The association of Tap42 phosphatase complexes with TORC1: another level of regulation in Tor signaling.

In the budding yeast Saccharomyces cerevisiae, rapamycin has been known to induce a rapid dephosphorylation of many downstream targets of Tor. The key components mediating this dephosphorylation process are the Tap42-associated phosphatases, which become active upon rapamycin treatment. However, the mechanism by which rapamycin rapidly activates phosphatases is unclear. A recent report has provided evidence demon strating a physical association of the Tap42-phosphatase complexes with TORC1, which is sensitive to rapamycin treatment or nutrient starvation. This association adds another level of regulation in Tor signaling, and explains why rapamycin or nutrient availability is able to initiate a rapid and robust response in the cell.