Expression of the essential mRNA export factor Yra1p is autoregulated by a splicing-dependent mechanism
Expression of the essential mRNA export factor Yra1p is autoregulated by a splicing-dependent mechanism
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DOI：
10.1017/s1355838202020046
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发表时间：
2002-08-01
期刊：
影响因子：
4.5
通讯作者：
Guthrie, C
中科院分区：
文献类型：
--
作者：
Preker, PJ;Kim, KS;Guthrie, C
最近的证据支持前mRNA剪接和mRNA输出是机械耦合的观点。在后生动物中，这一过程似乎是由多组分复合物介导的，该复合物与外显子-外显子连接处上游的剪接RNA相关。其中一种成分（Aly/REF）在芽殖酵母酿酒酵母（Saccharomycescerevisiae）中有一种同源物，称为Yra 1 p。YRA 1基因是生长所必需的，也是mRNA输出所必需的。值得注意的是，YRA 1是酵母中仅有的含5%内含子的相似基因之一。此外，YRA 1内含子有几个不寻常的功能，是保守的其他芽殖酵母物种。以前，无内含子YRA 1的过表达被证明是有毒的。我们在这里表明，含内含子的基因的过表达导致未剪接的前mRNA水平增加，但Yra 1蛋白水平正常;相反，cDNA的表达导致蛋白水平增加和核多聚（A）（+）RNA的积累。另外两条证据表明Yra 1 p的表达是自动调节的：第一，质粒中过量Yra 1 p的表达降低了标记的染色体Yra 1 p的水平，第二，这种效应需要野生型蛋白。YRA 1内含子被其它S.酿酒酵母基因不能挽救无内含子YRA 1的显性负性生长缺陷。我们的结论是，Yra 1 p的水平是负自动调节的机制，涉及剪接其不寻常的内含子。严格控制Yra 1 p的水平可能对于结合前体mRNA剪接和mRNA输出的速率是必要的。
Recent evidence supports the idea that pre-mRNA splicing and mRNA export are mechanistically coupled. In metazoans, this process appears to be mediated by a multicomponent complex, which associates with the spliced RNA upstream of the exon-exon junction. One of these components (Aly/REF) has a homolog in the budding yeast Saccharomyces cerevisiae known as Yra1p. The YRA1 gene is essential for growth and required for mRNA export. Notably, YRA1 is one of the only similar to5% intron-containing genes in yeast. Moreover, the YRA1 intron has several unusual features and is conserved in other budding yeast species. Previously, overexpression of intronless YRA1 was shown to be toxic. We show here that overexpression of the intron-containing gene results in increased levels of unspliced pre-mRNA but normal levels of Yra1 protein; conversely, expression of the cDNA results in increased levels of protein and accumulation of nuclear poly(A)(+) RNA. Two additional lines of evidence suggest that expression of Yra1p is autoregulated: First, expression of excess Yra1p from a plasmid reduces the level of tagged, chromosomal Yra1p, and, second, this effect requires wild-type protein. Replacement of the YRA1 intron with that of other S. cerevisiae genes cannot rescue the dominant-negative growth defect of intronless YRA1. We conclude that the level of Yra1p is negatively autoregulated by a mechanism that involves splicing of its unusual intron. Tight control of the levels of Yra1p might be necessary to couple the rates of pre-mRNA splicing and mRNA export.