HuR contributes to cyclin E1 deregulation in MCF-7 breast cancer cells
HuR contributes to cyclin E1 deregulation in MCF-7 breast cancer cells
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DOI：
10.1158/0008-5472.can-05-4362
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发表时间：
2006-08-15
期刊：
影响因子：
11.2
通讯作者：
Hartley, Rebecca S.
中科院分区：
文献类型：
--
作者：
Guo, Xun;Hartley, Rebecca S.
许多癌症过表达细胞周期蛋白El及其肿瘤特异性低分子量（LMW）同种型。然而，细胞周期蛋白El失调在癌症中的机制仍然没有很好地理解。我们发现mRNA结合蛋白HuR增加了MCF-7乳腺癌细胞中细胞周期蛋白El mRNA的稳定性。因此，mRNA稳定化可能是MCF-7细胞中细胞周期蛋白El失调的关键事件。与MCF 10A永生化乳腺上皮细胞相比，MCF-7细胞过表达全长细胞周期蛋白El及其LMW亚型，并表现出增加的细胞周期蛋白El mRNA的稳定性。mRNA稳定性的增加与稳定的腺苷酸化状态和细胞质与细胞核HuR比率的增加有关。UV交联竞争和UV交联免疫沉淀实验证实HuR特异性结合于细胞周期蛋白E1 3 '非翻译区。在MCF-7细胞中用小干扰RNA（siRNA）敲低HuR降低细胞周期蛋白El mRNA半衰期（t（1/2））及其蛋白水平：全长亚型降低22%，LMW亚型降低80%。Hall siRNA还延迟了G（1）-S期转换，抑制MCF-7细胞增殖，这部分恢复过表达的细胞周期蛋白E1的LMW亚型。在MCF 10 A细胞中，HuR过表达可增加细胞周期蛋白E1 mRNA t（1/2）及其蛋白水平。总而言之，我们的数据表明，Hall对细胞周期蛋白El过表达及其促生长功能做出了关键贡献，至少部分是通过增加细胞周期蛋白El mRNA的稳定性，这提供了乳腺癌细胞周期蛋白El失调的新机制。
Many cancers overexpress cyclin El and its tumor-specific low molecular weight (LMW) isoforms. However, the mechanism of cyclin El deregulation in cancers is still not well understood. We show here that the mRNA-binding protein HuR increases cyclin El mRNA stability in MCF-7 breast carcinoma cells. Thus, mRNA stabilization may be a key event in the deregulation of cyclin El in MCF-7 cells. Compared with MCF10A immortalized breast epithelial cells, MCF-7 cells overexpress full-length cyclin El and its LMW isoforms and exhibit increased cyclin El mRNA stability. Increased mRNA stability is associated with a stable adenylation state and an increased ratio of cytoplasmic versus nuclear HuR. UV crosslink competition and UV cross-link immunoprecipitation assays verified that HuR specifically bound to the cyclin El 3'-untranslated region. Knockdown of HuR with small interfering RNA (siRNA) in MCF-7 cells decreased cyclin El mRNA half-life (t(1/2)) and its protein level: a 22% decrease for the full-length isoforms and 80% decrease for the LMW isoforms. Hall siRNA also delayed G(1)-S phase transition and inhibited MCF-7 cell proliferation, which was partially recovered by overexpression of a LMW isoform of cyclin E1. Overexpression of HuR in MCF10A cells increased cyclin E1 mRNA t(1/2) and its protein level. Taken together, our data show that Hall critically contributes to cyclin El overexpression and its growth-promoting function, at least in part by increasing cyclin El mRNA stability, which provides a new mechanism of cyclin El deregulation in breast cancer.