Yang Hushan, Henning Dale, Valdez Benigno C
Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA.
FEBS J. 2005 Aug;272(15):3788-802. doi: 10.1111/j.1742-4658.2005.04811.x.
RNA helicase II/Gu(alpha) is a multifunctional nucleolar protein involved in ribosomal RNA processing in Xenopus laevis oocytes and mammalian cells. Downregulation of Gu(alpha) using small interfering RNA (siRNA) in HeLa cells resulted in 80% inhibition of both 18S and 28S rRNA production. The mechanisms underlying this effect remain unclear. Here we show that in mammalian cells, Gu(alpha) physically interacts with ribosomal protein L4 (RPL4), a component of 60S ribosome large subunit. The ATPase activity of Gu(alpha) is important for this interaction and is also necessary for the function of Gu(alpha) in the production of both 18S and 28S rRNAs. Knocking down RPL4 expression using siRNA in mouse LAP3 cells inhibits the production of 47/45S, 32S, 28S, and 18S rRNAs. This inhibition is reversed by exogenous expression of wild-type human RPL4 protein but not the mutant form lacking Gu(alpha)-interacting motif. These observations have suggested that the function of Gu(alpha) in rRNA processing is at least partially dependent on its ability to interact with RPL4.
RNA解旋酶II/鸟苷酸结合蛋白α（Gu(α)）是一种多功能核仁蛋白，参与非洲爪蟾卵母细胞和哺乳动物细胞中的核糖体RNA加工。在HeLa细胞中使用小干扰RNA（siRNA）下调Gu(α)，导致18S和28S rRNA产生均受到80%的抑制。这种效应背后的机制仍不清楚。在此我们表明，在哺乳动物细胞中，Gu(α)与核糖体蛋白L4（RPL4）发生物理相互作用，RPL4是60S核糖体大亚基的一个组成部分。Gu(α)的ATP酶活性对这种相互作用很重要，并且对Gu(α)在18S和28S rRNA产生中的功能也是必需的。在小鼠LAP3细胞中使用siRNA敲低RPL4表达会抑制47/45S、32S、28S和18S rRNA的产生。这种抑制可通过野生型人RPL4蛋白的外源表达而逆转，但缺乏与Gu(α)相互作用基序的突变形式则不能。这些观察结果表明，Gu(α)在rRNA加工中的功能至少部分取决于其与RPL4相互作用的能力。
