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  • 1
    ISSN: 1432-0983
    Keywords: Key words Zinc-finger protein ; Nuclear localization ; Immuno electron microscopy ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In previous studies the AZF1 gene has been identified as a second high-copy number suppressor for a special mutant of the gene for the mitochondrial core enzyme of RNA polymerase. The first high-copy number suppressor of this mutant turned out to be the specificity factor MTF1 for mitochondrial transcription. Up to now, the influence of AZF1 on mitochondrial transcription, its precise localization in the cell and the regulation of its expression has not been determined. The putative protein contains a long stretch of poly-asparagine amino acids and a typical zinc-finger domain for DNA binding. These characteristic structural features were used to create the abbreviation AZF1 (Asparagine-rich Zinc Finger protein). An initial computer analysis of the sequence gave no conclusive results for the presence of a mitochondrial import sequence or a typical nuclear-targeting sequence. A recent more-detailed analysis identified a possible nuclear localization signal in the middle of the protein. Disruption of the gene shows no effect on plates with glucose-rich medium or glycerol. In this report a specific polyclonal antibody against Azf1p was prepared and used in cell-fractionation experiments and in electron-microscopic studies. Both of these clearly demonstrate that the AZF1 protein is localized exclusively in the nucleus of the yeast cell. Northern analysis for the expression of the AZF1 messenger RNA under different growth conditions was therefore performed to obtain new insights into the regulation of this gene. Together with the respective protein-expression analysis these data demonstrate that Azf1p is preferentially synthezised in higher amounts under non-fermentable growth conditions. Over-expression of Azf1p in the yeast cell does not influence the expression level of the mitochondrial transcription factor Mtf1p, indicating that the influence of Azf1p on the suppression of the special mitochondrial RNA polymerase mutant is an indirect one. Subcellular investigation of the deletion mutant by electron microscopy identifies specific ultrastructural cell-division defects in comparison to the wild-type.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0983
    Keywords: β-isopropylmalate dehydrogenase ; Allelic variation ; Genome organisation ; Candida maltosa ; Silent genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three different alleles of the β-isopropylmalate dehydrogenase gene were cloned and sequenced from a leucine auxotrophic mutant, G587, of Candida maltosa. The cloning of functionally-intact wild-type genes from this mutant strain suggests the presence of silent gene copies. An interallelic-divergence comparison has provided evidence for new regulatory mechanisms. Sequence data and karyotype analysis argue for a highly-aneuploid genome of C. maltosa. An interpretation for the spontaneous auxotrophy-prototrophy-auxotrophy sequence of mutations in C. maltosa is suggested.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 6 (1982), S. 163-165 
    ISSN: 1432-0983
    Keywords: Hybridization ; Polyethylene glycol ; Nuclear transfer ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Viable hybrids of Saccharomyces cerevisiae were obtained by transfer of isolated diploid nuclei into haploid protoplasts using a polyethylene glycol (PEG) fusion procedure.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1617-4623
    Keywords: Pathway ; Gene cloning ; Karyotyping ; Mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The four enzymatic steps in the conversion of α-ketoisovaleriate to leucine were examined in the wild type and in 13 leucine auxotrophic strains of Candida maltosa. The genetic lesions in the auxotrophs, involve at least five different loci and are correlated with three enzymatic steps. This was confirmed by gene cloning, protoplast fusion, and enzyme assays. The pathway for leucine biosynthesis in C. maltosa shows general similarity to that of other lower eukaryotes but there are individual differences in the numbers of genes responsible for single enzymatic steps. A disomic state of the chromosomes carrying genes coding for α-isopropylmalate synthase and β-isopropyl-malate dehydrogenase was elucidated.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1617-4623
    Keywords: Imperfect yeasts ; Genome plasticity ; Adenine biosynthesis ; Mitotic recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The imperfect yeast Candida maltosa has an ill-defined genetic constitution; it is nominally diploid, but probably highly aneuploid, in nature. We report on polymorphisms specifically affecting those chromosomes which bear the cm-ADE1 gene. This gene encodes phosphoribosylaminoimidazole-succinocarboxamide synthetase, an enzyme in the adenine biosynthetic pathway. By electrophoretic karyotype analysis, three differently sized chromosomes were demonstrated to carry cm-ADE; the size (but not the number) of these chromosomes was also found to vary, both between strains and during the mitotic growth of a single strain. Four different alleles of cm-ADE1 have been cloned and sequenced from one prototrophic strain. DNA sequence divergence between these different alleles is as high as 8%, with the greatest divergence being found in the upstream region. Mitotic recombination events that led to changes in the karyotype were followed by using cm-ADE1 DNA as an hybridization probe. A recombination hot-spot in the neighbourhood of the gene appears to be responsible for the instability of the chromosomes on which it resides.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Protoplast fusions between strains of identical and of opposite mating type were performed. Sexual crosses and protoplast fusions inRhodosporidium toruloides led to different hybrid types. Sexual crosses gave rise exclusively to a dikaryotic mycelium. In protoplast fusions between strains of identical mating type (A ora), monokaryotic yeast-like hybrids which sustained the parental mating type were obtained. In protoplast fusions between strains of opposite mating type, the majority of the hybrids belonged to theMyc + type, i.e., the hybrids grew like yeasts, able to switch over spontaneously to mycelial growth. In addition to theMyc + types, up to 10% real yeast hybrids and less than 5% dikaryotic mycelia were obtained. Obviously the cell type inR. toruloides is under the control of the mating type alleles.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 14 (1998), S. 287-295 
    ISSN: 0749-503X
    Keywords: Candida maltosa ; Candida albicans ; tRNA splicing gene ; silent genes ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The tRNA splicing gene SPL1-1 has been cloned and sequenced in Saccharomyces cerevisiae (Kolman and Soll, 1993). Sequence adjacent to the LEU2 gene in Candida maltosa showed some homology to the SPL1-1 gene of S. cerevisiae. This work describes the sequencing of the SPL1 tRNA splicing genes from C. maltosa and C. albicans and the analysis of these genes. Comparison of these sequences and the relationship observed between the LEU2 and SPL1 genes in these yeasts suggests that there may be some synteny amongst various species of yeasts. The coding region of the C. maltosa SPL1 region described in this work differs from previously described partial sequences in that it is a complete uninterrupted open reading frame. Two strains of C. maltosa were each shown to contain different alleles, one uninterrupted open reading frame and one disrupted open reading frame. The sequences have been deposited in the GenBank/EMBL data libraries under Accession Numbers X72940, AF000115, AF000116, AF000117, AF000118, AF000119 and AF000120. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0749-503X
    Keywords: Candida maltosa ; electroporation ; transformation ; plasmid vectors ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Conditions for efficient and quick transformation by electroporation were developed in Candida maltosa. To investigate the efficiency of transformation with integrative as well as with autonomously replicating plasmids, a series of vectors was constructed for homologous transformation of the species. Transformants were obtained with different plasmids as covalently closed circular molecules and as linearized DNA. The influence of recipient strain and plasmid type as well as of cell number and parameters of the supplied electrical pulse on the transformation efficiency have been investigated. A maximum of 7000 transformants per 100ng of plasmid DNA was reached. The efficiency of transformation was compared with that of the LiCl method.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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