BIOSYNTHESIS OF RNAS

尽管在许多实验室进行了密集的研究，但我们对 分子机制规定了准确和有效的剪接 含有内含子的mrna核转录本仅有轻微进展 超越现象学。中的其他步骤也是如此。 消息的成熟，包括3‘末端的产生和 多聚腺苷酸化。最近，一个由六个小团体组成的团体引起了人们的注意 核RNA(SnRNAs)，其非凡的结构保守性， 再加上各种间接证据，表明他们 真核基因中功能保守步骤的参与 表情。例如，假设U1 RNA参与内含子的去除 通过对剪接连接处的保守序列进行互补(S)。 因为在高等学府中缺乏可管理的实验系统 对于真核生物来说，这些假说还没有得到严格的检验。我们建议 利用酵母中独特的强大基因技术来 实现这些目标。 我们正在采用两种相辅相成的战略。第一个利用我们的 酿酒酵母中存在单链RNA的最新证据 由单拷贝基因编码；这使我们能够执行最终的测试 这些模型通过分析空等位基因和条件等位基因的结果 在这些基因中的每一个。此外，外源抑制子的分离 将识别与这些突变相互作用的细胞成分 SnRNAs；这些应该包括SnRNP蛋白，以及潜在的 “靶”RNA：前信使核糖核酸的底物。我们的第二种方法是 我们最近发现的突变型5‘端剪接接头的优势 酵母基因内含子。在这种情况下，分离外源基因的能力 抑制者应该允许对RNA的“Ul指南模型”进行直接测试 拼接

Despite intensive study in numerous laboratories, our understanding of the molecular mechanisms which specify the accurate and efficient splicing of intron-containing mRNA nuclear transcripts has progressed only slightly beyond the phenomenological. The same is true for other steps in the maturation of messages, including the generation of 3' termini and polyadenylation. Attention has recently been drawn to a group of six small nuclear RNAs (snRNAs), whose extraordinary structural conservation, together with a variety of circumstantial evidence, suggest their participation in functionally conserved steps in eukaryotic gene expression. For example, U1 RNA is hypothesized to mediate intron removal via complementarity to conserved sequences at the splice junction(s). Because of the lack of tractable experimental systems among the higher eukaryotes, these hypotheses have yet to be critically tested. We propose to exploit the powerful genetic techniques uniquely available in yeast to achieve these ends. We are employing two complementary strategies. The first exploits our recent demonstration of the existence in Saccharomyces cerevisiae of snRNAs encoded by single copy genes; this allows us to perform definitive tests of these models by analyzing the consequences of null and conditional alleles in each of these genes. Moreover, the isolation of extragenic suppressors of these mutations will identify cellular components which interact with the snRNAs; these should include the snRNP proteins, as well as potential "target" RNAs: the pre-mRNA substrates. Our second approach takes advantage of our recent identification of a mutant 5' splice junction in a yeast mRNA intron. In this case, the ability to isolate extragenic suppressors should allow a direct test of the "Ul guide model" for RNA splicing