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L Frontali

Publications and source records attributed to L Frontali.

At least 55 records · Page 3Linked to original sources
PubMed1984

Expression of the clustered mitochondrial tRNA genes in Saccharomyces cerevisiae: transcription and processing of transcripts.

The transcripts of a cluster of eight tRNA genes localized in the Cap-oxiI region of the mitochondrial genome of Saccharomyces cerevisiae were investigated by hybridization of gene-specific probes on Northern blots of mitochondrial RNA and by S1 mapping of the 5' termini of the transcripts. Two rho- mutants that lack mature tRNA species and accumulate precursors have been used to detect transcripts that are not detectable in wild-type (w.t.) mitochondria. The results have shown the existence of polygenic transcripts carrying at least 5-7 tRNA sequences, both in w.t. and in rho- strains. The existence of several alternative processing pathways, which involve cleavage at the 3' and 5' ends of the tRNA sequences and in the long intergenic regions (possibly at GC clusters), is suggested. Cleavage at the 5' ends of tRNA sequences is defective in the mutant strains. The transcripts of the genes for tRNAThrACN and tRNACys (the tRNA genes immediately downstream from the 21S rRNA gene) have been analyzed; the possibility that these species represent primary transcripts is considered, and potential sites for initiation of transcription of the clustered tRNA genes are discussed.

Base Sequence↗
PubMed1984

Molecular characterization of a plasmid from Pseudomonas fluorescens involved in styrene degradation.

In this paper evidence is given that in a strain of Pseudomonas fluorescens able to grow on styrene as the sole carbon source, the degradation pathway of styrene is inducible and plasmid dependent. The plasmid, which we have called pEG is self-transmissible between Pseudomonas strains and has a size of 37 kb. A restriction map has been constructed and evidence for an inducible transcription of two separate regions of the plasmid has been obtained.

Chromosome Mapping↗
PubMed1983

Mitochondrial translation products during release from glucose repression in Saccharomyces cerevisiae.

Mitochondrial protein synthesis was studied during release from glucose repression in Saccharomyces cerevisiae cells bearing different mitochondrial genomes. The increase in the rate of the synthesis of mitochondrial translation products was analyzed during respiratory induction. Different kinetic patterns were found for strains having a different structure of mitochondrial mosaic genes, even when the nuclear background was the same. A very limited response of the synthesis of the var1 ribosomal protein to inducing conditions was observed.

Cycloheximide↗
PubMed1983

Role of nuclear genes in expression of a mitochondrial tRNA gene in Saccharomyces cerevisiae.

In yeast mitochondria, most of the isoaccepting species of tyrosyl tRNA are coded by a mitochondrial gene, tyrA. A particular isoaccepting species is coded by a second mitochondrial gene, tyrB. This gene is not expressed in certain strains of yeast which show no deficient phenotype. Genetic crosses between strains expressing or not expressing the tyrB gene demonstrate that expression is controlled by specific nuclear genes and that a mutation of the tyrA gene can be bypassed when the tyrB gene is operative.

Cell Nucleus↗
PubMed1982

Transcripts of mitochondrial tRNA genes in Saccharomyces cerevisiae.

The transcription of a group of tRNA genes from the large tRNA gene cluster of mitochondrial DNA from Saccharomyces cerevisiae has been investigated by hybridization with DNA probes carrying tRNA coding sequences and small portions of the A + T rich intergenic regions. Results have shown that in some rho- mutants (DS502, F11) mature tRNA was absent, but a few transcripts could be detected. Some high molecular weight species actually hybridized with DNA probes carrying different tRNA coding sequences. Low molecular weight transcripts (100-150 nucleotides, carrying one tRNA sequence) were also present in these mutants. A high molecular weight transcript was also observed in the wild type, though in much more limited amount. The low molecular weight transcripts were analysed by the S1 mapping technique and found to include both a tRNA sequence and the upstream 5' flanking region extending as far as the 3' end of the preceding tRNA gene. The results suggest the existence of a common transcript bearing several tRNA sequences and indicate a possible mechanism of processing, which might be defective in mutants.

Base Sequence↗
PubMed1979

Two isoaccepting seryl tRNAs coded by separate mitochondrial genes in yeast.

In S. cerevisiae four isoacceptor mitochondrial tRNAs for serine have been separated by reversed phase chromatography. At least two of these species are products of different genes. In this work the deletion mapping technique has been used to locate two genes for tRNAser. The gene for tRNAser previously localized in the oli I region of the mitochondrial genome has been found to code for tRNAser2, and another gene coding for tRNAser1 has been detected in the region where most of other tRNA genes are found. Results of fine mapping experiments allowed to localize this gene in the proximity of the gene for tRNAarg.

Chromatography↗
PubMed1979

Mitochondrial protein-synthesizing machinery in Saccharomyces cerevisiae grown in different metabolic conditions. Variability of seryl-tRNA and alanyl-tRNA isoacceptor patterns.

1. The isoacceptor patterns of mitochondrial seryl and alanyl-tRNAs from Saccharomyces cerevisiae grown under different conditions and committed to fermentative or respiratory metabolism have been studied by reversed-phase chromatography. 2. An extensive variability of the chromatographic patterns of the four isoacceptors for serine and of the three isoacceptors for alanine has been observed as a function of carbon source and stage of growth, but the main differences were observed in the different stages of growth on glucose. 3. In order to distinguish the effects due to stage of growth from those due to relief from glucose repression, the isoacceptor patterns of mitochondrial tRNA were compared in repressed and derepressed resting cells; results show that some of the mitochondrial species are almost undetectable in resting repressed cells, but are the major ones after recovery of respiration. 4. Two of the serine isoacceptors (species 1 and 2), one of which is absent or not acylable in repressed resting cells, are different gene products.

Alanine↗
PubMed1977

Dependence of cytoplasmic on mitochondrial protein synthesis in K. Lactis CBS 2360. I. Biochemical analysis.

In the "petite negative" yeast Kluyveromyces lactis (strain CBS 2360) growth is inhibited by the same Erythromycin concentrations on fermentable and non-fermentable carbon sources. The minimal inhibitory concentrations of Erythromycin does not affect respiration, but completely inhibits total aminoacid incorporation by the cells in conditions in which permeability effects can be ruled out. The effect of the antibiotic on the "in vitro" protein synthesis by cytoplasmic and mitochondrial systems shows that inhibition is effective only at the mitochondrial level. Results suggest that the inhibition of growth and of total protein synthesis is a consequence of the inhibition of mitochondrial protein synthesis.

Cell-Free System↗
PubMed1975

Heterogeneity of mitochondrial DNA from Saccharomyces cerevisiae and genetic information for tRNA.

Mitochondrial DNA from wild-type Saccharomyces cerevisiae and from an "extreme" petite mutant were analyzed by hybridization of several tRNAs on DNA fragments of different buoyant density, obtained by sonication and fractionation on a CsCl gradient. The hybridization patterns show that the genes for tRNAser, tRNAphe, tRNAhis, tRNAval, tRNAileu are present on wild-type mitochondrial DNA, while only genes for tRNAser and tRNAhis are present on petite mitochondrial DNA; moreover the hybridization patterns indicate that these genes are not clustered and suggest that more than one gene might exist for tRNAser and tRNAhis.

Centrifugation, Density Gradient↗