RIBOSOMAL GENES OF YEAST AND THEIR REGULATION

点击翻译按钮获取中文摘要

The synthesis of ribosomes is a complex but tightly regulated process in which the cell synthesizes equimolar amounts of four ribosomal RNAs in the nucleus, and of seventy-five ribosomal proteins in the cytoplasm, and assembles them into a ribosome in the nucleolus. We propose to study in Saccharomyces cerevisiae the mechanisms controlling both the transcription of ribosomal RNA and the synthesis of ribosomal proteins. Ribosomal RNA: We have identified a sequence in the rDNA repeat with many of the properties of an enhancer element. We plan to identify the precise sequences involved in this effect. We will ask whether this enhancer element: a) binds a specific transcription factor? b) is involved in the regulation of transcription of 35S prerRNA? c) is responsible for the 1:1 ratio of the transcription of 35S prerRNA and 5S RNA, whose gene lies between the enhancer and the 35S initiation site? Ribosomal Protein: The rates of transcription of most, if not all, ribosomal protein genes are tightly coupled. To understand the mechanism behind this coupling we will identify the sequences essential for the transcription of one ribosomal protein gene and then determine if similar sequences are used for other ribosomal protein genes. We will ask if the same sequences are involved in regulation of their transcription and/or whether there is a transcription factor specific for these genes. Finally, we will analyze the mechanism for translational control of ribosomal protein synthesis, with emphasis on testing the hypothesis that a regulatory molecule interacts with the m7G cap and its adjacent sequences.