Armenia Joshua, Fabris Linda, Lovat Francesca, Berton Stefania, Segatto Ilenia, D'Andrea Sara, Ivan Cristina, Cascione Luciano, Calin George A, Croce Carlo M, Colombatti Alfonso, Vecchione Andrea, Belletti Barbara, Baldassarre Gustavo
Division of Experimental Oncology 2, CRO, National Cancer Institute, Aviano, Italy.
Oncotarget. 2014 Mar 15;5(5):1185-97. doi: 10.18632/oncotarget.1803.
MicroRNAs (miRs) are a large class of small regulatory RNAs that function as nodes of signaling networks. This implicates that miRs expression has to be finely tuned, as observed during cell cycle progression. Here, using an expression profiling approach, we provide evidence that the CDK inhibitor p27Kip1 regulates miRs expression following cell cycle exit. By using wild type and p27KO cells harvested in different phases of the cell cycle we identified several miRs regulated by p27Kip1 during the G1 to S phase transition. Among these miRs, we identified miR-223 as a miR specifically upregulated by p27Kip1 in G1 arrested cells. Our data demonstrate that p27Kip1 regulated the expression of miR-223, via two distinct mechanisms. p27Kip1 directly stabilized mature miR-223 expression, acting as a RNA binding protein and it controlled E2F1 expression that, in turn, regulated miR-223 promoter activity. The resulting elevated miR-223 levels ultimately participated to arresting cell cycle progression following contact inhibition. Importantly, this mechanism of growth control was conserved in human cells and deranged in breast cancers. Here, we identify a novel and conserved function of p27Kip1 that, by modulating miR-223 expression, contributes to proper regulation of cell cycle exit following contact inhibition. Thus we propose a new role for miR-223 in the regulation of breast cancer progression.
微小RNA（miR）是一大类小的调节RNA，作为信号网络的节点发挥作用。这意味着miR的表达必须得到精细调控，正如在细胞周期进程中所观察到的那样。在此，我们采用表达谱分析方法，提供证据表明细胞周期蛋白依赖性激酶（CDK）抑制剂p27Kip1在细胞周期退出后调节miR的表达。通过使用在细胞周期不同阶段收获的野生型和p27基因敲除（KO）细胞，我们鉴定出了在G1期到S期转变过程中受p27Kip1调节的几种miR。在这些miR中，我们鉴定出miR - 223是在G1期停滞细胞中被p27Kip1特异性上调的一种miR。我们的数据表明，p27Kip1通过两种不同机制调节miR - 223的表达。p27Kip1作为一种RNA结合蛋白直接稳定成熟miR - 223的表达，并且它控制E2F1的表达，而E2F1反过来调节miR - 223启动子的活性。由此导致的miR - 223水平升高最终参与了接触抑制后细胞周期进程的停滞。重要的是，这种生长控制机制在人类细胞中是保守的，而在乳腺癌中则被打乱。在此，我们鉴定出p27Kip有一个新的保守功能，即通过调节miR - 223的表达，有助于在接触抑制后对细胞周期退出进行适当调控。因此，我们提出miR - 223在乳腺癌进展调控中具有新的作用。
