ORNITHINE DECARBOXYLASE AND S-ADENOSYLMETHIONINE DECARBOXYLASE EXPRESSION DURING THE CELL-CYCLE OF CHINESE-HAMSTER OVARY CELLS

Cells in mitosis were harvested from exponentially growing Chinese ham ster ovary cells by the mitotic detachment technique. Immediately afte r harvesting, the mitotic cells were seeded in tissue culture flasks a nd incubated at 37 degrees C in a CO2 incubator. Care was taken not to perturb the progression of cells through the cell cycle. At every hou r after seeding for 14 h, cells were collected for analysis of cell cy cle distribution, cellular polyamine content, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) activities, an d relative mRNA contents. The progression through the cell cycle was m onitored by DNA flow cytometry. The putrescine, spermidine, and spermi ne levels were approximately doubled during the cell cycle: putrescine mainly during late S and G(2), spermidine continuously during the ent ire cell cycle, and spermine mainly during G(1) and S. The ODC activit y was low in seeded mitotic cells and the enzyme was activated in late G(1) and reached a plateau in S phase. A second burst in activity was observed during late S phase and maximal ODC activity was found at th e S/G(2) transition. The relative ODC mRNA level approximately doubled during the cell cycle and the increase in the relative level mainly t ook part during mid and late S phase. AdoMetDC activity increased in l ate G(1) and a first maximum was observed during the G(1)/S transition . A second burst in activity was found in mid S phase. Maximal AdoMetD C activity was found in G(2). The relative AdoMetDC mRNA approximately doubled during the cell cycle and the increase in the relative level mainly took place during late G(1) and early S phase. Our results indi cate that polyamine synthesis was regulated at transcriptional and tra nslational/post-translational levels during the cell cycle of Chinese hamster ovary cells. (C) 1995 Academic Press, Inc.