Novel regulation of rDNA transcription by mTOR/S6K signalling

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Increased cellular growth requires a number of important processes to occur, the most fundamental of which is protein synthesis. Successful synthesis of proteins requires a large number of efficient ribosomes, the protein synthesis machinery. mTOR is a central cellular signalling molecule that directly regulates growth via modulating the efficiency of the ribosomes. It does this by regulating an enzyme called S6 kinase. Interestingly for long term or sustained increases in the rates of growth an increase in the number of ribosomes in addition to an increase efficiency of protein synthesis is required. This proposal will test the hypothesis that the mTOR-S6 kinase signalling pathway regulates protein synthesis both at the level of ribosome efficiency and capacity. This will be extended to determine the mechanism by which such regulation occurs. Furthermore recent studies have demonstrated that S6 kinase is involved in tumor growth. We propose that S6 kinase will contribute to the regulation of both normal or tumor growth at least in part via modulation of the number of ribosomes. Accordingly, S6K is upregulated in a segregated proportion of breast tumors. Outcomes from this project have the potential to provide targets to which specific therapies for particular breast tumors can be developed. Overall this information will also extend our basic knowledge on normal growth regulation.