Yuan Y, Li D M, Sun H
Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
J Biol Chem. 1998 Aug 7;273(32):20347-53. doi: 10.1074/jbc.273.32.20347.
Protein tyrosine phosphatases are involved in the regulation of important cellular processes such as signal transduction, cell cycle progression, and tumor suppression. Here we report the cloning and characterization of PIR1, a novel member in the dual-specificity phosphatase subfamily of the protein tyrosine phosphatases. PIR1 also contains two stretches of arginine-rich sequences. We have shown that the recombinant PIR1 protein possessed an intrinsic phosphatase activity on phosphotyrosine-containing substrate. A unique feature of this phosphatase is that it binds directly to RNA in vitro with high affinity. In addition, we have found that PIR1 interacted with splicing factors 9G8 and SRp30C, possibly through an RNA intermediate during a yeast two-hybrid screen. PIR1 exhibited a nuclear-staining pattern that was sensitive to RNase A, but not to DNase I, suggesting that PIR1 in the cells are associated with RNA and/or ribonucleoprotein particles. Furthermore, a fraction of PIR1 showed a speckle-staining pattern that superimposed with that of the splicing factor, SC35. Taken together, our data suggest that PIR1 is a novel phosphatase that may participate in nuclear mRNA metabolism.
蛋白质酪氨酸磷酸酶参与重要细胞过程的调控，如信号转导、细胞周期进程和肿瘤抑制。在此，我们报告了PIR1的克隆与特性分析，PIR1是蛋白质酪氨酸磷酸酶双特异性磷酸酶亚家族中的一个新成员。PIR1还包含两段富含精氨酸的序列。我们已表明，重组PIR1蛋白对含磷酸酪氨酸的底物具有内在磷酸酶活性。这种磷酸酶的一个独特特征是它在体外能以高亲和力直接与RNA结合。此外，我们发现在酵母双杂交筛选中，PIR1可能通过RNA中间体与剪接因子9G8和SRp30C相互作用。PIR1呈现出对核糖核酸酶A敏感但对脱氧核糖核酸酶I不敏感的核染色模式，这表明细胞中的PIR1与RNA和/或核糖核蛋白颗粒相关。此外，一部分PIR1呈现出与剪接因子SC35重叠的斑点状染色模式。综上所述，我们的数据表明PIR1是一种可能参与核mRNA代谢的新型磷酸酶。
