Effect of DNA conformation on the transcription of mitochondrial DNA

The importance of the conformation of the DNA template for in vitro transcription experiments was investigated using a mitochondrial RNA polymerase preparation from Xenopus laevis oocyte mitochondria. A premature termination transcription assay has been devised and the levels of the formation of transcriptional complexes have been identified using agarose gel electrophoresis. It was found that accurate initiation of transcription from in vivo promoter sequences was enhanced by supercoiling and that the two mitochondrial DNA-binding proteins, previously characterized by us, inhibited the transcription of DNA as gauged by these assays.