Loss of the TOR kinase Tor2 mimics nitrogen starvation and activates the sexual development pathway in fission yeast.
Fission yeast has two TOR (target of rapamycin) kinases, namely Tor1 and Tor2. Tor1 is required for survival under stressed conditions, proper G(1) arrest, and sexual development. In contrast, Tor2 is essential for growth. To analyze the functions of Tor2, we constructed two temperature-sensitive tor2 mutants. Interestingly, at the restrictive temperature, these mutants mimicked nitrogen starvation by arresting the cell cycle in G(1) phase and initiating sexual development. Microarray analysis indicated that expression of nitrogen starvation-responsive genes was induced extensively when Tor2 function was suppressed, suggesting that Tor2 normally mediates a signal from the nitrogen source. As with mammalian and budding yeast TOR, we find that fission yeast TOR also forms multiprotein complexes analogous to TORC1 and TORC2. The raptor homologue, Mip1, likely forms a complex predominantly with Tor2, producing TORC1. The rictor/Avo3 homologue, Ste20, and the Avo1 homologue, Sin1, appear to form TORC2 mainly with Tor1 but may also bind Tor2. The Lst8 homologue, Wat1, binds to both Tor1 and Tor2. Our analysis shows, with respect to promotion of G(1) arrest and sexual development, that the loss of Tor1 (TORC2) and the loss of Tor2 (TORC1) exhibit opposite effects. This highlights an intriguing functional relationship among TOR kinase complexes in the fission yeast Schizosaccharomyces pombe.
Matsuo
Tomohiko
T
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan. yamamoto@biochem.s.u-tokyo.ac.jp
Otsubo
Yoko
Y
Urano
Jun
J
Tamanoi
Fuyuhiko
F
Yamamoto
Masayuki
M
D016193:G1 Phase; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D049770:Genes, Mating Type, Fungal; D008540:Meiosis; D026901:Membrane Transport Proteins / Q000235:genetics; D050505:Mutant Proteins / Q000302:isolation & purification; D009584:Nitrogen / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000172:deficiency* / Q000378:metabolism*; D011485:Protein Binding; D012568:Schizosaccharomyces / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D046468:Sexual Development / Q000502:physiology*
D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D009584:Nitrogen; D019869:Phosphatidylinositol 3-Kinases; D029702:Schizosaccharomyces pombe Proteins; C513100:tor2 protein, S pombe