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首页> 外文期刊>Molecular and Cellular Biology >Nuclear RNase MRP is required for correct processing of pre-5.8S rRNA in Saccharomyces cerevisiae.
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Nuclear RNase MRP is required for correct processing of pre-5.8S rRNA in Saccharomyces cerevisiae.

机译：核糖核酸酶MRP是正确处理啤酒酵母中5.8S之前的rRNA所必需的。

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RNase MRP is a site-specific ribonucleoprotein endoribonuclease that cleaves RNA from the mitochondrial origin of replication in a manner consistent with a role in priming leading-strand DNA synthesis. Despite the fact that the only known RNA substrate for this enzyme is complementary to mitochondrial DNA, the majority of the RNase MRP activity in a cell is found in the nucleus. The recent characterization of this activity in Saccharomyces cerevisiae and subsequent cloning of the gene coding for the RNA subunit of the yeast enzyme have enabled a genetic approach to the identification of a nuclear role for this ribonuclease. Since the gene for the RNA component of RNase MRP, NME1, is essential in yeast cells and RNase MRP in mammalian cells appears to be localized to nucleoli within the nucleus, we utilized both regulated expression and temperature-conditional mutations of NME1 to assay for a possible effect on rRNA processing. Depletion of the RNA component of the enzyme was accomplished by using the glucose-repressed GAL1 promoter. Shortly after the shift to glucose, the RNA component of the enzyme was found to be depleted severely, and rRNA processing was found to be normal at all sites except the B1 processing site. The B1 site, at the 5' end of the mature 5.8S rRNA, is actually composed of two cleavage sites 7 nucleotides apart. This cleavage normally generates two species of 5.8S rRNA at a ratio of 10:1 (small to large) in most eukaryotes. After RNase MRP depletion, yeast cells were found to have almost exclusively the larger species of 5.8S rRNA. In addition, an aberrant 309-nucleotide precursor that stretched from the A2 to E processing sites of rRNA accumulated in these cells. Temperature-conditional mutations in the RNase MRP RNA gene gave an identical phenotype.Translation in yeast cells depleted of the smaller 5.8S rRNA was found to remain robust, suggesting a possible function for two 5.8S rRNAs in the regulated translation of select messages. These results are consistent with RNase MRP playing a role in a late step of rRNA processing. The data also indicate a requirement for having the smaller form of 5.8S rRNA, and they argue for processing at the B1 position being composed of two separate cleavage events catalyzed by two different activities.
机译：RNase MRP是一种位点特异性核糖核酸蛋白核糖核酸内切酶，可从线粒体复制起点切割RNA，其方式与引发前导链DNA合成的作用一致。尽管事实上该酶的唯一已知RNA底物与线粒体DNA互补，但细胞核中的大多数RNase MRP活性都在细胞核中发现。最近在酿酒酵母中对该活性的表征以及随后的酵母酶RNA亚基编码基因的克隆，已经为鉴定这种核糖核酸酶的核作用提供了一种遗传方法。由于RNase MRP RNA成分的基因NME1在酵母细胞中是必不可少的，而哺乳动物细胞中的RNase MRP似乎位于核内的核仁，因此我们利用NME1的调控表达和温度条件突变来检测可能对rRNA加工产生影响。通过使用葡萄糖抑制的GAL1启动子来完成酶RNA成分的消耗。转变为葡萄糖后不久，发现该酶的RNA成分严重枯竭，并且发现除B1加工位点以外的所有位点，rRNA加工均正常。 B1位点位于成熟的5.8S rRNA的5'端，实际上是由两个7个核苷酸间隔的切割位点组成。这种裂解通常会在大多数真核生物中以10：1（小到大）的比率生成两种5.8S rRNA。 RNase MRP耗尽后，发现酵母细胞几乎只具有更大的5.8S rRNA。此外，从rRNA的A2到E加工位点延伸的异常309核苷酸前体积聚在这些细胞中。 RNase MRP RNA基因中的温度条件突变表现出相同的表型。发现在耗竭较小的5.8S rRNA的酵母细胞中，翻译仍然保持稳健，表明两个5.8S rRNA在选择信息的调控翻译中可能发挥作用。这些结果与RNase MRP在rRNA加工的后期发挥作用相一致。数据还表明需要具有更小形式的5.8S rRNA，并且他们争辩说在B1位置的加工由两个不同的活性催化的两个独立的切割事件组成。

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