Henry Michael F, Mandel Daniel, Routson Valerie, Henry Pamela A
Department of Molecular Biology, University of Medicine and Dentistry, New Jersey School of Osteopathic Medicine, Stratford, New Jersey 08084, USA.
Mol Biol Cell. 2003 Sep;14(9):3929-41. doi: 10.1091/mbc.e03-01-0854. Epub 2003 May 29.
The Hrp1/Nab4 shuttling protein belongs to a family of RNA binding proteins that bind to nascent RNA polymerase II transcripts and form hnRNP complexes. Members of this family function in a staggering array of cellular activities, ranging from transcription and pre-mRNA processing in the nucleus to cytoplasmic mRNA translation and turnover. It has recently been recognized that the yeast stress response can include alterations in hnRNP-mediated mRNA export. We now report that the steady-state localization of Hrp1p rapidly shifts from the nucleus to the cytoplasm in response to osmotic stress. In contrast to a general stress response resulting in a transient relocation, Hrp1p redistribution is specific to hyperosmotic stress and is only reversed after stress removal. Hrp1p relocalization requires both the CRM1/XPO1 exportin and the FPS1 glycerol transporter genes but is independent of ongoing RNA transcription and protein arginine methylation. However, mutations in the high osmolarity glycerol and protein kinase C osmosensing pathways do not impact the Hrp1p hyperosmotic response. We present a working model for the cytoplasmic accumulation of Hrp1 and discuss the implications of this relocalization on Hrp1p function.
穿梭蛋白Hrp1/Nab4属于一类RNA结合蛋白家族，它们与新生的RNA聚合酶II转录本结合并形成核不均一核糖核蛋白（hnRNP）复合物。该家族成员在一系列惊人的细胞活动中发挥作用，从细胞核中的转录和前体mRNA加工到细胞质中的mRNA翻译和周转。最近人们认识到，酵母应激反应可能包括hnRNP介导的mRNA输出的改变。我们现在报告，响应渗透胁迫，Hrp1p的稳态定位迅速从细胞核转移到细胞质。与导致短暂重新定位的一般应激反应不同，Hrp1p的重新分布对高渗胁迫具有特异性，并且仅在胁迫消除后才会逆转。Hrp1p的重新定位需要CRM1/XPO1输出蛋白和FPS1甘油转运蛋白基因，但与正在进行的RNA转录和蛋白质精氨酸甲基化无关。然而，高渗甘油和蛋白激酶C渗透压感应途径中的突变不会影响Hrp1p的高渗反应。我们提出了一个Hrp1在细胞质中积累的工作模型，并讨论了这种重新定位对Hrp1p功能的影响。
