 Until recently, the two known effects of ARF were growth inhibition by NPM interactions and apoptosis induction by Mdm2 interactions.The function of ARF involving p53-independent death, has now been attributed to the small mitochondrial isoform of ARF, smARF.While full-length ARF inhibits cell growth by cell cycle arrest or type I apoptotic death, smARF kills cells by type II autophagic death.