A RNA polymerase III promoter (from 5S rRNA) drives expression of a chimeric RNA that consists of a non-coding leader sequence (from the major mitochondrial 5S rRNA isoform encoded by a nuclear-encoded 5SrRNA gene) and 25bp of sequence complementary to mt:ATPase6 that targets the mt:ATPase6 translational start site. The presence of the NCL sequence targets the RNA to the mitochondrion, where the antisense sequence can act as a translational inhibitor, inhibiting endogenous mitochondrial expression of mt:ATPase6 protein in vivo.