Biochemical and genetic characterization of ribosome biogenesis and functional diversity

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Ribosomes are intricate molecular machines playing a central role in translating the genetic code into proteins. Ribosomes are considered the basis of modern cells and the essence of life. Indeed, it was believed that ribosomes are standard protein factories with uniform functions. In this project, we challenge this notion and propose the existence of a code linking ribosome production and function to cellular needs and changes in growth conditions. In baker's yeast, ribosomes are made of ribonucleic acid (RNA) and several proteins generated from a large set of duplicated genes. The duplicated ribosomal protein genes are very similar in sequence and were believed to have redundant function. Surprisingly, we discovered that these duplicated genes with seemingly identical functions are not expressed equally, and the parolog deletions lead to gene copy specific phenotypic effect. This means that duplicated genes exhibits copy specific function. In this project, we will systematically examine the mechanism regulating the expression of duplicated ribosomal protein genes and measure their impact on cell function and response to stress. We will determine how the duplicated genes communicate to establish a specific ribosomal protein ratio and monitor the impact of altering the established expression pattern on the synthesis and assembly of the different ribosome components. The impact on cell function will be measured using a pre-determined set of phenotypic tests allowing us to identify specific stresses and growth conditions requiring the production of specialized ribosomes. The outcome of this project will not only provide fundamental information about how the cell function but will also help us understand how cells respond to their environment and give us a new approach to determine how functional diversity is achieved.