Cells continue to progress from the G0/G1 phase to S phase of the cell cycle in the absence of an increase in c-myc RNA; the kinetics of [3H]thymidine incorporation after serum stimulation are comparable to those observed in cells in which c-myc RNA levels rise after serum stimulation. Our observations are of significance because they suggest a dissociation between the transient rise of c-myc RNA which occurs before DNA synthesis and the events that initiate DNA synthesis in quiescent fibroblasts; c-myc may not play as central a role in stimulating noncycling, quiescent cells to progress through the cell cycle, as has been generally assumed.