Absence of expression from RNA internalised into electroporated mammalian mitochondria

Transfection of mammalian mitochondria has proved to be notoriously difficu lt. Whilst there have been sporadic reports of import of foreign nucleic ac ids into isolated organelles, these imported nucleic acids have never been demonstrated to be functional. Inability to manipulate mitochondrial gene e xpression has hampered our understanding of RNA processing, maturation and translation in mitochondria. In an attempt to establish a model system for mt-RNA expression, we have electroporated rat liver mitochondria and mitopl asts in the presence of various RNA constructs built around the mitochondri al reporter gene mt-luciferase. Following electroporation, a fraction of th e RNA was shown to be stably maintained, mitochondria remained coupled for oxidative phosphorylation and intramitochondrial protein synthesis was unaf fected. In no case, however, was this RNA translated.