Half-Lives of Ornithine Decarboxylase and S-Adenosylmethionine Decarboxylase Activities during the Cell Cycle of Chinese Hamster Ovary Cells

Abstract

Cells in mitosis were seeded immediately after being harvested by the mitotic shake off technique from a culture of exponentially growing Chinese hamster ovary cells. At 2, 5, 7, 10, and 12 h after seeding, cycloheximide was added. Cells were sampled at various times after cycloheximide addition and the ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) activities were determined. Flow cytometric analysis showed that cells sampled at 2, 5, 7, 10, and 12 h after seeding were found in mid G1, at the G1/S transition, in mid S phase, at the S/G2 transition, and in late G2, respectively. The half-lives of ODC and AdoMetDC activities varied during the cell cycle. The half-life of ODC activity showed a biphasic pattern with increases in connection to the G1/S and S/G2 transitions while the half-life of AdoMetDC activity increased only at the G1/S transition.