A "petite obligate" mutant of Saccharomyces cerevisiae: functional mtDNA is lethal in cells lacking the delta subunit of mitochondrial F1-ATPase.
Within the mitochondrial F(1)F(0)-ATP synthase, the nucleus-encoded delta-F(1) subunit plays a critical role in coupling the enzyme proton translocating and ATP synthesis activities. In Saccharomyces cerevisiae, deletion of the delta subunit gene (Deltadelta) was shown to result in a massive destabilization of the mitochondrial genome (mitochondrial DNA; mtDNA) in the form of 100% rho(-)/rho degrees petites (i.e. cells missing a large portion (>50%) of the mtDNA (rho(-)) or totally devoid of mtDNA (rho degrees )). Previous work has suggested that the absence of complete mtDNA (rho(+)) in Deltadelta yeast is a consequence of an uncoupling of the ATP synthase in the form of a passive proton transport through the enzyme (i.e. not coupled to ATP synthesis). However, it was unclear why or how this ATP synthase defect destabilized the mtDNA. We investigated this question using a nonrespiratory gene (ARG8(m)) inserted into the mtDNA. We first show that retention of functional mtDNA is lethal to Deltadelta yeast. We further show that combined with a nuclear mutation (Deltaatp4) preventing the ATP synthase proton channel assembly, a lack of delta subunit fails to destabilize the mtDNA, and rho(+) Deltadelta cells become viable. We conclude that Deltadelta yeast cannot survive when it has the ability to synthesize the ATP synthase proton channel. Accordingly, the rho(-)/rho degrees mutation can be viewed as a rescuing event, because this mutation prevents the synthesis of the two mtDNA-encoded subunits (Atp6p and Atp9p) forming the core of this channel. This is the first report of what we have called a "petite obligate" mutant of S. cerevisiae.
Duvezin-Caubet
Stéphane
S
Institut de Biochimie et Génétique Cellulaires, Université Victor Segalen, 1 Rue Camille Saint-Saëns, Bordeaux 33077 cedex, France.
Rak
Malgorzata
M
Lefebvre-Legendre
Linnka
L
Tetaud
Emmanuel
E
Bonnefoy
Nathalie
N
di Rago
Jean-Paul
JP
D001692:Biological Transport; D004272:DNA, Mitochondrial; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008928:Mitochondria / Q000201:enzymology*; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics*; D011522:Protons; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
D004272:DNA, Mitochondrial; D011522:Protons; D029701:Saccharomyces cerevisiae Proteins; D025261:Mitochondrial Proton-Translocating ATPases; D006180:Proton-Translocating ATPases