Control of Gene Expression in the Biosynthesis of Mitochondrial Ribosomes

真核细胞维持不同的细胞器和细胞质蛋白质合成系统，并且在指定这两个系统成分的基因家族之间似乎非常重叠。细胞器翻译系统组成部分的基因分为两个遗传系统。对于酿酒酵母的线粒体翻译系统，rrna、trna和一种核糖体蛋白由线粒体基因组指定，另外还有100多种蛋白质由核基因编码。分子生物学和遗传学相结合的方法被用来鉴定和表征酵母中编码线粒体蛋白质合成机制成分的核基因。这些基因是通过在gtll噬菌体表达载体中构建酵母基因组文库的免疫筛选和线粒体蛋白合成缺陷的温度敏感突变体的遗传互补来克隆的。克隆的基因与特定的免疫探针相结合，为系统地研究一组独特的翻译成分的结构、功能和调控提供了工具。迄今为止的研究主要集中在三种基因上，每一种基因似乎都受到不同的调节模式的影响。特别令人感兴趣的是转录后调控的两个基因。该建议的主要部分是致力于对这些基因受到独特形式的翻译控制的可能性进行批判性评估。同一个细胞中不同的基因组是如何交流的，这仍然是一个遗传学上的谜。这项研究的结果应该能让我们更深入地了解这一过程。

Eukaryotic cells maintain distinct organellar and cytoplasmic systems of protein synthesis, and there appears to be very overlap between the gene familes that specify the components of the two systems. The genes for components of the organellar translation systems are divided between two genetic systems. For the mitochondrial translation system of Saccharomyces cerevisiae, the rRNAs, tRNAs and one ribosomal protein are specified by the mitochondrial genome, and over 100 additional proteins are encoded by nuclear genes. Combined molecular biological and genetic approach is being taken to identify and characterize nuclear genes in yeast that encode components of the mitochondrial protein synthetic machinery. These genes are being cloned by immunological screening of a yeast genomic library constructed in the gtll phage expression vector and by genetic complementation of temperature-sensitive mutants that are defective in mitochondrial protein synthesis. The cloned genes, combined with specific immunological probes, provide the tools to systematically study the structure, function, and regulation of a unique set of translational components. Studies thus far have been focussed on three genes, each of which appears to be subject to different modes of regulation. Of particular interest are two genes that are regulated posttranscriptionally. A major part of this proposal is devoted to the critical evaluation of the possibility that these genes are subject to unique forms of translational control. How different genomes in the same cell communicate is still a genetic mystery. The results of this study should give greater insight into that process.