Izaurralde E, Mattaj I W
European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
Semin Cell Biol. 1992 Aug;3(4):279-88. doi: 10.1016/1043-4682(92)90029-u.
The transport out of the nucleus of RNAs transcribed by RNA polymerase II (U snRNAs and mRNAs) has not been extensively studied. Basic questions, such as whether export requires association of the RNA with specific proteins, are not yet definitively answered. Nevertheless, recent progress in this area has been significant. Sequence or structural features of RNAs which are either required for export or which result in nuclear retention have been defined. These are presumed to interact with components of the transport machinery or with anchoring nuclear factors respectively. The unexplained dependence of the transport of certain mRNAs on either intervening sequences or for transcription from specific promoters suggests that RNAs may have to pass through different intranuclear compartments before export. Studies of the import of RNAs from the cytoplasm has revealed that different classes of nuclear localization signals exist, and protein components of viral RNPs that appear to determine the direction in which they move through the nuclear envelope have been identified.
由RNA聚合酶II转录的RNA（U小核RNA和信使RNA）从细胞核输出的过程尚未得到广泛研究。一些基本问题，比如RNA输出是否需要与特定蛋白质结合，仍未得到明确解答。然而，该领域最近取得了重大进展。已确定了RNA输出所需的序列或结构特征，以及导致RNA滞留细胞核的序列或结构特征。据推测，它们分别与转运机制的组分或与锚定核因子相互作用。某些信使RNA的输出对居间序列或特定启动子转录的莫名依赖表明，RNA在输出之前可能必须穿过不同的核内区室。对细胞质RNA输入的研究表明，存在不同类别的核定位信号，并且已鉴定出似乎决定病毒核糖核蛋白通过核膜移动方向的蛋白质组分。
