MOLECULAR ORGANIZATION OF THE MAL6 LOCUS OF SACCHAROMYCES CARLSBERGENSIS.
Item
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Title
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MOLECULAR ORGANIZATION OF THE MAL6 LOCUS OF SACCHAROMYCES CARLSBERGENSIS.
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Identifier
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AAI8708281
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identifier
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8708281
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Creator
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DUBIN, ROBERT ALLEN.
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Contributor
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Corinne A. Michels
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Genetics
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Abstract
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The MAL loci of Saccharomyces are a polymeric series of five unlinked, dominant loci, any one of which confers upon yeast the ability to ferment maltose. Maltose fermenting strains synthesize two maltose fermentative enzymes, maltase and maltose permease. In most maltose fermenting strains, synthesis of maltase and maltose permease is induced by maltose, however in certain mutants, expression of these enzymes is unregulated and constitutive.;Previous genetic evidence demonstrated that the cloned MAL6 locus was a complex locus composed to three genes: MAL61, MAL62, and MAL63. The MAL61 and MAL62 genes are responsible for the synthesis of maltose inducible transcripts while the MAL63 gene transcripts are constitutively expressed. Using in vitro mutagenesis and gene transplacement, we have selectively mutated these genes at the genomic MAL6 locus in an inducible strain and have demonstrated that all three genes are required for maltose fermentation. Further characterization of these mutants has established the functions of these three gene products. The MAL61 gene may encode the maltose permease. The MAL62 gene encodes maltase. The MAL63 gene encodes a trans-acting, positive regulatory function that is required for maltose regulated induction of maltase and maltose permease and their respective transcripts.;The mutation responsible for constitutive expression of maltase and maltose permease in MAL6-C constitutive mutants is linked to the MAL6 locus. We have demonstrated that the positive regulatory gene MAL63 is dispensible for maltose fermentation in constitutive strains and plays no role in constitutive expression of the maltose fermentative enzymes or their respective transcripts. Instead, constitutivity is dependent upon a fourth MAL6-linked gene, MAL64. MAL64 is located 3.5 kilobase pairs to the left of MAL63 and shows at least partial homology to the MAL63 gene. The MAL64-C allele present in MAL6-linked constitutive strains encodes a trans-acting, positive regulatory function that is required for the constitutive expression of the maltose fermentative enzymes and their respective MAL61 and MAL62 transcripts. In contrast, the wild type MAL64 gene present in inducible MAL6 strains is dispensible and plays no apparent role in maltose regulated, inducible fermentation.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biology
