Regulated expression of cofilin and the consequent regulation of p27kip1 are essential for G1 phase progression
Regulated expression of cofilin and the consequent regulation of p27kip1 are essential for G1 phase progression
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DOI：
10.4161/cc.8.15.9072
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发表时间：
2009-08-01
期刊：
影响因子：
4.3
通讯作者：
Lee, Yi-Jang
中科院分区：
文献类型：
--
作者：
Tsai, Cheng-Han;Chiu, Shu-Jun;Lee, Yi-Jang
Cofilin 是一种普遍表达的肌动蛋白结合蛋白，负责肌动蛋白细胞骨架的形成，对于细胞周期控制是不可或缺的。然而，丝切蛋白表达与细胞周期之间的关联仍有待阐明。在这项研究中，我们发现 G(1) 期停滞的汇合细胞中 cofilin 的表达水平上调，而这些细胞中小干扰 RNA (siRNA) 敲低 cofilin 表达导致 G(1) 细胞数量减少。为了研究 cofilin 在控制 G(1) 期进展中的作用，引入了 tet-on 基因表达系统以在细胞中过表达不同浓度的 cofilin。结果表明，外源丝切蛋白诱导后，G(1)期进展被阻断。对控制 G(1) 期进展的细胞周期蛋白的调查表明，细胞周期蛋白依赖性激酶抑制剂 (CKI) p27(kip1) 是过表达的丝切蛋白以时间和剂量依赖性方式诱导的主要分子。上调 p27(kip1) 抑制由细胞周期蛋白 D1/CDK4 活性介导的视网膜母细胞瘤蛋白 (Rb) 的磷酸化。相反，针对 cofilin 过表达细胞中 p27(kip1) 表达的 siRNA 释放了 G(1) 期停滞。此外，我们使用荧光素酶报告基因测定发现，cofilin 的过度表达导致 p27(kip1) 基因启动子反式激活的诱导。这种效应与 p27(kip1) mRNA 的瞬时增加有关。此外，抑制泛素蛋白酶体介导的 p27(kip1) 蛋白苏氨酸 187 磷酸化也参与 p27(kip1) 的上调。这些数据表明 cofilin 表达及其对 p27(kip1) 表达的调节对于 G(1) 期进展的控制很重要。
Cofilin, a ubiquitously expressed actin binding protein, is responsible for the formation of the actin cytoskeleton and is indispensable for cell cycle control. However, the association between cofilin expression and the cell cycle remains to be elucidated. In this study, we found that the expression level of cofilin upregulated in G(1) phase-arrested confluent cells, while knockdown of cofilin expression by small interference RNA (siRNA) in these cells led to a reduction in the population of G(1) cells. To investigate the role of cofilin in the control of G(1) phase progression, a tet-on gene expression system was introduced to overexpress different concentrations of cofilin in cells. The results showed that G(1) phase progression was blocked following induction of exogenous cofilin. A survey of the cell cycle proteins controlling the G(1) phase progression revealed that the cyclin-dependent kinase inhibitor (CKI) p27(kip1) was the primary molecule induced by overexpressed cofilin in a time and dose dependent manner. Upregulated p27(kip1) repressed phosphorylation of the retinoblastoma protein (Rb) mediated by cyclin D1/CDK4 activity. Conversely, siRNA against p27(kip1) expression in the cofilin overexpressing cells released the G(1) phase arrest. Furthermore, we found that overexpression of cofilin led to induction of p27(kip1) gene promoter transactivation using luciferase reporter gene assay. This effect was associated with increase of p27(kip1) mRNA transiently. In addition, inhibition of threonine-187 phosphorylation of p27(kip1) protein for ubiquitinyl-proteasomal mediated degradation was also involved in upregulation of p27(kip1). These data suggest that cofilin expression and its regulation of p27(kip1) expression is important for the control of G(1) phase progression.