The mRNA export factor Dbp5 is associated with Balbiani ring mRNP from gene to cytoplasm
The mRNA export factor Dbp5 is associated with Balbiani ring mRNP from gene to cytoplasm
复制标题
mRNA输出因子Dbp5与Balbiani环mRNP从基因到细胞质相关
作者：
Jian Zhao;Shaobo Jin;B. Björkroth;L. Wieslander;B. Daneholt
DEAD BOX RNA解旋酶Dbp5是核质转运mRNP复合体所必需的。Dbp5主要存在于细胞质中，并在核孔复合体(NPC)的细胞质一侧富含，表明它在mRNP输出的晚期起作用。在这里，我们可视化了一个特定的mRNP颗粒，即Balbiani环mRNP在双翅目摇蚊中的组装和运输，并表明触须摇蚊中的Dbp5同系物Ct-Dbp5与前mRNP结合，并伴随着mRNP进入并通过核孔进入细胞质。我们还证明，当核输出mRNA被抑制时，Ct-Dbp5在细胞核中积聚，并从NPC中部分消失。Ct-Dbp5沿着从核孔延伸到细胞质的mRNP原纤维存在，这一事实支持了Ct-Dbp5参与翻译前mRNP重组的观点。最后，将输出因子Dbp5添加到不断增长的转录本中，突显了共转录加载过程在决定mRNA命运中的重要性。
The DEAD box RNA helicase Dbp5 is essential for nucleocytoplasmic transport of mRNA–protein (mRNP) complexes. Dbp5 is present mainly in the cytoplasm and is enriched at the cytoplasmic side of nuclear pore complexes (NPCs), suggesting that it acts in the late part of mRNP export. Here, we visualize the assembly and transport of a specific mRNP particle, the Balbiani ring mRNP in the dipteran Chironomus tentans, and show that a Dbp5 homologue in C.tentans, Ct‐Dbp5, binds to pre‐mRNP co‐transcriptionally and accompanies the mRNP to and through the nuclear pores and into the cytoplasm. We also demonstrate that Ct‐Dbp5 accumulates in the nucleus and partly disappears from the NPC when nuclear export of mRNA is inhibited. The fact that Ct‐Dbp5 is present along the exiting mRNP fibril extending from the nuclear pore into the cytoplasm supports the view that Ct‐Dbp5 is involved in restructuring the mRNP prior to translation. Finally, the addition of the export factor Dbp5 to the growing transcript highlights the importance of the co‐transcriptional loading process in determining the fate of mRNA.