Li Jiaxu, Kinoshita Toshinori, Pandey Sona, Ng Carl K-Y, Gygi Steven P, Shimazaki Ken-ichiro, Assmann Sarah M
Biology Department, The Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania 16802, USA.
Nature. 2002 Aug 15;418(6899):793-7. doi: 10.1038/nature00936.
Protein kinases are involved in stress signalling in both plant and animal systems. The hormone abscisic acid mediates the responses of plants to stresses such as drought, salinity and cold. Abscisic-acid-activated protein kinase (AAPK -- found in guard cells, which control stomatal pores -- has been shown to regulate plasma membrane ion channels. Here we show that AAPK-interacting protein 1 (AKIP1), with sequence homology to heterogeneous nuclear RNA-binding protein A/B, is a substrate of AAPK. AAPK-dependent phosphorylation is required for the interaction of AKIP1 with messenger RNA that encodes dehydrin, a protein implicated in cell protection under stress conditions. AAPK and AKIP1 are present in the guard-cell nucleus, and in vivo treatment of such cells with abscisic acid enhances the partitioning of AKIP1 into subnuclear foci which are reminiscent of nuclear speckles. These results show that phosphorylation-regulated RNA target discrimination by heterogeneous nuclear RNA-binding proteins may be a general phenomenon in eukaryotes, and implicate a plant hormone in the regulation of protein dynamics during rapid subnuclear reorganization.
蛋白激酶参与植物和动物系统中的应激信号传导。激素脱落酸介导植物对干旱、盐度和寒冷等胁迫的反应。脱落酸激活蛋白激酶（AAPK——存在于控制气孔的保卫细胞中——已被证明可调节质膜离子通道。我们在此表明，与不均一核RNA结合蛋白A/B具有序列同源性的AAPK相互作用蛋白1（AKIP1）是AAPK的底物。AKIP1与编码脱水素的信使RNA相互作用需要AAPK依赖性磷酸化，脱水素是一种在胁迫条件下参与细胞保护的蛋白质。AAPK和AKIP1存在于保卫细胞核中，用脱落酸对这些细胞进行体内处理可增强AKIP1向类似于核斑点的亚核灶的分配。这些结果表明，不均一核RNA结合蛋白的磷酸化调节的RNA靶标识别可能是真核生物中的普遍现象，并表明一种植物激素在快速亚核重组过程中对蛋白质动态的调节作用。
