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Regulatory interactions between mitochondrial genes: interactions between two mosaic genes
Abstract:
We have studied the mitochondrial DNA and the phenotypes of strains of Saccharomyces cerevisiae with specific intervening sequences in two mosaic genes: cob (the gene for apocytochrome b) and oxi3 (the gene for subunit I of cytochrome oxidase). The results suggest the following. (i) The presence of an intervening sequence downstream encompassing the intron box7 is sufficient for the regulation of oxi3 by cob (BOX phenotype); two sequences (containing intron loci box3 and box10) upstream in cob and two in oxi3 are dispensable. (ii) Strains without the two sequences upstream still contain the downstream sequence and the competence to specify a functional trans-acting element. Mutational lesions in this segment are phenotypically indistinguishable from box7 mutants, including the accumulation of polypeptides with homologous amino acid sequences. (iii) A catabolite-sensitive BOX phenotype, characteristic of mutants in the first exon, requires the simultaneous presence of an adjacent intervening sequence. A model is presented in which a hypothetical product specified by an intron (locus box7) of the cob gene controls the expression of a second mosaic gene (oxi3).
Insights
A specific intron sequence in Saccharomyces cerevisiae
Area of Science:
- Mitochondrial genetics
- Molecular biology
- Yeast genetics
Background:
- Mosaic genes like cob and oxi3 in Saccharomyces cerevisiae contain intervening sequences.
- Understanding the function of these intervening sequences is crucial for gene regulation.
- Previous studies have hinted at complex regulatory mechanisms within mitochondrial genes.
Purpose of the Study:
- To investigate the role of specific intervening sequences in the cob and oxi3 mosaic genes.
- To elucidate the regulatory relationship between the cob and oxi3 genes.
- To characterize the BOX phenotype and its genetic basis.
Main Methods:
- Analysis of mitochondrial DNA and phenotypes in Saccharomyces cerevisiae strains.
- Genetic manipulation to study the effects of specific intervening sequences.
- Biochemical analysis of polypeptide accumulation in mutant strains.
Main Results:
- A downstream intervening sequence (box7) in the cob gene is sufficient for regulating the oxi3 gene (BOX phenotype).
- Upstream sequences in cob and oxi3 are dispensable for this regulation.
- Mutations in the regulatory segment mimic box7 mutants, leading to polypeptide accumulation.
Conclusions:
- A hypothetical product from the cob gene's intron (box7) likely controls the expression of the oxi3 gene.
- The presence of a specific downstream intervening sequence is key for this intergenic regulation.
- This study provides a model for intron-mediated gene expression control in mitochondria.