The Chironomus tentans translation initiation factor elF4H is present in the nucleus but does not bind to mRNA until the mRNA reaches the cytoplasmic perinuclear region
The Chironomus tentans translation initiation factor elF4H is present in the nucleus but does not bind to mRNA until the mRNA reaches the cytoplasmic perinuclear region
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DOI：
10.1242/jcs.00766
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发表时间：
2003-11-15
影响因子：
4
通讯作者：
Wieslander, L
中科院分区：
文献类型：
--
作者：
Björk, P;Baurén, G;Wieslander, L
在细胞核中，mRNA的前体，pre-mRNAs，与大量蛋白质结合并被加工成mRNA-蛋白质复合物，mRNP。然后mRNP被输出到细胞质，mRNA被翻译成蛋白质。含有读框内提前终止密码子的mRNA在无义介导的mRNA降解过程中被识别和降解。这种mRNA监视也可能发生在细胞核中，并可能涉及翻译机制的组成部分。在细胞核中已经检测到几个翻译因子，但它们与细胞核中前mRNP和mRNP的动态蛋白质组成的功能关系尚不清楚。在细胞质中，Ct-eIF 4 H与多聚核糖体中的poly（A+）RNA相关。我们表明，一小部分的Ct-eIF 4 H进入细胞核。这部分是独立的转录水平。Ct-eIF 4 H不能在基因特异性pre-mRNP或mRNP中检测到，也不能在细胞核中的大量mRNP中检测到。我们的免疫电镜数据表明，Ct-eIF 4 H协会与mRNP在细胞质核周区，立即作为mRNP退出核孔复合物。
In the cell nucleus, precursors to mRNA, pre-mRNAs, associate with a large number of proteins and are processed to mRNA-protein complexes, mRNPs. The mRNPs are then exported to the cytoplasm and the mRNAs are translated into proteins. The mRNAs containing in-frame premature stop codons are recognized and degraded in the nonsense-mediated mRNA decay process. This mRNA surveillence may also occur in the nucleus and presumably involves components of the translation machinery. Several translation factors have been detected in the nucleus, but their functional relationship to the dynamic protein composition of pre-mRNPs and mRNPs in the nucleus is still unclear.Here, we have identified and characterized the translation initiation factor eIF4H in the dipteran Chironomus tentans. In the cytoplasm, Ct-eIF4H is associated with poly(A+) RNA in polysomes. We show that a minor fraction of Ct-eIF4H enters the nucleus. This fraction is independent on the level of transcription. Ct-eIF4H could not be detected in gene-specific pre-mRNPs or mRNPs, nor in bulk mRNPs in the nucleus. Our immunoelectron microscopy data suggest that Ct-eIF4H associates with mRNP in the cytoplasmic perinuclear region, immediately as the mRNP exits from the nuclear pore complex.