| Modification Notes |
Tor proteins, which encode putative phosphatidylinositol kinases, are involved in a signal transduction pathway in S. cerevisiae that activates cell wall expansion and protein synthesis in response to nutrient availability (1-3). Both Tor1 and Tor2 mediate protein synthesis via the phosphorylation of Tap42, which inhibits type-2A phosphatases (1,2,4,5). Tor1 and Tor2 also regulate G1 progression in yeast , and loss of Tor or treatment with rapamycin causes cells to arrest in early G1 (3-6). In addition to its overlapping function with Tor1, Tor2 is essential for the regulation of the cell-cycle-dependent organization of the actin cytoskeleton (5-7). The Tor signaling pathway is thought to mediate cell growth by harboring transcription factors in the cytoplasm, which mediate nutrient metabolism (2). |