Kullmann Michael, Göpfert Ulrich, Siewe Basile, Hengst Ludger
Max-Planck-Institute of Biochemistry, Am Klopferspitz 18a, D-82152 Martinsried, Germany.
Genes Dev. 2002 Dec 1;16(23):3087-99. doi: 10.1101/gad.248902.
p27Kip1 restrains cell proliferation by binding to and inhibiting cyclin-dependent kinases. To investigate the mechanisms of p27 translational regulation, we isolated a complete p27 cDNA and identified an internal ribosomal entry site (IRES) located in its 5'UTR. The IRES allows for efficient p27 translation under conditions where cap-dependent translation is reduced. Searching for possible regulators of IRES activity we have identified the neuronal ELAV protein HuD as a specific binding factor of the p27 5'UTR. Increased expression of HuD or the ubiquitously expressed HuR protein specifically inhibits p27 translation and p27 IRES activity. Consistent with an inhibitory role of Hu proteins in p27 translation, siRNA mediated knockdown of HuR induced endogenous p27 protein levels as well as IRES-mediated reporter translation and leads to cell cycle arrest in G1.
p27Kip1 通过结合并抑制细胞周期蛋白依赖性激酶来抑制细胞增殖。为了研究 p27 翻译调控的机制，我们分离出了完整的 p27 cDNA，并鉴定出位于其 5'UTR 的一个内部核糖体进入位点（IRES）。该 IRES 能够在帽依赖性翻译减少的条件下实现 p27 的高效翻译。在寻找 IRES 活性的可能调节因子时，我们鉴定出神经元 ELAV 蛋白 HuD 是 p27 5'UTR 的特异性结合因子。HuD 或普遍表达的 HuR 蛋白的表达增加会特异性抑制 p27 翻译和 p27 IRES 活性。与 Hu 蛋白在 p27 翻译中的抑制作用一致，siRNA 介导的 HuR 敲低可诱导内源性 p27 蛋白水平以及 IRES 介导的报告基因翻译，并导致细胞周期在 G1 期停滞。
