Mitochondrial heredity of resistance to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, an inhibitor of cytochrome b oxidation, in Saccharomyces cerevisiae.

3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), an inhibitor of cytochrome b oxidation, has been used for the selection of three resistant mutants (diur) of Saccharomyces cerevisiae. The mutant diur-64 exhibits in vivo cross-resistance to antimycin A while diur-34 and diur-1 are more sensitive to antimycin A than the parental strain. The three mutants exhibit mitochondrial inheritance according to the following criteria: mitotic segregation of diuron-resistant and diuron-sensitive diploids is obtained among the diploid progeny of a cross between diur and dius; non-Mendelian segregation of diuron resistance (4:0) is observed in spores of tetrads issued from diuron-resistant diploid; extensive ethidium bromide treatment leads to the formation of Q- mutants which no longer transmit diur and dius alleles. Evidence for two distinct diuron-resistant loci were obtained by allelism tests. Recombination analysis shows that diuron-resistance is not located in the polar region of the mitochondrial genome. The diur loci are not linked to the erythromycin locus since the upper limit in recombinants frequency (26%) for a non-polar region is obtained between diur and eryr. A low recombinants frequency (3%) is observed in crosses between diur-34 mutation and the two mutants cob1 and cob2 suggesting that diur-34 might be located between these two cytochrome-b-deficient loci. The resistance to diuron is also expressed in vitro since the oxidation rates of succinate by sonicated submitochondrial particles from the mutants are clearly less sensitive to diuron than that of the wild type.     

Reduced plasma membrane permeability in a multiple cross-resistant strain of Saccharomyces cerevisiae.

Single nuclear gene inheritance was shown to be responsible for increased resistance to: eight diverse inhibitors of mitochondrial function (antimycin, carbonylcyanide-m-chlorophenylhydrazone, chloramphenicol, oligomycin, tetracycline, triethyltin bromide, triphenylmethylphosphonium bromide and triton-X-165); and an inhibitor of cytoplasmic protein synthesis (cycloheximide). Continuous monitoring of oxygen uptake during respiratory adaptation showed that anerobic pretreatment of resistant cells sensitized respiratory adaptation to chloramphenicol and antimycin. However, since a depression of mitochondrial function by catabolite repression did not result in sensitization to antimycin, alteration of the mitochondrial membrane does not appear to be responsible for resistance to mitochondrial inhibition. Alteration of cellular binding sites was not responsible for resistance since in vitro mitochondrial protein synthesis was sensitive to chloramphenicol and in vitro mitochondrial respiration was sensitive to oligomycin, carbonylcyanide-m-chlorophenylhydrazone, and antimycin. Autoradiography of an ethylacetate-ethanol extract of [14C]chloramphenicol-treated resistant cells indicated that resistance was not due to enzymatic modification of inhibitors. The maintenance of an antimycin-resistant respiration by protoplasts of resistant cells ruled out the involvement of the cell wall in cellular resistance. The reduced transport of [14C]chloramphenicol by resistant cells (1% of normal cells) indicated that a single nuclear gene mutation can alter the permeability of the plasma membrane to many diverse inhibitors.     

Single nuclear gene inherited cross resistance and collateral sensitivity to 17 inhibitors of mitochondrial function in S. cerevisiae

Summary Previous tetrad analyses defined a yeast strain (332-7c) as containing a single nuclear gene (11.8 map units from the centromere) conferring resistance to oligomycin. Resistance to 18 additional inhibitors of mitochondrial function (Table 1) was determined on (i) ascospore isolates from tetrads segregating 2 resistant: 2 sensitive for oligomycin (Table 2) and (ii), spontaneously derived sensitive isolates of the oligomycin resistant strain (Tables 3 and 4). The observed pattern of resistance suggests that the gene for resistance to oligomycin also results in (i) cross resistance to rutamycin, venturicidin, triethyltin bromide, antimycin A, carbonylcyanide m-chlorophenylhydrazone, tetra-N-butylammonium bromide, dibenzyl-dimethylammonium chlorop and tetracycline and (ii), collateral sensitivity to paromomycin, neomycin, dequalinium chloride, ethidium bromide and acriflavin.     

Studies on the mechanism of electron trasport in the bc1-segment of the respiratory chain in yeast. III. Isolation and characterization of an antimycin resistant mutant ANT 8 in Schizosaccharomyces pombe.

1. A mutant (ANT 8) of Schizosaccharomyces pombe which shows resistance to antimycin both in vivo and in vitro is characterized biochemically and genetically. 2. In crosses of ANT 8 with auxotrophic strains, resistance to antimycin segregates 2:2 indicating that resistance is conferred by a single nuclear gene. Diploids heterozygous for the resistance gene, however, show segregation of the resistance and sensitivity during mitosis. Possible reasons for this segregation are discussed. 3. Compared with the wild type, the NADH oxidase of ANT 8 requires 13 times as much antimycin for 95% inhibition. After addition of ubiquinone-3, electron transport which is less sensitive to antimycin is found only in the mutant. 4. The resistance of the mutant ANT 8 si due to the much weaker binding of antimycin to mitochondria. As in the wild type, two antimycin binding sites can be separated by binding studies. From the inhibition curves it is evident that binding of antimycin to oxidized mitochondrial particles does not correspond with its inhibitory effect on the partly reduced enzyme in kinetic studies. 5. The peak of the b-cytochrome absorbing at 560.2 nm at 77 degrees K in the wild type is shifted to 561 nm in the mutant. 6. A special preparation method for mutant mitochondrial particles is described, yielding highly active enzymes and CO-insensitive cytochromes. 7. The results are discussed with reference to the components in our model of the respiratory chain, which may be responsible for this type of resistance.     

Cytoplasmic inheritance of antimycin A resistance in Saccharomyces cerevisiae

Summary Three antimycin resistant mutants of Saccharomyces cerevisiae are characterized genetically. The mutations have been shown to be cytoplasmically inherited by four criteria. The phenotype persists in diploids formed by a cross with a ⁰ strain of yeast of the opposite mating type. Diploids heterozygous for the antimycin marker, however, show segregation of the resistance and sensitivity during mitosis. Tetrad analysis indicated a non-Mendelian segregation (4:0 and 0:4) of the mutations. The antimycin marker can be eliminated by ethidium bromide treatment under conditions that should have deleted all of the mitochondrial DNA.     

Activity of reduced ubiquinone: Cytochrome c oxidoreductase with various ubiquinol-isoprenologues as substrate and corresponding inhibitory effect of antimycin in yeast

1. Reduced ubiquinones-1, -2, -3, -4 and -6 were used as substrates for ubiquinol: cytochrome c oxidoreductase.2. The portion of antimycin-sensitive activity depends on the concentration of ubiquinol and on the pH. Only reduced ubiquinone-2 and reduced ubiquinone-3 show high activities the main part of which is sensitive to antimycin.3. The antimycin effect curve of ubiquinol: cytochrome c oxidoreductase is linear in shape with reduced ubiquinone-2 as substrate but sigmoidal with reduced ubiquinone-3 and succinate. Ubiquinol-3: cytochrome c oxidoreductase activity contains a portion scarcely affected by antimycin. About 300 pmoles of antimycin per mg protein, enough to inhibit succinate, NADH- and reduced ubiquinone-2:cytochrome c oxidoreductase almost totally, affect ubiquinol-3: cytochrome c oxidoreductase to only about 80% and another 300 pmoles of antimycin are needed for the next 10% of inhibition.4. The activities of succinate- and NADH: cytochrome c oxidoreductase are stimulated by ubiquinones-2 and -3. The shapes of the inhibition curves by antimycin of the stimulated activities are sigmoidal. About twice the amount of antimycin is necessary to inhibit stimulated activities to the same value as the unstimulated.5. The non-ionic detergent Lubrol WX is not effective in stimulating enzymatic activities. However, in the presence of 0.6 M sorbitol, it converts the linear antimycin effect curve with reduced ubiquinone-2 as substrate, into sigmoidal.6. NADH- and succinate: cytochrome c oxidoreductase activities and reduced ubiquinone-2 and reduced ubiquinone-3: cytochrome c oxidoreductase activities become deactivated with increasing concentrations of the non-ionic detergent Lubrol WX. The activity with reduced ubiquinone-2 as substrate is less resistant to the action of the detergent than with reduced ubiquinone-3. The b-cytochromes do not become CO-reactive by this treatment.7. Deoxycholate in low concentrations does not stimulate ubiquinol: cytochrome c oxidoreductase activity. It converts the inhibition curve by antimycin from sigmoidal to linear with increasing concentrations of the detergent with all substrates tested. The amount of antimycin needed for 90% inhibition of reduced ubiquinone activities is about the same under these conditions as with succinate, NADH or reduced ubiquinol in untreated particles.8. The results are discussed with respect to the theories of the electron transport mechanism and of the inhibition by antimycin of the electron flow through the bc₁-segment of the respiratory chain in beef heart.     

Cytochrome b of protozoan mitochondria: relationships between function and structure.

1. The sensitivity of ubiquinol:cytochrome c reductase to its most powerful inhibitors has been characterized in mitochondria from three ciliate and two trypanosome protozoans and compared with that in mitochondria of animals and plants. 2. Mitochondria of ciliates, particularly those of Tetrahymena pyriformis, are resistant to antimycin. 3. Mitochondria of trypanosomes are quite resistant to stigmatellin, as they exhibit a 40-fold higher titer than that in ciliate or animals mitochondria. 4. Both ciliates and trypanosomes are highly resistant to myxothiazol. 5. Correlations have been drawn between the natural resistance of the protozoan mitochondria to antimycin, stigmatellin and myxothiazol and peculiar features in the structure of their apocytochrome b, on the basis of an accurate alignment of the sequences of this protein.     

Germination properties of a spore coat-defective mutant of Bacillus subtilis.

The presence of the gerE36 mutation in strains of Bacillus subtilis 168 resulted in poor germination of their spores in a range of germinants, as measured by the fall in absorbance of spore suspensions. Although resistant to heat and organic solvents, spores were sensitive to lysozyme; electron microscopy revealed that their coat structure was incomplete. These spores responded to germinants by losing heat resistance and changing from phase bright to phase gray. The release of dipicolinic acid and the fall in absorbance of spore suspensions reached only 75 and 50% of wild-type levels, respectively, but followed the same time course as the loss of heat resistance. Although the germination response was incomplete, the concentration of L-alanine required to elicit it was the same for the mutant as for the wild type. The properties of mutant spores suggest that an intact spore coat is not required for the initial interaction between germinant and spore, but that the coat layers may contain molecules important in later stages of germination. In transduction with phage SPP1, the gerE36 mutation mapped between citF and ilvB and was 90% cotransduced with citF2. The gerE mutation identifies the location of a gene important for the progress of late stages of spore formation.     

Antimycin A mimics a cell-death-inducing Bcl-2 homology domain 3

The Bcl-2-related survival proteins confer cellular resistance to a wide range of agents. Bcl-xL-expressing hepatocyte cell lines are resistant to tumour necrosis factor and anti-cancer drugs, but are more sensitive than isogenic control cells to antimycin A, an inhibitor of mitochondrial electron transfer. Computational molecular docking analysis predicted that antimycin A interacts with the Bcl-2 homology domain 3 (BH3)-binding hydrophobic groove of Bcl-xL. We demonstrate that antimycin A and a Bak BH3 peptide bind competitively to recombinant Bcl-2. Antimycin A and BH3 peptide both induce mitochondrial swelling and loss of DeltaPsim on addition to mitochondria expressing Bcl-xL. The 2-methoxy derivative of antimycin A3 is inactive as an inhibitor of cellular respiration but still retains toxicity for Bcl-xL+ cells and mitochondria. Finally, antimycin A inhibits the pore-forming activity of Bcl-x L in synthetic liposomes, demonstrating that a small non-peptide ligand can directly inhibit the function of Bcl-2-related proteins.     

Characterization of rat liver mitochondria depleted of inner membrane components by chloramphenicol treatment of regenerating rat liver.

The maximal decline of adenosine triphosphate phosphohydrolase (ATPase; EC 3.6.1.3) in mitochondria from regenerating rat liver on treatment with chloramphenicol occurs between 48 and 72 h after partial hepatectomy. The depleted mitochondria are well coupled, exhibiting a respiratory control ratio of about 7 with succinate. These mitochondria are fully sensitive to rutamycin for the inhibition of succinate state 3 respiration. In frozen-thawed mitochondria there is a 60% reduction in ATPase activity, and of this remaining ATPase activity only 50% is sensitive to rutamycin. The titers for release of succinate state 4 respiration and ATPase activity by 5-Cl, 3-tert-butyl, 2′-Cl, 4′-NO₂-salicylanilide are decreased, and the efficiency of the uncoupler is increased. The antimycin titer for inhibition of succinate state 3 respiration is decreased. In all cases where a decrease in activity or titer was observed it is about the same (50%), suggesting inhibition at a common site for these parameters.     

Selection and characterization of a rice mutant resistant to 5-methyltryptophan

Summary A rice plant resistant to 5-methyltryptophan (5MT) was selected from mutagenized M3 seeds (Oryza sativa L. var. Sasanishiki) originating from panicles treated with ethylene imine (0.2%) 2 h after flowering. When germinated on 5MT-containing medium, the seeds (M4) from selfed plants segregated with a 3 resistant:1 sensitive ratio, indicating that the plant was heterozygous for a resistance gene and that the resistance was dominant. The resistance was also expressed in callus derived from seeds. Analysis of the free amino acids in seeds, seedlings, and calli showed that homozygous resistant plants (TR1) contained higher levels of total free amino acids than sensitive plants. In particular the levels of tryptophan, phenylalanine, and histidine were, respectively, 8.5, 5.4, and 4.9 times higher than those in the sensitive plants.     

转不可翻译PVY^N CP基因烟草的抗病性分析

我们曾报道表达不可翻译PVY^N CP基因的转基因烟草抗病性是由RNA介导的,其抗病性类似于转录后的基因沉默(PTGS)。本研究以这类不同抗性的T0代转基因烟草植株为材料,对自交后的T1代转基因植株的遗传和抗病性进行了分析,并选取部分T1代抗病株系自交留种。对T2代RNA介导抗病性转基因植株进行了分子分析和一系列抗病性研究。结果表明,含1—2个转基因拷贝的T0代感病植株,在T1代中的Km抗性分离符合单位点插入的3：1的遗传规律;含3个或3个以上转基因拷贝的T0代中抗或高抗植株,在T1代中的Km抗性分离符合多位点插入的15：1或63：1的遗传规律。大多数T1、T2代转基因植株的抗病性与转基因拷贝数成正相关,转基因在T1、T2代植株中能够转录表达,且转基因植株之间转基因mRNA在细胞质中的积累水平与转基因植株的抗病性成负相关。转基因植株的抗病性能够在T1、T2代中遗传,且T2代转基因植株的抗病性具有以下特征：1)既抗病毒粒体又抗病毒RNA的侵染,且这种抗病性不受接种物剂量的影响;2)抗病谱较窄,只对PVY的某些株系具有高度抗病性;3)与传毒方式无关,既抗摩擦接种又抗带毒蚜虫接种;4)与植株的发育阶段没有关系。     

Electron and proton transport in the ubiquinone cytochrome b-c2 oxidoreductase of Rhodopseudomonas sphaeroides. Patterns of binding and inhibition by antimycin.

The effect of antimycin on the ubiquinone cytochrome b-c2 (Q b-c2) oxidoreductase of the photosynthetic bacterium Rhodopseudomonas sphaeroides has been studied under controlled oxidation-reduction potential (Eh) conditions by equilibrium measurements and by rapid kinetic analysis of single turnover flash.induced electron and proton translocations. 1. Antimycin shifts the alpha-band of ferro b50 (lambda max 560 nm) by 1 to 2 nm toward the red but has no apparent effect on the equilibrium oxidation-reduction midpoint potential of the cytochrome. 2. This red shift is proportional to the antimycin added until a "titer" of 0.7 +/- 0.1 antimycin per reaction center (RC) is approached. With a similar titer antimycin essentially abolishes the following millisecond reactions activated by saturating single turnover flashes: reduction of ferri c2, oxidation of ferro b, Phase III of the membrane-potential-indicating band shift of endogenous carotenoid pigments, and the uptake of 1 of the 2 protons taken up per electron transferred. Such titrations indicate that the binding (KD approximately 10(-9) m) and mode of inhibition of antimycin are noncooperative and are independent of the membrane's coupling status and of the pH and Eb over the range in which electron transport is operative. 3. In the presence of excess antimycin a partial recovery of ferri c2 reduction is seen when the intensity of the flash is diminished, but only at Eh values such that Z (a special quinone serving as reductant for ferri c2) is reduced but b50 is oxidized before activation. These results are consistent with the following model. Each Q b-c2 oxidoreductase complex includes one antimycin binding site, one b50, and one Z. These complexes and the c2 . RC complexes, present in an 0.7:1 ratio, are to some degree mobile with respect to each other. Ferri b50 can be reduced either via the quinones of the RC or via Z in a reaction also involving c2. The former route is kinetically dominant in the presence of antimycin, but the latter route is the means for "oxidant-induced reduction" and depends on the collisional interaction of the oxidoreductase and c2 . RC complexes. Antimycin interferes with neither of these two routes but does inhibit the oxidation of ferro b50; all the other inhibitory effects are consequent on this.     

ATPase complex and oxidative phosphorylation in chloramphenicol-induced megamitochondria from mouse liver.

1. Functional properties of the ATPase complex are investigated in megamitochondria isolated from livers of weanling mice fed a diet containing 2% chloramphenicol, as an inhibitor of mitochondrial protein synthesis. 2. Whereas the specific activity of ATPase remains unchanged in chloramphenicol-induced megamitochondria, about 40% of the enyzme activity is resistant to inhibition by oligomycin, triethyltin or venturicidin. It is concluded that the ATPase complex lacks one or more components whose synthesis or accumulation is dependent on mitochondrial translation. The inhibitor-resistant ATPase portion appears tightly bound to the mitochondrial membrane. 3. Respiratory chain phosphorylation is tightly coupled in isolated megamitochondria. ATP synthesis and ATP-Pi exchange are diminished by 40%, as compared to control mitochondria, but both processes are sensitive to oligomycin, triethyltin or venturicidin. 4. The decrease in ATP synthesis and ATP-Pi exchange in megamitochondria correlates quite well with the emergence of inhibitor-resistant ATPase. 5. The following electron transport activities in the megmitochondria are reduced: NADH-cytochrome c reductase, by 60%, cytochrome oxidase, by 80%; the amount of antimycin required to gain complete inhibition of the bc1-segment is diminished by more than 50%. On the other hand succinate dehydrogenase activity is increased by 50%. 6. Chloramphenicol-induced megamitochondria appear to be a useful system for studying the role of mitochondrial translation in the assembly of mammalian mitochondria.     

7个香蕉品种对枯萎病的抗性评价及3种评价方法的对比

[目的] 评价香蕉自主选育品种对枯萎病病原菌尖孢镰刀菌古巴专化型（Fusarium oxysporum f. sp. cubense）热带4号小种（tropical race 4, Foc TR4）的抗性。[方法] 以浸根法和2种灌注法将Foc TR4接种于不同抗性的香蕉品种上,分析接种后香蕉的发病情况,比较筛选这3种评价方法,并评价7个香蕉品种的苗期和田间抗性水平。[结果] 采用浓度为2×10⁵ 个·mL^-1的PDB培养基Foc TR4孢子悬浮液灌注法进行香蕉苗期抗性评价更为高效可行;综合苗期和田间抗性评价结果,7个香蕉品种的抗性由高到低为：南天黄>红研3号>红研5号>红研2号>滇蕉1号>巴西蕉>红研1号。[结论] 以南天黄作为高抗品种对照,以巴西蕉作为高感品种对照条件下,红研3号和红研5号抗性为中等抗性偏强,红研2号达到中抗水平,滇蕉1号为感病,红研1号为高度感病。     

Role of the spore coat layers in Bacillus subtilis spore resistance to hydrogen peroxide, artificial UV-C, UV-B, and solar UV radiation

Spores of Bacillus subtilis possess a thick protein coat that consists of an electron-dense outer coat layer and a lamellalike inner coat layer. The spore coat has been shown to confer resistance to lysozyme and other sporicidal substances. In this study, spore coat-defective mutants of B. subtilis (containing the gerE36 and/or cotE::cat mutation) were used to study the relative contributions of spore coat layers to spore resistance to hydrogen peroxide (H(2)O(2)) and various artificial and solar UV treatments. Spores of strains carrying mutations in gerE and/or cotE were very sensitive to lysozyme and to 5% H(2)O(2), as were chemically decoated spores of the wild-type parental strain. Spores of all coat-defective strains were as resistant to 254-nm UV-C radiation as wild-type spores were. Spores possessing the gerE36 mutation were significantly more sensitive to artificial UV-B and solar UV radiation than wild-type spores were. In contrast, spores of strains possessing the cotE::cat mutation were significantly more resistant to all of the UV treatments used than wild-type spores were. Spores of strains carrying both the gerE36 and cotE::cat mutations behaved like gerE36 mutant spores. Our results indicate that the spore coat, particularly the inner coat layer, plays a role in spore resistance to environmentally relevant UV wavelengths.     

Proteomic identification of predictive biomarkers of resistance to neoadjuvant chemotherapy in luminal breast cancer: a possible role for 14-3-3 theta/tau and tBID?

Introduction

Chemotherapy resistance is a major obstacle in effective neoadjuvant treatment for estrogen receptor-positive breast cancer. The ability to predict tumour response would allow chemotherapy administration to be directed towards only those patients who would benefit, thus maximising treatment efficiency. We aimed to identify putative protein biomarkers associated with chemotherapy resistance, using fresh tumour samples with antibody microarray analysis and then to perform pilot clinical validation experiments.

Materials and methods

Chemotherapy resistant and chemotherapy sensitive tumour samples were collected from breast cancer patients who had received anthracycline based neoadjuvant therapy consisting of epirubicin with cyclophosphamide followed by docetaxel. A total of 5 comparative proteomics experiments were performed using invasive ductal carcinomas which demonstrated estrogen receptor positivity (luminal subtype). Protein expression was compared between chemotherapy resistant and chemotherapy sensitive tumour samples using the Panorama XPRESS Profiler725 antibody microarray containing 725 antibodies from a wide variety of cell signalling and apoptosis pathways. A pilot series of archival samples was used for clinical validation of putative predictive biomarkers.

Results

AbMA analysis revealed 38 differentially expressed proteins which demonstrated at least 1.8 fold difference in expression in chemotherapy resistant tumours and 7 of these proteins (Zyxin, 14-3-3 theta/tau, tBID, Pinin, Bcl-xL, RIP and MyD88) were found in at least 2 experiments. Clinical validation in a pilot series of archival samples revealed 14-3-3 theta/tau and tBID to be significantly associated with chemotherapy resistance.

Conclusions

For the first time, antibody microarrays have been used to identify proteins associated with chemotherapy resistance using fresh breast cancer tissue. We propose a potential role for 14-3-3 theta/tau and tBID as predictive biomarkers of neoadjuvant chemotherapy resistance in breast cancer. Further validation in a larger sample series is now required.     

Evolutionary dynamics of cancer multidrug resistance in response to olaparib and photodynamic therapy

P-glycoprotein (P-gp) is an adenosine triphosphate (ATP)-dependent drug efflux protein commonly associated with multidrug resistance in cancer chemotherapy. In this report, we used a dual-fluorescent co-culture model to study the population dynamics of the drug sensitive human ovarian cancer cell line (OVCAR-8-DsRed2) and its resistant subline that overexpresses P-gp (NCI/ADR-RES-EGFP) during the course of a photodynamic therapy (PDT)-olaparib combination regimen. Without treatment, OVCAR-8-DsRed2 cells grew more rapidly than the NCI/ADR-RES-EGFP cells. Olaparib treatment reduced the total number of cancer cells by 70±4% but selected for the resistant NCI/ADR-RES-EGFP population since olaparib is an efflux substrate for the P-gp pump. This study used the FDA-approved benzoporphyrin derivative (BPD) photosensitizer or its lipidated formulation ((16:0)LysoPC-BPD) to kill OVCAR-8 cells and reduce the likelihood that olaparib-resistant cells would have selective advantage. Three cycles of PDT effectively reduced the total cell number by 66±3%, while stabilizing the population ratio of sensitive and resistant cells at approximately 1:1. The combination of olaparib treatment and PDT enhanced PARP cleavage and deoxyribonucleic acid (DNA) damage, further decreasing the total cancer cell number down to 10±2%. We also showed that the combination of olaparib and (16:0)LysoPC-BPD-based PDT is up to 18-fold more effective in mitigating the selection of resistant NCI/ADR-RES-EGFP cells, compared to using olaparib and BPD-based PDT. These studies suggest that PDT may improve the effectiveness of olaparib, and the use of a lipidated photosensitizer formulation holds promise in overcoming cancer drug resistance.     

Modification and Inheritance of Pleiotropic Cross Resistance and Collateral Sensitivity in SACCHAROMYCES CEREVISIAE

A meiotic segregant (oli^PR1) was isolated with a phenotype of multiple cross resistance and collateral sensitivity. Strain oli^PR1 has increased sensitivity to ethidium bromide, dequalinium chloride, acriflavin, paromomycin and neomycin, and increased resistance to oligomycin, rutamycin, venturicidin, triethyltin bromide, antimycin, carbonylcynamide-m-chlorophenylhydrazone, tetra-N-butylammonium bromide, dibenzyldimethylammonium chloride, triphenylmethylphosphonium bromide, chloramphenicol, carbomycin, tetracycline, triton-X-165 and cycloheximide. Single gene inheritance of the cross resistance and collateral sensitivity was shown by 2:2 parental ditype segregation and reversion of the complete phenotype by a spontaneous revertant. The locus conferring the oli^PR1 phenotype was mapped 11.7 units from an unspecified centromere. Antibiotic resistance showed incomplete dominance, with the level of hybrid resistance dependent upon the inhibitor tested. Resistant diploids that produced four resistant ascospores were the result of mitotic recombination prior to meiosis. A partial revertant phenotype (sensitive to all inhibitors except oligomycin, antimycin and carbonylcyanide-m-chlorophenylhydrazone) was shown to be due to a single nuclear gene causing partial suppression of oli^PR1. Anaerobic pretreatment, 37° and 0.5 M KCl were observed to reduce the growth of oli^PR1 when challenged with seven diverse inhibitors (antimycin, carbonylcyanide-m-chlorophenylhydrazone,-chloramphenicol, cycloheximide, oligomycin, triethyltin bromide, and triphenylmethylphosphonium bromide). Resistance to cycloheximide was not altered by the [rho—] state. A revertant of oli^PR1 (sensitive to the above inhibitors but resistant to ethidium bromide, paromycin and neomycin) showed anaerobic and temperature sensitization to ethidium bromide, paromomycin and neomycin. Continuous monitoring of oxygen uptake by the revertant after anaerobic pretreatment revealed that anaerobiosis sensitized respiratory adaptation of the revertant to neomycin. It is proposed that oli^PR1 is a mutation resulting in the alteration of plasma membrane premeability to many diverse inhibitors.