Autonomy of Mitochondria in Saccharomyces cerevisiae in Their Production of Messenger RNA

In ts(-)136, a temperature-sensitive mutant of Saccharomyces cerevisiae, nuclear and mitochondrial RNA production can be inhibited selectively by exposure to 36 degrees and ethidium bromide, respectively. Using the programming of mitochondrial polysomes, as measured by their ability to form nascent polypeptide chains, as an assay for functional messenger RNA, we have determined its response to temperature shifts and ethidium bromide. Only ethidium bromide produced a measurable effect; in contrast the cell-sap system responded exclusively to temperature shifts. We conclude that transcription of mitochondrial DNA is sufficient and that import of messenger RNA transcribed from nuclear chromosomes makes no measurable contribution to intramitochondrial protein synthesis.