YEAST RNA VIROLOGY

我们已经描述了两种双链RNA病毒(L A和L BC)和两个单链RNA复制子(20S RNA和23S RNA)。 酿酒酵母。MdsRNA是L A的卫星 对杀手毒素进行编码。我们发现了7个染色体基因， SKI1、2、3、4、6、7和8，通过它们阻止这些复制的能力 对酵母细胞产生致病作用。这四种RNA 复制子都制造无上限的mRNAs，并且缺乏3‘聚(A)结构。 SKI1是一种外切核糖核酸酶，专用于未封顶的mRNAs，而 我们发现了SKI2、SKI3、SKI6、SKI7和SKI8基因 产物阻止非聚(A)mRNAs的翻译。我们展示了 Ski2p是一种RNA解旋酶，Ski6p与tRNA- 处理核糖核酸酶，Ski7p类似于翻译因子EF1*。 我们发现，20个染色体基因的突变会导致 在60S核糖体亚基中缺失M dsRNA。这些 突变被SKI突变抑制，而不是恢复 60S亚基缺失。我们建议SKI2、SKI3和 SKI8阻断非Poly(A)mRNA的翻译 影响60S亚基与核糖体相互作用的核糖体生物发生 信使核糖核酸的3‘多聚(A)结构。我们现在已经克隆了 MAK21，发现它类似于人类CAATT盒结合 已知的调节Hsp70转录的蛋白质。而酵母菌 Mak21p不调控同源酵母Hsp70，它是 对增长至关重要，因为它是60年代特别需要的 核糖体亚基生物发生。模型RNA的电穿孔研究 表明mak21-1突变体在翻译过程中受到了特定的损害 缺乏5‘帽或3’聚(A)结构的mRNAs，解释 他们对病毒mRNAs的翻译很差，也缺乏这些 结构。

We have described two dsRNA viruses (L A and L BC) and two ssRNA replicons (20S RNA and 23S RNA) in the yeast Saccharomyces cerevisiae. M dsRNA is a satellite of L A encoding the killer toxin. We discovered 7 chromosomal genes, SKI1, 2, 3, 4, 6, 7, and 8, by their ability to prevent these replicons from causing pathogenicity to yeast cells. These four RNA replicons all make uncapped mRNAs and lack a 3' poly(A)structure. SKI1 is an exoribonuclease specific for uncapped mRNAs, while we showed that the SKI2, SKI3, SKI6, SKI7 and SKI8 gene products block the translation of non-poly(A) mRNAs. We showed that Ski2p is an RNA helicase, Ski6p has homology to a tRNA - processing RNAse, and Ski7p is similar to translation factor EF1*. We showed that mutations in 20 chromosomal genes resulting in loss of M dsRNA are deficient in 60S ribosomal subunits. These mutations are suppressed by ski mutations without restoration of the 60S subunit deficiency. We proposed that SKI2, SKI3 and SKI8 block translation of non-poly(A) mRNA by an effect on ribosome biogenesis affecting the interaction of 60S subunits with the 3' poly(A) structure of the mRNA. We have now cloned MAK21 and found it similar to a human CAATT box binding protein known to regulate Hsp70 transcription. While yeast Mak21p does not regulate the homologous yeast Hsp70, it is essential for growth because it is required specifically for 60S ribosomal subunit biogenesis. Electroporation of model mRNAs shows that mak21-1 mutants are specifically impaired in translation of mRNAs lacking the 5' cap or 3' poly(A) structures, explaining their poor translation of viral mRNAs which also lack these structures.