Department of Cell Biology, University of Alberta, Edmonton, Canada.
Biochemistry, Molecular, Cellular and Developmental Biology Graduate Group, University of California, Davis, Davis, United States.
Elife. 2019 Aug 27;8:e48410. doi: 10.7554/eLife.48410.
Dbp5 is an essential DEAD-box protein that mediates nuclear mRNP export. Dbp5 also shuttles between nuclear and cytoplasmic compartments with reported roles in transcription, ribosomal subunit export, and translation; however, the mechanism(s) by which nucleocytoplasmic transport occurs and how Dbp5 specifically contributes to each of these processes remains unclear. Towards understanding the functions and transport of Dbp5 in , alanine scanning mutagenesis was used to generate point mutants at all possible residues within a GFP-Dbp5 reporter. Characterization of the 456 viable mutants led to the identification of an N-terminal Xpo1-dependent nuclear export signal in Dbp5, in addition to other separation-of-function alleles, which together provide evidence that Dbp5 nuclear shuttling is not essential for mRNP export. Rather, disruptions in Dbp5 nucleocytoplasmic transport result in tRNA export defects, including changes in tRNA shuttling dynamics during recovery from nutrient stress.
Dbp5 是一种必需的 DEAD 盒蛋白，可介导核 mRNP 输出。Dbp5 还在核质和细胞质之间穿梭，据报道在转录、核糖体亚基输出和翻译中具有作用；然而，核质转运发生的机制以及 Dbp5 如何特异性地促进这些过程仍不清楚。为了了解 Dbp5 在 中的功能和运输，采用丙氨酸扫描突变的方法在 GFP-Dbp5 报告基因的所有可能残基上生成点突变。对 456 个存活突变体的特征分析导致鉴定出 Dbp5 中的 Xpo1 依赖性核输出信号，此外还有其他分离功能等位基因，这些共同提供了证据表明 Dbp5 的核穿梭对于 mRNP 输出不是必需的。相反，Dbp5 的核质转运中断会导致 tRNA 输出缺陷，包括在从营养胁迫中恢复时 tRNA 穿梭动力学的变化。
