David-Pfeuty T, Nouvian-Dooghe Y, Sirri V, Roussel P, Hernandez-Verdun D
UMR 146 du CNRS, Institut Curie-Recherche, Bâtiment 110, Centre Universitaire, 91405 Orsay Cédex, France.
Oncogene. 2001 Sep 20;20(42):5951-63. doi: 10.1038/sj.onc.1204741.
Two specific inhibitors of cyclin-dependent kinase 2 (Cdk2), roscovitine and olomoucine, have been shown recently to induce nuclear accumulation of wt p53 and nucleolar unravelling in interphase human untransformed IMR-90 and breast tumor-derived MCF-7 cells. Here, we show that the early response of MCF-7 cells to roscovitine is fully reversible since a rapid restoration of nucleolar organization followed by an induction of p21(WAF1/CIP1), a downregulation of nuclear wt p53 and normal cell cycle resumption occurs if the compound is removed after 4 h. Interestingly, similar reversible effects are also induced by the casein kinase II (CKII) inhibitor, 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole. Upon short-term treatment also, both compounds significantly, but reversibly, reduce the level of 45S precursor ribosomal RNA. Cells exposed to the two types of protein kinase inhibitors for longer times keep exhibiting altered nucleolar and wt p53 features, yet they strikingly differentiate in that most roscovitine-treated cells fail to ever accumulate high levels of p21(WAF1/CIP1) in contrast with DRB-treated ones. In both cases, however, the cells eventually fall into an irreversible state and die. Moreover, we found that constitutive overexpression of p21(WAF1/CIP1) alters the nucleolar unravelling process in the presence of DRB, but not of roscovitine, suggesting a role for this physiological Cdk inhibitor in the regulation of nucleolar function. Our data also support the notion that both roscovitine- and DRB-sensitive protein kinases, probably including Cdk2 and CKII, via their dual implication in the p53-Rb pathway and in ribosomal biogenesis, would participate in coupling cell growth with cell division.
细胞周期蛋白依赖性激酶2（Cdk2）的两种特异性抑制剂，即罗斯考维汀和olomoucine，最近已被证明可诱导野生型p53在细胞核内积聚，并使间期人类未转化的IMR - 90细胞和乳腺癌来源的MCF - 7细胞的核仁解聚。在此，我们表明MCF - 7细胞对罗斯考维汀的早期反应是完全可逆的，因为如果在4小时后去除该化合物，核仁组织会迅速恢复，随后诱导p21（WAF1/CIP1），细胞核内野生型p53下调，细胞周期恢复正常。有趣的是，酪蛋白激酶II（CKII）抑制剂5,6 - 二氯 - 1 - β - D - 呋喃核糖基苯并咪唑也能诱导类似的可逆效应。短期处理后，这两种化合物也会显著但可逆地降低45S前体核糖体RNA的水平。长时间暴露于这两种蛋白激酶抑制剂的细胞仍表现出核仁及野生型p53特征的改变，但它们有显著差异，与DRB处理的细胞相比，大多数罗斯考维汀处理的细胞始终无法积累高水平的p21（WAF1/CIP1）。然而，在这两种情况下，细胞最终都会进入不可逆状态并死亡。此外，我们发现p21（WAF1/CIP1）的组成型过表达在存在DRB而非罗斯考维汀的情况下会改变核仁解聚过程，这表明这种生理性Cdk抑制剂在核仁功能调节中发挥作用。我们的数据还支持这样一种观点，即罗斯考维汀和DRB敏感的蛋白激酶，可能包括Cdk2和CKII，通过它们在p53 - Rb途径和核糖体生物合成中的双重作用，参与将细胞生长与细胞分裂耦合起来。
