The nucleolus is involved in mRNA export from the nucleus in fission yeast
The nucleolus is involved in mRNA export from the nucleus in fission yeast
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DOI：
10.1242/jcs.01155
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发表时间：
2004-06-15
影响因子：
4
通讯作者：
Tani, T
中科院分区：
文献类型：
--
作者：
Ideue, T;Azad, AK;Tani, T
为了阐明mRNA从细胞核输出的机制，我们分离了5个新的温度敏感突变体（ptr7至ptr11），它们在非允许温度下在粟酒裂殖酵母细胞核中积累poly（A）（+）RNA。其中，在编码DNA拓扑异构酶H的top2（+）基因中发现了ptr11突变。除了聚（A）1 RNA的核积累，ptr11表现出切割（细胞不合时宜的撕裂）表型在非允许的温度下，像以前分离的突变体ptr4。在这两个突变体中，胞质分裂发生在没有预先核分裂的情况下，导致未分裂的核被隔膜分裂。为了研究mRNA输出缺陷与在ptr4和pir11中观察到的切割表型之间的关系，我们分析了显示切割表型的11个其他突变体，发现所有这些测试的突变体在异常切割的核中积累poly（A）1 mRNA。有趣的是，只有在异常胞质分裂产生的无核仁细胞核中观察到poly（A）+ mRNA的核积累。nuc1、S.粟粒突变体在非允许温度下表现出核仁塌陷，将poly（A）+ mRNA捕获在核仁区域。在ptr11和nuc1中，从含内含子的TBP基因转录的mRNA显示核积累，但不从无内含子的TBP cDNA转录，这表明剪接和未剪接的TBP mRNA之间的出口途径不同。这些发现支持了酵母中mRNA的一个子集通过与核仁的短暂结合从细胞核输出的观点。
To elucidate the mechanism of mRNA export from the nucleus, we isolated five novel temperature-sensitive mutants (ptr7 to ptr11) that accumulate poly(A)(+) RNA in the nuclei at the nonpermissive temperature in Schizosaccharomyces pombe. Of those, the ptr11 mutation was found in the top2(+) gene encoding DNA topoisomerase H. In addition to the nuclear accumulation of poly(A)l RNA,ptr11 exhibited the cut (cell untimely torn) phenotype at the nonpermissive temperature, like the previously isolated mutants ptr4. In these two mutants, cytokinesis occurred without prior nuclear division, resulting in cleavage of the undivided nuclei by the septum. To investigate the relationship between mRNA export defects and the cut phenotype observed in ptr4 and pir11, we analyzed 11 other mutants displaying the cut phenotype and found that all these tested mutants accumulate poly(A)l mRNA in the aberrantly cleaved nuclei. Interestingly, nuclear accumulation of poly(A)+ mRNA was observed only in the anucleolate nuclei produced by aberrant cytokinesis. In addition, nuc1, the S. pombe mutant exhibiting a collapsed nucleolus, trapped poly(A)+ mRNA in the nucleolar region at the nonpermissive temperature. In ptr11 and nuc1, mRNA transcribed from the intron-containing TBP gene showed nuclear accumulation, but not transcripts from the intron-less TBP cDNA, suggesting that the export pathway differs between the spliced and unspliced TBP mRNAs. These findings support the notion that a subset of mRNAs in yeast is exported from the nucleus through transient association with the nucleolus.