DNA TOPOISOMERASE-I AND TOPOISOMERASE-II ACTIVITIES DURING CELL-PROLIFERATION AND THE CELL-CYCLE IN CULTURED MOUSE EMBRYO FIBROBLAST (C3H 10T1/2) CELLS
DNA TOPOISOMERASE-I AND TOPOISOMERASE-II ACTIVITIES DURING CELL-PROLIFERATION AND THE CELL-CYCLE IN CULTURED MOUSE EMBRYO FIBROBLAST (C3H 10T1/2) CELLS
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DOI：
10.1016/0014-4827(85)90426-4
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发表时间：
1985-01-01
影响因子：
3.7
通讯作者：
KOWALSKI, D
中科院分区：
文献类型：
--
作者：
TRICOLI, JV;SAHAI, BM;KOWALSKI, D
C3H 10T1/2 cells were used to examine the regulation of topoisomerase activities during cell proliferation and the cell cycle. The specific activity of topoisomerase I was about 4-fold greater in proliferating (log phase) cells than in non-proliferating (confluent) cells. In synchronized cells, the bulk of the increased activity occurred during or just prior to S phase, depending upon the method of synchronization. A smaller increase in activity also occurred during G1 phase. The increase in activity during S phase was not altered by a hydroxyurea block at the G1/S phase boundary indicating that it is not directly coupled to DNA synthesis and is not the result of topoisomerase I gene dosage. The increase was inhibited by blocking cells at mid-G1 phase using isoleucine deprivation. Thus, the increase in activity during S phase is dependent on events occurring during mid- to late G1 phase. In contrast to the changes in topoisomerase I levels, the specific activity of topoisomerase II showed no detectable differences in proliferating vs. non-proliferating cells. No detectable differences in topoisomerase II specific activity was seen in G1, S and M phases of the cell cycle. The differences in the activity profiles of the topoisomerases I and II during the cell cycle suggest that the 2 activities are regulated independently and may be required for different functions.
