Grant: Discovery Grants Program - Individual

Ribosomes*are intricate molecular machines that play a central role in translating the*genetic code into proteins. In baker's yeast, assembly of the ribosomal RNA*requires a large number of factors and the correct expression of 137 ribosomal*protein-coding genes the majority of which are duplicated genes. The events*leading to the processing of pre-rRNAs, assembly and export have been*extensively studied in vertebrates and yeast, and the overall process is very*well understood. However, the mechanism regulating the expression of duplicated*ribosomal protein genes and its impact on ribosome biogenesis and function*remain unclear. Recently, we discovered that the majority of the ribosomal*protein paralogs are not expressed equally and that in most cases they are*expressed in a specific ratio required for normal growth. This finding argues*against an equal and redundant role for the ribosomal protein genes paralogs. In*this proposal, we aim at understanding the mechanism regulating the expression*of duplicated genes and its impact on ribosome production and function. Accordingly,*we propose two specific aims: 1. Determine the mechanism regulating the*expression of duplicated ribosomal protein genes. Under this aim, we will*determine how duplicated genes communicate to establish the overall expression*of ribosomal proteins. We have recently identified a set of inter-regulated*duplicated ribosomal genes, and we will use them as a model for this study. The*impact of promoters, intron, transcription termination and cellular*ribonucleases on the expression of these paralogs will be monitored and*elements that affect inter and intragene regulation will be identified. The*outcome of this study will not only explain how the expression of ribosomal*proteins is coordinated but will also help us to understand an important*component of the general mechanism of gene regulation. 2. Understand the*impact of duplicated genes on ribosome biogenesis and function. Under this*aim, we will monitor the impact of changing the ratio of ribosomal proteins on*ribosome biogenesis, translation and cellular functions. The duplicated genes*will be overexpressed from a heterologous promoter, deleted or mutated and the*impact on the associated proteins monitored using expression tags. The impact*on cell function will be measured using a standard set of phenotypic tests,*including temperature sensitivity, drug resistance and use of different carbon*sources. The effects of growth conditions on the paralogs expression will also*be analyzed in order to identify signals inducing changes in the ribosome*composition and function. This project will directly verify the hypothesis*of paralogs driven functional diversification of eukaryotic ribosomes and*provides a mechanistic frame for how ribosome production is modulated in*response to growth conditions.*