Transcription-dependent DNA transactions in the mitochondrial genome of a yeast hypersuppressive petite mutant.
Mitochondrial DNA (mtDNA) of Saccharomyces cerevisiae contains highly conserved sequences, called rep/ori, that are associated with several aspects of its metabolism. These rep/ori sequences confer the transmission advantage exhibited by a class of deletion mutants called hypersuppressive petite mutants. In addition, because they share features with the mitochondrial leading-strand DNA replication origin of mammals, rep/ori sequences have also been proposed to participate in mtDNA replication initiation. Like the mammalian origins, where transcription is used as a priming mechanism for DNA synthesis, yeast rep/ori sequences contain an active promoter. Although transcription is required for maintenance of wild-type mtDNA in yeast, the role of the rep/ori promoter as a cis-acting element involved in the replication of wild-type mtDNA is unclear, since mitochondrial deletion mutants need neither transcription nor a rep/ori sequence to maintain their genome. Similarly, transcription from the rep/ori promoter does not seem to be necessary for biased inheritance of mtDNA. As a step to elucidate the function of the rep/ori promoter, we have attempted to detect transcription-dependent DNA transactions in the mtDNA of a hypersuppressive petite mutant. We have examined the mtDNA of the well-characterized petite mutant a-1/1R/Z1, whose repeat unit shelters the rep/ori sequence ori1, in strains carrying either wild-type or null alleles of the nuclear genes encoding the mitochondrial transcription apparatus. Complex DNA transactions were detected that take place around GC-cluster C, an evolutionarily conserved GC-rich sequence block immediately downstream from the rep/ori promoter. These transactions are strictly dependent upon mitochondrial transcription.
Van Dyck
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Department of Developmental Biology, Stanford University School of Medicine, California 94305-5427, USA.
Clayton
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DA
D004261:DNA Replication; D004272:DNA, Mitochondrial / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D006609:High Mobility Group Proteins / Q000378:metabolism; D009154:Mutation; D012313:RNA / Q000378:metabolism*; D000077278:RNA, Mitochondrial; D018741:Replication Origin; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
C072843:ABF2 protein, S cerevisiae; D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D000077278:RNA, Mitochondrial; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D012313:RNA; D004720:Endonucleases