Toward understanding the global functions of target of rapamycin (TOR) proteins in Saccharomyces cerevisiae

Rapamycin is a bacterial antibiotics currently under clinical trials for various types of organ transplantation and anti-tumor therapy. The Target of Rapamycin (TOR) protein is a highly conserved protein kinase essential for cell growth. To understand its general functions and relevance to human diseases, the main theme of this study is to identify novel biological processes regulated by TOR. Using the yeast Saccharomyces cerevisiae as a model organism, the first part of the study involved a genome-wide rapamycin-sensitivity screening of the knockout mutants collection. Changes in global gene expression pattern upon inhibition of TOR by rapamycin treatment were also studied. Results led to the characterization of a possible mechanism by which TOR regulates autophagy, a cellular recycling process to salvage amino acids when cells are under nitrogen-limiting conditions. Finally, a possible role of TOR in the regulation of the late stage of cell-cycle progression, namely cytokinesis, was discussed.