UASt regulates expression of a catalytically dead and mitochondria-excluded/cytoplasmic version of the P{mito-APOBEC1} "mtDNA mutator" - codon GAA is changed to GCT at amino acid position 63 of the Rnor\Apobec1 cDNA, resulting in a Glu63Ala change, and the mitochondrial targeting sequence has been removed.