Definition of a consensus transportin-specific nucleocytoplasmic transport signal
Definition of a consensus transportin-specific nucleocytoplasmic transport signal
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DOI：
10.1074/jbc.274.14.9771
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发表时间：
1999-04-02
影响因子：
4.8
通讯作者：
Cullen, BR
中科院分区：
文献类型：
--
作者：
Bogerd, HP;Benson, RE;Cullen, BR
Ran的GTP结合形式的低细胞质和高细胞核浓度为核蛋白的输入和输出提供了方向性。进口和出口因素直接结合RanGTP，但这种相互作用产生相反的效果;在前者的情况下，RanGTP结合诱导核货物释放，而在后者，RanGTP结合诱导核货物组装。因此，预测核输入和输出受体及其蛋白质识别位点是不同的。尽管如此，已经报道了与存在于异质核核糖核蛋白A1中的38个氨基酸的M9序列相似的M9序列作为核定位信号和核输出信号，即使只有一种蛋白质，即核输入因子转运蛋白，已经显示直接结合M9。我们已经使用突变随机化的组合，然后选择转运蛋白结合，以彻底定义M9中对体内转运蛋白结合至关重要的氨基酸。正如预期的那样，所得的类似于12个氨基酸的转运蛋白结合共有序列也预测了核定位信号活性。然而，令人惊讶的是，这种广泛的突变分析未能剖析M9核定位信号和核输出信号功能。然而，转运蛋白似乎不太可能是M9输出受体，因为RanGTP不仅可以在体外阻断转运蛋白与M9的结合，而且可以在体内细胞核中阻断转运蛋白与M9的结合。因此，该分析预测存在与转运蛋白不同的核输出受体，但其在异质核核糖核蛋白A1上具有共同的蛋白结合位点。
The low cytoplasmic and high nuclear concentration of the GTP-bound form of Ran provides directionality for both nuclear protein import and export. Both import and export factors bind RanGTP directly, yet this interaction produces opposite effects; in the former case, RanGTP binding induces nuclear cargo release, whereas in the latter, RanGTP binding induces nuclear cargo assembly. Therefore, nuclear import and export receptors and their protein recognition sites are predicted to be distinct. Nevertheless, the similar to 38-amino acid M9 sequence present in heterogeneous nuclear ribonucleoprotein Al has been reported to serve as both a nuclear localization signal and a nuclear export signal, even though only one protein, the nuclear import factor transportin, has been shown to bind M9 directly. We have used a combination of mutational randomization followed by selection for transportin binding to exhaustively define amino acids in M9 that are critical for transportin binding in vivo, As expected, the resultant similar to 12-amino acid transportin-binding consensus sequence is also predictive of nuclear localization signal activity. Surprisingly, however, this extensive mutational analysis failed to dissect M9 nuclear localization signal and nuclear export signal function. Nevertheless, transportin appears unlikely to be the M9 export receptor, as RanGTP can be shown to block M9 binding by transportin not only in vitro, but also in the nucleus in vivo, This analysis therefore predicts the existence of a nuclear export receptor distinct from transportin that nevertheless shares a common protein-binding site on heterogeneous nuclear ribonucleoprotein A1.