YEAST RNA VIROLOGY

我们在酿酒酵母中发现了两种双链RNA病毒(L-A和L-BC)和两种单链RNA复制子(20S和23S)。MdsRNA是L-A的一个卫星，编码杀手毒素。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子对酵母细胞致病的能力。这四个RNA复制子都产生无帽的mRNAs，并且缺乏3聚(A)结构。SKI1是一种外切核糖核酸酶，我们发现SKI2、SKI3、SKI6、SKI7和SKI8基因产物可以阻断非Poly(A)mRNAs的翻译。我们发现Ski2p是一种RNA解旋酶，Ski6p与tRNA加工RNase同源，Ski7p与翻译因子EF1pha相似。我们发现，导致M dsRNA丢失的20个染色体基因的突变在60S核糖体亚基中存在缺陷。这些突变被SKI突变抑制，但不能修复60S亚基缺失。我们认为Ski2、SKI3和SKI8通过影响核糖体的生物发生，影响60S亚基与mRNA3聚(A)结构的相互作用，从而阻断非Poly(A)mRNAs的翻译。我们发现ski7突变增加了电穿孔非Polya mRNAs的翻译起始速度和翻译持续时间，表明该基因对翻译和mRNA稳定性都有影响。对mRNA稳定性的影响可能次于对翻译的影响。Ski7缺失突变体也对潮霉素过敏，这再次表明了对翻译的影响。Ski7p的过表达降低了非Polya mRNAs的表达，并治愈了M dsRNA。我们现在正在研究另一个与Ski2同源的酵母基因。我们发现，该基因的突变也特异性地降低了非Polya mRNAs的表达。我们正在研究这种作用的机制以及该基因与Ski2的相互作用。-双链RNA，病毒，复制，组装，酿酒酵母，聚(A)，翻译，SKI6，SKI7，SKI2，SKI3，SKI8，FUN12

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 EF1alpha. 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 find that a ski7 mutation increases both the initial rate and the duration of translation of electroporated non-polyA mRNAs, indicating effects of the gene on both translation and mRNA stability. The effect on mRNA stability may be secondary to the effect on translation. The ski7 deletion mutant is also hypersensitive to hygromycin, again suggesting an effect on translation. Overexpression of Ski7p lowers expression of non-polyA mRNAs and cures M dsRNA. We are now studying another yeast gene homologous to SKI2. We find that mutations of this gene also specifically derepress expression of non-polyA mRNAs. We are studying the mechanism of this effect and the interaction of this gene with SKI2. - double-stranded RNA, virus, replication, assembly, Saccharomyces cerevisiae, poly(A), translation, SKI6, SKI7, SKI2, SKI3, SKI8, FUN12