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PubMed1997

Saccharomyces cerevisiae Nip7p is required for efficient 60S ribosome subunit biogenesis.

The Saccharomyces cerevisiae temperature-sensitive (ts) allele nip7-1 exhibits phenotypes associated with defects in the translation apparatus, including hypersensitivity to paromomycin and accumulation of halfmer polysomes. The cloned NIP7+ gene complemented the nip7-1 ts growth defect, the paromomycin hypersensitivity, and the halfmer defect. NIP7 encodes a 181-amino-acid protein (21 kDa) with homology to predicted products of open reading frames from humans, Caenorhabditis elegans, and Arabidopsis thaliana, indicating that Nip7p function is evolutionarily conserved. Gene disruption analysis demonstrated that NIP7 is essential for growth. A fraction of Nip7p cosedimented through sucrose gradients with free 60S ribosomal subunits but not with 80S monosomes or polysomal ribosomes, indicating that it is not a ribosomal protein. Nip7p was found evenly distributed throughout the cytoplasm and nucleus by indirect immunofluorescence; however, in vivo localization of a Nip7p-green fluorescent protein fusion protein revealed that a significant amount of Nip7p is present inside the nucleus, most probably in the nucleolus. Depletion of Nip7-1p resulted in a decrease in protein synthesis rates, accumulation of halfmers, reduced levels of 60S subunits, and, ultimately, cessation of growth. Nip7-1p-depleted cells showed defective pre-rRNA processing, including accumulation of the 35S rRNA precursor, presence of a 23S aberrant precursor, decreased 20S pre-rRNA levels, and accumulation of 27S pre-rRNA. Delayed processing of 27S pre-rRNA appeared to be the cause of reduced synthesis of 25S rRNA relative to 18S rRNA, which may be responsible for the deficit of 60S subunits in these cells.

Alleles↗
PubMed1985

Isolation of the SUP45 omnipotent suppressor gene of Saccharomyces cerevisiae and characterization of its gene product.

The Saccharomyces cerevisiae SUP45+ gene has been isolated from a genomic clone library by genetic complementation of paromomycin sensitivity, which is a property of a mutant strain carrying the sup45-2 allele. This plasmid complements all phenotypes associated with the sup45-2 mutation, including nonsense suppression, temperature sensitivity, osmotic sensitivity, and paromomycin sensitivity. Genetic mapping with a URA3+-marked derivative of the complementing plasmid that was integrated into the chromosome by homologous recombination demonstrated that the complementing fragment contained the SUP45+ gene and not an unlinked suppressor. The SUP45+ gene is present as a single copy in the haploid genome and is essential for viability. In vitro translation of the hybrid-selected SUP45+ transcript yielded a protein of Mr = 54,000, which is larger than any known ribosomal protein. RNA blot hybridization analysis showed that the steady-state level of the SUP45+ transcript is less than 10% of that for ribosomal protein L3 or rp59 transcripts. When yeast cells are subjected to a mild heat shock, the synthesis rate of the SUP45+ transcript was transiently reduced, approximately in parallel with ribosomal protein transcripts. Our data suggest that the SUP45+ gene does not encode a ribosomal protein. We speculate that it codes for a translation-related function whose precise nature is not yet known.

Actins↗
PubMed1997

Diplogonoporiasis presumably introduced into Spain: first confirmed case of human infection acquired outside the Far East.

A 58-year-old man who was very fond of eating raw fish and had not left Zaragoza Province in Spain in the last 20 years excreted a short chain of gravid proglottids. Treatment with 50 mg/kg of paromomycin sulfate was divided into three doses, all given within the same day, followed by administration of a laxative at night. On days 1 and 2 post-treatment, several chains of degenerated proglottids were evacuated. Only eggs were expelled on days 3 and 4. A long complete strobila including the scolex, and immature, mature, and gravid segments was spontaneously discharged on day 25 after treatment. It was identified as Diplogonoporus balaenopterae, and was the first confirmed case of diplogonoporiasis outside the Far East (all previous cases were reported from Japan, except for one recent case reported from Korea). The origin of this case, outside of its normal geographic location, may be associated with the importation of fish into Spain. The viability of the infective larval stage is evidence of its resistance to export/import conditions. Treatment with paromomycin sulfate did not result in the whole worm being discharged but several short strobilar chains showed drug-induced degeneration.

Animals↗
PubMed2006

Drug unresponsiveness & combination therapy for kala-azar.

Pentavalent antimonials (SbV) have been successfully used for treatment of kala-azar since last six decades. Since 1970s its conventional dosages have failed to achieve with 60 per cent unresponsiveness reported with WHO regimen in Bihar (India). Pentamidine initially used as a second line of drug, acquired resistance (25%) even with prolonged dosage. Newer oral drug miltefosine is a potent antileishmanial drug with longer half-life, a property likely to acquire resistance. Paromomycin has undergone extensive clinical trials in Indian kala-azar patients. Being an aminoglycoside, acquired resistance is likely to occur when used as a monotherapy. To encounter the problem of treatment failure in kala-azar and to reduce length of therapy, combination of at least two effective antileishmanial agents is a desirable option. In India sodium stibogluconate (SSG) in standard dose has been combined with other antileishmanial agents including paromomycin without encouraging result. Infection with Leishmania donovani depresses cell-mediated immunity. Immunological balance is tilted in favour of Th2 suppressive cytokines over Th1 producing protective cytokines. Interferon gamma (IFN-gamma) has been used in combination with SbV in Indian kala-azar patients with unexpectedly discouraging results. Combination of two most potent leishmanicidal drugs amphotericin B and miltefosine which are not dependent on host immune system, may shorten the course of therapy besides encountering unresponsiveness. A combination therapy should be preferred when treating kala-azar associated with HIV/AIDS. Immunotherapy with exogenous Th1 stimulating cytokines or use of antileishmanial vaccine in combination with a potent chemotherapeutic agent is a future option.

Amphotericin B↗
PubMed1979

[Aminoglycoside-3'-phosphotransferase from Actinomyces fradiae. Its isolation, purification and properties].

Aminoglycoside phosphotransferase was isolated from the mycelium of Act. fradiae, the neomycin-producing organism, with paromomycin, neomycin and to a less extent ribostamycin being substrates of aminoglycoside-phosphotransferase. It was purified to homogenous state. The maximum activity of the enzyme preparations was observed at pH 7.7--7.8;KM for neomycin and paromomycin was about 20 micron and KM for ATP was 150 micron. Mg2+ ions were necessary for the enzyme activity. None of the divalent cations tested could replace the magnesium ions in the reaction of phosphorylation catalyzed by the enzyme. High sensitivity to the ionic strength of the buffer was characteristic of the enzyme. It lost about 80 per cent of the initial activity at a concentration of KC1 equal to 1.0 M. The molecular mass of the enzyme from the mycelium of Act. fradiae was determined by the method of gel-filtration through sefadex G-100. It was about 22,000. High stability was characteristic of the enzyme. The fingings indicate that aminoglycoside phosphotransferase from Act. fradiae differs from the described aminoglycoside-3'-phosphotransferases isolated from antibiotic resistant bacteria.

Aminoglycosides↗
PubMed1984

The influence of aminoglycoside antibiotics on the in vitro function of rat liver ribosomes.

There are few studies of the influence of aminoglycoside antibiotics on the ribosomes of higher eukaryotic organisms. To this end, cytoplasmic ribosomes were prepared from rat liver. In vitro, poly(U)-directed ribosome protein synthesis was studied in the presence and absence of selected aminoglycosides. Misreading of poly(U) was also assessed. Consistent with earlier studies using different sources of ribosomes, paromomycin inhibited cell-free protein synthesis and caused poly(U) misreading. In contrast to the findings of other studies in cell-free ribosomes of eukaryotic organisms, netilmicin, tobramycin, and neomycin were most active in inhibiting protein synthesis, and gentamicin C2 and neomycin caused appreciable misreading. Thus the previous suggestion that a paromamine fragment (found in paromomycin) might be a structural requirement for in vitro inhibition of protein synthesis and misreading is not substantiated by the results in rat liver ribosomes. Commercial gentamicin C is a mixture of gentamicins C1, C1a, and C2. Despite nearly identical chemical structures, the three constituents displayed greatly different propensities for inducing poly(U) misreading. C2 was the most active, followed by C1a. In summary, selected aminoglycoside antibiotics caused inhibition and mistranslation of poly(U) messenger in an in vitro ribosome system prepared from rat liver. These effects were not limited to paromamine-containing aminoglycoside antibiotics. Gentamicin C2 caused much more poly(U) misreading than the other two constituents of the gentamicin C complex.

Aminoglycosides↗
PubMed1976

[Resistance to beta-lactam antibiotics and aminoglycosides in gram negative bacteria. 2. Mechanism of resistance (author's transl)].

In a preceding paper the genetics of resistance of 2 representative strains exhibiting resistance to beta-lactam antibiotics (ampicillin, catbenicillin, cephalothin) to aminoglycosides (kanamycin, neomycin, paromomycin, gentamycin, sisomycin, tobramycin, streptomycin, spectinomycin) and further antimicrobials (tetracycline, chloramphenicol, suphonamides) were described. This paper reports about the mechanism of resistance to beta-lactam antibiotics and aminoglycosides in these strains. Enzymatic extracts from K. pneumoniae 1 and Serratia marcescens 2 were produced by the osmotic shock procedure. Incubation of these extracts with aminoglycoside antibiotics, to which the strains are resistant, and ATP resulted in the total inactivation of the antimicrobials, as measured with a Bacillus subtilis assay. Analysis of this inactivation with the radioactive methods of Davies and his colleagues revealed that the kanamycins, neomycins, paromomycin and gentamycin A were phosphorylated. Because butirosin was not a substrate for the phosphorylating enzyme, it was concluded that the strain produced the neomycin/kanamycin phosphototransferase I. Furthermore, it was found that streptomycin and spectinomycin were adenylylated by the enzymatic extracts as well as gentamycin C1a, C1, C2, A, tobramycin, sisomycin and the kanamycins. This substrate profile indicated the presence of two adenylylating enzymes: streptomycin/spectinomycin-adenylyl-transferase and gentamycin-adenylyltransferase. After transfer of multiple drug resistance by conjugation from both strains into C. coli K-12, sonified extracts were prepared and examined for enzymatic activity splitting beta-lactam antibiotics. The relative rates of inactivation of benzylpenicillin, ampicillin and cephaloridine as well as the inhibitory effect of cloxacillin, but not of p-chloro-mercuri-benzoate on the inactivation of cephaloridine indicated that both strains produced a class III/type a (TEM type) beta-lactamase. It is discussed that the increasing frequency of gram-negative organisms form the university hospital with identical resistant phenotypes as the strains examined is the result of the spread of an R-factor among the hospital bacterial flora.

Aminoglycosides↗
PubMed1975

Modification and inheritance of pleiotropic cross resistance and collateral sensitivity in Saccharomyces cerevisiae.

A meiotic segregant (oliPR1) was isolated with a phenotype of multiple cross resistance and collateral sensitivity. Strain oliPR1 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, triphenylmethlphosphonium 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 oliPR1 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 oliPR1. Anaerobic pretreatment, 37degrees and 0.5 MKC1 were observed to reduce the growth of oliPR1 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 oliPR1 (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 afteranaerobic pretreatment revealed that anaerbiosis sensitized respiratory adaptation of the revertant to neomycin. It is proposed that oliPR1 is a mutation resulting in the alteration of plasma membrane permeability to many diverse inhibitors.

Antimycin A↗
PubMed1998

Cutaneous leishmaniasis due to Leishmania infantum. Case reports and literature review.

BACKGROUND: Leishmania infantum recently has been identified as a possible agent of cutaneous leishmaniasis (CL). This species has been isolated from cutaneous lesions of patients from the Mediterranean Basin. However, little is known about the clinical, biological, or therapeutic features of this newly recognized CL. OBSERVATIONS: Six patients aged 9 months to 85 years in southeastern France were found to have autochthonous leishmaniasis. Parasitological identification showed that the agent was L infantum, zymodemes Montpellier-1 for 2 patients and Montpellier-24 for 1 patient. Five patients who underwent testing with a Western blot assay were found to have antibodies against 4 antigens with molecular masses of 18, 21, 23, and 31 kd. Five patients were successfully treated with local injections of N-methylglucamine, and 1 patient was successfully treated with topical paromomycin sulfate. No patient had visceral disease at diagnosis or after follow-up. CONCLUSIONS: Recent data provide increasing evidence that L infantum is an important agent of CL. In southwestern Europe, this species is the only agent that has long been identified from autochthonous CL. Leishmania infantum should be considered an agent of CL in areas in which visceral leishmaniasis is endemic. Western blot assay could be a useful test for the diagnosis, but precise parasitological identification is important to having a better knowledge of the disease. The relationships between CL and the visceral disease have to be explored.

Administration, Cutaneous↗
PubMedDate not supplied

Protection by antibiotics against experimental focal cholangitis produced in mice by a schistosomicidal isothiocyanate.

Oral administration to mice of high doses of 4-isothiocyano-4'nitrodiphenylamine (amoscanate), a potent antischistosomal drug, produced focal necrotizing lesions of the large intrahepatic and extrahepatic bile ducts and the gallbladder. Coadministration of erythromycin and, to a somewhat lesser degree, of paromomycin, markedly reduced the effects of amoscanate on the biliary tract. These results suggest that amoscanate may be converted to a cholangiotoxic product by one or several constituents of the enteric bacterial flora. Since erythromycin does not affect the antischistosomal activity of amoscanate, coadministration of an antibacterial agent can reduce toxic effects of a drug while full chemotherapeutic activity is maintained. The possibility of toxic effects of metabolites of xenobiotics produced by intestinal bacteria deserves attention and the experimental production of focal intrahepatic and extrahepatic cholangitis by such drug metabolites suggests a possible mechanism in human bile diseases.

1-Naphthylisothiocyanate↗
PubMed1995

The properties of the multicopy suppressor of the ogd1 mutation in yeast.

The 8.1 kb chromosomal fragment partially suppressing the ogd1 mutation in Saccharomyces cerevisiae has been cloned. The molecular analysis revealed that its suppressor gene codes for a natural glutamine tRNA(CAG) and maps on chromosome XIII in the upstream region of the URA10 gene. The multicopy plasmids containing this tRNA gene also suppressed the standard trp1-1 amber mutation and conferred the sensitivity of yeast cells to paromomycin and increased temperature.

Chromosome Mapping↗
PubMed1993

MSS1, a nuclear-encoded mitochondrial GTPase involved in the expression of COX1 subunit of cytochrome c oxidase.

Mutations in the MSS1 gene render the yeast cells respiratory deficient only in the presence of the PR454 mutation (paromomycin resistance) in the mitochondrial 15 S ribosomal RNA gene. The MSS1 gene product works in association with the small subunit of mitoribosomes and seems to play some part in mitochondrial translation. The block in the splicing of introns of cytochrome c oxidase subunit 1 could result from a specific impeding of the translation of maturases. Comparison of the MSS1 putative protein with data libraries revealed that it contains, in its second half, the consensus sequences characteristic of GTP binding proteins and is very homologous to the bacterial "genes 50K".

Base Sequence↗
PubMed1999

Effect of mutations in the A site of 16 S rRNA on aminoglycoside antibiotic-ribosome interaction.

Decoding of genetic information occurs upon interaction of an mRNA codon-tRNA anticodon complex with the small subunit of the ribosome. The ribosomal decoding region is associated with highly conserved sequences near the 3' end of 16 S rRNA. The decoding process is perturbed by the aminoglycoside antibiotics, which also interact with this region of rRNA. Mutations of certain nucleotides in rRNA reduce aminoglycoside binding affinity, as previously demonstrated using a model RNA oligonucleotide system. Here, predictions from the oligonucleotide system were tested in the ribosome by mutation of universally conserved nucleotides at 1406 to 1408 and 1494 to 1495 in the decoding region of plasmid-encoded bacterial 16 S rRNA. Phenotypic changes range from the benign effect of U1406-->A or A1408-->G substitutions, to the highly deleterious 1406G and 1495 mutations that assemble into 30 S subunits but are defective in forming functional ribosomes. Changes in the local conformation of the decoding region caused by these mutations were identified by chemical probing of isolated 30 S subunits. Ribosomes containing 16 S rRNA with mutations at positions 1408, 1407+1494, or 1495 had reduced affinity for the aminoglycoside paromomycin, whereas no discernible reduction in affinity was observed with 1406 mutant ribosomes. These data are consistent with prior NMR structural determination of aminoglycoside interaction with the decoding region, and further our understanding of how aminoglycoside resistance can be conferred.

Anti-Bacterial Agents↗
PubMed1978

Physical mapping of genes on yeast mitochondrial DNA: localization of antibiotic resistance loci, and rRNA and tRNA genes.

We have physically mapped the loci conferring resistance to antibiotics that inhibit mitochondrial protein synthesis (erythromycin, chloramphenicol and paromomycin) or respiration (oligomycin I and II), as well as the 21s and 14s rRNA and tRNA genes on the restriction map of the mitochondrial genome of the yeast Saccharomyces cerevisiae. The mitochondrial genes were localized by hybridization of labeled RNA probes to restriction fragments of grande (strain MH41-7B) mitochondrial DNA (mtDNA) generated by endonucleases EcoRI, HpaI, BamHI, HindIII, SalI, PstI and HhaI. We have derived the HhaI restriction fragment map of MH41-7B mit DNA, to be added to our previously reported maps for the six other endonucleases. The antibiotic resistance loci (antR) were mapped by hybridization of 3H-cRNA transcribed from single marker petite mtDNA's of low kinetic complexity to grande restriction fragments. We have chosen the single Sal I site as the origin of the circular physical map and have positioned the antibiotic loci as follows: C (99.5-1.Ou)--P (27-36.Ou)--OII (58.3-62u--OI (80-84u)--E (94.4-98.4u). The 21s rRNA is localized at 94.4-99.2u, and the 14s rRNA is positioned between 36.2-39.8u. The two rRNA species are separated by 36% of the genome. Total mitochondrial tRNA labeled with 125I hybridized primarily to two regions of the genome, at 99.5-11.5u and 34-44u. A third region of hybridization was occasionally detected at 70--76u, which probably corresponds to seryl and glutamyl tRNA genes, previously located to this region by petite deletion mapping.

Chloramphenicol↗
PubMed1976

Deletion mapping of mitochondrial transfer RNA genes in Saccharomyces cerevisiae by means of cytoplasmic petite mutants.

Mitochondrial transfer RNA genes have been ordered relative to the position of five mitochondrial drug resistance markers, namely, chloramphenicol (C),1 erythromycin (E), oligomycin I and II (OI, OII), and paromomycin (P). Forty-six petite yeast clones that were genetically characterized with respect to these markers were used for a study of these relationships. Different regions of the mitochondrial genome are deleted in these individual mutants, resulting in variable loss of genetic markers. Mitochondrial DNA was isolated from each mutant strain and hybridized with eleven individual mitochondrial transfer RNAs. The following results were obtained: i) Of the seven petite clones that retained C, E, and P resistance markers (but not O1 or O11), four carried all eleven transfer RNA genes examined; the other three clones lost several transfer RNA genes, probably by secondary internal deletion; ii) Prolyl and valyl transfer RNA genes were located close to the P marker, whereas the histidyl transfer RNA gene was close to the C marker; iii) Except for a glutamyl transfer RNA gene that was loosely associated with the O1 region, no other transfer RNA genes were found in petite clones retaining only the O1 and/or the OII markers; and iv) Two distinct mitochondrial genes were found for glutamyl transfer RNA, they were not homologous in DNA sequence and were located at two separate loci. The data indicate that the petite mitochondrial genome is the result of a primary deletion followed by successive additional deletions. Thus an unequivocal gene arrangement cannot be readily established by deletion mapping with petite mutants alone. Nevertheless, we have derived a tentative circular map of the yeast mitochondrial genome from the data; the map indicates that all but one of the transfer RNA genes are found between the C and P markers without forming a tight cluster. The following arrangement is suggested: -P-pro-val-ile-(phe, ala, tyr, asp)-glu2- (lys-leu)-his-C-E-O1-glu1-OII-P-.

Chloramphenicol↗
PubMed1989

Two new loci that give rise to dominant omnipotent suppressors in Saccharomyces cerevisiae.

Ten dominant omnipotent suppressors of Saccharomyces cerevisiae, which were previously shown to be different from SUP46, have been examined. Nine are mapped in a region between lys5 and cyh2 on the left arm of chromosome VII. These suppressors, like SUP46, manifest sensitivity to increased temperature and the antibiotics paromomycin and hygromycin B. In addition, they have an identical action spectrum. These results strongly suggest that they are allelic to each other and they are designated SUP138. The tenth is mapped to a position between his1 and arg6 on the right arm of chromosome V. This suppressor, named SUP139, does not manifest temperature sensitivity nor antibiotic sensitivity. SUP139 and SUP138, which are clearly distinguished by means of action spectrum, act on much fewer nonsense mutations than SUP46. It is now clear that dominant omnipotent suppressors arising at a single locus are homogeneous and that their efficiency is locus-dependent. The order of efficiency is SUP46 greater than SUP138 greater than SUP139.

Alleles↗
PubMed1976

Some physiological alteration associated with pleiotropic cross resistance and collateral sensitivity in Saccharomyces cerevisiae.

A mutant strain (2-20) isolated by growth on medium containing oligomycin and cycloheximide was also found to be cross resistant to antimyicn, cerulenin, chloramphenicol, tetracycline, triethyltin and triphenylmethylphosphonium bromide, but collaterally sensitive to dequalinium chloride, gentamycin, neomycin, paromomycin and thiolutin. Growth of 2-20, compared to the parental strain and 2 complete revertants, under a variety of environmental conditions revealed that strain 2-20 had an enhanced sensitivity to increased osmolality, elevated pH, and high temperature; in addition, strain 2-20 was unable to polymerize aminoimidazole ribotide at 37 degrees C as shown by the failure to develop a red colony in the presence of ade 2. Four complex solid media (glucose--KCI, galactose, ethanol, ethanol--KCI, Table 1) unable to sustain the growth of strain 2-20 were arbitrarily chosen to monitor cellular growth under different physiological conditions. Tetrad analysis indicated that the complex phenotype (cross resistance, collateral sensitivity, inablity to polymerize aminoimidazole ribotide, absence of growth under adverse physiological conditions) was inherited by an allele of a locus previously shown to result in a permeability barrier of the plasma membrane to chloramphenicol. 582 of 640 subclones used to isolate revertants of 2-20, under four different physiological conditions, were observed to produce a complete revertant of the complex phenotype. It is proposed that the pleiotropic phenotype could result from an alteration of the plasma membrane and mitochondrial inner membrane by a single nuclear gene mutation.

Alleles↗