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F Foury

Publications and source records attributed to F Foury.

11 recordsLinked to original sources
PubMed1979

Genetic control of enhanced mutability of mitochondrial DNA and gamma-ray sensitivity in Saccharomyces cerevisiae.

Five nuclear mutants enhancing the spontaneous mutation rate of mtDNA have been isolated in Saccharomyces cerevisiae. These mutators fall into five complementation groups and are located at five genetic loci different from rad50 to rad57 loci. Three mutants (gam1, gam2, and gam4), insensitive or weakly sensitive to gamma-rays, exhibit increased frequency of spontaneous production of mutants with large deletions of the mtDNA (p-) and of all tested mitochondrial drug-resistant mutants. Two other mutants (gam3 and gam5), highly sensitive to gamma-rays, increase only the mutation rate of particular alleles of the mtDNA. The mutant gam5 enhances only the production of p- and erythromycin-resistant clones. The mutant gam3 exhibits an enhanced rate of oligomycin-resistant clones as well as a collateral increase of nuclear mutability. The existence of gam3 and gam5 mutants indicates that at least two common steps control both nuclear DNA repair and the mutability of particular alleles of the mtDNA. However, the general spontaneous mutability of the mtDNA includes at least three steps not involved in the repair of nuclear DNA, as revealed by the gam1, gam2, and gam4 mutations.

Chromosome Mapping↗
PubMed1978

Assembly of the mitochondrial membrane system. Genetic complementation of mit- mutations in mitochondrial DNA of Saccharomyces cerevisiae.

A method has been devised to test intergenic complementation of mutations in the mitochondrial DNA of Saccharomyces cerevisiae. The test is based on the observation that diploids issued from pairwise crosses of certain mit- mutants with deficiencies in cytochrome oxidase, or coenzyme QH2-cytochrome c reductase, acquire high levels of respiratory activity shortly after zygote formation. Under our experimental conditions neither biochemical complementation, interallelic complementation, nor recombination has been found to contribute to any significant extent toward the respiration measured in the diploids at early times. The test has been used to study the number of complementation groups represented by a large number of mit- mutants. Results of pairwise crosses of mutants in the oxi 1, oxi 2, oxi 3, cob 1, and cob 2 loci indicate that complementation occurs between the oxi and cob loci between different oxi loci but not between the two cob loci. The five loci have, therefore, been assigned to four different complementation groups.

DNA, Mitochondrial↗
PubMed1977

Energy-dependent uptake of calcium by the yeast Schizosaccharomyces pombe.

1. In resting cells of the fission yeast Schizosaccharomyces pombe, the uptake of calcium is stimulated by the addition of 90 mM glucose in the presence as in the absence of respiration and inhibited by Antimycin A in the absence of exogenous carbon source. This uptake therefore requires fermentative or respiratory metabolic energy. 2. The calcium uptake by S. pombe exhibits saturation kinetics and high affinity for calcium. At external pH 4.5, the apparent Km is 45 muM ca2+ 400 muM of other divalent cations exert competitive inhibitions of calcium uptake in the following order of affinities: Sr2+ greater than Mn2+ greater than Co2+ greater than Mg2+. Inhibition by KCl is also observed but is of non-competitive type and requires high concentrations of the order of 40 mM. 3. At 30 degrees C, the uptake rate of calcium is about 10-times higher at pH 8925 than at pH 4.0. An extrusion of 45Ca2+, the rate of which is estimated to be lower than one-fifth of the uptake, is observed in the presence of glucose when the external pH is acid. 4. At external pH 4.5, low concentrations of lanthanum chloride, ruthenium red and hexamine cobaltichloride are inhibitory for the uptake of calcium by the yeast cells. 5. In presence of Antimycin A, the uncouplers: NaN3, dinitrophenol, and concentrations of crobonylcyanide m-chlorophenylhydrazone higher than 80 muM inhibit the calcium uptake by glycolysing cells. In the presence of glucose, the K+ ionophore Dio-9 dnhances severalfold the uptake of calcium even at 2 degrees C. 6. It is concluded that S. pombe possess an active transport system for low concentrations of calcium. This transport seems to be dependent on an electric potential (negative inside) across the cellular membrane.

Antimycin A↗
PubMed1976

Assembly of the mitochondrial membrane system. XVIII. Genetic loci on mitochondrial DNA involved in cytochrome b biosynthesis.

1. Fourteen cytoplasmic mutants of Saccharomyces cerevisiae with a specific deficiency of cytochrome b have been studied. The mutations have been shown to occur in two separate genetic loci, COB 1 and COB 2. These loci can be distinguished by mit- X mit- crosses. Pairwise crosses of cytochrome b mutants belonging to different loci yield 4-6% wild type recombinants corresponding to recombinational frequencies of 8-12%. In intra-locus crosses, the recombinational frequencies range from 1% to less than 0.01%. The two loci can also be distinguished by mit- X rho- crosses. Twenty rho- testers have been isolated of which ten preferentially restore mutations in COB 1 and ten others in COB 2. 2. The COB 1 and COB 2 loci have been localized on mitochondrial DNA between the two antibiotic resistance loci OLI 1 and OLI 2 in the order OLI 2-COB 2-COB 1-OLI 1. The results of mit- X mit- and mit- X rho- crosses have also been used to map the cytochrome b mutations relative to each other. The maps obtained by the two independent methods are in good agreement. 3. Mutations in COB 1 have been found to be linked to the OLI1 locus in some but not in other strains of S. cervisiae. This evidence suggests that there may be a spacer region between the two loci whose length varies from strain to strain. 4. Two mutations in COB 2 have been found to cause a loss of a mitochondrial translation product corresponding to the cytochrome b apoprotein. Instead of the wild type protein the mutants have a new low-molecular weight product which is probably a fragment of cytochrome b. The fact that the mutations revert suggests that they are nonsense mutations in the structural gene of cytochrome b.

Anti-Bacterial Agents↗
PubMed1976

Assembly of the mitochondrial membrane system. XIX. Genetic characterization of mit- mutants with deficiencies in cytochrome oxidase and coenzyme qh2-cytochrome c reductase.

Nineteen mutants of S. cerevisiae exhibiting a double deficiency in cytochrome oxidase and coenzyme QH2-cytochrome c reductase (also cytochrome b deficient) have been studied. The mutants have been crossed to a set of rho- tester strains with different segments of mitochondrial DNA. The mutants have also been crossed to mit- testers with defined genetic lesions. In addition, crosses were performed with a respiratory competent strain to ascertain whether mitotic and meiotic segregants could be isolated with only one of the two enzymatic deficiencies. The rho- testers allowed the doubly deficient mutants to be separated into two classes. Mutants in class 1 were not restored by any of the rho- testers and appeared to have separate mutations, one in cytochrome oxidase and the other in cytochrome b. Mutants in class 2 were restored by a set of rho- clones whose retained segments of mitochondrial DNA contained the cytochrome b but not the cytochrome oxidase loci. These appeared to behave as single hit mutations. Further studies, however, indicated that both class 1 and class 2 mutants carried separate mutations in two different loci. Mitotic and meiotic segregants with a single enzymatic deficiency could be isolated. In a number of strains, the mutations were mapped in known cytochrome oxidase and cytochrome b loci. The apparent discrepancy of the rho- tests for the class 2 mutants was shown to be probably due to a high unstability in one of the mutations. It has been concluded that all the doubly deficient strains carry two mutations in previously described cytochrome oxidase and cytochrome b loci. This conclusion argues against the existence of a single gene on mitochondrial DNA that controls the biosynthesis of the two respiratory enzymes.

Cell Division↗
PubMed1976

Localization on mitochondrial DNA of mutations leading to a loss of rutamycin-sensitive adenosine triphosphatase.

Four cytoplasmic mutants of Saccharomyces cerevisiae showing loss of mitochondrial rutamycin-sensitive ATPase activity but having significant cytochrome oxidase and NADH-cytochrome c reductase have been isolated. Genetic studies indicate the mutations to be closely linked to each other and have been assigned to a new locus, PHO1. The mutations show a low frequency of recombination with the OL12 locus, suggesting a linkage to this marker. They are not, however, linked to the OLI1 locus. Linkage of the ATPase mutations to the OLI2 locus is also indicated by restoration of wild-type diploids by sigma- clones that retain the segment of mitochondrial DNA carrying OLI2. Based on the recombinants issued from crosses of the mutants with a triple drug-resistant strain and an analysis of the resistance markers present in sigma- clones that are effective in restoring a wild-type phenotype, the PHO1 locus has been placed in the segment of DNA located between PAR1 and OLI2.

Adenosine Triphosphatases↗
PubMed1975

Regulation of mitochondrial biogenesis: enzymatic changes in cytochrome-deficient yeast mutants requiring delta-aminolevulinic acid.

Yeast cells almost completely deficient in all cytochromes were obtained by introducing two defective nuclear genes, cyd1 and cyc4, into the same haploid strain. The action of the two mutant genes is synergistic, since either gene acting singly results in only partial cytochrome deficiency. Normal synthesis of all cytochromes can be restored in the double mutant by adding delta-aminolevulinic acid to the growth medium. The optimum concentration of delta-aminolevulinate for restoration of cytochrome synthesis is about 40 muM; when higher concentrations are used, synthesis of cytochromes is partially suppressed, particularly that of cytochrome a.a3. Growth yield of the double mutant is stimulated by ergosterol and Tween 80, a source of unsaturated fatty acid. Methionine stimulates further. None of these nutrients is required for growth when sufficient delta-aminolevulinic acid is present in the growth medium. With respect to nutritional responses, the single-gene, cytochrome-deficient mutant, ole3, behaves like the double mutant. The frequency of the p-mutation in the double mutant grown in the absence of ergosterol, Tween 80, and delta-aminolevulinic acid is at least 15%. The frequency can be reduced to less than 1% by either delta-aminolevulinic acid or Tween 80. Ergosterol alone does not decrease the p- frequency. The ole3 mutant does not exhibit increased p-frequency under similar conditions of unsaturated fatty acid deficiency.

5-Aminolevulinate Synthetase↗
PubMed1975

Stimulation of active uptake of nucleosides and amino acids by cyclic adenosine 3' :5'-monophosphate in the yeast Schizosaccharomyces pombe.

In conditions of glucose starvation, the maximum velocity of the mediated transport of nonmetabolized and metabolized amino acids, uridine, adenosine, and sucrose across the plasma membrane is stimulated by a factor of two by the addition of 1 mM adenosine 3':5'-monophosphate to Schizosaccharomyces pombe 972h- wild strain, to the glucose-super-repressed and derepressed mutants COB5 and COB6, and to Saccharomyces cerevisiae strain IL 216-IA. The mediated uptake of 2-D-deoxyglucose and the apparently nonmediated uptake of guanosine are not stimulated by the cyclic nucleotide. N6,O2'-Dibutyryl adenosine 3':5'-monophosphate is also efficient, whereas theophylline, guanosine 3':5'-monophosphate, 5'-AMP, ATP, and adenosine are ineffective. The cellular ATP content of glycerol-grown S. pombe COB5 is about 10 nmol per mg of protein and is not decreased by further incubation in the starvation medium. The addition of 100 mM glucose markedly enhances transport without any increase of the cellular ATP content. The addition of antimycin A or Dio-9 decreases markedly both cellular ATP content and transport. The addition of 2.5 mM glucose to antimycin A-containing medium restores both transport is not necessarily of mitochondrial origin. The uptake of 2-D-deoxyglucose is unaffected by the respiratory inhibitors. Stimulation of uptake by cyclic adenosine 3':5'-monophosphate occurs only in glucose-deprived cells. The addition of 10 mM glucose elicits the disappearance of the stimulation and prevents the 30% decrease of the cellular adenosine 3':5'-monophosphate content produced by glucose starvation. Adenosine 3':5'-'monophosphate does not enhance the steady state ATP level but requires cellular ATP produced either by endogenous respiration or, in the absence of respiration blocked by antimycin A, by further addition of 2.5 mM glucose. Stimulation of active uptake by adenosine 3':5'-monophosphate does not require protein synthesis because the addition of cycloheximide or anisomycin does not prevent the stimulation of L-leucine uptake. In the absence of respiration, Dio-9, and ATPase inhibitor, suppresses instantaneously the cellular ejection of protons as well as the uptake of uridine and amino acids. It abolishes also the adenosine 3':5'-monophosphate-stimulated transport. In the presence of antimycin A, specific mitochondrial ATPase inhibitors such as venruricidin A do not inhibit metabolite uptakes and their stimulation by adenosine 3':5'-monophosphate. These results suggest that in these conditions, the target of Dio-9 is not the mitochondrial ATPase but a plasma membrane proton-translocating function generating an electrochemical gradient required for active transport. That adenosine 3':5'-monophosphate enhances the Dio-9-sensitive proton extrusion supports the view that the cyclic nucleotide might modulate the plasma membrane ATPase.

Adenosine Diphosphate↗