Ap4A tetraammonium (P1, P4-Di- (adenosine-5') -tetraphosphate tetraammonium) is a conserved second messenger in organisms ranging from bacteria to humans. Ap4A tetraammonium binds to the histidine triad nucleotide-binding protein 1 (HINT1) activates the transcription of genes downstream of MITF. Ap4A tetraammonium induces apoptosis[1][2].