The fission yeast TOR homolog, tor1(+), is required for the response to starvation and other stresses via a conserved serine

Targets of rapamycin (TORs) are conserved phosphatidylinositol kinase-relat ed kinases that are involved in the coordination between nutritional or mit ogenic signals and cell growth, Here we report the initial characterization of two Schizosaccharomyces pombe TOR homologs, tor1(+) and tor2(+). tor2() is an essential gene, whereas tor1(+) is required only under starvation a nd other stress conditions. Specifically, Delta tor1 cells fail to enter st ationary phase or undergo sexual development and are sensitive to cold, osm otic stress, and oxidative stress, In complex with the prolyl isomerase FKB P12, the drug rapamycin binds a conserved domain in TORs, FRB, thus inhibit ing some of the functions of TORs, Mutations at a conserved serine within t he FRB domain of Saccharomyces cerevisiae TOR proteins led to rapamycin res istance but did not otherwise affect the functions of the proteins. The S. pombe tor1(+) exhibits different features; substitution of the conserved se rine residue, Ser(1834), With arginine compromises its functions and has no effect on the inhibition that rapamycin exerts on sexual development in S, pombe.