The purpose of the present invention is to provide a system in which an apoptosis-inducing factor is expressed in an expression promoter-dependent manner, which is not a system wherein a toxin is introduced externally, and a novel protein that can enhance an apoptosis signal used in the system. The present invention relates to An apoptosis-inducing factor comprising a fusion protein of a polypeptide comprising FADD or a constituting domain thereof and a protein with a self-assembling activity, an expression vector comprising DNA encoding the apoptosis-inducing factor, a transgenic animal having the expression vector introduced therein, an animal wherein apoptosis is induced in a specific cell or tissue and/or at a specific time and a method for producing the animal.