Down-regulation of the Cyclin A Promoter by Transforming Growth Factor-β1 Is Associated with a Reduction in Phosphorylated Activating Transcription Factor-1 and Cyclic AMP-responsive Element-binding Protein*
Down-regulation of the Cyclin A Promoter by Transforming Growth Factor-β1 Is Associated with a Reduction in Phosphorylated Activating Transcription Factor-1 and Cyclic AMP-responsive Element-binding Protein*
复制标题
DOI：
10.1074/jbc.272.35.22259
复制
发表时间：
1997-08
期刊：
影响因子：
--
通讯作者：
M. Yoshizumi;H Wang-;C. Hsieh;N. Sibinga;M. Perrella;M. -. Lee
中科院分区：
文献类型：
--
作者：
M. Yoshizumi;H Wang-;C. Hsieh;N. Sibinga;M. Perrella;M. -. Lee
转化生长因子（TGF）-β1通过抑制几种调节因子（包括细胞周期蛋白A）阻止细胞周期进程。为了研究TGF-β1下调cyclin A基因表达的机制，我们将cyclin A启动子驱动的报告质粒转染貂肺上皮细胞，在TGF-β1存在和不存在的情况下进行研究。TGF-β1诱导的cyclin A启动子活性下调似乎是通过转录激活因子（ATF）位点介导的，因为该位点的突变取消了下调。令人惊讶的是，尽管TGF-β1处理24 h显著降低了细胞周期蛋白A启动子活性，但它并没有降低ATF结合蛋白ATF-1和环AMP反应结合蛋白（CREB）的丰度。然而，我们检测到用TGF-β1处理的貂肺上皮细胞中磷酸化CREB和ATF-1分别减少了90%和78%（通过Western分析）。TGF-β1诱导的细胞周期蛋白A启动子活性下调可被冈田酸（一种磷酸酶抑制剂）逆转，也可通过与表达cAMP依赖性蛋白激酶催化亚基或猴病毒小肿瘤抗原（Sm-t，一种PP 2A抑制剂）的质粒共转染逆转。这些数据表明，TGF-β1可能通过降低CREB和ATF-1的磷酸化而下调细胞周期蛋白A启动子活性。
Transforming growth factor (TGF)-β1 prevents cell cycle progression by inhibiting several regulators, including cyclin A. To study the mechanisms by which TGF-β1 down-regulates cyclin A gene expression, we transfected reporter plasmids driven by the cyclin A promoter into mink lung epithelial cells in the absence and presence of TGF-β1. The TGF-β1-induced down-regulation of cyclin A promoter activity appeared to be mediated via the activating transcription factor (ATF) site, because mutation of this site abolished down-regulation. Surprisingly, although TGF-β1 treatment for 24 h markedly decreased cyclin A promoter activity, it did not decrease the abundance of the ATF-binding proteins ATF-1 and cyclic AMP-responsive binding protein (CREB). However, we detected 90 and 78% reductions (by Western analysis) in phosphorylated CREB and ATF-1, respectively, in mink lung epithelial cells treated with TGF-β1. TGF-β1-induced down-regulation of cyclin A promoter activity was reversed by okadaic acid (a phosphatase inhibitor) and by cotransfection with plasmids expressing the cAMP-dependent protein kinase catalytic subunit or the simian virus small tumor antigen (Sm-t, an inhibitor of PP2A). These data indicate that TGF-β1 may down-regulate cyclin A promoter activity by decreasing phosphorylation of CREB and ATF-1.