Inositol hexakisphosphate and Gle1 activate the DEAD-box protein Dbp5 for nuclear mRNA export
Inositol hexakisphosphate and Gle1 activate the DEAD-box protein Dbp5 for nuclear mRNA export
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DOI：
10.1038/ncb1427
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发表时间：
2006-07-01
影响因子：
21.3
通讯作者：
Wente, Susan R.
中科院分区：
文献类型：
--
作者：
Alcazar-Roman, Abel R.;Tran, Elizabeth J.;Wente, Susan R.
核mRNA输出的调节对于真核基因的正确表达至关重要。在这个过程中的一个关键步骤是mRNA-核糖核蛋白颗粒（mRNP）的定向易位通过核孔复合物（NPC），嵌入在核蛋白1。我们之前在酿酒酵母中的研究确定了肌醇六磷酸（InsP（6））和NPC相关Gle 1在mRNA输出中的体内作用（2）。在这里，我们发现Gle 1和InsP（6）共同作用，刺激必需的DEAD盒蛋白Dbp 5的RNA依赖性ATP酶活性。DBP 5的过表达特异性地抑制了在InsP（6）产生和Gle 1定位中有缺陷的ipk 1 nup 42突变体的mRNA输出和生长缺陷。体外动力学分析表明，InsP（6）以Gle 1依赖的方式显著增加Dbp 5 ATP酶活性，并降低ATP酶半最大活性的有效RNA浓度。单独的Gle 1具有最小的影响。最大InsP（6）结合需要Dbp 5和Gle 1。有人认为Dbp 5需要未鉴定的辅因子（3，4）。我们现在提出Dbp 5在NPC中的激活需要Gle 1和InsP（6）。这将有助于在定向转运期间对mRNP蛋白质组成的重塑进行空间控制，并为动力转运循环提供能量。
Regulation of nuclear mRNA export is critical for proper eukaryotic gene expression. A key step in this process is the directional translocation of mRNA-ribonucleoprotein particles ( mRNPs) through nuclear pore complexes ( NPCs) that are embedded in the nuclear envelope1. Our previous studies in Saccharomyces cerevisiae defined an in vivo role for inositol hexakisphosphate ( InsP(6)) and NPC-associated Gle1 in mRNA export(2). Here, we show that Gle1 and InsP(6) act together to stimulate the RNA-dependent ATPase activity of the essential DEAD-box protein Dbp5. Overexpression of DBP5 specifically suppressed mRNA export and growth defects of an ipk1 nup42 mutant defective in InsP(6) production and Gle1 localization. In vitro kinetic analysis showed that InsP(6) significantly increased Dbp5 ATPase activity in a Gle1-dependent manner and lowered the effective RNA concentration for half-maximal ATPase activity. Gle1 alone had minimal effects. Maximal InsP(6) binding required both Dbp5 and Gle1. It has been suggested that Dbp5 requires unidentified cofactors(3, 4). We now propose that Dbp5 activation at NPCs requires Gle1 and InsP(6). This would facilitate spatial control of the remodelling of mRNP protein composition during directional transport and provide energy to power transport cycles.