Opposite effects of tor1 and tor2 on nitrogen starvation responses in fission yeast.

The TOR protein kinases exhibit a conserved role in regulating cellular growth and proliferation. In the fission yeast two TOR homologs are present. tor1(+) is required for starvation and stress responses, while tor2(+) is essential.

Regulation of leucine uptake by tor1+ in Schizosaccharomyces pombe is sensitive to rapamycin.

TOR protein kinases are key regulators of cell growth in eukaryotes. TOR is also known as the target protein for the immunosuppressive and potentially anticancer drug rapamycin. The fission yeast Schizosaccharomyces pombe has two TOR homologs.