Intercalating drugs and low temperatures inhibit synthesis and processing of ribosomal RNA in isolated human mitochondria.
Mitochondrial DNA transcription in isolated HeLa cell mitochondria faithfully reproduces the in vivo process. In this system, actinomycin D, proflavine and ethidium bromide preferentially inhibit the formation of ribosomal RNA over that of messenger RNA, strongly supporting independent controls of the two overlapping transcription units involved in their synthesis. The processing step removing the tRNAPhe sequence at the 5' end of the ribosomal RNA precursor is uniquely sensitive to low temperature, proflavine and ethidium bromide.