RP041 -Independent Maintenance of [rho⁻] Mitochondrial DNA in Saccharomyces cerevisiae Walton L. Fangman

Abstract

A subset of promoters in the mitochondrial DNA (mtDNA) of the yeast Saccharomyces cerevisiae has been proposed to participate in replication initiation, giving rise to a primer through site-specific cleavage of an RNA transcript. To test whether transcription is essential for mtDNA maintenance, we examined two simple mtDNA deletion ([rho⁻]) genomes in yeast cells. One genome (HS3324) contains a consensus promoter (ATATAAGTA) for the mitochondrial RNA polymerase encoded by the nuclear gene RP041, and the other genome (4a) does not. As anticipated, in RP041 cells transcripts from the HS3324 genome were more abundant than were transcripts from the 4a genome. When the RP041 gene was disrupted, both [rho~] genomes were efficiently maintained. The level of transcripts from HS3324 mtDNA was decreased >400-fold in cells carrying the RP041 disrupted gene; however, the low-level transcripts from 4a mtDNA were undiminished. These results indicate that replication of [rho⁻] genomes can be initiated in the absence of wild-type levels of the RP041 -encoded RNA polymerase.