In yeast, caloric restriction (CR) delays aging by activating the Sir2 deacetylase. Here we
show that expression of mammalian Sir2 (SIRT1) is induced in CR rats as well as in human
cells that are treated with serum from these animals. Insulin and insulin-like growth factor 1
(IGF-1) attenuated this response. SIRT1 deacetylates the DNA repair factor Ku70, causing it
to sequester the proapoptotic factor Bax away from mitochondria, thereby inhibiting stress …