Bilodeau J F, Faure R, Piedboeuf B, Mirault M E
Unit of Health and Environment, Laval University Medical Research Centre, CHUQ, Department of Medicine, Laval University, Ste-Foy, Québec, Canada.
Exp Cell Res. 2000 May 1;256(2):347-57. doi: 10.1006/excr.2000.4844.
Little is known about cell-cycle checkpoint activation by oxidative stress in mammalian cells. The effects of hyperoxia on cell-cycle progression were investigated in asynchronous human T47D-H3 cells, which contain mutated p53 and fail to arrest at G1/S in response to DNA damage. Hyperoxic exposure (95% O(2), 40-64 h) induced an S-phase arrest associated with acute inhibition of Cdk2 activity and DNA synthesis. In contrast, exit from G2/M was not inhibited in these cells. After 40 h of hyperoxia, these effects were partially reversible during recovery under normoxic conditions. The inhibition of Cdk2 activity was not due to degradation of Cdk2, cyclin E or A, nor impairment of Cdk2 complex formation with cyclin A or E and p21(Cip1). The loss of Cdk2 activity occurred in the absence of induction and recruitment of cdk inhibitor p21(Cip1) or p27(Kip1) in cyclin A/Cdk2 or cyclin E/Cdk2 complexes. In contrast, Cdk2 inhibition was associated with increased Cdk2-Tyr15 phosphorylation, increased E2F-1 recruitment, and decreased PCNA contents in Cdk2 complexes. The latter results indicate a p21(Cip1)/p27(Kip1)-independent mechanism of S-phase checkpoint activation in the hyperoxic T47D cell model investigated.
关于氧化应激在哺乳动物细胞中激活细胞周期检查点的情况，人们了解甚少。在含有突变型p53且在DNA损伤时无法在G1/S期停滞的人T47D-H3细胞中，研究了高氧对细胞周期进程的影响。高氧暴露（95% O₂，40 - 64小时）诱导了S期停滞，这与Cdk2活性和DNA合成的急性抑制相关。相比之下，这些细胞从G2/M期退出并未受到抑制。高氧暴露40小时后，在常氧条件下恢复过程中，这些影响部分是可逆的。Cdk2活性的抑制并非由于Cdk2、细胞周期蛋白E或A的降解，也不是由于Cdk2与细胞周期蛋白A或E以及p21(Cip1)形成复合物的能力受损。Cdk2活性的丧失发生在细胞周期蛋白A/Cdk2或细胞周期蛋白E/Cdk2复合物中未诱导和募集细胞周期蛋白依赖性激酶抑制剂p21(Cip1)或p27(Kip1)的情况下。相反，Cdk2抑制与Cdk2-Tyr15磷酸化增加、E2F-1募集增加以及Cdk2复合物中增殖细胞核抗原（PCNA）含量降低相关。后一结果表明在所研究的高氧T47D细胞模型中，存在一种不依赖p21(Cip1)/p27(Kip1)的S期检查点激活机制。
