Pyo Chul-Woong, Choi Joon Hwan, Oh Sang-Muk, Choi Sang-Yun
Department of Life Sciences, School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
Biochim Biophys Acta. 2013 Nov;1830(11):5316-25. doi: 10.1016/j.bbagen.2013.07.030. Epub 2013 Aug 3.
Cyclin D1 is immediately down-regulated in response to reactive oxygen species (ROS) and implicated in the induction of cell cycle arrest in G2 phase by an unknown mechanism. Either treatment with a protease inhibitor alone or expression of protease-resistant cyclin D1 T286A resulted in only a partial relief from the ROS-induced cell cycle arrest, indicating the presence of an additional control mechanism.
Cells were exposed to hydrogen peroxide (H2O2), and analyzed to assess the changes in cyclin D1 level and its effects on cell cycle processing by kinase assay, de novo synthesis, gene silencing, and polysomal analysis, etc.
Exposure of cells to excessive H2O2 induced ubiquitin-dependent proteasomal degradation of cyclin D1, which was subsequently followed by translational repression. This dual control mechanism was found to contribute to the induction of cell cycle arrest in G2 phase under oxidative stress. Silencing of an eIF2α kinase PERK significantly retarded cyclin D1 depletion, and contributed largely to rescuing cells from G2 arrest. Also the cyclin D1 level was found to be correlated with Chk1 activity.
In addition to an immediate removal of the pre-existing cyclin D1 under oxidative stress, the following translational repression appear to be required for ensuring full depletion of cyclin D1 and cell cycle arrest. Oxidative stress-induced cyclin D1 depletion is linked to the regulation of G2/M transit via the Chk1-Cdc2 DNA damage checkpoint pathway.
The control of cyclin D1 is a gate keeping program to protect cells from severe oxidative damages.
细胞周期蛋白D1会因活性氧（ROS）而立即下调，并通过未知机制参与诱导细胞周期停滞于G2期。单独使用蛋白酶抑制剂处理或表达抗蛋白酶的细胞周期蛋白D1 T286A仅能部分缓解ROS诱导的细胞周期停滞，这表明存在额外的控制机制。
将细胞暴露于过氧化氢（H2O2）中，并通过激酶测定、从头合成、基因沉默和多核糖体分析等方法进行分析，以评估细胞周期蛋白D1水平的变化及其对细胞周期进程的影响。
细胞暴露于过量的H2O2会诱导细胞周期蛋白D1的泛素依赖性蛋白酶体降解，随后发生翻译抑制。发现这种双重控制机制有助于在氧化应激下诱导细胞周期停滞于G2期。沉默eIF2α激酶PERK可显著延缓细胞周期蛋白D1的消耗，并在很大程度上有助于使细胞从G2期停滞中解救出来。还发现细胞周期蛋白D1水平与Chk1活性相关。
除了在氧化应激下立即清除预先存在的细胞周期蛋白D1外，后续的翻译抑制似乎对于确保细胞周期蛋白D1的完全消耗和细胞周期停滞是必需的。氧化应激诱导的细胞周期蛋白D1消耗与通过Chk1-Cdc2 DNA损伤检查点途径对G2/M转换的调节有关。
细胞周期蛋白D1的控制是一种保护细胞免受严重氧化损伤的守门程序。
