Patterson B, Guthrie C
Cell. 1987 Jun 5;49(5):613-24. doi: 10.1016/0092-8674(87)90537-x.
Yeast contains at least 24 snRNAs, many of which are dispensable for viability. We recently demonstrated that a small subset of these RNAs has a functional binding site for the Sm antigen, a hallmark of metazoan snRNAs involved in mRNA processing. Here we show that one of these snRNAs, snR7, is required for growth. To determine the biochemical basis of lethality in cells lacking snR7, we engineered the conditional synthesis of snR7 by fusing the snRNA coding sequences to the yeast GAL1 control region. Cells depleted for the SNR7 gene product by growth on glucose for five generations show marked accumulation of unspliced mRNA precursors from the four intron-containing genes tested. In some cases, intron-exon 2 lariats also accumulate. We have identified a 70 nucleotide domain within snR7 with limited sequence-specific but striking structural homology to the mammalian snRNA U5. We conclude that mRNA splicing in yeast requires the function of a U5-like snRNA.
酵母至少含有24种小核仁RNA（snRNAs），其中许多对于细胞存活并非必需。我们最近证明，这些RNA中的一小部分具有与Sm抗原的功能性结合位点，Sm抗原是参与mRNA加工的后生动物snRNAs的一个标志。在此我们表明，其中一种snRNA，即snR7，是细胞生长所必需的。为了确定缺乏snR7的细胞中致死性的生化基础，我们通过将snRNA编码序列与酵母GAL1控制区融合来构建snR7的条件性合成。在葡萄糖上生长五代使SNR7基因产物耗尽的细胞，显示出所测试的四个含内含子基因的未剪接mRNA前体明显积累。在某些情况下，内含子 - 外显子2套索结构也会积累。我们在snR7内鉴定出一个70个核苷酸的结构域，其与哺乳动物snRNA U5具有有限的序列特异性但显著的结构同源性。我们得出结论，酵母中的mRNA剪接需要一种类似U5的snRNA的功能。
