Induction of respiration deficient mutants in Saccharomyces cerevisiae by berenil. II. Characteristics of the process

Petite and sectored induction in Saccharomyces cerevisiae by propidium iodide: synergistic effect of sodium dodecyl sulfate

Sodium dodecyl sulfate (SDS) was examined for its effect on petite and sectored colony induction in Saccharomyces cerevisiae by propidium iodide (PI) and ethidium bromide (EB). 4-h cultivation with 100 microM PI and 100 micrograms/ml SDS resulted in virtually all plated cells growing as sectored colonies with no decrease in viability. Sectored colonies are mixed colonies comprised of respiratory deficient and competent cells believed to be derived from an unstable respiratory deficient cell. Further cultivation with PI and SDS prior to plating led to induction of complete petite colonies with a rapid decrease in viable cells. PI alone at this concentration exhibited weak induction of sectored colonies (maximum 12.3% at 8 h) and petite colonies (maximum 10.8% at 12 h), but SDS alone caused induction of neither. 50 microM PI had almost the same activity as 100 microM except for a delay in the induction of sectored colonies in the initial stage, and a decreased rate of petite colony induction. The effects of 20 microM PI and SDS were much lower than that by 50 microM and no inhibition of growth was observed. 10 microM PI was quite inactive even in the presence of SDS. Under resting conditions, 10 approximately 100 microM PI and 100 micrograms/ml SDS induced about 60% sectored colonies at 12 h incubation and more than 60% petite colonies at 24 h. After 6 h incubation, decrease in survival was also observed.

Studies on the induction of petite mutants in yeast by analogues of berenil. Characterization of three mutants resistant to the compound Hoe 15,030

Compound Hoe 15,030 is an analogue of berenil which is as effective as berenil in inducing petite mutants in Saccharomyces cerevisiae. Hoe 15,030 has greater stability than berenil in aqueous solution, and is less toxic to yeast at high drug concentrations. Mutants of S. cerevisiae strain J69-1B have been isolated which are resistant to the petite inducing effects of Hoe 15,030. Three mutant strains (HR7, HR8 and HR10) were characterized and each was shown to carry a recessive nuclear mutation determining resistance to Hoe 15,030. The degree of resistance to Hoe 15,030 is different for each mutant, and each was found to be co-ordinately cross-resistant both to berenil and to another analogue of berenil, Hoe 13,548. However, the three mutants show no cross-resistance to other unrelated petite inducing drugs, including ethidium bromide, euflavine and 1-methyl phenyl neutral red. Further studies on the mutants revealed that each strain exhibits characteristic new properties indicative of changes in mitochondrial membrane functions concerned with the replication (and probably also repair) of mitochondrial DNA. Thus, mutant HR7 is hypersensitive to petite induction by the detergent sodium dodecyl sulphate under conditions where the parent J69-1B is unaffected by this agent. Mutant HR8 is even more sensitive to sodium dodecyl sulphate than is HR7, and additionally shows a markedly elevated spontaneous petite frequency. Isolated mitochondria from strains HR8 and HR10 (but not HR7) show resistance to the inhibitory effects of Hoe 15,030 on the replication of mitochondrial DNA in vitro.

A novel class of Saccharomyces cerevisiae mutants specifically UV-sensitive to "petite" induction

A mutant of Saccharomyces cerevisiae has been isolated which, though exhibiting a normal response to nuclear genetic damage by ultraviolet light (UV), is more sensitive than its wild type specifically in the production of the cytoplasmic (rho-) mutation by this agent. Some of the features of this mutation which has been designated uvsrho 5 are: i) The mutation is recessive, it exhibits a Mendelian, and hence presumably nuclear, pattern of segregation, but manifests its effects specifically and pleiotropically on mitochondrial functions. ii) Mutant cells resemble their wild type parents in a) growth characteristics on glucose; b) in their UV induced dose response to lethality or nuclear mutation and c) the ability of their mitochondrial genome, upon mating with appropriate testers, of transmitting and recombining various markers, albeit with enhanced efficiency. Similarly, d) they are able to modulate the expression of mitochondrial mutagenesis by ethidium bromide. Thus their mitochondrial DNA appears genetically as competent as that of the wild type. iii) Mutant cells differ from their wild type parents in a) growth characteristics on glycerol; b) susceptibility to induction of the mitochondrial (rho-) mutation by various mutagens, in that the rate of spontaneous mutation is slightly and that by UV is significantly enhanced, whild that by ethidium bromide is greatly diminished. Conversely, c) modulating influences resulting in the repair of initial damage are diminished fro UV and stimulated in the case of Berenil. iv) The amount of mitochondrial DNA per cell appears elevated in the mutant, relative to wild type, and its rate of degradation subsequent to a mutagenic exposure to either UV or ethidium bromide is diminished. v) A self-consistent scheme to account for this and all other information so far available for the induction and modulation of the (rho-) mutation is presented. In a previous study it was shown that some nuclear mutants of Saccharomyces cerevisiae, more sensitive to lethal damage induced by ultraviolet light (rad) than their parent wild type (RAD), also exhibit a concomitant modification in sensitivity to both nuclear and cytoplasmic genetic damage (Moustacchi, 1971). However, another class of rad mutants respond to the induction of the cytoplasmic "petite" also designated as rho- (or rho-) mutation by UV in a manner indistinguishable from that of the RAD strain. One possible interpretation of this last observation is that some of the steps in the expression of the UV damage on mitochondrial (mt)DNA may be governed by other nuclear and cytoplasmic genetic determinants, the products of which may then act specifically on mitochondrial lesions. If this assumption is correct, it should be possible to find mutants with a normal response to nuclear damage but specifically UV-sensitive towards induction of (rho-)...

Effect of caffeine on the rho- -induction with ethidium bromide in Saccharomyces cerevisiae

It is shown that caffeine antagonizes petite-induction with ethidium bromide under non-growth conditions when administered during or after mutagenic treatment. Caffeine itself is shown to be a petite-inducing agent when cells are grown in liquid glucose-complete-medium in the presence of the drug. A possible mode of action of caffeine in the ethidium bromide induced petite-mutagenesis is discussed.

A protective effect of caffeine on the ethidium induced petite mutation in yeast

A prerequisite for petite induction by ethidium bromide (EB) is an initial covalent attachment of the drug to cytoplasmic DNA. This DNA modification is thought to initiate repair processes. The repair inhibitor, caffeine, provided a protective effect against the ethidium induced petite mutation at caffeine concentrations known to inhibit the repair of UV damage in cytoplasmic DNA (Fig. 1). Mitochondrial DNA isolated from yeast exposed to EB in vivo was not as degraded in the presence of both drugs as with EB alone (Fig. 2).

Promotion of sporulation by caffeine pretreatment in Saccharomyces cerevisiae. I. Metabolism of nucleic acids and protein during sporulation

Cells cultured in the presence of caffeine had high sporulation ability. The sporulation-promotive effect of caffeine was studied, special attention being paid upon changes in nucleic acid metabolism. When transferred to a sporulation medium, the breakdown of RNA, the synthesis of protein, RNA and DNA, commitment to sporulation and the appearance of mature asci took place in caffeine-treated cells significantly earlier than in control cells. Commitment to sporulation occurred before the completion of premeiotic DNA synthesis in both caffeine-treated and control cells.

Biogenesis of mitochondria. 43. A comparative study of petite induction and inhibition of mitochondrial DNA replication in yeast by ethidium bromide and berenil

The action of ethidium bromide and berenil on the mitochondrial genome of Saccharomyces cerevisiae has been compared in three types of study: (i) early kinetics (up to 4 h) of petite induction by the drugs in the presence or absence of sodium dodecyl sulphate; (ii) genetic consequences of long-term (8 cell generations) exposure to the drugs; (iii) inhibition of mitochondrial DNA replication, both in whole cells and in isolated mitochondria. The results have been interpreted as follows. Firstly, the early events in petite induction differ markedly for the two drugs, as indicated by differences in the short-term kinetics. After some stage a common pathway is apparently followed because the composition of the population of petite cells induced after long-term exposure are very similar for both ethidium bromide and berenil. Secondly, both drugs probably act at the same site to inhibit mitochondrial DNA replication, in view of the fact that a petite strain known to be resistant to ethidium bromide inhibition of mitochondrial DNA replication was found to have simultaneously acquired resistance to berenil. From consideration of the drug concentrations needed to inhibit mitochondrial DNA replication in vivo and in vitro it is suggested that in vivo permeability barriers impede the access of ethidium bromide to the site of inhibition of mitochondrial DNA replication, whilst access of berenil to this site is facilitated. The site at which the drugs act to inhibit mitochondrial DNA replication may be different from the site(s) involved in early petite induction. Binding of the drugs at the latter site(s) is considered to initiate a series of events leading to the fragmentation of yeast mitochondrial DNA and petite induction.

Comparative studies on sporulation-promotive actions on cyclic AMP, theophylline and caffeine in Saccharomyces cerevisiae

Cyclic AMP, theophylline and caffeine promoted sporulation when added to a presporulation medium containing glucose. Caffeine promoted sporulation even when added to a presporulation medium containing acetate as the carbon source, but cyclic AMP and theophylline did not. Caffeine did not increase the intracellular cyclic AMP level, while theophylline did significantly when added to a presporulation medium containing glucose. Caffeine inhibited the vegatative DNA synthesis with little effect on RNA and protein synthesis, resulting in the increase in cell volume, dry weight, and RNA and protein contents, but cyclic AMP and theophylline did not show such effects.

Coupling between mitochondrial mutation and energy transduction

Upon incubation with ethidium bromide (Etd Br) isolated mitochondria of Saccharomyces cerevisiae have been shown to be capable of performing five novel reactions: (a) a single scission of their DNA (mtDNA) coincident with (b) the incorporation of Etd Br into the product (mtDNA --> 2 mtDNA'-Etd Br); (c) an energy- (and probably ATP-) requiring degradation of mtDNA'-Etd Br to acid-labile products. These reactions acting in series generate (d) a DNase dependent on both Etd Br and an energy supply with mtDNA'-Etd Br as an obligatory intermediate. Coincident with (d) there occurs (e) an activation of adenosinetriphosphatase. Experiments with specific inhibitors suggest that the enzyme responsible is the mitochondrial adenosinetriphosphatase complex itself, and that it and the ability to carry out reactions (a) through (e) are tightly coupled to the energy-transducing functions of the particle.