Intensive radiotherapy can be toxic in 60 percent of patients with tumors located in the gastrointestinal cavity. Increases in levels of the protein URI protect mice against high-dose ionizing radiation-induced gastrointestinal syndrome and enhance mouse intestinal regeneration and survival in 100 percent of the cases. This finding could be useful to mitigate side effects of other sources of intensive radiation, such as nuclear accidents, nuclear warfare or the exposure to cosmic radiation during space explorations.