Allemand Eric, Guil Sònia, Myers Michael, Moscat Jorge, Cáceres Javier F, Krainer Adrian R
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
Proc Natl Acad Sci U S A. 2005 Mar 8;102(10):3605-10. doi: 10.1073/pnas.0409889102. Epub 2005 Feb 28.
Heterogeneous nuclear ribonucleoprotein (hnRNP) A1 is an alternative splicing factor that is mainly nuclear, although it shuttles rapidly between nuclear and cytoplasmic compartments. Cells stressed by osmotic shock (OSM) activate the mitogen-activated protein kinase kinase(3/6)-p38 signaling pathway, which in turn results in accumulation of hnRNP A1 in the cytoplasm. This effect modulates alternative splicing regulation in vivo and correlates with increased hnRNP A1 phosphorylation. We have characterized the molecular mechanism involved in the cytoplasmic accumulation of hnRNP A1 in NIH 3T3 cells subjected to OSM. This treatment results in serine-specific phosphorylation within a C-terminal peptide, dubbed the "F-peptide," which is adjacent to the M9 motif that mediates bidirectional transport of hnRNP A1. Analysis of mutants in which the F-peptide serines were replaced by aspartic acids or alanines showed that F-peptide phosphorylation is required for the subcellular redistribution of hnRNP A1 in cells subjected to OSM. Furthermore, F-peptide phosphorylation modulates the interaction of hnRNP A1 with transportin Trn1. Our findings suggest that the phosphorylation of F-peptide by cell-signaling pathways regulates the rate of hnRNP A1 nuclear import.
不均一核核糖核蛋白（hnRNP）A1是一种可变剪接因子，虽然它在核和细胞质区室之间快速穿梭，但主要位于细胞核中。受到渗透休克（OSM）应激的细胞会激活丝裂原活化蛋白激酶激酶（3/6）-p38信号通路，进而导致hnRNP A1在细胞质中积累。这种效应在体内调节可变剪接调控，并与hnRNP A1磷酸化增加相关。我们已经阐明了在经受OSM的NIH 3T3细胞中，hnRNP A1在细胞质中积累所涉及的分子机制。这种处理导致在一个称为“F肽”的C末端肽内发生丝氨酸特异性磷酸化，该肽与介导hnRNP A1双向转运的M9基序相邻。对F肽丝氨酸被天冬氨酸或丙氨酸取代的突变体的分析表明，F肽磷酸化是经受OSM的细胞中hnRNP A1亚细胞重新分布所必需的。此外，F肽磷酸化调节hnRNP A1与转运蛋白Trn1的相互作用。我们的研究结果表明，细胞信号通路对F肽的磷酸化调节了hnRNP A1核输入的速率。
