Kimura K, Saijo M, Ui M, Enomoto T
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
J Biol Chem. 1994 Jan 14;269(2):1173-6.
The fluctuations in the expression of two forms of DNA topoisomerase II, p170 and p180, were examined by immunoblotting during the transition of the growth state and the cell cycle in Swiss 3T3 cells. The level of p170 expression was higher during the exponentially growing phase than in the stationary phase, and the level of p180 did not appear to change when the cells changed the growth state. When quiescent cells were stimulated with serum, the p170 level began to increase at 12 h and reached a maximal level at 24-28 h, corresponding to the G2 phase. In contrast, the level of p180 was almost constant during the cell cycle, and the p180 band became obscure when the number of mitotic cells increased. Immunoblotting of the samples prepared from metaphase-synchronized HeLa cells did not have a p180 band, but did exhibit a band with a higher molecular weight. This band increased and p180 decreased in parallel with the increase in the number of mitotic cells. When the cells exited from the M phase, p180 reappeared and the higher molecular weight band disappeared.
通过免疫印迹法检测了瑞士3T3细胞在生长状态和细胞周期转变过程中两种形式的DNA拓扑异构酶II（p170和p180）表达的波动情况。在指数生长期，p170的表达水平高于静止期，当细胞改变生长状态时，p180的水平似乎没有变化。当静止细胞受到血清刺激时，p170水平在12小时开始升高，并在24 - 28小时达到最高水平，这与G2期相对应。相比之下，p180的水平在细胞周期中几乎保持恒定，当有丝分裂细胞数量增加时，p180条带变得模糊不清。从中期同步化的HeLa细胞制备的样品进行免疫印迹时，没有p180条带，但确实显示出一条分子量更高的条带。随着有丝分裂细胞数量的增加，这条带增加而p180减少。当细胞从M期退出时，p180重新出现，分子量更高的条带消失。
