High nutrient levels and TORC1 activity reduce cell viability following prolonged telomere dysfunction and cell cycle arrest.

Cells challenged with DNA damage activate checkpoints to arrest the cell cycle and allow time for repair. Successful repair coupled to subsequent checkpoint inactivation is referred to as recovery. When DNA damage cannot be repaired, a choice between permanent arrest and cycling in the presence of damage (checkpoint adaptation) must be made. While permanent arrest jeopardizes future lineages, continued proliferation is associated with the risk of genome instability. We demonstrate that nutritional signaling through target of rapamycin complex 1 (TORC1) influences the outcome of this decision. Rapamycin-mediated TORC1 inhibition prevents checkpoint adaptation via both Cdc5 inactivation and autophagy induction. Preventing adaptation results in increased cell viability and hence proliferative potential. In accordance, the ability of rapamycin to increase longevity is dependent upon the DNA damage checkpoint. The crosstalk between TORC1 and the DNA damage checkpoint may have important implications in terms of therapeutic alternatives for diseases associated with genome instability.