A nuclear import pathway for a protein involved in tRNA maturation.
A nuclear import pathway for a protein involved in tRNA maturation.
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DOI：
10.1083/jcb.139.7.1655
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发表时间：
1997-12-29
期刊：
影响因子：
--
通讯作者：
Blobel G
中科院分区：
文献类型：
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作者：
Rosenblum JS;Pemberton LF;Blobel G
有限数量的运输因子或核粘附素在细胞质和核质之间运送特定的底物。根据与已知核粘附素的有限序列相似性，我们确定酿酒酵母YDR395w/SXM1基因是一个潜在的核粘附素。我们从酵母胞浆中分离到Sxm1p，并与几种潜在的进口底物形成了复合体。这些底物包括人类自身抗原La的酵母同源物Lhp1p，最近被证明有助于Pre-tRNA的成熟，以及三种不同的核糖体蛋白，Rpl16p，Rpl25p和Rpl34p。进一步，我们证明了Lhp1p是由Sxm1p特定导入的。在Sxm1p缺失的情况下，Lhp1p错误定位于细胞质。Sxm1p和Lhp1p代表核粘附素和一种独特的核输入途径的同源底物，该途径操作于前tRNA成熟的主要途径的上游，而该途径本身就是野生型细胞中tRNA输出的上游。此外，通过与核糖体蛋白的结合，Sxm1p可能在协调核糖体生物发生和tRNA加工方面发挥作用。
A limited number of transport factors, or karyopherins, ferry particular substrates between the cytoplasm and nucleoplasm. We identified the Saccharomyces cerevisiae gene YDR395w/SXM1 as a potential karyopherin on the basis of limited sequence similarity to known karyopherins. From yeast cytosol, we isolated Sxm1p in complex with several potential import substrates. These substrates included Lhp1p, the yeast homologue of the human autoantigen La that has recently been shown to facilitate maturation of pre-tRNA, and three distinct ribosomal proteins, Rpl16p, Rpl25p, and Rpl34p. Further, we demonstrate that Lhp1p is specifically imported by Sxm1p. In the absence of Sxm1p, Lhp1p was mislocalized to the cytoplasm. Sxm1p and Lhp1p represent the karyopherin and a cognate substrate of a unique nuclear import pathway, one that operates upstream of a major pathway of pre-tRNA maturation, which itself is upstream of tRNA export in wild-type cells. In addition, through its association with ribosomal proteins, Sxm1p may have a role in coordinating ribosome biogenesis with tRNA processing.