Regulation of the human cyclin-dependent kinase inhibitor p18INK4c by the transcription factors E2F1 and Sp1
Regulation of the human cyclin-dependent kinase inhibitor p18INK4c by the transcription factors E2F1 and Sp1
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DOI：
10.1074/jbc.m204554200
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发表时间：
2002-08-30
影响因子：
4.8
通讯作者：
Labrie, C
中科院分区：
文献类型：
--
作者：
Blais, A;Monté, D;Labrie, C
p18（INK 4c）细胞周期蛋白依赖性激酶抑制剂是细胞周期进程和细胞分化的重要调节剂。我们和其他人发现，过表达的E2 F蛋白上调p18的表达。为了更好地理解这一现象，我们对人p18启动子进行了功能分析。缺失研究表明，启动子的E2 F响应元件位于转录起始位点上游131 bp内。该区域含有推定的Sp1和E2 F结合位点。这些元件的突变失活表明，Sp1位点对启动子的基础活性很重要，但也可以介导E2 F1对p18启动子的影响。此外，我们发现E2 F1和Sp1可以协同增强近端p18启动子的活性。凝胶位移分析，使用p18启动子衍生的探针导致几个多蛋白复合物，发现含有不同的组合E2 F蛋白和/或Sp1的鉴定。重组E2 F1也能够与E2 F结合位点结合。染色质免疫沉淀实验表明，E2 F1和E2 F4与未受干扰的细胞中的p18启动子。基于这些发现，我们得出结论，E2 F蛋白和Sp1在p18表达的控制中发挥重要作用。
The p18(INK4c) cyclin-dependent kinase inhibitor is an important regulator of cell cycle progression and cellular differentiation. We and others found that overexpressed E2F proteins up-regulate p18 expression. To better understand this phenomenon, we performed a functional analysis of the human p18 promoter. Deletion studies revealed that the E2F-responsive elements of the promoter are located within 131 bp upstream of the transcription start site. This region contains putative Sp1- and E2F-binding sites. Mutational inactivation of these elements revealed that the Sp1 sites were important for the basal activity of the promoter but could also mediate the effects of E2F1 on the p18 promoter. Moreover, we found that E2F1 and Sp1 can synergistically enhance the activity of the proximal p18 promoter. Gel shift analyses using p18 promoter-derived probes led to the identification of several multiprotein complexes that were found to contain different combinations of E2F proteins and/or Sp1. Recombinant E2F1 was also capable of binding to the E2F-binding sites. Chromatin immunoprecipitation experiments demonstrated that E2F1 and E2F4 associate with the p18 promoter in unperturbed cells. Based on these findings, we conclude that E2F proteins and Sp1 play an important role in the control of p18 expression.