We first discovered a gene called PNC1, which turns vitamin B3 into NAD. That led us to try boosting PNC1 by introducing four extra copies of it into the yeast cells, giving them five copies in total. Those yeast cells lived 50 percent longer than normal, but not if we removed the SIR2 gene. The cells were making extra NAD, and the sirtuin survival circuit was being engaged!
PNC1
