Noxa is a BH3-only member of the Bcl-2 family. Expression of Noxa gene involves direct activation of its promotor by p53. Increased expression of Noxa protein occurs in normal thymocytes but not in p53-deficient thymocytes. Coimmunoprecipitation data sμggest that Noxa protein may interact with proteins belonging to the Bcl-2 family, such as Bcl-xL and Mcl-1. Blocking the endogenous Noxa induction results in the suppression of apoptosis. These sμggest Noxa may represent a candidate mediator of p53-induced apoptosis.