Regulation of late G1/S phase transition and APCCdh1 by reactive oxygen species
Regulation of late G1/S phase transition and APCCdh1 by reactive oxygen species
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DOI：
10.1128/mcb.00303-06
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发表时间：
2006-06-01
影响因子：
5.3
通讯作者：
Dowdy, Steven F.
中科院分区：
文献类型：
--
作者：
Havens, Courtney G.;Ho, Alan;Dowdy, Steven F.
增殖细胞比静止细胞具有更高的代谢率。为了研究代谢在细胞周期进程中的作用，我们检查了从早期 G(1) 到 S 期的高度同步的细胞群中的细胞大小、线粒体质量和活性氧 (ROS) 水平。我们发现，在整个细胞周期中，与细胞大小和线粒体质量相比，ROS 稳步增加。由于 ROS 已被证明会影响细胞增殖和转化，因此我们假设 ROS 可能有助于细胞周期进程。细胞的抗氧化处理诱导晚期 G(1) 期细胞周期停滞，其特征是持续的细胞生长、活性细胞周期蛋白 D-Cdk4/6 和活性细胞周期蛋白 E-Cdk2 激酶以及失活的过度磷酸化 pRb。然而，经过抗氧化剂处理的细胞未能积累细胞周期蛋白 A，而细胞周期蛋白 A 是启动 DNA 合成的必要步骤。进一步检查表明，细胞周期蛋白 A 继续被后期促进复合物 (APC) 泛素化，并被蛋白酶体降解。这种抗氧化停滞可以通过 APC 抑制剂 Emi1 的过度表达来挽救。这些观察结果揭示了一个内在的晚期 G(1) 相检查点，在跨越生长因子依赖性 G(1) 限制点后，该检查点通过与 Cdh1 相关的 APC 的持续活动，将内源 ROS 稳态水平的增加与细胞周期进展联系起来。
Proliferating cells have a higher metabolic rate than quiescent cells. To investigate the role of metabolism in cell cycle progression, we examined cell size, mitochondrial mass, and reactive oxygen species (ROS) levels in highly synchronized cell populations progressing from early G(1) to S phase. We found that ROS steadily increased, compared to cell size and mitochondrial mass, through the cell cycle. Since ROS has been shown to influence cell proliferation and transformation, we hypothesized that ROS could contribute to cell cycle progression. Antioxidant treatment of cells induced a late-G(1)-phase cell cycle arrest characterized by continued cellular growth, active cyclin D-Cdk4/6 and active cyclin E-Cdk2 kinases, and inactive hyperphosphorylated pRb. However, antioxidant-treated cells failed to accumulate cyclin A protein, a requisite step for initiation of DNA synthesis. Further examination revealed that cyclin A continued to be ubiquitinated by the anaphase promoting complex (APC) and to be degraded by the proteasome. This antioxidant arrest could be rescued by overexpression of Emi1, an APC inhibitor. These observations reveal an intrinsic late-G(1)-phase checkpoint, after transition across the growth factor-dependent G(1) restriction point, that links increased steady-state levels of endogenous ROS and cell cycle progression through continued activity of APC in association with Cdh1.