Regulation of gene expression is a fundamental process in all cellular systems. While the major steps in gene regulation such as transcription and translation are well understood, the role of tRNA availability (e.g. abundance, half-life) in regulating translation is largely unknown. The ultimate objective of this proposal is to investigate how tRNA availability within a cell can influence which mRNA molecules are actively translated by the ribosome. More specifically, it aims to address (i) whether mechanisms such as transcription, nucleo-cytoplasmic transport and degradation vary for individual tRNAs coding for different amino acids and (ii) how altered tRNA dynamics can affect protein abundance, and hence fitness, in different cellular conditions.To address these questions, I propose systematically charting the tRNA abundance landscape using yeast as a model organism. I will quantitatively investigate the processes of tRNA production, transport and degradation, in order to determine which steps in tRNA homeostasis are altered under diverse stress conditions, compared to optimal growth conditions. I will then investigate the impact of tRNA dynamics in cell fitness through competitive growth experiments. In this manner, I propose to construct the first dynamic map of tRNA abundance, which holds the potential to help understand the process of gene expression regulation in fine detail.In the long-term, the goals described in this proposal will not only provide new insights into regulatory mechanisms of protein translation but will also help to achieve a better understanding of factors that influence fitness and cell survival. With recent discoveries relating changes in tRNA abundance to apoptosis and gene misregulation in tumorigenic cells, future research on understanding how tRNA availability is regulated and how it contributes to cell survival could lead to new strategies for the rational design of molecular therapies against cancer.